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
Wall cloud warm, moist air rises and converges, overpowering wet, rain-cooled air from the normally downwind downdraft. As the warm air continues to entrain the cooler air, the air temperature drops and the dew point increases (thus the dew point depression decreases). As this air continues to rise, it becomes more saturated with moisture, which results in additional cloud condensation, sometimes in the form of a wall cloud. Wall clouds may form as a descending of the cloud base or may form as rising scud comes together and connects to the storm's cloud base. Wall clouds can be anywhere from a fraction