Fire Tornadoes

Tornadoes are quite possibly the single most terrifying weather event. While not responsible for nearly as much damage as hurricanes, flash floods, or a variety of other events, their sheer monolithic force is much more concrete than larger, more dispersed phenomena. There is one variant, however, whose name seems like it should be far, far more intimidating of a phenomena- the fire tornado. In reality, however, fire whirls aren't nearly as much of a concern as they would seem.

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First off, fire tornadoes aren't actually tornadoes, strictly speaking. They're more properly referred to as fire whirls. They're generated from the high heat of fires, as opposed to tornadoes, which are generated by atmospheric phenomena known as mesocyclones, which stretch from the ground to the clouds. Small fire whirls, though they can reach extreme levels of heat (as much as 2000 degrees Fahrenheit (1090 degrees Celsius), are seldom particularly intimidating- the overwhelming majority are only a few inches tall.

There are, of course, larger and more intimidating fire whirls- if they never got bigger than a few inches then they would have never earned the nickname of fire tornadoes. Larger fire whirls average between 10 and 50 meters tall, are a few meters wide, only last a few minutes. Significantly larger ones have been known to grow up to a kilometer in height, however, and contain winds going over 160 km/h. (Still considerably less than half of speeds recorded inside tornadoes.) They've been known to uproot 50 foot tall trees as well.

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There have been a few isolated examples of truly devastating fire whirls, however. In 2003, severe brushfires in Australia spawned an F3 tornado in Canberra. This is the only confirmed actual tornado (not fire whirl) to be spawned by a wildfire. The 1923 Great Kanto Earthquake ignited a city-sized firestorm in Tokyo. Many of the deaths were caused by an immense fire whirl that hit a massively overpacked emergency shelter, killing 38,000 people inside. No tornado has ever killed more than 1300 people.

It seems pretty audacious claiming that a phenomena that killed 38,000 people in one go is a less dangerous threat than a tornado. Here's the thing, though- the deaths are the result of massively overpacking people in an emergency shelter that couldn't adequately shelter them. Even if the fire whirl hadn't occurred, they would have probably still died from just the fire- and therein lies the rub. Fire tornadoes are the result of a destructive event themselves- if you're able to evade the original fire, you'll likely be able to evade the fire tornado as well.

A pyroclastic flow, followed by the subsequent generation of pyroclastic tornadoes. Note that the video is sped up at 2x normal speed. [Original video]

As a great example of this, pyroclastic eruptions from volcanoes are capable of generating a similar phenomena, but fueled by superheated volcanic ash instead of fire. They get much larger in size than the average fire whirl, but there are no records of anyone ever dying in one, simply due to the fact that anyone who might have been in range of them will already have died to the pyroclastic flow. Pyroclastic flows and firestorms are worth worrying about- worrying about fire whirls is like worrying about getting sick when you're on a plane about to crash.

On top of that, fire whirls are much, much rarer and shorter lived than actual tornadoes, so the frequency with which they are encountered by humans is imply a lot lower. Of course, our psychology is fundamentally biased to be more worried over rare events than common ones. Car crashes hardly worry us, despite how extremely common they are, while lots of people fear shark attacks or plane crashes, despite both being extraordinarily rare and improbable events.

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Bibliography:

• Door to Door, by Edward Humes
• https://en.wikipedia.org/wiki/Fire_whirl
• https://en.wikipedia.org/wiki/Mesocyclone#Tornado_formation
• https://en.wikipedia.org/wiki/1923_Great_Kant%C5%8D_earthquake#Damage_and_deaths
• https://en.wikipedia.org/wiki/Tornado
• https://en.wikipedia.org/wiki/2003_Canberra_bushfires#Canberra_Fire_Tornado
• https://www.livescience.com/45676-what-is-a-firenado.html
• https://news.nationalgeographic.com/2017/01/fire-tornado-video-western-australia-fire-whirl/
• https://www.smh.com.au/environment/researchers-confirm-first-fire-tornado-during-2003-bushfires-20121119-29liv.html