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What Is a Firestorm?

The Short Answer

A wildfire--or multiple wildfires in the same area--can cause a firestorm. A firestorm occurs when heat from a wildfire creates its own wind system. This phenomenon can lead to very strange weather effects.

Seeing Wildfires From Space

Image of a firestorm over a mountain.
Figure-A: Credit: U.S. Forest Service, photo by John Newman

The latest Geostationary Operational Environmental Satellites, called the GOES-R series, have an instrument called the Advanced Baseline Imager (or ABI). The ABI can quickly locate fires, seeing them in more detail than ever before and allowing scientists to monitor changing fires more easily.

Figure-A shows an active flame front of the Zaca Fire in Santa Barbara County, CA. This 2007 blaze was one of the largest fires on record in California. Credit: 

Weather Forged by Fire

How firestorms form: a large arrow pointing up with swirling arrows going upward, heat rises written at the bottom.
Figure-B: Credit: NOAA/JPL-Caltech

Whether they start from a lightning strike, an unattended campfire, or a downed power line, wildfires can be an incredibly destructive force. Some of them grow so large that they can also create their own weather system.

It's true. At times, a wildfire (or multiple wildfires in the same area) causes a firestorm. That means the heat from the fire creates its own wind system, and this can lead to very strange weather effects.

Fire Wind… and Tornadoes

A person in a field with a fire tornado in the background.
Figure-C: A fire tornado. Credit: United States Marine Corps.

Firestorms form for two main reasons:

  • Hot air rises.
  • Nature hates a vacuum (not the loud cleaning appliance, but an empty space). That means empty spaces don’t stay empty for long

It all starts because heat is constantly and quickly rising from the fire. As all this heat and air moves upwards, it leaves behind some empty space. Air from all around the fire rushes in to fill that gap.

That movement of air creates powerful wind called an updraft.

In some cases, the rising air can be so fast it creates a fire whirl, also known as a fire tornado. Seriously. A tornado of fire. As if a wildfire weren't bad enough by itself!

Fire Clouds

A large dark cloud with a plane flying through it.
Figure-D: A pyrocumulus develops above the Oregon Gulch fire in 2014. Credit: Oregon Air National Guard, photo by James Haseltine.

As the smoke from the fire rises, it condenses when it reaches the upper atmosphere. The water comes from moisture already in the atmosphere, as well as the water evaporating from the burned plants, fueling the fire. The cloud that forms is called a pyrocumulus, which means "fire cloud."

If the fire is big enough, it will form a pyrocumulonimbus, or a "fire storm cloud." These can produce lightning, which could set off even more fires. They also generate stronger winds, which fan the fire, making it hotter and helping it spread. No one wants that.

Pyrocumulonimbus clouds in the sky
Figure-E: A pyrocumulonimbus forming in British Columbia, Canada. Credit: NOAAA, photo by Noriyuki Todo.

Fire Clouds With Occasional Silver Linings

But wait! It's not all bad. Although it’s rare, these fire clouds can also produce rain that helps extinguish the fire. When that happens, it's a wonderful thing.

 

This content was produced by the NASA Space Place team at NASA's Jet Propulsion Laboratory for NESDIS with funds from the GOES-R Series program and the JPSS program.