C_L = 2

(a) TECHNICAL SPECIFICATION

Cumulus mediocris or congestus, with or without Cumulus of species fractus or humilis or Stratocumulus, all having their bases at the same level.

(b) EXPLANATION

Cumulus mediocris or congestus are Cumulus of moderate or strong vertical extent, generally with protuberances in the form of domes or towers:

(i) On days with fresh or strong wind, these Cumulus have irregular bases and may be ragged in places.

(ii) At middle latitudes, on hot days with a thundery tendency and also frequently at low latitudes (trade wind zones), Cumulus are generally of the species congestus. They have a clear-cut horizontal base and a bulging upper part resembling a cauliflower; these clouds are sometimes in the form of a tower, sometimes in the form of a complex mass of protuberances.

(iii) Cumulus congestus may sometimes give precipitation in the form of showers.

(iv) Sometimes, the turrets of Stratocumulus castellanus develop so strongly that they reach the stage of Cumulus mediocris or congestus; the coding is then C_L = 2, and not C_L = 5. An analogous evolution may occur in Altocumulus castellanus; the coding is then again C_L = 2, and not C_M = 8.