Cumulonimbus 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 occurring as a thunderstorm these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes, hazardous winds, and large hailstones. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell. Cumulonimbus is abbreviated Cb.
Cumulonimbus incus
A view from space of a silhouette of a cumulonimbus in the afterglow of the troposphere at Earth's horizon, below the blue afterglow of the ozone layer at the lower stratosphere.
Cumulonimbus calvus cloud in Monterrey, Mexico.
Cumulonimbus calvus
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature.
Cloudscape over Borneo, taken by the International Space Station
Windy evening twilight enhanced by the Sun's angle, can visually mimic a tornado resulting from orographic lift
Cirrus fibratus clouds in March
High cirrus upper-left merging into cirrostratus right and some cirrocumulus far right