How destructive wildfires create their own weather

By Amanda Schmidt, AccuWeather staff writer

Wildfires have the potential to devastate thousands of acres of land, wreaking havoc on anything in their path.

They also have the potential to create their own weather.

This makes wildfires widely unpredictable and dangerous for firefighters working to control the flames.

'firenado' CA wildfire 2006

Flames spiral upward in mini-tornadoes on a ridge as the Sawtooth Complex fire moves through Big Morongo Canyon, Thursday, July 13, 2006, in Morongo Valley, Calif. (AP Photo/Reed Saxon)

Wildfires that create their own weather usually do so under conditions for “extreme fire behavior,” according to AccuWeather Meteorologist Evan Duffey.

Dry air and hot weather at the surface are key for extreme fire behavior.

The hot air at the surface raises the temperature of vegetation, making it more likely to quickly ignite. This helps the fire spread faster.

Hot air at the surface also creates atmospheric instability, similar to conditions that help thunderstorms to develop, Duffey said.

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“The fire gives air a push up above it, and then once it is moving up, the atmospheric instability accelerates it upwards, just like a building thunderstorm,” Duffey said.

Wildfires can create their own thunderstorms, according to AccuWeather Meteorologist Jordan Root.

“The hot air generated by a wildfire will rise and create an updraft. As the air rises, moisture will cool and condense into tiny water droplets on the ash creating a cloud,” Root said.

Clouds created by wildfire are called pyrocumulus, which means "fire cloud."

If the fire is big enough it will create pyrocumulonimbus, which means "fire storm cloud."

“While they can bring rain which can help in fighting the fire, they also can bring dry lightning which can start new fires,” Root said.

Storms created by fires can also generate stronger winds, which fan the fire and make it hotter, which can cause the fire to spread, according to NOAA SciJinks.

Wildfires also create their own wind patterns.

Air that is warmer than its surroundings will rise because it is less dense. In the case of wildfires, the air is much warmer, so it rises rapidly.

The rapidly rising air creates a vacuum at the surface near the fire, so air from around the fire gets rapidly pulled in to fill the void, according to Duffey.

This is how fires create their own wind.

firestorm graphic

Firenadoes and whirls are created when this incoming wind meets and clashes.

The swirling winds of firenadoes carry embers and ash that get caught in the violently rising air. As the air is rapidly pulled up, it causes the swirling air to spin faster, causing a fire whirl, according to Root.

Firenadoes within the Carr Fire were captured in videos, which demonstrates the intensity of that fire.

“When wildfires are intense, air tends to move much more violently, producing strong gusts, which creates a chaotic and dangerous environment for firefighters,” Root said.

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