alan & rossi | An expanded Beaufort Scale of wind

Beaufort Number

Desc.

Velocity equivalent at a standard height of 10 metres above open flat ground

Specifications for estimating speed over land

Description of Sea

Sea State

Significant Sea Wave Height in Metres

knots

mps

kmph

mph

0

Calm

< 1

0 - 0.2

< 1

Calm; smoke rises vertically.

Sea like a mirror.

Calm
(glassy)

0

1

Light air

1 - 3

0.3 - 1.5

1 - 5

1 - 3

Direction of wind shown by smoke- drift but not by wind vanes.

Ripples withthe appearance of scales are formed, but without foam crests.

Calm
(rippled)

< 0.1

2

Light breeze

4 - 6

1.6 - 3.3

6 - 11

4 - 7

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

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

Smooth

0.1 - 0.4

3

Gentle breeze

7 - 10

3.4 - 5.4

12 - 19

8 - 12

Leaves and small twigs in constant motion; wind extends light flag.

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

Slight

0.4 - 1.0

4

Moderate breeze

11 - 16

5.5 - 7.9

20 - 28

13 - 18

Raises dust and loose paper; small branches are moved.

Small waves, becoming longer; fairly frequent white horses.

Slight/
Moderate

1.0 - 1.6

5

Fresh breeze

17 - 21

8.0 - 10.7

29 - 38

19 - 24

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

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

Moderate

1.6 - 2.5

6

Strong breeze

22 - 27

10.8 - 13.8

39 - 49

25 - 31

Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty.

Large waves begin to form; the white foam crests are more extensive everywhere (probably some spray).

Rough

2.5 - 4.0

7

Near gale

28 - 33

13.9 - 17.1

50 - 61

32 - 38

Whole trees in motion; inconvenience felt when walking against the wind.

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

Very Rough

4.0 - 6.0

8

Gale

34 - 40

17.2 - 20.7

62 - 74

39 - 46

Breaks twigs off trees; generally impedes progress.

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

Very Rough
to High

6.0 - 7.5

9

Strong gale

41 - 47

20.8 - 24.4

75 - 88

47 - 54

Slight structural damage occurs (chimney-pots and slates removed).

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.

High

7.5 - 9.0

10

Storm

48 - 55

24.5 - 28.4

89 - 102

55 - 63

Seldom experienced inland; trees uprooted; considerable structural damage occurs.

Very high waves with long over- hanging crests; the resulting foam, in great patches, is blown in dense white streaks along the direction of the wind; on the whole, the surface of the sea takes a white appearance; the tumbling of the sea becomes heavy and shock- like; visibility affected.

Very High

9.0 - 11.5

11

Violent storm

56 - 63

28.5 - 32.6

103 - 117

64 - 72

Very rarely experienced; accompanied by widespread damage.

Exceptionally high waves (small and medium-sized ships might be for a time lost to view behind the waves); the sea is completely covered with long white patches of foam lying along the direction of the wind; everywhere the edges of the wave crests are blown into froth; visibility affected.

Very High

11.5 - 14.0

12

Hurricane

64 - 71

32.7 - 36.9

118 - 133

73 - 82

*

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

Phenomenal

> 14.0

13

-

72 - 80

37.0 - 41.4

134 - 149

83 - 92

*

-

14

-

81 - 89

41.5 - 46.1

150 - 166

93 - 103

*

-

15

-

90 - 99

46.2 - 50.9

167 - 183

104 - 114

*

-

16

-

100 - 108

51.0 - 56.0

184 - 201

115 - 125

*

-

17

-

109 - 118

56.1 - 61.2

202 - 220

126 - 136

*

-