Abbreviation Ci
Family A
Genus Cirrus
Occurrence Worldwide
Altitude >5000m, in troposphere
Formation Saturation of upper-level air mass
Precipitation Virga may be produced
Potential Hazards Indicates an approaching frontal system or decayed thunderstorm

Cirrus (Ci; Latin for wisp of hair) is a genus of clouds characterized by occurrence in high altitudes and by appearing to consist of fibrous or wispy strands. Cirrus clouds are composed of millions of ice crystals blown into streaks by high-level winds, and they indicate the presence of moisture high in the troposphere.

Cirrus clouds were first described in 1802 by Luke Howard as "parallel, flexuous or diverging fibres extensible by increase in any or all directions."

Subtypes Edit

Cirrus castellated
Cirrus duplicatus
Cirrus fibratus
Cirrus floccus
Cirrus intortus
Cirrus Kelvin-Helmholtz
Cirrus with mammatus
Cirrus radiatus
Cirrus spissatus
Cirrus uncinus
Cirrus vertebratus

High Clouds (Family A): Cirrus (Ci) • Cirrus aviaticus • Cirrus intortus • Cirrus radiatus • Cirrus uncinus • Cirrus Kelvin-Helmholtz • Cirrostratus (Cs) • Cirrocumulus (Cc) • Pileus • Contrail
Middle Clouds (Family B): Altostratus (As) • Altostratus undulatus • Altocumulus (Ac) • Altocumulus undulatus • Altocumulus mackerel sky • Altocumulus castellanus • Altocumulus lenticularis
Low Clouds (Family C): Stratus (St) • Orographic stratus • Fog • Nimbostratus (Ns) • Cumulus humilis (Cu) • Cumulus mediocris (Cu) • Stratocumulus (Sc)
Vertical Clouds (Family D): Cumulonimbus (Cb) • Cumulonimbus incus • Cumulonimbus calvus • Cumulonimbus with mammatus • Cumulus congestus • Cumulus castellanus • Pyrocumulus  • Pyrocumulonimbus