Around 12:40 p.m. on July 12, a wildfire east of Moab, Utah intensified, burning hotter, higher and faster than before and running six miles in five hours. Flames reached 250 to 300 feet and crews were ordered to move farther away to safety. The fire and its inky black smoke column began to rotate, forming a pyro-vortex. Two conditions enabled the vortex: an especially hot fire and a source of spin. Gusts off the La Sal Mountains created wake eddies that provided that spin. The vortex sucked debris, produced EF2-level winds (111–135 mph) and can cause severe damage; such events are rare and poorly documented.
The crews were spread out around the blaze, trying to box it in; it had been intense, running six miles in its first five hours. The weather had been hot and windy, sure, but this voracious fire behavior was new. The sky glowed a deep red as the flames grew to 250 to 300 feet. Leaders began radioing their crews, telling them to move farther away to safety.
And then, the fire and its inky black smoke column began to rotate. A wildfire rarely creates its own tornado, or pyro-vortex. (Fire whirls, a fire tornado's little brother, are more common and are smaller, briefer and less intense.) Two key ingredients must first be present: an especially hot fire, and something to set it spinning.
Gusts coming off the flanks of the La Sal Mountains provided the spin for the Deer Creek Fire's tornado. Here, wind flows over the mountains like a river flowing over rocks. The mountains disrupt the wind much like a rock disturbs a river, creating an eddy of swirling water - or, in this case, air.
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