Beaufort
Force

Wind speed
Knots

MPH

Description

Sea Condition

0

0

0

Calm

Sea  like a mirror

1

1 - 3

> 2.6

Light  Air

 Ripples but without foam crests

2

4 - 6

> 5.1

Light  Breeze

 Small wavelets. Crests do not break

3

7 - 10

> 8.6

Gentle  Breeze

 Large wavelets. Perhaps scattered white horses

4

11 - 16

> 13.8

Moderate Breeze

 Small waves. Fairly frequent white horses.

5

17 - 21

> 18.1

Fresh  Breeze

 Moderate waves, many white horses

6

22 - 27

> 23.3

Strong Breeze

Large  waves begin to form; white foam crests, probably spray

7

28 - 33

> 28.4

Near  Gale

Sea  heaps up and white foam blown in streaks along the direction of  the wind

8

34 - 40

> 34.5

Gale

 Moderately high waves, crests begin to break into spindrift

9

41 - 47

> 40.5

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

> 47.4

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

> 54.3

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+

55.1 +

Hurricane

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