Question Can a tornado be made out of fire?

Answer

Yes, although not all atmospheric scientists or fire experts agree on the exact definition and terminology. True fire tornadoes are rare and are always associated with extreme fire behavior.

Fire Tornado Terminology

Fire tornadoes are rare atmospheric tornado events. They are also referred to as “pyrogenetic tornadoes,” which refers to the way in which they are formed, with a tornado-strength vortex much like a traditional tornado.

People sometimes use terms like “fire whirl,”  “fire devil,” “firenado” or “firestorm” interchangeably.  The terminology can be confusing—and not even the experts always agree on the differences between these phenomena. The following sources take a closer look at the terms:

• The U.S. Forest Service defines the fire whirl as a “spinning vortex column of ascending hot air and gases rising from a fire and carrying aloft smoke, debris, and flame. Fire whirls range in size from less than one foot to more than 500 feet in diameter.” Sometimes, however, a fire whirl occurs that is much larger and stronger than average. More common than fire tornadoes, fire whirls are whirlwinds created by the heat of flames.
• In their paper “Fire Whirls: Twisters that Light the Sky”, Bradley Muller and Christopher Herbster look at the history and science of fire whirls, while discussing some of the differences and shared characteristics of associated terms. They point out that even fire fighters and atmospheric scientists use the term ‘fire tornado‘ in different ways, and that atmospheric scientists may distinguish between intense fire whirls and the more rare fire tornadoes associated with a cumulonimbus or pyrocumulonimbus cloud.(Weatherwise, v.67: 30 Oct. 2014.)
• Firestorm:  The National Oceanic and Atmospheric Administration (NOAA ) gives this definition of a firestorm on their SciJinks site:  “A wildfire–or multiple wildfires in the same area–can cause a firestorm. A firestorm occurs when heat from a wildfire creates its own wind system. This phenomenon can lead to very strange weather effects.” 
• Another description of a fire whirl was given by David W. Goens, in a 1978 NOAA Technical Memorandum (NWS WR-129) in which he describes it as : “a vigorous atmospheric circulation, created when highly unstable, superheated, dry air near the ground breaks through the boundary layer and shoots upward in a swirling motion. “
• For more fire-term definitions, see the  Fire Terminology Glossary posted on the U.S. Forest Service website.

Not all fire whirls are fire tornadoes but today some scientists classify certain extreme events as fire tornadoes.  They are sometimes referred to as  firenadoes—or, in Australia, pyrotornadoes.  Scientists have identified  certain characteristics that go beyond normal fire whirls and are specific to actual fire tornadoes, as happened in the Carr Fire in California. In 2018, Neil P.  Lareau,  a professor and  atmospheric scientist at the University of Nevada, Reno,  discovered that a fire-generated vortex—a massive stream of rising, spinning, smoke, ash and fire—accelerated California’s Carr Fire. He used satellite and radar observations to document the evolution of the vortex, which spun with the power of an EF-3 tornado and rose 17,000 feet above Earth. 

According to  Lareau a fire tornado  “initiates its own weather system helping to concentrate the rotation”.  As smoke rises and condenses in the upper atmosphere,  it forms an ice-topped cloud known as a pyro-cumulonimbus or firestorm cloud over the fire vortex. The development of the cloud stretches the underlying column of air, concentrating the rotation near the surface and causing winds to accelerate to tornado strength. Winds in the Carr Fire were estimated at 143 mph.

Interesting Facts about Fire Whirls and Tornadoes

• They can uproot trees that are 15 m (49 ft.) tall or more.
• In 2018, a fire tornado from the Carr Fire in Redding, CA was reported to have an estimated  speed of 64 m/s  (about 143 mph). 
• Smaller scale fire whirls can appear in bonfires. Even bonfires often have whirls on a smaller scale and tiny fire whirls have been generated by very small fires in laboratories.
• Films of fire tornadoes used to be rare, but they are becoming more common as access to video cameras becomes widespread. 
• Historic fire whirls and fire tornadoes  include: 
  • The Great Peshtigo Fire.
    Oct. 8, 1871,  Wisconsin — A strong cold front fanned prairie fires into a firestorm over Peshtigo, Wisconsin, with winds over 100 mph and fire temperatures between 500 and 700 degrees Fahrenheit.
  • The Great Kanto Earthquake. 
    Sept. 1, 1923, Tokyo, Japan — Following an earthquake and tsunami, a devastating fire tornado  swept through Tokyo.
  • San Luis Obispo Fire. 
     April 7, 1926, California — Lightning striking tanks at a tank farm led to a five-day fire with numerous whirls and at least one tornado. J.E. Hissong wrote about it in the April, 1926 issue of Monthly Weather Review, marking the first scholarly treatment of fire whirls and their formation. Hissong wrote that the fire “produced hundreds of violent whirlwinds, many of tornadic character and force, probably the strangest meteorological phenomenon ever noted in connection with a fire.”
  • Fire bombings of Hamburg and Dresden. 
    Large, deadly whirls also were noted after the  bombings of these cities during World War II.

  

Published: 6/2020. Author: Science Reference Section, Library of Congress