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.