| |
|
Wind |
Length of waves [m]* |
Height of waves [m]* |
| °B |
Description |
For use on land |
For use at sea |
km/h |
Mm/h |
| 0 |
Calm |
Smoke rises vertically. |
Sea like a mirror. |
0-1 |
0-1 |
- |
- |
| 1 |
Light air |
Direction of wind shown by smoke drift but not by wind vanes. |
Ripples with the appearance of scales are formed, but without foam crests. |
2-6 |
1-3 |
do 5 |
0.1-0.2 |
| 2 |
Light breeze |
Wind felt on face, leaves rustle, ordinary wind vanes moved by wind. |
Small wavelets, still short but more pronounced. Crests have a glassy appearance and do not break. |
7-12 |
4-6 |
do 15 |
0.2-0.3 |
| 3 |
Gentle breeze |
Leaves and small twigs in constant motion, wind extends light flags. |
Large wavelets. Crests begin to break. Foam of glassy appearance. Perhaps scattered white horses. |
13-18 |
7-10 |
do 25 |
0.6-1.0 |
| 4 |
Moderate breeze |
Wind raises dust and loose paper, small branches move. |
Small waves, becoming longer, fairly frequent white horses. |
19-26 |
11-16 |
do 50 |
1.0-1.5 |
| 5 |
Fresh breeze |
Small trees in leaf start to sway, crested wavelets on inland waters. |
Moderate waves, taking a more pronounced form, many white horses are formed. Chance of some spray. |
27-35 |
17-21 |
do 75 |
2.0-2.5 |
| 6 |
Strong breeze |
Large branches in motion, whistling in telegraph wires, umbrellas used with difficulty. |
Large waves begin to form, the white foam crests are more extensive everywhere. Probably some spray. |
36-44 |
22-27 |
do 100 |
3.0-4.0 |
| 7 |
Near gale |
Whole trees in motion, inconvenient to walk against the wind. |
Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind. |
45-54 |
28-33 |
do 135 |
4.0-5.5 |
| 8 |
Gale |
Twigs break from trees, difficult to walk. |
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. |
55-65 |
34-40 |
150-200 |
5.5-7.5 |
| 9 |
Strong gale |
Slight structural damage occurs, chimney pots and slates removed. |
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. |
66-77 |
41-47 |
150-200 |
7.0-10.0 |
| 10 |
Storm |
Trees uprooted, considerable structural damage occurs. |
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. |
78-90 |
48-55 |
do 250 |
9.0-12.5 |
| 11 |
Violent storm |
Widespread damage. |
Exceptionally high waves (small and medium sized ships might be lost for a time 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 waves are blown into froth. Visibility affected. |
91-104 |
56-63 |
do 300 |
11.5-14.0 |
| 12 |
Hurricane |
Widespread damage. |
The air is filled with foam and spray. The sea completely white with driving spray, visibility very seriously affected. |
over 104 |
over 63 |
and longer |
15.0 and higher |
