Force |
Km/h |
Mph |
Knots |
Wind |
Probable sea state |
0 |
less than 1 |
less than 1 |
less than 1 |
Still |
Like a mirror |
1 |
1-5 |
1-3 |
1-3 |
Very light |
Ripples with appearance of scales. No crests. |
2 |
6-11 |
4-7 |
4-6 |
Light breeze |
Small wavelets. Glassy crests that don't break. |
3 |
12-19 |
8-12 |
7-10 |
Gentle breeze |
Crests begin to break |
4 |
20-29 |
13-18 |
11-16 |
Moderate breeze |
Waves becoming larger, frequent white horses |
5 |
30-39 |
19-24 |
17-21 |
Fresh breeze |
Moderate waves, many white horses, some spray |
6 |
40-50 |
25-31 |
22-27 |
Strong breeze |
Large waves, extensive white horses |
7 |
51-61 |
32-38 |
28-33 |
Near gale |
Sea heaps up, waves breaking, white foam blown in streaks |
8 |
62-74 |
39-46 |
34-40 |
Gale |
Moderate high waves, crests break into spindrift, white foam |
9 |
75-87 |
47-54 |
41-47 |
Strong gale |
High waves, crests topple spray affects visibility |
10 |
88-101 |
55-63 |
48-55 |
Storm |
Very high breaking waves, dense foam streaks |