Soon it was out of sight amid the altocumulus clouds.

What little wind there was came from the east and the sky had few altocumulus clouds.

The altocumulus approach can sometimes be disturbing, for the cloud has a dark and somewhat frightening appearance.

Stratocumulus is also often, though not always, darker in colour than altocumulus.

Altocumulus now leaving from Tube 21V, departure time 1:03.

It is rare with altocumulus and extremely rare in its cirrocumulus form.

The presence of altocumulus undulatus may indicate precipitation within the next 20 hours or simply an overcast day.

All three are associated with the stratiformis species of altocumulus and stratocumulus.

"The weather at base is clear, scattered altocumulus about eight thousand, maybe, and the barometer is steady," he told me.

Like other cumulus clouds, altocumulus signifies convection.

Sweet fluffy altocumulus.

For these reasons, flight through Altocumulus Castellanus clouds is often best avoided by aircraft.

Altocumulus clouds can form via convection or via the forced uplift caused by a warm front.

Strato- is also excluded from altocumulus.

A mackerel sky or buttermilk sky describes a sky mostly covered by altocumulus clouds.

Altocumulus (Ac)

Rainshowers or thunderstorms may occur should any lower cumulus clouds reach the layer of the altocumulus form.

Altocumulus often are seen preceding a cold front, and their presence on a warm, humid, summer morning frequently signals the development of thunderstorms later in the day.

The altostratus undulatus is a type of low altocumulus cloud with signature undulations within it.

Altocumulus Castellanus clouds are typically accompanied by moderate turbulence as well as potential icing conditions.

An example of this would be an opaque layer of altocumulus stratiformis arranged in seemingly converging rows.

Similar clouds found at intermediate heights carry the prefix alto- resulting in the genus names altostratus and altocumulus.

This often does not apply when stratocumulus is of a broken, fractus form, when it may appear as small as altocumulus.

Altocumulus Castellanus (Source: Australiasevereweather.com)

Cirrocumulus is distinguished from altocumulus in several ways, although the two stratocumuliform genus types can occasionally occur together with no clear demarcation between them.