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Scale of threat levels

for South Central and Southeast Wisconsin
Wind and Wave Threat
Hazard Map Threat Levels Safety & Impact

The "Marine Wind and Wave Hazard Map" depicts the local threat to mariners for specified coastal water areas based on the adverse affects of wind and sea state.

Marine Wind & Sea Threat Level

Threat Level Descriptions

Extreme

"An Extreme Threat to Life and Property Aboard Marine Vessels, Especially Small Craft, from Marine Winds/Seas."

Storm-force prevailing winds with extreme combined seas.  Sustained winds of 48 knots or greater (Beaufort Scale 10+). Winds of this strength, combined with a long fetch and duration, would be capable of generating waves of 20 to 30 feet or more. Visibility very seriously affected from dense blowing foam and spray. Freezing temperatures would create very hazardous freezing spray conditions. Small craft should stay in port. Conditions typical for a "Storm Warning".

High

"A High Threat to Life and Property Aboard Marine Vessels, Especially Small Craft, from Marine Winds/Seas."

Gale-force prevailing winds with very large combined seas.  Sustained  winds of 34 - 47 knots (Beaufort Scale 8 - 9). Winds of this strength, combined with a long fetch and duration, would be capable of generating waves of 10 to 20 feet. Visibility becoming affected by blowing foam and spray. Freezing temperatures could create hazardous freezing spray conditions. Small craft encouraged to seek safe harbor or stay in port. Conditions typical for a "Gale Warning".

Moderate

"A Moderate Threat to Life and Property Aboard Marine Vessels, Especially Small Craft, from Marine Winds/Seas."

Strong prevailing winds and large combined seas.  Sustained winds of 22 - 33 knots (Beaufort Scale 6 - 7). Winds of this strength, combined with a long fetch and duration, would be capable of generating waves of 5 to 15 feet. Conditions typical for a "Small Craft Advisory".

Low

"A Low Threat to Life and Property Aboard Marine Vessels, Especially Small Craft, from Marine Winds/Seas."

Prevailing winds and combined seas are moderate. Sustained winds of 17 - 21 knots (Beaufort Scale 5). Winds of this strength, combined with a long fetch and duration, would be capable of generating waves of 3 to 6 feet. Conditions typical for a "Small Craft Advisory".
Very Low
" A Very Low Threat to Life and Property Aboard Marine Vessels, Especially Small Craft, from Marine Winds/Seas."

Prevailing winds and combined seas becoming moderate.  Sustained winds around 14 - 16 knots (Beaufort Scale 4). Winds of this strength, combined with a long fetch and duration, would be capable of generating waves of capable of driving seas of 3 to 4 feet. Conditions typical for "Small Craft To Exercise Caution".

Non-Threatening
" No Discernable Threat to Life and Property Aboard Marine Vessels, Especially Small Craft, from Marine Winds/Seas."

Prevailing winds and combined seas are non-threatening.

Note: Combined seas are the combination of wind waves and swells as they relate to sea height.  The height (or significant wave height) is defined as the average height of the one third highest waves.

Guide to Sea State and Winds

Beaufort Force 0  Beaufort Force 1  Beaufort Force 2
Beaufort Force 3  Beaufort Force 4  Beaufort Force 5
Beaufort Force 6  Beaufort Force 7  Beaufort Force 8
Beaufort Force 9  Beaufort Force 10  Beaufort Force 11
Beaufort Force 12  Ocean and Lake Swells

Determining Likelihood

  • NOAA's National Weather Service
  • Milwaukee/Sullivan, WI Weather Forecast Office
  • N3533 Hardscrabble Road
  • Dousman, WI 53118
  • 414-744-8000
  • Page Author: MKX Webmaster
  • Web Master's E-mail: w-mkx.webmaster@noaa.gov
  • Page last modified: 2-Nov-2005 10:23 PM UTC
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