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Altocumulus Clouds (Ac)

Middle Clouds (6,500 to 20,000 feet)

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Altocumulus (coarse lamb) clouds typically form at the edge of a large, ascending air mass. They may also form in turbulence (convection) in the middle cloud level. The appearance of fountain-like formations generally indicate the presence of both vertical and horizontal air flow. These relatively thin clouds typically occur as a patchy deck with waved bands, rolls or rounded masses. The clouds, made up of ice particles and/or very small water droplets, are usually sharply outlined and often appear as lumps. Mackerel skies are typically comprised of altocumulus clouds.

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Genera:  From the Latin altum (height, upper air) and cumulus (an accumulation, a heap, a pile)

 

Most Common Species:

castellanus (in the form of a castle tower)

floccus (tuft of wool, fluff or nap of a cloth)

lenticularis (a small lentil, a pea)

stratiformis (to extend, to spread or flatten out, to cover with a layer)

 

Related Weather: Precipitation likely when solid banks of altocumulus clouds are seen to move across the sky from south or west toward the east

 

Precipitation to be Expected:  Only rarely will these clouds generate any precipitation

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Unless otherwise noted, all photos taken from Der Karlsruher Wolkenatlas, 2001 and used with permission of the author, Bernhard Muhr.

 

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