Themes > Science > Earth Sciences > Hydrology, Meteorology, Climatology > Meteorology / Climatology > Clouds and Precipitation > Cloud Types > Altocumulus Clouds 

Parallel bands or rounded masses 

Photograph by: Holle

Altocumulus may appear as parallel bands (top photograph) or rounded masses (bottom photograph). Typically a portion of an altocumulus cloud is shaded, a characteristic which makes them distinguishable from the high-level cirrocumulus. Altocumulus clouds usually form by convection in an unstable layer aloft, which may result from the gradual lifting of air in advance of a cold front. The presence of altocumulus clouds on a warm and humid summer morning is commonly followed by thunderstorms later in the day.

Information provided by: http://ww2010.atmos.uiuc.edu