Cumulonimbus flammagenitus (cloud) column of a volcano. In 2002, various sensing instruments detected 17 distinct cumulonimbus flammageniti in North America alone. Alternate spellings and abbreviations for cumulonimbus flammagenitus that may be found in the literature include Cb-Fg, pyrocumulonimbus, pyro-cumulonimbus, pyroCb, pyro-Cb, pyrocb, and pyro-cb. The World Meteorological Organization does not recognize the cumulonimbus flammagenitus as a distinct cloud type, but instead classifies it simply as cumulonimbus. On 18 January 2003, a supercell thunderstorm formed from a cumulonimbus flammagenitus cloud associated with a severe wildfire, during the 2003 Canberra bushfires in Canberra, Australia. The supercell resulted in a large fire tornado, rated at EF3
Funnel cloud example, is also a form of "tuba". Cold-air funnel clouds (vortices) are usually short-lived and generally much weaker than the vortices produced by supercells. Although cold-air funnels rarely make ground contact, they may touch down briefly and become weak tornadoes or waterspouts. Unlike the related phenomenon associated with severe thunderstorms, cold-air funnels are generally associated with partly cloudy skies in the wake of cold fronts, where atmospheric instability and moisture is sufficient to support towering cumulus clouds but not precipitation. The mixing of cooler air in the lower troposphere with air flowing in a different direction in the middle troposphere