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Beaufort,
Francis
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Beaufort
Wind Scale |
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wind
scale
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Wind effects observed on sea |
Beaufort
# |
WMO description
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WMO
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wind speed
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wind speed |
Wind effects observed on land
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Sea surface smooth and mirror-like.
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0 |
< 1 knot
< 1 mph
< 1 km/h
< 0.5 m/s
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Calm |
Calm; smoke rises vertically. |
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Ripples with the appearance of scales are
formed, but without foam crests.
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1 |
1--3 knots
1--3 mph
1--5 km/h
0.5--1.5 m/s
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Light air |
Direction of wind shown by smoke drift, but not
by wind vanes. |
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Small wavelets, still short, but more pronoun-
ced; crests have a glassy appearance and do not break.
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2 |
4--6 knots
4--7 mph
6--11 km/h
1.6--3.0 m/s
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Light breeze |
Wind felt on face, leaves rustle, vanes begin to
move. |
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Large wavelets; crests begin to break; foam of
glassy appearance; perhaps some scattered whitecaps (white foam crests).
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3 |
7--10 knots
8--12 mph
12--19 km/h
3.1--5.1 m/s
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Gentle breeze |
Leaves and small twigs in constant motion; wind
extends light flag. |
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Small waves (1-4 ft), becoming longer; fairly
frequent whitecaps.
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4 |
11--16 knots
13--18 mph
20--28 km/h
5.2--8.2 m/s
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Moderate breeze |
Dust, leaves, and loose paper lifted, small tree
branches move. |
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Moderate waves (4-8 ft), taking a more pronoun-
ced long form; many whitecaps; some spray.
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5 |
17--21 knots
19--24 mph
29--38 km/h
8.3--10.8 m/s
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Fresh breeze |
Small trees in leaf begin to sway; crested
wavelets form on inland waters. |
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Larger waves (8-13 ft) begin to form; whitecaps
common; more spray.
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6 |
22--27 knots
25--31 mph
39--49 km/h
10.9--13.9 m/s
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Strong breeze |
Large tree branches in motion; whistling heard
in telegraph wires; umbrellas used with difficulty. |
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Sea heaps up; waves of ~13 ft; white foam from
breaking waves begins to be blown in streaks along the direction of the
wind
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7 |
28--33 knots
32--38 mph
50--61 km/h
14.0--17.0 m/s
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Near gale |
Whole trees in motion; resistance felt when
walking against the wind. |
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Moderately high (13-20 ft) waves of greater
length; edges of crests begin to break into spindrift; foam is blown in
well-marked streaks along the direction of the wind.
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8 |
34--40 knots
39--46 mph
62--74 km/h
17.1--20.5 m/s
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Gale |
Breaks twigs off trees; generally impedes motion
against wind. |
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High waves (20 ft); crests of waves begin to
topple, tumble and roll over; dense streaks of foam along the direction of
the wind; spray may reduce visibility.
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9 |
41--47 knots
47--54 mph
75--88 km/h
20.6--24.2 m/s
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Strong gale
(Severe gale) |
Slight structural damage occurs, chimney-pots
and slate blows off roofs. |
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Very high (20-30 ft) waves with overhanging
crests; sea surface takes white appearance as foam is blown in very dense
streaks along the direction of the wind; tumbling (rolling) of the sea
becomes heavy and shock like; lowered visibility.
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10 |
48--55 knots
55--63 mph
89--102 km/h
24.3--28.3 m/s
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Storm |
Seldom experienced on land, trees broken or
uprooted, considerable structural damage occurs. |
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Exceptionally high (30-45 ft) waves; small and
medium-size ships might be for a time lost to view behind the waves; sea
completely covered with long white patches of foam lying along the
direction of the wind; edges of the wave crests blown into froth;
visibility further reduced.
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11 |
56--63 knots
64--72 mph
103--117 km/h
28.4--32.4 m/s
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Violent storm |
Very rarely experienced on land; accompanied by
wide-spread damage. |
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Air filled with foam and spray; waves over 45
ft; sea completely white with driving spray; visibility greatly reduced
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12 |
>= 64 knots
>= 73 mph
>= 118 km/h
>= 32.5 m/s
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UPDATED : 2004-11-07
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WEBSITE EDITOR : Krešimir J. Adamić
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