| Calm |
0 |
<1 |
Sea like a mirror. |
- |
- |
| Light |
1 |
1-3 |
Ripples with the appearance of scales are formed but without foam crests. |
0.1 |
0.1 |
| Light |
2 |
4-6 |
Small wavelets, still short but more pronounced; crests have a glassy appearance and do not break. |
0.2 |
0.3 |
| Moderate |
3 |
7-10 |
Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses. |
0.6 |
1 |
| Moderate |
4 |
11-16 |
Small waves, becoming longer; fairly frequent white horses. |
1 |
1.5 |
| Fresh |
5 |
17-21 |
Moderate waves, taking a more pronounced long form; many white horses are formed (chance of some spray). |
2 |
2.5 |
| Strong |
6 |
22-27 |
Large waves begin to form; the white foam crests are more extensive everywhere (probably some spray). |
3 |
4 |
| Strong |
7 |
28-33 |
Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind. |
4 |
5.5 |
| Gale |
8 |
34-40 |
Moderately high waves of greater length; edges of crests begin to break into spindrift; the foam is blown in well-marked streaks along the direction of the wind. |
5.5 |
7.5 |
| Gale |
9 |
41-47 |
High waves; dense streaks of foam along the direction of the wind; crests of waves begin to topple, tumble and roll over; spray may affect visibility. |
7 |
10 |
| Storm |
10 |
48-55 |
Very high waves with long overhanging crests; the resulting foam, in great patches, is blown in dense white streaks along the direction of the wind; on the whole, the surface of the sea takes on a white appearance; the tumbling of the sea becomes heavy and shocklike; visibility affected. |
9 |
12.5 |
| Storm |
11 |
56-63 |
Exceptionally high waves (small and medium-sized ships might be for a time lost to view behind the waves); the sea is completely covered with long white patches of foam lying along the direction of the wind; everywhere the edges of the wave crests are blown into froth; visibility affected. |
11.5 |
16 |
| Hurricane |
12 |
64 and over |
The air is filled with foam and spray; sea completely white with driving spray; visibility very seriously affected. |
14 or over |
- |