| Knots |
Bft. |
m/s
|
km/h
|
Label
|
Effect
on sea
|
| 1 |
0 |
0 - 0.2 |
1 |
Calm |
Sea like a mirror |
| 1-3 |
1 |
0.3-1.5 |
1-5 |
Light Air |
Ripples with the
appearance of scales are formed, but without foam crests |
| 4-6 |
2 |
1.6-3.3 |
6-11 |
Light Breeze |
Small wavelets, still
short, but more pronounced. Crests have a glassy
appearance and do not break |
| 7-10 |
3 |
3.4-5.4 |
12-19 |
Gentle Breeze |
Large wavelets. Crests
begin to break. Foam of glassy appearance. Perhaps
scattered white horses |
| 11-15 |
4 |
5.5-7.9 |
20-28 |
Moderate Breeze |
Small waves, becoming
larger; fairly frequent white horses |
| 16-21 |
5 |
8.0-10.7 |
29-38 |
Fresh Breeze |
Moderate waves, taking
a more pronounced long form; many white horses are formed.
Chance of some spray |
| 22-27 |
6 |
10.8-13.8 |
39-49 |
strong Breeze |
Large waves begin to
form; the white foam crests are more extensive everywhere.
Probably some spray |
| 28-33 |
7 |
13.9-17.1 |
50-61 |
Near Gale |
Sea heaps up and white
foam from breaking waves begins to be blown in streaks
along the direction of the wind |
| 34-40 |
8 |
17.2-20.7 |
62-74 |
Gale |
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 |
| 41-47 |
9 |
20.8-24.4 |
75-88 |
Severe Gale |
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 |
| 48-55 |
10 |
24.5-28.4 |
89-102 |
Storm |
Very high waves with
long over-hanging 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 shock-like. Visibility affected |
| 56-63 |
11 |
28.5-32.6 |
103-117 |
Violent Storm |
Exceptionally high
waves (small and medium-size ships might disappear behind
the waves). The sea is completely covered with long white
patches of foam flying along the direction of the wind.
Everywhere the edges of the wave crests are blown into
froth. Visibility affected |
| 64-71 |
12 |
32.7-36.9 |
118-133 |
Hurricane |
The air is filled with
foam and spray. Sea completely white with driving spray;
visibility very seriously affected |
