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.