Beaufort scale

The Beaufort Scale is used to measure wind speed and is laid out in the table below.

Beaufort Force Windspeed (Knots) Description Sea Condition
0 0 Calm Sea like a mirror
1 1 – 3 Light Air Ripples but without foam crests
2 4 – 6 Light Breeze Small wavelets. Crests do not break.
3 7 – 10 Gentle Breeze Large wavelets. Perhaps scattered white horses
4 11 – 16 Moderate Breeze Small waves. Fairly frequent white horses.
5 17 – 21 Fresh Breeze Moderate waves, many white horses
6 22 – 27 Strong Breeze Large waves begin to form; white foam crests, probably spray
7 28 – 33 Near Gale Sea heaps up and white foam blown in streaks along the direction of the wind
8 34 – 40 Gale Moderately high waves, crests begin to break into spindrift
9 41 – 47 Strong Gale High waves. Dense foam along the direction of the wind. Crests of waves begin to roll over. Spray may affect visibility
10 48 – 55 Storm Very high waves with long overhanging crests. The surface of the sea takes a white appearance. The tumbling of the sea becomes heavy and shock like. Visibility affected
11 56 – 63 Violent Storm Exceptionally high waves. The sea is completely covered with long white patches of foam lying in the direction of the wind. Visibility affected
12 64+ Hurricane The air is filled with foam and spray. Sea completely white with driving spray. Visibility very seriously affected.