Fire whirl

Episode #4 of the course “Rare and Unusual Weather Phenomena”

Fire whirls, also known as fire tornadoes or “firenadoes,” are not true tornadoes. Where tornadoes descend from swirls of storm clouds, firenadoes are caused when air currents rise from the heat of burning fires, creating a vortex that lifts burning debris into the air. Fire whirls start fairly small and can be less than one foot in diameter, but when the vortex becomes stronger additional materials cause the whirl to grow into a tornado-like phenomenon that can be as wide as 500 feet (153 meters) across.

The stronger a fire tornado’s vortex grows, the more it creates a column of fire that stretches from earth to sky, resembling a tornado. Although fire tornadoes are a fairly quick phenomenon, lasting only a few minutes, they can wreak immense havoc across a wide area. Because the winds in a fire whirl are moving so quickly, they can spread fires over large distances, and they are known to be powerful enough to lift and move armored vehicles and buildings. When they strike they can cause devastation to communities; the deadliest fire tornado on record appeared in 1871, killing over 1500 people.

Fire tornadoes occur fairly infrequently because they need the right conditions, including hot, dry air heated from the ground. But the fire whirls that have been measured include winds over 100 miles per hour and temperatures as hot as 2000 degrees Fahrenheit (1093 degrees Celsius). Fire whirls are so devastating because the vortex of spinning air speeds up at its center, easily picking up burning materials, gases, and embers.

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