When The Sky Churns!
 Mammatus (also known as mammatocumulus,
meaning "bumpy clouds") is a meteorological term
applied to a cellular pattern of pouches hanging
underneath the base of a cloud. The name "mammatus"
is derived from the Latin mamma (breast), due to the
resemblance between the shape of these clouds and
human female breasts.
Mammatus are most often associated
with the anvil cloud that extends from a
cumulonimbus, but may also be found under
altocumulus, altostratus, stratocumulus, and cirrus
clouds, as well as contrails and volcanic ash
clouds. In the United States, sky gazers may
be most familiar with the very distinct and more
common cumulonimbus mammatus. When occurring in
cumulonimbus, mammatus are often indicative of a
particularly strong storm or maybe even a tornadic
storm. These tend to form more often during warm
months and over the midwest and eastern portions of
the United States, and more infrequently over the
west and southwest. Due to the intensely sheared
environment in which mammatus form, aviators are
strongly cautioned to avoid cumulonimbus with
mammatus.
Mammatus may appear as smooth, ragged or lumpy lobes
and may be opaque or semitransparent. Because
mammatus occur as a grouping of lobes, the way they
clump together can vary from an isolated cluster to
a field of mamma that spread over hundreds of
kilometers to being organized along a line, and may
be composed of unequal or similarly-sized lobes. The
individual mammatus lobe average diameters of 1-3 km
and lengths on average of 0.5 km. A lobe can last an
average of 10 minutes, but a whole cluster of mamma
can range from 15 minutes to a few hours. They
usually are composed of ice, but also can be a
mixture of ice and liquid water or be composed of
almost entirely liquid water.
Mammatus Gallery:
Also see: Planetary Boundary Layer: Turbulence |
