BEAUFORT
FORCE |
| Force |
Description |
Sea
State |
Specification
on land |
knots*
|
km/h* |
mph* |
0 |
Calm |
Sea
like mirror |
Smoke
rises vertically |
<1 |
<1 |
<1 |
1 |
Very
Light |
Ripples
with appearance of scales, no form crests |
Direction
of wind shown by smoke drift but not by wind vanes |
1
- 3 |
1
- 5 |
1
- 3 |
2 |
Light
breeze |
Wavelets,
small but pronounced. Crests with glassy appearance, but do not
break. |
Wind
felt on face, leaves rustle, ordinary wind vane moved by wind. |
4
- 6 |
6
- 11 |
4
- 7 |
3 |
Gentle
breeze |
Large
wavelets, crests begin to break. Glassy looking foam, occasional
white horses. |
Leaves
and small twigs in constant motion, wind extends light flag. |
7
- 10 |
12
- 19 |
8
- 12 |
4 |
Moderate
breeze |
Small
waves becoming longer, frequent white horses. |
Wind
raises dust and loose paper, small branches move. |
11
- 16 |
20
- 29 |
13
- 18 |
5 |
Fresh
breeze |
Moderate
waves of pronounced long form. Many whit horses, some spray. |
Small
trees in leaf start to sway, crested wavelets form on inland
waters. |
17
- 21 |
30
- 39 |
19
- 24 |
6 |
Strong
breeze |
Some
large waves, extensive white foam crests, some spray. |
Large
branches in motion, whistling in telegraph wires, umbrellas used
with difficulty. |
22
- 27 |
40
- 50 |
25
- 31 |
7 |
Near
gale |
Sea
heaped up, white foam from breaking waves blowing in streaks
with the wind. |
Whole
trees in motion, inconvenience felt when walking against wind. |
28
- 33 |
51
- 61 |
32
- 38 |
8 |
Gale |
Moderately
high and long waves. Crests break into spindrift, blowing foam
in well marked streaks. |
Twigs
break from trees, difficult to walk. |
34
- 40 |
62
- 74 |
39
- 46 |
9 |
Strong
gale |
High
waves, dense foam streaks in wind, wave crests topple, tumble
and roll over. Spray reduces visibility |
Slight
structural damage occurs, chimney pots and slates removed |
41
- 47 |
75
- 87 |
47
- 54 |
10 |
Storm |
Very
high waves with long overhanging crests. Dense blowing foam,
sea surface appears white. Heavy tumbling of sea, shock-like,
poor visibility. |
Trees
uprooted, considerable structural damage occurs. |
48
- 55 |
88
- 101 |
55
- 63 |
11 |
Violent
storm |
Exceptionally
high waves, sometimes concealing small and medium sized ships.
Sea completely covered with long white patches of foam. Edges
of wave crests blown into froth. Poor visibility. |
Widespread damage. |
56
- 63 |
102
- 117 |
64
- 73 |
12 |
Hurricane |
Air
filled with foam and spray, sea white with driving spray, poor
visibility. |
Widespread damage. |
>64 |
>119 |
>74 |
*
Equivalent Speed (10m above ground)
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