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000
FXHW60 PHFO 210156
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
356 PM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT SOME SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS WILL BE MOST ACTIVE DURING
THE NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW DEVELOPING
NORTHWEST OF THE ISLANDS WILL WEAKEN WINDS AND VEER THEM OUT OF
THE SOUTHEAST.

&&

.DISCUSSION...
VISIBLE SATELLITE AND RADAR SHOW SCATTERED PASSING TRADE WIND SHOWERS
ACROSS HAWAII THIS AFTERNOON. TRADE WINDS WILL CONTINUE TO BE
STRONG...DRIVEN BY AN EASTWARD TRAVELING HIGH PRESSURE SYSTEM
NORTH OF THE STATE. THE BREEZY CONDITIONS ARE THE RESULT OF THE
PRESSURE DIFFERENCE BETWEEN THE HIGH AND EQUATORIAL LOW PRESSURE
SOUTH OF THE AREA. AFTERNOON SOUNDINGS SHOW A STABLE ATMOSPHERE
ALOFT WITH SUBSIDENCE INVERSIONS AT AROUND 8000 FEET WITH PRECIPATBLE
WATER VALUES AT BOTH LOCATIONS ARE BELOW NORMAL.

ISLAND TOPOGRAPHY...COUPLED WITH THE STRONG TRADE WINDS...IS
RESULTING IN SOME PASSING SHOWERS ACROSS HAWAII LATE THIS
AFTERNOON. WINDWARD AREAS ARE SEEING MOST OF THE SHOWERS...BUT
WINDS ARE CARRYING OCCASIONAL CLOUDS AND SHOWERS ACROSS TO THE
LEEWARD AREAS AS WELL. EXPECT THIS PATTERN TO CONTINUE AT LEAST
THROUGH TUESDAY NIGHT...WITH MORE SHOWERS DURING THE NIGHTTIME
HOURS. THE ATMOSPHERE WILL REMAIN STABLE...THUS SHOWERS WILL BE
LIGHT AND FAST MOVING.

BOTH GFS AND ECMWF SHOW AN UPPER / SURFACE LOW DEVELOPING NORTHWEST OF
HAWAII ON TUESDAY NIGHT AND WEDNESDAY. THIS SYSTEM IS EXPECTED TO
LINGER TO THE NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A
SIGNIFICANT FRONT / CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD
FROM THE LOW. MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY
AND MOISTURE AHEAD OF THE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN.

MODELS SHOWS THIS FEATURE LINGERING WEST OF HAWAII FROM WEDNESDAY INTO
THE WEEKEND...AND COULD PRODUCE SOME SHOWERS OVER THE WESTERN PORTION
OF THE STATE LATER THIS WEEK. THE LOW IS EXPECTED TO BE CLOSE AND
STRONG ENOUGH TO SHIFT WINDS OUT OF THE SOUTHEAST FROM WEDNESDAY
THROUGH THE WEEKEND TO BRING VOG AND HUMID CONDTIONS OVER THE
STATE. CLOUDS AND SHOWERS MOVING IN WITH THE SOUTHEAST FLOW WILL
FOCUS OVER WINDWARD AND SOUTHEASTERN FACING SLOPES...AND SHOULD BE
A LITTLE BIT WETTER THAN TODAY AND TUESDAY. PLUME CLOUDS AND
SHOWER BANDS MAY SET UP UNDER THESE CONDITIONS. IT IS NOT LIKELY
TO BE UNSTABLE ENOUGH TO PRODUCE HEAVY RAIN...BUT SHOWERS COULD
ANCHOR OVER THE WINDWARD AND SOUTHEAST FACING SLOPES BRINGING MORE
PERSISTENT RAIN.

STILL TOO EARLY TO CALL FOR WEATHER THIS WEEKEND AS THE SYSTEM
WILL REMAIN JUST WEST OF THE STATE WITH GFS AND ECMWF DIVERGING
SOLUTIONS. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER INCREASE IN
MOISTURE OVER NIIHAU AND KAUAI. THIS WILL LEAD TO A POSSIBLE MORE
WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE WEEKEND.


&&

.AVIATION...
STRONG SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SUSTAIN BREEZY
EASTERLY TRADE WINDS THROUGH TONIGHT. OCCASIONAL MVFR CIGS WILL
LIKELY IMPACT WINDWARD SECTIONS THROUGH MID MORNING TUESDAY.
ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AS THE HIGH WILL SHIFTS EAST TUESDAY THE WINDS ACROSS THE ISLANDS
WILL BECOME MORE SOUTHEASTERLY AND WEAKER...WITH THE BIG ISLAND
ACTING AS A SHIELD FOR THE OTHER ISLANDS. THUS THE LOW LEVEL
TURBULENCE AIRMET WILL NOT BE REQUIRED AT THAT POINT IN TIME.


&&

.MARINE...
STRONG WINDS WILL AFFECT ALL HAWAIIAN COASTAL WATERS THROUGH
TUESDAY. A GALE WARNING IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE
ALENUIHAHA CHANNEL...WITH SMALL CRAFT ADVISORIES /SCA/ IN EFFECT
FOR THE REST OF THE COASTAL WATERS. THE SCA WILL LIKELY CONTINUE
FOR ALL WATERS ON TUESDAY...AND BEYOND FOR SELECT ZONES.

WINDS ARE EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE
ISLANDS TUESDAY NIGHT. THE SOUTHEAST FLOW WILL CONTINUE THROUGH
THE REST OF THE WEEK INTO THE WEEKEND.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT AND MAY NEED TO BE EXTENDED IF WINDS ARE
SLOW TO WEAKEN.

A LONG PERIOD SOUTH SWELL WILL SLOWLY BUILD TODAY...AND PEAK AROUND
TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING
SHORES...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NORTHWEST SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI AND BIG ISLAND.

GALE WARNING UNTIL 6 AM HST TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR REST OF HAWAIIAN
COASTAL WATERS.


&&

$$

DISCUSSION/MARINE...FOSTER
AVAITION...FUJII





000
FXHW60 PHFO 210156
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
356 PM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT SOME SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS WILL BE MOST ACTIVE DURING
THE NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW DEVELOPING
NORTHWEST OF THE ISLANDS WILL WEAKEN WINDS AND VEER THEM OUT OF
THE SOUTHEAST.

&&

.DISCUSSION...
VISIBLE SATELLITE AND RADAR SHOW SCATTERED PASSING TRADE WIND SHOWERS
ACROSS HAWAII THIS AFTERNOON. TRADE WINDS WILL CONTINUE TO BE
STRONG...DRIVEN BY AN EASTWARD TRAVELING HIGH PRESSURE SYSTEM
NORTH OF THE STATE. THE BREEZY CONDITIONS ARE THE RESULT OF THE
PRESSURE DIFFERENCE BETWEEN THE HIGH AND EQUATORIAL LOW PRESSURE
SOUTH OF THE AREA. AFTERNOON SOUNDINGS SHOW A STABLE ATMOSPHERE
ALOFT WITH SUBSIDENCE INVERSIONS AT AROUND 8000 FEET WITH PRECIPATBLE
WATER VALUES AT BOTH LOCATIONS ARE BELOW NORMAL.

ISLAND TOPOGRAPHY...COUPLED WITH THE STRONG TRADE WINDS...IS
RESULTING IN SOME PASSING SHOWERS ACROSS HAWAII LATE THIS
AFTERNOON. WINDWARD AREAS ARE SEEING MOST OF THE SHOWERS...BUT
WINDS ARE CARRYING OCCASIONAL CLOUDS AND SHOWERS ACROSS TO THE
LEEWARD AREAS AS WELL. EXPECT THIS PATTERN TO CONTINUE AT LEAST
THROUGH TUESDAY NIGHT...WITH MORE SHOWERS DURING THE NIGHTTIME
HOURS. THE ATMOSPHERE WILL REMAIN STABLE...THUS SHOWERS WILL BE
LIGHT AND FAST MOVING.

BOTH GFS AND ECMWF SHOW AN UPPER / SURFACE LOW DEVELOPING NORTHWEST OF
HAWAII ON TUESDAY NIGHT AND WEDNESDAY. THIS SYSTEM IS EXPECTED TO
LINGER TO THE NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A
SIGNIFICANT FRONT / CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD
FROM THE LOW. MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY
AND MOISTURE AHEAD OF THE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN.

MODELS SHOWS THIS FEATURE LINGERING WEST OF HAWAII FROM WEDNESDAY INTO
THE WEEKEND...AND COULD PRODUCE SOME SHOWERS OVER THE WESTERN PORTION
OF THE STATE LATER THIS WEEK. THE LOW IS EXPECTED TO BE CLOSE AND
STRONG ENOUGH TO SHIFT WINDS OUT OF THE SOUTHEAST FROM WEDNESDAY
THROUGH THE WEEKEND TO BRING VOG AND HUMID CONDTIONS OVER THE
STATE. CLOUDS AND SHOWERS MOVING IN WITH THE SOUTHEAST FLOW WILL
FOCUS OVER WINDWARD AND SOUTHEASTERN FACING SLOPES...AND SHOULD BE
A LITTLE BIT WETTER THAN TODAY AND TUESDAY. PLUME CLOUDS AND
SHOWER BANDS MAY SET UP UNDER THESE CONDITIONS. IT IS NOT LIKELY
TO BE UNSTABLE ENOUGH TO PRODUCE HEAVY RAIN...BUT SHOWERS COULD
ANCHOR OVER THE WINDWARD AND SOUTHEAST FACING SLOPES BRINGING MORE
PERSISTENT RAIN.

STILL TOO EARLY TO CALL FOR WEATHER THIS WEEKEND AS THE SYSTEM
WILL REMAIN JUST WEST OF THE STATE WITH GFS AND ECMWF DIVERGING
SOLUTIONS. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER INCREASE IN
MOISTURE OVER NIIHAU AND KAUAI. THIS WILL LEAD TO A POSSIBLE MORE
WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE WEEKEND.


&&

.AVIATION...
STRONG SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SUSTAIN BREEZY
EASTERLY TRADE WINDS THROUGH TONIGHT. OCCASIONAL MVFR CIGS WILL
LIKELY IMPACT WINDWARD SECTIONS THROUGH MID MORNING TUESDAY.
ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AS THE HIGH WILL SHIFTS EAST TUESDAY THE WINDS ACROSS THE ISLANDS
WILL BECOME MORE SOUTHEASTERLY AND WEAKER...WITH THE BIG ISLAND
ACTING AS A SHIELD FOR THE OTHER ISLANDS. THUS THE LOW LEVEL
TURBULENCE AIRMET WILL NOT BE REQUIRED AT THAT POINT IN TIME.


&&

.MARINE...
STRONG WINDS WILL AFFECT ALL HAWAIIAN COASTAL WATERS THROUGH
TUESDAY. A GALE WARNING IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE
ALENUIHAHA CHANNEL...WITH SMALL CRAFT ADVISORIES /SCA/ IN EFFECT
FOR THE REST OF THE COASTAL WATERS. THE SCA WILL LIKELY CONTINUE
FOR ALL WATERS ON TUESDAY...AND BEYOND FOR SELECT ZONES.

WINDS ARE EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE
ISLANDS TUESDAY NIGHT. THE SOUTHEAST FLOW WILL CONTINUE THROUGH
THE REST OF THE WEEK INTO THE WEEKEND.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT AND MAY NEED TO BE EXTENDED IF WINDS ARE
SLOW TO WEAKEN.

A LONG PERIOD SOUTH SWELL WILL SLOWLY BUILD TODAY...AND PEAK AROUND
TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING
SHORES...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NORTHWEST SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI AND BIG ISLAND.

GALE WARNING UNTIL 6 AM HST TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR REST OF HAWAIIAN
COASTAL WATERS.


&&

$$

DISCUSSION/MARINE...FOSTER
AVAITION...FUJII




000
FXHW60 PHFO 210156
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
356 PM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT SOME SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS WILL BE MOST ACTIVE DURING
THE NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW DEVELOPING
NORTHWEST OF THE ISLANDS WILL WEAKEN WINDS AND VEER THEM OUT OF
THE SOUTHEAST.

&&

.DISCUSSION...
VISIBLE SATELLITE AND RADAR SHOW SCATTERED PASSING TRADE WIND SHOWERS
ACROSS HAWAII THIS AFTERNOON. TRADE WINDS WILL CONTINUE TO BE
STRONG...DRIVEN BY AN EASTWARD TRAVELING HIGH PRESSURE SYSTEM
NORTH OF THE STATE. THE BREEZY CONDITIONS ARE THE RESULT OF THE
PRESSURE DIFFERENCE BETWEEN THE HIGH AND EQUATORIAL LOW PRESSURE
SOUTH OF THE AREA. AFTERNOON SOUNDINGS SHOW A STABLE ATMOSPHERE
ALOFT WITH SUBSIDENCE INVERSIONS AT AROUND 8000 FEET WITH PRECIPATBLE
WATER VALUES AT BOTH LOCATIONS ARE BELOW NORMAL.

ISLAND TOPOGRAPHY...COUPLED WITH THE STRONG TRADE WINDS...IS
RESULTING IN SOME PASSING SHOWERS ACROSS HAWAII LATE THIS
AFTERNOON. WINDWARD AREAS ARE SEEING MOST OF THE SHOWERS...BUT
WINDS ARE CARRYING OCCASIONAL CLOUDS AND SHOWERS ACROSS TO THE
LEEWARD AREAS AS WELL. EXPECT THIS PATTERN TO CONTINUE AT LEAST
THROUGH TUESDAY NIGHT...WITH MORE SHOWERS DURING THE NIGHTTIME
HOURS. THE ATMOSPHERE WILL REMAIN STABLE...THUS SHOWERS WILL BE
LIGHT AND FAST MOVING.

BOTH GFS AND ECMWF SHOW AN UPPER / SURFACE LOW DEVELOPING NORTHWEST OF
HAWAII ON TUESDAY NIGHT AND WEDNESDAY. THIS SYSTEM IS EXPECTED TO
LINGER TO THE NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A
SIGNIFICANT FRONT / CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD
FROM THE LOW. MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY
AND MOISTURE AHEAD OF THE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN.

MODELS SHOWS THIS FEATURE LINGERING WEST OF HAWAII FROM WEDNESDAY INTO
THE WEEKEND...AND COULD PRODUCE SOME SHOWERS OVER THE WESTERN PORTION
OF THE STATE LATER THIS WEEK. THE LOW IS EXPECTED TO BE CLOSE AND
STRONG ENOUGH TO SHIFT WINDS OUT OF THE SOUTHEAST FROM WEDNESDAY
THROUGH THE WEEKEND TO BRING VOG AND HUMID CONDTIONS OVER THE
STATE. CLOUDS AND SHOWERS MOVING IN WITH THE SOUTHEAST FLOW WILL
FOCUS OVER WINDWARD AND SOUTHEASTERN FACING SLOPES...AND SHOULD BE
A LITTLE BIT WETTER THAN TODAY AND TUESDAY. PLUME CLOUDS AND
SHOWER BANDS MAY SET UP UNDER THESE CONDITIONS. IT IS NOT LIKELY
TO BE UNSTABLE ENOUGH TO PRODUCE HEAVY RAIN...BUT SHOWERS COULD
ANCHOR OVER THE WINDWARD AND SOUTHEAST FACING SLOPES BRINGING MORE
PERSISTENT RAIN.

STILL TOO EARLY TO CALL FOR WEATHER THIS WEEKEND AS THE SYSTEM
WILL REMAIN JUST WEST OF THE STATE WITH GFS AND ECMWF DIVERGING
SOLUTIONS. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER INCREASE IN
MOISTURE OVER NIIHAU AND KAUAI. THIS WILL LEAD TO A POSSIBLE MORE
WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE WEEKEND.


&&

.AVIATION...
STRONG SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SUSTAIN BREEZY
EASTERLY TRADE WINDS THROUGH TONIGHT. OCCASIONAL MVFR CIGS WILL
LIKELY IMPACT WINDWARD SECTIONS THROUGH MID MORNING TUESDAY.
ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AS THE HIGH WILL SHIFTS EAST TUESDAY THE WINDS ACROSS THE ISLANDS
WILL BECOME MORE SOUTHEASTERLY AND WEAKER...WITH THE BIG ISLAND
ACTING AS A SHIELD FOR THE OTHER ISLANDS. THUS THE LOW LEVEL
TURBULENCE AIRMET WILL NOT BE REQUIRED AT THAT POINT IN TIME.


&&

.MARINE...
STRONG WINDS WILL AFFECT ALL HAWAIIAN COASTAL WATERS THROUGH
TUESDAY. A GALE WARNING IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE
ALENUIHAHA CHANNEL...WITH SMALL CRAFT ADVISORIES /SCA/ IN EFFECT
FOR THE REST OF THE COASTAL WATERS. THE SCA WILL LIKELY CONTINUE
FOR ALL WATERS ON TUESDAY...AND BEYOND FOR SELECT ZONES.

WINDS ARE EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE
ISLANDS TUESDAY NIGHT. THE SOUTHEAST FLOW WILL CONTINUE THROUGH
THE REST OF THE WEEK INTO THE WEEKEND.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT AND MAY NEED TO BE EXTENDED IF WINDS ARE
SLOW TO WEAKEN.

A LONG PERIOD SOUTH SWELL WILL SLOWLY BUILD TODAY...AND PEAK AROUND
TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING
SHORES...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NORTHWEST SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI AND BIG ISLAND.

GALE WARNING UNTIL 6 AM HST TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR REST OF HAWAIIAN
COASTAL WATERS.


&&

$$

DISCUSSION/MARINE...FOSTER
AVAITION...FUJII



  [top]

000
ATHW40 PHFO 210029
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0030 UTC TUE APR 21 2015

BASED ON DATA THROUGH 0000 UTC APRIL 21 2015

AS OF 200 PM HST...VISIBLE SATELLITE IMAGERY SHOWED SCATTERED TO
BROKEN LOW CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE
AROUND 700 TO 800 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS
WERE TRACKING WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 25 MPH.
CLOUD TOPS WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID
TO UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 29N AND 30N FROM 156W TO 165W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 20 MPH.

DEEP MOIST CONVECTION WITH EMBEDDED THUNDERSTORMS ASSOCIATED WITH
THE ITCZ WERE SHOWN BETWEEN THE EQUATOR AND 10N. DEBRIS CLOUDS
ASSOCIATED WITH THIS ACTIVITY WERE TRACKING NORTHEASTWARD BETWEEN
10N AND 15N FROM 150W TO 140W.

BROKEN TO OVERCAST LOW CLOUDS WERE GENERALLY FOCUSED OVER THE
WINDWARD SLOPES OF THE MAIN HAWAIIAN ISLANDS. CLOUD TOPS WERE BELOW
10000 FEET. BROKEN TO OVERCAST CONDITIONS WERE SHOWN ACROSS THE
LEEWARD SIDE OF THE BIG ISLAND DUE TO A COMBINATION OF DAYTIME
HEATING AND THE AFTERNOON SEA BREEZE. ELSEWHERE...ISOLATED TO
SCATTERED LOW CLOUDS WERE SHOWN ACROSS THE ISLANDS. AN AREA OF
BROKEN TO OVERCAST LOW CLOUDS ASSOCIATED WITH A CONFLUENT BOUNDARY
DOWNSTREAM OF THE BIG ISLAND WAS SHOWN BETWEEN 18N AND 20N FROM 165W
TO 157W. ELSEWHERE...ISOLATED TO SCATTERED LOW-LEVEL CLOUDS WERE
DEPICTED AROUND THE ISLANDS WITHIN THE TRADE WINDS AND WERE TRACKING
WEST-SOUTHWEST AT 15 TO 20 MPH.

$$

AG






000
ATHW40 PHFO 210029
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0030 UTC TUE APR 21 2015

BASED ON DATA THROUGH 0000 UTC APRIL 21 2015

AS OF 200 PM HST...VISIBLE SATELLITE IMAGERY SHOWED SCATTERED TO
BROKEN LOW CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE
AROUND 700 TO 800 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS
WERE TRACKING WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 25 MPH.
CLOUD TOPS WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID
TO UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 29N AND 30N FROM 156W TO 165W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 20 MPH.

DEEP MOIST CONVECTION WITH EMBEDDED THUNDERSTORMS ASSOCIATED WITH
THE ITCZ WERE SHOWN BETWEEN THE EQUATOR AND 10N. DEBRIS CLOUDS
ASSOCIATED WITH THIS ACTIVITY WERE TRACKING NORTHEASTWARD BETWEEN
10N AND 15N FROM 150W TO 140W.

BROKEN TO OVERCAST LOW CLOUDS WERE GENERALLY FOCUSED OVER THE
WINDWARD SLOPES OF THE MAIN HAWAIIAN ISLANDS. CLOUD TOPS WERE BELOW
10000 FEET. BROKEN TO OVERCAST CONDITIONS WERE SHOWN ACROSS THE
LEEWARD SIDE OF THE BIG ISLAND DUE TO A COMBINATION OF DAYTIME
HEATING AND THE AFTERNOON SEA BREEZE. ELSEWHERE...ISOLATED TO
SCATTERED LOW CLOUDS WERE SHOWN ACROSS THE ISLANDS. AN AREA OF
BROKEN TO OVERCAST LOW CLOUDS ASSOCIATED WITH A CONFLUENT BOUNDARY
DOWNSTREAM OF THE BIG ISLAND WAS SHOWN BETWEEN 18N AND 20N FROM 165W
TO 157W. ELSEWHERE...ISOLATED TO SCATTERED LOW-LEVEL CLOUDS WERE
DEPICTED AROUND THE ISLANDS WITHIN THE TRADE WINDS AND WERE TRACKING
WEST-SOUTHWEST AT 15 TO 20 MPH.

$$

AG





000
ATHW40 PHFO 210029
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0030 UTC TUE APR 21 2015

BASED ON DATA THROUGH 0000 UTC APRIL 21 2015

AS OF 200 PM HST...VISIBLE SATELLITE IMAGERY SHOWED SCATTERED TO
BROKEN LOW CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE
AROUND 700 TO 800 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS
WERE TRACKING WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 25 MPH.
CLOUD TOPS WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID
TO UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 29N AND 30N FROM 156W TO 165W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 20 MPH.

DEEP MOIST CONVECTION WITH EMBEDDED THUNDERSTORMS ASSOCIATED WITH
THE ITCZ WERE SHOWN BETWEEN THE EQUATOR AND 10N. DEBRIS CLOUDS
ASSOCIATED WITH THIS ACTIVITY WERE TRACKING NORTHEASTWARD BETWEEN
10N AND 15N FROM 150W TO 140W.

BROKEN TO OVERCAST LOW CLOUDS WERE GENERALLY FOCUSED OVER THE
WINDWARD SLOPES OF THE MAIN HAWAIIAN ISLANDS. CLOUD TOPS WERE BELOW
10000 FEET. BROKEN TO OVERCAST CONDITIONS WERE SHOWN ACROSS THE
LEEWARD SIDE OF THE BIG ISLAND DUE TO A COMBINATION OF DAYTIME
HEATING AND THE AFTERNOON SEA BREEZE. ELSEWHERE...ISOLATED TO
SCATTERED LOW CLOUDS WERE SHOWN ACROSS THE ISLANDS. AN AREA OF
BROKEN TO OVERCAST LOW CLOUDS ASSOCIATED WITH A CONFLUENT BOUNDARY
DOWNSTREAM OF THE BIG ISLAND WAS SHOWN BETWEEN 18N AND 20N FROM 165W
TO 157W. ELSEWHERE...ISOLATED TO SCATTERED LOW-LEVEL CLOUDS WERE
DEPICTED AROUND THE ISLANDS WITHIN THE TRADE WINDS AND WERE TRACKING
WEST-SOUTHWEST AT 15 TO 20 MPH.

$$

AG





000
ATHW40 PHFO 210029
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0030 UTC TUE APR 21 2015

BASED ON DATA THROUGH 0000 UTC APRIL 21 2015

AS OF 200 PM HST...VISIBLE SATELLITE IMAGERY SHOWED SCATTERED TO
BROKEN LOW CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE
AROUND 700 TO 800 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS
WERE TRACKING WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 25 MPH.
CLOUD TOPS WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID
TO UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 29N AND 30N FROM 156W TO 165W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 20 MPH.

DEEP MOIST CONVECTION WITH EMBEDDED THUNDERSTORMS ASSOCIATED WITH
THE ITCZ WERE SHOWN BETWEEN THE EQUATOR AND 10N. DEBRIS CLOUDS
ASSOCIATED WITH THIS ACTIVITY WERE TRACKING NORTHEASTWARD BETWEEN
10N AND 15N FROM 150W TO 140W.

BROKEN TO OVERCAST LOW CLOUDS WERE GENERALLY FOCUSED OVER THE
WINDWARD SLOPES OF THE MAIN HAWAIIAN ISLANDS. CLOUD TOPS WERE BELOW
10000 FEET. BROKEN TO OVERCAST CONDITIONS WERE SHOWN ACROSS THE
LEEWARD SIDE OF THE BIG ISLAND DUE TO A COMBINATION OF DAYTIME
HEATING AND THE AFTERNOON SEA BREEZE. ELSEWHERE...ISOLATED TO
SCATTERED LOW CLOUDS WERE SHOWN ACROSS THE ISLANDS. AN AREA OF
BROKEN TO OVERCAST LOW CLOUDS ASSOCIATED WITH A CONFLUENT BOUNDARY
DOWNSTREAM OF THE BIG ISLAND WAS SHOWN BETWEEN 18N AND 20N FROM 165W
TO 157W. ELSEWHERE...ISOLATED TO SCATTERED LOW-LEVEL CLOUDS WERE
DEPICTED AROUND THE ISLANDS WITHIN THE TRADE WINDS AND WERE TRACKING
WEST-SOUTHWEST AT 15 TO 20 MPH.

$$

AG





000
ATHW40 PHFO 210029
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0030 UTC TUE APR 21 2015

BASED ON DATA THROUGH 0000 UTC APRIL 21 2015

AS OF 200 PM HST...VISIBLE SATELLITE IMAGERY SHOWED SCATTERED TO
BROKEN LOW CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE
AROUND 700 TO 800 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS
WERE TRACKING WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 25 MPH.
CLOUD TOPS WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID
TO UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 29N AND 30N FROM 156W TO 165W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 20 MPH.

DEEP MOIST CONVECTION WITH EMBEDDED THUNDERSTORMS ASSOCIATED WITH
THE ITCZ WERE SHOWN BETWEEN THE EQUATOR AND 10N. DEBRIS CLOUDS
ASSOCIATED WITH THIS ACTIVITY WERE TRACKING NORTHEASTWARD BETWEEN
10N AND 15N FROM 150W TO 140W.

BROKEN TO OVERCAST LOW CLOUDS WERE GENERALLY FOCUSED OVER THE
WINDWARD SLOPES OF THE MAIN HAWAIIAN ISLANDS. CLOUD TOPS WERE BELOW
10000 FEET. BROKEN TO OVERCAST CONDITIONS WERE SHOWN ACROSS THE
LEEWARD SIDE OF THE BIG ISLAND DUE TO A COMBINATION OF DAYTIME
HEATING AND THE AFTERNOON SEA BREEZE. ELSEWHERE...ISOLATED TO
SCATTERED LOW CLOUDS WERE SHOWN ACROSS THE ISLANDS. AN AREA OF
BROKEN TO OVERCAST LOW CLOUDS ASSOCIATED WITH A CONFLUENT BOUNDARY
DOWNSTREAM OF THE BIG ISLAND WAS SHOWN BETWEEN 18N AND 20N FROM 165W
TO 157W. ELSEWHERE...ISOLATED TO SCATTERED LOW-LEVEL CLOUDS WERE
DEPICTED AROUND THE ISLANDS WITHIN THE TRADE WINDS AND WERE TRACKING
WEST-SOUTHWEST AT 15 TO 20 MPH.

$$

AG





000
ATHW40 PHFO 210029
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0030 UTC TUE APR 21 2015

BASED ON DATA THROUGH 0000 UTC APRIL 21 2015

AS OF 200 PM HST...VISIBLE SATELLITE IMAGERY SHOWED SCATTERED TO
BROKEN LOW CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE
AROUND 700 TO 800 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS
WERE TRACKING WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 25 MPH.
CLOUD TOPS WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID
TO UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 29N AND 30N FROM 156W TO 165W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 20 MPH.

DEEP MOIST CONVECTION WITH EMBEDDED THUNDERSTORMS ASSOCIATED WITH
THE ITCZ WERE SHOWN BETWEEN THE EQUATOR AND 10N. DEBRIS CLOUDS
ASSOCIATED WITH THIS ACTIVITY WERE TRACKING NORTHEASTWARD BETWEEN
10N AND 15N FROM 150W TO 140W.

BROKEN TO OVERCAST LOW CLOUDS WERE GENERALLY FOCUSED OVER THE
WINDWARD SLOPES OF THE MAIN HAWAIIAN ISLANDS. CLOUD TOPS WERE BELOW
10000 FEET. BROKEN TO OVERCAST CONDITIONS WERE SHOWN ACROSS THE
LEEWARD SIDE OF THE BIG ISLAND DUE TO A COMBINATION OF DAYTIME
HEATING AND THE AFTERNOON SEA BREEZE. ELSEWHERE...ISOLATED TO
SCATTERED LOW CLOUDS WERE SHOWN ACROSS THE ISLANDS. AN AREA OF
BROKEN TO OVERCAST LOW CLOUDS ASSOCIATED WITH A CONFLUENT BOUNDARY
DOWNSTREAM OF THE BIG ISLAND WAS SHOWN BETWEEN 18N AND 20N FROM 165W
TO 157W. ELSEWHERE...ISOLATED TO SCATTERED LOW-LEVEL CLOUDS WERE
DEPICTED AROUND THE ISLANDS WITHIN THE TRADE WINDS AND WERE TRACKING
WEST-SOUTHWEST AT 15 TO 20 MPH.

$$

AG





000
FXHW60 PHFO 202001
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1001 AM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS WILL BE MOST ACTIVE DURING
THE NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW
DEVELOPING NORTHWEST OF THE ISLANDS WILL WEAKEN WINDS AND VEER
THEM OUT OF THE SOUTHEAST.

&&

.DISCUSSION...
VISIBLE SATELLITE AND RADAR SHOW SCATTERED PASSING TRADE WIND SHOWERS
ACROSS HAWAII THIS MORNING. TRADE WINDS WILL CONTINUE TO BE
STRONG TODAY...DRIVEN BY AN EASTWARD TRAVELING HIGH PRESSURE
SYSTEM NORTH OF THE STATE. THE BREEZY CONDITIONS ARE THE RESULT OF
THE PRESSURE DIFFERENCE BETWEEN THE HIGH AND EQUATORIAL LOW
PRESSURE SOUTH OF THE AREA. A STABLE ATMOSPHERE PERSISTS ALOFT
WITH SUSIDENCE INVERSIONS AT 7000 FEET AT LIHUE TO 9000 FEET AT
HILO. PRECIPATBLE WATER VALUES AT BOTH LOCATIONS ARE BELOW NORMAL.

EXPECT A FEW PASSING LOW CLOUDS AND SHOWERS TO CONTINUE AFFECT THE
ISLANDS TODAY AND THROUGH THE NEXT FEW DAYS...WITH WINDWARD AREAS
SEEING THE MOST. SOME SHOWERS WILL REACH THE LEE AREAS OF THE
SMALLER ISLANDS UNDER THE BRISK WINDS. THE ATMOSPHERE WILL REMAIN
STABLE...THUS SHOWERS WILL BE LIGHT AND FAST MOVING.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A SIGNIFICANT
FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM THE LOW.
MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY AND MOISTURE
AHEAD OF THE FRONT/CONVERGENCE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN AROUND MID-WEEK. MEANWHILE...A STRONG MID LEVEL RIDGE
WILL KEEP MORE STABLE WEATHER IN PLACE OVER THE EASTERN
ISLANDS...MAINLY MAUI COUNTY AND THE BIG ISLAND. THIS SURFACE LOW IS
EXPECTED TO BE CLOSE ENOUGH TO THE ISLANDS RESULTING IN WINDS
VEERING TO MORE SOUTHEAST FROM TUESDAY INTO THE WEEKEND...ESPECIALLY
OVER THE WESTERN END OF THE ISLAND CHAIN. PRECIPITATION SHOULD
CONTINUE TO FAVOR WINDWARD AREAS IN THE MEANTIME...BUT WITH AN
INCREASINGLY SOUTHERLY COMPONENT TO THE WINDS...PLUME CLOUD BANDS
DEVELOPING ALONG THE WAKE OF THE ISLANDS MAY BRING MORE CLOUDS AND
SHOWERS TO THE DOWNWIND ISLANDS...ESPECIALLY FOR THE WESTERN
ISLANDS. THE VOG PLUME IS EXPECTED TO TRAIN OVER THE SMALLER
ISLANDS LIKELY BEGINING ON WEDNESDAY AND CONTINUING THROUGH THE
WEEKEND.

LATEST MODEL SOLUTIONS CONTINUE TO DIVERGE A BIT ON HOW CLOSE THIS
LINGERING FRONT/CONVERGENCE BAND WILL GET TO THE ISLANDS...WITH
ECMWF NOW HAS IT VERY CLOSE TO KAUAI BY THE WEEKEND WHILE GFS HAS IT
STAYS A LITTLE MORE WEST. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER
INCREASE IN MOISTURE OVER NIIHAU AND KAUAI BY THE WEEKEND. THIS WILL
LEAD TO A POSSIBLE MORE WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE
WEEKEND. ONCE AGAIN...FORECAST CONFIDENCE IS LOW DUE TO THE
DIFFERENCES BETWEEN MODELS.

&&

.AVIATION...
STRONG SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SUSTAIN BREEZY
EASTERLY TRADE WINDS THROUGH TONIGHT. OCCASIONAL MVFR CIGS WILL
LIKELY IMPACT WINDWARD SECTIONS THROUGH MID MORNING TUESDAY.
ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AS THE HIGH WILL SHIFTS EAST TUESDAY THE WINDS ACROSS THE ISLANDS
WILL BECOME MORE SOUTHEASTERLY AND WEAKER...WITH THE BIG ISLAND
ACTING AS A SHIELD FOR THE OTHER ISLANDS. THUS THE LOW LEVEL
TURBULENCE AIRMET WILL NOT BE REQUIRED AT THAT POINT IN TIME.


&&

.MARINE...
STRONG WINDS WILL AFFECT ALL HAWAIIAN COASTAL WATERS THROUGH
TUESDAY. A GALE WARNING IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE
ALENUIHAHA CHANNEL...WITH SMALL CRAFT ADVISORIES /SCA/ IN EFFECT
FOR THE REST OF THE COASTAL WATERS. THE SCA WILL LIKELY CONTINUE
FOR ALL WATERS ON TUESDAY...AND BEYOND FOR SELECT ZONES.

WINDS ARE EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE
ISLANDS TUESDAY NIGHT. THE SOUTHEAST FLOW WILL CONTINUE THROUGH
THE REST OF THE WEEK INTO THE WEEKEND.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

A LONG PERIOD SOUTH SWELL WILL SLOWLY BUILD TODAY...AND PEAK AROUND
TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING
SHORES...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NORTHWEST SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI AND BIG ISLAND.

GALE WARNING UNTIL 6 AM HST TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR REST OF HAWAIIAN
COASTAL WATERS.


&&

$$

DISCUSSION/MARINE...FOSTER
AVAITION...FUJII





000
FXHW60 PHFO 202001
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1001 AM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS WILL BE MOST ACTIVE DURING
THE NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW
DEVELOPING NORTHWEST OF THE ISLANDS WILL WEAKEN WINDS AND VEER
THEM OUT OF THE SOUTHEAST.

&&

.DISCUSSION...
VISIBLE SATELLITE AND RADAR SHOW SCATTERED PASSING TRADE WIND SHOWERS
ACROSS HAWAII THIS MORNING. TRADE WINDS WILL CONTINUE TO BE
STRONG TODAY...DRIVEN BY AN EASTWARD TRAVELING HIGH PRESSURE
SYSTEM NORTH OF THE STATE. THE BREEZY CONDITIONS ARE THE RESULT OF
THE PRESSURE DIFFERENCE BETWEEN THE HIGH AND EQUATORIAL LOW
PRESSURE SOUTH OF THE AREA. A STABLE ATMOSPHERE PERSISTS ALOFT
WITH SUSIDENCE INVERSIONS AT 7000 FEET AT LIHUE TO 9000 FEET AT
HILO. PRECIPATBLE WATER VALUES AT BOTH LOCATIONS ARE BELOW NORMAL.

EXPECT A FEW PASSING LOW CLOUDS AND SHOWERS TO CONTINUE AFFECT THE
ISLANDS TODAY AND THROUGH THE NEXT FEW DAYS...WITH WINDWARD AREAS
SEEING THE MOST. SOME SHOWERS WILL REACH THE LEE AREAS OF THE
SMALLER ISLANDS UNDER THE BRISK WINDS. THE ATMOSPHERE WILL REMAIN
STABLE...THUS SHOWERS WILL BE LIGHT AND FAST MOVING.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A SIGNIFICANT
FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM THE LOW.
MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY AND MOISTURE
AHEAD OF THE FRONT/CONVERGENCE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN AROUND MID-WEEK. MEANWHILE...A STRONG MID LEVEL RIDGE
WILL KEEP MORE STABLE WEATHER IN PLACE OVER THE EASTERN
ISLANDS...MAINLY MAUI COUNTY AND THE BIG ISLAND. THIS SURFACE LOW IS
EXPECTED TO BE CLOSE ENOUGH TO THE ISLANDS RESULTING IN WINDS
VEERING TO MORE SOUTHEAST FROM TUESDAY INTO THE WEEKEND...ESPECIALLY
OVER THE WESTERN END OF THE ISLAND CHAIN. PRECIPITATION SHOULD
CONTINUE TO FAVOR WINDWARD AREAS IN THE MEANTIME...BUT WITH AN
INCREASINGLY SOUTHERLY COMPONENT TO THE WINDS...PLUME CLOUD BANDS
DEVELOPING ALONG THE WAKE OF THE ISLANDS MAY BRING MORE CLOUDS AND
SHOWERS TO THE DOWNWIND ISLANDS...ESPECIALLY FOR THE WESTERN
ISLANDS. THE VOG PLUME IS EXPECTED TO TRAIN OVER THE SMALLER
ISLANDS LIKELY BEGINING ON WEDNESDAY AND CONTINUING THROUGH THE
WEEKEND.

LATEST MODEL SOLUTIONS CONTINUE TO DIVERGE A BIT ON HOW CLOSE THIS
LINGERING FRONT/CONVERGENCE BAND WILL GET TO THE ISLANDS...WITH
ECMWF NOW HAS IT VERY CLOSE TO KAUAI BY THE WEEKEND WHILE GFS HAS IT
STAYS A LITTLE MORE WEST. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER
INCREASE IN MOISTURE OVER NIIHAU AND KAUAI BY THE WEEKEND. THIS WILL
LEAD TO A POSSIBLE MORE WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE
WEEKEND. ONCE AGAIN...FORECAST CONFIDENCE IS LOW DUE TO THE
DIFFERENCES BETWEEN MODELS.

&&

.AVIATION...
STRONG SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SUSTAIN BREEZY
EASTERLY TRADE WINDS THROUGH TONIGHT. OCCASIONAL MVFR CIGS WILL
LIKELY IMPACT WINDWARD SECTIONS THROUGH MID MORNING TUESDAY.
ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AS THE HIGH WILL SHIFTS EAST TUESDAY THE WINDS ACROSS THE ISLANDS
WILL BECOME MORE SOUTHEASTERLY AND WEAKER...WITH THE BIG ISLAND
ACTING AS A SHIELD FOR THE OTHER ISLANDS. THUS THE LOW LEVEL
TURBULENCE AIRMET WILL NOT BE REQUIRED AT THAT POINT IN TIME.


&&

.MARINE...
STRONG WINDS WILL AFFECT ALL HAWAIIAN COASTAL WATERS THROUGH
TUESDAY. A GALE WARNING IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE
ALENUIHAHA CHANNEL...WITH SMALL CRAFT ADVISORIES /SCA/ IN EFFECT
FOR THE REST OF THE COASTAL WATERS. THE SCA WILL LIKELY CONTINUE
FOR ALL WATERS ON TUESDAY...AND BEYOND FOR SELECT ZONES.

WINDS ARE EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE
ISLANDS TUESDAY NIGHT. THE SOUTHEAST FLOW WILL CONTINUE THROUGH
THE REST OF THE WEEK INTO THE WEEKEND.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

A LONG PERIOD SOUTH SWELL WILL SLOWLY BUILD TODAY...AND PEAK AROUND
TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING
SHORES...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NORTHWEST SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI AND BIG ISLAND.

GALE WARNING UNTIL 6 AM HST TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR REST OF HAWAIIAN
COASTAL WATERS.


&&

$$

DISCUSSION/MARINE...FOSTER
AVAITION...FUJII





000
FXHW60 PHFO 202001
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1001 AM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS WILL BE MOST ACTIVE DURING
THE NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW
DEVELOPING NORTHWEST OF THE ISLANDS WILL WEAKEN WINDS AND VEER
THEM OUT OF THE SOUTHEAST.

&&

.DISCUSSION...
VISIBLE SATELLITE AND RADAR SHOW SCATTERED PASSING TRADE WIND SHOWERS
ACROSS HAWAII THIS MORNING. TRADE WINDS WILL CONTINUE TO BE
STRONG TODAY...DRIVEN BY AN EASTWARD TRAVELING HIGH PRESSURE
SYSTEM NORTH OF THE STATE. THE BREEZY CONDITIONS ARE THE RESULT OF
THE PRESSURE DIFFERENCE BETWEEN THE HIGH AND EQUATORIAL LOW
PRESSURE SOUTH OF THE AREA. A STABLE ATMOSPHERE PERSISTS ALOFT
WITH SUSIDENCE INVERSIONS AT 7000 FEET AT LIHUE TO 9000 FEET AT
HILO. PRECIPATBLE WATER VALUES AT BOTH LOCATIONS ARE BELOW NORMAL.

EXPECT A FEW PASSING LOW CLOUDS AND SHOWERS TO CONTINUE AFFECT THE
ISLANDS TODAY AND THROUGH THE NEXT FEW DAYS...WITH WINDWARD AREAS
SEEING THE MOST. SOME SHOWERS WILL REACH THE LEE AREAS OF THE
SMALLER ISLANDS UNDER THE BRISK WINDS. THE ATMOSPHERE WILL REMAIN
STABLE...THUS SHOWERS WILL BE LIGHT AND FAST MOVING.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A SIGNIFICANT
FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM THE LOW.
MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY AND MOISTURE
AHEAD OF THE FRONT/CONVERGENCE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN AROUND MID-WEEK. MEANWHILE...A STRONG MID LEVEL RIDGE
WILL KEEP MORE STABLE WEATHER IN PLACE OVER THE EASTERN
ISLANDS...MAINLY MAUI COUNTY AND THE BIG ISLAND. THIS SURFACE LOW IS
EXPECTED TO BE CLOSE ENOUGH TO THE ISLANDS RESULTING IN WINDS
VEERING TO MORE SOUTHEAST FROM TUESDAY INTO THE WEEKEND...ESPECIALLY
OVER THE WESTERN END OF THE ISLAND CHAIN. PRECIPITATION SHOULD
CONTINUE TO FAVOR WINDWARD AREAS IN THE MEANTIME...BUT WITH AN
INCREASINGLY SOUTHERLY COMPONENT TO THE WINDS...PLUME CLOUD BANDS
DEVELOPING ALONG THE WAKE OF THE ISLANDS MAY BRING MORE CLOUDS AND
SHOWERS TO THE DOWNWIND ISLANDS...ESPECIALLY FOR THE WESTERN
ISLANDS. THE VOG PLUME IS EXPECTED TO TRAIN OVER THE SMALLER
ISLANDS LIKELY BEGINING ON WEDNESDAY AND CONTINUING THROUGH THE
WEEKEND.

LATEST MODEL SOLUTIONS CONTINUE TO DIVERGE A BIT ON HOW CLOSE THIS
LINGERING FRONT/CONVERGENCE BAND WILL GET TO THE ISLANDS...WITH
ECMWF NOW HAS IT VERY CLOSE TO KAUAI BY THE WEEKEND WHILE GFS HAS IT
STAYS A LITTLE MORE WEST. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER
INCREASE IN MOISTURE OVER NIIHAU AND KAUAI BY THE WEEKEND. THIS WILL
LEAD TO A POSSIBLE MORE WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE
WEEKEND. ONCE AGAIN...FORECAST CONFIDENCE IS LOW DUE TO THE
DIFFERENCES BETWEEN MODELS.

&&

.AVIATION...
STRONG SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SUSTAIN BREEZY
EASTERLY TRADE WINDS THROUGH TONIGHT. OCCASIONAL MVFR CIGS WILL
LIKELY IMPACT WINDWARD SECTIONS THROUGH MID MORNING TUESDAY.
ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AS THE HIGH WILL SHIFTS EAST TUESDAY THE WINDS ACROSS THE ISLANDS
WILL BECOME MORE SOUTHEASTERLY AND WEAKER...WITH THE BIG ISLAND
ACTING AS A SHIELD FOR THE OTHER ISLANDS. THUS THE LOW LEVEL
TURBULENCE AIRMET WILL NOT BE REQUIRED AT THAT POINT IN TIME.


&&

.MARINE...
STRONG WINDS WILL AFFECT ALL HAWAIIAN COASTAL WATERS THROUGH
TUESDAY. A GALE WARNING IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE
ALENUIHAHA CHANNEL...WITH SMALL CRAFT ADVISORIES /SCA/ IN EFFECT
FOR THE REST OF THE COASTAL WATERS. THE SCA WILL LIKELY CONTINUE
FOR ALL WATERS ON TUESDAY...AND BEYOND FOR SELECT ZONES.

WINDS ARE EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE
ISLANDS TUESDAY NIGHT. THE SOUTHEAST FLOW WILL CONTINUE THROUGH
THE REST OF THE WEEK INTO THE WEEKEND.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

A LONG PERIOD SOUTH SWELL WILL SLOWLY BUILD TODAY...AND PEAK AROUND
TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING
SHORES...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NORTHWEST SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI AND BIG ISLAND.

GALE WARNING UNTIL 6 AM HST TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR REST OF HAWAIIAN
COASTAL WATERS.


&&

$$

DISCUSSION/MARINE...FOSTER
AVAITION...FUJII





000
FXHW60 PHFO 202001
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1001 AM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS WILL BE MOST ACTIVE DURING
THE NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW
DEVELOPING NORTHWEST OF THE ISLANDS WILL WEAKEN WINDS AND VEER
THEM OUT OF THE SOUTHEAST.

&&

.DISCUSSION...
VISIBLE SATELLITE AND RADAR SHOW SCATTERED PASSING TRADE WIND SHOWERS
ACROSS HAWAII THIS MORNING. TRADE WINDS WILL CONTINUE TO BE
STRONG TODAY...DRIVEN BY AN EASTWARD TRAVELING HIGH PRESSURE
SYSTEM NORTH OF THE STATE. THE BREEZY CONDITIONS ARE THE RESULT OF
THE PRESSURE DIFFERENCE BETWEEN THE HIGH AND EQUATORIAL LOW
PRESSURE SOUTH OF THE AREA. A STABLE ATMOSPHERE PERSISTS ALOFT
WITH SUSIDENCE INVERSIONS AT 7000 FEET AT LIHUE TO 9000 FEET AT
HILO. PRECIPATBLE WATER VALUES AT BOTH LOCATIONS ARE BELOW NORMAL.

EXPECT A FEW PASSING LOW CLOUDS AND SHOWERS TO CONTINUE AFFECT THE
ISLANDS TODAY AND THROUGH THE NEXT FEW DAYS...WITH WINDWARD AREAS
SEEING THE MOST. SOME SHOWERS WILL REACH THE LEE AREAS OF THE
SMALLER ISLANDS UNDER THE BRISK WINDS. THE ATMOSPHERE WILL REMAIN
STABLE...THUS SHOWERS WILL BE LIGHT AND FAST MOVING.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A SIGNIFICANT
FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM THE LOW.
MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY AND MOISTURE
AHEAD OF THE FRONT/CONVERGENCE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN AROUND MID-WEEK. MEANWHILE...A STRONG MID LEVEL RIDGE
WILL KEEP MORE STABLE WEATHER IN PLACE OVER THE EASTERN
ISLANDS...MAINLY MAUI COUNTY AND THE BIG ISLAND. THIS SURFACE LOW IS
EXPECTED TO BE CLOSE ENOUGH TO THE ISLANDS RESULTING IN WINDS
VEERING TO MORE SOUTHEAST FROM TUESDAY INTO THE WEEKEND...ESPECIALLY
OVER THE WESTERN END OF THE ISLAND CHAIN. PRECIPITATION SHOULD
CONTINUE TO FAVOR WINDWARD AREAS IN THE MEANTIME...BUT WITH AN
INCREASINGLY SOUTHERLY COMPONENT TO THE WINDS...PLUME CLOUD BANDS
DEVELOPING ALONG THE WAKE OF THE ISLANDS MAY BRING MORE CLOUDS AND
SHOWERS TO THE DOWNWIND ISLANDS...ESPECIALLY FOR THE WESTERN
ISLANDS. THE VOG PLUME IS EXPECTED TO TRAIN OVER THE SMALLER
ISLANDS LIKELY BEGINING ON WEDNESDAY AND CONTINUING THROUGH THE
WEEKEND.

LATEST MODEL SOLUTIONS CONTINUE TO DIVERGE A BIT ON HOW CLOSE THIS
LINGERING FRONT/CONVERGENCE BAND WILL GET TO THE ISLANDS...WITH
ECMWF NOW HAS IT VERY CLOSE TO KAUAI BY THE WEEKEND WHILE GFS HAS IT
STAYS A LITTLE MORE WEST. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER
INCREASE IN MOISTURE OVER NIIHAU AND KAUAI BY THE WEEKEND. THIS WILL
LEAD TO A POSSIBLE MORE WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE
WEEKEND. ONCE AGAIN...FORECAST CONFIDENCE IS LOW DUE TO THE
DIFFERENCES BETWEEN MODELS.

&&

.AVIATION...
STRONG SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SUSTAIN BREEZY
EASTERLY TRADE WINDS THROUGH TONIGHT. OCCASIONAL MVFR CIGS WILL
LIKELY IMPACT WINDWARD SECTIONS THROUGH MID MORNING TUESDAY.
ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AS THE HIGH WILL SHIFTS EAST TUESDAY THE WINDS ACROSS THE ISLANDS
WILL BECOME MORE SOUTHEASTERLY AND WEAKER...WITH THE BIG ISLAND
ACTING AS A SHIELD FOR THE OTHER ISLANDS. THUS THE LOW LEVEL
TURBULENCE AIRMET WILL NOT BE REQUIRED AT THAT POINT IN TIME.


&&

.MARINE...
STRONG WINDS WILL AFFECT ALL HAWAIIAN COASTAL WATERS THROUGH
TUESDAY. A GALE WARNING IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE
ALENUIHAHA CHANNEL...WITH SMALL CRAFT ADVISORIES /SCA/ IN EFFECT
FOR THE REST OF THE COASTAL WATERS. THE SCA WILL LIKELY CONTINUE
FOR ALL WATERS ON TUESDAY...AND BEYOND FOR SELECT ZONES.

WINDS ARE EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE
ISLANDS TUESDAY NIGHT. THE SOUTHEAST FLOW WILL CONTINUE THROUGH
THE REST OF THE WEEK INTO THE WEEKEND.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

A LONG PERIOD SOUTH SWELL WILL SLOWLY BUILD TODAY...AND PEAK AROUND
TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING
SHORES...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NORTHWEST SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST WEDNESDAY FOR EAST FACING SHORES
OF KAUAI...OAHU...MOLOKAI...MAUI AND BIG ISLAND.

GALE WARNING UNTIL 6 AM HST TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR REST OF HAWAIIAN
COASTAL WATERS.


&&

$$

DISCUSSION/MARINE...FOSTER
AVAITION...FUJII





000
ATHW40 PHFO 201828
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1830 UTC MON APR 20 2015

BASED ON DATA THROUGH 1800 UTC APRIL 20 2015

AS OF 800 AM HST...VISIBLE SATELLITE IMAGERY SHOWED BROKEN LOW
CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE AROUND
500 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS WERE TRACKING
WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 30 MPH. CLOUD TOPS
WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID TO
UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 28N AND 30N FROM 156W TO 170W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 10 MPH AND CONTAINED VERY
LITTLE VERTICAL EXTENT.

SCATTERED TO BROKEN DEBRIS CLOUDS ASSOCIATED WITH THUNDERSTORM
ACTIVITY IN THE ITCZ SOUTH OF 10N WERE SHOWN BETWEEN 10N AND 15N
FROM 170W TO 140W. THESE HIGH-LEVEL CLOUDS WERE TRACKING
NORTHEASTWARD.

BROKEN TO OVERCAST LOW-LEVEL CLOUDS WERE SHOWN ACROSS THE MAJORITY
OF KAUAI. SCATTERED TO BROKEN LOW-LEVEL CLOUDS WERE MOSTLY FOCUSING
OVER THE WINDWARD AND INTERIOR AREAS OF OAHU AND MOLOKAI. BROKEN TO
OVERCAST LOW CLOUDS WERE EVIDENT ACROSS THE WINDWARD SLOPES AND THE
ADJACENT COASTAL WATERS DIRECTLY UPSTREAM OF MAUI AND THE BIG
ISLAND. MOSTLY CLEAR TO PARTLY CLOUDY SKIES WERE SHOWN OVER THE
LEEWARD SIDES OF OAHU...MOLOKAI...MAUI AND THE BIG ISLAND. CLOUD
TOPS ACROSS THE MAIN HAWAIIAN ISLANDS WERE GENERALLY LESS THAN 10000
FEET. SCATTERED LOW-LEVEL CLOUDS WERE SHOWN ELSEWHERE UPSTREAM AND
DOWNSTREAM OF THE ISLANDS AND WERE TRACKING WEST-SOUTHWEST AT 20 TO
30 MPH.

$$

AG





000
ATHW40 PHFO 201828
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1830 UTC MON APR 20 2015

BASED ON DATA THROUGH 1800 UTC APRIL 20 2015

AS OF 800 AM HST...VISIBLE SATELLITE IMAGERY SHOWED BROKEN LOW
CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE AROUND
500 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS WERE TRACKING
WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 30 MPH. CLOUD TOPS
WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID TO
UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 28N AND 30N FROM 156W TO 170W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 10 MPH AND CONTAINED VERY
LITTLE VERTICAL EXTENT.

SCATTERED TO BROKEN DEBRIS CLOUDS ASSOCIATED WITH THUNDERSTORM
ACTIVITY IN THE ITCZ SOUTH OF 10N WERE SHOWN BETWEEN 10N AND 15N
FROM 170W TO 140W. THESE HIGH-LEVEL CLOUDS WERE TRACKING
NORTHEASTWARD.

BROKEN TO OVERCAST LOW-LEVEL CLOUDS WERE SHOWN ACROSS THE MAJORITY
OF KAUAI. SCATTERED TO BROKEN LOW-LEVEL CLOUDS WERE MOSTLY FOCUSING
OVER THE WINDWARD AND INTERIOR AREAS OF OAHU AND MOLOKAI. BROKEN TO
OVERCAST LOW CLOUDS WERE EVIDENT ACROSS THE WINDWARD SLOPES AND THE
ADJACENT COASTAL WATERS DIRECTLY UPSTREAM OF MAUI AND THE BIG
ISLAND. MOSTLY CLEAR TO PARTLY CLOUDY SKIES WERE SHOWN OVER THE
LEEWARD SIDES OF OAHU...MOLOKAI...MAUI AND THE BIG ISLAND. CLOUD
TOPS ACROSS THE MAIN HAWAIIAN ISLANDS WERE GENERALLY LESS THAN 10000
FEET. SCATTERED LOW-LEVEL CLOUDS WERE SHOWN ELSEWHERE UPSTREAM AND
DOWNSTREAM OF THE ISLANDS AND WERE TRACKING WEST-SOUTHWEST AT 20 TO
30 MPH.

$$

AG





000
ATHW40 PHFO 201828
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1830 UTC MON APR 20 2015

BASED ON DATA THROUGH 1800 UTC APRIL 20 2015

AS OF 800 AM HST...VISIBLE SATELLITE IMAGERY SHOWED BROKEN LOW
CLOUDS BETWEEN 20N AND 30N FROM 140W TO 150W...WHICH WERE AROUND
500 MILES NORTHEAST OF THE BIG ISLAND. THESE CLOUDS WERE TRACKING
WEST-SOUTHWEST WITHIN THE TRADE WINDS AT 20 TO 30 MPH. CLOUD TOPS
WERE BELOW 10000 FEET DUE TO THE PRESENCE OF VERY DRY MID TO
UPPER-LEVEL AIR.

SCATTERED TO BROKEN LOW CLOUDS ASSOCIATED WITH A STATIONARY FRONTAL
BOUNDARY WERE SHOWN BETWEEN 28N AND 30N FROM 156W TO 170W. THESE
CLOUDS WERE TRACKING WESTWARD AROUND 10 MPH AND CONTAINED VERY
LITTLE VERTICAL EXTENT.

SCATTERED TO BROKEN DEBRIS CLOUDS ASSOCIATED WITH THUNDERSTORM
ACTIVITY IN THE ITCZ SOUTH OF 10N WERE SHOWN BETWEEN 10N AND 15N
FROM 170W TO 140W. THESE HIGH-LEVEL CLOUDS WERE TRACKING
NORTHEASTWARD.

BROKEN TO OVERCAST LOW-LEVEL CLOUDS WERE SHOWN ACROSS THE MAJORITY
OF KAUAI. SCATTERED TO BROKEN LOW-LEVEL CLOUDS WERE MOSTLY FOCUSING
OVER THE WINDWARD AND INTERIOR AREAS OF OAHU AND MOLOKAI. BROKEN TO
OVERCAST LOW CLOUDS WERE EVIDENT ACROSS THE WINDWARD SLOPES AND THE
ADJACENT COASTAL WATERS DIRECTLY UPSTREAM OF MAUI AND THE BIG
ISLAND. MOSTLY CLEAR TO PARTLY CLOUDY SKIES WERE SHOWN OVER THE
LEEWARD SIDES OF OAHU...MOLOKAI...MAUI AND THE BIG ISLAND. CLOUD
TOPS ACROSS THE MAIN HAWAIIAN ISLANDS WERE GENERALLY LESS THAN 10000
FEET. SCATTERED LOW-LEVEL CLOUDS WERE SHOWN ELSEWHERE UPSTREAM AND
DOWNSTREAM OF THE ISLANDS AND WERE TRACKING WEST-SOUTHWEST AT 20 TO
30 MPH.

$$

AG






000
FXHW60 PHFO 201414
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS ARE MOST ACTIVE DURING
NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW DEVELOPING
NORTHWEST OF THE ISLANDS WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN
OVER THE STATE...ESPECIALLY FOR THE WESTERN ISLANDS.

&&

.DISCUSSION...
BRISK TRADE WINDS CONTINUE ACROSS THE ISLANDS EARLY THIS MORNING...
AS A BUILDING SURFACE HIGH PRESSURE PASSES FAR NORTH OF THE STATE.
EARLY MORNING LIHUE AND HILO SOUNDINGS STILL INDICATE A STABLE
AIRMASS IN THE ISLAND VICINITY...WITH LOW LEVEL MOISTURE EXTENDING
FROM 6K FEET ON LIHUE SOUNDING TO 8K FEET ON HILO SOUNDING. THERE IS
UPPER LEVEL RIDGING OVER THE ISLANDS...AND THIS FEATURE IS KEEPING
AIRMASS STABLE IN THE AREA. EVEN THOUGH THE ATMOSPHERE IS
STABLE...MOISTURE EMBEDDED IN THE WIND FLOW IS DEEP ENOUGH FOR LOW
CLOUDS AND SHOWERS TO DEVELOP. FURTHERMORE...STRONG TRADE WINDS
CARRYING THE LOW LEVEL MOISTURE OVER THE TERRAIN ACROSS THE ISLANDS
ALSO AID SHOWER DEVELOPMENT. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS TODAY.
LATEST SATELLITE IMAGERY REVEALED A BROAD PATCH OF LOW CLOUDS OVER
WINDWARD BIG ISLAND EARLY THIS MORNING...WITH MORE SCATTERED LOW
CLOUDS JUST EAST OF THE REST OF THE ISLANDS. THESE CLOUDS WILL REACH
THE AREA THROUGH REST OF THE MORNING...BRINGING MORE SHOWERS. EXPECT
PASSING LOW CLOUDS AND SHOWERS TO CONTINUE AFFECT THE ISLANDS
TODAY...WITH WINDWARD AREAS SEEING THE MOST. RAINFALL AMOUNTS WILL
BE SOMEWHAT LIMITED...DUE TO THE FAST MOVING NATURE OF THESE
SHOWERS.

THE SURFACE HIGH FAR NORTH OF THE ISLANDS WILL TRACK STEADILY FAR
NORTHEAST BY TUESDAY. AS SUCH...BRISK TRADE WINDS WILL CONTINUE
THROUGH MUCH OF TUESDAY. A MID-LEVEL RIDGE WILL PERSIST NEARBY THE
STATE AS WELL...MAINTAINING A STABLE AIRMASS OVER THE AREA. MOISTURE
EMBEDDED IN THE WIND FLOW WILL CONTINUE TO BE DEEP ENOUGH TO BRING
MORE SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A SIGNIFICANT
FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM THE LOW.
MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY AND MOISTURE
AHEAD OF THE FRONT/CONVERGENCE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN AROUND MID-WEEK. MEANWHILE...A STRONG MID LEVEL RIDGE
WILL KEEP MORE STABLE WEATHER IN PLACE OVER THE EASTERN
ISLANDS...MAINLY MAUI COUNTY AND THE BIG ISLAND. THIS SURFACE LOW IS
EXPECTED TO BE CLOSE ENOUGH TO THE ISLANDS RESULTING IN WINDS
VEERING TO MORE SOUTHEAST FROM TUESDAY INTO THE WEEKEND...ESPECIALLY
OVER THE WESTERN END OF THE ISLAND CHAIN. PRECIPITATION SHOULD
CONTINUE TO FAVOR WINDWARD AREAS IN THE MEANTIME...BUT WITH AN
INCREASINGLY SOUTHERLY COMPONENT TO THE WINDS...PLUME CLOUD BANDS
DEVELOPING ALONG THE WAKE OF THE ISLANDS MAY BRING MORE CLOUDS AND
SHOWERS TO THE DOWNWIND ISLANDS...ESPECIALLY FOR THE WESTERN ISLANDS.

LATEST MODEL SOLUTIONS CONTINUE TO DIVERGE A BIT ON HOW CLOSE THIS
LINGERING FRONT/CONVERGENCE BAND WILL GET TO THE ISLANDS...WITH
ECMWF NOW HAS IT VERY CLOSE TO KAUAI BY THE WEEKEND WHILE GFS HAS IT
STAYS A LITTLE MORE WEST. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER
INCREASE IN MOISTURE OVER NIIHAU AND KAUAI BY THE WEEKEND. THIS WILL
LEAD TO A POSSIBLE MORE WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE
WEEKEND. ONCE AGAIN...FORECAST CONFIDENCE IS LOW DUE TO THE
DIFFERENCES BETWEEN MODELS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH TONIGHT...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO AND PHLI THROUGH
MID MORNING. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE DAY. AIRMET SIERRA
MAY BE NEEDED LATER THIS MORNING ACROSS PORTIONS OF THE ISLANDS DUE
TO MOUNTAIN OBSCURATION.

&&

.MARINE...
A GALE WARNING CONTINUES FOR THE ALENUIHAHA CHANNEL EARLY THIS
MORNING DUE TO VERY STRONG TRADE WINDS...AS FINALLY A GOOD
SCATTEROMETER PASS OVER THE ISLANDS SHOWED A 35 KT READING IN THAT
CHANNEL. A SMALL CRAFT ADVISORY /SCA/ ALSO REMAINS IN EFFECT FOR THE
REST OF THE COASTAL WATERS DUE TO THE WINDS. AS THE STRONG TRADES
CONTINUE THROUGH EARLY TUESDAY...EXPECT THE GALE WARNING AS WELL AS
THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL THEN. WINDS ARE
EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE ISLANDS
AFTER TUESDAY...THOUGH STRONG EASTERLY WINDS MAY PERSIST OVER THE
BIG ISLAND COASTAL WATERS...WARRANTING THE POSSIBLE EXTENSION OF THE
SCA FOR THOSE AREAS.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE
EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

THE LONG-PERIOD SSW SWELL WILL SLOWLY BUILD TODAY...AND PEAK
AROUND TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH
FACING SHORES. IT SLOWLY DIMINISHES THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NW SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI






000
FXHW60 PHFO 201414
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS ARE MOST ACTIVE DURING
NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW DEVELOPING
NORTHWEST OF THE ISLANDS WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN
OVER THE STATE...ESPECIALLY FOR THE WESTERN ISLANDS.

&&

.DISCUSSION...
BRISK TRADE WINDS CONTINUE ACROSS THE ISLANDS EARLY THIS MORNING...
AS A BUILDING SURFACE HIGH PRESSURE PASSES FAR NORTH OF THE STATE.
EARLY MORNING LIHUE AND HILO SOUNDINGS STILL INDICATE A STABLE
AIRMASS IN THE ISLAND VICINITY...WITH LOW LEVEL MOISTURE EXTENDING
FROM 6K FEET ON LIHUE SOUNDING TO 8K FEET ON HILO SOUNDING. THERE IS
UPPER LEVEL RIDGING OVER THE ISLANDS...AND THIS FEATURE IS KEEPING
AIRMASS STABLE IN THE AREA. EVEN THOUGH THE ATMOSPHERE IS
STABLE...MOISTURE EMBEDDED IN THE WIND FLOW IS DEEP ENOUGH FOR LOW
CLOUDS AND SHOWERS TO DEVELOP. FURTHERMORE...STRONG TRADE WINDS
CARRYING THE LOW LEVEL MOISTURE OVER THE TERRAIN ACROSS THE ISLANDS
ALSO AID SHOWER DEVELOPMENT. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS TODAY.
LATEST SATELLITE IMAGERY REVEALED A BROAD PATCH OF LOW CLOUDS OVER
WINDWARD BIG ISLAND EARLY THIS MORNING...WITH MORE SCATTERED LOW
CLOUDS JUST EAST OF THE REST OF THE ISLANDS. THESE CLOUDS WILL REACH
THE AREA THROUGH REST OF THE MORNING...BRINGING MORE SHOWERS. EXPECT
PASSING LOW CLOUDS AND SHOWERS TO CONTINUE AFFECT THE ISLANDS
TODAY...WITH WINDWARD AREAS SEEING THE MOST. RAINFALL AMOUNTS WILL
BE SOMEWHAT LIMITED...DUE TO THE FAST MOVING NATURE OF THESE
SHOWERS.

THE SURFACE HIGH FAR NORTH OF THE ISLANDS WILL TRACK STEADILY FAR
NORTHEAST BY TUESDAY. AS SUCH...BRISK TRADE WINDS WILL CONTINUE
THROUGH MUCH OF TUESDAY. A MID-LEVEL RIDGE WILL PERSIST NEARBY THE
STATE AS WELL...MAINTAINING A STABLE AIRMASS OVER THE AREA. MOISTURE
EMBEDDED IN THE WIND FLOW WILL CONTINUE TO BE DEEP ENOUGH TO BRING
MORE SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A SIGNIFICANT
FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM THE LOW.
MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY AND MOISTURE
AHEAD OF THE FRONT/CONVERGENCE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN AROUND MID-WEEK. MEANWHILE...A STRONG MID LEVEL RIDGE
WILL KEEP MORE STABLE WEATHER IN PLACE OVER THE EASTERN
ISLANDS...MAINLY MAUI COUNTY AND THE BIG ISLAND. THIS SURFACE LOW IS
EXPECTED TO BE CLOSE ENOUGH TO THE ISLANDS RESULTING IN WINDS
VEERING TO MORE SOUTHEAST FROM TUESDAY INTO THE WEEKEND...ESPECIALLY
OVER THE WESTERN END OF THE ISLAND CHAIN. PRECIPITATION SHOULD
CONTINUE TO FAVOR WINDWARD AREAS IN THE MEANTIME...BUT WITH AN
INCREASINGLY SOUTHERLY COMPONENT TO THE WINDS...PLUME CLOUD BANDS
DEVELOPING ALONG THE WAKE OF THE ISLANDS MAY BRING MORE CLOUDS AND
SHOWERS TO THE DOWNWIND ISLANDS...ESPECIALLY FOR THE WESTERN ISLANDS.

LATEST MODEL SOLUTIONS CONTINUE TO DIVERGE A BIT ON HOW CLOSE THIS
LINGERING FRONT/CONVERGENCE BAND WILL GET TO THE ISLANDS...WITH
ECMWF NOW HAS IT VERY CLOSE TO KAUAI BY THE WEEKEND WHILE GFS HAS IT
STAYS A LITTLE MORE WEST. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER
INCREASE IN MOISTURE OVER NIIHAU AND KAUAI BY THE WEEKEND. THIS WILL
LEAD TO A POSSIBLE MORE WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE
WEEKEND. ONCE AGAIN...FORECAST CONFIDENCE IS LOW DUE TO THE
DIFFERENCES BETWEEN MODELS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH TONIGHT...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO AND PHLI THROUGH
MID MORNING. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE DAY. AIRMET SIERRA
MAY BE NEEDED LATER THIS MORNING ACROSS PORTIONS OF THE ISLANDS DUE
TO MOUNTAIN OBSCURATION.

&&

.MARINE...
A GALE WARNING CONTINUES FOR THE ALENUIHAHA CHANNEL EARLY THIS
MORNING DUE TO VERY STRONG TRADE WINDS...AS FINALLY A GOOD
SCATTEROMETER PASS OVER THE ISLANDS SHOWED A 35 KT READING IN THAT
CHANNEL. A SMALL CRAFT ADVISORY /SCA/ ALSO REMAINS IN EFFECT FOR THE
REST OF THE COASTAL WATERS DUE TO THE WINDS. AS THE STRONG TRADES
CONTINUE THROUGH EARLY TUESDAY...EXPECT THE GALE WARNING AS WELL AS
THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL THEN. WINDS ARE
EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE ISLANDS
AFTER TUESDAY...THOUGH STRONG EASTERLY WINDS MAY PERSIST OVER THE
BIG ISLAND COASTAL WATERS...WARRANTING THE POSSIBLE EXTENSION OF THE
SCA FOR THOSE AREAS.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE
EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

THE LONG-PERIOD SSW SWELL WILL SLOWLY BUILD TODAY...AND PEAK
AROUND TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH
FACING SHORES. IT SLOWLY DIMINISHES THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NW SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 201414
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST MON APR 20 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD OF THE SMALLER ISLANDS. SHOWERS ARE MOST ACTIVE DURING
NIGHTS AND MORNINGS. BY THE MIDDLE OF THE WEEK...A LOW DEVELOPING
NORTHWEST OF THE ISLANDS WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN
OVER THE STATE...ESPECIALLY FOR THE WESTERN ISLANDS.

&&

.DISCUSSION...
BRISK TRADE WINDS CONTINUE ACROSS THE ISLANDS EARLY THIS MORNING...
AS A BUILDING SURFACE HIGH PRESSURE PASSES FAR NORTH OF THE STATE.
EARLY MORNING LIHUE AND HILO SOUNDINGS STILL INDICATE A STABLE
AIRMASS IN THE ISLAND VICINITY...WITH LOW LEVEL MOISTURE EXTENDING
FROM 6K FEET ON LIHUE SOUNDING TO 8K FEET ON HILO SOUNDING. THERE IS
UPPER LEVEL RIDGING OVER THE ISLANDS...AND THIS FEATURE IS KEEPING
AIRMASS STABLE IN THE AREA. EVEN THOUGH THE ATMOSPHERE IS
STABLE...MOISTURE EMBEDDED IN THE WIND FLOW IS DEEP ENOUGH FOR LOW
CLOUDS AND SHOWERS TO DEVELOP. FURTHERMORE...STRONG TRADE WINDS
CARRYING THE LOW LEVEL MOISTURE OVER THE TERRAIN ACROSS THE ISLANDS
ALSO AID SHOWER DEVELOPMENT. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS TODAY.
LATEST SATELLITE IMAGERY REVEALED A BROAD PATCH OF LOW CLOUDS OVER
WINDWARD BIG ISLAND EARLY THIS MORNING...WITH MORE SCATTERED LOW
CLOUDS JUST EAST OF THE REST OF THE ISLANDS. THESE CLOUDS WILL REACH
THE AREA THROUGH REST OF THE MORNING...BRINGING MORE SHOWERS. EXPECT
PASSING LOW CLOUDS AND SHOWERS TO CONTINUE AFFECT THE ISLANDS
TODAY...WITH WINDWARD AREAS SEEING THE MOST. RAINFALL AMOUNTS WILL
BE SOMEWHAT LIMITED...DUE TO THE FAST MOVING NATURE OF THESE
SHOWERS.

THE SURFACE HIGH FAR NORTH OF THE ISLANDS WILL TRACK STEADILY FAR
NORTHEAST BY TUESDAY. AS SUCH...BRISK TRADE WINDS WILL CONTINUE
THROUGH MUCH OF TUESDAY. A MID-LEVEL RIDGE WILL PERSIST NEARBY THE
STATE AS WELL...MAINTAINING A STABLE AIRMASS OVER THE AREA. MOISTURE
EMBEDDED IN THE WIND FLOW WILL CONTINUE TO BE DEEP ENOUGH TO BRING
MORE SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE THROUGH THE WEEKEND...WITH A SIGNIFICANT
FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM THE LOW.
MODEL SOLUTIONS BRING A SLIGHT INCREASE IN INSTABILITY AND MOISTURE
AHEAD OF THE FRONT/CONVERGENCE BAND OVER THE WESTERN PORTION OF THE
ISLAND CHAIN AROUND MID-WEEK. MEANWHILE...A STRONG MID LEVEL RIDGE
WILL KEEP MORE STABLE WEATHER IN PLACE OVER THE EASTERN
ISLANDS...MAINLY MAUI COUNTY AND THE BIG ISLAND. THIS SURFACE LOW IS
EXPECTED TO BE CLOSE ENOUGH TO THE ISLANDS RESULTING IN WINDS
VEERING TO MORE SOUTHEAST FROM TUESDAY INTO THE WEEKEND...ESPECIALLY
OVER THE WESTERN END OF THE ISLAND CHAIN. PRECIPITATION SHOULD
CONTINUE TO FAVOR WINDWARD AREAS IN THE MEANTIME...BUT WITH AN
INCREASINGLY SOUTHERLY COMPONENT TO THE WINDS...PLUME CLOUD BANDS
DEVELOPING ALONG THE WAKE OF THE ISLANDS MAY BRING MORE CLOUDS AND
SHOWERS TO THE DOWNWIND ISLANDS...ESPECIALLY FOR THE WESTERN ISLANDS.

LATEST MODEL SOLUTIONS CONTINUE TO DIVERGE A BIT ON HOW CLOSE THIS
LINGERING FRONT/CONVERGENCE BAND WILL GET TO THE ISLANDS...WITH
ECMWF NOW HAS IT VERY CLOSE TO KAUAI BY THE WEEKEND WHILE GFS HAS IT
STAYS A LITTLE MORE WEST. REGARDLESS...BOTH SOLUTIONS HINT A FURTHER
INCREASE IN MOISTURE OVER NIIHAU AND KAUAI BY THE WEEKEND. THIS WILL
LEAD TO A POSSIBLE MORE WIDESPREAD SHOWERS FOR THOSE ISLANDS FOR THE
WEEKEND. ONCE AGAIN...FORECAST CONFIDENCE IS LOW DUE TO THE
DIFFERENCES BETWEEN MODELS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH TONIGHT...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO AND PHLI THROUGH
MID MORNING. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE DAY. AIRMET SIERRA
MAY BE NEEDED LATER THIS MORNING ACROSS PORTIONS OF THE ISLANDS DUE
TO MOUNTAIN OBSCURATION.

&&

.MARINE...
A GALE WARNING CONTINUES FOR THE ALENUIHAHA CHANNEL EARLY THIS
MORNING DUE TO VERY STRONG TRADE WINDS...AS FINALLY A GOOD
SCATTEROMETER PASS OVER THE ISLANDS SHOWED A 35 KT READING IN THAT
CHANNEL. A SMALL CRAFT ADVISORY /SCA/ ALSO REMAINS IN EFFECT FOR THE
REST OF THE COASTAL WATERS DUE TO THE WINDS. AS THE STRONG TRADES
CONTINUE THROUGH EARLY TUESDAY...EXPECT THE GALE WARNING AS WELL AS
THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL THEN. WINDS ARE
EXPECTED TO WEAKEN A BIT AND VEER SOUTHEASTERLY OVER THE ISLANDS
AFTER TUESDAY...THOUGH STRONG EASTERLY WINDS MAY PERSIST OVER THE
BIG ISLAND COASTAL WATERS...WARRANTING THE POSSIBLE EXTENSION OF THE
SCA FOR THOSE AREAS.

THE STRONG TRADE WINDS WILL CONTINUE TO BRING ADVISORY LEVEL ROUGH
AND CHOPPY SURF ALONG EAST FACING SHORES FOR THE NEXT COUPLE OF
DAYS. THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST
THROUGH TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE
EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

THE LONG-PERIOD SSW SWELL WILL SLOWLY BUILD TODAY...AND PEAK
AROUND TUESDAY...BRINGING NEAR ADVISORY LEVEL SURF ALONG SOUTH
FACING SHORES. IT SLOWLY DIMINISHES THROUGH THE REST OF THE WEEK.
ANOTHER SMALL NW SWELL IS EXPECTED ON TUESDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
ATHW40 PHFO 201159
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1230 UTC MON APR 20 2015

BASED ON DATA THROUGH 1200 UTC APRIL 20 2015

TO THE SOUTH...MODERATE THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 10N TO 01N...MAINLY EAST OF 167W. LAYERED MIDDLE TO HIGH DEBRIS
CLOUDS FROM THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES
MOSTLY TO PARTLY FROM 11N TO THE EQUATOR...AND PARTLY AS FAR NORTH
AS 14N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...LOCALLY MERGING INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. THESE CLOUDS WERE GREATEST IN AREAL
COVERAGE EAST OF THE CURVE FROM 30N 146W TO 20N 151W TO 18N 140W.
THEY GENERALLY ROSE TO HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER
CUMULI AND HIGHER LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED
TOWARD THE WEST SOUTHWEST AT 20 TO 25 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF
CLUMPS OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST...ESPECIALLY OVER MAUI AND THE BIG
ISLAND. LAYERED DEBRIS CLOUDS FROM AFTERNOON CUMULUS BUILDUPS ON
SUNDAY DIMINISHED DURING THE PAST SIX HOURS...BUT STILL LINGERED IN
PLACES ALONG LOWER WEST SLOPES OF THE BIG ISLAND.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER NORTH
THROUGH EAST MAUI...ALONG THE HAMAKUA COAST ON THE BIG ISLAND...
OFFSHORE TO THE NORTH THROUGH EAST OF OAHU...OFFSHORE TO THE EAST OF
THE BIG ISLAND...AND OFFSHORE IN THE LEE PLUME WELL TO THE WEST OF
THE BIG ISLAND.

$$

RYSHKO






000
ATHW40 PHFO 201159
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1230 UTC MON APR 20 2015

BASED ON DATA THROUGH 1200 UTC APRIL 20 2015

TO THE SOUTH...MODERATE THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 10N TO 01N...MAINLY EAST OF 167W. LAYERED MIDDLE TO HIGH DEBRIS
CLOUDS FROM THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES
MOSTLY TO PARTLY FROM 11N TO THE EQUATOR...AND PARTLY AS FAR NORTH
AS 14N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...LOCALLY MERGING INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. THESE CLOUDS WERE GREATEST IN AREAL
COVERAGE EAST OF THE CURVE FROM 30N 146W TO 20N 151W TO 18N 140W.
THEY GENERALLY ROSE TO HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER
CUMULI AND HIGHER LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED
TOWARD THE WEST SOUTHWEST AT 20 TO 25 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF
CLUMPS OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST...ESPECIALLY OVER MAUI AND THE BIG
ISLAND. LAYERED DEBRIS CLOUDS FROM AFTERNOON CUMULUS BUILDUPS ON
SUNDAY DIMINISHED DURING THE PAST SIX HOURS...BUT STILL LINGERED IN
PLACES ALONG LOWER WEST SLOPES OF THE BIG ISLAND.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER NORTH
THROUGH EAST MAUI...ALONG THE HAMAKUA COAST ON THE BIG ISLAND...
OFFSHORE TO THE NORTH THROUGH EAST OF OAHU...OFFSHORE TO THE EAST OF
THE BIG ISLAND...AND OFFSHORE IN THE LEE PLUME WELL TO THE WEST OF
THE BIG ISLAND.

$$

RYSHKO





000
ATHW40 PHFO 201159
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1230 UTC MON APR 20 2015

BASED ON DATA THROUGH 1200 UTC APRIL 20 2015

TO THE SOUTH...MODERATE THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 10N TO 01N...MAINLY EAST OF 167W. LAYERED MIDDLE TO HIGH DEBRIS
CLOUDS FROM THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES
MOSTLY TO PARTLY FROM 11N TO THE EQUATOR...AND PARTLY AS FAR NORTH
AS 14N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...LOCALLY MERGING INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. THESE CLOUDS WERE GREATEST IN AREAL
COVERAGE EAST OF THE CURVE FROM 30N 146W TO 20N 151W TO 18N 140W.
THEY GENERALLY ROSE TO HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER
CUMULI AND HIGHER LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED
TOWARD THE WEST SOUTHWEST AT 20 TO 25 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF
CLUMPS OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST...ESPECIALLY OVER MAUI AND THE BIG
ISLAND. LAYERED DEBRIS CLOUDS FROM AFTERNOON CUMULUS BUILDUPS ON
SUNDAY DIMINISHED DURING THE PAST SIX HOURS...BUT STILL LINGERED IN
PLACES ALONG LOWER WEST SLOPES OF THE BIG ISLAND.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER NORTH
THROUGH EAST MAUI...ALONG THE HAMAKUA COAST ON THE BIG ISLAND...
OFFSHORE TO THE NORTH THROUGH EAST OF OAHU...OFFSHORE TO THE EAST OF
THE BIG ISLAND...AND OFFSHORE IN THE LEE PLUME WELL TO THE WEST OF
THE BIG ISLAND.

$$

RYSHKO






000
ATHW40 PHFO 201159
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
1230 UTC MON APR 20 2015

BASED ON DATA THROUGH 1200 UTC APRIL 20 2015

TO THE SOUTH...MODERATE THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 10N TO 01N...MAINLY EAST OF 167W. LAYERED MIDDLE TO HIGH DEBRIS
CLOUDS FROM THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES
MOSTLY TO PARTLY FROM 11N TO THE EQUATOR...AND PARTLY AS FAR NORTH
AS 14N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...LOCALLY MERGING INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. THESE CLOUDS WERE GREATEST IN AREAL
COVERAGE EAST OF THE CURVE FROM 30N 146W TO 20N 151W TO 18N 140W.
THEY GENERALLY ROSE TO HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER
CUMULI AND HIGHER LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED
TOWARD THE WEST SOUTHWEST AT 20 TO 25 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF
CLUMPS OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST...ESPECIALLY OVER MAUI AND THE BIG
ISLAND. LAYERED DEBRIS CLOUDS FROM AFTERNOON CUMULUS BUILDUPS ON
SUNDAY DIMINISHED DURING THE PAST SIX HOURS...BUT STILL LINGERED IN
PLACES ALONG LOWER WEST SLOPES OF THE BIG ISLAND.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER NORTH
THROUGH EAST MAUI...ALONG THE HAMAKUA COAST ON THE BIG ISLAND...
OFFSHORE TO THE NORTH THROUGH EAST OF OAHU...OFFSHORE TO THE EAST OF
THE BIG ISLAND...AND OFFSHORE IN THE LEE PLUME WELL TO THE WEST OF
THE BIG ISLAND.

$$

RYSHKO





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
FXHW60 PHFO 200637
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD. SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...POSSIBLY TO KAUAI. MAUI
AND THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
RATHER BRISK TRADE WINDS PREVAIL ACROSS THE ISLANDS THIS EVENING...
AS A BROAD AREA OF SURFACE HIGH PRESSURE PERSISTS FAR NORTH THE
STATE. THERE IS UPPER LEVEL RIDGING OVER OF THE ISLANDS...AND THIS
FEATURE IS KEEPING AIRMASS STABLE IN THE ISLAND VICINITY. DESPITE
THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE WINDS FLOW IS DEEP
ENOUGH FOR LOW CLOUDS AND SHOWERS TO DEVELOP OVER THE OPEN
OCEAN...WHILE STRONG TRADE WIND FLOW CARRYING THE LOW LEVEL MOISTURE
OVER THE TERRAIN ACROSS THE ISLANDS ALSO AIDS SHOWER DEVELOPMENT.
LATEST SATELLITE IMAGERY INDICATED A BROAD AREA OF LOW CLOUDS HAS
REACHED MOST OF THE ISLANDS THIS EVENING...WITH KAUAI GETTING THE
LEAST AMOUNT OF CLOUDS. THERE ARE STILL MORE AREAS OF LOW CLOUDS
EAST OF THE STATE...AND THESE CLOUDS WILL REACH THE AREA THROUGH
REST OF THE EVENING INTO EARLY MONDAY...BRINGING MORE SHOWERS.
THEREFORE PASSING LOW CLOUDS AND SHOWERS WILL CONTINUE AFFECT THE
ISLANDS THROUGH EARLY MONDAY MORNING...WITH WINDWARD AREAS SEEING
THE MOST. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED...DUE TO THE
FAST MOVING NATURE OF THESE FEATURES.

A SURFACE HIGH FAR NORTHWEST WILL TRACK STEADILY EAST AND STRENGTHEN
THROUGH MONDAY. IN TURN...EXPECT TRADE WINDS TO FIRM UP SLIGHTLY
THROUGH EARLY MONDAY...THEN REMAIN RATHER BRISK THROUGH TUESDAY. A
MID-LEVEL RIDGE WILL PERSIST NEARBY THE STATE...MAINTAINING A STABLE
AIRMASS OVER THE AREA. WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.
MOISTURE EMBEDDED IN THE WIND FLOW WILL BE DEEP ENOUGH TO BRING MORE
SHOWERS. HENCE SIMILAR WEATHER REGIME WILL PERSIST THROUGH
TUESDAY...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. SOME SHOWERS WILL REACH THE LEE AREAS OF THE SMALLER
ISLANDS UNDER THE BRISK WINDS.

LATEST MODEL SOLUTIONS ARE IN GOOD AGREEMENT UPON THE EVOLUTION OF
THE SURFACE HIGH TO NORTHEAST FROM WEDNESDAY THROUGH THE END OF THE
WEEK...AS IT IS EXPECTED TO SLOWLY WEAKEN AND DRIFT SOUTH. THERE WILL
ALSO BE A LOW PRESSURE SYSTEM DEVELOPING NORTHWEST OF THE ISLANDS
BEGINNING LATE TUESDAY. THIS SYSTEM IS EXPECTED TO LINGER TO THE
NORTHWEST OF THE STATE AT LEAST FOR SEVERAL DAYS...WITH A
SIGNIFICANT FRONT/CONVERGENCE BAND FEATURE EXTENDING SOUTHWARD FROM
THE LOW. MODEL SOLUTIONS CONTINUE TO BRING A SLIGHT INCREASE IN
INSTABILITY AND MOISTURE AHEAD OF THE FRONT/CONVERGENCE BAND OVER
THE WESTERN PORTION OF THE ISLAND CHAIN AROUND MID-WEEK. LOOKS LIKE
THIS BAND WILL REMAIN JUST WEST OF THE ISLANDS AT THIS TIME.
MEANWHILE...A STRONG MID LEVEL RIDGE WILL KEEP MORE STABLE WEATHER
IN PLACE OVER THE EASTERN ISLANDS...MAINLY MAUI COUNTY AND THE BIG
ISLAND. THIS SURFACE LOW IS EXPECTED TO BE CLOSE ENOUGH TO THE
ISLANDS RESULTING IN WINDS VEERING TO MORE SOUTHEAST FROM TUESDAY
INTO THE NEXT WEEKEND...ESPECIALLY OVER THE WESTERN END OF THE
ISLAND CHAIN. PRECIPITATION SHOULD CONTINUE TO FAVOR WINDWARD AREAS
FOR THE REST OF THE WEEK. BUT WITH AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS...THIS COULD LEAD TO CONVERGENCE CLOUD BANDS
DEVELOPING ALONG THE LEE WAKE OF THE ISLANDS...PROVIDING MORE CLOUDS
AND SHOWERS TO THE ADJACENT ISLAND DOWNWIND...ESPECIALLY FOR THE
WESTERN ISLANDS. SINCE THESE MESO-SCALE FEATURES ARE DIFFICULT TO
GAGE IN ADVANCE...SHALL LEAVE THE PRECIPITATION FORECAST AS IS AT
THIS TIME. MOREOVER...THE FORECAST MAY STILL BE CHANGING SINCE THERE
ARE STILL SUBTLE DIFFERENCES BETWEEN MODEL RUNS.

&&

.AVIATION...
HIGH PRESSURE NORTH OF THE STATE WILL KEEP A BREEZY EAST-NORTHEAST
TRADE WIND FLOW IN PLACE THROUGH MONDAY...WITH CLOUDS AND SHOWERS
PRIMARILY FOCUSED OVER THE MOUNTAINS AND NORTH THRU EAST SECTIONS OF
THE ISLANDS. OCCASIONAL MVFR CIGS MAY IMPACT PHTO...PHNY...PHMK AND
PHLI OVERNIGHT. ELSEWHERE VFR CONDITIONS ARE EXPECTED TO PREVAIL.

AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND
SOUTH THRU WEST OF THE MOUNTAINS ON ALL ISLANDS...AND THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MONDAY. AIRMET SIERRA
MAY BE NEEDED LATER TONIGHT FOR MOUNTAIN OBSCURATION ACROSS PORTIONS
OF THE ISLANDS.

&&

.MARINE...
A GALE WARNING CONTINUES FOR ALENUIHAHA CHANNEL DUE TO VERY STRONG
TRADE WINDS OVER THAT AREA...WHILE A SMALL CRAFT ADVISORY /SCA/
REMAINS IN EFFECT FOR THE REST OF THE COASTAL WATERS. AS THE STRONG
TRADES ARE TO PREVAIL THROUGH EARLY TUESDAY...EXPECT THE GALE
WARNING AS WELL AS THE SMALL CRAFT ADVISORY TO REMAIN POSTED TILL
THEN. WINDS MAY WEAKEN AND VEER SOUTHEASTERLY OVER KAUAI AND OAHU
WATERS AFTER TUESDAY...THOUGH STRONG EAST WINDS OVER MAUI AND THE
BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS ARE ALSO BRINGING ADVISORY LEVEL ROUGH AND
CHOPPY SURF ALONG EAST FACING SHORES THROUGH THE NEXT FEW DAYS.
THEREFORE A HIGH SURF ADVISORY REMAINS IN EFFECT AT LEAST THROUGH
TUESDAY NIGHT. THIS ADVISORY MAY NEED TO BE EXTENDED...ESPECIALLY
FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS PEAKED TODAY WITH ANOTHER ONE EXPECTED ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. THE
EXPECTED LONG-PERIOD SSW SWELL HAS REACHED THE ISLANDS EARLIER TODAY
AS INDICATED BY READING FROM BUOY NEAR LANAI...AND WILL SLOWLY BUILD
INTO TUESDAY. THIS SWELL WILL PEAK AROUND TUESDAY...BRINGING NEAR
ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES...AND THEN SLOWLY
DIMINISH THROUGH THE REST OF THE WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

AVIATION...JELSEMA
REST...HUI





000
ATHW40 PHFO 200513
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0530 UTC MON APR 20 2015

BASED ON DATA THROUGH 0500 UTC APRIL 20 2015

TO THE NORTHWEST...THE END OF A DISSIPATING CLOUD BAND ASSOCIATED
WITH A FRONT EXTENDED ACROSS HAWAIIAN WATERS WITHIN 60 MILES OF THE
LINE FROM 30N 174W TO 27N 178W. THIS FEATURE SHIFTED NORTHWEST
SLOWLY.

TO THE SOUTHWEST...THIN HIGH CLOUD LAYERS FROM ACROSS THE DATELINE
PARTLY OBSCURED LOWER FEATURES WITHIN 150 MILES OF THE LINE FROM 18N
167W TO 15N 180.

TO THE SOUTH...LIGHT THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 09N TO 01N. LAYERED MIDDLE TO HIGH LAYERED DEBRIS CLOUDS FROM
THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES MOSTLY TO PARTLY
FROM 11N TO THE EQUATOR ACROSS MOST OF THE AREA...AND PARTLY FROM
13N TO 11N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...THOUGH INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. NORTHEAST OF THE CURVE FROM 30N 146W TO
29N 147W TO 19N 143W TO 20N 140W...THESE CLOUDS MERGED INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. THEY GENERALLY ROSE TO
HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER CUMULI AND HIGHER
LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED TOWARD THE WEST
SOUTHWEST AT AROUND 20 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF A
CLUMP OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST FROM OAHU TO THE BIG ISLAND. IN
MAUI COUNTY AND ON OAHU...THESE CLOUDS ALSO PASSED COMPLETELY OVER
THE MOUNTAINS IN PLACES...THUS REACHING SOME TYPICALLY CLEAR LEE
AREAS. AFTERNOON CUMULUS BUILDUPS WITH THEIR LAYERED DEBRIS CLOUDS
ALSO WERE IMPORTANT OVER LOWER TO MIDDLE WEST SLOPES OF THE BIG
ISLAND IN NORTH AND SOUTH KONA DISTRICTS. AREAS WITH THE LEAST CLOUD
COVER WERE LIMITED MAINLY TO NIIHAU...WEST KAUAI...THE IMMEDIATE
SOUTH COAST OF OAHU...THE IMMEDIATE SOUTH COAST OF MOLOKAI...WEST
SLOPES OF THE WEST MAUI MOUNTAINS...THE CENTRAL ISTHMUS ON MAUI...
THE SUMMIT AND SOUTH SLOPES OF HALEAKALA ON MAUI...THE WEST COAST OF
THE BIG ISLAND FROM KIHOLO BAY TO UPOLU POINT...THE KAU DESERT ON
THE BIG ISLAND...AND INTERIOR UPLANDS OF THE BIG ISLAND ABOVE
ELEVATIONS OF ABOUT 6000 FEET.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER
MOLOKAI...OVER THE INTERIOR OF LANAI...OVER THE WEST MAUI
MOUNTAINS...OVER EAST MAUI...OVER THE MOUNTAINS OF NORTH KOHALA
DISTRICT ON THE BIG ISLAND...OFFSHORE TO THE WEST-SOUTHWEST OF
LANAI...AND OFFSHORE TO THE EAST OF THE BIG ISLAND. ELSEWHERE...
RADAR DATA SHOWED ISOLATED SHOWERS AT MOST.

$$

RYSHKO






000
ATHW40 PHFO 200513
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0530 UTC MON APR 20 2015

BASED ON DATA THROUGH 0500 UTC APRIL 20 2015

TO THE NORTHWEST...THE END OF A DISSIPATING CLOUD BAND ASSOCIATED
WITH A FRONT EXTENDED ACROSS HAWAIIAN WATERS WITHIN 60 MILES OF THE
LINE FROM 30N 174W TO 27N 178W. THIS FEATURE SHIFTED NORTHWEST
SLOWLY.

TO THE SOUTHWEST...THIN HIGH CLOUD LAYERS FROM ACROSS THE DATELINE
PARTLY OBSCURED LOWER FEATURES WITHIN 150 MILES OF THE LINE FROM 18N
167W TO 15N 180.

TO THE SOUTH...LIGHT THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 09N TO 01N. LAYERED MIDDLE TO HIGH LAYERED DEBRIS CLOUDS FROM
THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES MOSTLY TO PARTLY
FROM 11N TO THE EQUATOR ACROSS MOST OF THE AREA...AND PARTLY FROM
13N TO 11N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...THOUGH INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. NORTHEAST OF THE CURVE FROM 30N 146W TO
29N 147W TO 19N 143W TO 20N 140W...THESE CLOUDS MERGED INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. THEY GENERALLY ROSE TO
HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER CUMULI AND HIGHER
LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED TOWARD THE WEST
SOUTHWEST AT AROUND 20 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF A
CLUMP OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST FROM OAHU TO THE BIG ISLAND. IN
MAUI COUNTY AND ON OAHU...THESE CLOUDS ALSO PASSED COMPLETELY OVER
THE MOUNTAINS IN PLACES...THUS REACHING SOME TYPICALLY CLEAR LEE
AREAS. AFTERNOON CUMULUS BUILDUPS WITH THEIR LAYERED DEBRIS CLOUDS
ALSO WERE IMPORTANT OVER LOWER TO MIDDLE WEST SLOPES OF THE BIG
ISLAND IN NORTH AND SOUTH KONA DISTRICTS. AREAS WITH THE LEAST CLOUD
COVER WERE LIMITED MAINLY TO NIIHAU...WEST KAUAI...THE IMMEDIATE
SOUTH COAST OF OAHU...THE IMMEDIATE SOUTH COAST OF MOLOKAI...WEST
SLOPES OF THE WEST MAUI MOUNTAINS...THE CENTRAL ISTHMUS ON MAUI...
THE SUMMIT AND SOUTH SLOPES OF HALEAKALA ON MAUI...THE WEST COAST OF
THE BIG ISLAND FROM KIHOLO BAY TO UPOLU POINT...THE KAU DESERT ON
THE BIG ISLAND...AND INTERIOR UPLANDS OF THE BIG ISLAND ABOVE
ELEVATIONS OF ABOUT 6000 FEET.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER
MOLOKAI...OVER THE INTERIOR OF LANAI...OVER THE WEST MAUI
MOUNTAINS...OVER EAST MAUI...OVER THE MOUNTAINS OF NORTH KOHALA
DISTRICT ON THE BIG ISLAND...OFFSHORE TO THE WEST-SOUTHWEST OF
LANAI...AND OFFSHORE TO THE EAST OF THE BIG ISLAND. ELSEWHERE...
RADAR DATA SHOWED ISOLATED SHOWERS AT MOST.

$$

RYSHKO





000
ATHW40 PHFO 200513
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0530 UTC MON APR 20 2015

BASED ON DATA THROUGH 0500 UTC APRIL 20 2015

TO THE NORTHWEST...THE END OF A DISSIPATING CLOUD BAND ASSOCIATED
WITH A FRONT EXTENDED ACROSS HAWAIIAN WATERS WITHIN 60 MILES OF THE
LINE FROM 30N 174W TO 27N 178W. THIS FEATURE SHIFTED NORTHWEST
SLOWLY.

TO THE SOUTHWEST...THIN HIGH CLOUD LAYERS FROM ACROSS THE DATELINE
PARTLY OBSCURED LOWER FEATURES WITHIN 150 MILES OF THE LINE FROM 18N
167W TO 15N 180.

TO THE SOUTH...LIGHT THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 09N TO 01N. LAYERED MIDDLE TO HIGH LAYERED DEBRIS CLOUDS FROM
THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES MOSTLY TO PARTLY
FROM 11N TO THE EQUATOR ACROSS MOST OF THE AREA...AND PARTLY FROM
13N TO 11N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...THOUGH INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. NORTHEAST OF THE CURVE FROM 30N 146W TO
29N 147W TO 19N 143W TO 20N 140W...THESE CLOUDS MERGED INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. THEY GENERALLY ROSE TO
HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER CUMULI AND HIGHER
LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED TOWARD THE WEST
SOUTHWEST AT AROUND 20 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF A
CLUMP OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST FROM OAHU TO THE BIG ISLAND. IN
MAUI COUNTY AND ON OAHU...THESE CLOUDS ALSO PASSED COMPLETELY OVER
THE MOUNTAINS IN PLACES...THUS REACHING SOME TYPICALLY CLEAR LEE
AREAS. AFTERNOON CUMULUS BUILDUPS WITH THEIR LAYERED DEBRIS CLOUDS
ALSO WERE IMPORTANT OVER LOWER TO MIDDLE WEST SLOPES OF THE BIG
ISLAND IN NORTH AND SOUTH KONA DISTRICTS. AREAS WITH THE LEAST CLOUD
COVER WERE LIMITED MAINLY TO NIIHAU...WEST KAUAI...THE IMMEDIATE
SOUTH COAST OF OAHU...THE IMMEDIATE SOUTH COAST OF MOLOKAI...WEST
SLOPES OF THE WEST MAUI MOUNTAINS...THE CENTRAL ISTHMUS ON MAUI...
THE SUMMIT AND SOUTH SLOPES OF HALEAKALA ON MAUI...THE WEST COAST OF
THE BIG ISLAND FROM KIHOLO BAY TO UPOLU POINT...THE KAU DESERT ON
THE BIG ISLAND...AND INTERIOR UPLANDS OF THE BIG ISLAND ABOVE
ELEVATIONS OF ABOUT 6000 FEET.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER
MOLOKAI...OVER THE INTERIOR OF LANAI...OVER THE WEST MAUI
MOUNTAINS...OVER EAST MAUI...OVER THE MOUNTAINS OF NORTH KOHALA
DISTRICT ON THE BIG ISLAND...OFFSHORE TO THE WEST-SOUTHWEST OF
LANAI...AND OFFSHORE TO THE EAST OF THE BIG ISLAND. ELSEWHERE...
RADAR DATA SHOWED ISOLATED SHOWERS AT MOST.

$$

RYSHKO






000
ATHW40 PHFO 200513
SIMHI

HAWAIIAN ISLANDS SATELLITE INTERPRETATION MESSAGE
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI
0530 UTC MON APR 20 2015

BASED ON DATA THROUGH 0500 UTC APRIL 20 2015

TO THE NORTHWEST...THE END OF A DISSIPATING CLOUD BAND ASSOCIATED
WITH A FRONT EXTENDED ACROSS HAWAIIAN WATERS WITHIN 60 MILES OF THE
LINE FROM 30N 174W TO 27N 178W. THIS FEATURE SHIFTED NORTHWEST
SLOWLY.

TO THE SOUTHWEST...THIN HIGH CLOUD LAYERS FROM ACROSS THE DATELINE
PARTLY OBSCURED LOWER FEATURES WITHIN 150 MILES OF THE LINE FROM 18N
167W TO 15N 180.

TO THE SOUTH...LIGHT THUNDERSTORM ACTIVITY CONTINUED IN THE ITCZ
FROM 09N TO 01N. LAYERED MIDDLE TO HIGH LAYERED DEBRIS CLOUDS FROM
THIS AND EARLIER CONVECTION OBSCURED LOWER FEATURES MOSTLY TO PARTLY
FROM 11N TO THE EQUATOR ACROSS MOST OF THE AREA...AND PARTLY FROM
13N TO 11N.

OTHERWISE...CLOUD COVER ACROSS HAWAIIAN WATERS CONSISTED MAINLY OF
LOOSE CLUMPS OF MARINE STRATOCUMULI...THOUGH INDIVIDUAL SMALL CUMULI
ALSO OCCURRED THROUGHOUT. NORTHEAST OF THE CURVE FROM 30N 146W TO
29N 147W TO 19N 143W TO 20N 140W...THESE CLOUDS MERGED INTO AREAS OF
NEARLY SOLID LOW TO MIDDLE STRATUS OVERCAST. THEY GENERALLY ROSE TO
HEIGHTS OF 8000 TO 12000 FEET...THOUGH TALLER CUMULI AND HIGHER
LAYERS APPROACHED 15000 FEET. THESE CLOUDS MOVED TOWARD THE WEST
SOUTHWEST AT AROUND 20 MILES AN HOUR.

ACROSS THE MAIN HAWAIIAN ISLANDS...CLOUD COVER CONSISTED MOSTLY OF A
CLUMP OF MARINE STRATOCUMULI MOVING ASHORE AND BANKING UP ALONG
SLOPES FACING NORTH THROUGH EAST FROM OAHU TO THE BIG ISLAND. IN
MAUI COUNTY AND ON OAHU...THESE CLOUDS ALSO PASSED COMPLETELY OVER
THE MOUNTAINS IN PLACES...THUS REACHING SOME TYPICALLY CLEAR LEE
AREAS. AFTERNOON CUMULUS BUILDUPS WITH THEIR LAYERED DEBRIS CLOUDS
ALSO WERE IMPORTANT OVER LOWER TO MIDDLE WEST SLOPES OF THE BIG
ISLAND IN NORTH AND SOUTH KONA DISTRICTS. AREAS WITH THE LEAST CLOUD
COVER WERE LIMITED MAINLY TO NIIHAU...WEST KAUAI...THE IMMEDIATE
SOUTH COAST OF OAHU...THE IMMEDIATE SOUTH COAST OF MOLOKAI...WEST
SLOPES OF THE WEST MAUI MOUNTAINS...THE CENTRAL ISTHMUS ON MAUI...
THE SUMMIT AND SOUTH SLOPES OF HALEAKALA ON MAUI...THE WEST COAST OF
THE BIG ISLAND FROM KIHOLO BAY TO UPOLU POINT...THE KAU DESERT ON
THE BIG ISLAND...AND INTERIOR UPLANDS OF THE BIG ISLAND ABOVE
ELEVATIONS OF ABOUT 6000 FEET.

RADAR DATA FROM NEAR THE ISLANDS SHOWED SCATTERED SHOWERS OVER
MOLOKAI...OVER THE INTERIOR OF LANAI...OVER THE WEST MAUI
MOUNTAINS...OVER EAST MAUI...OVER THE MOUNTAINS OF NORTH KOHALA
DISTRICT ON THE BIG ISLAND...OFFSHORE TO THE WEST-SOUTHWEST OF
LANAI...AND OFFSHORE TO THE EAST OF THE BIG ISLAND. ELSEWHERE...
RADAR DATA SHOWED ISOLATED SHOWERS AT MOST.

$$

RYSHKO





000
FXHW60 PHFO 200146 CCA
AFDHFO

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

CORRECTED FIRST PARAGRAPH OF MARINE SECTION

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT UNTIL TUESDAY MORNING FOR
ALL HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED
WITH STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE
EXCEPTION FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A
GALE WARNING HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO
THE SE OVER KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS
OVER MAUI AND THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE
SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 200146 CCA
AFDHFO

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

CORRECTED FIRST PARAGRAPH OF MARINE SECTION

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT UNTIL TUESDAY MORNING FOR
ALL HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED
WITH STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE
EXCEPTION FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A
GALE WARNING HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO
THE SE OVER KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS
OVER MAUI AND THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE
SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 200146 CCA
AFDHFO

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

CORRECTED FIRST PARAGRAPH OF MARINE SECTION

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT UNTIL TUESDAY MORNING FOR
ALL HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED
WITH STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE
EXCEPTION FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A
GALE WARNING HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO
THE SE OVER KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS
OVER MAUI AND THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE
SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 200146 CCA
AFDHFO

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

CORRECTED FIRST PARAGRAPH OF MARINE SECTION

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT UNTIL TUESDAY MORNING FOR
ALL HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED
WITH STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE
EXCEPTION FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A
GALE WARNING HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO
THE SE OVER KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS
OVER MAUI AND THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE
SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 200146 CCA
AFDHFO

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

CORRECTED FIRST PARAGRAPH OF MARINE SECTION

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT UNTIL TUESDAY MORNING FOR
ALL HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED
WITH STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE
EXCEPTION FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A
GALE WARNING HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO
THE SE OVER KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS
OVER MAUI AND THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE
SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 200146 CCA
AFDHFO

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

CORRECTED FIRST PARAGRAPH OF MARINE SECTION

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT UNTIL TUESDAY MORNING FOR
ALL HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED
WITH STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE
EXCEPTION FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A
GALE WARNING HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO
THE SE OVER KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS
OVER MAUI AND THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE
SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 200130
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE EXCEPTION
FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A GALE WARNING
HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO THE SE OVER
KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS OVER MAUI AND
THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 200130
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE EXCEPTION
FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A GALE WARNING
HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO THE SE OVER
KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS OVER MAUI AND
THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 200130
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE EXCEPTION
FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A GALE WARNING
HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO THE SE OVER
KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS OVER MAUI AND
THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 200130
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE EXCEPTION
FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A GALE WARNING
HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO THE SE OVER
KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS OVER MAUI AND
THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 200130
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE EXCEPTION
FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A GALE WARNING
HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO THE SE OVER
KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS OVER MAUI AND
THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 200130
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING STRONG TRADE
WINDS THROUGH TUESDAY. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. BY
THE MIDDLE OF THE WEEK...A LOW DEVELOPING NORTHWEST OF THE ISLANDS
WILL TURN WINDS TO THE SOUTHEAST AND WEAKEN THEM...ESPECIALLY OVER
KAUAI AND OAHU. THE LOW MAY COME CLOSE ENOUGH TO THE AREA TO BRING
INCREASED SHOWERS FROM WEDNESDAY ONWARD...MAINLY TO KAUAI. MAUI AND
THE BIG ISLAND ARE EXPECTED TO REMAIN UNDER A TRADE WIND FLOW
THROUGHOUT THE WEEK.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. AS DISCUSSED
EARLIER...THE HIGH TO THE NE IS TRACKING SW AND DISSIPATING WHILE
THE HIGH TO THE NW IS TRACKING E AND STRENGTHENING. MID AND UPPER
LEVEL ANALYSIS INDICATES A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...
WITH AFTERNOON SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE
INVERSION IS BETWEEN 6 AND 8 KFT...WITH PWAT VALUES LESS THAN AN
INCH. DESPITE THE STABLE ATMOSPHERE...MOISTURE EMBEDDED IN THE
TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW SHOWERS OVER THE OPEN
OCEAN...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR TONIGHT...THE
EXPECTATION IS THAT CLOUDS AND SHOWERS WILL INCREASE DUE TO CLOUD
TOP COOLING...WHILE A CLUSTER OF SHOWERY LOW CLOUDS CURRENTLY
UPSTREAM OF MAUI AND THE BIG ISLAND HELPS TO FUEL SHOWERS AS IT
SPREADS ACROSS THE CHAIN FROM THE E.

THE HIGH TO THE NW WILL TRACK STEADILY E AND STRENGTHEN OVER THE
NEXT 48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE ISLANDS ON
TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...THE HIGH WILL
SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR TRADE WINDS TO
INCREASE A NOTCH THROUGH TONIGHT...THEN REMAINING WINDY THROUGH
TUESDAY...WITH WINDS EXPECTED TO EASE SLIGHTLY AND VEER AROUND MID
WEEK. A NEARBY MID-LEVEL RIDGE WILL MAINTAIN THE STABLE ATMOSPHERE...
BUT WILL STILL ALLOW TRADE SHOWERS TO CONTINUE. IN THE SHORT-TERM...
WINDS MAY REACH ADVISORY LEVEL IN SOME WIND-PRONE AREAS ACROSS THE
ISLANDS UNDER THE STABLE AIR MASS...BUT HAVE ELECTED NOT TO ISSUE AN
ADVISORY AT THIS TIME.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE REMAIN SOME SUBTLE DIFFERENCES WITH RESPECT TO THE
ANTICIPATED DEVELOPMENT AND EVOLUTION OF A VIGOROUS KONA LOW THAT
DEVELOPS NW OF THE ISLANDS TUESDAY/WEDNESDAY AND THEN LINGERS FOR AT
LEAST SEVERAL DAYS. MODELS HAVE BEEN CONSISTENT IN DEVELOPING THIS
DEEP LAYER CUT-OFF LOW...IT/S ASSOCIATED SURFACE LOW...AND A
SIGNIFICANT CONVERGENCE BAND E OF THE LOW. HOWEVER...AS CAN BE
EXPECTED WITH THIS KIND OF FEATURE...FORECAST MODELS HAVE WAVERED AS
TO THE FINER-SCALE DETAILS...WHICH IN THIS CASE HAS SIGNIFICANT
IMPLICATIONS FOR ISLAND WEATHER.

THE GFS BRINGS AN INCREASE IN INSTABILITY AND MOISTURE ASSOCIATED
WITH THE LOW OVER THE W PORTION OF THE ISLAND CHAIN AROUND
MID-WEEK...AND THEN KEEPS THIS PATTERN IN PLACE INTO NEXT WEEKEND.
JUST E OF THE ISLANDS A STRONG MID LEVEL RIDGE WILL KEEP STABLE
WEATHER IN PLACE OVER THE BIG ISLAND AND MAUI THROUGH THE PERIOD.
IN THE GFS...THE SURFACE LOW MOVES CLOSE ENOUGH TO VEER WINDS TO THE
SE FROM TUESDAY INTO THE WEEKEND...ESPECIALLY OVER THE W END OF
THE ISLAND CHAIN. MEANWHILE...12Z ECMWF GUIDANCE HAS TRENDED A
LITTLE CLOSER TO THE GFS WITH VEERING WINDS NEAR KAUAI. THE 12Z CMC
ALSO VEERS WINDS...BUT KEEPS MOST OF THE DYNAMICS ASSOCIATED WITH
THE LOW OUT TO THE W. SO THIS FORECAST PACKAGE CONTAINS WINDS THAT
ARE A LITTLE MORE SE THAN PREVIOUSLY FORECAST...ESPECIALLY NEAR
KAUAI. MODELS SUGGEST THAT PORTIONS OF THE ISLAND CHAIN COULD
BE AFFECTED BY CONVERGENCE BANDS E OF THE LOW...AS SHORT WAVE LOBES
OF VORTICITY ROTATE AROUND THE MAIN LOW...BUT THERE IS LESS
CONFIDENCE IN THIS OCCURRING. PRECIP SHOULD CONTINUE TO FAVOR
WINDWARD AREAS FOR MOST OF THE WEEK...BUT AN INCREASINGLY SOUTHERLY
COMPONENT TO THE WINDS COULD BRING LEEWARD RAINFALL...ESPECIALLY TO
KAUAI AND OAHU. FOR NOW HAVE NOT MADE SIGNIFICANT CHANGES TO POP
GRIDS WHICH FEATURE HIGHER POPS OVER WINDWARD TERRAIN...AS
CONFIDENCE IN THAT ASPECT OF THE FORECAST REMAINS QUITE LOW.

&&

.AVIATION...
LOW CLOUDS AND SHOWERS MOVING OVER THE ISLANDS FROM THE E WILL BRING
MVFR VIS/CIG...MAINLY TO WINDWARD SLOPES AND COASTS...WHICH MAY
BECOME SUFFICIENTLY WIDESPREAD TO WARRANT AIRMET SIERRA FOR MTN
OBSCURATION OVERNIGHT. AIRMET TANGO...WITH ISOL SEVERE TURB...
REMAINS POSTED FOR LOW LEVEL TURBULENCE TO THE LEE OF THE TERRAIN ON
ALL ISLANDS...AND WILL CONTINUE FOR THE FORESEEABLE FUTURE. A SMALL
PLANE REPORTED MODERATE TO SEVERE TURB NEAR MAUI/S MCGREGOR POINT
EARLIER THIS AFTERNOON. WHILE VFR CONDITIONS WILL PREVAIL AT THE
TERMINALS...PERIODS OF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT
WINDWARD LOCATIONS...MOST NOTABLY PHTO.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO STRONG TRADE WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. THE EXCEPTION
FOR THE TIME BEING IS THE ALENUIHAHA CHANNEL...WHERE A GALE WARNING
HAS BEEN ISSUED. ALTHOUGH WINDS MAY WEAKEN AND VEER TO THE SE OVER
KAUAI AND OAHU WATERS AFTER TUESDAY...STRONG E WINDS OVER MAUI AND
THE BIG ISLAND WILL LIKELY WARRANT AN EXTENSION OF THE SCA.

THE STRONG TRADE WINDS WILL ALSO BRING HIGH SURF TO E FACING SHORES
THE NEXT FEW DAYS...WITH SURF RATHER ROUGH AND CHOPPY. LATE MORNING
SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET ALONG E FACING
SHORES OF THE BIG ISLAND...WITH UP TO 8 FEET REPORTED ON KAUAI AND
OAHU...AND A HIGH SURF ADVISORY WAS ISSUED EARLIER THIS AFTERNOON.
THE ADVISORY CURRENTLY RUNS THROUGH TUESDAY NIGHT...BUT MAY NEED TO
BE EXTENDED...ESPECIALLY FOR MAUI AND THE BIG ISLAND.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...
WITH THE CDIP/PACIOOS BUOY NEAR LANAI DETECTING FORERUNNERS IN THE
16-22 SECOND BANDS TODAY. THIS SWELL WILL PEAK AROUND TUESDAY...
AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH NEAR
ADVISORY LEVEL SURF ALONG S FACING SHORES DURING THE PEAK OF THE
SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING UNTIL 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 192208 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1210 PM HST SUN APR 19 2015

.UPDATE...
LATE MORNING SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET
ALONG E FACING SHORES OF THE BIG ISLAND...AND 8 FEET WAS REPORTED ON
KAUAI AND OAHU. THUS A HIGH SURF ADVISORY HAS BEEN ISSUED FOR
EAST FACING SHORES OF ISLANDS EXPOSED TO THE ROUGH WIND WAVES. HAVE
ALSO MODIFIED THE AFTERNOON FORECAST TO INCREASE SKY COVER IN SOME
AREAS INCLUDING N AND CENTRAL OAHU...AND TO INCREASE POPS AND SKY
COVER OVER WINDWARD MAUI AS A CLUSTER OF SHOWER-BEARING CLOUDS LIES
IMMEDIATELY UPSTREAM.

&&

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING WINDY CONDITIONS
THE NEXT COUPLE OF DAYS...WITH BREEZY CONDITIONS PREVAILING FOR THE
REMAINDER OF THE WEEK. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. A
DISTURBANCE NORTHWEST OF THE ISLANDS MAY TURN WINDS TOWARD THE
SOUTHEAST LATER IN THE WEEK...POTENTIALLY BRINGING INCREASED SHOWERS
TO KAUAI.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. THE HIGH TO
THE NE IS TRACKING SW AND WEAKENING WHILE THE HIGH TO THE NW IS
TRACKING E AND STRENGTHENING. MID AND UPPER LEVEL ANALYSIS INDICATES
A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...WITH EARLY MORNING
SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE INVERSION IS
BETWEEN 6 AND 8 KFT. DESPITE THE STABLE ATMOSPHERE...MOISTURE
EMBEDDED IN THE TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW OPEN OCEAN
SHOWERS...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR THE REMAINDER OF
TODAY...THE EXPECTATION IS THAT CLOUDS AND SHOWERS WILL DIMINISH ON
KAUAI AND OAHU AS UPSTREAM MOISTURE WANES...BUT A CLUSTER OF BROKEN
LOW CLOUDS UPSTREAM OF MAUI AND THE BIG ISLAND WILL LIKELY KEEP
WINDWARD AREAS OF THOSE ISLANDS A LITTLE CLOUDIER AND WETTER
THROUGH THE DAY. SOME OF THIS MOISTURE IS EXPECTED TO FUEL TRADE
SHOWERS OVER KAUAI AND OAHU TONIGHT.

THE HIGH TO THE NW WILL TRACK STEADILY TOWARD THE E AND STRENGTHEN
OVER THE NEXT 24-48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE
ISLANDS ON TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...
THE HIGH WILL SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR
TRADE WINDS TO INCREASE A NOTCH TODAY AND TONIGHT...REMAINING WINDY
THROUGH TUESDAY...WITH WINDS EASING JUST A LITTLE LATER IN THE WEEK.
IN THE SHORT-TERM...THE WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE ARE SOME DIFFERENCES WITH RESPECT TO OTHER
FEATURES. ALTHOUGH THE MODEL SOLUTIONS ARE A LITTLE MORE CLOSELY
ALIGNED WITH RESPECT TO THE ANTICIPATED DEVELOPMENT AND EVOLUTION OF
A CUT-OFF LOW TO THE NW OF THE ISLANDS TUESDAY/WEDNESDAY...ENOUGH OF
A DIFFERENCE EXISTS BETWEEN THE GFS AND ECMWF TO HAVE IMPLICATIONS
FOR HAWAIIAN WEATHER. THE GFS BRINGS A MODERATE INSTABILITY AND
MOISTURE INCREASE ASSOCIATED WITH THE LOW OVER THE ISLANDS...AROUND
MID-WEEK...AND ALSO BRINGS IT CLOSE ENOUGH TO VEER WINDS TO SSE FROM
TUESDAY INTO THE WEEKEND. MEANWHILE...THE NEWLY-ARRIVED ECMWF
GUIDANCE HAS TRENDED A LITTLE CLOSER TO THE GFS. ONGOING FORECAST
FAVORS THE OLDER ECMWF SOLUTION...WHICH ESSENTIALLY KEEPS A FAIRLY
STABLE AND BREEZY TRADE WIND FLOW IN PLACE THROUGH THE WEEK. WILL
LIKELY NUDGE THE WIND FORECAST A LITTLE MORE TOWARD THE SE FOR THE
LATTER PART OF THE WEEK IN DEFERENCE TO THIS. THE MID LEVEL RIDGE
CURRENTLY OVER THE ISLANDS WILL SHIFT SLIGHTLY E THIS WEEK...KEEPING
FAIRLY STABLE CONDITIONS IN PLACE NEAR THE BIG ISLAND...WITH KAUAI
WEATHER POTENTIALLY INFLUENCED BY THE LOW AFTER MID-WEEK.

&&

.AVIATION...
A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS THAT MOVED ASHORE IN
MANY AREAS THIS MORNING HAS CLEARED SUCH THAT AIRMET SIERRA FOR MTN
OBSCURATION WAS CANCELLED...BUT ENOUGH LINGERS NEAR WINDWARD BIG
ISLAND TO SUPPORT ITS CONTINUATION...AT LEAST FOR NOW. AIRMET TANGO
FOR LO LVL TURB BLO 080 WILL CONT FOR THE FORESEEABLE FUTURE FOR
ALL ISLANDS. WHILE VFR CONDITIONS WILL PREVAIL AT THE TERMINALS...
BRIEF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT WINDWARD LOCATIONS...
MOST NOTABLY PHTO/

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. WINDS ARE
EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE FORCE WINDS
EXPECTED IN CHANNELS AROUND MAUI AND THE BIG ISLAND. IN FACT...
LATEST GUIDANCE FROM HI-RES MODELS INDICATES GALE FORCE WINDS IN THE
ALENUIHAHA CHANNEL FROM TONIGHT INTO MONDAY NIGHT. THUS THE MARINE
FORECAST HAS BEEN MODIFIED TO UPGRADE THE SCA TO A GALE WARNING...
BEGINNING LATER TODAY...FOR THIS CHANNEL. ALTHOUGH WINDS MAY EASE
AFTER TUESDAY...ONLY A SLIGHT DOWNTREND IS EXPECTED...AND THE SCA
WILL LIKELY NEED TO BE EXTENDED.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG E FACING SHORES THE NEXT FEW DAYS...WITH RATHER ROUGH AND
CHOPPY SURF UNDER THE WINDS. LATEST NEAR SHORE BUOY OBSERVATIONS
INDICATE 8-9 FOOT SEAS WITH A DOMINANT PERIOD OF 8-9 SECONDS...WHICH
IS VERY CLOSE TO THE VALUES WE NORMALLY LOOK FOR WHEN ISSUING HIGH
SURF ADVISORIES FOR TRADE WIND SWELLS. WILL LIKELY BE ISSUING AN
ADVISORY AS WAVE WATCH ANTICIPATES A SLIGHT INCREASE IN WAVE
HEIGHTS.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...AND
THE CDIP/PACIOOS BUOY NEAR LANAI HAS BEEN DETECTING FORERUNNERS IN
THE 20-SECOND BAND ALREADY THIS MORNING. THIS SWELL WILL PEAK AROUND
TUESDAY...AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE
WEEK...WITH NEAR ADVISORY LEVEL SURF ALONG S FACING SHORES DURING
THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FROM 4 PM TODAY TO 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 192208 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1210 PM HST SUN APR 19 2015

.UPDATE...
LATE MORNING SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET
ALONG E FACING SHORES OF THE BIG ISLAND...AND 8 FEET WAS REPORTED ON
KAUAI AND OAHU. THUS A HIGH SURF ADVISORY HAS BEEN ISSUED FOR
EAST FACING SHORES OF ISLANDS EXPOSED TO THE ROUGH WIND WAVES. HAVE
ALSO MODIFIED THE AFTERNOON FORECAST TO INCREASE SKY COVER IN SOME
AREAS INCLUDING N AND CENTRAL OAHU...AND TO INCREASE POPS AND SKY
COVER OVER WINDWARD MAUI AS A CLUSTER OF SHOWER-BEARING CLOUDS LIES
IMMEDIATELY UPSTREAM.

&&

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING WINDY CONDITIONS
THE NEXT COUPLE OF DAYS...WITH BREEZY CONDITIONS PREVAILING FOR THE
REMAINDER OF THE WEEK. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. A
DISTURBANCE NORTHWEST OF THE ISLANDS MAY TURN WINDS TOWARD THE
SOUTHEAST LATER IN THE WEEK...POTENTIALLY BRINGING INCREASED SHOWERS
TO KAUAI.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. THE HIGH TO
THE NE IS TRACKING SW AND WEAKENING WHILE THE HIGH TO THE NW IS
TRACKING E AND STRENGTHENING. MID AND UPPER LEVEL ANALYSIS INDICATES
A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...WITH EARLY MORNING
SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE INVERSION IS
BETWEEN 6 AND 8 KFT. DESPITE THE STABLE ATMOSPHERE...MOISTURE
EMBEDDED IN THE TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW OPEN OCEAN
SHOWERS...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR THE REMAINDER OF
TODAY...THE EXPECTATION IS THAT CLOUDS AND SHOWERS WILL DIMINISH ON
KAUAI AND OAHU AS UPSTREAM MOISTURE WANES...BUT A CLUSTER OF BROKEN
LOW CLOUDS UPSTREAM OF MAUI AND THE BIG ISLAND WILL LIKELY KEEP
WINDWARD AREAS OF THOSE ISLANDS A LITTLE CLOUDIER AND WETTER
THROUGH THE DAY. SOME OF THIS MOISTURE IS EXPECTED TO FUEL TRADE
SHOWERS OVER KAUAI AND OAHU TONIGHT.

THE HIGH TO THE NW WILL TRACK STEADILY TOWARD THE E AND STRENGTHEN
OVER THE NEXT 24-48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE
ISLANDS ON TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...
THE HIGH WILL SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR
TRADE WINDS TO INCREASE A NOTCH TODAY AND TONIGHT...REMAINING WINDY
THROUGH TUESDAY...WITH WINDS EASING JUST A LITTLE LATER IN THE WEEK.
IN THE SHORT-TERM...THE WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE ARE SOME DIFFERENCES WITH RESPECT TO OTHER
FEATURES. ALTHOUGH THE MODEL SOLUTIONS ARE A LITTLE MORE CLOSELY
ALIGNED WITH RESPECT TO THE ANTICIPATED DEVELOPMENT AND EVOLUTION OF
A CUT-OFF LOW TO THE NW OF THE ISLANDS TUESDAY/WEDNESDAY...ENOUGH OF
A DIFFERENCE EXISTS BETWEEN THE GFS AND ECMWF TO HAVE IMPLICATIONS
FOR HAWAIIAN WEATHER. THE GFS BRINGS A MODERATE INSTABILITY AND
MOISTURE INCREASE ASSOCIATED WITH THE LOW OVER THE ISLANDS...AROUND
MID-WEEK...AND ALSO BRINGS IT CLOSE ENOUGH TO VEER WINDS TO SSE FROM
TUESDAY INTO THE WEEKEND. MEANWHILE...THE NEWLY-ARRIVED ECMWF
GUIDANCE HAS TRENDED A LITTLE CLOSER TO THE GFS. ONGOING FORECAST
FAVORS THE OLDER ECMWF SOLUTION...WHICH ESSENTIALLY KEEPS A FAIRLY
STABLE AND BREEZY TRADE WIND FLOW IN PLACE THROUGH THE WEEK. WILL
LIKELY NUDGE THE WIND FORECAST A LITTLE MORE TOWARD THE SE FOR THE
LATTER PART OF THE WEEK IN DEFERENCE TO THIS. THE MID LEVEL RIDGE
CURRENTLY OVER THE ISLANDS WILL SHIFT SLIGHTLY E THIS WEEK...KEEPING
FAIRLY STABLE CONDITIONS IN PLACE NEAR THE BIG ISLAND...WITH KAUAI
WEATHER POTENTIALLY INFLUENCED BY THE LOW AFTER MID-WEEK.

&&

.AVIATION...
A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS THAT MOVED ASHORE IN
MANY AREAS THIS MORNING HAS CLEARED SUCH THAT AIRMET SIERRA FOR MTN
OBSCURATION WAS CANCELLED...BUT ENOUGH LINGERS NEAR WINDWARD BIG
ISLAND TO SUPPORT ITS CONTINUATION...AT LEAST FOR NOW. AIRMET TANGO
FOR LO LVL TURB BLO 080 WILL CONT FOR THE FORESEEABLE FUTURE FOR
ALL ISLANDS. WHILE VFR CONDITIONS WILL PREVAIL AT THE TERMINALS...
BRIEF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT WINDWARD LOCATIONS...
MOST NOTABLY PHTO/

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. WINDS ARE
EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE FORCE WINDS
EXPECTED IN CHANNELS AROUND MAUI AND THE BIG ISLAND. IN FACT...
LATEST GUIDANCE FROM HI-RES MODELS INDICATES GALE FORCE WINDS IN THE
ALENUIHAHA CHANNEL FROM TONIGHT INTO MONDAY NIGHT. THUS THE MARINE
FORECAST HAS BEEN MODIFIED TO UPGRADE THE SCA TO A GALE WARNING...
BEGINNING LATER TODAY...FOR THIS CHANNEL. ALTHOUGH WINDS MAY EASE
AFTER TUESDAY...ONLY A SLIGHT DOWNTREND IS EXPECTED...AND THE SCA
WILL LIKELY NEED TO BE EXTENDED.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG E FACING SHORES THE NEXT FEW DAYS...WITH RATHER ROUGH AND
CHOPPY SURF UNDER THE WINDS. LATEST NEAR SHORE BUOY OBSERVATIONS
INDICATE 8-9 FOOT SEAS WITH A DOMINANT PERIOD OF 8-9 SECONDS...WHICH
IS VERY CLOSE TO THE VALUES WE NORMALLY LOOK FOR WHEN ISSUING HIGH
SURF ADVISORIES FOR TRADE WIND SWELLS. WILL LIKELY BE ISSUING AN
ADVISORY AS WAVE WATCH ANTICIPATES A SLIGHT INCREASE IN WAVE
HEIGHTS.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...AND
THE CDIP/PACIOOS BUOY NEAR LANAI HAS BEEN DETECTING FORERUNNERS IN
THE 20-SECOND BAND ALREADY THIS MORNING. THIS SWELL WILL PEAK AROUND
TUESDAY...AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE
WEEK...WITH NEAR ADVISORY LEVEL SURF ALONG S FACING SHORES DURING
THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FROM 4 PM TODAY TO 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 192208 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1210 PM HST SUN APR 19 2015

.UPDATE...
LATE MORNING SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET
ALONG E FACING SHORES OF THE BIG ISLAND...AND 8 FEET WAS REPORTED ON
KAUAI AND OAHU. THUS A HIGH SURF ADVISORY HAS BEEN ISSUED FOR
EAST FACING SHORES OF ISLANDS EXPOSED TO THE ROUGH WIND WAVES. HAVE
ALSO MODIFIED THE AFTERNOON FORECAST TO INCREASE SKY COVER IN SOME
AREAS INCLUDING N AND CENTRAL OAHU...AND TO INCREASE POPS AND SKY
COVER OVER WINDWARD MAUI AS A CLUSTER OF SHOWER-BEARING CLOUDS LIES
IMMEDIATELY UPSTREAM.

&&

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING WINDY CONDITIONS
THE NEXT COUPLE OF DAYS...WITH BREEZY CONDITIONS PREVAILING FOR THE
REMAINDER OF THE WEEK. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. A
DISTURBANCE NORTHWEST OF THE ISLANDS MAY TURN WINDS TOWARD THE
SOUTHEAST LATER IN THE WEEK...POTENTIALLY BRINGING INCREASED SHOWERS
TO KAUAI.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. THE HIGH TO
THE NE IS TRACKING SW AND WEAKENING WHILE THE HIGH TO THE NW IS
TRACKING E AND STRENGTHENING. MID AND UPPER LEVEL ANALYSIS INDICATES
A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...WITH EARLY MORNING
SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE INVERSION IS
BETWEEN 6 AND 8 KFT. DESPITE THE STABLE ATMOSPHERE...MOISTURE
EMBEDDED IN THE TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW OPEN OCEAN
SHOWERS...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR THE REMAINDER OF
TODAY...THE EXPECTATION IS THAT CLOUDS AND SHOWERS WILL DIMINISH ON
KAUAI AND OAHU AS UPSTREAM MOISTURE WANES...BUT A CLUSTER OF BROKEN
LOW CLOUDS UPSTREAM OF MAUI AND THE BIG ISLAND WILL LIKELY KEEP
WINDWARD AREAS OF THOSE ISLANDS A LITTLE CLOUDIER AND WETTER
THROUGH THE DAY. SOME OF THIS MOISTURE IS EXPECTED TO FUEL TRADE
SHOWERS OVER KAUAI AND OAHU TONIGHT.

THE HIGH TO THE NW WILL TRACK STEADILY TOWARD THE E AND STRENGTHEN
OVER THE NEXT 24-48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE
ISLANDS ON TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...
THE HIGH WILL SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR
TRADE WINDS TO INCREASE A NOTCH TODAY AND TONIGHT...REMAINING WINDY
THROUGH TUESDAY...WITH WINDS EASING JUST A LITTLE LATER IN THE WEEK.
IN THE SHORT-TERM...THE WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE ARE SOME DIFFERENCES WITH RESPECT TO OTHER
FEATURES. ALTHOUGH THE MODEL SOLUTIONS ARE A LITTLE MORE CLOSELY
ALIGNED WITH RESPECT TO THE ANTICIPATED DEVELOPMENT AND EVOLUTION OF
A CUT-OFF LOW TO THE NW OF THE ISLANDS TUESDAY/WEDNESDAY...ENOUGH OF
A DIFFERENCE EXISTS BETWEEN THE GFS AND ECMWF TO HAVE IMPLICATIONS
FOR HAWAIIAN WEATHER. THE GFS BRINGS A MODERATE INSTABILITY AND
MOISTURE INCREASE ASSOCIATED WITH THE LOW OVER THE ISLANDS...AROUND
MID-WEEK...AND ALSO BRINGS IT CLOSE ENOUGH TO VEER WINDS TO SSE FROM
TUESDAY INTO THE WEEKEND. MEANWHILE...THE NEWLY-ARRIVED ECMWF
GUIDANCE HAS TRENDED A LITTLE CLOSER TO THE GFS. ONGOING FORECAST
FAVORS THE OLDER ECMWF SOLUTION...WHICH ESSENTIALLY KEEPS A FAIRLY
STABLE AND BREEZY TRADE WIND FLOW IN PLACE THROUGH THE WEEK. WILL
LIKELY NUDGE THE WIND FORECAST A LITTLE MORE TOWARD THE SE FOR THE
LATTER PART OF THE WEEK IN DEFERENCE TO THIS. THE MID LEVEL RIDGE
CURRENTLY OVER THE ISLANDS WILL SHIFT SLIGHTLY E THIS WEEK...KEEPING
FAIRLY STABLE CONDITIONS IN PLACE NEAR THE BIG ISLAND...WITH KAUAI
WEATHER POTENTIALLY INFLUENCED BY THE LOW AFTER MID-WEEK.

&&

.AVIATION...
A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS THAT MOVED ASHORE IN
MANY AREAS THIS MORNING HAS CLEARED SUCH THAT AIRMET SIERRA FOR MTN
OBSCURATION WAS CANCELLED...BUT ENOUGH LINGERS NEAR WINDWARD BIG
ISLAND TO SUPPORT ITS CONTINUATION...AT LEAST FOR NOW. AIRMET TANGO
FOR LO LVL TURB BLO 080 WILL CONT FOR THE FORESEEABLE FUTURE FOR
ALL ISLANDS. WHILE VFR CONDITIONS WILL PREVAIL AT THE TERMINALS...
BRIEF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT WINDWARD LOCATIONS...
MOST NOTABLY PHTO/

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. WINDS ARE
EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE FORCE WINDS
EXPECTED IN CHANNELS AROUND MAUI AND THE BIG ISLAND. IN FACT...
LATEST GUIDANCE FROM HI-RES MODELS INDICATES GALE FORCE WINDS IN THE
ALENUIHAHA CHANNEL FROM TONIGHT INTO MONDAY NIGHT. THUS THE MARINE
FORECAST HAS BEEN MODIFIED TO UPGRADE THE SCA TO A GALE WARNING...
BEGINNING LATER TODAY...FOR THIS CHANNEL. ALTHOUGH WINDS MAY EASE
AFTER TUESDAY...ONLY A SLIGHT DOWNTREND IS EXPECTED...AND THE SCA
WILL LIKELY NEED TO BE EXTENDED.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG E FACING SHORES THE NEXT FEW DAYS...WITH RATHER ROUGH AND
CHOPPY SURF UNDER THE WINDS. LATEST NEAR SHORE BUOY OBSERVATIONS
INDICATE 8-9 FOOT SEAS WITH A DOMINANT PERIOD OF 8-9 SECONDS...WHICH
IS VERY CLOSE TO THE VALUES WE NORMALLY LOOK FOR WHEN ISSUING HIGH
SURF ADVISORIES FOR TRADE WIND SWELLS. WILL LIKELY BE ISSUING AN
ADVISORY AS WAVE WATCH ANTICIPATES A SLIGHT INCREASE IN WAVE
HEIGHTS.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...AND
THE CDIP/PACIOOS BUOY NEAR LANAI HAS BEEN DETECTING FORERUNNERS IN
THE 20-SECOND BAND ALREADY THIS MORNING. THIS SWELL WILL PEAK AROUND
TUESDAY...AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE
WEEK...WITH NEAR ADVISORY LEVEL SURF ALONG S FACING SHORES DURING
THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FROM 4 PM TODAY TO 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD






000
FXHW60 PHFO 192208 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1210 PM HST SUN APR 19 2015

.UPDATE...
LATE MORNING SURF OBSERVATIONS INDICATED SURF AS HIGH AS 10 FEET
ALONG E FACING SHORES OF THE BIG ISLAND...AND 8 FEET WAS REPORTED ON
KAUAI AND OAHU. THUS A HIGH SURF ADVISORY HAS BEEN ISSUED FOR
EAST FACING SHORES OF ISLANDS EXPOSED TO THE ROUGH WIND WAVES. HAVE
ALSO MODIFIED THE AFTERNOON FORECAST TO INCREASE SKY COVER IN SOME
AREAS INCLUDING N AND CENTRAL OAHU...AND TO INCREASE POPS AND SKY
COVER OVER WINDWARD MAUI AS A CLUSTER OF SHOWER-BEARING CLOUDS LIES
IMMEDIATELY UPSTREAM.

&&

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING WINDY CONDITIONS
THE NEXT COUPLE OF DAYS...WITH BREEZY CONDITIONS PREVAILING FOR THE
REMAINDER OF THE WEEK. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. A
DISTURBANCE NORTHWEST OF THE ISLANDS MAY TURN WINDS TOWARD THE
SOUTHEAST LATER IN THE WEEK...POTENTIALLY BRINGING INCREASED SHOWERS
TO KAUAI.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. THE HIGH TO
THE NE IS TRACKING SW AND WEAKENING WHILE THE HIGH TO THE NW IS
TRACKING E AND STRENGTHENING. MID AND UPPER LEVEL ANALYSIS INDICATES
A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...WITH EARLY MORNING
SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE INVERSION IS
BETWEEN 6 AND 8 KFT. DESPITE THE STABLE ATMOSPHERE...MOISTURE
EMBEDDED IN THE TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW OPEN OCEAN
SHOWERS...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR THE REMAINDER OF
TODAY...THE EXPECTATION IS THAT CLOUDS AND SHOWERS WILL DIMINISH ON
KAUAI AND OAHU AS UPSTREAM MOISTURE WANES...BUT A CLUSTER OF BROKEN
LOW CLOUDS UPSTREAM OF MAUI AND THE BIG ISLAND WILL LIKELY KEEP
WINDWARD AREAS OF THOSE ISLANDS A LITTLE CLOUDIER AND WETTER
THROUGH THE DAY. SOME OF THIS MOISTURE IS EXPECTED TO FUEL TRADE
SHOWERS OVER KAUAI AND OAHU TONIGHT.

THE HIGH TO THE NW WILL TRACK STEADILY TOWARD THE E AND STRENGTHEN
OVER THE NEXT 24-48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE
ISLANDS ON TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...
THE HIGH WILL SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR
TRADE WINDS TO INCREASE A NOTCH TODAY AND TONIGHT...REMAINING WINDY
THROUGH TUESDAY...WITH WINDS EASING JUST A LITTLE LATER IN THE WEEK.
IN THE SHORT-TERM...THE WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE ARE SOME DIFFERENCES WITH RESPECT TO OTHER
FEATURES. ALTHOUGH THE MODEL SOLUTIONS ARE A LITTLE MORE CLOSELY
ALIGNED WITH RESPECT TO THE ANTICIPATED DEVELOPMENT AND EVOLUTION OF
A CUT-OFF LOW TO THE NW OF THE ISLANDS TUESDAY/WEDNESDAY...ENOUGH OF
A DIFFERENCE EXISTS BETWEEN THE GFS AND ECMWF TO HAVE IMPLICATIONS
FOR HAWAIIAN WEATHER. THE GFS BRINGS A MODERATE INSTABILITY AND
MOISTURE INCREASE ASSOCIATED WITH THE LOW OVER THE ISLANDS...AROUND
MID-WEEK...AND ALSO BRINGS IT CLOSE ENOUGH TO VEER WINDS TO SSE FROM
TUESDAY INTO THE WEEKEND. MEANWHILE...THE NEWLY-ARRIVED ECMWF
GUIDANCE HAS TRENDED A LITTLE CLOSER TO THE GFS. ONGOING FORECAST
FAVORS THE OLDER ECMWF SOLUTION...WHICH ESSENTIALLY KEEPS A FAIRLY
STABLE AND BREEZY TRADE WIND FLOW IN PLACE THROUGH THE WEEK. WILL
LIKELY NUDGE THE WIND FORECAST A LITTLE MORE TOWARD THE SE FOR THE
LATTER PART OF THE WEEK IN DEFERENCE TO THIS. THE MID LEVEL RIDGE
CURRENTLY OVER THE ISLANDS WILL SHIFT SLIGHTLY E THIS WEEK...KEEPING
FAIRLY STABLE CONDITIONS IN PLACE NEAR THE BIG ISLAND...WITH KAUAI
WEATHER POTENTIALLY INFLUENCED BY THE LOW AFTER MID-WEEK.

&&

.AVIATION...
A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS THAT MOVED ASHORE IN
MANY AREAS THIS MORNING HAS CLEARED SUCH THAT AIRMET SIERRA FOR MTN
OBSCURATION WAS CANCELLED...BUT ENOUGH LINGERS NEAR WINDWARD BIG
ISLAND TO SUPPORT ITS CONTINUATION...AT LEAST FOR NOW. AIRMET TANGO
FOR LO LVL TURB BLO 080 WILL CONT FOR THE FORESEEABLE FUTURE FOR
ALL ISLANDS. WHILE VFR CONDITIONS WILL PREVAIL AT THE TERMINALS...
BRIEF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT WINDWARD LOCATIONS...
MOST NOTABLY PHTO/

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. WINDS ARE
EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE FORCE WINDS
EXPECTED IN CHANNELS AROUND MAUI AND THE BIG ISLAND. IN FACT...
LATEST GUIDANCE FROM HI-RES MODELS INDICATES GALE FORCE WINDS IN THE
ALENUIHAHA CHANNEL FROM TONIGHT INTO MONDAY NIGHT. THUS THE MARINE
FORECAST HAS BEEN MODIFIED TO UPGRADE THE SCA TO A GALE WARNING...
BEGINNING LATER TODAY...FOR THIS CHANNEL. ALTHOUGH WINDS MAY EASE
AFTER TUESDAY...ONLY A SLIGHT DOWNTREND IS EXPECTED...AND THE SCA
WILL LIKELY NEED TO BE EXTENDED.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG E FACING SHORES THE NEXT FEW DAYS...WITH RATHER ROUGH AND
CHOPPY SURF UNDER THE WINDS. LATEST NEAR SHORE BUOY OBSERVATIONS
INDICATE 8-9 FOOT SEAS WITH A DOMINANT PERIOD OF 8-9 SECONDS...WHICH
IS VERY CLOSE TO THE VALUES WE NORMALLY LOOK FOR WHEN ISSUING HIGH
SURF ADVISORIES FOR TRADE WIND SWELLS. WILL LIKELY BE ISSUING AN
ADVISORY AS WAVE WATCH ANTICIPATES A SLIGHT INCREASE IN WAVE
HEIGHTS.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...AND
THE CDIP/PACIOOS BUOY NEAR LANAI HAS BEEN DETECTING FORERUNNERS IN
THE 20-SECOND BAND ALREADY THIS MORNING. THIS SWELL WILL PEAK AROUND
TUESDAY...AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE
WEEK...WITH NEAR ADVISORY LEVEL SURF ALONG S FACING SHORES DURING
THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FROM 4 PM TODAY TO 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY UNTIL 6 AM WEDNESDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

&&

$$

BIRCHARD





000
FXHW60 PHFO 192016
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1015 AM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING WINDY CONDITIONS
THE NEXT COUPLE OF DAYS...WITH BREEZY CONDITIONS PREVAILING FOR THE
REMAINDER OF THE WEEK. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. A
DISTURBANCE NORTHWEST OF THE ISLANDS MAY TURN WINDS TOWARD THE
SOUTHEAST LATER IN THE WEEK...POTENTIALLY BRINGING INCREASED SHOWERS
TO KAUAI.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. THE HIGH TO
THE NE IS TRACKING SW AND WEAKENING WHILE THE HIGH TO THE NW IS
TRACKING E AND STRENGTHENING. MID AND UPPER LEVEL ANALYSIS INDICATES
A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...WITH EARLY MORNING
SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE INVERSION IS
BETWEEN 6 AND 8 KFT. DESPITE THE STABLE ATMOSPHERE...MOISTURE
EMBEDDED IN THE TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW OPEN OCEAN
SHOWERS...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR THE REMAINDER OF
TODAY...THE EXPECTATION IS THAT CLOUDS AND SHOWERS WILL DIMINISH ON
KAUAI AND OAHU AS UPSTREAM MOISTURE WANES...BUT A CLUSTER OF BROKEN
LOW CLOUDS UPSTREAM OF MAUI AND THE BIG ISLAND WILL LIKELY KEEP
WINDWARD AREAS OF THOSE ISLANDS A LITTLE CLOUDIER AND WETTER
THROUGH THE DAY. SOME OF THIS MOISTURE IS EXPECTED TO FUEL TRADE
SHOWERS OVER KAUAI AND OAHU TONIGHT.

THE HIGH TO THE NW WILL TRACK STEADILY TOWARD THE E AND STRENGTHEN
OVER THE NEXT 24-48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE
ISLANDS ON TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...
THE HIGH WILL SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR
TRADE WINDS TO INCREASE A NOTCH TODAY AND TONIGHT...REMAINING WINDY
THROUGH TUESDAY...WITH WINDS EASING JUST A LITTLE LATER IN THE WEEK.
IN THE SHORT-TERM...THE WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE ARE SOME DIFFERENCES WITH RESPECT TO OTHER
FEATURES. ALTHOUGH THE MODEL SOLUTIONS ARE A LITTLE MORE CLOSELY
ALIGNED WITH RESPECT TO THE ANTICIPATED DEVELOPMENT AND EVOLUTION OF
A CUT-OFF LOW TO THE NW OF THE ISLANDS TUESDAY/WEDNESDAY...ENOUGH OF
A DIFFERENCE EXISTS BETWEEN THE GFS AND ECMWF TO HAVE IMPLICATIONS
FOR HAWAIIAN WEATHER. THE GFS BRINGS A MODERATE INSTABILITY AND
MOISTURE INCREASE ASSOCIATED WITH THE LOW OVER THE ISLANDS...AROUND
MID-WEEK...AND ALSO BRINGS IT CLOSE ENOUGH TO VEER WINDS TO SSE FROM
TUESDAY INTO THE WEEKEND. MEANWHILE...THE NEWLY-ARRIVED ECMWF
GUIDANCE HAS TRENDED A LITTLE CLOSER TO THE GFS. ONGOING FORECAST
FAVORS THE OLDER ECMWF SOLUTION...WHICH ESSENTIALLY KEEPS A FAIRLY
STABLE AND BREEZY TRADE WIND FLOW IN PLACE THROUGH THE WEEK. WILL
LIKELY NUDGE THE WIND FORECAST A LITTLE MORE TOWARD THE SE FOR THE
LATTER PART OF THE WEEK IN DEFERENCE TO THIS. THE MID LEVEL RIDGE
CURRENTLY OVER THE ISLANDS WILL SHIFT SLIGHTLY E THIS WEEK...KEEPING
FAIRLY STABLE CONDITIONS IN PLACE NEAR THE BIG ISLAND...WITH KAUAI
WEATHER POTENTIALLY INFLUENCED BY THE LOW AFTER MID-WEEK.

&&

.AVIATION...
A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS THAT MOVED ASHORE IN
MANY AREAS THIS MORNING HAS CLEARED SUCH THAT AIRMET SIERRA FOR MTN
OBSCURATION WAS CANCELLED...BUT ENOUGH LINGERS NEAR WINDWARD BIG
ISLAND TO SUPPORT ITS CONTINUATION...AT LEAST FOR NOW. AIRMET TANGO
FOR LO LVL TURB BLO 080 WILL CONT FOR THE FORESEEABLE FUTURE FOR
ALL ISLANDS. WHILE VFR CONDITIONS WILL PREVAIL AT THE TERMINALS...
BRIEF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT WINDWARD LOCATIONS...
MOST NOTABLY PHTO/

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. WINDS ARE
EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE FORCE WINDS
EXPECTED IN CHANNELS AROUND MAUI AND THE BIG ISLAND. IN FACT...
LATEST GUIDANCE FROM HI-RES MODELS INDICATES GALE FORCE WINDS IN THE
ALENUIHAHA CHANNEL FROM TONIGHT INTO MONDAY NIGHT. THUS THE MARINE
FORECAST HAS BEEN MODIFIED TO UPGRADE THE SCA TO A GALE WARNING...
BEGINNING LATER TODAY...FOR THIS CHANNEL. ALTHOUGH WINDS MAY EASE
AFTER TUESDAY...ONLY A SLIGHT DOWNTREND IS EXPECTED...AND THE SCA
WILL LIKELY NEED TO BE EXTENDED.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG E FACING SHORES THE NEXT FEW DAYS...WITH RATHER ROUGH AND
CHOPPY SURF UNDER THE WINDS. LATEST NEAR SHORE BUOY OBSERVATIONS
INDICATE 8-9 FOOT SEAS WITH A DOMINANT PERIOD OF 8-9 SECONDS...WHICH
IS VERY CLOSE TO THE VALUES WE NORMALLY LOOK FOR WHEN ISSUING HIGH
SURF ADVISORIES FOR TRADE WIND SWELLS. WILL LIKELY BE ISSUING AN
ADVISORY AS WAVE WATCH ANTICIPATES A SLIGHT INCREASE IN WAVE
HEIGHTS.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...AND
THE CDIP/PACIOOS BUOY NEAR LANAI HAS BEEN DETECTING FORERUNNERS IN
THE 20-SECOND BAND ALREADY THIS MORNING. THIS SWELL WILL PEAK AROUND
TUESDAY...AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE
WEEK...WITH NEAR ADVISORY LEVEL SURF ALONG S FACING SHORES DURING
THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FROM 4 PM TODAY TO 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

BIRCHARD






000
FXHW60 PHFO 192016
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1015 AM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE PASSING NORTH OF THE STATE WILL BRING WINDY CONDITIONS
THE NEXT COUPLE OF DAYS...WITH BREEZY CONDITIONS PREVAILING FOR THE
REMAINDER OF THE WEEK. THE TRADE WINDS WILL FOCUS CLOUDS AND SHOWERS
OVER WINDWARD SLOPES AND COASTS...BUT A FEW SHOWERS WILL SPREAD
LEEWARD...WITH SHOWERS MOST ACTIVE DURING NIGHTS AND MORNINGS. A
DISTURBANCE NORTHWEST OF THE ISLANDS MAY TURN WINDS TOWARD THE
SOUTHEAST LATER IN THE WEEK...POTENTIALLY BRINGING INCREASED SHOWERS
TO KAUAI.

&&

.DISCUSSION...
LATEST SURFACE ANALYSIS FEATURES TWO HIGH PRESSURE CENTERS WELL N
OF THE ISLANDS...ONE TO THE NE AND THE OTHER TO THE NW. THE HIGH TO
THE NE IS TRACKING SW AND WEAKENING WHILE THE HIGH TO THE NW IS
TRACKING E AND STRENGTHENING. MID AND UPPER LEVEL ANALYSIS INDICATES
A RIDGE DIRECTLY OVERHEAD OF THE ISLANDS...WITH EARLY MORNING
SOUNDINGS INDICATING THAT THE BASE OF THE SUBSIDENCE INVERSION IS
BETWEEN 6 AND 8 KFT. DESPITE THE STABLE ATMOSPHERE...MOISTURE
EMBEDDED IN THE TRADE FLOW IS DEEP ENOUGH TO FUEL A FEW OPEN OCEAN
SHOWERS...WHILE OROGRAPHIC FORCING OF THE STRONG TRADE WIND FLOW IS
ALSO AIDING IN PROMOTING SHOWER DEVELOPMENT. FOR THE REMAINDER OF
TODAY...THE EXPECTATION IS THAT CLOUDS AND SHOWERS WILL DIMINISH ON
KAUAI AND OAHU AS UPSTREAM MOISTURE WANES...BUT A CLUSTER OF BROKEN
LOW CLOUDS UPSTREAM OF MAUI AND THE BIG ISLAND WILL LIKELY KEEP
WINDWARD AREAS OF THOSE ISLANDS A LITTLE CLOUDIER AND WETTER
THROUGH THE DAY. SOME OF THIS MOISTURE IS EXPECTED TO FUEL TRADE
SHOWERS OVER KAUAI AND OAHU TONIGHT.

THE HIGH TO THE NW WILL TRACK STEADILY TOWARD THE E AND STRENGTHEN
OVER THE NEXT 24-48 HOURS...TOPPING OUT NEAR 1034 MB FAR NE OF THE
ISLANDS ON TUESDAY. FROM WEDNESDAY THROUGH THE END OF THE WEEK...
THE HIGH WILL SLOWLY WEAKEN AS IT DRIFTS S. THUS WE ARE LOOKING FOR
TRADE WINDS TO INCREASE A NOTCH TODAY AND TONIGHT...REMAINING WINDY
THROUGH TUESDAY...WITH WINDS EASING JUST A LITTLE LATER IN THE WEEK.
IN THE SHORT-TERM...THE WINDS MAY REACH ADVISORY LEVEL IN SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

FOR THE MOST PART MODELS AGREE ON THE EVOLUTION OF THE SURFACE
HIGH...BUT THERE ARE SOME DIFFERENCES WITH RESPECT TO OTHER
FEATURES. ALTHOUGH THE MODEL SOLUTIONS ARE A LITTLE MORE CLOSELY
ALIGNED WITH RESPECT TO THE ANTICIPATED DEVELOPMENT AND EVOLUTION OF
A CUT-OFF LOW TO THE NW OF THE ISLANDS TUESDAY/WEDNESDAY...ENOUGH OF
A DIFFERENCE EXISTS BETWEEN THE GFS AND ECMWF TO HAVE IMPLICATIONS
FOR HAWAIIAN WEATHER. THE GFS BRINGS A MODERATE INSTABILITY AND
MOISTURE INCREASE ASSOCIATED WITH THE LOW OVER THE ISLANDS...AROUND
MID-WEEK...AND ALSO BRINGS IT CLOSE ENOUGH TO VEER WINDS TO SSE FROM
TUESDAY INTO THE WEEKEND. MEANWHILE...THE NEWLY-ARRIVED ECMWF
GUIDANCE HAS TRENDED A LITTLE CLOSER TO THE GFS. ONGOING FORECAST
FAVORS THE OLDER ECMWF SOLUTION...WHICH ESSENTIALLY KEEPS A FAIRLY
STABLE AND BREEZY TRADE WIND FLOW IN PLACE THROUGH THE WEEK. WILL
LIKELY NUDGE THE WIND FORECAST A LITTLE MORE TOWARD THE SE FOR THE
LATTER PART OF THE WEEK IN DEFERENCE TO THIS. THE MID LEVEL RIDGE
CURRENTLY OVER THE ISLANDS WILL SHIFT SLIGHTLY E THIS WEEK...KEEPING
FAIRLY STABLE CONDITIONS IN PLACE NEAR THE BIG ISLAND...WITH KAUAI
WEATHER POTENTIALLY INFLUENCED BY THE LOW AFTER MID-WEEK.

&&

.AVIATION...
A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS THAT MOVED ASHORE IN
MANY AREAS THIS MORNING HAS CLEARED SUCH THAT AIRMET SIERRA FOR MTN
OBSCURATION WAS CANCELLED...BUT ENOUGH LINGERS NEAR WINDWARD BIG
ISLAND TO SUPPORT ITS CONTINUATION...AT LEAST FOR NOW. AIRMET TANGO
FOR LO LVL TURB BLO 080 WILL CONT FOR THE FORESEEABLE FUTURE FOR
ALL ISLANDS. WHILE VFR CONDITIONS WILL PREVAIL AT THE TERMINALS...
BRIEF MVFR CIG/VIS IN SHRA CAN BE EXPECTED AT WINDWARD LOCATIONS...
MOST NOTABLY PHTO/

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT THROUGH TUESDAY FOR ALL
HAWAIIAN WATERS...DUE TO WINDS AND SEAS ASSOCIATED WITH
STRENGTHENING HIGH PRESSURE PASSING N OF THE ISLANDS. WINDS ARE
EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE FORCE WINDS
EXPECTED IN CHANNELS AROUND MAUI AND THE BIG ISLAND. IN FACT...
LATEST GUIDANCE FROM HI-RES MODELS INDICATES GALE FORCE WINDS IN THE
ALENUIHAHA CHANNEL FROM TONIGHT INTO MONDAY NIGHT. THUS THE MARINE
FORECAST HAS BEEN MODIFIED TO UPGRADE THE SCA TO A GALE WARNING...
BEGINNING LATER TODAY...FOR THIS CHANNEL. ALTHOUGH WINDS MAY EASE
AFTER TUESDAY...ONLY A SLIGHT DOWNTREND IS EXPECTED...AND THE SCA
WILL LIKELY NEED TO BE EXTENDED.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG E FACING SHORES THE NEXT FEW DAYS...WITH RATHER ROUGH AND
CHOPPY SURF UNDER THE WINDS. LATEST NEAR SHORE BUOY OBSERVATIONS
INDICATE 8-9 FOOT SEAS WITH A DOMINANT PERIOD OF 8-9 SECONDS...WHICH
IS VERY CLOSE TO THE VALUES WE NORMALLY LOOK FOR WHEN ISSUING HIGH
SURF ADVISORIES FOR TRADE WIND SWELLS. WILL LIKELY BE ISSUING AN
ADVISORY AS WAVE WATCH ANTICIPATES A SLIGHT INCREASE IN WAVE
HEIGHTS.

SMALL NW SWELLS ARE EXPECTED TO PEAK TODAY AND THEN AGAIN ON
TUESDAY...WITH PEAK SURF HEIGHTS WELL BELOW ADVISORY LEVELS. A
LONG-PERIOD SSW SWELL IS EXPECTED TO SLOWLY BUILD INTO TUESDAY...AND
THE CDIP/PACIOOS BUOY NEAR LANAI HAS BEEN DETECTING FORERUNNERS IN
THE 20-SECOND BAND ALREADY THIS MORNING. THIS SWELL WILL PEAK AROUND
TUESDAY...AND THEN SLOWLY DIMINISH THROUGH THE REST OF THE
WEEK...WITH NEAR ADVISORY LEVEL SURF ALONG S FACING SHORES DURING
THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING FROM 4 PM TODAY TO 6 AM TUESDAY FOR ALENUIHAHA CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

BIRCHARD





000
FXHW60 PHFO 191359
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE NORTH OF THE STATE WILL BRING BREEZY TRADE WINDS
THROUGH THE FIRST HALF OF THE WEEK. THE TRADE WINDS WILL FOCUS
CLOUDS AND SHOWERS MAINLY OVER WINDWARD AREAS. A DISTURBANCE
DEVELOPING FAR WEST OF THE ISLANDS MAY RESULT IN SLIGHTLY WEAKER
WINDS BY THE SECOND HALF OF THE WEEK.

&&

.DISCUSSION...
TRADE WIND WEATHER CONTINUES OVER THE ISLANDS EARLY THIS MORNING AS
A SURFACE HIGH PRESSURE RIDGE STAYS NORTH OF THE STATE. LOW CLOUDS
AND SHOWERS DID INCREASE A TAD OVERNIGHT AS EXPECTED...AND AFFECT
MAINLY WINDWARD AREAS. LATEST SATELLITE IMAGERY INDICATED THERE IS A
LINE OF LOW CLOUDS REACHING THE WINDWARD BIG ISLAND EARLY THIS
MORNING AND WILL SPREAD TO MAUI COUNTY AND OAHU IN THE NEXT FEW
HOURS. EARLY MORNING LIHUE AND HILO SOUNDINGS CONTINUE TO REVEAL A
STABLE AIR MASS IN THE ISLAND VICINITY...WITH LOW LEVEL MOISTURE
EXTENDING TO SLIGHTLY ABOVE 8K FEET ON THE HILO SOUNDING.
THEREFORE...EXPECT MORE PASSING SHOWERS TO AFFECT MAINLY WINDWARD
AREAS THROUGH THE REST OF THE MORNING...WITH SOME SHOWERS REACHING
THE LEE AREAS OF THE SMALLER ISLANDS AT TIMES UNDER THE BREEZY TRADE
WINDS. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED UNDER THE
UNFAVORABLE ATMOSPHERIC CONDITIONS AS WELL AS THE BRISK TRADE WINDS.

A STRENGTHENING SURFACE HIGH PRESSURE FAR NORTHWEST OF THE STATE
WILL PASS NORTH OF THE STATE IN THE NEXT COUPLE OF DAYS...BRINGING A
TIGHTENING OF LOW LEVEL PRESSURE GRADIENT ACROSS THE AREA. IN
TURN...A FURTHER SLIGHT INCREASE OF TRADE WINDS IS EXPECTED TODAY
THROUGH MONDAY. A MID LEVEL HIGH WILL PERSIST IN THE ISLAND
VICINITY...KEEPING AIR MASS STABLE OVER THE AREA. BREEZY TRADE WIND
WEATHER WILL PREVAIL IN THE NEXT COUPLE OF DAYS...WITH PASSING LOW
CLOUDS AND SHOWERS AFFECTING MAINLY WINDWARD AREAS. LEE AREAS OF THE
SMALLER ISLANDS MAY SEE SOME SHOWERS AT TIMES...DUE TO THE STRONG
WINDS. FURTHERMORE...THE WINDS MAY REACH ADVISORY LEVEL FOR SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

THE AFOREMENTIONED SURFACE HIGH WILL MOVE TO FAR NORTHEAST OF THE
STATE BY TUESDAY...THEN WEAKEN SOMEWHAT BUT SAG SOUTH CLOSER TO THE
ISLANDS. LATEST MODEL SOLUTIONS CONTINUE TO ALIGN CLOSER TO EACH
OTHER...WITH A SURFACE LOW PRESSURE SYSTEM EXPECTING TO DEVELOP FAR
WEST OF THE STATE BY THE LATER HALF OF THE WEEK. THIS SYSTEM MAY
STILL BE CLOSE ENOUGH TO THE STATE SUCH THAT WINDS MAY TURN A LITTLE
MORE SOUTHEASTERLY ACROSS THE AREA. MEANWHILE...A SURFACE HIGH
PRESSURE IS EXPECTED TO PERSIST NORTHEAST OF THE STATE...KEEPING
RATHER ROBUST WINDS OVER THE ISLANDS. MODEL SOLUTIONS STILL SHOW A
SLIGHT INCREASE IN MOISTURE ACROSS THE AREA...WITH GFS CONTINUES TO
HAVE A WETTER FORECAST. PREVIOUS FORECAST PACKAGE WAS ON
TRACK...HENCE HAVE ONLY DONE SOME MINOR TWEAKING TO THE WINDS AS
WELL AS INTRODUCING MORE BREAKS IN THE CHANCE OF PRECIPITATION
COVERAGE FOR THIS ONE. TRADE WIND WEATHER WILL PROBABLY CONTINUE FOR
THE LATER HALF OF THE WEEK...THROUGH WITH WINDS TURNING A LITTLE
MORE SOUTHEAST AND SLIGHTLY WEAKER WHILE THE ISLANDS MAY SEE A
SLIGHT INCREASE IN CLOUDS AND SHOWERS AS WELL.

&&

.AVIATION...
THE SOUTHERN FRINGE TO A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS
INCREASED AND MOVED ASHORE ON THE BIG ISLAND PROMPTING AN AIRMET
SIERRA FOR MTN OBSCURATION ACROSS THE ISLAND/S NE FACING SLOPES
ABOVE 25 HUNDRED FEET. THIS PATCH IS JUST PART OF A LONG EXTENSION
OF AREAS OF SHOWER BEARING CLOUDS AIMED AT THE ISLANDS...PRIMARILY
THE BIG ISLAND AND MAUI. THIS EXTENSION STRETCHED UPWIND OF THE
ISLANDS FOR AT LEAST 400 MILES. UNLIKE THE BIG ISLAND...POCKETS OF
LOW CLOUDS MOSTLY DISSIPATED UPON REACHING THE REMAINING ISLANDS
WITH BRIEF MVFR CIGS AND VIS NOTED. THUS...NO AIRMET SIERRA
ISSUED...BUT WE WILL BE MONITORING CLOSELY FOR THOSE CLOUDS/SHOWERS
UPWIND OF THE ISLANDS. LEE SECTIONS OF THE SMALLER ISLANDS WILL
CONTINUE DRY ALTHO A STRAY SHOWER OR TWO MAY ENTER THE LEEWARD ZONE.
LEEWARD BIG ISLAND WILL HAVE SOME MINOR AFTERNOON CLOUDS AND
ISOLATED SHOWER AT BEST.

AIRMET TANGO FOR LO LVL TURB BLO 080 WILL CONT THRU AT LEAST 22Z FOR
ALL ISLANDS. THIS IS DUE TO A MOD TO STRONG TRADE WIND FLOW WITH A
MODERATELY STRONG INVERSION BETWEEN 6 AND 7K FEET.

&&

.MARINE...
SMALL CRAFT WIND CONDITIONS WILL PREVAIL FOR ALL COASTAL WATERS AS
THE WINDS ARE EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE
FORCE WINDS IN CHANNELS AROUND MAUI AND THE BIG ISLAND.
MOREOVER...THE RATHER STRONG WINDS WILL CONTINUE THROUGH THE EARLY
PART OF THIS WEEK. THUS A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR
ALL COASTAL WATERS THROUGH EARLY TUESDAY.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG EAST FACING SHORES IN THE NEXT FEW DAYS...WITH RATHER ROUGH
AND CHOPPY SURF UNDER THE WINDS. A NEW SMALL NORTHWEST SWELLS ARE
EXPECTED ON TODAY AND TUESDAY...THOUGH SURF HEIGHTS FROM THE SWELLS
WILL REMAIN BELOW ADVISORY LEVELS. A LONG-PERIOD SOUTH-SOUTHWEST
SWELL IS EXPECTED TO ARRIVE TONIGHT...PEAKING LATE MONDAY INTO
TUESDAY...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH
NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES DURING THE PEAK
OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

AVIATION...LAU
REST...HUI





000
FXHW60 PHFO 191359
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE NORTH OF THE STATE WILL BRING BREEZY TRADE WINDS
THROUGH THE FIRST HALF OF THE WEEK. THE TRADE WINDS WILL FOCUS
CLOUDS AND SHOWERS MAINLY OVER WINDWARD AREAS. A DISTURBANCE
DEVELOPING FAR WEST OF THE ISLANDS MAY RESULT IN SLIGHTLY WEAKER
WINDS BY THE SECOND HALF OF THE WEEK.

&&

.DISCUSSION...
TRADE WIND WEATHER CONTINUES OVER THE ISLANDS EARLY THIS MORNING AS
A SURFACE HIGH PRESSURE RIDGE STAYS NORTH OF THE STATE. LOW CLOUDS
AND SHOWERS DID INCREASE A TAD OVERNIGHT AS EXPECTED...AND AFFECT
MAINLY WINDWARD AREAS. LATEST SATELLITE IMAGERY INDICATED THERE IS A
LINE OF LOW CLOUDS REACHING THE WINDWARD BIG ISLAND EARLY THIS
MORNING AND WILL SPREAD TO MAUI COUNTY AND OAHU IN THE NEXT FEW
HOURS. EARLY MORNING LIHUE AND HILO SOUNDINGS CONTINUE TO REVEAL A
STABLE AIR MASS IN THE ISLAND VICINITY...WITH LOW LEVEL MOISTURE
EXTENDING TO SLIGHTLY ABOVE 8K FEET ON THE HILO SOUNDING.
THEREFORE...EXPECT MORE PASSING SHOWERS TO AFFECT MAINLY WINDWARD
AREAS THROUGH THE REST OF THE MORNING...WITH SOME SHOWERS REACHING
THE LEE AREAS OF THE SMALLER ISLANDS AT TIMES UNDER THE BREEZY TRADE
WINDS. RAINFALL AMOUNTS WILL BE SOMEWHAT LIMITED UNDER THE
UNFAVORABLE ATMOSPHERIC CONDITIONS AS WELL AS THE BRISK TRADE WINDS.

A STRENGTHENING SURFACE HIGH PRESSURE FAR NORTHWEST OF THE STATE
WILL PASS NORTH OF THE STATE IN THE NEXT COUPLE OF DAYS...BRINGING A
TIGHTENING OF LOW LEVEL PRESSURE GRADIENT ACROSS THE AREA. IN
TURN...A FURTHER SLIGHT INCREASE OF TRADE WINDS IS EXPECTED TODAY
THROUGH MONDAY. A MID LEVEL HIGH WILL PERSIST IN THE ISLAND
VICINITY...KEEPING AIR MASS STABLE OVER THE AREA. BREEZY TRADE WIND
WEATHER WILL PREVAIL IN THE NEXT COUPLE OF DAYS...WITH PASSING LOW
CLOUDS AND SHOWERS AFFECTING MAINLY WINDWARD AREAS. LEE AREAS OF THE
SMALLER ISLANDS MAY SEE SOME SHOWERS AT TIMES...DUE TO THE STRONG
WINDS. FURTHERMORE...THE WINDS MAY REACH ADVISORY LEVEL FOR SOME
WIND-PRONE AREAS ACROSS THE ISLANDS UNDER THE STABLE AIR MASS.

THE AFOREMENTIONED SURFACE HIGH WILL MOVE TO FAR NORTHEAST OF THE
STATE BY TUESDAY...THEN WEAKEN SOMEWHAT BUT SAG SOUTH CLOSER TO THE
ISLANDS. LATEST MODEL SOLUTIONS CONTINUE TO ALIGN CLOSER TO EACH
OTHER...WITH A SURFACE LOW PRESSURE SYSTEM EXPECTING TO DEVELOP FAR
WEST OF THE STATE BY THE LATER HALF OF THE WEEK. THIS SYSTEM MAY
STILL BE CLOSE ENOUGH TO THE STATE SUCH THAT WINDS MAY TURN A LITTLE
MORE SOUTHEASTERLY ACROSS THE AREA. MEANWHILE...A SURFACE HIGH
PRESSURE IS EXPECTED TO PERSIST NORTHEAST OF THE STATE...KEEPING
RATHER ROBUST WINDS OVER THE ISLANDS. MODEL SOLUTIONS STILL SHOW A
SLIGHT INCREASE IN MOISTURE ACROSS THE AREA...WITH GFS CONTINUES TO
HAVE A WETTER FORECAST. PREVIOUS FORECAST PACKAGE WAS ON
TRACK...HENCE HAVE ONLY DONE SOME MINOR TWEAKING TO THE WINDS AS
WELL AS INTRODUCING MORE BREAKS IN THE CHANCE OF PRECIPITATION
COVERAGE FOR THIS ONE. TRADE WIND WEATHER WILL PROBABLY CONTINUE FOR
THE LATER HALF OF THE WEEK...THROUGH WITH WINDS TURNING A LITTLE
MORE SOUTHEAST AND SLIGHTLY WEAKER WHILE THE ISLANDS MAY SEE A
SLIGHT INCREASE IN CLOUDS AND SHOWERS AS WELL.

&&

.AVIATION...
THE SOUTHERN FRINGE TO A PATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS
INCREASED AND MOVED ASHORE ON THE BIG ISLAND PROMPTING AN AIRMET
SIERRA FOR MTN OBSCURATION ACROSS THE ISLAND/S NE FACING SLOPES
ABOVE 25 HUNDRED FEET. THIS PATCH IS JUST PART OF A LONG EXTENSION
OF AREAS OF SHOWER BEARING CLOUDS AIMED AT THE ISLANDS...PRIMARILY
THE BIG ISLAND AND MAUI. THIS EXTENSION STRETCHED UPWIND OF THE
ISLANDS FOR AT LEAST 400 MILES. UNLIKE THE BIG ISLAND...POCKETS OF
LOW CLOUDS MOSTLY DISSIPATED UPON REACHING THE REMAINING ISLANDS
WITH BRIEF MVFR CIGS AND VIS NOTED. THUS...NO AIRMET SIERRA
ISSUED...BUT WE WILL BE MONITORING CLOSELY FOR THOSE CLOUDS/SHOWERS
UPWIND OF THE ISLANDS. LEE SECTIONS OF THE SMALLER ISLANDS WILL
CONTINUE DRY ALTHO A STRAY SHOWER OR TWO MAY ENTER THE LEEWARD ZONE.
LEEWARD BIG ISLAND WILL HAVE SOME MINOR AFTERNOON CLOUDS AND
ISOLATED SHOWER AT BEST.

AIRMET TANGO FOR LO LVL TURB BLO 080 WILL CONT THRU AT LEAST 22Z FOR
ALL ISLANDS. THIS IS DUE TO A MOD TO STRONG TRADE WIND FLOW WITH A
MODERATELY STRONG INVERSION BETWEEN 6 AND 7K FEET.

&&

.MARINE...
SMALL CRAFT WIND CONDITIONS WILL PREVAIL FOR ALL COASTAL WATERS AS
THE WINDS ARE EXPECTED TO INCREASE A NOTCH TODAY...WITH NEAR GALE
FORCE WINDS IN CHANNELS AROUND MAUI AND THE BIG ISLAND.
MOREOVER...THE RATHER STRONG WINDS WILL CONTINUE THROUGH THE EARLY
PART OF THIS WEEK. THUS A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR
ALL COASTAL WATERS THROUGH EARLY TUESDAY.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG EAST FACING SHORES IN THE NEXT FEW DAYS...WITH RATHER ROUGH
AND CHOPPY SURF UNDER THE WINDS. A NEW SMALL NORTHWEST SWELLS ARE
EXPECTED ON TODAY AND TUESDAY...THOUGH SURF HEIGHTS FROM THE SWELLS
WILL REMAIN BELOW ADVISORY LEVELS. A LONG-PERIOD SOUTH-SOUTHWEST
SWELL IS EXPECTED TO ARRIVE TONIGHT...PEAKING LATE MONDAY INTO
TUESDAY...THEN SLOWLY DIMINISH THROUGH THE REST OF THE WEEK...WITH
NEAR ADVISORY LEVEL SURF ALONG SOUTH FACING SHORES DURING THE PEAK
OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

AVIATION...LAU
REST...HUI






000
FXHW60 PHFO 190657
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SAT APR 18 2015

.SYNOPSIS...
HIGH PRESSURE NORTH OF THE STATE WILL BRING BREEZY TRADE WINDS
THROUGH THE FIRST HALF OF NEXT WEEK. THE TRADE WINDS WILL FOCUS
CLOUDS AND SHOWERS MAINLY OVER WINDWARD AREAS. A DISTURBANCE
POSSIBLY DEVELOPING FAR NORTHWEST OF THE ISLANDS MAY BRING A WETTER
WEATHER PATTERN AND SOUTHEASTERLY WINDS TO THE STATE...BY THE
SECOND HALF OF THE WEEK.

&&

.DISCUSSION...
TRADE WIND WEATHER CONTINUES OVER THE ISLANDS THIS EVENING...WITH
PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY WINDWARD AREAS.
LATEST RADAR DATA SHOWED ONLY A FEW SHOWERS IN THE ISLAND VICINITY
AT THIS TIME...THOUGH SATELLITE IMAGERY INDICATED THERE IS A BROAD
PATCH OF LOW CLOUDS EAST OF MAUI COUNTY AND BIG ISLAND. THESE LOW
CLOUDS WILL REACH THE ISLANDS IN THE COMING HOURS...BRINGING MORE
PASSING SHOWERS TO THE STATE. AIR MASS IS STABLE IN THE ISLAND
VICINITY...AS AN UPPER LEVEL RIDGE HAS MOVED OVER THE AREA. AS
SUCH...RAINFALL AMOUNTS WILL BE LIMITED.

A STRENGTHENING SURFACE HIGH PRESSURE FAR NORTHWEST OF THE STATE
WILL PASS NORTH OF THE STATE IN THE NEXT COUPLE OF DAYS. IN
TURN...PRESSURE GRADIENT ACROSS THE AREA WILL TIGHTEN...RESULTING IN
A FURTHER INCREASE OF TRADE WINDS THROUGH EARLY NEXT WEEK. A MID
LEVEL HIGH WILL PERSIST IN THE ISLAND VICINITY...AND WILL KEEP AIR
MASS STABLE OVER THE AREA. LOOK FOR BREEZY TRADE WIND WEATHER IN THE
NEXT FEW DAYS...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. LEE AREAS OF THE SMALLER ISLANDS MAY SEE A LITTLE
SHOWERS AS WELL...DUE TO THE STRONG WINDS.

THE AFOREMENTIONED SURFACE HIGH WILL MOVE TO FAR NORTHEAST OF THE
STATE BY TUESDAY...THEN WEAKEN SOMEWHAT BUT SAG SOUTH CLOSER TO THE
ISLANDS. LATEST MODEL SOLUTIONS ARE A LITTLE MORE IN-LINE WITH EACH
OTHER...AS THE LATEST GFS SOLUTION NOW LEAN BACK TOWARD THE EARLIER
ECMWF SOLUTION. A SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP FAR
WEST OF THE STATE BY THE LATER HALF OF NEXT WEEK...THOUGH THIS
SYSTEM WILL BE CLOSE ENOUGH TO THE ISLANDS SUCH THAT WINDS WILL TURN
A LITTLE MORE SOUTHEASTERLY. MEANWHILE...A SURFACE HIGH PRESSURE
WILL CONTINUE NORTHEAST OF THE AREA...AND WILL KEEP RATHER ROBUST
WINDS OVER THE ISLANDS. MODEL SOLUTIONS ALSO INDICATE A POSSIBLE
INCREASE IN MOISTURE IN THE ISLAND VICINITY...THOUGH AIR MASS MAY
REMAIN MARGINALLY STABLE. LOOKS LIKE TRADE WIND WEATHER MAY PERSIST
FOR THE LATER HALF OF NEXT WEEK OVER THE STATE...WITH SLIGHTLY
WEAKER WINDS AND MORE MOISTURE. DUE TO VARIATIONS IN THE FORECAST
BETWEEN MODEL RUNS...CONFIDENCE IN THE FORECAST REMAINS SOMEWHAT LOW
AT THIS TIME.

&&

.AVIATION...
WE ARE MONITORING AN AREA OF CLOUDS AND SHOWERS 90 MILES UPWIND OF
MAUI THAT MAY WARRANT AN AIRMET SIERRA FOR MTN OBSC AFTER 08Z FOR
PRIMARILY MOLOKAI AND MAUI.

ELSEWHERE...VFR WILL BE THE PREVAILING FLYING COND FOR THE OVERNIGHT
HOURS. THE ISOL SHOWERS NOW WILL INCREASE SLIGHTLY OVERNIGHT BRIEFLY
LOWERING THE CEILINGS AND VIS TO MVFR CONDS. THESE SHOWERS WILL
FAVOR THE WINDWARD AND MTN AREAS WITH A STRAY SHOWER OR TWO
DRIFTING INTO THE LEE SECTIONS OF THE SMALLER ISLANDS. BUT IT WILL
BE MOSTLY DRY THERE. BKN TO OVC LO CLOUDS OVER THE KONA SLOPES...
COAST...AND ADJ WATERS WILL GRADUALLY BE CLEARING OUT THROUGH 12Z.

DUE TO A MOD TO STRONG TRADE WIND FLOW WITH A MODERATELY STRONG
INVERSION BETWEEN 6 AND 7K FEET...AIRMET TANGO FOR LO LVL TURB BLO
080 WILL CONT THRU AT LEAST 16Z FOR ALL ISLANDS.

&&

.MARINE...
AS THE WINDS ARE EXPECTED TO INCREASE A NOTCH THROUGH SUNDAY...WITH
NEAR GALE FORCE WINDS IN CHANNELS AROUND MAUI AND THE BIG
ISLAND...SMALL CRAFT WIND CONDITIONS WILL PREVAIL OVER ALL COASTAL
WATERS. ADDITIONALLY...THE COMBINED SEAS WILL ALSO APPROACH THE
SMALL CRAFT THRESHOLD OF 10 FEET...WITH SEAS DOMINATED BY
SHORT-PERIOD WIND WAVES. THEREFORE SMALL CRAFT ADVISORY CONTINUES
FOR ALL COASTAL WATERS THROUGH EARLY TUESDAY.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG EAST FACING SHORES THROUGH EARLY NEXT WEEK. SURF WILL BE ROUGH
ALONG EAST FACING SHORES FOR THE NEXT SEVERAL DAYS REGARDLESS DUE TO
THE STRONG WINDS. A NEW SMALL NORTHWEST SWELLS ARE EXPECTED ON
SUNDAY AND TUESDAY...THOUGH SURF HEIGHTS FROM THE SWELL WILL REMAIN
BELOW ADVISORY LEVELS. A LONG-PERIOD SOUTH-SOUTHWEST SWELL WILL
ARRIVE LATE OVER THE WEEKEND AND PEAK AROUND TUESDAY...THEN SLOWLY
DIMINISH THROUGH THE WEEK...WITH SURF ALONG SOUTH FACING SHORES
APPROACHING ADVISORY LEVELS DURING THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

AVIATION...LAU
REST...HUI





000
FXHW60 PHFO 190657
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SAT APR 18 2015

.SYNOPSIS...
HIGH PRESSURE NORTH OF THE STATE WILL BRING BREEZY TRADE WINDS
THROUGH THE FIRST HALF OF NEXT WEEK. THE TRADE WINDS WILL FOCUS
CLOUDS AND SHOWERS MAINLY OVER WINDWARD AREAS. A DISTURBANCE
POSSIBLY DEVELOPING FAR NORTHWEST OF THE ISLANDS MAY BRING A WETTER
WEATHER PATTERN AND SOUTHEASTERLY WINDS TO THE STATE...BY THE
SECOND HALF OF THE WEEK.

&&

.DISCUSSION...
TRADE WIND WEATHER CONTINUES OVER THE ISLANDS THIS EVENING...WITH
PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY WINDWARD AREAS.
LATEST RADAR DATA SHOWED ONLY A FEW SHOWERS IN THE ISLAND VICINITY
AT THIS TIME...THOUGH SATELLITE IMAGERY INDICATED THERE IS A BROAD
PATCH OF LOW CLOUDS EAST OF MAUI COUNTY AND BIG ISLAND. THESE LOW
CLOUDS WILL REACH THE ISLANDS IN THE COMING HOURS...BRINGING MORE
PASSING SHOWERS TO THE STATE. AIR MASS IS STABLE IN THE ISLAND
VICINITY...AS AN UPPER LEVEL RIDGE HAS MOVED OVER THE AREA. AS
SUCH...RAINFALL AMOUNTS WILL BE LIMITED.

A STRENGTHENING SURFACE HIGH PRESSURE FAR NORTHWEST OF THE STATE
WILL PASS NORTH OF THE STATE IN THE NEXT COUPLE OF DAYS. IN
TURN...PRESSURE GRADIENT ACROSS THE AREA WILL TIGHTEN...RESULTING IN
A FURTHER INCREASE OF TRADE WINDS THROUGH EARLY NEXT WEEK. A MID
LEVEL HIGH WILL PERSIST IN THE ISLAND VICINITY...AND WILL KEEP AIR
MASS STABLE OVER THE AREA. LOOK FOR BREEZY TRADE WIND WEATHER IN THE
NEXT FEW DAYS...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. LEE AREAS OF THE SMALLER ISLANDS MAY SEE A LITTLE
SHOWERS AS WELL...DUE TO THE STRONG WINDS.

THE AFOREMENTIONED SURFACE HIGH WILL MOVE TO FAR NORTHEAST OF THE
STATE BY TUESDAY...THEN WEAKEN SOMEWHAT BUT SAG SOUTH CLOSER TO THE
ISLANDS. LATEST MODEL SOLUTIONS ARE A LITTLE MORE IN-LINE WITH EACH
OTHER...AS THE LATEST GFS SOLUTION NOW LEAN BACK TOWARD THE EARLIER
ECMWF SOLUTION. A SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP FAR
WEST OF THE STATE BY THE LATER HALF OF NEXT WEEK...THOUGH THIS
SYSTEM WILL BE CLOSE ENOUGH TO THE ISLANDS SUCH THAT WINDS WILL TURN
A LITTLE MORE SOUTHEASTERLY. MEANWHILE...A SURFACE HIGH PRESSURE
WILL CONTINUE NORTHEAST OF THE AREA...AND WILL KEEP RATHER ROBUST
WINDS OVER THE ISLANDS. MODEL SOLUTIONS ALSO INDICATE A POSSIBLE
INCREASE IN MOISTURE IN THE ISLAND VICINITY...THOUGH AIR MASS MAY
REMAIN MARGINALLY STABLE. LOOKS LIKE TRADE WIND WEATHER MAY PERSIST
FOR THE LATER HALF OF NEXT WEEK OVER THE STATE...WITH SLIGHTLY
WEAKER WINDS AND MORE MOISTURE. DUE TO VARIATIONS IN THE FORECAST
BETWEEN MODEL RUNS...CONFIDENCE IN THE FORECAST REMAINS SOMEWHAT LOW
AT THIS TIME.

&&

.AVIATION...
WE ARE MONITORING AN AREA OF CLOUDS AND SHOWERS 90 MILES UPWIND OF
MAUI THAT MAY WARRANT AN AIRMET SIERRA FOR MTN OBSC AFTER 08Z FOR
PRIMARILY MOLOKAI AND MAUI.

ELSEWHERE...VFR WILL BE THE PREVAILING FLYING COND FOR THE OVERNIGHT
HOURS. THE ISOL SHOWERS NOW WILL INCREASE SLIGHTLY OVERNIGHT BRIEFLY
LOWERING THE CEILINGS AND VIS TO MVFR CONDS. THESE SHOWERS WILL
FAVOR THE WINDWARD AND MTN AREAS WITH A STRAY SHOWER OR TWO
DRIFTING INTO THE LEE SECTIONS OF THE SMALLER ISLANDS. BUT IT WILL
BE MOSTLY DRY THERE. BKN TO OVC LO CLOUDS OVER THE KONA SLOPES...
COAST...AND ADJ WATERS WILL GRADUALLY BE CLEARING OUT THROUGH 12Z.

DUE TO A MOD TO STRONG TRADE WIND FLOW WITH A MODERATELY STRONG
INVERSION BETWEEN 6 AND 7K FEET...AIRMET TANGO FOR LO LVL TURB BLO
080 WILL CONT THRU AT LEAST 16Z FOR ALL ISLANDS.

&&

.MARINE...
AS THE WINDS ARE EXPECTED TO INCREASE A NOTCH THROUGH SUNDAY...WITH
NEAR GALE FORCE WINDS IN CHANNELS AROUND MAUI AND THE BIG
ISLAND...SMALL CRAFT WIND CONDITIONS WILL PREVAIL OVER ALL COASTAL
WATERS. ADDITIONALLY...THE COMBINED SEAS WILL ALSO APPROACH THE
SMALL CRAFT THRESHOLD OF 10 FEET...WITH SEAS DOMINATED BY
SHORT-PERIOD WIND WAVES. THEREFORE SMALL CRAFT ADVISORY CONTINUES
FOR ALL COASTAL WATERS THROUGH EARLY TUESDAY.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG EAST FACING SHORES THROUGH EARLY NEXT WEEK. SURF WILL BE ROUGH
ALONG EAST FACING SHORES FOR THE NEXT SEVERAL DAYS REGARDLESS DUE TO
THE STRONG WINDS. A NEW SMALL NORTHWEST SWELLS ARE EXPECTED ON
SUNDAY AND TUESDAY...THOUGH SURF HEIGHTS FROM THE SWELL WILL REMAIN
BELOW ADVISORY LEVELS. A LONG-PERIOD SOUTH-SOUTHWEST SWELL WILL
ARRIVE LATE OVER THE WEEKEND AND PEAK AROUND TUESDAY...THEN SLOWLY
DIMINISH THROUGH THE WEEK...WITH SURF ALONG SOUTH FACING SHORES
APPROACHING ADVISORY LEVELS DURING THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

AVIATION...LAU
REST...HUI






000
FXHW60 PHFO 190657
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SAT APR 18 2015

.SYNOPSIS...
HIGH PRESSURE NORTH OF THE STATE WILL BRING BREEZY TRADE WINDS
THROUGH THE FIRST HALF OF NEXT WEEK. THE TRADE WINDS WILL FOCUS
CLOUDS AND SHOWERS MAINLY OVER WINDWARD AREAS. A DISTURBANCE
POSSIBLY DEVELOPING FAR NORTHWEST OF THE ISLANDS MAY BRING A WETTER
WEATHER PATTERN AND SOUTHEASTERLY WINDS TO THE STATE...BY THE
SECOND HALF OF THE WEEK.

&&

.DISCUSSION...
TRADE WIND WEATHER CONTINUES OVER THE ISLANDS THIS EVENING...WITH
PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY WINDWARD AREAS.
LATEST RADAR DATA SHOWED ONLY A FEW SHOWERS IN THE ISLAND VICINITY
AT THIS TIME...THOUGH SATELLITE IMAGERY INDICATED THERE IS A BROAD
PATCH OF LOW CLOUDS EAST OF MAUI COUNTY AND BIG ISLAND. THESE LOW
CLOUDS WILL REACH THE ISLANDS IN THE COMING HOURS...BRINGING MORE
PASSING SHOWERS TO THE STATE. AIR MASS IS STABLE IN THE ISLAND
VICINITY...AS AN UPPER LEVEL RIDGE HAS MOVED OVER THE AREA. AS
SUCH...RAINFALL AMOUNTS WILL BE LIMITED.

A STRENGTHENING SURFACE HIGH PRESSURE FAR NORTHWEST OF THE STATE
WILL PASS NORTH OF THE STATE IN THE NEXT COUPLE OF DAYS. IN
TURN...PRESSURE GRADIENT ACROSS THE AREA WILL TIGHTEN...RESULTING IN
A FURTHER INCREASE OF TRADE WINDS THROUGH EARLY NEXT WEEK. A MID
LEVEL HIGH WILL PERSIST IN THE ISLAND VICINITY...AND WILL KEEP AIR
MASS STABLE OVER THE AREA. LOOK FOR BREEZY TRADE WIND WEATHER IN THE
NEXT FEW DAYS...WITH PASSING LOW CLOUDS AND SHOWERS AFFECTING MAINLY
WINDWARD AREAS. LEE AREAS OF THE SMALLER ISLANDS MAY SEE A LITTLE
SHOWERS AS WELL...DUE TO THE STRONG WINDS.

THE AFOREMENTIONED SURFACE HIGH WILL MOVE TO FAR NORTHEAST OF THE
STATE BY TUESDAY...THEN WEAKEN SOMEWHAT BUT SAG SOUTH CLOSER TO THE
ISLANDS. LATEST MODEL SOLUTIONS ARE A LITTLE MORE IN-LINE WITH EACH
OTHER...AS THE LATEST GFS SOLUTION NOW LEAN BACK TOWARD THE EARLIER
ECMWF SOLUTION. A SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP FAR
WEST OF THE STATE BY THE LATER HALF OF NEXT WEEK...THOUGH THIS
SYSTEM WILL BE CLOSE ENOUGH TO THE ISLANDS SUCH THAT WINDS WILL TURN
A LITTLE MORE SOUTHEASTERLY. MEANWHILE...A SURFACE HIGH PRESSURE
WILL CONTINUE NORTHEAST OF THE AREA...AND WILL KEEP RATHER ROBUST
WINDS OVER THE ISLANDS. MODEL SOLUTIONS ALSO INDICATE A POSSIBLE
INCREASE IN MOISTURE IN THE ISLAND VICINITY...THOUGH AIR MASS MAY
REMAIN MARGINALLY STABLE. LOOKS LIKE TRADE WIND WEATHER MAY PERSIST
FOR THE LATER HALF OF NEXT WEEK OVER THE STATE...WITH SLIGHTLY
WEAKER WINDS AND MORE MOISTURE. DUE TO VARIATIONS IN THE FORECAST
BETWEEN MODEL RUNS...CONFIDENCE IN THE FORECAST REMAINS SOMEWHAT LOW
AT THIS TIME.

&&

.AVIATION...
WE ARE MONITORING AN AREA OF CLOUDS AND SHOWERS 90 MILES UPWIND OF
MAUI THAT MAY WARRANT AN AIRMET SIERRA FOR MTN OBSC AFTER 08Z FOR
PRIMARILY MOLOKAI AND MAUI.

ELSEWHERE...VFR WILL BE THE PREVAILING FLYING COND FOR THE OVERNIGHT
HOURS. THE ISOL SHOWERS NOW WILL INCREASE SLIGHTLY OVERNIGHT BRIEFLY
LOWERING THE CEILINGS AND VIS TO MVFR CONDS. THESE SHOWERS WILL
FAVOR THE WINDWARD AND MTN AREAS WITH A STRAY SHOWER OR TWO
DRIFTING INTO THE LEE SECTIONS OF THE SMALLER ISLANDS. BUT IT WILL
BE MOSTLY DRY THERE. BKN TO OVC LO CLOUDS OVER THE KONA SLOPES...
COAST...AND ADJ WATERS WILL GRADUALLY BE CLEARING OUT THROUGH 12Z.

DUE TO A MOD TO STRONG TRADE WIND FLOW WITH A MODERATELY STRONG
INVERSION BETWEEN 6 AND 7K FEET...AIRMET TANGO FOR LO LVL TURB BLO
080 WILL CONT THRU AT LEAST 16Z FOR ALL ISLANDS.

&&

.MARINE...
AS THE WINDS ARE EXPECTED TO INCREASE A NOTCH THROUGH SUNDAY...WITH
NEAR GALE FORCE WINDS IN CHANNELS AROUND MAUI AND THE BIG
ISLAND...SMALL CRAFT WIND CONDITIONS WILL PREVAIL OVER ALL COASTAL
WATERS. ADDITIONALLY...THE COMBINED SEAS WILL ALSO APPROACH THE
SMALL CRAFT THRESHOLD OF 10 FEET...WITH SEAS DOMINATED BY
SHORT-PERIOD WIND WAVES. THEREFORE SMALL CRAFT ADVISORY CONTINUES
FOR ALL COASTAL WATERS THROUGH EARLY TUESDAY.

THE STRONG TRADE WINDS WILL ALSO BRING NEAR ADVISORY LEVEL SURF
ALONG EAST FACING SHORES THROUGH EARLY NEXT WEEK. SURF WILL BE ROUGH
ALONG EAST FACING SHORES FOR THE NEXT SEVERAL DAYS REGARDLESS DUE TO
THE STRONG WINDS. A NEW SMALL NORTHWEST SWELLS ARE EXPECTED ON
SUNDAY AND TUESDAY...THOUGH SURF HEIGHTS FROM THE SWELL WILL REMAIN
BELOW ADVISORY LEVELS. A LONG-PERIOD SOUTH-SOUTHWEST SWELL WILL
ARRIVE LATE OVER THE WEEKEND AND PEAK AROUND TUESDAY...THEN SLOWLY
DIMINISH THROUGH THE WEEK...WITH SURF ALONG SOUTH FACING SHORES
APPROACHING ADVISORY LEVELS DURING THE PEAK OF THE SWELL.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN WATERS.

&&

$$

AVIATION...LAU
REST...HUI





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