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Beaufort Wind Scale

Sir Francis Beaufort (1774–1857), a captain in the British Admiralty created the first version of his famous wind scales in 1806 for his own use. The Sea Conditions column describes observations used by mariners to estimate wind speeds since, prior to the advent of GPS, obtaining precise speeds from a (possibly) moving vessel was impossible.












Beaufort Number Wind speed Description Wave Height Sea Conditions Land Conditions
kt km/h mph m/s m/ft
0 0 0 0 0-0.2 Calm 0/0 Flat Calm, smoke rises vertically
1 1-3 1-6 1-3 0.3-1.5 Light Air 0.1/0.33 Ripples without crests Wind motion visible in smoke
2 4-6 7-11 4-7 1.6-3.3 Light
Breeze
0.2/0.66 Small wavelets, crests of glassy appearance, not breaking Wind felt on exposed skin, leaves rustle
3 7-10 12-19 8-12 3.4-5.4 Gentle
Breeze
0.6/2 Large wavelets, crests begin to break, scattered whitecaps Leaves and smaller twigs in constant motion
4 11-16 20-29 13-18 5.5-7.9 Moderate
Breeze
1/3.3 Small waves Dust and loose paper raised. Small branches begin to move.
5 17-21 30-39 19-24 8.0-10.7 Fresh
Breeze
2/6.6 Moderate (1.2 m) longer waves, some foam and spray Smaller trees sway
6 22-27 40-50 25-31 10.8-13.8 Strong
Breeze
3/9.9 Large waves with foam crests and some spray Large branches in motion, whistling heard in overhead wires, umbrella use becomes difficult
7 28-33 51-62 32-38 13.9-17.1 Near
Gale
4/13.1 Sea heaps up and foam begins to streak Whole trees in motion, effort needed to walk against the wind
8 34-40 63-75 39-46 17.2-20.7 Gale 5.5/18 Moderately high waves with breaking crests forming spindrift, streaks of foam Twigs broken from trees, cars veer on road
9 41-47 76-87 47-54 20.8-24.4 Strong
Gale
7/23 High waves (2.75 m) with dense foam, wave crests start to roll over, considerable spray Light structure damage
10 48-55 88-102 55-63 24.5-28.4 Storm 9/29.5 Very high waves, sea surface is white with considerable tumbling, visibility reduced Trees uprooted. Considerable structural damage
11 56-63 103-117 64-72 28.5-32.6 Violent
Storm
11.5/37.7 Exceptionally high waves Widespread structural damage
12 >63 >117 >72 >32.7 Hurricane 14+/46+ Huge waves, air filled with foam and spray, sea completely white with driving spray, visibility very greatly reduced Massive and widespread damage to structures

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