Marine Definitions

Coastal Waters Forecast (CWF): The marine forecast for areas, including bays, harbors, and sounds, from a line approximating the mean high water mark (average height of high water over a 19-year period) along the mainland or near shore islands extending out to 40 NM in Guam and Hawai`i.
Combined Seas: Generally referred to as SEAS. Used to describe the combination or interaction of wind waves and swell in which the separate components are not distinguished. This includes the case when swell is negligible or is not considered in describing sea state. Specifically, SEAS = where S is the height of the swell and W is the height of the wind wave. When used, SEAS should be considered as being the same as the significant wave height.
Fetch: The across water distance over which waves are generated by winds having an approximately constant direction and speed.
Gale Warning: A warning of sustained winds or frequent gusts from 34 to 47 KT inclusive, predicted or occurring, not generated by a tropical cyclone.
Gust: A fluctuation of the mean wind speed with variations of 10 KT or more between peaks and lulls.
High Seas Forecasts (HSF): Marine forecasts for the major oceans of the world. In Hawaii, High Seas Forecasts are issued for the North Pacific...from the Equator to 30N, between 140W and 160E longitude, and the South Pacific, from the Equator to 25S, between 120W and 160E.
Hurricane (also known as typhoon in the western Pacific Ocean): A tropical cyclone generating sustained winds of 64 KT or greater.
Hurricane Force Wind Warning: A warning for sustained winds or frequent gusts of 64 KT or greater, either predicted or occurring, NOT associated with a tropical cyclone.
Knot: Unit of speed used in navigation, equal to 1 NM per hour or about 1.15 statute miles per hour.
Nautical Mile: Unit of distance, equal to about 1.15 statute miles (length of 1 minute of latitude).
Offshore Waters Forecast (OFF): A marine forecast for that portion of the oceans, gulfs, and seas beyond the coastal waters extending to a specified distance from the coastline, to a specified depth contour, or covering an area defined by specific latitude and longitude points. In Hawaii, the Offshore Waters extends out to 240 NM from shore, south of 30N.
Rip Currents: Narrow channels of water flowing seaward from the beach through areas of breaking waves.
Seas: Used to describe the combination or interaction of wind waves and swell in which the separate components are not distinguished. This includes the case when swell is negligible or is not considered in describing sea state. Specifically, SEAS = where S is the height of the swell and W is the height of the wind wave. When used, SEAS should be considered as being the same as the significant wave height.
Significant Wave Height: The average height (trough to crest) of the one-third highest waves. An experienced observer will most frequently report heights equivalent to the average of the highest one-third of all waves observed.
Small Craft Advisory in Hawai`i: An advisory for areas included in the Hawaiian coastal waters forecast for sustained winds or frequent gusts from 20 to 33 KT inclusive and/or for seas of 10 FT or more depending on wave period and direction.
Special Marine Warning (SMW): A warning of potentially hazardous weather conditions usually of short duration (less than 2 hours) producing wind speeds of 34 KT or more affecting areas included in a coastal waters forecast.
Storm Warning: A warning of sustained winds or frequent gusts of 48 to 63 KT inclusive not generated by a tropical cyclone.
Sustained Wind: The wind speed obtained in the U.S. by averaging observed values over a period of at least 1 minute.
Surf Zone Forecast (SRF): A routine or event driven forecast geared toward non-boating marine users issued for an area extending from the near-coastal point where waves begin breaking to the high tide point on shore. In Hawaii this is used for the surf observations and forecast product, issued at least three times daily.
Swell: Wind-generated waves that have traveled out of their generating area. Swell characteristically exhibits smoother, more regular and uniform crests and a longer period than wind waves.
Tropical Cyclone: A generic term for a synoptic scale cyclone originating over tropical or subtropical waters with organized convection and definite cyclonic surface wind circulation.
Tropical Depression: A tropical cyclone in which the maximum sustained surface wind is 33 KT or less.
Tropical Storm: A tropical cyclone in which the maximum sustained surface wind ranges from 34 to 63 KT inclusive.
Coordinated Universal Time (UTC): The standard international time reference based on the time at 0° longitude (Greenwich Meridian).
Waterspout: A rotating column of air over water whose circulation extends to the surface.
Wave Period: Time, in seconds, between the passage of consecutive wave crests past a fixed point.
Wave Spectrum: The distribution of wave energy with respect to wave frequency or period. Wave spectra assist in differentiating between wind waves and swell.
Wind Waves: May be referred to as WAVES. Waves generated from the action of wind on the local water surface.