Afire whirl,fire devil orfire tornado is awhirlwind induced by afire and often (at least partially) composed offlame orash. These start with a whirl ofwind, often made visible bysmoke, and may occur when intense rising heat and turbulent wind conditions combine to form whirlingeddies of air. These eddies can contract to atornado-likevortex that sucks in debris and combustible gases.
The phenomenon is sometimes labeled afire tornado,firenado,fire swirl, orfire twister, but these terms usually refer to a separate phenomenon where a fire has such intensity that it generates an actual tornado. Fire whirls are not usually classifiable as tornadoes as the vortex in most cases does not extend from the surface to cloud base. Also, even in such cases, those fire whirls very rarely are classic tornadoes, as theirvorticity derives from surfacewinds and heat-induced lifting, rather than from a tornadicmesocyclone aloft.[1]
A fire whirl consists of a burning core and a rotating pocket of air. A fire whirl can reach up to 2,000 °F (1,090 °C).[2] Fire whirls become frequent when awildfire, or especiallyfirestorm, creates its own wind, which can spawn large vortices. Evenbonfires often have whirls on a smaller scale and tiny fire whirls have been generated by very small fires in laboratories.[3]
Most of the largest fire whirls are spawned from wildfires. They form when a warmupdraft and convergence from the wildfire are present.[4] They are usually 10–50 m (33–164 ft) tall, a few meters (several feet) wide, and last only a few minutes. Some, however, can be more than 1 km (0.6 mi) tall, containwind speeds over 200 km/h (120 mph), and persist for more than 20 minutes.[5]
Fire whirls can uproot trees 15 m (49 ft) tall or more.[6] These can also aid the 'spotting' ability of wildfires to propagate and start new fires as they lift burning materials such as tree bark. These burning embers can be blown away from the fire-ground by the stronger winds aloft.
Fire whirls can be common within the vicinity of aplume during avolcanic eruption.[7][8] These range from small to large and form from a variety of mechanisms, including those akin to typical fire whirl processes, but can result inCumulonimbus flammagenitus (cloud) spawninglandspouts andwaterspouts[9] or even to develop mesocyclone-like updraft rotation of the plume itself and/or of the cumulonimbi, which can spawn tornadoes similar to those insupercells.[10] Pyrocumulonimbi generated by large fires on rare occasions also develop in a similar way.[11][1][12][13]
There are currently three widely recognized types of fire whirls:[14]
Type 1: Stable and centered over burning area.
Type 2: Stable or transient, downwind of burning area.
Type 3: Steady or transient, centered over an open area adjacent to an asymmetric burning area with wind.
There is evidence suggesting that the fire whirl in the Hifukusho-ato area, during the1923 Great Kantō earthquake, was of type 3.[15] Other mechanism and fire whirl dynamics may exist.[16] A broader classification of fire whirls suggested byForman A. Williams includes five different categories:[17]
Whirls generated by fuel distribution in wind
Whirls above fuels in pools or on water
Tilted fire whirls
Moving fire whirls
Whirls modified by vortex breakdown
The meteorological community views some fire-induced phenomena as atmospheric phenomena. Using thepyro- prefix, fire-induced clouds are calledpyrocumulus andpyrocumulonimbus. Larger fire vortices are similarly being viewed. Based on vortex scale, the classification terms ofpyronado,"pyrotornado", and"pyromesocyclone" have been proposed.[18]
During the 1871Peshtigo fire, the community of Williamsonville,Wisconsin, was burned by a fire whirl; the area where Williamsonville once stood is now Tornado Memorial County Park.[19][20][21]
An extreme example of the phenomenon occurred in the aftermath of the1923 Great Kantō earthquake in Japan, in which a city-widefirestorm inTokyo produced the conditions required for a gigantic fire whirl that killed 38,000 people in fifteen minutes in theHifukusho-Ato region of the city.[22]
Numerous large fire whirls (some tornadic) that developed afterlightning struck an oil storage facility nearSan Luis Obispo,California, on 7 April 1926, produced significant structural damage well away from the fire, killing two. Many whirlwinds were produced by the four-day-long firestorm coincident with conditions that produced severethunderstorms, in which the larger fire whirls carried debris 5 km (3.1 mi) away.[23]
Throughout the 1960s and 1970s, particularly in 1978–1979, fire whirls ranging from the transient and very small to intense, long-lived tornado-like vortices capable of causing significant damage were spawned by fires generated from the 1000MWMétéotron, a series of large oil wells located in theLannemezan plain ofFrance used for testing atmospheric motions and thermodynamics.[25]
During the2003 Canberra bushfires inCanberra,Australia, a violent fire whirl was documented. It was calculated to have horizontal winds of 160 mph (260 km/h) and vertical air speed of 93 mph (150 km/h), causing theflashover of 300 acres (120 ha) in 0.04 seconds.[26] It was the first known fire whirl in Australia to have EF3 wind speeds on theEnhanced Fujita scale.[27]
A fire whirl, of reportedly uncommon size for New Zealand wildfires, formed on day three of the2017 Port Hills fires inChristchurch. Pilots estimated the fire column to be 100 m (330 ft) high.[29]
On August 15, 2020, for the first time in its history, the U.S. National Weather Service issued a tornado warning for apyrocumulonimbus created by a wildfire nearLoyalton, California, capable of producing a fire tornado.[31][32][33]
On July 12, 2025, a strong and nearly stationary fire tornado was spawned from theDeer Creek wildfire inSan Juan County, Utah. Despite being rated EF2 and damaging a fire engine belonging to theBureau of Land Management, no injuries or fatalities would occur in relation to this fire tornado.[36][37]
In controlled small-scale experiments, fire whirls are found to transition to a mode of combustion called blue whirls.[38] The nameblue whirl was coined because the soot production is negligible, leading to the disappearance of the yellow color typical of a fire whirl. Blue whirls are partially premixed flames that reside elevated in the recirculation region of the vortex-breakdown bubble.[39] The flame length and burning rate of a blue whirl are smaller than those of a fire whirl.[38]
^Grazulis, Thomas P. (July 1993).Significant Tornadoes 1680–1991: A Chronology and Analysis of Events. St. Johnsbury, VT: The Tornado Project of Environmental Films.ISBN1-879362-03-1.
^Cunningham, Phillip; M. J. Reeder (2009). "Severe convective storms initiated by intense wildfires: Numerical simulations of pyro-convection and pyro-tornadogenesis".Geophys. Res. Lett.36 (12): L12812.Bibcode:2009GeoRL..3612812C.doi:10.1029/2009GL039262.S2CID128775258.
^Kinniburgh, David C.; M. J. Reeder; T. P. Lane (2016). "The dynamics of pyro-tornadogenesis using a coupled fire-atmosphere model".11th Symposium on Fire and Forest Meteorology. Minneapolis, MN: American Meteorological Society.
^Williams, Forman A. (2020). "Scaling considerations for fire whirls".Progress in Scale Modeling.1 (1):1–4.doi:10.13023/psmij.2020.02.
^McCarthy, Patrick; Cormier, Leanne (23 September 2020)."Proposed Nomenclature for Fire-induced Vortices".CMOS BULLETIN SCMO. Canadian Meteorological and Oceanographic Society.Archived from the original on 20 October 2020. Retrieved18 October 2020.
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