|
Force
|
(knots)
|
Wind speed
(km/h)
|
(m/sec)
|
Description
|
Deep sea criteria
|
Probable mean
(max) wave ht(m)
|
|
0
|
<1
|
0-2
|
0-0.5
|
Calm
|
Like a mirror
|
-
|
|
1
|
1-3
|
2-6
|
0.3-1.5
|
Light air
|
Ripples like scales are formed
|
0.1 (0.1)
|
|
2
|
4-6
|
7-11
|
1.6-3.3
|
Light breeze
|
Small wavelets, still short but more pronounced, not breaking
|
0.1 (0.3)
|
|
3
|
7-10
|
13-19
|
3.4-5.4
|
Gentle breeze
|
Large wavelets, crests begin to break; a few white horses
|
0-6 (1)
|
|
4
|
11-16
|
20-30
|
5.5-7.9
|
Moderate breeze
|
Small waves growing longer: fairly frequent white horses
|
1 (1.5)
|
|
5
|
17-21
|
31-39
|
8.0-10.7
|
Fresh breeze
|
Moderate waves, taking more pronounced form; many white horses, perhaps some spray
|
2 (2.5)
|
|
6
|
22-27
|
41-50
|
10.8-13.8
|
Strong breeze
|
Large waves forming; white foam crests more extensive;
probably some spray
|
3 (4)
|
|
7
|
28-33
|
52-61
|
13.9-17.1
|
Near gale
|
Sea heaps up: white foam from breaking waves begins
to blow in streaks
|
4 (5.5)
|
|
8
|
34-40
|
63-74
|
17.2-20.7
|
Gale
|
Moderately high waves of greater length; edge of crests
break into spindrift; foam blown in well marked streaks
driving spray; visibility very seriously affected
|
5.5 (7.5)
|
|
9
|
41-47
|
76-87
|
20.8-24.4
|
Strong gale
|
High waves with tumbling crests; dense streaks of foam;
spray may affect visibility
|
7 (10)
|
|
10
|
48-55
|
89-102
|
24.5-28.4
|
Storm
|
Very high waves with long overhanging crests; dense
streams of foam make surface of sea white. Heavy tumbling
sea; visibility affected
|
9 (12.5)
|
|
11
|
56-63
|
104-117
|
28.5-32.6
|
Violent storm
|
Exceptionally high waves; sea completely covered with long white patches of foam; edges of wave crests blown into froth.
Visibility affected
|
11.5 (16)
|
|
12
|
64 plus
|
118 plus
|
32.7 plus
|
Hurricane
|
Air filled with foam and spray; sea completely white with driving spray; visibility very seriously affected.
|
14 (–)
|