6 Windstorm Questions for JPL Climatologist Bill Patzert

JPL climatologist Bill Patzert talks about why the winds were so strong, what made the storm so unusual, and our poor choices in an urban canopy.

When we got on the phone with JPL climatologist Bill Patzert he was just enjoying his first cup of coffee since the storm hit.

Like other local residents, Patzert does not have power and has been trying to get his own property back in shape since the storm hit. Patzert, a Sierra Madre resident, also has dug an old wire phone out of the closet since his wireless one does not work without power.

Patzert spoke with Patch about the storm, why it hit so hard, how it happened, and why it fizzled out Thursday. Questions and answers are below:

Patch: Can you start by giving a scientifically accurate, interesting and easy-to-understand explanation for this unusual wind system?

Patzert: November and December is really the primes season for Santa Anas, which are these really powerful high winds that come through the high desert and mountain passes. The history of Southern California is written in these great events: they are mild, they are medium, and then they are super duper.  And we had a super duper one. We had a high-pressure system over northern California and a low-pressure system in Arizona, and squeezing between those two systems, really cold air invaded Southern California.


But all Southern California did not get hit. It really got focused in the San Gabriel Valley.

Patch: Now I’ve read that a lot of the reason that the Pasadena, Altadena, foothills area got hit was because the winds came from the North rather than the Northeast, right?

Patzert: Yeah that’s correct … it was very cool and rather than Northeast it was straight out of the North and for some reason it really focused here in the foothills, which made it unusual. The usual suspects like the Santa Clarita River Valley and the Cajon Pass really got bypassed. So for some reason our number came up here. From La Canada to Sierra Madre, Temple City and Pasadena it was a little pocket of destruction. Wednesday night we had gusts anywhere between 80 to 90 mph surging out of the foothills and we’re still cleaning up and waiting for our electricity.

Patch: It is my impression living in the Pasadena area that when normal Santa Ana winds are forecast we don’t get them. They forecast these winds and then there’s no wind … so it that correct?

Patzert: 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.

Patch: After Wednesday night they changed the forecast from high winds to more normal winds, but it didn’t seem like any winds even arrived Thursday night. What happened?

Patzert: Yeah, those two systems I described—last night, rather than being so tightly squeezed together like they were Wednesday night, the high-pressure system drifted to the north and the low-pressure system to the east, so the typical Santa Anas that were forecast really never arrived. So we dodged a bullet last night … it was pretty calm across the Southland.

Patch: With the forecast ahead of the storm I don’t recall hearing anything about the unusual northerly winds, or about the foothills getting impacted so hard.  How well did the forecasters anticipate the impacts of this storm?

Patzert: That’s an excellent question: they were forecast as northerly winds and it was expected to be a cold Santa Ana-like system but nobody forecast the impacts in terms of location and intensity. So, you know, we’re not that good! But the fact is that it was so localized, I’m shocked it was not more widespread. It was a good forecast but not specific enough.

Patch: But then even if you have a specific forecast, it’s hard for people to prepare.  I guess people were told to secure loose objects, but there’s not much you can do to prepare for all this tree destruction.

Patzert: 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.

Hulga December 04, 2011 at 09:05 PM
Very interesting article! So what are good trees to plant? I saw plenty of downed oaks and sycamores and I always thought those had better root systems.


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