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Boca Marina Yacht Club - Boating Resources - Beaufort Wind Scale
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Beaufort Wind Scale
The
Beaufort Wind Scale is a scale that is used by seamen and coastal
observers to estimate wind speed. The scale was created by British Rear
Admiral Sir Francis Beaufort in the year 1805, and it was derived from
his observations of sea conditions. It was especially important during
the 19th century, because no sophisticated wind speed-measuring
equipment was available at that time. Despite the introduction
of new technologies, it is still being used by seafarers today, and it
also applied to measure wind speed on land.
|
Force |
Wind
(Knots) |
WMO
Classification |
Appearance of Wind Effects |
|---|
|
On the Water |
On Land |
|---|
|
0 |
< 1 |
Calm |
Sea surface smooth and mirror-like |
Calm, smoke rises vertically |
| 1 |
1-3 |
Light Air |
Scaly ripples, no foam crests |
Smoke drift indicates wind direction, still wind vanes |
| 2 |
4-6 |
Light Breeze |
Small wavelets, crests glassy, no breaking |
Wind felt on face, leaves rustle, vanes begin to move |
| 3 |
7-10 |
Gentle Breeze |
Large wavelets, crests begin to break, scattered whitecaps |
Leaves and small twigs constantly moving, light flags extended |
| 4 |
11-16 |
Moderate Breeze |
Small waves 1-4 ft. becoming longer, numerous whitecaps |
Dust, leaves, and loose paper lifted, small tree branches move |
| 5 |
17-21 |
Fresh Breeze |
Moderate waves 4-8 ft taking longer form, many whitecaps, some spray |
Small trees in leaf begin to sway |
| 6 |
22-27 |
Strong Breeze |
Larger waves 8-13 ft, whitecaps common, more spray |
Larger tree branches moving, whistling in wires |
| 7 |
28-33 |
Near Gale |
Sea heaps up, waves 13-20 ft, white foam streaks off breakers |
Whole trees moving, resistance felt walking against wind |
| 8 |
34-40 |
Gale |
Moderately high (13-20 ft) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks |
Whole trees in motion, resistance felt walking against wind |
| 9 |
41-47 |
Strong Gale |
High waves (20 ft), sea begins to roll, dense streaks of foam, spray may reduce visibility |
Slight structural damage occurs, slate blows off roofs |
| 10 |
48-55 |
Storm |
Very high waves (20-30 ft) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility |
Seldom experienced on land, trees broken or uprooted, "considerable structural damage" |
| 11 |
56-63 |
Violent Storm |
Exceptionally high (30-45 ft) waves, foam patches cover sea, visibility more reduced |
|
| 12 |
64 + |
Hurricane |
Air filled with foam, waves over 45 ft, sea completely white with driving spray, visibility greatly reduced |
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History of the
Beaufort Scale
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