Mammatus, also known as mammatocumulus (meaning "mammary cloud" or "breast cloud"), 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 (meaning "udder" or "breast").
The characteristics
of Mammatus
are most often associated with the anvil cloud and also severe
thunderstorms. They often extend from the base of a cumulonimbus, but may also be found
under altocumulus, altostratus, stratocumulus, and cirrus clouds, as well as
volcanic ash clouds.[citation needed] 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. 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 translucent.
Because mammatus occur as a grouping of lobes, the way they clump together can
vary from an isolated cluster to a field of mammae 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.
True
to their ominous appearance, mammatus clouds are often harbingers of a coming
storm or other extreme weather system. Typically composed primarily of ice,
they can extend for hundreds of miles in each direction and individual
formations can remain visibly static for ten to fifteen minutes at a time.
While they may appear foreboding they are merely the messengers - appearing
around, before or even after severe weather.
