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Marine Thunderstorm Wind Gust Threat

The "Marine Thunderstorm Wind Hazard Map" depicts the local threat of strong to severe wind gusts associated with thunderstorms for specified marine areas.  It is based on the likelihood that strong to severe wind gusts will occur with marine thunderstorms combined with the anticipated speed of the greatest gusts.    

Marine Thunderstorm Wind Threat Level

Threat Level Descriptions

Extreme

"An Extreme Threat to Life and Property Aboard Small Marine Craft from Wind Gusts Associated with Thunderstorms."

Within 12 miles of a location, a moderate likelihood or greater (16% probability or greater) of very severe/violent thunderstorm wind gusts (64 knots or greater).  

AND/OR...a high likelihood or greater (26% probability or greater) of severe thunderstorm wind gusts (between 50 knots and 63 knots). 

AND/OR...a very high likelihood (36% or greater) of strong thunderstorm wind gusts (between 34 and 49 knots).

High

"A High Threat to Life and Property Aboard Small Marine Craft from Wind Gusts Associated with Thunderstorms." 

Within 12 miles of a location, a low likelihood (6% to 15% probability) of very severe/violent thunderstorm wind gusts (64 knots or greater).  

AND/OR...a moderate likelihood (16% to 25% probability) of severe thunderstorm wind gusts (between 50 knots and 63 knots).

AND/OR...a high likelihood (26% to 35% probability) of strong thunderstorm wind gusts (between 34 and 49 knots).

Moderate

"A Moderate Threat to Life and Property Aboard Small Marine Craft from Wind Gusts Associated with Thunderstorms."

Within 12 miles of a location, a very low likelihood (2% to 5% probability) of very severe/violent thunderstorm wind gusts (64 knots or greater).  

AND/OR...a low likelihood (6% to 15% probability) of severe thunderstorm wind gusts (between 50 knots and 63 knots). 

AND/OR...a moderate likelihood (16% to 25% probability) of strong thunderstorm wind gusts (between 34 and 49 knots).

Low

"A Low Threat to Life and Property Aboard Small Marine Craft from Wind Gusts Associated with Thunderstorms."

Within 12 miles of a location, a very low likelihood (2% to 5% probability) of severe thunderstorm wind gusts (between 50 knots and 63 knots).

AND/OR...a low likelihood (6% to 15% probability) of strong thunderstorm wind gusts (between 34 and 49 knots).

Very Low
" A Very Low Threat to Life and Property Aboard Small Marine Craft from Wind Gusts Associated with Thunderstorms."

Within 12 miles of a location, a very low likelihood (2% to 5% probability) of strong thunderstorm wind gusts (between 34 and 49 knots).

Non-Threatening
" No Discernable Threat to Life and Property Aboard Small Marine Craft from Wind Gusts Associated with Thunderstorms."

Within 12 miles of a location, environmental conditions do not support the occurrence of strong to severe wind gusts from thunderstorms.     

Note: Since small craft are vulnerable to rapid, gusty increases in wind speed, mariners should not allow strong to severe thunderstorms to get between them and safe harbor.    

Strong Wind Gusts - Thunderstorm wind gusts between 34 knots and 49 knots.

Severe Wind Gusts - Severe thunderstorm wind gusts between 50 knots and 63 knots. 

Very Severe/Violent Wind Gusts - Severe thunderstorm wind gusts between 64 knots and 79 knots, but in worse case situations may exceed 80 knots.