The Beaufort scale (Bft) is a scalazur division of wind strength into 13 strength ranges from 0 – calm to 12 – hurricane, based not on exact measurements but on the observed effects of the wind. It is named after Sir Francis Beaufort and is a widely used system for describing wind strength.
According to the 1946 revision of the Beaufort scale, the following relationship exists between wind speed v and Beaufort force B [Bft] (commercially rounded):
Wind- force | Meaning | avarage Windspeed | |||
in Bft | kn | m/s | km/h | mph | |
0 | Calm | 0 – < 1 | 0,0 – < 0,3 | 0 – 1 | 0 – < 1,2 |
---|---|---|---|---|---|
1 | Light air | 1 – < 4 | 0,3 – < 1,6 | 1 – 5 | 1,2 – < 4,6 |
2 | Light breeze | 4 – < 7 | 1,6 – < 3,4 | 6 – 11 | 4,6 – < 8,1 |
3 | Gentle breeze | 7 – < 11 | 3,4 – < 5,5 | 12 – 19 | 8,1 – < 12,7 |
4 | Moderate breeze | 11 – < 16 | 5,5 – < 8,0 | 20 – 28 | 12,7 – < 18,4 |
5 | Fresh breeze | 16 – < 22 | 8,0 – < 10,8 | 29 – 38 | 18,4 – < 25,3 |
6 | Strong breeze | 22 – < 28 | 10,8 – < 13,9 | 39 – 49 | 25,3 – < 32,2 |
7 | High wind | 28 – < 34 | 13,9 – < 17,2 | 50 – 61 | 32,2 – < 39,1 |
8 | Gale | 34 – < 41 | 17,2 – < 20,8 | 62 – 74 | 39,1 – < 47,2 |
9 | Strong gale | 41 – < 48 | 20,8 – < 24,5 | 75 – 88 | 47,2 – < 55,2 |
10 | Storm, whole gale | 48 – < 56 | 24,5 – < 28,5 | 89 – 102 | 55,2 – < 64,4 |
11 | Violent storm | 56 – < 64 | 28,5 – < 32,7 | 103 – 117 | 64,4 – < 73,6 |
12 | Hurricane | ≥ 64 | ≥ 32,7 | ≥ 118 | ≥ 73,6 |