Storm warning

{{Short description|Meteorological warning about a coming storm}}

{{About||other uses|Storm Warning (disambiguation)|weather warnings in general|Weather warning}}

{{Redirect|Storm watch||Stormwatch (disambiguation)}}

{{distinguish|Tropical storm warning|Severe thunderstorm warning}}

{{globalize|date=September 2017}}

File:Weather Warning Flag (United States).svg

At sea, a storm warning is a warning issued by the National Weather Service of the United States when winds between {{convert|48|and|63|kn|km/h mph}} are occurring or predicted to occur soon. The winds must not be associated with a tropical cyclone.{{cite web|title=Storm Warning|url=http://www.weather.gov/glossary/index.php?word=Storm+Warning|work=Glossary - National Weather Service|accessdate=21 July 2011|author=National Weather Service}} If the winds are associated with a tropical cyclone, a tropical storm warning will be substituted for the storm warning and less severe gale warning.

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 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 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 {{convert|115|mph|kn|abbr=on}} will always result in new issuance of an extreme wind warning shortly before their onset, typically right before the eyewall of a major hurricane makes landfall, but possibly as a substitute for a severe thunderstorm warning in an extreme derecho event. The only exception is that if the extreme winds are associated with a tornado, a tornado warning (or more likely a tornado emergency) will be issued instead.