At sea, a storm warning is a warning issued by the

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

of the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

when winds between are occurring or predicted to occur soon. The winds must not be associated with a tropical cyclone. If the winds are associated with a tropical cyclone, a

tropical storm warning Tropical cyclone warnings and watches are alerts issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local pop ...

will be substituted for the storm warning and less severe

gale warning A ''gale warning'' is an alert issued by national weather forecasting agencies around the world in an event that maritime locations currently or imminently experiencing winds of gale force on the Beaufort scale. Gale warnings (and gale watch ...

. In US maritime warning flag systems, a red square flag with a black square taking up the middle ninth of the flag is used to indicate a storm warning (the use of two such flags denotes a

hurricane force wind warning A hurricane force wind warning is a warning issued by the National Weather Service of the United States when sustained winds or frequent gusts of 64 knots (118 km/h, 74 mph) or greater are either being observed or are predicted to occur. The wind ...

or a hurricane warning). The same flag as a storm warning is used to indicate a tropical storm warning. On land, the National Weather Service issues a 'high wind warning' (Specific Area Message Encoding code: HWW) for storm-force winds, which also encompasses the lesser

gale-force The Beaufort scale ( ) is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. It was devised in 1805 by Francis Beaufort a Hydrography, hydrographer in the Roy ...

and greater hurricane force winds. In most cases, the warning applies to winds of 40-114 mph for at least 1 hour; or any gusts of 58–114 miles per hour on land unless a tropical storm warning, blizzard warning, winter storm warning, severe thunderstorm warning, or dust storm warning covers the phenomenon. Winds in excess of will always result in new issuance of an

extreme wind warning An extreme wind warning (Specific Area Message Encoding, SAME code EWW) is an alert issued by the National Weather Service for areas on land that will experience sustained surface winds or greater within one hour. As of 2024, it has only been u ...

shortly before their onset, typically right before the

eyewall The eye is a region of mostly calm weather at the center of a tropical cyclone. The eye of a storm is a roughly circular area, typically in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weath ...

of a major

hurricane A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its ...

makes landfall, but possibly as a substitute for a

severe thunderstorm warning A severe thunderstorm warning ( SAME code: SVR) is a type of public warning for severe weather that is issued by weather forecasting agencies worldwide when one or more severe thunderstorms have been detected by Doppler weather radar, observed ...

in an extreme

derecho A ''derecho'' (, from , 'straight') is a widespread, long-lived, straight-line wind storm that is associated with a fast-moving group of Severe weather#Categories, severe thunderstorms known as a mesoscale convective system. Derechos cause Bea ...

event. The only exception is that if the extreme winds are associated with a tornado, a

tornado warning A tornado warning ( SAME code: TOR) is a public warning that is issued by weather forecasting agencies to an area in the direct path of a tornado, or a severe thunderstorm capable of producing one, and advises individuals in that area to take c ...

(or more likely a

tornado emergency A tornado emergency is an enhanced version of a tornado warning, which is used by the National Weather Service (NWS) in the United States during imminent, significant tornado occurrences. Although it is not a new warning type from the NWS, issue ...

) will be issued instead.

Weather Warning Flags (United States)

File:Small Craft Advisory Flag (U.S).svg, Small Craft Advisory Flag File:Gale Warning Flag (U.S).svg, Gale Warning Flags File:Storm Warning Flag (U.S).svg, Storm Warning Flag File:Hurricane Warning Flags (U.S).svg, Hurricane Warning Flags

Example

The following is an example of a storm warning issued by the National Weather Service office in

Seattle, Washington Seattle ( ) is the List of municipalities in Washington, most populous city in the U.S. state of Washington (state), Washington and in the Pacific Northwest region of North America. With a population of 780,995 in 2024, it is the List of Unit ...

246 
WHUS76 KSEW 180451
MWWSEW

URGENT - MARINE WEATHER MESSAGE
NATIONAL WEATHER SERVICE SEATTLE WA
851 PM PST SUN JAN 17 2010

PZZ150-153-156-170-173-176-181300-
/O.UPG.KSEW.GL.W.0087.000000T0000Z-100118T2300Z/
/O.NEW.KSEW.SR.W.0003.100118T0451Z-100118T2000Z/
COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-
COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE OUT 10 NM-
COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER OUT 10 NM-
COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-
COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-
COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER 10 TO
60 NM-
851 PM PST SUN JAN 17 2010

...STORM WARNING IN EFFECT UNTIL NOON PST MONDAY...

THE NATIONAL WEATHER SERVICE IN SEATTLE HAS ISSUED A STORM
WARNING...WHICH IS IN EFFECT UNTIL NOON PST MONDAY. THE GALE
WARNING IS NO LONGER IN EFFECT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A STORM WARNING MEANS WINDS OF 48 TO 63 KNOTS ARE IMMINENT OR
OCCURRING. RECREATIONAL BOATERS SHOULD REMAIN IN PORT OR TAKE
SHELTER UNTIL THE WINDS AND WAVES SUBSIDE. COMMERCIAL VESSELS
SHOULD PREPARE FOR VERY STRONG WINDS AND DANGEROUS SEA
CONDITIONS...AND CONSIDER REMAINING IN PORT OR TAKING SHELTER IN
PORT UNTIL WINDS AND WAVES SUBSIDE.

&&

$$

References

External links

National Weather Service
{{SevWea nav Weather warnings and advisories

Weather Warning Flags (United States)

Example

See also

References

External links