Figure B-16. Altocumulus formed by spreading out 

 of cumulus. 



Figwe B-13. Thin (semi transparent) altocumulus 



Figure B-lo. Altocimiulus in bauds. 



This tends to make the atmosphere thermally 

 stable and prevents active vertical mixing, 

 which in turn favors the production of haze and 

 fog at low levels. A stable atmosphere, there- 

 fore, is characterized by poor visibility and, if it 

 is sufficiently moist, by fog, low stratus clouds, 

 and drizzle. 



Observations of visibility should be recorded 

 on the A-Sheet in either meters and kilometers 



Figure B-IS. Altostratus and altocumulus. 



or yards and nautical miles. A2/ways indicate the 

 units of measurement. 



B-6 Wind Speed and Direction. — When a 

 ship is equipi)ed with an anemometer the true 

 wind speed is recorded in knots and the direction 

 in degrees true rather than magnetic, "\^^^en 

 observing aboard a ship without an anemometer, 

 estimate the wind speed in knots from the Beau- 



B-6 



