Beaufort Wind Scale

Beauforts description and observation of wind and wind velocity

Sponsored Links

The Beaufort wind scale, which is used to describe the force of the wind, was invented by Admiral Beaufort in 1805. With some experience in the use of the scale the wind force can be estimated with reasonable accuracy.

The Beaufort wind scale is divided into series of values, from zero for calm winds, up to twelve and above for hurricanes. Each value represents a specific range and a classification of wind velocity with an accompanying descriptions of the effects on surface features.

Beaufort No.	Description of wind	Observation	Wind speed
			m/s	mph	knots	ft/min
0	Calm	Smoke rises vertically	0 - 0.15	0 - 0.3	0 - 0.5	0 - 25
1	Light Air	Direction of wind shown by smoke drift but not by vanes	0.15 - 2.7	0.3 - 6	0.5 - 3	25 - 525
2	Light Breeze	Wind felt on face, leaves rustle, ordinary vanes moved by wind	2.7 - 3.6	6 - 8	3 - 7	525 - 700
3	Gentle Breeze	Leaves and small twigs in constant motion, wind extends light flag	3.6 - 7.2	8 - 16	7 - 10	700 - 1400
4	Moderate Breeze	Raises dust and loose paper, small branches moved	7.2 - 8.9	16 - 20	10 - 15	1,400 - 1,800
5	Fresh Breeze	Small trees in leaf begin to sway	8.9 - 12.5	20 - 28	15 - 21	1,800 - 2,500
6	Strong Breeze	Large branches in motion, whistling heard in telegraph wires	12.5 - 14.5	28 - 32	21 - 27	2,500 - 2,800
7	Moderate gale	Whole trees in motion, inconvenience felt when walking into wind	14.5 - 20	32 - 44	27 - 33	2,800 - 3,900
8	Gale	Twigs broken of trees, generally impeded progress	20 - 22	44 - 50	33 - 40	3,900 - 4,400
9	Strong gale	Straight structural damage, e.g. slates and chimney pots removed from the roofs	22 - 28	50 - 62	40 - 48	4,400 - 5,450
10	Storm	Trees uprooted, considerable structural damage	28 - 31	62 - 70	48 - 55	5,450 - 6,150
11	Violent Storm	Widespread damage	31 - 37	70 - 82	55 - 63	6,150 - 7,200
12	Hurricane		> 37	> 82	> 63	> 7,200