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