NOUS41 KWBC 181345
Service Change Notice 17-51
National Weather Service Headquarters, Silver Spring, MD
945 AM EDT Tue Apr 18 2017
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
Other NWS Partners and Employees
FROM: Allison Allen
Chief, Marine, Tropical, and Tsunami Services Branch
SUBJECT: Impact Based Warnings for Special Marine Warnings
(SMW) and Marine Weather Statements (MWS) for WFOs
Honolulu and Guam will become operational May 18, 2017
Effective Thursday, May 18, 2017, Weather Forecast Offices (WFO)
Honolulu and Guam will transition to the Impact Based Warning
(IBW) format for Special Marine Warnings SMW and MWS that follow
the SMW. WSO Pago Pago will transition at a later to be
determined date. These products will convey information about
associated impacts, specific hazards expected, and recommended
actions both within bullet statements and as part of the tag
This is the first step for WFO Guam and WFO Honolulu in a
transition to IBW for all short-fused hazards products. This
format change will help improve the communication of crucial
decision support and risk assessment information to partners and
users within the guidelines of governing policy and the existing
The NWS has been evaluating the IBW format since 2013 at
conterminous United States (CONUS) WFOs. Successes with this
format along with comments received from the public, partners
and social scientists have all been positive.
In the new version of these products, hazard, source and impact
will be identified.
HAZARD...WATERSPOUTS and WIND GUSTS 34 KNOTS OR GREATER.
IMPACT...WATERSPOUTS CAN QUICKLY FORM AND CAPSIZE BOATS...DAMAGE
VESSELS AND CREATE SUDDENLY HIGHER WAVES. MAKE SURE ALL ON
BOARD ARE IN A SECURE LOCATION AND WEARING LIFE JACKETS. EXPECT
WIND GUSTS IN EXCESS OF 34 KNOTS...SUDDENLY HIGHER
WAVES...FREQUENT LIGHTNING AND HEAVY DOWNPOURS.
WFO Honolulu and WFO Guam will also include tags at the end of
the SMWs and MWSs that follow-up SMWs, which designates the
threat expected: Waterspout, Wind or Hail.
This change will include the experimental addition of a forecast
tag labeled "WATERSPOUT" at the bottom of SMWs and MWSs noting
that follow-up SMWs will transition to operational for WFO
Honolulu and WFO Guam. The transition to operational will occur
for WSO Pago Pago at a later date. A Service Change Notice will
be issued at that time.
The permanent addition of Waterspout, Hail and Wind adds plain
text lines below the product after the dollar sign, dollar sign
and the LAT...LON information.
[dollar sign, dollar sign]
LAT...LON 4298 8242 4261 8252 4261 8253 4276 8248
TIME...MOT...LOC 1400Z 263DEG 40KT 4284 8289 4244 8291
[dollar sign, dollar sign]
The additional information is also found elsewhere within the
product, simply summarized on the lines below. If a waterspout
threat does not exist, the waterspout tag line is omitted.
For details on this product enhancement, please see:
For more information, please contact:
NWS Headquarters, Silver Spring, MD 20910
National Public Information Statements are online at: