Table 2. --Determination of wind speed by sea condition (from USWB Circular M, 

 1954. p. 14) 



Wind force 

 (Beaufort) 



Speed 



in knots 



Descriptive terms 



Sea conditions 



10 



11 



12 



Less than 1 



1-3 



4-6 



7-10 



11-16 

 17-21 



22-27 



28-33 



34-40 



41-47 



48-55 



56-63 



64 and above 



Calm 

 Light air 

 Light breeze 



Gentle breeze 



Moderate breeze 

 Fresh breeze 



Strong breeze 



Moderate gale 



Fresh gale 



Strong gale 



Whole gale 



Stornn 



Hurricane 



Sea smooth and mirror-like 



Scale-like ripples without foam crests 



Small, short wavelets; crests have a glassy 

 appearance and do not break. 



Large wavelets; some crests begin to break; 

 foan-i of glassy appearance. Occasional 

 white foam crests. 



Small waves, becoming longer; far-rly frequent 

 white foam crests. 



Moderate waves, taking a nnore pronounced 

 long form; many white foam crests; there 

 may be some spray. 



Large waves begin to form; white foam crests 

 are more extensive everywhere; there may 

 be some spray. 



Sea heaps up and white foam from breaking 

 waves begins to be blown in streaks along 

 the direction of the wind; spindrift begins. 



Moderately high waves of greater length; edges 

 of crests break into spindrift; foam is blown 

 in well-marked streaks along the direction 

 of the wind. 



High waves; dense streaks of foam along the 

 direction of the wind; crests of waves begin 

 to topple, tumble, and roll over; spray nnay 

 reduce visibility. 



Very high waves with long overhanging crests. 

 The resulting foam in great patches is blown 

 in dense white streaks along the direction of 

 the wind. On the whole, the surface of the 

 sea is white in appearance. The tumbling of 

 the sea becomes heavy and shocklike. Visi- 

 bility is reduced. 



Exceptionally high waves that may obscure 



small and medium-sized ships. The sea is 

 completely covered with long white patches 

 of foam lying along the direction of the wind. 

 Everywhere the edges of the wave crests are 

 blown into froth. Visibility reduced. 



The air is filled with foam and spray. Sea 

 completely white with driving spray; visi- 

 bility very much reduced. 



