<- CIRRUS 



Code 1 



H2 : Dense cirrus in patches or twisted sheaves 

 usually not increasing; possibly but not 

 certainly the remains of the upper part of 

 cumulonimbus. 



<- CIRRUS 



Code 1 



H3: Cirrus, often anvil-shaped; either the 

 remains of the upper portions of cumulo- 

 nimbus or part of a distant cumulonimbus, 

 the rest of which is not visible. 



(See notes on L9 for coding requirements 

 when cumulonimbus is present.) 



<- CIRRUS 



Code 1 



H4: Cirrus (often hook-shaped) gradually 

 spreading over the sky and usually thicken- 

 ing as a whole. 



The essential characteristic is the gradual 

 spreading over the sky. 



Note that these clouds must extend to the 

 horizon from which they are advancing, 

 where owing to the effect of perspective they 

 may assume the appearance of cirrostratus. 



176 



H. O. 607 



