Special marine warning

A special marine warning (SAME code SMW) is a warning issued by the U.S. National Weather Service for potentially hazardous marine weather conditions usually of short duration (up to 2 hours) producing sustained marine thunderstorm winds or associated gusts of 34 knots or greater; or hail 3/4 inch or more in diameter; or waterspouts affecting areas included in a coastal waters forecast, a nearshore marine forecast, or a Great Lakes open lakes forecast that is not adequately covered by existing marine warnings. It is also used for short duration mesoscale events such as a strong cold front, gravity wave, squall line, etc., lasting less than 2 hours and producing winds or gusts of 34 knots or greater.[1]

Example

Below is a sample warning issued by the National Weather Service office in Houston, Texas.[2]

WHUS54 KHGX 122204
SMWHGX
GMZ335-122245- /O.NEW.KHGX.MA.W.0136.160612T2204Z-160612T2245Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SPECIAL MARINE WARNING
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
504 PM CDT SUN JUN 12 2016

THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS ISSUED A

* SPECIAL MARINE WARNING FOR...
  GALVESTON BAY...

* UNTIL 545 PM CDT

* AT 504 PM CDT...A SEVERE THUNDERSTORM CAPABLE OF PRODUCING WATERSPOUTS WAS LOCATED OVER
  NORTHEASTERN GALVESTON BAY...MOVING EAST AT 15 KNOTS.

  HAZARD...WATERSPOUTS AND WIND GUSTS 34 KNOTS OR GREATER.

  SOURCE...RADAR INDICATED.

  IMPACT...WATERSPOUTS CAN EASILY OVERTURN BOATS AND CREATE LOCALLY HAZARDOUS SEAS.
  SMALL CRAFT COULD BE DAMAGED IN BRIEFLY HIGHER WINDS AND SUDDENLY HIGHER WAVES.

* LOCATIONS IMPACTED INCLUDE...
  GALVESTON BAY...TRINITY BAY...NORTHWESTERN EAST GALVESTON BAY...EAGLE POINT AND SMITH POINT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THUNDERSTORMS CAN PRODUCE SUDDEN WATERSPOUTS. WATERSPOUTS CAN EASILY OVERTURN BOATS AND CREATE
LOCALLY HAZARDOUS SEAS. SEEK SAFE HARBOR IMMEDIATELY.

FREQUENT LIGHTNING IS OCCURRING WITH THIS STORM. IF CAUGHT ON THE OPEN WATER STAY BELOW DECK
IF POSSIBLE...KEEP AWAY FROM UNGROUNDED METAL OBJECTS.

&&

LAT...LON 2974 9467 2965 9468 2954 9474 2957 9463 2952 9461 2941 9491 2943 9491 2946 9497
2949 9495 2950 9499 2955 9504 2960 9500
2964 9503 2968 9502 2971 9495 2970 9491
2967 9491 2968 9489 2977 9482 2980 9472

TIME...MOT...LOC 2204Z 260DEG 13KT 2955 9488
WATERSPOUT...POSSIBLE
HAIL...0.00IN WIND...>34KTS

$$

References
  1. "Special Marine Warning Definition". NWS. Retrieved 28 September 2013.
  2. "Special Marine Warnings" (PDF). National Weather Service. Retrieved June 7, 2018.
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