The pyrocumulonimbus cloud (pyroCb) is a type of cumulonimbus cloud that forms above a source of heat, such as a wildfire, and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of a pyrocumulus cloud. According to the American Meteorological Society’s Glossary of Meteorology, a pyrocumulus is "a cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process." Analogous to the meteorological distinction between cumulus and cumulonimbus, the pyrocumulonimbus is a fire-aided or –caused convective cloud, like a pyrocumulus, but with considerable vertical development. The pyroCb reaches the upper troposphere or even lower stratosphere and may involve precipitation (although usually light), hail, lightning, extreme low-level winds, and in some cases even tornadoes. The pyroCb was named following the discovery that extreme manifestations of this pyroconvection caused direct injection of large abundances of smoke into the lower stratosphere.  A pyrocumulonimbus may often form from the eruption column of a volcano.
Alternate spellings and abbreviations for pyrocumulonimbus that may be found in the literature include pyro-cumulonimbus, pyro-cb, pyro-Cb and pyrocb. The World Meteorological Organization does not recognize the pyrocumulonimbus as a distinct cloud type, but instead classifies it simply as cumulonimbus.
In 2002, various sensing instruments detected 17 distinct pyrocumulonimbi in North America alone.
2003 Canberra Firestorm
On the 18 of January 2003, a supercell thunderstorm formed from a pyrocumulonimbus cloud associated with a severe wildfire, during the 2003 Canberra bushfires in Canberra, Australia. The supercell resulted in a huge fire tornado, rated at EF3 on the fujita scale, the first confirmed violent fire tornado.[better source needed] The tornado and associated fire killed 4 people and injured 492.
- "AMS Glossary". American Meteorological Society. Retrieved 6 January 2012.
- Fromm, M.; Tupper, A.; Rosenfeld, D.; Servranckx, R.; McRae, R. (2006). "Violent pyro-convective storm devastates Australia's capital and pollutes the stratosphere". Geophysical Research Letters 33 (5). Bibcode:2006GeoRL..33.5815F. doi:10.1029/2005GL025161.
- Fromm, M.; Alfred, J.; Hoppel, K.; Hornstein, J.; Bevilacqua, R.; Shettle, E.; Servranckx, R.; Li, Z.; Stocks, B. (2000). "Observations of boreal forest fire smoke in the stratosphere by POAM III, SAGE II, and lidar in 1998". Geophysical Research Letters 27 (9): 1407. Bibcode:2000GeoRL..27.1407F. doi:10.1029/1999GL011200.
- Fromm, M.; Servranckx, R. (2003). "Transport of forest fire smoke above the tropopause by supercell convection". Geophysical Research Letters 30 (10). Bibcode:2003GeoRL..30j..49F. doi:10.1029/2002GL016820.
- Fire-Breathing Storm Systems
- Anja Taylor (6 June 2013). "Fire Tornado". Australian Broadcasting Corporation. Retrieved 6 June 2013.
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