Mammatuscumulus clouds Mammatus Cumulus weather forecast nubes wolken Molnformationer Annuvola Nuages formørker

Mammatuscumulus clouds are strange-looking pouches that hang down from a thunderstorm anvil. Though most often gray, they can appear in a startling array of eerie colors, such as ghostly green or orange. Their pendant appearance suggests a funnel, but they have absolutely nothing to do with tornado formation -- except that, a robust storm with mammatus to its fore may well have a tornado lurking to its rear, somewhere. . .
Mammatus clouds form in sinking air. (Most clouds form in rising air.) Although mammatus most frequently form on the underside of a cumulonimbus, they can develop underneath cirrocumulus, altostratus, altocumulus, and stratocumulus. For a mammatus to form, the sinking air must be cooler than the air around it and have high liquid water or ice content. They derive their name from their appearance. The baglike sacs that hang beneath the cloud resemble cow's udders...