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.
|
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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