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Beaufort Wind Scale

The Beaufort scale was long in use as a system for estimating wind speeds. It was introduced in 1805 by Admiral Sir Francis Beaufort (1774-1857) of the British navy to describe wind effects on a fully rigged man-of-war sailing vessel, and it was later extended to include descriptions of effects on land features as well.


Bft Sourroundings Wind Knots km/h mph m/s
0 Smoke rises vertically and the see is mirror smooth calm 0 0 0 0
1 Smokes moves slightly with breeze and shows direction of wind light air 1-3 1-5 1-3 <2
2 You can feel wind on your face and hear the leaves start to rustle light breeze 4-6 6-11 4-7 2-3
3 Smoke will move horizontally and small branches start to sway. Wind extends a light flag gentle breeze 7-10 12-19 8-12 4-5
4 Loose dust or sand on the ground will move and larger branches will sway, loose paper blows around, and fairly frequent whitecaps occur moderate breeze 11-16 20-28 13-18 6-7
5 Surface waves form on water and small trees sway fresh breeze 17-21 29-38 19-24 8-10
6 Trees begin to bend with the force of the wind and causes whistling in telephone wires and some spray on the sea surface strong breeze 22-27 39-49 25-31 11-13
7 large trees sway moderate gale 28-33 50-61 32-38 14-16
8 twigs break from trees, and long streaks of foam appear on the ocean fresh gale 34-40 62-74 39-46 17-20
9 branches break from trees strong gale 41-47 75-88 47-55 21-24
10 weak trees are uprooted, and the sea takes on a white appearance whole galem 48-55 89-102 56-64 25-28
11 widespread damage storm 56-63 103-117 65-73 29-32
12 structural damage on land and storm waves at sea hurricane >46 >118 >74 >33





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