- Beaufort wind scale
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ranges of wind speeds which are reported as nautical miles per hour in marine weather forecasts while general weather forecasts report wind speeds in kilometres per hour. Beaufort values 13 to 17 have wind speeds in knots at 72-80, 81-89, 90-99, 100-109 and 110-118 without any verbal descriptions of sea conditions:Beaufort scale -- State of air -- Wind speed (knots) -- Wind speed (km/h) -- Sea conditions0 -- Calm -- 0-1 -- 0-1Like a mirror1 -- Light airs -- 1-3 -- 1-5Ripples2 -- Light breeze -- 4-6 -- 6-11Small wavelets3 -- Gentle breeze -- 7-10 -- 12-19Small waves, fairly frequent whitecaps4 -- Moderate breeze -- 11-16 -- 20-29Small waves, fairly frequent whitecaps5 -- Fresh breeze -- 17-21 -- 30-39Moderate waves, many whitecaps6 -- Strong breeze -- 22-27 -- 40-50Large waves begin to form, white foam crests more extensive every-where7 -- Near gale -- 28-33 -- 51-618 -- Fresh gale -- 34-40 -- 62-74Moderately high waves of greater length, edges of crests break into spin-drift, foam blown in well-marked streaks along direction of wind9 -- Strong gale -- 41-47 -- 75-86High waves, dense streaks of foam blown along direction of wind, crests of waves begin to topple, tumble and roll over, spray may affect visibility10 -- Whole gale -- 48-55 -- 87-100Very high waves with long overhanging crests, foam in great patches blown in dense white streaks along direction of wind, surface on the whole becomes white, tumbling of the sea becomes heavy and shock-like, visibility affected11 -- Storm -- 56-63 -- 101-117Exceptionally high waves, small and medium-sized vessels may be lost to view for long periods, sea completely covered with long white patches of foam along direction of wind, everywhere the edges of wave crests are blown into froth, visibility affected12 -- Hurricane -- >63 -- >117Air filled with foam and spray, sea completely white with driving spray, visibility very seriously affected
Dictionary of ichthyology. 2009.