CLOUD TYPES 



(Compiled by the U.S. Weather Bureau to aid in the interpretation of cloud observations.) 



FAMILY "A" HIGH CLOUDS: CIRRUS (Ci), CIRROCUMULUS (Cc). MEAN LOWER LEVEL, 6,000 METERS 



(20,000 FEET). 

 FAMILY "B" MIDDLE CLOUDS: ALTOCUMULUS (Ac), ALTOSTRATUS (As). MEAN UPPER LEVEL, 6,000 



METERS (20,000 FEET) ; MEAN LOWER LEVEL, 2,000 METERS (6,500 FEET). 



FAMILY "C" LOW CLOUDS : STRATOCUMULUS (Sc), STRATUS (St), NIMBOSTRATUS (Ns). MEAN UPPER 



LEVEL, 2,000 METERS (6,500 FEET); MEAN LOWER LEVEL, CLOSE TO SURFACE. 



FAMILY "D" CLOUDS WITH VERTICAL DEVELOPMENT; CUMULUS (Cu), CUMULONIMBUS (Cb). 



Figure B-2. Filaments or strands of cirrus scattered 

 and not increasing. 



Figure B-5. Cirrus (often hook-shaped) gradually 

 spreading over the sliy. 



Figure B~3. Dense cirrus in patches or twisted 

 sheaves usually not increasing. 



B-4 



Figure B-6. Cirrus and cirrostratus, often in bands 

 converging tov^ard the horizon. 



