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Beaufort Wind Scale

Descriptive term Beaufort scale number Mean velocity
Land criterion Sea criterion
Calm 0 < 2 Calm; smoke rises vertically. Sea like a mirror.
Light 1 2 - 6 Direction of wind shown by smoke drift, but not by wind vanes. Ripples with the appearance of scales are formed but without foam crests.
Light 2 7 - 12 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.
Moderate 3 13 - 19 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.
Moderate 4 20 - 30 Raises dust and loose paper; small branches are moved. Small waves, becoming longer; fairly frequent white horses.
Fresh 5 31 - 40 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).
Strong 6 41 - 51 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).
Strong 7 52 - 62 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.
Gale 8 63 - 75 Breaks twigs off trees; generally impedes progress. Moderately high waves of greater length; edges of crests begin to break into spindrift; the foam is blown in well-marked streaks along the direction of the wind.
Gale 9 76 - 87 Slight structural damage occurs. 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.
Storm 10 88 - 103 Seldom experienced inland; trees uprooted; considerable structural damage occurs. Very high waves with long overhanging 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 on a white appearance; the tumbling of the sea becomes heavy and shocklike; visibility affected.
Storm 11 104 - 117 Very rarely experienced; accompanied by wide-spread 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.
Hurricane 12 >= 118 Very rarely experienced; accompanied by wide-spread damage. The air is filled with foam and spray; sea completely white with driving spray; visibility very seriously affected.

Last revision date: <31 Jan 2013>