C_H = 6

(a) TECHNICAL SPECIFICATION

Cirrus (often in bands} and Cirrostratus, or Cirrostratus alone, progressively invading the sky; they generally thicken as a whole; the continuous veil extends more than 45° above the horizon, without the sky being totally covered.

(b) EXPLANATION

(i) Cirrostratus invading the sky progressively with its continuous part more than 45° above the horizon but not covering the sky completely.

(ii) The veil of the Cirrostratus may be preceded by Cirrus clouds often in long filaments (Cirrus fibratus) or shaped like commas (Cirrus uncinus), frequently arranged in bands crossing a part of the sky and seemingly converging towards one point or towards two opposite points of the horizon (variety radiatus).

(iii) Cirrus may also have a form resembling a fish skeleton (variety vertebratus).