Extraordinary weather phenomenon: the fire tornado

A gigantic whirlwind of flames that wrap around each other: this phenomenon, often depicted in hollywood movie disasters, actually exists. The tornadoes of fire are even quite common in fires, whether forest fires, brush fires and even fires in human facilities, such as factories or gas stations. The “firenado”, a contraction of fire (fire) and tornado (tornado) is similar to Dust Devils, these famous dust devils that regularly form in the desert regions of the USA and the Sahara, sometimes also in the south of France. We are used to calling them “fire tornadoes” even though they are not, strictly speaking, fire tornadoes. tornadoes (because a tornado forms under a thunderstorm), but rather whirlwinds.

Classic dust devils form most commonly in dry, sandy regions:air unstable rotates and lifts dust or sand from the ground. Their formation depends on the warming of the soil and the turbulence currents: fire generates its own winds. In the event of a fire, the air near the ground is obviously overheated. These whirlwinds therefore tend to form easily in this context: fire tornadoes are in fact dust devils who encounter fires, and take their source fromenergy in the heat intense air near the blaze. Some whirlwinds come in the form of smoke tornadoes near fires, while others directly encounter the flames and become real fire tornadoes.

Up to 2,000°C inside the tourbillon

Some whirlwinds of smoke and fire can also reach several hundred meters in height with a temperature of 1,500 to 2,000 ° C inside. The most impressive were filmed during the great california fires and D’Australia in recent years, especially in softwood forests. Some rangers have even reported seeing fire tornadoes reaching 1 to 4 kilometers in height!

Fire tornadoes can therefore stretch for tens of meters, or take the form of a tiny whirlpool of less than a meter. The larger the whirlpool, the more dangerous it is, as it is capable of sending flaming debris hundreds of meters away, and in all directions, as it spins at great speed. speed. This flaming debris is in turn capable of triggering other fires.

These fire tornadoes are often very short-lived, a few seconds to a few minutes, but it has happened that some last 20 minutes. Like dust devils and real thunderstorm tornadoes, they can travel a few hundred meters or more. It also happens that several fire tornadoes form at the same time, giving rise to a truly apocalyptic-looking scene that has nothing to envy to the movie theater.