Fire whirl explained

Fire whirl
Area Of Occurrence:Worldwide (most frequent in areas subject to wildfires)
Season:All year (most frequent in dry season)
Effect:Wind damage, burning, propagation/intensification of fires

A fire whirl or fire devil is a whirlwind induced by a fire and often (at least partially) composed of flame or ash. These start with a whirl of wind, often made visible by smoke, and may occur when intense rising heat and turbulent wind conditions combine to form whirling eddies of air. These eddies can contract to a tornado-like vortex that sucks in debris and combustible gases.

The phenomenon is sometimes labeled a fire tornado, firenado, fire swirl, or fire 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 their vorticity derives from surface winds and heat-induced lifting, rather than from a tornadic mesocyclone aloft.[1]

The phenomenon was first verified in the 2003 Canberra bushfires and has since been verified in the 2018 Carr Fire in California and 2020 Loyalton Fire in California and Nevada.

Formation

A fire whirl consists of a burning core and a rotating pocket of air. A fire whirl can reach up to 2000F.[2] Fire whirls become frequent when a wildfire, or especially firestorm, creates its own wind, which can spawn large vortices. Even bonfires 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 warm updraft and convergence from the wildfire are present.[4] They are usually 10m–50mm (30feet–160feetm) tall, a few meters (several feet) wide, and last only a few minutes. Some, however, can be more than 1sigfig=1NaNsigfig=1 tall, contain wind speeds over 200km/h, and persist for more than 20 minutes.[5]

Fire whirls can uproot trees that are 15m (49feet) 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 a plume during a volcanic 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 in Cumulonimbus flammagenitus (cloud) spawning landspouts and waterspouts[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 in supercells.[10] Pyrocumulonimbi generated by large fires on rare occasions also develop in a similar way.[11] [1] [12] [13]

Classification

There are currently three widely recognized types of fire whirls:[14]

There is evidence suggesting that the fire whirl in the Hifukusho-ato area, during the 1923 Great Kantō earthquake, was of type 3.[15] Other mechanism and fire whirl dynamics may exist.[16] A broader classification of fire whirls suggested by Forman A. Williams includes five different categories:[17]

The meteorological community views some fire-induced phenomena as atmospheric phenomena. Using the pyro- prefix, fire-induced clouds are called pyrocumulus and pyrocumulonimbus. Larger fire vortices are similarly being viewed. Based on vortex scale, the classification terms of pyronado, "pyrotornado", and "pyromesocyclone" have been proposed.[18]

Notable examples

During the 1871 Peshtigo 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 a fire whirl is the 1923 Great Kantō earthquake in Japan, which ignited a large city-sized firestorm which in turn produced a gigantic fire whirl that killed 38,000 people in fifteen minutes in the Hifukusho-Ato region of Tokyo.[22]

Numerous large fire whirls (some tornadic) that developed after lightning struck an oil storage facility near San 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 severe thunderstorms, in which the larger fire whirls carried debris 5km (03miles) away.[23]

Fire whirls were produced in the conflagrations and firestorms triggered by firebombings of European and Japanese cities during World War II and by the atomic bombings of Hiroshima and Nagasaki. Fire whirls associated with the bombing of Hamburg, particularly those of 27–28 July 1943, were studied.[24]

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 1000 MW Météotron, a series of large oil wells located in the Lannemezan plain of France used for testing atmospheric motions and thermodynamics.[25]

During the 2003 Canberra bushfires in Canberra, Australia, a violent fire whirl was documented. It was calculated to have horizontal winds of 160mph and vertical air speed of 93mph, causing the flashover of in 0.04 seconds.[26] It was the first known fire whirl in Australia to have EF3 wind speeds on the Enhanced Fujita scale.[27]

A fire whirl, of reportedly uncommon size for New Zealand wildfires, formed on day three of the 2017 Port Hills fires in Christchurch. Pilots estimated the fire column to be 100m (300feet) high.[28]

Residents in the city of Redding, California, while evacuating the area from the massive Carr Fire in late July 2018, reported seeing pyrocumulonimbus clouds and tornado-like behaviour from the firestorm, resulting in uprooted trees, cars, structures and other wind related damages in addition to the fire itself. As of August 2, 2018, a preliminary damage survey, led by the National Weather Service (NWS) in Sacramento, California, suggested the July 26th fire whirl was equivalent to an EF3 tornado with winds in excess of 143mph.[29]

On August 15, 2020, for the first time in its history, the U.S. National Weather Service issued a tornado warning for a pyrocumulonimbus created by a wildfire near Loyalton, California, capable of producing a fire tornado.[30] [31] [32]

Blue whirl

In controlled small-scale experiments, fire whirls are found to transition to a mode of combustion called blue whirls.[33] The name blue 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.[34] The flame length and burning rate of a blue whirl are smaller than those of a fire whirl.

See also

Further reading

External links

Notes and References

  1. McRae . Richard H. D. . J. J. Sharples . S. R. Wilkes . A. Walker . An Australian pyro-tornadogenesis event . Nat. Hazards . 65 . 3 . 1801–1811 . 2013 . 10.1007/s11069-012-0443-7 . 2013NatHa..65.1801M . 51933150 .
  2. Fortofer, Jason (20 September 2012) "New Fire Tornado Spotted in Australia" National Geographic
  3. Chuah . Keng Hoo . K. Kuwana . Modeling a fire whirl generated over a 5-cm-diameter methanol pool fire . Combust. Flame . 156 . 9 . 1828–1833 . 2009 . 10.1016/j.combustflame.2009.06.010 . 2009CoFl..156.1828C .
  4. Umscheid . Michael E. . Monteverdi . J.P. . Davies . J.M. . Photographs and Analysis of an Unusually Large and Long-lived Firewhirl . . 1 . 2 . 2006 . 1–13 . 10.55599/ejssm.v1i2.3. free .
  5. Book: Grazulis, Thomas P. . Thomas P. Grazulis . Significant Tornadoes 1680–1991: A Chronology and Analysis of Events . July 1993 . The Tornado Project of Environmental Films . St. Johnsbury, VT . 1-879362-03-1 .
  6. Book: Otways Fire No. 22 – 1982/83 Aspects of fire behaviour. Research Report No.20 . Victoria Department of Sustainability and Environment . PDF . June 1983 . 2012-12-19 . Billing . P. . 3 May 2013 . https://web.archive.org/web/20130503091620/http://www.dse.vic.gov.au/fire-and-other-emergencies/publications-and-research/fire-research-reports/research-report-20 . live .
  7. Thorarinsson . Sigurdur . B. Vonnegut . Whirlwinds Produced by the Eruption of Surtsey Volcano . Bull. Am. Meteorol. Soc. . 45 . 8 . 440–444 . 1964 . 10.1175/1520-0477-45.8.440 . 4 August 2024 . 1964BAMS...45..440T . free .
  8. Antonescu . Bogdan . D. M. Schultz . F. Lomas . Tornadoes in Europe: Synthesis of the Observational Datasets . Mon. Wea. Rev. . 144 . 7 . 2445–2480 . 2016 . 10.1175/MWR-D-15-0298.1 . free . 2016MWRv..144.2445A .
  9. Lareau . N. P. . N. J. Nauslar . J. T. Abatzoglou . The Carr Fire Vortex: A Case of Pyrotornadogenesis? . Geophys. Res. Lett. . 45 . 23 . 13107–13115 . 2018 . 10.1029/2018GL080667 . 2018GeoRL..4513107L . free .
  10. Chakraborty . Pinaki . G. Gioia . S. W. Kieffer . Volcanic mesocyclones . Nature . 458 . 7237 . 497–500 . 2009 . 10.1038/nature07866 . 19325632 . 2009Natur.458..497C . 1129142 .
  11. Cunningham . Phillip . M. J. Reeder . Severe convective storms initiated by intense wildfires: Numerical simulations of pyro-convection and pyro-tornadogenesis . Geophys. Res. Lett. . 36 . 12 . L12812 . 2009 . 10.1029/2009GL039262 . 2009GeoRL..3612812C . 128775258 .
  12. Fromm . Michael . A. Tupper . D. Rosenfeld . R. Servranckx . R. McRae . Violent pyro-convective storm devastates Australia's capital and pollutes the stratosphere . Geophys. Res. Lett. . 33 . 5 . L05815 . 2006 . 10.1029/2005GL025161 . 2006GeoRL..33.5815F . 128709657 . free .
  13. David C. . Kinniburgh . M. J. Reeder . T. P. Lane . The dynamics of pyro-tornadogenesis using a coupled fire-atmosphere model . 11th Symposium on Fire and Forest Meteorology . American Meteorological Society . 2016 . Minneapolis, MN .
  14. Web site: The Occurrence and Mechanisms of Fire Whirls. MAE UCSD; Spanish Section of the Combustion Institute. Williams, Forman. La Lolla, California; Valladolid, Spain. 22 May 2009. dead. https://web.archive.org/web/20140513010536/http://www.seic09.eis.uva.es/Presentaciones/IL4.pdf. 13 May 2014. dmy-all.
  15. Kuwana. Kazunori. Kozo . Sekimoto . Kozo . Saito . Forman A. . Williams . Scaling fire whirls . Fire Safety Journal . May 2008 . 43 . 4 . 252–7 . 10.1016/j.firesaf.2007.10.006 . 2008FirSJ..43..252K .
  16. Chuah . Keng Hoo . K. Kuwana . K. Saito . F. A. Williams . Inclined fire whirls . Proc. Combust. Inst. . 33 . 2 . 2417–2424 . 2011 . 10.1016/j.proci.2010.05.102 . 2011PComI..33.2417C .
  17. Williams . Forman A. . Scaling considerations for fire whirls . Progress in Scale Modeling . 1 . 1 . 1–4 . 2020 . 10.13023/psmij.2020.02.
  18. Web site: Patrick . McCarthy . Leanne . Cormier . Proposed Nomenclature for Fire-induced Vortices . CMOS BULLETIN SCMO . Canadian Meteorological and Oceanographic Society . 18 October 2020 . September 23, 2020 . 20 October 2020 . https://web.archive.org/web/20201020193046/https://bulletin.cmos.ca/nomenclature-for-fire-induced-vortices/ . live .
  19. http://images.library.wisc.edu/WI/EFacs/transactions/WT1990/reference/wi.wt1990.jmmoran.pdf Tornadoes of Fire at Williamsonville, Wisconsin, October 8, 1871
  20. News: The Fire That Took Williamsonville. Skiba. Justin. September 2, 2016. Door County Living. January 22, 2019. 24 September 2020. https://web.archive.org/web/20200924211214/https://doorcountypulse.com/fire-took-williamsonville/. live.
  21. https://web.archive.org/web/20200113055040/http://map.co.door.wi.us/parks/kiosks/Tornado.pdf Tornado Memorial Park
  22. Book: Quintiere, James G. . Principles of Fire Behavior . Thomson Delmar Learning . 1998 . 0-8273-7732-0 .
  23. Hissong . J. E. . Whirlwinds At Oil-Tank Fire, San Luis Obispo, Calif . Mon. Wea. Rev. . 54 . 4 . 161–3 . 1926 . 10.1175/1520-0493(1926)54<161:WAOFSL>2.0.CO;2 . 1926MWRv...54..161H . free .
  24. Ebert . Charles H. V. . The Meteorological Factor in the Hamburg Fire Storm . Weatherwise . 16 . 2 . 70–75 . 1963 . 10.1080/00431672.1963.9941009 . 1963Weawi..16b..70E .
  25. Church . Christopher R. . John T. . Snow . Jean . Dessens . Intense Atmospheric Vortices Associated with a 1000 MW Fire . Bull. Am. Meteorol. Soc. . 61 . 7 . 682–694 . 1980 . 10.1175/1520-0477(1980)061<0682:IAVAWA>2.0.CO;2 . 1980BAMS...61..682C . free .
  26. Web site: Fire tornado video. ACT Emergency Services. 28 November 2018. 28 November 2018. https://web.archive.org/web/20181128122637/http://esa.act.gov.au/emergency-management/fire-tornado-video/. live.
  27. News: California 'fire tornado' had 143mph winds, possibly state's strongest twister ever. USA Today. August 3, 2018. 28 November 2018. 28 November 2018. https://web.archive.org/web/20181128075429/https://www.usatoday.com/story/weather/2018/08/03/fire-tornado-california-carr-fire-143-mph-winds/897835002/. live.
  28. News: van Beynen . Martin . Firestorm . 12 March 2017 . . 11 March 2017 . C1–C4 . 12 March 2017 . https://web.archive.org/web/20170312005611/https://assets.stuff.co.nz/interactives/2017/firestorm/ . live .
  29. News: Erdman . Jonathan . The Giant Fire Whirl From California's Carr Fire Produced Damage Similar to an EF3 Tornado in Redding, an NWS Survey Found . The Weather Channel . August 3, 2018 . 16 February 2019 . 5 August 2018 . https://web.archive.org/web/20180805083134/https://weather.com/safety/wildfires/news/2018-08-03-fire-whirl-carr-fire-california-damage . live .
  30. Web site: A 'fire tornado' warning? Weather service issues what could be a first at California blaze . 16 August 2020 . 16 August 2020 . https://web.archive.org/web/20200816050603/https://www.sacbee.com/news/weather-news/article244993335.html . live .
  31. Web site: Daryl . Herzmann . IEM :: Valid Time Event Code (VTEC) App . mesonet.agron.iastate.edu . 14 September 2020 . en . 1 September 2020 . https://web.archive.org/web/20200901234400/https://mesonet.agron.iastate.edu/vtec/#2020-O-NEW-KREV-TO-W-0001/USCOMP-N0Q-202008152135 . live .
  32. Web site: Matthew Cappucci (September 13, 2020) California's wildfire smoke plumes are unlike anything previously seen . . 14 September 2020 . 14 September 2020 . https://web.archive.org/web/20200914140119/https://www.msn.com/en-us/weather/topstories/californias-wildfire-smoke-plumes-are-unlike-anything-previously-seen/ar-BB18Y54b?li=BBnb7Kz . live .
  33. Xiao . Huahua . Gollner . Michael J. . Oran . Elaine S. . From fire whirls to blue whirls and combustion with reduced pollution . Proceedings of the National Academy of Sciences . 2016 . 113 . 34 . 9457–9462 . 10.1073/pnas.1605860113. 27493219 . 5003231 . 1605.01315 . 2016PNAS..113.9457X . free .
  34. Coenen . Wilfried . Kolb . Erik J. . Sánchez . Antonio L. . Williams . Forman A. . Observed dependence of characteristics of liquid-pool fires on swirl magnitude . Combustion and Flame . July 2019 . 285 . 1–6 . 10.1016/j.combustflame.2019.03.032. 2202.06567 . 2019CoFl..205....1C . 132260032 .

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