Pyrocumulonimbus

An analysis of how this tornado formed sees several factors joining forces: the preexisting winds and local topography, a pyrocumulonimbus storm developing, and the addition of hotter-burning fuels as the fire hit groups of houses.

Last Wednesday, though, conditions led to the creation of a larger, taller cloud called a pyrocumulonimbus, which is similar to a thunderhead. It likely reached an altitude of about 45,000 feet, said Neil Lareau, who studies wildfire behavior at the University of Nevada, Reno.