Beaufort Wind Scale
Devised by British Rear-Admiral, Sir Francis Beaufort in 1805
based on observations of the effects of the wind
Beaufort	Wind Speed		Wave	WMO*	Effects observed on the sea
number			height	description
(force)			(feet)
	knots	mph
0	under 1	under 1	-	Calm	Sea is like a mirror
1	1 - 3	1 - 3	0.25	Light air	Ripples with appearance of scales; no foam crests
2	4 - 6	4 - 7	0.5 - 1	Light breeze	Small wavelets; crests of glassy appearance, not breaking
3	7 - 10	8 - 12	03-Feb	Gentle breeze	Large wavelets; crests begin to break; scattered whitecaps
4	11 - 16	13-18		Moderate breeze	Small waves, becoming longer; numerous whitecaps
5	17-21	19-24	08-Jun	Fresh breeze	Moderate waves, taking longer form; many whitecaps; some spray
6	22-27	25-31	9½-13	Strong breeze	Larger waves forming; whitecaps everywhere; more spray
7	28-33	32-38	13½-19	Near gale	Sea heaps up; white foam from breaking waves begins to be blown in streaks
8	34-40	39-46	18-25	Gale	Moderately high waves of greater length; edges of crests begin to break into spindrift; foam is blown in well-marked streaks
9	41-47	47-54	23-32	Strong gale	High waves; sea begins to roll; dense streaks of foam; spray may begin to reduce visibility
10	48-55	55-63	29-41	Storm	Very high waves with overhanging crests; sea takes white appearance as foam is blown in very dense streaks; rolling is heavy and visibility is reduced
11	56-63	64-72	37-52	Violent storm	Exceptionally high waves; sea covered with white foam patches; visibility further reduced
12	64 and over	73 and over	45 and over	Hurricane	Air filled with foam; sea completely white with driving spray; visibility greatly reduced
* World Meteorological Organization