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
Altostratus undulatus cloud elements that have stretched through the sky. They often run parallel, but can also appear to interweave across the sky, especially if dual wave systems are seen (also referred to as biundulatus). Gravity waves aligned normally to the direction of the wind can show wide, near-parallel cloud strips. Altostratus undulatus cloud The altostratus undulatus is a type of altostratus cloud with signature undulations within it. These undulations may be visible (usually as "wavy bases"), but frequently they are indiscernible to the naked eye. These formations will generally appear in the early stages of destabilizing return flows, especially over the southern