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Height of base:

below 600 m (2000 ft) (low-level clouds)



cauliflower tops; fluffy rounded tops

flat bases

brilliant white; base can appear shadowed;


World-wide, except Antarctica (no thermals)

Made of:

water droplets, supercooled water droplets


None; cumulus congestus may precipitate brief showers


convection in instable layer (thermals), capped by stable layer


Humilis, mediocris, congestus, fractus



How to distinguish from

Stratocumulus (Sc)

Clouds are detached, not joined into layer

Altocumulus (Ac)

Wider than three fingers at stretched arm, 30 above horizon

Cumulonimbus (Cb)

Develops from congestus

Congestus has a sharp cauliflower outline, no softness from ice crystals


Cumulus humilis

(Hebgen Lake, Mt, June2006)

Cumulus mediocris

(Yellowstone Nat Park,

June 2006)

Cumulus congestus embedded in stratocumulus,

Altocumulus (Morris, June07)

Cumulus mediocris

Morris, May 07

Cumulus congestus

Glenwood, May 07

Cumulus humilis

Morris, May06

Cumulus fractus

Morris, May06

Cumulus humilis

Fountain geyser, Yellowstone NP, June06

Cumulus fractus

(Morris, May 2007)



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Last modified: 1/18/2008

Maintained by Sylke Boyd


The views and opinions expressed in this page are strictly those of the page author. The contents of this page have not been reviewed or approved by the University of Minnesota.