Ocean in Motion: Waves - Beaufort Wind Scale

Beaufort Wind Force	Wind Speed (Knots)	WMO* Wind Classification	Wave Height (ft)	Sea Conditions
0	Less than 1	Calm		Sea surface is smooth and mirror-like.
1	1-3	Light Air		Scaly ripples without foam crests.
2	4-6	Light Breeze		Small wavelets with glassy appearing crests and no breaking.
3	7-10	Gentle Breeze		Large wavelets, crests begin to break and whitecaps are scattered whitecaps.
4	11-16	Moderate Breeze	1-4	Small waves becoming longer and whitecaps are numerous.
5	17-21	Fresh Breeze	4-8	Moderate waves take longer form and there are many whitecaps and some spray.
6	22-27	Strong Breeze	8-13	Larger waves form and whitecaps are common, along with more spray.
7	28-33	Near Gale	13-20	The sea heaps up and white foam streaks off breakers.
8	34-40	Gale	13-20	Moderately high waves of greater length are formed. The edges of crests begin to break into spindrift and foam blown in streaks.
9	41-47	Strong Gale	20	High waves occur, the sea begins to roll and dense streaks of foam form. Spray may reduce visibility.
10	48-55	Storm	20-30	Very high waves form with overhanging crests. The sea is white with densely blown foam. There is heavy rolling and lowered visibility.
11	56-63	Violent Storm	30-45	Exceptionally high waves form and foam patches cover the sea. Visibility is more reduced.
12	64+	Hurricane	45	Exceptionally high waves. The air is filled with foam and the sea completely white with driving spray. Visibility greatly reduced.
* World Meteorological Organization