Altocumulus (Ac) - the name derives from the latin words altus = high and cumulus = mass or heap. Altocumulus is a member of the ten fundamental cloud types (or cloud genera). It is a middle-level cloud, thus they usually form between 2 to 7 kilometers (6,500 to 22,000 ft).

Ac cloud usually occur as a layer or patch of more or less separate cloudlets in the form of heaps, rolls or pancakes. They are white and/or gray in colour with generally shadowed parts or undersites and often show a waved aspect. They may be well shaped by high winds into lentels and might appear as a pancake tower or like an UFO, often sharply outlined, but they may also become partly fibrous and diffuse. They may or may not be merged.

Altocumulus clouds chiefly consist of water droplets, but ice crystals are often present. As they are extremely varied, they might occur in the cloud species: castellanus , floccus , lenticularis and stratiformis ; and the cloud varieties: duplicatus , lacunosus , opacus , perlucidus , radiatus , translucidus and undulatus .

Related feature:
Mackerel Sky