Plain English Meaning

A layer of medium-height clouds that look like patches or rows of small puffy lumps, often with gaps of blue sky between them.

Full Definition

A middle-altitude cloud type, generally found between about 6,500 and 20,000 feet AGL, appearing as white or gray patches, sheets, or layers of rounded masses or rolls. Altocumulus clouds are composed mostly of water droplets and often indicate moisture and instability at middle levels of the atmosphere.

Context Anchor

Seen in aviation weather study, preflight weather planning, and cloud identification when judging what kind of weather may be developing along a route.

Derivation

From Latin altus meaning 'high' and cumulus meaning 'heap' or 'pile.' The name signals what the cloud is: piled, lumpy clouds at a higher than ordinary cumulus — but not as high as . '' in cloud naming does not mean 'highest'; it means 'middle level.'