Mammatus

Mammatus, mammatocumulus or simply mamma are "pouch" -like clouds that form beneath another cloud. The term "mammatus" derives from mamma, due to its association with the shape of breasts or breasts.

They form in descending air, in contrast to the other clouds, which form in ascending air. Frequently, mammatus clouds form under the anvil of a Cumulonimbus, and are usually observed after their passing.

Mammatus are "dependent" clouds, as they exist only in association with other clouds.

Mammatus cloud formation is often associated with Cumulonimbus formation, but may also occur in association with Stratocumulus, Altocumulus, Altostratus, Cirrus and Cirrocumulus. They can also occur on condensation trails (artificial aircraft clouds) and volcanic dust clouds.

Mammatus clouds, when associated with a Cumulonimbus, are severe weather indicators, but in many cases indicate that the storm is losing strength. Mammatus are usually made of ice crystals, but can also be mixed or liquid.

Although they carry bad news, they are only messengers, appearing before and / or after a major weather change.