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Remember how that last post had a (1) after the title? Tada, it’s a two-part post on the weather behind/related to wildfires!

Last time, I talked about peculiar weather conditions to Southern California that helps drive wildfires. But this weather is indigenous to the region. It’s weather that’s related to the wildfire, but not directly caused by the wildfire. Yes. Fires can cause weather.

You see, when wildfires get big enough, they start creating their own weather systems that end up helping them spread. It’s really interesting. They’re called firestorms.

A firestorm happens when a wildfire gets so big and hot, it heats the air directly above it (besides just consuming it for its own purposes). Hot air rises, so all that air tries to escape upward. But now, there’s this empty space and we can’t have a space of no air (well, physics does actually allow for that to happen, but it would be a VERY. RARE. occurrence indeed), so surrounding cooler air enters the area.

This, of course, happens with any fire. However, they generally don’t create any appreciative results. But with very large fires, VERY large fires, this creates enough of a flow of air into the region of the fire, which provides it more oxygen, and if there’s still fuel to be burned, it creates a bigger and hotter fire. And the fire continues to rage out of control.

You would think this would only cause the fires to flare upwards. But no. The are is really turbulent in the area around the fire and that causes the gusts coming in to be erratic, thus spreading the fire. The winds can settle down into a circular pattern and produce a tornado, or at least a mesocyclone.

Another reason why a firestorm spreads fire is because the high oxygen levels produce a hotter fire. The heat can be so great so as to set other things on fire ahead of the fire itself. If it doesn’t ignite anything, well all that heated air does help with the turbulence and then you have that wind thing going on again.

Other weather elements a firestorm can cause are pyrocumulus clouds. These are the dense, puffy looking clouds you see over volcanoes sometimes. It’s due to the heated air again rising up. But this time the hot air rises high enough to hit moisture in the atmosphere again where it can rapidly cool and condense into a cloud…around all that ash and soot that’s mixed in with the air. Rain from one of these clouds is interesting. I wouldn’t recommend letting it fall on your tongue.

As for that rain, it can help put out the fire. Unless the fire was really big to begin with and continues to heat all this air to make a gianter cloud which can then produce lightning that can start another fire.

Firestorms (and the weather it generates). Interesting stuff.


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