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JPL Scientist Explains Why the Foothill Cities Became 'A Little Pocket of Destruction'

Photo by Andy Kennelly via the LAist Featured Photos pool
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Typically when the notorious Santa Anas blow through Southern California, the cities at the base of San Gabriel Mountains are spared the worst. But this week the foothills were at a surprisingly concentrated epicenter of destruction that toppled trees and left residents without power or even water.

To understand what went wrong for the foothills on Wednesday night, Altadena Patch called up Jet Propulsion Laboratory scientist Bill Patzert, who has a knack for explaining climatology to the masses. (He called the Station Fire the Jabba the Hut Fire: "It's menacing and big, but it definitely can't move that fast.")

Patzert explained that the direction of the Santa Ana winds spelled disaster for the foothills:

Yeah usually here in the foothills locally we are immune to those northeast winds. But in these unusual situations where the winds are more northerly and cooler, the usual suspects are spared and the foothills get clobbered. And we see this every 10 years or so. But I’ve lived here in Sierra Madre for 27 years and this is the worst I’ve ever seen.
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But part of the reason for so much destruction also has to do with all those gorgeous trees that make the foothill cities look like dead-ringers for small Midwestern towns that get a lot of rain instead of dry, scrubby Southern California:

Right, the other thing that people don’t think about is that the urban forest in Southern California, especially here in the foothills, none of it is natural. This is all artificially planted, and about half of it is definitely the wrong trees - all these big conifers, big pine trees, and eucalyptus, which are so top heavy and have a bad profile. Such shallow root systems - they’re exactly the wrong kind of trees to plant here. And most of the urban forest is nurtured by lawn sprinklers! So they have a very shallow root system and when we get a situation like this, it’s like Humpty Dumpty: we definitely fall off the wall.

Here's the rest of the interview.