BEAUFORT scale
Wind speed at a height of 10 m from flat ground
Force
Type of
wind
Speed
(knots)
Speed
(kph)
Speed
(m/s)
Effects on Land Sea condition
0 Calm 0 - 1
0 - 1 < 0.3
smoke rises vertically sea like a mirror
1 Light air 1 - 3
1 - 5 0.3 - 1.5
the wind bends the smoke
ripples but without foam
crests
2
Light
breeze
4 - 6
6 - 11 1.6 - 3.3
The wind can be felt on the
face; shakes the leaves
small but evident wavelets
3
Gentle
breeze
7 - 10
12 - 19 3.4 - 5.4
The wind continuously shakes
the leaves and twigs
large wavelets. Perhaps
scattered white horses
4
Moderate
breeze
11 - 16
20 - 28 5.5 - 7.9
The wind raises dust and
scraps of paper; shakes the
twigs
small waves. Fairly frequent
white horses
5
Fresh
breeze
17 - 21
29 - 38 8 - 10.7
leafy shrubs sway
small waves form on inland
waters. Moderate waves,
many white horses
6
Strong
breeze
22 - 27
39 - 49 10.8 - 13.8
Shakes thick branches, metal
wires hum; it becomes difficult
to keep an umbrella open
large waves begin to form;
white foam crests, probably
spray
7 Near gale 28 - 33
50 - 61 13.9 - 17.1
Whole trees sway; it is difficult
to walk against the wind
sea heaps up and white
foam blown in streaks along
the direction of the wind
8 Gale 34 - 40
62 - 74 17.2 - 20.7
Breaks the branches of trees; it
is almost impossible to walk
against the wind
moderately high waves,
crests begin to break into
spindrift.
9
Strong
gale
41 - 47
75 - 88 20.8 - 24.4
Causes slight damage to
buildings (stacks, tiles, etc..).
high waves. Dense foam
along the direction of the
wind. Crests of waves begin
to roll over. Spray may affect
visibility
10 Storm 48 - 55
89 - 102 24.5 - 28.4
Rare inland; uproots trees;
causes considerable damage
to buildings
very high waves with long
overhanging crests. Visibility
affected
11
Violent
storm
56 - 63
103 - 117 28.5 - 32.6
Very rare, causes extensive
devastation
exceptionally high waves
that may hide medium sized
ships. Visibility affected
12 Hurricane 64 +
over 118 32.7 +
Causes very serious
catastrophes
the air is filled with foam and
spray. Sea completely white
with driving spray. Visibility
very seriously affected
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