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Some have e-mailed LAist asking about the huge white cloud over the fire. "Why is the smoke cloud white during the day?" one reader asked.
It is a pyrocumulous cloud, or fire cloud, "that is created from very intense heat at the surface, usually from wildfires," explained Gary Robbins, resident Sciencedude at the Orange County Register. "The lower part of the cloud is gray, and the upper reaches are white — a normal shading, says the National Weather Service. The clouds are about 15,000-feet high."
The Weather Notebook, a nationally syndicated radio show, describes a lot of what we've been hearing about, such as the fire creating its own wind patterns, and a new concern brought up today--lightning:
What happens is when you get these large fires you're getting quite a bit of trees and brush. Obviously, that's moisture being released from the trees. Also a lot of heat. So that in turn you have this big mass of warm ascending moist air-- it sounds like a big thunder storm in the mid west. That's exactly what these smoke columns are. They act very much like thunderstorms. So you start developing these large smoke columns, and then as the moisture starts to condense out you start developing this pyrocumulous cloud this thing will grow and will eventually evolve into the thunderstorm phase… and from there it will start being effected by high winds aloft just like regular thunderstorms are and you'll get lightning and rain, all those types of things you see with a typical thunderstorm.Lightning from pyrocumulous clouds can actually start other fires downwind from the original source. At the same time, rain from pyrocumulous clouds can sometimes put fires out. The biggest concern for firefighters when these conditions develop is wind. Downdrafts created by the thunderstorm conditions can cause fires to suddenly switch directions, and can even causes powerful tornados of fire.
LAist Featured Photos Contributor STERLINGDAVISPHOTO submitted this short time-lapse video (below). It looks like waves at the beach.
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Dallas Raines explained last night as the heated air rises it creates the cloud and as it cools the dome collapses (as shown in the video) until the surface air reheats and creates it again.
It's pretty incredible stuff, albeit a bit terrifying as well.
I would modify that explanation just a bit. LA has it's typical coastal inversion layer -- the higher air is hotter rather than cooler as is typical in most regions.
The fire creates its own thermals and breaks the inversion "cap" which allows massive convection columns to rise up through the temperature gradient (typically, it is mountains that do that, which is why they get the big cumulo-nimbus clouds and massive thunderstorms in hot, dry weather).
That's also why the clouds looks so white up above the smoke created by the Station Fire, it's pulling all the area's moisture along with the smoke to above the inversion, making our relative humidity drop even lower. Plus, the fire is burning so hotly that there is complete combustion and less black smoke.
That is one ex-firefighter's opinion.
Thanks STERLINGDAVISPHOTO for that incredible time-lapse video. Kinda reminded me of an electric desktop wave machine that rocks slowly back and forth generating a contained liquid wave.
here is another time-lapse of the recent fires:
http://www.brandonriza.com/Video/HTML/ZeroPercentContained.html