C_H1 Ci filaments/hooks not invading sky

Click the small image for full size version.

Gallery
© R.D. Whyman	© R.K. Pilsbury
© R.D. Whyman	© C.S. Broomfield

The white, delicate, hair-like cirrus clouds of C_H 1 occur most often in nearly straight or somewhat curved filaments (top left photograph). The cloud height in this example was about 30,000 ft. Sometimes they are shaped like commas, topped with a hook or a tuft which is not rounded (top right). In this form they are popularly called mares' tails. The elements may sometimes be arranged in a manner suggesting a fish skeleton with a spinal column and filaments on either side (bottom left). Cirrus may also occur in parallel bands, sometimes broad, which owing to perspective may appear to converge towards the horizon (bottom right). The height of cirrus in these photographs was at least 20,000 ft.

The cirrus of C_H 1 doesn't progressively invade the sky. This type of cloud often occurs with other cirrus clouds, but the high cloud should be coded as C_H =1 only when the combined cover of all the filaments, strands and hooks exceeds the cover of all other cirrus clouds.

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