Beaufort Scale Page
Beaufort number | Description | Wind speed | Wave height | Sea conditions | Land conditions | Associated warning flag |
---|---|---|---|---|---|---|
0 | Calm |
< 1 knot < 1 mph < 2 km/h < 0.5 m/s |
0 ft (0 m) | Sea like a mirror | Smoke rises vertically. | |
1 | Light air | 1-3 knots | 0-1 ft | Ripples with appearance of scales are formed, without foam crests | Direction shown by smoke drift but not by wind vanes. | |
1-3 mph | ||||||
2-5 km/h | 0-0.3 m | |||||
0.5-1.5 m/s | ||||||
2 | Light breeze | 4-6 knots | 1-2 ft | Small wavelets still short but more pronounced; crests have a glassy appearance but do not break | Wind felt on face; leaves rustle; wind vane moved by wind. | |
4-7 mph | ||||||
6-11 km/h | 0.3-0.6 m | |||||
1.6-3.3 m/s | ||||||
3 | Gentle breeze | 7-10 knots | 2-4 ft | Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses | Leaves and small twigs in constant motion; light flags extended. | |
8-12 mph | ||||||
12-19 km/h | 0.6-1.2 m | |||||
3.4-5.5 m/s | ||||||
4 | Moderate breeze | 11-16 knots | 3.5-6 ft | Small waves becoming longer; fairly frequent white horses | Raises dust and loose paper; small branches moved. | |
13-18 mph | ||||||
20-28 km/h | 1-2 m | |||||
5.5-7.9 m/s | ||||||
5 | Fresh breeze | 17-21 knots | 6-10 ft | Moderate waves taking a more pronounced long form; many white horses are formed; chance of some spray | Small trees in leaf begin to sway; crested wavelets form on inland waters. | |
19-24 mph | ||||||
29-38 km/h | 2-3 m | |||||
8-10.7 m/s | ||||||
6 | Strong breeze | 22-27 knots | 9-13 ft | Large waves begin to form; the white foam crests are more extensive everywhere; probably some spray | Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty. |
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25-31 mph | ||||||
39-49 km/h | 3-4 m | |||||
10.8-13.8 m/s | ||||||
7 |
High wind, moderate gale, near gale |
28-33 knots | 13-19 ft | Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind; spindrift begins to be seen | Whole trees in motion; inconvenience felt when walking against the wind. |
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32-38 mph | ||||||
50-61 km/h | 4-5.5 m | |||||
13.9-17.1 m/s | ||||||
8 |
Gale, fresh gale |
34-40 knots | 18-25 ft | Moderately high waves of greater length; edges of crests break into spindrift; foam is blown in well-marked streaks along the direction of the wind | Twigs break off trees; generally impedes progress. |
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39-46 mph | ||||||
62-74 km/h | 5.5-7.5 m | |||||
17.2-20.7 m/s | ||||||
9 | Strong/severe gale | 41-47 knots | 23-32 ft | High waves; dense streaks of foam along the direction of the wind; sea begins to roll; spray affects visibility | Slight structural damage (chimney pots and slates removed). |
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47-54 mph | ||||||
75-88 km/h | 7-10 m | |||||
20.8-24.4 m/s | ||||||
10 |
Storm whole gale |
48-55 knots | 29-41 ft | Very high waves with long overhanging crests; resulting foam in great patches is blown in dense white streaks along the direction of the wind; on the whole the surface of the sea takes on a white appearance; rolling of the sea becomes heavy; visibility affected | Seldom experienced inland; trees uprooted; considerable structural damage. |
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55-63 mph | ||||||
89-102 km/h | 9-12.5 m | |||||
24.5-28.4 m/s | ||||||
11 | Violent storm | 56-63 knots | 37-52 ft | Exceptionally high waves; small- and medium-sized ships might be for a long time lost to view behind the waves; sea is covered with long white patches of foam; everywhere the edges of the wave crests are blown into foam; visibility affected | Very rarely experienced; accompanied by widespread damage. |
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64-72 mph | ||||||
103-117 km/h | 11.5-16 m | |||||
28.5-32.6 m/s | ||||||
12 | Hurricane force | ≥ 64 knots | ≥ 46 ft | The air is filled with foam and spray; sea is completely white with driving spray; visibility very seriously affected | Devastation. |
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≥ 73 mph | ||||||
≥ 118 km/h | ≥ 14 m | |||||
≥ 32.7 m/s |