Beaufort Number or Force
|
Wind Speed and Description
|
Effects Land/Sea
|
Probable Wave Height
|
MPH
|
Knots
|
Description
|
0
|
<1
|
<1
|
Calm
|
Still, calm air, smoke will rise vertically. Smooth like a mirror.
|
0
|
1
|
1-3
|
1-3
|
Light Air
|
Rising smoke drifts, wind vane is inactive. Small ripples like fish scales.
|
¼ - ½ foot
|
2
|
4-7
|
4-6
|
Light Breeze
|
Leaves rustle, can feel wind on your face, wind vanes begin to move. Short, small pronounced wavelets with no crests.
|
¼ - ½ foot
|
3
|
8-12
|
7-10
|
Gentle Breeze
|
Leaves and small twigs move, light weight flags extend. Large wavelets, crests start to break, some whitecaps.
|
2 feet
|
4
|
13-18
|
11-16
|
Moderate Breeze
|
Small branches move, raises dust, leaves and paper. Small waves develop, becoming longer, whitecaps.
|
4 feet
|
5
|
19-24
|
17-21
|
Fresh Breeze
|
Small trees sway. Moderate lengthening waves, with many white caps and some spray.
|
6 feet
|
6
|
25-31
|
22-27
|
Strong Breeze
|
Large tree branches move, telephone wires begin to "whistle"Large waves, extensive white caps, some spray.
|
10 feet
|
7
|
32-38
|
28-33
|
Near Gale
|
Large trees sway, becoming difficult to walk. Heaps of waves, with some breakers whose foam is blown downwind in streaks.
|
14 feet
|
8
|
39-46
|
34-40
|
Gale
|
Twigs and small branches are broken from trees, walking is difficult. Moderately large waves with blown foam.
|
18 feet
|
9
|
47-54
|
41-47
|
Strong Gale
|
Slight damage occurs to buildings, shingles are blown off of roofs. Rolling seas, dense foam, Blowing spray reduces visibility.
|
23 feet
|
10
|
55-63
|
48-55
|
Whole Gale or Storm
|
Trees are broken or uprooted, building damage is considerable. Very high waves with long, overhanging crests. The sea looks white, visibility is greatly reduced.
|
29 feet
|
11
|
64-72
|
56-63
|
Violent Storm
|
Extensive widespread damage. Wave edges are blown into froth, and the sea is covered with patches of foam.
|
37 feet
|
12
|
73+
|
64+
|
Hurricane
|
Extreme destruction, devastation. The air is filled with foam and spray, and the sea is completely white, little visibility.
|
45 feet
|
