Beaufort-scale

The Beaufort scale describes wind intensity based mainly on observed sea conditions.

Beaufort number and description Wind speed [kn] Wind speed [km/h] Land conditions Sea conditions
0
Calm
<1 <1 Smoke rises vertically.
Lika a mirror.
1
Light air
1-3 1-5 Wind motion visible in smoke.
Ripples without crests.
2
Light breeze
4-7 6-11 Wind felt on exposed skin.
Small wavelets. Crests of glassy appearance, not breaking.
3
Gentle breeze
8-11 12-19 Leaves on smaller twigs in constant motion.
Larger wavelets. Crests begin to break.
4
Moderate breeze
12-15 20-28 Dust and loose paper raised. Small branches begin to move.
Small waves. Fairly frequent whit horses.
5
Fresh breeze
16-21 29-38 Smaller trees sway.
Moderate (1.2m) longer waves. Some foam and spray.
6
Strong breeze
22-27 39-49 Whistling heard in overhead wire.
Large waves. The white foam crests are more extensive everywhere.
7
Near gale
28-33 50-61 Effort needed to walk against the wind.
Sea heaps up and foam begins to streak along the direction of the wind.
8
Gale
34-40 62-74 Twigs broken from trees; generally impedes progress.
Moderatly high waves with breaking crests forming spindrift.
9
Strong gale
41-47 75-88 Slight structure damage.
High waves (2.75m) with dense foam. Wave crests start to roll over. Considerable spray.
10
Storm
48-55 89-102 Trees uprooted. Considerable structural damage.
Very high waves. The sea surface is white and there is considerable tumbling. Visibility is reduced.
11
Violent storm
56-63 103-117 Widespread structural damage.
Exceptionally high waves. Everywhere the edges of the wave crests are blown into froth. Visibility affected.
12
Hurricane
>63 >117 Considerable and widespread damage to structures.
Air filled with foeam and spray. Sea completely white with driving spray. Visibility very greately reduced.