Beaufort Scale

 

 

Wind

Speed

 

 

Probable  

Wave Height

Force

Knots

MPH

Description

Sea State

Metres

Feet

0

0

0

Calm

Sea like a mirror.

0

0

1

1-3

1-3

Light Air

Ripples with the appearance of scales are formed but without foam.

0

0

2

4-6

4-7

Light Breeze

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

.1

.3

3

7-10

8-11

Gentle Breeze

Large wavelets, crests begin to break; foam of glassy appearance, perhaps scattered white horses.

.4

1.5

4

11-16

12-18

Moderate Breeze

Small waves becoming longer; fairly frequent white horses.

1

3

5

17-21

19-24

Fresh Breeze

Moderate waves taking a more pronounced long form; many white horses, chance of some spray.

2

6

6

22-27

25-31

Strong Breeze

Large waves begin to foam and white foam crests become more extensive, probably some spray.

3

10

7

28-33

32-38

Near Gale

Sea heaps up and white foam from the breaking waves begins to be blown in streaks.

4

14

8

34-40

39-46

Gale

Moderately high waves of greater length, edges of crests begin to break into spindrift.   The foam blown in well-marked streaks.

5.5

18

9

41-47

47-54

Strong

High waves; dense streaks of foam.  Crests begin to topple and roll over, spray may effect visibility.

7

25

10

48-55

55-63

Storm

Very high waves with long, overhanging crests.  Foam in great patches is blown in dense white streaks making surface of the sea white.  The tumbling of the sea becomes very heavy and shock-like.  Visibility is poor.

9

30

11

56-63

64-72

Violent Storm

Exceptionally high waves; the sea is completely covered with patches of foam.  Visibility is reduced.

11

36

12

64+

73+

Hurricane

The air is filled with foam and spume; sea completely white with driving spray, visibility very seriously affected.

14

47