|
Beaufort Number |
Description |
Wind Speed |
Wave Height |
Sea Conditions |
Land Conditions |
|||
|
mph |
km/h |
kts |
m |
ft |
||||
|
0 |
Calm |
< 1 |
< 1 |
< 1 |
0 |
0 |
Flat |
Calm. Smoke rises vertically |
|
1 |
Light air |
1 - 3 |
1.1 - 5.5 |
1 - 2 |
0 - 0.2 |
0 - 1 |
Ripples without crests |
Wind motion visible in smoke |
|
2 |
Light breeze |
4 - 7 |
5.6 - 11 |
3 - 6 |
0.2 - 0.5 |
1 - 2 |
Small wavelets. Crests of glassy appearance, not breaking |
Wind felt on exposed skin. Leaves rustle |
|
3 |
Gentle breeze |
8 - 12 |
12 - 19 |
7 - 10 |
0.5 - 1 |
2 - 3.5 |
Large wavelets. Crests begin to break; scattered whitecaps |
Leaves and smaller twigs in constant motion |
|
4 |
Moderate breeze |
13 - 17 |
20 - 28 |
11 - 15 |
1 - 2 |
3.5 - 6 |
Small waves with breaking crests. Fairly frequent white horses |
Dust and loose paper raised. Small branches begin to move |
|
5 |
Fresh breeze |
18 - 24 |
29 - 38 |
16 - 20 |
2 - 3 |
6 - 9 |
Moderate waves of some length. Many white horses. Small amounts of spray |
Branches of a moderate size move. Small trees begin to sway |
|
6 |
Strong breeze |
25 - 30 |
39 - 49 |
21 - 26 |
3 - 4 |
9 - 13 |
Long waves begin to form. White foam crests are very frequent. Some airborne spray is present |
Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic rubbish bins tip over |
|
7 |
High wind, moderate gale, near gale |
31 - 38 |
50 - 61 |
27 - 33 |
4 - 5.5 |
13 - 19 |
Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray |
Whole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors. |
|
8 |
Gale, fresh gale |
39 - 46 |
62 - 74 |
34 - 40 |
5.5 - 7.5 |
17.2 - 20.7 |
Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray |
Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded |
|
9 |
Strong gale |
47 - 54 |
75 - 88 |
41 - 47 |
7 - 10 |
23 - 32 |
High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility |
Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies |
|
10 |
Storm, whole gale |
55 - 63 |
89 - 102 |
48 - 55 |
9 - 12.5 |
29 - 41 |
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 |
Trees are broken off or uprooted, saplings bent and deformed. Poorly attached asphalt shingles and shingles in poor condition peel off roofs |
|
11 |
Violent storm |
64 - 72 |
103 - 117 |
56 - 63 |
11.5 - 16 |
37 - 52 |
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 |
Widespread damage to vegetation. Many roofing surfaces are damaged; asphalt tiles that have curled up and/or fractured due to age may break away completely |
|
12 |
Hurricane |
≥ 73 |
≥ 118 |
≥ 64 |
≥14 |
≥46 |
Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility |
Very widespread damage to vegetation. Some windows may break; mobile homes and poorly constructed sheds and barns are damaged. Debris may be hurled about |