We’ve all heard of tornadoes, dust devils, and even water spouts — but “Fire-nado” is a relatively new term. A fire-nado is a rare weather phenomenon that can simply be described as a fire tornado.
In essence, fire-nadoes can form under certain weather conditions (depending on air temperature and currents) that acquire a vertical vorticity (or spin) and forms a whirl — or a tornado-like vertically oriented rotating column of air. Fire-nadoes or fire whirls may be whirlwinds separated from the flames, either within the burn area or outside it, or it can be a vortex of flame, itself.
One of the most recent incidents occurred just a few days ago where an Australian filmmaker was in the right place at the right time to shoot this incredible 90-foot-tall fire tornado. He says it sounded like a fighter jet, despite there being no wind in the Alice Springs area.
An extreme example is the 1923 Great Kanto earthquake in Japan which ignited a large city-sized firestorm and produced a gigantic fire whirl that killed 38,000 in 15 minutes in the region of Tokyo. Another example is the numerous large fire whirls (some tornadic) that developed after lightning struck a Californian oil storage facility in 1926 — several of which produced significant structural damage well away from the fire, killing two. Thousands of whirlwinds were produced by the four-day-long firestorm coincident with conditions that produced severe thunderstorms, in which the larger fire whirls carried debris 5km away.
According to NOAA (the National Oceanic Administrative Association), “While rare, fire tornadoes (also known as fire whirls) generally form when superheated air near the surface of a large fire zone rises rapidly in an airmass where sufficient horizontal or vertical vorticity (spin in the atmosphere) is also present. Much like a dust devil or whirlwind, the rapidly rising air above a wildfire can accelerate and turn the local vorticity into a tight vertical vortex, now composed of fire instead of dust.”