parallel bands or rounded masses
|Altocumulus clouds are composed primarily of water droplets and
are located between 6,500 and 20,000 feet (2,000 to 6,000
meters) above the ground.
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
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.
Also found at mid-levels are altostratus clouds, which
are often confused with high-level
One distinguishing feature is that a halo
is not observed around the sun (or moon) when viewed
through altostratus, but is a common feature associated
with cirrostratus clouds.
In fact, the sun (or moon) is only vaguely visible through
altostratus clouds and appears
as if it were shining through frosted glass.