| Beaufort scale number
|
Descriptive term
|
Units in km/h
|
Units in knots
|
Description on Land
|
Description at Sea
|
| 0
|
Calm
|
0
|
0
|
Smoke rises vertically
|
Sea like a mirror.
|
| 1-3
|
Light winds
|
19 km/h or less
|
10 knots or less
|
Wind felt on face; leaves rustle; ordinary vanes moved by wind.
|
Small wavelets, ripples formed but do not break: A glassy appearancemaintained.
|
| 4
|
Moderate winds
|
20 - 29 km/h
|
11-16 knots
|
Raises dust and loose paper; small branches are moved.
|
Small waves - becoming longer; fairly frequent white horses.
|
| 5
|
Fresh winds
|
30 - 39 km/h
|
17-21 knots
|
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 ofsome spray
|
| 6
|
Strong winds
|
40 - 50 km/h
|
22-27 knots
|
Large branches in motion; whistling heard in telephone wires; umbrellas used withdifficulty.
|
Large waves begin to form; the white foam crests are more extensive with probably somespray
|
| 7
|
Near gale
|
51 - 62 km/h
|
28-33 knots
|
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 ofwind.
|
| 8
|
Gale
|
63 - 75 km/h
|
34-40 knots
|
Twigs break off trees; progress generally impeded.
|
Moderately high waves of greater length; edges of crests begin to break into spindrift; foam isblown in well-marked streaks along
the direction of the wind.
|
| 9
|
Strong gale
|
76 - 87 km/h
|
41-47 knots
|
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; spraymay affect visibility.
|
| 10
|
Storm
|
88 - 102 km/h
|
48-55 knots
|
Seldom experienced inland; trees uprooted; considerable structural damage.
|
Very high waves with long overhanging crests; the resulting foam in great patches is blown indense white streaks; the surface of
the sea takes on a white appearance; the tumbling of the seabecomes heavy with visibility affected.
|
| 11
|
Violent storm
|
103 -117 km/h
|
56-63 knots
|
Very rarely experienced - 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 blowninto froth.
|
| 12+
|
Hurricane
|
118 km/h or more
|
64 knots or more
|
The air is filled with foam and spray. Sea completely white with driving spray; visibility veryseriously affected
|
