Skip navigation

Monthly Archives: May 2013

Fire, fire, fire, fire! (2)

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.

Fire, fire, fire, fire! (1)

Let’s talk about fires.  In particular, wildfires.  In case you’re wondering, a wildfire was partially the reason as to why I didn’t post on Friday (I was in the midst of preparing a filler when I got distracted).

So, what is a wildfire?

wildfire (noun) \-ˌfī(-ə)r\

: a sweeping and destructive conflagration especially in a wilderness or a rural area

If you’ve been following state news, you’ll know that there were a few fires in Southern California recently.  Here’s a map.  The biggest one so far as been the Springs Fire, which started in Camarillo Springs and spread into Newbury Park.

Why does the Springs Fire matter?  Because Clib (and Clia) are located in the Newbury Park area of Thousand Oaks.  And because when I’m working out there, I like to stay in Camarillo.  So, the Springs Fire was kind of relevant to me this past week.  See?

fires

The photo on the left was taken on Thursday around 19:00.  The photo on the right was taken in the same general area (I think I shifted left a bit) on Friday around 15:00.

At the closest, the fire perimeter was a bit more than half a mile from us.  But since we were northeast of the fire and the winds were blowing mostly southwest, we weren’t evacuated.  But it was bad enough on Friday that it was raining ash and soot on us.  It made for a difficult time breathing.  Oh, and I got to drive through the beginnings of it on Thursday going to work.

Wildfires are interesting to me.  Or actually, the weather involved with wildfires is interesting to me.  The Springs Fire was able to grow to 30,000ish acres in a large part because of the Santa Ana winds.  The Santa Ana winds are a strong, very dry katabatic wind that blows from the high desert to the coast.  While they can be a cold wind, they’re generally known to be hot winds.

The Santa Anas happen when the air over the Mohave Desert cools and descends rapidly.  As that chunk of air descends, it generally will heat up from compression and dries out.  The air was actually already quite dry when it got shoved over the high desert, but descending and blowing across the desert dries it out even more.  Now all that air has go somewhere.  So it goes whistling through the mountain passes toward the coast.

The problem with this is that a lot of the area the wind blows through is chaparral.  If the winds are hot and dry, they have a tendency to pick up any stray ember or spark and turn it into a wildfire.  Hence, the Springs Fire.  Or any number of other fires in Southern California’s history.

In this case, there hadn’t been a major fire in this area for over 20 years.  That means there was a lot of brush and undergrowth available to fuel the fire.  The Santa Anas were particularly hot and gusty this time.  Relative humidity had dropped into the single digits.  These are all very good conditions for a wildfire.  And we got one.  And it was made worse because after it had reached the coast, a coastal wind started blowing inland.  That caused the fire to double back on itself and burn areas that it hadn’t burned on its journey to the coast.  It’s a pretty sizable area that’s been burned.

So.  Wildfires.  And weather.  Interesting stuff.

And in case you’re wondering, the title of the post comes from the time when I was trying to remember the witches’ lines in Macbeth (you know the one: “Double, double toil and trouble; / Fire burn, and cauldron bubble”) and somehow my brain got stuck and I ended up with “Fire, fire, fire, fire!”  I…don’t know what happened either.