The Beaufort Scale, used throughout the marine world, has developed over many years since it was first devised by Admiral Francis Beaufort in 1806. Today, the Beaufort scale is defined for seamen in terms of sea state. It's emphasis is more on the observed effect of the wind, rather than the actual wind speed.
Currently :
Force |
Wind |
Wind |
Wave |
||||
---|---|---|---|---|---|---|---|
0 |
|
< 1 |
|
mph |
0 |
|
m |
On Sea : Flat On Land : Calm. Smoke rises vertically
|
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Force |
Wind |
Wind |
Wave |
||||
1 |
|
1 - 3 |
|
mph |
0 - 0.2 |
|
m |
On Sea : Ripples without crests On Land : Wind motion visible in smoke
|
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Force |
Wind |
Wind |
Wave |
||||
2 |
|
4 - 7 |
|
mph |
0.2 - 0.5 |
|
m |
On Sea : Small wavelets. Crests of glassy appearance, not breaking On Land : Wind felt on exposed skin. Leaves rustle
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Force |
Wind |
Wind |
Wave |
||||
3 |
|
8 - 12 |
|
mph |
0.5 - 1 |
|
m |
On Sea : Large wavelets. Crests begin to break; scattered whitecaps On Land : Leaves and smaller twigs in constant motion
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Force |
Wind |
Wind |
Wave |
||||
4 |
|
13 - 17 |
|
mph |
1 - 2 |
|
m |
On Sea : Small waves with breaking crests. Fairly frequent white horses On Land : Dust and loose paper raised. Small branches begin to move
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Force |
Wind |
Wind |
Wave |
||||
5 |
|
18 - 24 |
|
mph |
2 - 3 |
|
m |
On Sea : Moderate waves of some length. Many white horses. Small amounts of spray On Land : Branches of a moderate size move. Small trees begin to sway
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|||||||
Force |
Wind |
Wind |
Wave |
||||
6 |
|
25 - 30 |
|
mph |
3 - 4 |
|
m |
On Sea : Long waves begin to form. White foam crests are very frequent. Some airborne spray is present On Land : Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic rubbish bins tip over
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|||||||
Force |
Wind |
Wind |
Wave |
||||
7 |
|
31 - 38 |
|
mph |
4 - 5.5 |
|
m |
On Sea : Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray On Land : Whole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors
|
|||||||
Force |
Wind |
Wind |
Wave |
||||
8 |
|
39 - 46 |
|
mph |
5.5 - 7.5 |
|
m |
On Sea : Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray On Land : Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded
|
|||||||
Force |
Wind |
Wind |
Wave |
||||
9 |
|
47 - 54 |
|
mph |
7.5 - 10 |
|
m |
On Sea : High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility On Land : Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies
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|||||||
Force |
Wind |
Wind |
Wave |
||||
10 |
|
55 - 63 |
|
mph |
10 - 12.5 |
|
m |
On Sea : 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 On Land : Trees are broken off or uprooted, saplings bent and deformed. Poorly attached asphalt shingles and shingles in poor condition peel off roofs
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|||||||
Force |
Wind |
Wind |
Wave |
||||
11 |
|
64 - 72 |
|
mph |
12.5 - 16 |
|
m |
On Sea : 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 On Land : 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
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Force |
Wind |
Wind |
Wave |
||||
12 |
|
≥ 73 |
|
mph |
≥ 17 |
|
m |
On Sea : Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility On Land : Very widespread damage to vegetation. Some windows may break; mobile homes and poorly constructed sheds and barns are damaged. Debris may be hurled about
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