0 a type of cumulus (= a tall, rounded, white cloud with a flat base) found at medium height, above the level of cumulus --
In the middle tage are the alto clouds, which consist of the limiited-convective cumuliform or stratocumuliform cloud altocumulus and the stratiform cloud altostratus.
These include middle-tage layers of "altocumulus" and "altostratus" as well as low "stratocumulus", and "stratus".
The best-known is cumulonimbus with mammatus, but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus.
Altocumulus clouds can form via convection or via the forced uplift caused by a warm front.
In addition, the prevalence of altocumulus castellanus clouds was an indicator for additional severe weather later in the day.
All three are associated with the stratiformis species of altocumulus and stratocumulus.
There may be another rare type of altocumulus, altocumulus undulatus asperatus, but this has not been officially named yet.
An example of this would be an opaque layer of altocumulus stratiformis arranged in seemingly converging rows.
