The heat inside a large fire causes air to rise, forming eddies that can spiral into a vortex called a fire whirl. A fire tornado is essentially a much larger whirl. Those rising eddies become strong updrafts, much like the updrafts that form during thunderstorms. In normal storms, the moisture flung into the air from these updrafts form cumulonimbus clouds—when it happens in a fire, they’re called pyrocumulonimbus clouds. But these updrafts alone don’t cause a tornado. It’s when the surrounding winds are changing direction rapidly that the updrafts can start to get redirected into a spiral, which becomes a vortex, which can eventually strengthen into a full tornado. This weekend’s Loyalton Fire seems to have produced at least five tornado-strength vortices, which flung smoke up 30,000 feet into the air.
