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000
FXPQ60 PGUM 230220
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
1220 PM CHST SAT AUG 23 2014

.UPDATE...
PGUA WSR-88D SHOWS SHOWERS AND THUNDERSTORMS MOVING THROUGH
MARIANAS WATERS INCLUDING ROTA...TINIAN AND SAIPAN. THE MORNING
SOUNDING SHOWS A PWAT OF 2.17 AND A SIGNIFICANT K-INDEX. UPDATED
THE FORECASTS TO EXPAND ISOLATED THUNDERSTORM COVERAGE OVER ALL
THE MARIANAS FORECAST ZONES.

&&

.PREV DISCUSSION... /ISSUED 750 AM CHST SAT AUG 23 2014/

MARIANAS SYNOPSIS...
PGUA WSR-88D SHOWS A LINE OF SHOWERS MOVING THROUGH GUAM WATERS
AND THE OCEAN SOUTH OF GUAM. OTHERWISE...ONLY ISOLATED SHOWERS AND
THUNDERSTORMS ARE SEEN. THE VAD WIND PROFILE REVEALS SOUTHEAST
WINDS OF 3 TO 8 KNOTS THROUGH THE LOWEST 3 THOUSAND FEET OF THE
AIR.

DISCUSSION...
THUNDERSTORMS ARE DIMINISHING AS THE UPPER-LEVEL LOW CONTINUES TO
MOVE TO THE NORTH. THE THUNDERSTORMS IN THE FORECAST TODAY ARE
MORE DUE TO ISLAND HEATING OVER GUAM AS WE ARE EXPECTING CLEARER
SKIES AND LIGHT WINDS. OTHERWISE...PARTLY CLOUDY SKIES WILL
CONTINUE THROUGH THE FIRST HALF OF NEXT WEEK. CHANGING WIND
DIRECTIONS IN THE SECOND HALF OF NEXT WEEK SUGGEST A TROUGH
PASSAGE. THE GFS40 DID NOT HAVE AN APPRECIABLE INCREASE IN RAIN.
THE ECMWF-HIRES DID HAVE A SLIGHT INCREASE. WILL HAVE TO ALLOW
THIS PERIOD TO COME A LITTLE CLOSER AND WATCH SUCCESSIVE MODEL
RUNS. AT SOME POINT WE MAY NEED TO ADD MOSTLY CLOUDY SKIES AND
PERHAPS EVEN SCATTERED SHOWERS.

COMBINED SEAS OF 1 TO 2 FEET WILL DOUBLE TO BETWEEN 2 AND 4 FEET
MONDAY. THEY ARE THEN EXPECTED TO SUBSIDE TO BETWEEN 1 AND 2 FEET
AGAIN BY LATE IN THE WEEK. ALL OF THESE ARE WAY BELOW ADVISORY
CRITERIA...SO NO ADVISORIES ARE FORESEEN THROUGH THE REST OF
AUGUST.

EASTERN MICRONESIA...
A MILD PATTERN CONTINUES OVER EASTERN MICRONESIA. A RIDGING PATTERN
REMAINS OVER KOSRAE AND POHNPEI PROMOTING A LIGHT AND VARIABLE WIND
REGIME THROUGH THE PERIOD. ONLY WEAK TROUGHING WILL AFFECT MAJURO
TONIGHT THROUGH THE WEEKEND WITH ONLY MOSTLY CLOUDY CONDITIONS WITH
ISOLATED SHOWERS EXPECTED.

WESTERN MICRONESIA...
THE MONSOON TROUGH REMAINS NORTH OF ALL THREE FORECAST POINTS.
MONSOONAL FLOW IS ESTABLISHED ACROSS THE REGION. CONVERGING WINDS TO
THE SOUTH OF THE TROUGH BROUGHT SCATTERED SHOWERS TO KOROR THIS
MORNING. THIS COMPLEX OF SHOWERS WILL CONTINUE TO AFFECT KOROR
THROUGH THE DAY BEFORE MOVING WEST AND DISSIPATING. BASED ON
SATELLITE AND MODEL GUIDANCE...ONLY MADE SHORT TERM MODIFICATIONS TO
THE INHERITED FORECAST. INCREASED CLOUD COVER AT KOROR ALONG WITH
SCATTERED SHOWERS THROUGH TODAY. INCREASED CLOUD COVER AT BOTH YAP
AND CHUUK. BEGINNING TONIGHT...EXPECT DRIER CONDITIONS AT ALL 3
LOCALES AS A WEAKER WIND REGIME TAKES HOLD THROUGH THE MIDDLE OF
NEXT WEEK.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

DEVITA/ZIOBRO







000
FXPQ60 PGUM 222150
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
750 AM CHST SAT AUG 23 2014

.MARIANAS SYNOPSIS...
PGUA WSR-88D SHOWS A LINE OF SHOWERS MOVING THROUGH GUAM WATERS
AND THE OCEAN SOUTH OF GUAM. OTHERWISE...ONLY ISOLATED SHOWERS AND
THUNDERSTORMS ARE SEEN. THE VAD WIND PROFILE REVEALS SOUTHEAST
WINDS OF 3 TO 8 KNOTS THROUGH THE LOWEST 3 THOUSAND FEET OF THE
AIR.

&&

.DISCUSSION...
THUNDERSTORMS ARE DIMINISHING AS THE UPPER-LEVEL LOW CONTINUES TO
MOVE TO THE NORTH. THE THUNDERSTORMS IN THE FORECAST TODAY ARE
MORE DUE TO ISLAND HEATING OVER GUAM AS WE ARE EXPECTING CLEARER
SKIES AND LIGHT WINDS. OTHERWISE...PARTLY CLOUDY SKIES WILL
CONTINUE THROUGH THE FIRST HALF OF NEXT WEEK. CHANGING WIND
DIRECTIONS IN THE SECOND HALF OF NEXT WEEK SUGGEST A TROUGH
PASSAGE. THE GFS40 DID NOT HAVE AN APPRECIABLE INCREASE IN RAIN.
THE ECMWF-HIRES DID HAVE A SLIGHT INCREASE. WILL HAVE TO ALLOW
THIS PERIOD TO COME A LITTLE CLOSER AND WATCH SUCCESSIVE MODEL
RUNS. AT SOME POINT WE MAY NEED TO ADD MOSTLY CLOUDY SKIES AND
PERHAPS EVEN SCATTERED SHOWERS.

COMBINED SEAS OF 1 TO 2 FEET WILL DOUBLE TO BETWEEN 2 AND 4 FEET
MONDAY. THEY ARE THEN EXPECTED TO SUBSIDE TO BETWEEN 1 AND 2 FEET
AGAIN BY LATE IN THE WEEK. ALL OF THESE ARE WAY BELOW ADVISORY
CRITERIA...SO NO ADVISORIES ARE FORESEEN THROUGH THE REST OF
AUGUST.

&&

.EASTERN MICRONESIA...
A MILD PATTERN CONTINUES OVER EASTERN MICRONESIA. A RIDGING PATTERN
REMAINS OVER KOSRAE AND POHNPEI PROMOTING A LIGHT AND VARIABLE WIND
REGIME THROUGH THE PERIOD. ONLY WEAK TROUGHING WILL AFFECT MAJURO
TONIGHT THROUGH THE WEEKEND WITH ONLY MOSTLY CLOUDY CONDITIONS WITH
ISOLATED SHOWERS EXPECTED.

&&

.WESTERN MICRONESIA...
THE MONSOON TROUGH REMAINS NORTH OF ALL THREE FORECAST POINTS.
MONSOONAL FLOW IS ESTABLISHED ACROSS THE REGION. CONVERGING WINDS TO
THE SOUTH OF THE TROUGH BROUGHT SCATTERED SHOWERS TO KOROR THIS
MORNING. THIS COMPLEX OF SHOWERS WILL CONTINUE TO AFFECT KOROR
THROUGH THE DAY BEFORE MOVING WEST AND DISSIPATING. BASED ON
SATELLITE AND MODEL GUIDANCE...ONLY MADE SHORT TERM MODIFICATIONS TO
THE INHERITED FORECAST. INCREASED CLOUD COVER AT KOROR ALONG WITH
SCATTERED SHOWERS THROUGH TODAY. INCREASED CLOUD COVER AT BOTH YAP
AND CHUUK. BEGINNING TONIGHT...EXPECT DRIER CONDITIONS AT ALL 3
LOCALES AS A WEAKER WIND REGIME TAKES HOLD THROUGH THE MIDDLE OF
NEXT WEEK.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

STANKO/KLEESCHULTE








000
FXPQ60 PGUM 220554
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
354 PM CHST FRI AUG 22 2014

.MARIANAS SYNOPSIS...
IT HAS BEEN A CLASSIC DAY FOR ISLAND THUNDERSTORMS ON GUAM--LIGHT
WINDS DOWN THE LENGTH OF THE ISLAND...SOME SOLAR HEATING...AND
PLENTY OF MOISTURE. HIT-AND-RUN THUNDERSTORMS HAVE BEEN POPPING
RANDOMLY UP AND DOWN SINCE 1030 AM...AND CURRENTLY WHILE ONE IS
WEAKENING OVER ANDERSEN AFB...ANOTHER IS POPPING UP AROUND
INARAJAN IN SOUTHERN GUAM.

OTHERWISE...RADAR AND SATELLITE SHOW ISOLATED SHOWERS AROUND THE
MARIANAS...WITH A COUPLE OF ISOLATED THUNDERSTORMS WELL SOUTH OF
GUAM.

&&

.DISCUSSION...
ONE MORE ISLAND THUNDERSTORM DAY IS POSSIBLE FOR GUAM SATURDAY AS
WINDS WILL BE VERY LIGHT...BUT LIKELY FROM THE SOUTHEAST WHICH IS
LESS FAVORABLE FOR ISLAND-GENERATED CONVECTION. EVEN SO...HAVE
GONE WITH ISOLATED AFTERNOON THUNDER FOR GUAM FOR SATURDAY. OTHER
THAN THAT...THE REST OF THE FORECAST IS UNCHANGED--PARTLY CLOUDY
WITH ISOLATED SHOWERS AND GENERALLY LIGHT EAST WINDS.

&&

.EASTERN MICRONESIA...
A DIFFUSE SURFACE TROUGH IS PRODUCING CLOUDINESS FROM EAST OF MAJURO
TO BEYOND THE DATE LINE. THE MONSOON TROUGH PASSES TO THE NORTH OF
KOSRAE AND POHNPEI...BUT THE PATTERN OF RIDGING ON THE SOUTH SIDE OF
THE TROUGH IS PROMOTING WEAK MONSOONAL FLOW OVER THESE LOCALES.
FORECAST CLOSELY FOLLOWS PERSISTENCE. MADE SOME MINOR SHORT TERM
WIND ADJUSTMENTS BASED ON THE LATEST ASCAT IMAGERY. STILL EXPECT
WEAK AND CHAOTIC WIND FLOW REGIME TO PERSIST THROUGH THE FORECAST
PERIOD. A WEAK WIND FLOW PATTERN MEANS LOW-LEVEL FORCING WILL BE
WEAK AS WELL...THUS DO NOT EXPECT SCATTERED SHOWERS OVER ANY OF
THE FORECAST LOCALES THROUGH DAY 5.

&&

.WESTERN MICRONESIA...
MONSOON TROUGH PASSES TO THE NORTH OF ALL 3 FORECAST POINTS.
MONSOONAL FLOW HAS BECOME ESTABLISHED FOR THE TIME BEING OVER
CHUUK...YAP AND KOROR. DID MAKE SHORT TERM WIND ADJUSTMENTS TO THE
CHUUK AND YAP FORECASTS TO FACTOR IN THE MONSOONAL FLOW...BUT THEN
WEAKER WIND FLOW REGIME MOVES BACK IN FROM THE EAST. FORECASTS FOR
CHUUK AND YAP REMAIN RELATIVELY QUIET. HOWEVER...MADE SEVERAL
ADJUSTMENTS TO THE KOROR FORECASTS WHERE MONSOONAL FLOW IS MORE
DEEPLY ENTRENCHED. LATEST ASCAT IMAGERY AND METARS FROM KOROR
INDICATE STRONGER WINDS THAN EARLIER FORECAST...SO HAVE INCREASED
WINDS AND SEAS THERE ON DAYS 1 AND 2. COLD CLOUD TOPS WERE SEEN IN
IR SATELLITE IMAGERY TODAY IN THE VICINITY OF KOROR. GFS TIME-HEIGHT
CROSS SECTION SHOWS SIGNIFICANT OMEGA OVER KOROR JUST FOR TONIGHT.
HAVE ACCORDINGLY ADDED THUNDER FOR TONIGHT TO THE KOROR FORECAST.
LONG TERM FORECAST FOR ALL 3 LOCALES REMAINS VIRTUALLY UNCHANGED AND
QUIET AS WEAKER WIND FLOW REGIME TAKES HOLD DAYS 3 THROUGH 5.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.

&&

$$

MIDDLEBROOKE/MCELROY







000
FXPQ60 PGUM 212200
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
800 AM CHST FRI AUG 22 2014

.MARIANAS SYNOPSIS...
PGUA WSR-88D SHOWS ISOLATED SHOWERS MOVING THROUGH THE MARIANAS
WATERS. SATELLITE SHOWS AN UPPER-LEVEL LOW NORTHEAST OF THE
MARIANAS WHICH IS PRODUCING A FEW THUNDERSTORMS ACROSS THE AREA.
THE VAD WIND PROFILE REVEALS 4 TO 9 KNOT EAST WINDS THROUGH THE
LOWEST 12 THOUSAND FEET OF THE AIR.

&&

.DISCUSSION...
MAIN FORECAST PROBLEM IS THE UPPER-LEVEL LOW AND WHETHER OR NOT IT
WILL DESTABILIZE THE ATMOSPHERE ENOUGH FOR THUNDERSTORMS IN THE
FORECAST ZONES. THERE ARE THUNDERSTORMS JUST WEST OF SAIPAN WATERS
SO LEFT THEM IN TODAY. ONCE THE UPPER-LEVEL LOW PULLS FAR ENOUGH
AWAY WE CAN TAKE THE THUNDERSTORMS OUT. INHERITED GRIDS HAD THE
THUNDERSTORMS ENDING AFTER TODAY. WITH THE LOW MOVING A BIT NORTH
THIS ALSO LOOKED GOOD AT THIS TIME.

WAVES WILL REMAIN BETWEEN 2 AND 3 FEET WITH A FEW 4 FOOT VALUES.
NO SIGNIFICANT WAVES ARE FORESEEN THROUGH THE MIDDLE OF NEXT WEEK.

&&

.EASTERN MICRONESIA...
NO MAJOR CHANGES MADE TO INHERITED FORECAST. A WEAK CIRCULATION AND
ASSOCIATED TROUGH CONTINUES TO WEAKEN AND DRIFT WEST-NORTHWESTWARD
AWAY FROM KWAJALEIN AND KOSRAE WITH DRIER CONDITIONS PUSHING INTO
MAJURO AND KOSRAE AS EXPECTED. EXTENDED MOSTLY CLOUDY CONDITIONS
THROUGH TODAY AT POHNPEI AS THE WEATHER ASSOCIATED WITH THIS SYSTEM
CONTINUES TO DECREASE AND MOVES NORTH OF POHNPEI. RIDGING IS
BUILDING INTO THE REGION AND WILL DOMINATE THE PATTERN OVER THE NEXT
FEW DAYS.

&&

.WESTERN MICRONESIA...
INCREASING CONVERGENCE OVER THE REGION FROM CHUUK TO NEAR KOROR WILL
RESULT IN A BIT MORE CONVECTION THAN EXPECTED. JUST TO THE EAST OF
CHUUK...AN AREA OF SHOWERS AND THUNDERSTORMS CONTINUES TO DEVELOP
THIS MORNING. DO NOT EXPECT THIS COMPLEX TO REMAIN IN TACT AS IT
APPROACHES CLOSER TO CHUUK...BUT MAY RESULT IN MOSTLY CLOUDY
CONDITIONS WITH ISOLATED SHOWERS AND THUNDERSTORMS POSSIBLE LATER IN
THE MORNING. FOR KOROR...A SMALL BAND OF SHOWERS HAS DEVELOPED TO
THE NORTHEAST OF THE ISLAND AND A LARGER AREA OF SHOWERS AND
THUNDERSTORMS IS SEEN TO THE SOUTH. THESE SHOWERS WILL CONTINUE TO
DEVELOP THROUGH THE MORNING BUT THE THUNDERSTORMS TO THE SOUTH ARE
EXPECTED TO REMAIN SOUTH OF KOROR WATERS. BASED ON THIS...INCREASED
CLOUD COVER OVER KOROR FOR TODAY AND THOUGHT IT WOULD BE PRUDENT TO
ADD A SLIGHT CHANCE OF THUNDERSTORMS TO THE FORECAST. A RIDGE OF
HIGH PRESSURE IS NOW IN PLACE SOUTHEAST OF YAP AND IS EXPECTED TO
MAINTAIN PLEASANT CONDITIONS THERE THROUGH THE BEGINNING OF NEXT
WEEK. THE RIDGE WILL ALSO BRING PLEASANT CONDITIONS BACK TO CHUUK
AND KOROR TONIGHT THROUGH EARLY IN THE WEEK.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

STANKO/KLEESCHULTE







000
FXPQ60 PGUM 210820
AFDPQ

AREA FORECAST DISCUSSION...ADDED MICRONESIAN DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
605 PM CHST THU AUG 21 2014

.MARIANAS SYNOPSIS...
AN ELONGATED AND EXTREMELY WEAK SURFACE TROUGH IS EVIDENT ON
VISIBLE SATELLITE IMAGERY OVER THE MARIANAS. WINDS WERE LIGHT WNW
EARLIER ON GUAM AND ESE ON TINIAN AND SAIPAN...BUT WINDS HAVE
BECOME LIGHT AND VARIABLE IN THE LAST HOUR OR TWO. MEANWHILE...AN
UPPER-LEVEL LOW IS SEEN IN WATER VAPOR IMAGERY CENTERED AROUND
12N151E...MOVING WEST.

&&

.DISCUSSION...
MODELS SHOW THE WEAK CIRCULATION BREAKING DOWN OVERNIGHT INTO A WEAK
TROUGH ON FRIDAY...WHILE THE WESTWARD-MOVING UPPER LOW OPENS INTO A
TROUGH AS IT PASSES OVER THE ISLANDS ON FRIDAY. WITH ADEQUATE
MOISTURE STILL IN THE MID-LEVELS...THIS IS ENOUGH TO KEEP ISOLATED
THUNDERSTORMS IN THE FORECAST TONIGHT...AND HAVE EXTENDED THEM
THROUGH FRIDAY AS THE UPPER TROUGH MOVES BY AND ISLAND HEATING WITH
LIGHT WINDS PROVIDES AN EXTRA BOOST. THE REST OF THE FORECAST
REMAINS THE SAME AS PREVIOUS...PARTLY CLOUDY SKIES AND ISOLATED
SHOWERS--UNUSUALLY DRY FOR AUGUST.

&&

.EASTERN MICRONESIA...
A SURFACE TROUGH RUNNING FROM ABOUT 11N165E TO 1N154E IS WEAKENING
AS IT MOVES WESTWARD. THE MODELS INDICATE HIGH PRESSURE IS BUILDING
JUST EAST OF THE TROUGH FOR A SHORT WHILE UNTIL OTHER TROUGHS MOVE
IN AT INTERVALS BEHIND IT. TONIGHT AT MAJURO THERE IS A SURFACE
TROUGH JUST TO THE EAST FOLLOWED BY A CONVERGENCE ZONE. THE MODELS
SHOW THE CONVERGENCE ZONE AND WEAK TROUGHS AFFECTING MAJURO AFTER
TONIGHT. THIS EVENING KOSRAE IS ON THE TRAILING EDGE OF CLOUD COVER
AROUND THE WEAKENING TROUGH WITH A RIDGE TO THE EAST. THE MODELS
INDICATE THE RIDGE WILL AFFECT KOSRAE FRIDAY AND FRIDAY NIGHT...THEN
WEAK TROUGHS AND WEAK RIDGES WILL FOLLOW. POHNPEI IS EXPERIENCING
THE WEAKENED TROUGH THEN FOLLOWED BY ADDITIONAL WEAKENING FRIDAY
WITH RIDGING TO THE SOUTH.

&&

.WESTERN MICRONESIA...
NO MAJOR CHANGES TO THE INHERITED FORECAST FOR WESTERN MICRONESIA.
THE MONSOON TROUGH NORTH OF 10N CONTINUES TO BE THE PRIMARY WEATHER
INFLUENCE OVER THE REGION. MAINLY LIGHT WINDS ARE EXPECTED ACROSS
THE REGION. CHUUK IS ON THE EDGE OF CLOUD COVER WITH THUNDERSTORMS
NEARBY TO THE WEST. WHAT FOLLOWS AT CHUUK WILL BE WEATHER SIMILAR TO
POHNPEI. YAP IS IN AN AREA OF CONVERGENCE BETWEEN HIGH PRESSURE TO
THE SOUTH AND A CIRCULATION TO THE NORTHEAST. A RIDGING PATTERN IS
EXPECTED TO BE NEAR KOROR THROUGH THE WEEKEND.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

MIDDLEBROOKE/DEVITA










000
FXPQ60 PGUM 210544
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
344 PM CHST THU AUG 21 2014

.MARIANAS SYNOPSIS...
AN ELONGATED AND EXTREMELY WEAK SURFACE TROUGH IS EVIDENT ON
VISIBLE SATELLITE IMAGERY OVER THE MARIANAS. WINDS WERE LIGHT WNW
EARLIER ON GUAM AND ESE ON TINIAN AND SAIPAN...BUT WINDS HAVE
BECOME LIGHT AND VARIABLE IN THE LAST HOUR OE TWO. MEANWHILE...AN
UPPER-LEVEL LOW IS SEEN IN WATER VAPOR IMAGERY CENTERED AROUND
12N151E...MOVING WEST.

&&

.DISCUSSION...
MODELS SHOW THE WEAK CIRCULATION BREAKING DOWN OVERNIGHT INTO A
WEAK TROUGH ON FRIDAY...WHILE THE WESTWARD-MOVING UPPER LOW OPENS
INTO A TROUGH AS IT PASSES OVER THE ISLANDS ON FRIDAY. WITH
ADEQUATE MOISTURE STILL IN THE MID-LEVELS...THIS IS IS ENOUGH TO
KEEP ISOLATED THUNDERSTORMS IN THE FORECAST TONIGHT...AND HAVE
EXTENDED THEM THROUGH FRIDAY AS THE UPPER TROUGH MOVES BY AND
ISLAND HEATING WITH LIGHT WINDS PROVIDES AN EXTRA BOOST. THE REST
OF THE FORECAST REMAINS THE SAME AS PREVIOUS...PARTLY CLOUDY SKIES
AND ISOLATED SHOWERS--UNUSUALLY DRY FOR AUGUST.

&&

.EASTERN MICRONESIA...
WILL BE ADDED WHEN AVAILABLE.

&&

.WESTERN MICRONESIA...
WILL BE ADDED WHEN AVAILABLE.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

MIDDLEBROOKE/DEVITA







000
FXPQ60 PGUM 202122
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
722 AM CHST THU AUG 21 2014

.MARIANAS SYNOPSIS...LIGHT WINDS AND MOSTLY CLOUDY SKIES
PREVAILED OVER THE MARIANAS THIS MORNING. A FEW AREAS OF SHOWERS
AND THUNDERSTORMS DEVELOPED MAINLY OVER THE COASTAL AREAS THIS
MORNING. EXPECT ISOLATED SHOWERS AND THUNDERSTORMS THROUGH
TONIGHT AS A WEAK CIRCULATION PASSES THROUGH THE MARIANAS.

&&

.DISCUSSION...
LITTLE CHANGE MADE TO THE FORECAST WITH THE EXCEPTION OF UPDATING
THE WIND IN A FEW SPOTS. A NEUTRAL POINT WAS OVER THE AREA THIS
MORNING AND LIGHT AND VARIABLE WINDS PREVAILED OVER THE AREA AS A
RESULT. SCATTEROMETER DATA SHOWS A CIRCULATION LOCATED TO THE
SOUTHEAST OF GUAM. IT REMAINS RATHER WEAK AND MODELS KEEP IT THAT
WAY WHEN IT PASSES THROUGH THE LOCAL AREA.

THE MODELS TODAY AGREE A BIT MORE ON THE TRACK OF THE CIRCULATION
COMPARED TO PREVIOUS DAYS. GFS...GFS-ENSEMBLE...ECMWF AND NAVGEM
SHOW THE CIRCULATION PASSING OVER OR CLOSE TO GUAM ON FRIDAY.

EXPECT NORTHERLY WINDS TODAY BECOMING SOUTHEAST FRIDAY AS THE LOW
TREKS ACROSS THE MARIANAS. WIND SPEEDS WILL REMAIN LIGHT AND WIND
DIRECTIONS MAY BECOME VARIABLE AT TIMES.

THUNDERSTORMS WERE SEEN OVER THE MARIANAS WATERS JUST AROUND
SUNRISE. WITH FAVORABLE UPPER-LEVEL CONDITIONS AND SLIGHT SURFACE
WIND CONVERGENCE... FEEL THUNDERSTORMS ARE AGAIN POSSIBLE THROUGH
TONIGHT. BECAUSE OF THE LIGHT WIND REGIME OVER THE AREA ANY
SHOWER OR THUNDERSTORM THAT DOES FORM MAY BRING BRIEF PONDING OF
WATER IN CERTAIN LOCATIONS. THIS OCCURRED WEDNESDAY AFTERNOON
WHEN A FEW AREAS RECEIVED AROUND ONE INCH OF RAINFALL.

&&

.MARINE...
AN EAST TRADE-WIND SWELL OF 2 TO 3 FEET CAN BE EXPECTED THROUGH
THE WEEK. THE RIP CURRENT RISK WILL BE LOW THROUGH THE FORECAST.

&&

.EASTERN MICRONESIA...
A SURFACE TROUGH REMAINS OVER PORTIONS OF EASTERN MICRONESIA THIS
MORNING. SCATTERED SHOWERS MOVED IN TO MAJURO AND KOSRAE EARLY THIS
MORNING AND WILL CONTINUE OVER PORTIONS OF THE MARSHALL ISLANDS AND
KOSRAE STATE THROUGH THE DAY. EXPECT SHOWERS TO DECREASE TO ISOLATED
AT KOSRAE NEAR NOON AND AT MAJURO A LITTLE LATER IN THE AFTERNOON...
WITH DRIER CONDITIONS MOVING IN TO BOTH LOCATIONS FRIDAY AS THE
TROUGH AND ASSOCIATED CONVERGENCE CONTINUE TO DRIFT WESTWARD. MODELS
SHOW THE TROUGH WEAKENING AS IT CONTINUES WESTWARD RESULTING IN ONLY
AN INCREASE IN CLOUD COVER FOR POHNPEI THIS AFTERNOON. GENERALLY
LIGHT AND VARIABLE WINDS ARE LIKELY ACROSS THE REGION THROUGH THE
WEEKEND.

&&

.WESTERN MICRONESIA...
NO MAJOR CHANGES TO THE INHERITED FORECAST FOR WESTERN MICRONESIA.
THE MONSOON TROUGH NORTH OF 10N CONTINUES TO BE THE PRIMARY
INFLUENCE OVER THE REGION AND IS EXPECTED TO MAINTAIN LIGHT
SOUTHWEST TO WEST WINDS OVER YAP...KOROR AND CHUUK THROUGH THE
WEEKEND. THE ONLY CHANGES MADE ARE IN THE SHORT TERM AT CHUUK. AN
AREA OF SHOWERS AND THUNDERSTORMS REMAINS OVER THE SOUTHERN
PERIPHERY OF CHUUK WATERS RESULTING IN CONTINUING MENTION OF A
SLIGHT CHANCE OF THUNDERSTORMS THERE THROUGH TODAY.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

ZIOBRO/KLEESCHULTE







000
FXPQ60 PGUM 200657
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
457 PM CHST WED AUG 20 2014

.MARIANAS SYNOPSIS...
LATEST ASCAT ANALYSIS INDICATES A WEAK MONSOON TROUGH STILL PASSES
JUST SOUTH OF GUAM NEAR 12N. A WEAK CIRCULATION IS EMBEDDED IN THE
TROUGH CLOSE TO 12N150E. AN MCS ON THE NORTHWEST SIDE OF THE
CIRCULATION AFFECTED GUAM EARLIER THIS AFTERNOON...BUT THE
CONVECTION IS TAPERING OFF.

&&

.DISCUSSION...
MCS THAT FLARED UP EARLIER HAS PERTURBED THE WIND FIELDS IN THE
VICINITY OF GUAM AND SAIPAN...SO HAVE ADJUSTED WIND GRIDS TO
MAINTAIN LIGHT AND VARIABLE FORECAST WORDING FOR THIS EVENING.
OTHERWISE...FORECAST CLOSELY FOLLOWS PERSISTENCE WITH SOME MINOR
TWEAKS TO WIND FIELDS DAYS 3 AND 4. BACKED FLOW DURING THIS TIME
FRAME FROM SOUTH TO SOUTHEAST IN LINE WITH MODEL GUIDANCE
CONSENSUS. SHORT TERM MODEL GUIDANCE AND SATELLITE TRENDS SUGGEST
BEST AREA OF LOW-LEVEL CONVERGENCE ASSOCIATED WITH THE WEAK
MONSOON DEPRESSION SOUTHEAST OF GUAM WILL BE IN THE DEVELOPING
MONSOON TAIL OFF THE THE WEST OF THE FORECAST ZONES. HAVE
ACCORDINGLY KEPT SCATTERED SHOWERS OUT OF THE FORECAST THROUGH
DAY 7. GFS40 TIME-HEIGHT CROSS SECTION HINTS AT POSSIBLE DEEP
CONVECTION OVER/NEAR GUAM ON FRI AND SAT...BUT SITUATION LOOKS
MARGINAL DUE TO MID-LEVEL DRYING. WILL HOLD OFF ON ADDING ISLAND
THUNDER FOR GUAM TO THE FORECAST FOR NOW. UNSETTLED WEATHER
PATTERN WILL PERSIST THROUGH DAY 10 AS MOIST EAST TO SOUTHEAST
LOW-LEVEL WIND FLOW PERSISTS. WEAK DISTURBANCES COULD PRODUCE
SCATTERED SHOWERS FROM TIME TO TIME...BUT IT IS TOO EARLY TO
IDENTIFY ANY RELEVANT SYSTEMS.

&&

.MARINE...
NEARLY STEADY STATE MARINE CONDITIONS CONTINUE. COMBINED SEAS ARE
STILL HOVERING IN THE 2 TO 3-FOOT RANGE. LOW RIP CURRENT RISK
REMAINS A GOOD BET THROUGH THE FORECAST PERIOD.

&&

.EASTERN MICRONESIA...
A SURFACE TROUGH CONTINUES TO GENERATE SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE MARSHALL ISLANDS NORTH OF MAJURO.
MEANWHILE...DRY WEATHER IS FOUND AT KOSRAE AND POHNPEI. THIS TROUGH
WILL GRADUALLY SHIFT WEST TOWARDS KOSRAE TONIGHT AND THURSDAY...SO
ISOLATED THUNDERSTORMS WERE ADDED THERE THROUGH THURSDAY NIGHT.
DRIER WEATHER WILL BUILD IN BEHIND THE TROUGH AT MAJURO BY FRIDAY.
MODELS PROG THIS TROUGH TO WEAKEN THROUGH THURSDAY NIGHT PASSING
OVER KOSRAE AND THEN TOWARDS POHNPEI. ONLY ISOLATED SHOWERS ARE
EXPECTED AT POHNPEI THROUGH WEEKEND. GENERALLY LIGHT AND VARIABLE
WINDS WILL PERSIST ACROSS THE REGION INTO THE WEEKEND.

&&

.WESTERN MICRONESIA...
A WEAK MONSOON TROUGH EXTENDING WEST TO EAST JUST NORTH OF 10N WILL
MAINTAIN LIGHT SOUTHWEST TO WEST...AND AT TIMES VARIABLE...WINDS
THE NEXT FEW DAYS AT KOROR...YAP AND CHUUK. SHOWERY WEATHER NEAR
YAP HAS DISSIPATED SO FORECAST SHOWS IMPROVEMENT IN THE NEAR-TERM.
AN AREA OF SHOWERS AND THUNDERSTORMS SOUTHEAST OF CHUUK WILL PASS
NEARBY TO THE SOUTH OVERNIGHT SO A SLIGHT CHANCE OF THUNDERSTORMS
WAS ADDED THERE FOR TONIGHT. OTHERWISE...NO MAJOR WEATHER FEATURES
ARE EXPECTED AT THE THREE LOCATIONS NEXT FEW DAYS.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

MCELROY/M.AYDLETT/SIMPSON









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