Sky Watching: Mammatus Clouds

Sky-watching has been a well-loved activity for thousands of years. Ancient farmers, hunters and sailors have looked to the sky for years, hoping to unlock the clues that foretell the coming weather conditions.

In 1896, the first edition of the International Cloud Atlas was published, allowing meteorologists and avid sky-watchers to classify and consistently name the different types of clouds.

Mammatus Clouds

Mammatus clouds are round, protrubing-looking structures that are found on the underside of a larger, parent cloud. They can occur with cirrus clouds, stratocumulus clouds, and cumulonimbus clouds.

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A number of theories have been developed regarding the processes that cause mammatus clouds. According to Dr. Forbes, the mammtus clouds are formed when ice crystals fall out of the cumulonimbus cloud's anvil. The ice crystals sublimate, or change from ice to water vapor as they fall, causing the surrounding air to thermodynamically cool. The cooled air becomes "negatively bouyant" and begins to sink, producing the punched-out look indicative of the mammatus cloud.

Often, mammatus clouds are spotted on the underside of the anvil of a cumulonimbus cloud.  While mammatus clouds are associated with severe weather, they do not produce severe weather themselves.

(MORE: Sky Watching Stratus Clouds | 10 Spectacular Clouds)

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