Beaufort Scale

BEAUFORT	WINDSPEED	DESCRIPTION	SEA CONDITION
FORCE	KNOTS

0	0	Calm	Sea like a mirror
1	1 - 3	Light Air	Ripples but without foam crests
2	4 - 6	Light Breeze	Small Wavelets. Crests do not break
3	7 - 10	Gentle Breeze	Large Wavelets. Perhaps scattered white horses
4	11 - 16	Moderate Breeze	Small waves. Fairly frequent white horses
5	17 - 21	Fresh Breeze	Moderate waves, many white horses
6	22 - 27	Strong Breeze	Large waves begin to form: white foam crests, probably spray
7	28 - 33	Near Gale	Sea heaps up and white foam blown in streaks along the direction
			of the wind
8	34 - 40	Gale	Moderate high waves, crests begin to break into spindrift
9	41 - 47	Strong Gale	High waves. Dence foam along the direction of the wind.
			Crests of waves begin to roll over. Spray may effect visibility
10	48 - 55	Storm	Very high waves with long overhanging crests. The surface of the
			sea takes a white appearance. The tumbling of the sea becomes
			heavy and shock like. Visibility affected
11	56 - 63	Violent Storm	Exceptionally high waves. The sea is completely covered with long
			white patches of foam lying in the direction of the wind.
			Visibility affected
12	64+	Hurricane	The air is filled with foam and spray. Sea completely white with
			driving spray. Visibility very seriously affected