|
Force
|
Mean Speed (Knots)
|
Description
|
State of sea
|
Ashore
|
Probable wave height (m)
|
Probable max wave height
|
|
|
0-1
|
Calm
|
Flat
|
Smoke rises vertically
|
0
|
0
|
|
|
1-3
|
Light air
|
Ripples
|
Smoke shows wind direction
|
0.1
|
0
|
|
|
4-6
|
Light breeze
|
Small wavelets, non breaking
|
Leaves Rustle
|
0.2
|
0.3
|
|
|
7-10
|
Gentle breeze
|
Large wavelets, crests breaking
|
Wind extends small flag, leaves in motion
|
0.6
|
1
|
|
|
11-16
|
Moderate Breeze
|
Fairly frequent white horses
|
Small branches begin to move
|
1
|
1.5
|
|
|
17-21
|
Fresh Breeze
|
Moderate waves, many white horses some spray
|
Small trees begin to sway
|
2
|
2.5
|
|
|
22-27
|
Strong breeze
|
Large waves, white foam crests, some spray
|
Large branches move
|
3
|
4
|
|
|
28-33
|
Near gale
|
White foam blows from crests
|
Branches move, difficult to walk against the wind
|
4
|
5.5
|
|
|
34-40
|
Gale
|
Mod high waves, foam in streaks along surface
|
Twigs break off trees
|
5.5
|
7.5
|
|
|
41-47
|
Strong gale
|
High waves, tumblong crests, dense streaks of foam, much spray
|
Slates, chimneys begin to be moved
|
7
|
10
|
|
|
48-55
|
Storm
|
Very high waves with long overhanging crests, heavy tumbling sea
|
Trees uprooted, structural damage to buildings
|
9
|
12.5
|
|
|
56-63
|
Violent storm
|
Sea completely covered with long white foam patches
|
Wide spread damage to buildings etc
|
11.5
|
16
|
|
|
64 and above
|
Hurricane
|
Air filled with foam and driving spray. Visiblilty very seriously affected
|
As above
|
14
|
Above 16
|
