Beaufort
Number
|
MPH
|
Knots
|
International
Description
|
Specifications
|
|
0
|
Less than 1
|
Less than 1
|
Calm
|
Calm, smoke rises vertically
|
|
1
|
1 - 3
|
1 - 3
|
Light air
|
Direction of wind shown by smoke drift but not by wind
vanes.
|
|
2
|
4 - 7
|
4 - 6
|
Light Breeze
|
Wind felt on face; leaves rustle; vanes moved by wind
|
|
3
|
8 - 12
|
7 - 10
|
Gentle Breeze
|
Leaves and small twigs in constant motion; wind extends
light flag
|
|
4
|
13 - 18
|
11 - 16
|
Moderate
|
Raises dust, loose paper; small branches moved
|
|
5
|
19 - 24
|
17 - 21
|
Fresh
|
Small trees in leaf begin to sway; crested wavelets form
on inland
waters
|
|
6
|
25 - 31
|
22 - 27
|
Strong
|
Large branches in motion; whistling heard in telegraph
wires; umbrellas
used with difficulty
|
|
7
|
32 - 38
|
28 - 33
|
Near Gale
|
Whole trees in motion; inconvenience felt walking against
wind
|
|
8
|
39 - 46
|
34 - 40
|
Gale
|
Breaks twigs off trees; impedes progress
|
|
9
|
47 - 54
|
41 - 47
|
Strong Gale
|
Slight structural damage occurs
|
|
10
|
55 - 63
|
48 - 55
|
Storm
|
Trees uprooted; considerable damage occurs
|
|
11
|
64 - 72
|
56 - 63
|
Violent Storm
|
Wide Spread Damage
|
|
12
|
73 - 82
|
64 - 71
|
Hurricane
|
Wide Spread Damage
|