The Beaufort scale, which is used in Met Office
marine forecasts, is an empirical measure for describing wind intensity based
on observed sea conditions.
|
Specifications
and equivalent speeds |
|||||||||
|
Beaufort wind
scale |
Mean Wind Speed |
Limits of wind
speed |
Wind descriptive
terms |
Probable wave
height |
Probable maximum
wave height |
Seastate |
Sea descriptive
terms |
||
|
Knots |
ms-1 |
Knots |
ms-1 |
in metres1 |
in metres2 |
||||
|
0 |
0 |
0 |
<1 |
<1 |
Calm |
- |
- |
0 |
Calm (glassy) |
|
1 |
2 |
1 |
1-3 |
1-2 |
Light air |
0.1 |
0.1 |
1 |
Calm (rippled) |
|
2 |
5 |
3 |
4-6 |
2-3 |
Light breeze |
0.2 |
0.3 |
2 |
Smooth (wavelets) |
|
3 |
9 |
5 |
7-10 |
4-5 |
Gentle breeze |
0.6 |
1.0 |
3 |
Slight |
|
4 |
13 |
7 |
11-16 |
6-8 |
Moderate breeze |
1.0 |
1.5 |
3-4 |
Slight - Moderate |
|
5 |
19 |
10 |
17-21 |
9-11 |
Fresh breeze |
2.0 |
2.5 |
4 |
Moderate |
|
6 |
24 |
12 |
22-27 |
11-14 |
Strong breeze |
3.0 |
4.0 |
5 |
Rough |
|
7 |
30 |
15 |
28-33 |
14-17 |
Near gale |
4.0 |
5.5 |
5-6 |
Rough-Very rough |
|
8 |
37 |
19 |
34-40 |
17-21 |
Gale |
5.5 |
7.5 |
6-7 |
Very rough - High |
|
9 |
44 |
23 |
41-47 |
21-24 |
Strong gale3 |
7.0 |
10.0 |
7 |
High |
|
10 |
52 |
27 |
48-55 |
25-28 |
Storm |
9.0 |
12.5 |
8 |
Very High |
|
11 |
60 |
31 |
56-63 |
29-32 |
Violent storm |
11.5 |
16.0 |
8 |
Very High |
|
12 |
- |
|
64+ |
33+ |
Hurricane |
14+ |
- |
9 |
Phenomenal |
Notes
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.
3.
The official term
is Strong gale, however, the Met Office uses the descriptive term Severe gale