Cumulonimbus cloud

Genus of dense, towering vertical clouds

Cumulonimbus (from Latin cumulus 'heap' and nimbus 'rain cloud') is a dense, towering, vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents. Above the lower portions of the cumulonimbus the water vapor becomes ice crystals, such as snow and graupel, the interaction of which can lead to hail and to lightning formation, respectively. When causing thunderstorms, these clouds may be called thunderheads.

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