C_L3 Cumulonimbus without anvil

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Gallery
C.S. Broomfield (© Crown copyright)

The clouds of C_L3 are generally at an intermediate stage, representing a further development of C_L2 but not yet reaching the stage of C_L9.

Whilst the clear outlines and cauliflower shaped tops of C_L2 (see photograph) have at least partially disappeared, no part of the cloud top has acquired a fibrous appearance or any anvil development. The protuberances tend to form a whitish mass without striations.

Showers or thunderstorms may occur and cumulus, stratocumulus or status may also be present.

New cloud domes may be produced which make the cumulonimbus assume temporarily the appearance of towering cumulus C_L2. However it should still be called cumulonimbus and reported as C_L3. The occurrence of lightning, thunder or hail sometimes provides the only indication of the presence of a cumulonimbus. If, in this case, it is not possible to decide whether the cloud is C_L3 or C_L9, the coding is, by convention C_L=9.

Classification
Description: Cumulonimbus the summits of which lack sharp outlines but are neither clearly fibrous nor in the form of an anvil.	Designation: CL=3 (C9)
	Latin name: Cumulonimbus calvus (Cb cal).

Related pages: Cloud classification | C_L guide | C_M guide | C_H guide | Cloud index