Height of base:

above 5000 to 10000 m (16,500 – 30,000 ft) (high-level clouds)

Description:

Milky veil of high-level cloud;

Either smooth or vibrous

Cover large areas

Haloes, mock suns

Occurrence:

World-wide

Made of:

falling ice crystals

Precipitation:

None

Formation:

Joining of cirrus clouds

Species:

Fibratus, nebulosus

Varieties:

Undulatus, duplicatus

How to distinguish from …

Altostratus (As)

Cs is thinner and produces halo phenomena;

As only produces coronae

Cs allows a shadow to bee seen on ground

Cirrus and cirrocumulus (Ci, Cc)

Both have distinct elements, which Cs does not have

Cirrostratus fibratus and altocumulus castellanus

Morris, May 07

Cirrostratus fibratus

Morris, Jan07

Cirrostratus fibratus, note the circumzenithal arc

Morris, Jan 2008

Cirrostratus nebulosus, with halo

Morris, April5, 2008

Cirrostratus nebulosus, noticeable by its halo and corona effect.

Morris, May 18, 2008