Beaufort scale

Beaufort number Description Wind speed Sea conditions
km/h kts
0 Calm < 1 < 1 Flat.
1 Light air 1.1 – 5.5 1 – 2 Ripples without crests.
2 Light breeze 5.6 – 11 3 – 6 Small wavelets. Crests of glassy appearance, not breaking
3 Gentle breeze 12 – 19 7 – 10 Large wavelets. Crests begin to break; scattered whitecaps
4 Moderate breeze 20 – 28 11 – 15 Small waves with breaking crests. Fairly frequent white horses.
5 Fresh breeze 29 – 38 16 – 20 Moderate waves of some length. Many white horses. Small amounts of spray.
6 Strong breeze 39 – 49 21 – 26 Long waves begin to form. White foam crests are very frequent. Some airborne spray is present.
7 High wind, Moderate gale, Near gale 50 – 61 27 – 33 Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray.
8 Gale, Fresh gale 62 – 74 34 – 40 Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray.
9 Strong gale 75 – 88 41 – 47 High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility.
10 Storm, Whole gale 89 – 102 48 – 55 Very high waves with overhanging crests. Large patches of foam from wave crests give the sea a white appearance. Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility.
11 Violent storm 103 – 117 56 – 63 Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility.
12 Hurricane ≥ 118 ≥ 64 Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility.
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