Figure B-19. Altocumulus. 



Figure B-22. Cumulus of considerable development, 

 generally towering. 



Figure B-20. Altocumulus. 



Figure B-23. Cumulonimbus. 



C* 



Figure B~21. Cumulus with little vertical develop- 

 ment and seemingly flattened. 



fort's scale given in table B-3 or use a jjortable 

 wind measuring set shown in figure B-27. 



The appearance of the sea surface serves as 

 the best means of estimating the true wind speed, 

 just as it aifords the best means of estimating 

 true wind direction. The direction can be deter- 

 mined by making use of the fact that the crest 



Figure 8-2^. 



Stratocumulus formed by spreading out 

 of cumulus. 



lines of the smallest ripples on the sea surface 

 are perpendicular to the direction of the wind. 

 These ripples are very sensitive to sudden 

 changes in character of the wind. Accentuation 

 of them by a localized increase in wind velocity 

 produces an apparent darkening of the sea sur- 

 face, wliich serves to show the rate of travel of 

 individual gusts or puffs. With wind forces of 

 6 (Beaufort) or more, the wind direction also 

 may be estimated correctly from the direction 



B-7 



