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Consuming as many as 15 homes, it seemed the rapidly moving Rockport 5 Fire that forced evacuations in Summit County Tuesday couldn't get any worse. Then people started seeing something else: giant funnel clouds of fire and smoke rising out from the depths of the flames.

They're called fire whirls, and they're a sign that the fire is taking control.

The whirls happen when extreme heat meets high winds within a very healthy wildfire. The two forces combine to form small whirls that consume smoke and even flames, according to Monica Traphagan of the National Weather Service in Salt Lake City.

"You're seeing a fire sort of create its own weather," Traphagan said.

Pyrocumulus clouds, large brown clouds formed by smoke that rises high into the atmosphere, are also signs of a raging fire's micro-weather powers.

Of course, that power only applies within the limited influence of the fire itself. Most fire whirls don't have very long life-spans, and they don't travel beyond the boundaries of the fire, Traphagan said.

While they are a sight to behold, fire whirls aren't all that uncommon, she added. In most intense fires, fire whirls and pyrocumulous clouds will form, but they're usually beyond the prying eyes of the public.

So while people don't need to worry about a whirlwind of flames tearing through their neighborhood, a fire whirl sighting can be a sign of bigger problems.

"To us, that's a visual indicator of an unstable atmosphere," said Riley Pilgrim, a firefighter specialist for the Unified Fire Authority's Wildland Bureau.

In Pilgrim's 13 years of fighting wildfires, a fire whirl is also a sign that the fire is gaining the upper hand — and that there's not a whole lot firefighters can do until the atmosphere stabilizes.

"That's a safety concern for firefighters," he said. "We'll do as much as we can, but we also need to be safe."

Twitter: @KimballBennion

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