Mammatus clouds in Tulsa, Oklahoma, 1973

These Mammatus clouds were photographed over Regina, Saskatchewan, Canada during the past summer. Mammatus (“mammary cloud” or “breast cloud”), is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud.    Image credit: wikimedia

Under some conditions, cloud pockets can develop, that contain large droplets of water or ice that fall into clear air as they evaporate.

As water droplets grow, an opaque cloud forms. Such pockets may occur in turbulent air near a thunderstorm. Resulting mammatus clouds, can appear especially dramatic if sunlit from the side.

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Mammatus clouds in Tulsa, Oklahoma, 1973   Image credit: wikimedia

Mammatus clouds forming in Minnesota in 2005Mammatus clouds forming in Minnesota in 2005   Image credit: wikimedia

Mammatus Clouds

Mammatus, also known as mammatocumulus, derived from the Latin mamma (meaning “udder” or “breast”), refers to a resemblance between the characteristic shape of these clouds and the breast of a woman.
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. 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 Clouds in San Francisco, CaliforniaMammatus Clouds in San Francisco, California   Image credit: wikimedia