What is a fire tornado?

Published: Jul 28 2011 10:58:03 AM EDT

A fire whirl, fire devil or fire tornado, is a rare phenomenon in which a fire, under certain conditions (depending on air temperature and currents), acquires a vertical vorticity and forms a whirl, or a tornado-like vertically oriented rotating column of air.

Fire tornadoes may be whirlwinds separated from the flames, either within the burn area or outside it and can make fires more dangerous.

Most of the largest fire tornadoes are spawned from wildfires.

They form when a warm updraft and convergence from the wildfire are present.

They are usually 10-50 meters (30-200 ft) tall, a few meters (~10 ft) wide, and last only a few minutes.

However, some can be more than a kilometer (0.6 mile) tall, contain winds over 160 km/h (100 mph), and persist for more than 20 minutes.

Fire whirls can uproot trees up to 15 metres (49 ft) tall.

These can also aid the 'spotting' ability of wildfires to propagate and start new fires.