Fire whirl

A fire whirl, colloquially fire devil or fire tornado, is a phenomenon in which a fire, under certain conditions (depending on air temperature and currents), acquires a vertical vorticity and forms a whirl, or a tornado-like effect of a vertically oriented rotating column of air. Fire whirls may be whirlwinds separated from the flames, either within the burn area or outside it, or a vortex of flame, itself.

A fire whirl can make fires more dangerous. An extreme example is the 1923 Great Kantō earthquake in Japan which ignited a large city-sized firestorm and produced a gigantic fire whirl that killed 38,000 in fifteen minutes in the Hifukusho-Ato region of Tokyo.cite book |last=Quintiere |first=James G. |authorlink=James G. Quintiere |title=Principles of Fire Behavior |publisher=Thomson Delmar Learning |date=1998 |location= |isbn=0827377320 ] Another example is the numerous large fire whirls (some tornadic) that developed after lightning struck an oil storage facility near San Luis Obispo, California on April 7, 1926, several of which produced significant structural damage well away from the fire, killing two. Thousands of whirlwinds were produced by the four-day-long firestorm coincident with conditions that produced severe thunderstorms, in which the larger fire whirls carried debris 5 kilometers (3 mi) away.cite journal |last=Hissong |first=J. E. |title=Whirlwinds At Oil-Tank Fire, San Luis Obispo, Calif. |journal=Monthly Weather Review |volume=54 |issue=4 |pages=161–3 |date=Apr 1926 |url=http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0493(1926)54%3C161%3AWAOFSL%3E2.0.CO%3B2 |doi=10.1175/1520-0493(1926)54<161:WAOFSL>2.0.CO;2 |format=abstract |year=1926 ]

Most of the largest fire whirls are spawned from wildfires. They form when a warm updraft and convergence from the wildfire are present.cite journal |last=Umscheid |first=Michael E. |coauthors=J.P. Monteverdi, J.M. Davies |title=Photographs and Analysis of an Unusually Large and Long-lived Firewhirl |journal=Electronic Journal of Severe Storms Meteorology |volume=1 |issue=2 |date=2006 |url=http://www.ejssm.org/ojs/index.php/ejssm/issue/view/2 ] They are usually 10-50 meters (30-200 ft) tall, a few meters (~10 ft) wide, and last only a few minutes. However, some can be more than a kilometer (0.6 mile) tall, contain winds over 160 km/h (100 mph), and persist for more than 20 minutes.cite book |last=Grazulis |first=Thomas P. |authorlink=Thomas P. Grazulis |title=Significant Tornadoes 1680–1991: A Chronology and Analysis of Events |date=Jul 1993 |publisher=The Tornado Project of Environmental Films |location=St. Johnsbury, VT |isbn=1879362031 ]

These can also aid the 'spotting' ability of wildfires to propagate and start new fires.

See also

* Dust devil
* Landspout
* Pyrocumulus
* Tornado
* Steam devil

References

*
* [http://fire.nist.gov/bfrlpubs/fire98/art079.html Fire Whirl Simulations]

External links

* [http://www.wunderground.com/wximage/viewsingleimage.html?mode=singleimage&handle=Photo5150&number=178&album_id=51&thumbstart=0&gallery=#slideanchor Photo 1]
* [http://www.wunderground.com/wximage/viewsingleimage.html?mode=singleimage&handle=Fotoguy77&number=40&album_id=17&thumbstart=1&gallery=#slideanchor Photo 2]
* [http://www.wunderground.com/wximage/viewsingleimage.html?mode=singleimage&handle=Fotoguy77&number=39&album_id=16&thumbstart=1&gallery=#slideanchor Photo 3]