C_M = 8

(a) TECHNICAL SPECIFICATION

Altocumulus castellanus or Altocumulus floccus.

(b) EXPLANATION

(i) These two species of Altocumulus have a cumuliform appearance; this feature is more marked in Altocumulus castellanus than in Altocumulus floccus.

(ii) Altocumulus castellanus is composed of turrets that appear to be arranged in lines; the turrets generally have a common horizontal base, which gives the cloud a crenellated (castle battlement) appearance.

(iii) Altocumulus floccus occur in white or grey scattered tufts with rounded and slightly bulging upper parts; they are often accompanied by fibrous trails (virga). These clouds resemble very small, more or less ragged Cumulus.

(iv) When some of the Altocumulus castellanus or floccus present develop into Cumulus mediocris or congestus, or into Cumulonimbus, they become subject to the rules for coding C_L clouds.