Beaufort wind scale: translation
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 conditions
0 -- Calm -- 0-1 -- 0-1
Like a mirror
1 -- Light airs -- 1-3 -- 1-5
Ripples
2 -- Light breeze -- 4-6 -- 6-11
Small wavelets
3 -- Gentle breeze -- 7-10 -- 12-19
Small waves, fairly frequent whitecaps
4 -- Moderate breeze -- 11-16 -- 20-29
Small waves, fairly frequent whitecaps
5 -- Fresh breeze -- 17-21 -- 30-39
Moderate waves, many whitecaps
6 -- Strong breeze -- 22-27 -- 40-50
Large waves begin to form, white foam crests more extensive every-where
7 -- Near gale -- 28-33 -- 51-61
Sea heaps up, white foam from breaking waves blown in streaks along direction of wind
8 -- Fresh gale -- 34-40 -- 62-74
Moderately high waves of greater length, edges of crests break into spin-drift, foam blown in well-marked streaks along direction of wind
9 -- Strong gale -- 41-47 -- 75-86
High waves, dense streaks of foam blown along direction of wind, crests of waves begin to topple, tumble and roll over, spray may affect visibility
10 -- Whole gale -- 48-55 -- 87-100
Very 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 affected
11 -- Storm -- 56-63 -- 101-117
Exceptionally 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 affected
12 -- Hurricane -- >63 -- >117
Air filled with foam and spray, sea completely white with driving spray, visibility very seriously affected