Cirrostratus cloud

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Cirrostratus cloud
Cirrostratus with mock sun
Cirrostratus with mock sun
Abbreviation Cs
Genus Cirrus- "curl of hair" and
-stratus "layered"
Altitude Above 6000 m
(Above 20,000 ft)
Classification Family A (High-level)
Appearance white veil
Precipitation cloud? No, but usually signal the approach of a warm front.

Cirrostratus /ˌsɪrˈstrɑːtəs/ cloud is a high,very thin, generally uniform stratiform genus-type, composed of ice-crystals. It is difficult to detect and is capable of forming halos when the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no halos if it is thicker cirrostratus fibratus. On the approach of a frontal system, the cirrostratus often begins as nebulosus and turns to fibratus. If the cirrostratus begins as fragmented fibratus it often means the front is weak. Cirrostratus is usually located above 5.5 km (18,000 ft). Its presence indicates a large amount of moisture in the upper atmosphere.[1]

Cirrostratus at night causing a moon halo

Cirrostratus cloud sometimes signals the approach of a warm front if it forms after cirrus and spreads from one area across the sky and thus may be signs that precipitation might follow in the next 12 to 24 hours [2] or as soon as 6–8 hours if the front is fast moving. If the cirrostratus is broken fibratus it can mean that the front is weak and that stratus rather than nimbostratus will be the rain cloud (meaning drizzle instead of moderate rain). Cumulus humilis or stratocumulus clouds are often found below cirrostratus formations, this being due to the stable air associated with cirrostratus creating an inversion and restricting convection, causing cumuliform clouds to become flattened. Contrails also tend to spread out and can be visible for up to an hour in cirrostratus.

The phrase "hazy sunshine" is often, as well as referring to haze or light mist, used to refer to the milky look of the sky when cirrostratus is present.

See also[edit]

References[edit]

  1. ^ Ludlum, D. (1991). New York: Alfred A. Knopf. ISBN 0-679-40851-7.
  2. ^ Vekteris, Donna (2004). Scholastic Atlas of Weather. Scholastic Inc. p. 14. ISBN 0-439-41902-6. 

External links[edit]