What Kind of Weather Does an Altocumulus Bring?

Composition

• The formation of altocumulus clouds indicates unstable air. Altocumulus clouds consist of liquid droplets of water, ice crystals or some combination of both, according to the National Weather Service. The composition depends on factors such as altitude, the vertical temperature structure or various temperatures at different altitudes surrounding the clouds, and the time of year. For example, their presence can mean moist air is ascending, combined with dry air that is descending.

Cloud Formation

• If altocumulus clouds appear in the morning on a warm and humid day in the summer, thundershowers may occur in the afternoon. According to the Department of Atmospheric Science at the University of Illinois, altocumulus clouds form mostly by convection, or air moving vertically up or down. Air that is warmer than surrounding air will rise while air that is cooler than surrounding air will sink. Thermals, or warm air bubbles, can rise to greater heights before forming clouds if cool air occurs with warm air at altitudes that are lower.

Air Movements

• The approach of a cold front will induce warmer air lower to the ground to rise and eventually cool then condense as it mixes with colder air at higher elevations. This leads to cloud formation. Altocumulus clouds are further classified according to shape, which can provide more information about air movements, according to the College of Engineering and Applied Science at the University of Wyoming.

Shapes

• Altocumulus lenticularis are shaped like flat lenses; altocumulus undulatus resemble a series of ripples or waves. Altocumulus castellanus clouds, which are shaped like turrets from more air rising upwards, are more likely to lead to thunderstorms later. Altocumulus clouds may appear with other types of clouds at higher or lower elevations, depending on how the air is moving at different times. Altocumulus clouds occur between higher cirrus clouds and lower stratus clouds.