Altocumulus

Altocumulus are banks, sheets or layers of white or gray clouds, or simultaneously white and gray, with altitudes between 2 and 6 km, having their own shadows. They constitute the so-called "red hot sky".

Altocumulus are usually composed only of water droplets (there may rarely be ice crystals) and they appear in parallel bands, in distinct round masses, or often partly fibrous or diffuse in appearance, with mixed or unmixed elements arranged quite regularly. . These elements are usually formed by convection and usually indicate an approaching cold front.

They form in unstable air masses when, at their altitude, humidity is moderate and temperature is relatively high. They look like Stratocumulus, but are at higher altitude and have smaller cells. The fact that you see some shadows on them shows that they are not, however, high clouds (altitude greater than 6 km). They cause the phenomenon of corona and iridescence when its edge passes through the sun or moon. On humid and hot summer mornings are usually a hint of thunder during the day.

Altocumulus are often observed simultaneously at two or more levels (Altocumulus duplicatus), meaning that this cloud occurs over a wide range of altitudes.

They almost always form as a result of turbulence or convection at medium levels from the transformation of Altostratus and Nimbostratus and the development of a Cumulus or Stratocumulus at low levels, but sometimes they are formed at higher levels. This can be from the increase of Cirrocumulus or from Cumulonimbus.

Subtypes
Altocumulus castellanus

Altocumulus floccus

Altocumulus stratiformis

Altocumulus undulatus

Altocumulus radiatus

Altocumulus lacunosus

Altocumulus duplicatus

Altocumulus translucidus

Altocumulus perlucidus

Altocumulus opacus

Altocumulus lenticularis

Altocumulus cumulogenitus