Fire whirl

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Fire whirl
Fire whirl (FWS) crop.jpg
A fire whirl with flames in the vortex
Area of occurrenceWorldwide (most frequent in areas subject to wildfires)
SeasonAll year (most frequent in dry season)
EffectWind damage, burning, propagation/intensification of fires

A fire whirl, fire devil or fire tornado 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.

Contents

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 2,000 °F (1,090 °C). [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 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, contain wind speeds over 200 km/h (120 mph), and persist for more than 20 minutes. [5]

Fire whirls can uproot trees that are 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 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

A flame-filled fire whirl Fire-whirl.jpg
A flame-filled fire whirl

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 the phenomenon occurred in the aftermath of the 1923 Great Kantō earthquake in Japan, in which a city-wide firestorm in Tokyo produced the conditions required for a gigantic fire whirl that killed 38,000 people in fifteen minutes in the Hifukusho-Ato region of the city. [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 5 km (3.1 mi) 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 160 mph (260 km/h) and vertical air speed of 93 mph (150 km/h), causing the flashover 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 the Enhanced Fujita scale. [27]

Dashcam video of the 2018 Carr Fire tornado

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 100 m (330 ft) high. [28]

On July 26, 2018, the massive 2018 Carr Fire tornado would hit Redding, California. [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. [33]

See also

Related Research Articles

<span class="mw-page-title-main">Tornado</span> Rotating air column connecting the Earth’s surface and a cumulonimbus cloud

A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 180 kilometers per hour, are about 80 meters across, and travel several kilometers before dissipating. The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), can be more than 3 kilometers (2 mi) in diameter, and can stay on the ground for more than 100 km (62 mi).

<span class="mw-page-title-main">Cyclone</span> Large scale rotating air mass

In meteorology, a cyclone is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above. Cyclones are characterized by inward-spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes, and dust devils lie within the smaller mesoscale.

<span class="mw-page-title-main">Dust devil</span> Type of whirlwind

A dust devil is a strong, well-formed, and relatively short-lived whirlwind. Its size ranges from small to large. The primary vertical motion is upward. Dust devils are usually harmless, but can on rare occasions grow large enough to pose a threat to both people and property.

<span class="mw-page-title-main">Firestorm</span> High intensity conflagration

A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires and wildfires. Although the term has been used to describe certain large fires, the phenomenon's determining characteristic is a fire with its own storm-force winds from every point of the compass towards the storm's center, where the air is heated and then ascends.

<span class="mw-page-title-main">Ted Fujita</span> Japanese-American meteorologist (1920–1998)

Tetsuya Theodore Fujita was a Japanese and American meteorologist whose research primarily focused on severe weather. His research at the University of Chicago on severe thunderstorms, tornadoes, hurricanes, and typhoons revolutionized the knowledge of each. Although he is best known for creating the Fujita scale of tornado intensity and damage, he also discovered downbursts and microbursts and was an instrumental figure in advancing modern understanding of many severe weather phenomena and how they affect people and communities, especially through his work exploring the relationship between wind speed and damage.

<span class="mw-page-title-main">Polar vortex</span> Persistent cold-core low-pressure area that circles one of the poles

A circumpolar vortex, or simply polar vortex, is a large region of cold, rotating air; polar vortices encircle both of Earth's polar regions. Polar vortices also exist on other rotating, low-obliquity planetary bodies. The term polar vortex can be used to describe two distinct phenomena; the stratospheric polar vortex, and the tropospheric polar vortex. The stratospheric and tropospheric polar vortices both rotate in the direction of the Earth's spin, but they are distinct phenomena that have different sizes, structures, seasonal cycles, and impacts on weather.

<span class="mw-page-title-main">Funnel cloud</span> Funnel-shaped cloud not touching the ground

A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud base. Funnel clouds form most frequently in association with supercell thunderstorms, and are often, but not always, a visual precursor to tornadoes. Funnel clouds are visual phenomena, but these are not the vortex of wind itself.

<span class="mw-page-title-main">Multiple-vortex tornado</span> Tornado comprising multiple vortices

A multiple-vortex tornado is a tornado that contains several vortices revolving around, inside of, and as part of the main vortex. The only times multiple vortices may be visible are when the tornado is first forming or when condensation and debris are balanced such that subvortices are apparent without being obscured. They can add over 100 mph to the ground-relative wind in a tornado circulation and are responsible for most cases where narrow arcs of extreme destruction lie right next to weak damage within tornado paths.

<span class="mw-page-title-main">Fujiwhara effect</span> Meteorological phenomenon involving two cyclones circling each other

The Fujiwhara effect, sometimes referred to as the Fujiwara effect, Fujiw(h)ara interaction or binary interaction, is a phenomenon that occurs when two nearby cyclonic vortices move around each other and close the distance between the circulations of their corresponding low-pressure areas. The effect is named after Sakuhei Fujiwhara, the Japanese meteorologist who initially described the effect. Binary interaction of smaller circulations can cause the development of a larger cyclone, or cause two cyclones to merge into one. Extratropical cyclones typically engage in binary interaction when within 2,000 kilometres (1,200 mi) of one another, while tropical cyclones typically interact within 1,400 kilometres (870 mi) of each other.

<span class="mw-page-title-main">Landspout</span> Tornado not originating from a mesocyclone

Landspout is a term created by atmospheric scientist Howard B. Bluestein in 1985 for a tornado not associated with a mesocyclone. The Glossary of Meteorology defines a landspout:

<span class="mw-page-title-main">Eye (cyclone)</span> Central area of calm weather in a tropical cyclone

The eye is a region of mostly calm weather at the center of a tropical cyclone. The eye of a storm is a roughly circular area, typically 30–65 kilometers in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weather and highest winds of the cyclone occur. The cyclone's lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm.

<span class="mw-page-title-main">Cumulonimbus flammagenitus</span> Thunderstorm cloud that forms above a heat source

The cumulonimbus flammagenitus cloud (CbFg), also known as the pyrocumulonimbus cloud, is a type of cumulonimbus cloud that forms above a source of heat, such as a wildfire, nuclear explosion, or volcanic eruption, and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of a flammagenitus cloud. According to the American Meteorological Society’s Glossary of Meteorology, a flammagenitus is "a cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process."

<span class="mw-page-title-main">Tornadogenesis</span> Process by which a tornado forms

Tornadogenesis is the process by which a tornado forms. There are many types of tornadoes, varying in methods of formation. Despite ongoing scientific study and high-profile research projects such as VORTEX, tornadogenesis is a volatile process and the intricacies of many of the mechanisms of tornado formation are still poorly understood.

<span class="mw-page-title-main">Corn Belt derecho</span> Weather event

The Corn Belt derecho was a progressive derecho which affected a large area of the central United States on June 29, 1998. In the morning, thunderstorms, including a supercell, developed over South Dakota and tracked into central Iowa. As the thunderstorms reached central Iowa, a strong rear-inflow jet developed which caused the thunderstorm to take on a different characteristic, becoming a derecho. It traveled more than 600 miles in about ten hours, causing more than $125 million worth of widespread damage destruction, especially to crops, and was responsible for power outages to nearly a half a million people.

<span class="mw-page-title-main">Whirlwind</span> Meteorological phenomenon

A whirlwind is a phenomenon in which a vortex of wind forms due to instabilities and turbulence created by heating and flow (current) gradients. Whirlwinds can vary in size and last from a couple minutes to a couple hours.

<span class="mw-page-title-main">Tornado vortex signature</span> Weather radar pattern

A tornadic vortex signature, abbreviated TVS, is a Pulse-Doppler radar weather radar detected rotation algorithm that indicates the likely presence of a strong mesocyclone that is in some stage of tornadogenesis. It may give meteorologists the ability to pinpoint and track the location of tornadic rotation within a larger storm, and is one component of the National Weather Service's warning operations.

A mesovortex is a small-scale rotational feature found in a convective storm, such as a quasi-linear convective system, a supercell, or the eyewall of a tropical cyclone. Mesovortices range in diameter from tens of miles to a mile or less and can be immensely intense.

<span class="mw-page-title-main">Descending reflectivity core</span> Small-scale area of enhanced radar reflectivity

A descending reflectivity core (DRC), sometimes referred to as a blob, is a meteorological phenomenon observed in supercell thunderstorms, characterized by a localized, small-scale area of enhanced radar reflectivity that descends from the echo overhang into the lower levels of the storm. Typically found on the right rear flank of supercells, DRCs are significant for their potential role in the development or intensification of low-level rotation within these storms. The descent of DRCs has been associated with the formation and evolution of hook echoes, a key radar signature of supercells, suggesting a complex interplay between these cores and storm dynamics.

References

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  3. ↑ Chuah, Keng Hoo; K. Kuwana (2009). "Modeling a fire whirl generated over a 5-cm-diameter methanol pool fire". Combust. Flame. 156 (9): 1828–1833. Bibcode:2009CoFl..156.1828C. doi:10.1016/j.combustflame.2009.06.010.
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  7. ↑ Thorarinsson, Sigurdur; B. Vonnegut (1964). "Whirlwinds Produced by the Eruption of Surtsey Volcano". Bull. Am. Meteorol. Soc. 45 (8): 440–444. Bibcode:1964BAMS...45..440T. doi: 10.1175/1520-0477-45.8.440 (inactive 1 November 2024).{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link)
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  14. ↑ Williams, Forman (22 May 2009). "The Occurrence and Mechanisms of Fire Whirls" (PDF). La Lolla, California; Valladolid, Spain: MAE UCSD; Spanish Section of the Combustion Institute. Archived from the original (PDF) on 13 May 2014.
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  19. ↑ Tornadoes of Fire at Williamsonville, Wisconsin, October 8, 1871 Archived 9 October 2022 at Ghost Archive by Joseph M. Moran and E. Lee Somerville, 1990, Wisconsin Academy of Sciences, Arts, and Letters, 31 pp.
  20. ↑ Skiba, Justin (2 September 2016). "The Fire That Took Williamsonville". Door County Living. Archived from the original on 24 September 2020. Retrieved 22 January 2019.
  21. ↑ Tornado Memorial Park kiosk historical notes, also see p. 19 Archived 24 June 2021 at the Wayback Machine of the County C Park and Ride lot panel draft pdf
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  25. ↑ Church, Christopher R.; Snow, John T.; Dessens, Jean (1980). "Intense Atmospheric Vortices Associated with a 1000 MW Fire". Bull. Am. Meteorol. Soc. 61 (7): 682–694. Bibcode:1980BAMS...61..682C. doi: 10.1175/1520-0477(1980)061<0682:IAVAWA>2.0.CO;2 .
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  29. ↑ Erdman, Jonathan (3 August 2018). "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. Archived from the original on 5 August 2018. Retrieved 16 February 2019.
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  33. 1 2 Xiao, Huahua; Gollner, Michael J.; Oran, Elaine S. (2016). "From fire whirls to blue whirls and combustion with reduced pollution". Proceedings of the National Academy of Sciences. 113 (34): 9457–9462. arXiv: 1605.01315 . Bibcode:2016PNAS..113.9457X. doi: 10.1073/pnas.1605860113 . PMC   5003231 . PMID   27493219.
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