Beaufort

General

Sea Criterion

Land Criterion

Windspeed
in knots

Windspeed
in mph

0

Calm

Sea like a mirror

Calm; smoke rises vertically

below 1

1

1

Light air

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

Wind direction shown by
smoke drift but not by wind
vanes.

1 to 3

1 to 3.5

2

Light breeze

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

Wind felt on face;leaves rustle; ordinary vane moved by wind.

4 to 6

4.5 to 7

3

Gentle breeze

Large wavelets. Crests begin to break. Foam of glassy appearance. Perhaps scattered white horses

Leaves and small twigs in constant motion. Wind extends light flags

7 to 10

8 to 11.5

4

Moderate breeze

Small waves becoming longer; fairly frequent white horses

Raises dust and loose paper small branches are moved

11 to 16

12.5 to 18.5

5

Fresh breeze

Moderate waves, taking more pronounced long form; many white horses are formed. Chance of some spray

Small trees in leaf begin to sway. Crested wavelets form on inland waters

17 to 21

19.5 to 24

6

Strong breeze

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

Large branches in motion; whistling heard in telephone wires, umbrellas used with difficulty

22 to 27

25 to 31

7

Near gale

Sea heaps up and white foam from breaking waves begin to be blown in streaks along the direction of the wind

Whole trees in motion;inconvenience felt when walking against wind

28 to 33

32 to 38

8

Gale

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

Breaks twigs off trees; generally impedes progress

34 to 40

39 to 46

9

Severe 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.

Slight structural damage occurs (chimney pots and slates removed)

41 to 47

47 to 54

10

Storm

Very high waves with long overhanging crest. Resulting foam in great patches is blown in dense streaks along the direction of the wind. Whole surface takes on a white appearance. Tumbling of sea becomes heavy and shock-like. Visibility affected.

Seldom experienced inland; trees uprooted; considerable structural damage occurs

48 to 55

55 to 63

11

Hurricane

Oh sh**

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