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Beaufort wind force scale

Specifications and equivalent speeds
Beaufort wind scale
Mean Wind Speed
Limits of wind speed
Wind descriptive terms
Probable wave height in metres*
Probable maximum wave height in metres*
Seastate
Sea descriptive terms
Knots
m/s
Knots
m/s
0
0
0
<1
0-0.2
Calm
-
-
0
Calm (glassy)
1
2
0.8
1-3
0.3-1.5
Light air
0.1
0.1
1
Calm (rippled)
2
5
2.4
4-6
1.6-3.3
Light breeze
0.2
0.3
2
Smooth (wavelets)
3
9
4.3
7-10
3.4-5.4
Gentle breeze
0.6
1.0
3
Slight
4
13
6.7
11-16
5.5-7.9
Moderate breeze
1.0
1.5
3-4
Slight-Moderate
5
19
9.3
17-21
8.0-10.7
Fresh breeze
2.0
2.5
4
Moderate
6
24
12.3
22-27
10.8-13.8
Strong breeze
3.0
4.0
5
Rough
7
30
15.5
28-33
13.9-17.1
Near gale
4.0
5.5
5-6
Rough-Very rough
8
37
18.9
34-40
17.2-20.7
Gale
5.5
7.5
6-7
Very rough-High
9
44
22.6
41-47
20.8-24.4
Severe gale
7.0
10.0
7
High
10
52
26.4
48-55
24.5-28.4
Storm
9.0
12.5
8
Very High
11
60
30.5
56-63
28.5-32.6
Violent storm
11.5
16.0
8
Very High
12
-
-
64+
32.7+
Hurricane
14+
-
9
Phenomenal
*
  1. These values refer to well-developed wind waves of the open sea.
  2. The lag effect between the wind getting up and the sea increasing should be borne in mind.