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Beaufort Scale

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Beaufort Wind Force Scale
The Beaufort wind force scale was created by Rear-Admiral, Sir Francis Beaufort, around 1805 when he was a captain in the Royal Navy. The scale was designed to gauge wind speed using observations of the winds effects on a sailing ship and other objects when one was without the benefit of expensive equipment.


Force Wind Speed WMO Wind Speed Indicators
MPH Knots Km/H Desc At Sea On Land
0
<1
<1
<3
Calm
Ripples with appearance of scales; no foam crests
Smoke drift indicates wind direction; vanes do not move
1
1-3
1-3
1-5
Long Air
Small wavelets; crests of glassy appearance
Wind felt on face; leaves rustle; vanes begin to move
2
4-7
4-6
6-11
Light Breeze
Small wavelets; crests of glassy appearance
Wind felt on face; leaves rustle; vanes begin to move
3
8-12
7-10
12-29
Gentle Breeze
Large wavelets; crests begin to break, scattered whitecaps
Leaves & small twigs in motion; light flags extended
4
13-18
11-16
20-29
Moderate Breeze
1-4 ft. waves; numerous whitecaps
Leaves, & loose paper raised up; flags flap; small branches move.
5
19-24
17-21
30-38
Fresh Breeze
4-8 ft waves; many whitecaps; some spray
Small trees begin to sway; flags flap & ripple
6
25-31
22-27
39-50
Strong Breeze
8-13 ft waves forming white caps everywhere; more spray
Large branches in motion; whistling heard in wires
7
32-38
29-33
51-61
Near Gale
13-20 ft. waves; white foam blows in streaks
Whole trees in motion; resistance felt in walking against wind
8
39-46
34-40
62-74
Gale
13-20 ft. waves; edges of crests begin to break; foam in streaks
Whole trees in motion; resistance felt in walking against wind
9
47-54
41-47
75-86
Strong Gale
20 ft. waves; sea begins to roll; dense streaks of foam; spray may affect visibility
Slight structural damage occurs; shingles blow from roofs
10
55-63
48-55
87-101
Storm
20-30 ft. waves; white churning sea; rolling is heavy; reduced visibility
Trees broken or uprooted; considerable structural damage occurs
11
64-74
56-63
102-120
Violent Storm
30-45 ft. waves; white foam patches; visibility affected
Widespread damage to trees & buildings
12
75+
64+
120+
Hurricane
45 ft.+ waves; white sea; driving spray; visibility seriously affected
Severe & extensive damage






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