User:Penitentes/Fire tornado (draft)

Fire tornado
Fire tornado
	Aerial view of an EF3-strength fire tornado generated by the 2018 Carr Fire in California
Area of occurrence	So far observed in North America and Australia
Effect	Wind damage, burning, propagation/intensification of fires

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Fire tornadoes, also called pyrotornadoes, are tornado-strength vortices generated by fires. Fire tornadoes are often confused with fire whirls, a smaller-scale phenomenon, being much rarer and much less well-understood. Few confirmed examples exist, all of them occurring in the 21st century. The mechanism that leads to their formation are not entirely understood, but are generally suggested by research to have roots in both fire and cloud processes, making them distinct from both fire whirls (common in wildfires) and traditional tornadoes, which typically form from the mesocyclone of a supercell thunderstorm.

Pyro-tornadogenesis was first scientifically identified following a destructive vortex that formed during a bushfire on the outskirts of Canberra, Australia, in 2003. The vortex was filmed by multiple bystanders at a distance but was not generally accepted as a genuine fire-generated tornado until 2012. Since then, several others have been recognized. One of the most famous examples of a fire tornado to date is the vortex that formed within a portion of the Carr Fire in 2018, in the suburbs of the city of Redding, California. That vortex was found to have generated wind speeds upwards of 143 miles per hour (230 km/h), equivalent in strength to a traditional EF3 tornado.

Definitions[edit]

There is no single widely accepted term as of yet for a fire tornado. The scientific literature contains multiple names for the phenomenon, including "pyrogenetic tornado",^[1] "fire-generated tornadic vortex (FGTV)",^[1] and "pyrotornado".^[2]

According to the American Meteorological Society's glossary of meteorology, a tornado is defined as "a rapidly rotating column of air extending vertically from the surface to the base of a cumuliform cloud."^[3]

The terms fire whirl and fire tornado have often been used interchangeably to describe a vortex of any size or duration occurring in a wildfire. Only in recent years have scientists begun to distinguish types of vortices from one another, in particular highlighting the rare cases of actual pyro-tornadogenesis (or tornado formation during/due to a wildfire).

One of the first formal attempts at creating a rigid nomenclature for vortices in fires was in a National Oceanic and Atmospheric Administration (NOAA) technical memorandum from 1978, where National Weather Service (NWS) meteorologist David W. Goens separated fire whirls into four general classes: fire devils (typically 3 to 33 feet in diameter with rotational velocities less than 22 mph), fire whirls (typically 33 to 100 feet, with rotational velocities of 22 to 67 mph), fire tornadoes (typically 100 to 1,000 feet in diameter with rotational velocities up to 90 MPH), and fire storms (1,000 to 10,000 feet in diameter with winds estimated in excess of 110 mph). Goens' classification did not enter general usage,^[4] but multiple attempts have been made in more recent years to suggest a consistent classification scheme.^[2]

Formation and structure[edit]

Formation[edit]

Fire whirls and fire tornadoes both must necessarily begin with a fire, the combustion from which heats the atmosphere directly above it. As that hot air warms it rises, forming a strong updraft.^[5] Updrafts as strong as 130 miles per hour have been found extending miles above the surface in pyrocumulonimbus clouds, equaling the strength of those found in tornado-producing supercell thunderstorms.^[6]

This rising hot air must be replaced at its base by cooler air, which generates a horizontal inflow jet, or winds converging from all directions towards the fire and the base of the primary updraft. The second ingredient is the presence of pre-existing wind shear, where air is flowing in different directions adjacent to the inflow winds. The wind shear provides the initial source of rotation. This rotation inhibits the dilution and mixing of air, allowing the column of rising air to act in a chimney-like fashion, strengthening the updraft, inflow winds, and surface combustion.^[5]

These are the basic underlying processes behind the development of all fire-related whirlwinds. Where fire tornadoes diverge from smaller and briefer fire whirls is in their development of a connection to a pyrocumulonimbus cloud. A pyrocumulonimbus cloud (often abbreviated in scientific literature as pyroCb) is a fire-generated thunderstorm, formed when the water vapor contained in the rising updraft and associated smoke plume rises high enough into the atmosphere to condense into liquid cloud droplets, forming distinctive bright white clouds. The process of condensation releases heat back into the atmosphere (called latent heat release). This is the same process that fuels an ordinary thunderstorm.^[5] Wildfires have long been known to be capable of generating severe convective storms, which in addition to the strong updrafts can also produce lightning and hail, though typically not precipitation.^[7]

The precise manner of the link between fire tornadoes and pyro-convection is unclear. It is currently hypothesized by researchers that the latent heat release in rapid pyrocumulonimbus development reinvigorates the updraft, and the heat release and updraft stretches the column and concentrates its pre-existing rotation (or 'vorticity') in the lower atmosphere, causing it to accelerate in much the same way a figure skater does when they pull their arms in. The involvement of the pyrocumulonimbus cloud in the development of fire tornadoes is what distinguishes those vortices from smaller-scale fire vortices, which concentrate their rotation solely through fire-related processes.^[8]^[1]

Need to describe CVPs, too:

"Like water flowing around a boulder in a stream, he found, wind is forced to split around the plume of superheated air and ash rising off a wildfire. And just like water flowing around a boulder, “these two eddies develop,” said Lareau, “which we call counterrotating vortices [CRVs]. Between those CRVs there’s this kind of wake—air moving back toward the fire in opposition to what the wind would be doing if the fire wasn’t there.”" from Eos article

Characteristics[edit]

Tend to be anticyclonic

The Canberra and Carr fire tornadoes, perhaps the two most intensively studied events, differed in key ways.^[9]

Embedded and shedding vortices[edit]

University of Nevada Reno scientist Neil P. Lareau and others published a research paper in 2022 that studied fire-generated tornadic vortices in the 2020 Loyalton, Creek, and Bear fires. The paper distinguished two distinct morphologies found among the vortices: some that remained embedded within the main fire, and some that 'detached' from the main fire and traveled 'downstream' while remaining pendant from the leaning smoke plume.^[1]

Impacts and hazards[edit]

Fire tornadoes are always associated with pyrocumulonimbus clouds, and therefore with their attendant hazards, including cloud-to-ground lightning strikes, extreme darkness as the cloud nullifies solar radiation, ember showers, and winds.^[10]

In Australia[edit]

In Australia, following the 2012 scientific confirmation of the 2003 tornado, the Australian Capital Territory Emergency Services Agency (ACT ESA) intended to raise the issue of fire tornado impacts with the Standards Australia Wind Loadings Committee and the Australian Buildings Code Board, since building codes there specified structural engineering requirements for cyclonic winds, but not tornadoes.^[11]

In the United States[edit]

The Carr Fire tornado killed a firefighter, collapsed electrical power transmission towers, and caused other damage on the outskirts of a metropolitan area. [Scientific papers argue they pose a hazard?]

https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=774718

The Carr Fire tornado was estimated to have a peak gas temperature of 2,700 degrees F.

Forecasting, detection, and warning[edit]

Fire tornadoes can be detected in much the same manner as regular tornadoes, including the use of Doppler weather radar systems to detect rotation aloft.

In the United States, where most of the confirmed examples of fire tornadoes have occurred, several of them have been surveyed by National Weather Service meteorologists and their resulting damage given ratings on the Enhanced Fujita scale, as occurs in a typical tornado damage survey—the first being the Carr Fire tornado.^[12]^[13]^[14]^[15] However, the National Weather Service does not yet have a unified standard for warning of fire tornadoes: as of 2020, the NWS had not issued specific policy guidance to its 122 forecast offices on how to handle them. This has led to forecasting decisions being made on a case-by-case basis by the agency's constituent Weather Forecast Offices (WFOs), with some offices concluding internally that they will not issue tornado warnings for fire tornadoes: one meteorologist with the National Weather Service office in Hanford noted that "We need to get the science down before we start building policy about when we alert the public about such things. We don’t want to overburden emergency services or the public with limited science."^[12]

During the Loyalton Fire, staff at the National Weather Service office in Reno identified rotation within the plume and chose to issue a modified tornado warning for a possible "fire-induced tornado", the first warning of its kind. Staff there had the advantage of a favorable location for radar detection and had had prior conversations about what to do in a possible fire tornado scenario, based on the experience of an incident meteorologist who had previously been assigned to the Carr Fire.^[16]^[17] Several weeks later, during the Creek Fire, the NWS office in Hanford considered but ultimately chose not to issue a tornado warning for that incident. A warning coordination meteorologist there said the decision was made because they feared making people conflicted about whether to shelter or to evacuate.^[12]

Tornado warning issued by the National Weather Service in Reno, NV, for the Loyalton Fire

000
WFUS55 KREV 152135
TORREV
CAC035-152230-
/O.NEW.KREV.TO.W.0001.200815T2135Z-200815T2230Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Reno NV
235 PM PDT Sat Aug 15 2020

The National Weather Service in Reno has issued a

* Tornado Warning for...
  Southeastern Lassen County in northern California...

* Until 330 PM PDT.
* At 228 PM PDT, a pyrocumulonimbus from the Loyalton Wildfire is
  capable of producing a fire induced tornado and outflow winds in
  excess of 60 mph was located south of Chilcoot, and is nearly
  stationary.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...Extreme fire behavior with strong outflow winds capable
           of downing trees and starting new fires. This is and
           extremely dangerous situation for fire fighters.

* This tornadic pyrocumulonimbus will remain over mainly rural areas
  of southeastern Lassen County in the vicinity of the fire.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

&&

LAT...LON 3975 12012 3972 12007 3970 12014 3971 12015
      3973 12015
TIME...MOT...LOC 2128Z 240DEG 0KT 3972 12013

TORNADO...RADAR INDICATED
HAIL...<.75IN

$$

WH

List of confirmed fire tornadoes[edit]

The following are confirmed examples of fire tornadoes.


Fire	Date	Location	Max wind speed/rating	Path length	Max width	Summary
McIntyres Hut Fire	1/18/2003	Canberra, Australian Capital Territory, Australia	EF2	12 mi (20 km)	490 yd (450 m)	The Canberra vortex was the first reliably recorded phenomenon to be described as a genuine fire tornado. During the tornado a fire tanker's trailer was lifted off the ground, and a police car was stripped of its beacons and other attachments and lofted into a storm drain. It also damaged the roofs of houses and snapped softwood pine trees several meters above the ground.^[18]
Carr Fire	7/26/2018	Redding, California, United States	EF3 >143 mph	3,300 ft (0.63 mi; 1.0 km)	333 yd (304 m)	One of the strongest known fire-generated tornadoes, the vortex produced by the Carr Fire collapsed steel power transmission towers, uprooted and stripped the bark from large oak trees, damaged roofs, lofted vehicles and a metal shipping container, and produced ground scouring. Videos taken by bystanders and fire crews showed the tornado, which killed a firefighter after flipping his vehicle multiple times.^[13]^[9]^[19]
Loyalton Fire	8/15/2020	Loyalton, California, United States	EF1	0.43 mi (0.69 km)	137 yd (125 m)	The Loyalton Fire generated a large pyrocumulonimbus cloud, which developed a mesoanticyclone and eventually three anticyclonic tornadoes. Bystanders along California State Route 70 and U.S. Route 395 observed and filmed the tornadoes, capturing footage. The first tornado snapped and uprooted multiple several Jeffrey pine trees in Roberts Canyon, causing no property damage, injuries or fatalities.^[20]
			EF1	0.09 mi (0.14 km)	20 yd (18 m)	The second tornado snapped several quaking aspen trees in its short path along the northeast facing slope of Roberts Canyon. The tornado caused no property damage, injuries, or fatalities.^[21]
			EFU	3.16 mi (5.09 km)	156 yd (143 m)	The third tornado produced by the Loyalton Fire traveled more than three miles (4.8 km), but produced no damage that the National Weather Service could identify among burned sagebrush.^[22]
Creek Fire	9/5/2020	Mammoth Pool Reservoir, California, United States	EF2 115-25 mph	12.02 mi (19.34 km)	50 yd (46 m)	The Creek Fire produced two tornadoes. The first was rated EF2 by a National Weather Service incident meteorologist: it snapped multiple trees two feet (0.61 m) in diameter 20 to 30 feet above the ground, debarking them and removing branches. The damage occurred just north of Mammoth Pool, inside Wagner Campground and near Chawanakee Joint Elementary School.^[14]^[12]
Creek Fire	9/5/2020	Bass Lake, California, United States	EF1 90-107 mph	1.12 mi (1.80 km)	25 yd (23 m)	The second tornado produced by the Creek Fire, rated EF1, was described by the surveying incident meteorologist as short-lived but strong. The tornado snapped live trees 15 inches (380 mm) in diameter and uprooted others, leaving their root balls completely exposed.^[15]^[23]^[12]
Bootleg Fire	7/18/2021	Fremont–Winema National Forest, Oregon, United States	EF?	^{[to be determined]}	^{[to be determined]}	The National Weather Service confirmed that the Bootleg Fire produced a tornado. The tornado caused extensive tree damage and scoured roads and soil. While not officially rated, a professor of atmospheric science at the University of Nevada, Reno, characterized the vortex's strength as "akin to an EF2-type tornado".^[24]
Downton Lake Fire	8/18/2023	Gun Lake, British Columbia, Canada	EF0	^{[to be determined]}	^{[to be determined]}	A wildfire-generated tornado developed near the north shore of Gun Lake, at its northeast end near Gold Bridge, at approximately 4:45 a.m. PDT (1145 UTC). The tornado was captured on video and was later confirmed by researchers. Possible snapped and uprooted trees were noted in the area.^[25]^[26]Cite error: The opening `<ref>` tag is malformed or has a bad name (see the help page).^[27]