The term “fire tornado” describes a rare and dangerous atmospheric phenomenon technically known as a fire whirl or fire vortex. These events are columns of spinning air and flame that rise from an intense fire. While most fire whirls are small and short-lived, the largest can escalate to the power of a meteorological tornado. Understanding their formation and behavior is important for safety near any large blaze.
How Fire Whirls and Fire Tornadoes Form
A fire vortex begins when an intense fire superheats the air immediately above the ground. This hot, less-dense air rapidly rises, creating a powerful vertical column of air known as an updraft, similar to a chimney effect. If this updraft interacts with wind patterns that introduce a horizontal spin, the column can begin to rotate around a vertical axis. This rotation then tightens, much like a figure skater pulling in their arms, causing the spinning column to accelerate and intensify.
Smaller fire whirls are only tens of feet wide and last for mere minutes. These smaller whirls are driven by local thermal gradients and wind shear near the ground. However, under extreme conditions, such as during a massive wildfire, the heat can become so intense that it generates a pyrocumulonimbus cloud (pyroCb) high in the atmosphere. This massive, thunderstorm-like cloud structure introduces atmospheric instability and vorticity, allowing the fire vortex to grow into a true, destructive fire tornado.
The Specific Dangers of Fire Vortices
The danger posed by a fire vortex is twofold, combining the extreme thermal threat of fire with the mechanical devastation of high-speed winds. The core of a fire whirl can reach temperatures exceeding 2,000°F (1,093°C), with some recorded temperatures reaching as high as 2,700°F. This intense heat is capable of causing instantaneous combustion and melting many materials.
Simultaneously, the rotational winds within the vortex can become violently strong. While many fire whirls have wind speeds in the range of 40 to 100 miles per hour, rare, true fire tornadoes have been documented with speeds up to 143 mph, classifying them as an EF-3 on the Enhanced Fujita Scale. These tornado-force winds can uproot large trees, flip vehicles, and tear structures apart. A fire vortex can also loft burning embers and debris high into the air, a process called “spotting,” which spreads the fire rapidly and unpredictably far beyond the main fire line.
Response and Safety Near Wildfires
Because fire vortices are unpredictable, the primary safety measure is strict adherence to official evacuation orders in wildfire zones. Fire services utilize atmospheric monitoring and weather models to predict conditions conducive to the formation of these extreme phenomena. Meteorologists look for a combination of intense surface heat, strong updrafts, and existing wind shear to forecast when a large vortex is possible.
For anyone near a wildfire, identifying signs of rapidly escalating fire behavior is important, as large vortices can form quickly. Look for a sudden, rapid growth of the smoke column or noticeable changes in wind direction and intensity. If a fire vortex is spotted, the recommended action is to move away from it immediately, as it can change direction without warning. Due to the risk of spotting, new fires can ignite hundreds of feet away from the spinning column, so remaining vigilant for flying embers and new ignitions is necessary.