Beaufort Wind Scale

Sir Francis Beaufort (1774–1857), a captain in the British Admiralty created the first version of his famous wind scales in 1806 for his own use. The Sea Conditions column describes observations used by mariners to estimate wind speeds since, prior to the advent of GPS, obtaining precise speeds from a (possibly) moving vessel was impossible.

Beaufort Number	Wind speed				Description	Wave Height	Sea Conditions	Land Conditions
Beaufort Number	kt	km/h	mph	m/s	Description	m/ft	Sea Conditions	Land Conditions
0	0	0	0	0-0.2	Calm	0/0	Flat	Calm, smoke rises vertically
1	1-3	1-6	1-3	0.3-1.5	Light Air	0.1/0.33	Ripples without crests	Wind motion visible in smoke
2	4-6	7-11	4-7	1.6-3.3	Light Breeze	0.2/0.66	Small wavelets, crests of glassy appearance, not breaking	Wind felt on exposed skin, leaves rustle
3	7-10	12-19	8-12	3.4-5.4	Gentle Breeze	0.6/2	Large wavelets, crests begin to break, scattered whitecaps	Leaves and smaller twigs in constant motion
4	11-16	20-29	13-18	5.5-7.9	Moderate Breeze	1/3.3	Small waves	Dust and loose paper raised. Small branches begin to move.
5	17-21	30-39	19-24	8.0-10.7	Fresh Breeze	2/6.6	Moderate (1.2 m) longer waves, some foam and spray	Smaller trees sway
6	22-27	40-50	25-31	10.8-13.8	Strong Breeze	3/9.9	Large waves with foam crests and some spray	Large branches in motion, whistling heard in overhead wires, umbrella use becomes difficult
7	28-33	51-62	32-38	13.9-17.1	Near Gale	4/13.1	Sea heaps up and foam begins to streak	Whole trees in motion, effort needed to walk against the wind
8	34-40	63-75	39-46	17.2-20.7	Gale	5.5/18	Moderately high waves with breaking crests forming spindrift, streaks of foam	Twigs broken from trees, cars veer on road
9	41-47	76-87	47-54	20.8-24.4	Strong Gale	7/23	High waves (2.75 m) with dense foam, wave crests start to roll over, considerable spray	Light structure damage
10	48-55	88-102	55-63	24.5-28.4	Storm	9/29.5	Very high waves, sea surface is white with considerable tumbling, visibility reduced	Trees uprooted. Considerable structural damage
11	56-63	103-117	64-72	28.5-32.6	Violent Storm	11.5/37.7	Exceptionally high waves	Widespread structural damage
12	>63	>117	>72	>32.7	Hurricane	14+/46+	Huge waves, air filled with foam and spray, sea completely white with driving spray, visibility very greatly reduced	Massive and widespread damage to structures

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