Beaufort Scale

Force

Description Sea State Description

Speed
Knots

Range

Forecast
Description

Sea State

Waves
metres

0

Calm Sea like a mirror

0

<1

Calm

Calm

0

1

Light air "Ripples with the appearance of scales are formed but without foam crests."

2

1-3

Light

Smooth

0.1

2

Light breeze "Small wavelets still short but more pronounced. Crests have a glassy appearance and do not break."

5

4-6

Light

Smooth

0.2

3

Gentle breeze Large wavelets. Crests begin to break. Foam of glassy appearance. Scattered white horses.

9

7-10

Light

Slight

0.6

4

Moderate breeze "Small waves becoming longer fairly frequent white horses."

13

11-16

Moderate

Moderate

1

5

Fresh breeze "Moderate waves taking a more Pronounced long form; many white horses are formed. Chance of some spray."

19

17-21

Fresh

Rough

2

6

Strong breeze Large waves begin to form; white foam crests are more extensive everywhere. Probably some spray.

24

22-27

Strong

Very rough

3

7

Near gale Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind.

30

28-33

Strong

High

4

8

Gale Moderately high waves of greater length; edges of crests begin to break into spindrift. The foam is blown in well-marked streaks along the direction of the wind.

37

34-40

Gale

Very high

5.5

9

Strong gale "High waves. Dense streaks of foam along the direction of the wind. Crests of waves begin to topple tumble and roll over. Spray may affect visibility."

44

41-47

Severe gale

Very high

7

10

Storm "Very high waves with long over-hanging crests. The resulting foam in great patches is blown in dense white streaks along the direction of wind. On the whole the surface of the sea takes a white appearance. The 'tumbling' of the sea becomes heavy and shock-like. Visibility is affected"

52

48-55

Storm

Phenomenal

9

11

Violent storm Exceptionally high waves (small & medium sized ships might be lost to view for a time behind the waves). The sea is completely covered with long white patches of foam lying along the direction of the wind. Every-where the edges of the wave crests are blown into froth. Visibility is affected.

60

56-63

Violent storm

Phenomenal

11.5

12

Hurricane The air is filled with foam and spray. Sea completely white with driving spray; visibility very seriously affected

64+

Hurricane

14