Classification of the winds


Anybody have heard about the Beaufort wind scale, in various weather reports, but without really know what it is. Indeed, except the specialists, only a few persons know the signification of the various graduations of this scale.

The Beaufort wind scale is used by the sailors and the meteorologists to indicate the wind speed. It was invented in 1805 by the Irish hydrograph Francis Beaufort. The original characteristics were modified in 1946 ; the scale used today on sea is presented in the following table. 


Beaufort wind scale Speed in km/h


Effects observed on the sea

0 Under 1 Calm  Sea is like a mirror
1 1 - 5 Light air Ripples with appearance of scales; no foam crests
2 6 - 11 Light breeze Small wavelets; crests of glassy appearance, not breaking
3 12 - 19 Gentle breeze Large wavelets; crests begin to break; scattered whitecaps
4 20 - 28 Moderate breeze Small waves, becoming longer; numerous whitecaps
5 29 - 38 Fresh breeze Moderate waves, taking longer form; many whitecaps; some spray
6 39 - 49 Strong breeze Larger waves forming; whitecaps everywhere; more spray
7 50 - 61 Near gale Sea heaps up; white foam from breaking waves begins to be blown in streaks
8 62 - 74 Gale Moderately high waves of greater length; edges of crests begin to break into spindrift; foam is blown in well-marked streaks
9 75 - 88 Strong gale High waves; sea begins to roll; dense streaks of foam; spray may begin to reduce visibility
10 89 - 102 Storm Very high waves with overhanging crests; sea takes white appearance as foam is blown in very dense streaks; rolling is heavy and visibility is reduced
11 103 - 117 Violent storm Exceptionally high waves; sea covered with white foam patches; visibility further reduced
12 Over 118 Hurricane Air filled with foam; sea completely white with driving spray; visibility greatly reduced





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