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Cloud identification guide

(Section 2.7.2.1.2)
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Cumulonimbus

Cumulonimbus

Cb

 

Huge cloud tower, sometimes with anvil. Thunderstorm possible.

Yes
       
 
Yes
 
 
No
       
Yes
 
Cirrus

Cirrus

Ci

 

Hooks, feathers, bands or patches with silky shimmer.

   
 
No
 
 
No
 
 
Yes
   
Cumulus

Cumulus

Cu

 

Isolated, puffy cloud with sharp outlines.

 
No
   
   
 
Yes
 
 
No
   
Cirrostratus

Cirrostratus

Cs

 

Transparent milky or fibrous veil, casts shadow, produces halo.

Yes
 
Yes
Cirrocumulus

Cirrocumulus

Cc

 

Thin, pure white fields of small grains or ripples at a high level. Size < 1°

   
 
No
 
 
No
   
Altostratus

Altostratus

As

 

Smooth, extensive layer; casts no shadow, even if Sun/Moon is recognizable as a blurred dot.

Yes
 
Yes
Altocumulus

Altocumulus

Ac

 

White/grey patches (turreted, lens shaped or balls of cotton), sheets or structured layer with undulations or rolls. Size 1° - 3°

   
 
No
 
 
No
   
Nimbostratus

Nimbostratus

Ns

 

Dark rain cloud or bright snow cloud. Usually continuous rain, snow or ice pellets.

Yes
 
Stratocumulus

Grey or whitish fields, rolls or bundle, with rounded edges, at low level; regularly arranged elements. Size 5° - 10° (full hand)

   
   
 
No
       
   
Stratus

Stratus

St

 

Grey-whitish low layer, sometimes with drizzle or snow grains. If Sun/Moon is visible its outline is clear. Can occur in fragments.

       

Figure 10. Pictorial cloud identification guide

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