The Firestorm This Time: Why Los Angeles Is Burning (wired.com)

The Thomas Fire spread through the hills above Ventura, in the northern greater Los Angeles megalopolis, with the speed of a hurricane. Driven by 50 mph Santa Ana winds -- bone-dry katabatic air moving at freeway speeds out of the Mojave desert -- the fire transformed overnight from a 5,000-acre burn in a charming chaparral-lined canyon to an inferno the size of Orlando, Florida, that only stopped spreading because it reached the Pacific. Several readers have shared a Wired report: Tens of thousands of people evacuated their homes in Ventura; 150 buildings burned and thousands more along the hillside and into downtown are threatened. That isn't the only part of Southern California on fire. The hills above Valencia, where Interstate 5 drops down out of the hills into the city, are burning. Same for a hillside of the San Gabriel Mountains, overlooking the San Fernando Valley. And the same, too, near the Mount Wilson Observatory, and on a hillside overlooking Interstate 405 -- the flames in view of the Getty Center and destroying homes in the rich-people neighborhoods of Bel-Air and Holmby Hills. And it's all horribly normal. [...] Before humans, wildfires happened maybe once or twice a century, long enough for fire-adapted plant species like chapparal to build up a bank of seeds that could come back after a burn. Now, with fires more frequent, native plants can't keep up. Exotic weeds take root. Fires don't burn like this in Northern California. That's one of the things that makes the island on the land an island. Most wildfires in the Sierra Nevadas and northern boreal forests are slower, smaller, and more easily put out, relative to the south. Trees buffer the wind and burn less easily than undergrowth. Keeley says northern mountains and forests are "flammability-limited ecosystems," where fires only get big if the climate allows it -- higher temperatures and dryer conditions providing more fuel. Climate change makes fires there more frequent and more severe.

Comments

Here come those Santa Ana winds again

[rmdingler]

There are ideal conditions for wildfires in this region (and others) nearly every year. What's special about this year?

"What we don’t have every single year is an ignition during a wind event. And we’ve had several."

Whether by foolish acts or (pyro)maniacal disposition, people are the blight on this land.

Dontcha need wetter for more fuel?

[xxxJonBoyxxx]

>> higher temperatures and dryer conditions providing more fuel

I thought you needed WETTER conditions to get more fuel. Is anyone surprised that there are a bunch of large fires after California's water supply returned to normal and plants had a chance to grow back? (It was as green along Hwy 1 as I've ever seen it this year.) That stuff dries out...and then burns - science, yo.

http://www.mercurynews.com/2017/10/03/will-this-winter-in-california-be-wet-or-dry/

Re:Dontcha need wetter for more fuel?

[dfm3]

TFA does a better job than the summary at explaining, but yes, your observation is consistent. Wetter summers mean more vegetation growth, but it's the weather during a few critical weeks in late fall that determine how severe the fires will be.

It's the small stuff (leaves, brush, and weeds) that burns fast, hot, and explosively given the right conditions. In the fall, when the deciduous species lose their leaves, a wet December means that most of this vegetation falls to the ground and begins to decompose, rendering it more dense and less flammable. When you have a combination of dry weather, warm temperatures, and high wind, combined with ignition (historically caused by lightning, but usually by people these days), leaves tend to stay on the trees longer, or fall to the ground without decomposing, and become perfect fuel.

So yes, you're correct that when this stuff dries out, it becomes a hazard.

For example, last fall was a historically notable fire season in the southern Appalachians. Many parts of the mountains in NC/TN/GA had little to no measurable rainfall for a couple months, so the leaves simply dried up and stayed on the trees rather than changing color and falling to the ground. The deadly fires that swept through Gatlinburg, Tennessee became "canopy" fires - an event more common in California but virtually unheard of in eastern forests. Even one good rainstorm could, in theory, have been sufficient to knock enough leaves off of the trees and compress the leaf litter on the forest floor to render it slightly less flammable.

Re:The priesthood has spoken

[Opportunist]

I have no sockpuppets, I'm actually happy I got an answer for a change. Thank you.

The arguments sound valid so far, I'll have to look into it.

Re:Lot of people moved there for the warm weather

[liquid_schwartz]

Hope they're enjoying their warm weather. You have to take the good with the bad. Didn't the U.S. steal it from the Indians or Mexicans anyways? Bad karma?

Best thing that ever happen to the land if you've ever seen Mexico. If we could go back in time we should have just absorbed Mexico. We'd have a smaller border to defend and the Mexicans would already be integrated and English speaking. It would save everyone a lot of trouble in the long run.

Re:The priesthood has spoken

[bobbied]

Also, don't forget that humans have been putting out fires in these areas for decades. Fire is a natural part of this ecosystem and we put them out and restrict land management practices that would have reduced the available fuel in these areas currently burning. In that way we HAVE made these particular fires worse. So, I don't think we can lay the whole blame here on Global Warming... Even if it fits the accepted narrative... Some blame? Maybe a very small part of the hot/dry weather, but this is hardly provable. LA is a hot dry and windy place this time of year and always has been in our recorded history.

Same Thing as Every California Wildfire

[eepok]

Every big stretch of wildfires are caused by the same thing:

1. High winds
2. Low humidity
3. Unmanaged brush
4. Either a lightning storm or (more likely) some human doing something stupid (camp/bonfire, trash burning, arson, cigarette, etc.)

This year was particularly bad for both Northern and Southern California because this past winter's rain was so significant that it almost completely erased the multi-year drought. That means lots and lots of greenery growing in the spring and waiting to burn throughout the summer and fall.

Re:The priesthood has spoken

[judoguy]

When the population increases in an area, people are always driven to build more housing on the bad land. It's no surprise when 'expensive new housing' is flooded or beset upon by a hurricane. The 'bad land' is the places where there aren't already 100 year old structures.

Upvote, upvote, upvote.

I grew up going to NC outer banks for holidays. The Styrofoam stucco houses on the beach regularly get devastated while some of the first structures built are still there. People in the 1600's and 1700's knew about the ocean and weather and built as high up as possible and as far from the beach as feasible.

Re:True

[Gravis Zero]

There were never wildfires before climate change was discovered.

The is real problem is that we're been putting out the wildfires for over a hundred years when burning is part of the natural cycle of life for the ecosystem. As a result there are many millions of dead and dry trees just waiting for a spark. However, climate change is exacerbating the issue by causing more extreme weather (longer droughts and more extreme downpours) which ultimately kill more plants and turn them into fuel for the fire. Climate change definitely isn't the cause of these giant wildfires but it is making it worse.