Answer:
Most likely "fire tornadoes" form by a mechanism similar to dust devils. The hot air produced by a fire creates and updraft and more air must move in to replace it. Interaction with vegetation, buildings, local topography, and the wind can sometimes give this in-rushing air a spin.
First answer by Stormish. Last edit by Stormish. Contributor trust: 533 [recommend contributor recommended]. Question popularity: 2 [recommend question].