Mels-Place.com - The Beaufort Wind Scale

The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort Wind Force Scale, although it is a measure of wind speed and not of force. The scale was devised in 1805 by Rear Admiral Sir Francis Beaufort, an Irish Royal Navy officer. In the early 19th century, naval officers made regular weather observations, but there was no standard scale and could be very subjective – one man's "stiff breeze" might be another's "soft breeze". Sir Beaufort succeeded in standardizing the scale.

The initial Beaufort Number descriptions related wind conditions to effects on the sails of a frigate, then the main ship of the Royal Navy. In 1916, to accommodate the growth of steam power, the descriptions were changed to how the sea, not the sails, behaved and extended to land observations.

Beaufort Number or Force	Wind Speed		Description	Effects on Land and Sea
Beaufort Number or Force	MPH	Knots	Description	Effects on Land and Sea
0	<1	<1	Calm	Still, calm air, smoke will rise vertically Water surface is mirror-like
1	1 to 3	1 to 3	Light Air	Rising smoke drifts, wind vane is inactive Small ripples appear on water surface
2	4 to 7	4 to 6	Light Breeze	Leaves rustle, can feel wind on your face, wind vanes begin to move Small wavelets develop, crests are glassy
3	8 to 12	7 to 10	Gentle Breeze	Leaves and small twigs move, light weight flags extend Large wavelets, crests start to break, some whitecaps
4	13 to 18	11 to 16	Moderate Breeze	Small branches move, raises dust, leaves and paper Small waves develop, becoming longer, whitecaps
5	19 to 24	17 to 21	Fresh Breeze	Small trees sway White crested wavelets (whitecaps) form, some spray
6	25 to 31	22 to 27	Strong Breeze	Large tree branches move, telephone wires begin to whistle, umbrellas are difficult to keep under control Larger waves form, whitecaps prevalent, spray
7	32 to 38	28 to 33	Moderate or Near Gale	Large trees sway, becoming difficult to walk Larger waves develop, white foam from breaking waves begins to be blown
8	39 to 46	34 to 40	Gale	Twigs and small branches are broken from trees, walking is difficult Moderately large waves with blown foam
9	47 to 54	41 to 47	Strong Gale	Slight damage occurs to buildings, shingles are blown off of roofs High waves (6 meters), rolling seas, dense foam. Blowing spray reduces visibility
10	55 to 63	48 to 55	Storm	Trees are broken or uprooted, building damage is considerable Large waves (6-9 meters), overhanging crests, sea becomes white with foam, heavy rolling, reduced visibility
11	64 to 72	56 to 63	Violent Storm	Extensive and widespread damage Large waves (9-14 meters), white foam, visibility further reduced
12	> 73	> 64	Hurricane	Extreme destruction and devastation Large waves over 14 meters, air filled with foam, sea white with foam and driving spray, little visibility