|
Beaufort scale number
|
Descriptive term
|
Units in km/h
|
Units in knots
|
Description on Land
|
Description at Sea
|
|
0
|
Calm
|
<1
|
<1
|
Smoke rises vertically
|
Sea like a mirror.
|
|
1
|
Light air
|
1-5
|
1-3
|
Direction of wind shown by smoke drift but not by wind vanes.
|
Ripples with the appearance of scales are formed, but without foam crests.
|
|
2
|
Light Breeze
|
6-11
|
4-6
|
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.
|
|
3
|
Gentle Breeze
|
12-19
|
7-10
|
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.
|
|
4
|
Moderate breeze
|
20-28
|
11-16
|
Raises dust and loose paper; small branches are moved.
|
Small waves, becoming longer; fairly frequent white horses.
|
|
5
|
Fresh breeze
|
29-38
|
17-21
|
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 - a chance of
some spray
|
|
6
|
Strong breeze
|
39-49
|
22-27
|
Large branches in motion; whistling heard in telephone wires; umbrellas used with
difficulty.
|
Large waves begin to form; the white foam crests are more extensive with probably some
spray
|
|
7
|
Near gale
|
50-61
|
28-33
|
Whole trees in motion; inconvenience felt when walking against wind.
|
Sea heaps up and white foam from breaking waves begins to be blown in streaks along direction of
wind.
|
|
8
|
Gale
|
62-74
|
34-40
|
Twigs break off trees; progress generally impeded.
|
Moderately high 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.
|
|
9
|
Strong gale
|
75-88
|
41-47
|
Slight structural damage occurs -roofing dislodged; larger branches break off.
|
High waves; dense streaks of foam; crests of waves begin to topple, tumble and roll over; spray
may affect visibility.
|
|
10
|
Storm
|
89-102
|
48-55
|
Seldom experienced inland; trees uprooted; considerable structural damage.
|
Very high waves with long overhanging crests; the resulting foam in great patches is blown in
dense white streaks; the surface of the sea takes on a white appearance; the tumbling of the sea
becomes heavy with visibility affected.
|
|
11
|
Violent storm
|
103-117
|
56-63
|
Very rarely experienced; accompanied by widespread damage.
|
Exceptionally high waves; small and medium sized ships occasionally lost from view behind waves;
the sea is completely covered with long white patches of foam; the edges of wave crests are blown
into froth.
|
|
12
|
Hurricane
|
>118
|
>64
|
Severe and extensive damage. |
The air is filled with foam and spray. Sea completely white with driving spray; visibility very
seriously affected
|