Cloud If the air becomes more unstable, the cloud tends to grow vertically into the species "mediocris", then "congestus", the tallest cumulus species which is the same type that the International Civil Aviation Organization refers to as 'towering cumulus'. With highly unstable atmospheric conditions, large cumulus may continue to grow into cumulonimbus "calvus" (essentially a very tall congestus cloud that produces thunder), then ultimately into the species "capillatus" when supercooled water droplets at the top of the cloud turn into ice crystals giving it a cirriform appearance. All cloud varieties fall into one of two main groups. One group identifies 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