Cirrus cloud spreading from the top of a dying cumulonimbus. Cirrus forms from tropical cyclones, and is commonly seen fanning out from the eyewalls of hurricanes. A large shield of cirrus and cirrostratus typically accompanies the high altitude outflow of hurricanes or typhoons, and these can make the underlying rain bands—and sometimes even the eye—difficult to detect in satellite photographs. Thunderstorms can form dense cirrus at their tops. As the cumulonimbus cloud in a thunderstorm grows vertically, the liquid water droplets freeze when the air temperature reaches the freezing point. The anvil cloud takes its shape because the temperature inversion at the
Flammagenitus (cloud) Flammagenitus (cloud) A flammagenitus, also known as a pyrocumulus cloud or fire cloud, is a dense cumuliform cloud associated with fire or volcanic eruptions that may produce dry lightning (lightning without rain). A flammagenitus is similar dynamically in some ways to a firestorm, and the two phenomena may occur in conjunction with each other. However, either may occur without the other. A flammagenitus cloud is produced by the intense heating of the air from the surface. The intense heat induces convection, which causes the air mass to rise to a point of stability, usually in the presence of moisture. Phenomena