| Force |
Speed (knots) |
Speed (mph) |
Conditions |
| 0 |
< 1 |
< 1 |
Calm, sea like a mirror. |
| 1 |
1 - 3 |
1 - 3 |
Light air, ripples only. |
| 2 |
4 - 6 |
4 - 7 |
Light breeze, small wavelets (0.2m), crests have a glassy appearance. |
| 3 |
7 - 10 |
8 - 12 |
Gentle breeze, large wavelets (0.6m), crests begin to break. |
| 4 |
11 - 16 |
13 - 18 |
Moderate breeze, small waves (1m), some white horses. |
| 5 |
17 - 21 |
19 - 24 |
Fresh breeze, moderate waves (1.8m), many white horses. |
| 6 |
22 - 27 |
25 - 31 |
Strong breeze, large waves (3m), probably some spray. |
| 7 |
28 - 33 |
32 - 38 |
Near gale, mounting sea (4m) with foam blown in streaks downwind. |
| 8 |
34 - 40 |
39 - 46 |
Gale, moderately high waves (5.5m), crests break into spindrift. |
| 9 |
41 - 47 |
47 -54 |
Strong gale, high waves (7m), dense foam, visibility affected. |
| 10 |
48 - 55 |
55 - 63 |
Storm, very high waves (9m), heavy sea roll, visibility impaired,
surface generally white. |
| 11 |
56 - 63 |
64 - 74 |
Violent storm, exceptionally high waves (11m), visibility poor. |
| 12 |
64 + |
75 + |
Hurricane, 14 m waves, air filled with foam and spray, visibility
bad. |
