Met Office: CM1 Thin altostratus

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C_M1 Thin altostratus

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Gallery
© C.S. Broomfield	© S.G. Cornford
© C.S. Broomfield

Gallery

Thin altostratus usually evolves from the gradual thickening of a veil of cirrostratus. It nearly always appears as a layer of great horizontal extent. It is of a greyish or bluish colour, never white, and the greater part is always translucent enough to reveal the sun (or moon) as through ground glass. The ground glass effect can be seen in the three photographs in this page. Objects on the ground do not cast shadows, and halo phenomena are never seen. Pannus clouds C_L7 may occur. In their initial stages of formation, the pannus clouds are small, well separated and usually occur at a considerable distance below the altostratus. Sometimes, especially in the tropics, altostratus may form from the spreading out of the middle or upper part of a cumulonimbus.

Classification
Description: Altostratus, the greater part of which is semi-transparent; through which the sun or moon may be weakly visible as through ground glass.	Designation: C_M=1 (C4)
Latin name: Altostratus translucidus (As tr).

Classification

Description:
Altostratus, the greater part of which is semi-transparent; through which the sun or moon may be weakly visible as through ground glass.

Designation:
C_M=1 (C4)

Latin name:
Altostratus translucidus (As tr).