PASADENA – Climatologists who study the dynamics behind Santa Ana winds marveled at the show of strength behind Thursday’s epic windstorm but steered clear of calling it more than a once-in-a-decade spectacle.
With recorded winds in areas surrounding Pasadena reaching a high of about 70 mph, according to the National Oceanic and Atmospheric Agency’s National Weather Service, the storm toppled hundreds of trees and left thousands of residents and businesses without power.
NOAA forecast the winds as “the strongest easterly wind event in the past several years,” which combined with dry conditions to create “a significant fire threat” in the Southland.
Bill Patzert, a veteran climatologist with NASA’s Jet Propulsion Laboratory, offered insight from his Sierra Madre home – where he was blockaded by a chimney that the storm ripped from his neighbor’s house and lodged in his driveway.
“This is definitely not global warming; this is weather,” Patzert asserted, calling the Santa Anas an “embedded” part of Southern California’s history for hundreds of years.
Only 15 years ago, winds up to 80 mph (and gusts of 127 mph) tore through the Valley, according to a JPL history primer recalling the 200 destroyed or damaged trees and blown-out windows that marred the La Canada campus.
The only difference now, Patzert said, touching on a favorite topic, is that “there are so many of us in nature’s way.”
And while the damage this time is palpable, Patzert eschewed comparisons to recent hurricane disasters.
“When you have really big strong hurricanes like Hurricane Andrew, this is puny. It’s big for us, but doesn’t compare with the big hurricanes – for one thing you often have tremendous flooding associated with them; this is just wind damage.”
The other thing, he said, “is this is so very gusty. We had 20 to 30 mph winds last night and all of a sudden like a train rolling out of the mountains it just slammed us.”
Marilyn Raphael, a professor of geology with UCLA, called the storm “a relatively infrequent occurrence.”
Both she and Patzert acknowledged it was the strongest of its type they’d ever personally seen.
Raphael follows the Santa Anas closely, mostly tracking data related to frequency and temperatures.
What is peculiar about this event, she explained, is that it has been relatively cool.
“Part of that is because of the cold air associated with the low pressure system, which is a little bit southeast of us. There was a cold front in there and we’re experiencing the cooler temperature on the backside of that front.”
Eric Boldt, a National Weather Service spokesman, explained how Pasadena and the San Gabriel Valley ended up taking such a beating in this particular system.
Data from Pasadena were scarce, but the highest recorded winds were between 50 and 70 mph; the strongest recorded – at 97 mph – were in Ventura County and the San Gabriel Mountains.
But, Boldt said, the corridor of strongest winds came across the eastern San Fernando Valley, the western San Gabriel Valley and even down into south Los Angeles.
All of this, he said, from a forceful north wind – to which Pasadena is particularly susceptible.
“Typically during a Santa Ana we get a storm system that moves down to the east and turns winds coming from the northeast or easterly, and often that doesn’t impact the Pasadena area,” he said.
“You really don’t see winds for that…it’s more focused on Santa Clarita. (But) in this case the low pressure was close enough to us that we saw winds out of the north more than northeast.”
The cold air system coming off the mountains also contributed, he said. “That tends to increase the wind speeds, that cold air has momentum going down the hill.”
And while many experts will be tempted to hasten a link between the extreme behavior and global warming, Raphael said she is hesitant to do so without more information. But unlike Patzert, she doesn’t rule it out.
“I would want to be more confident. I want to see a longer stretch of data on wind speeds associated with the Santa Anas than we have now. I’m not saying it isn’t, just saying I’d need more information to be able to say that.”
The information, she said, is there – it just needs to be mined.
“It would be a matter of going through the weather records and finding earlier occurrences of Santa Ana winds and speeds associated with them,” she said.
Going into the weekend, Boldt said high winds were expected to diminish overnight, though the weather service cautioned the Valley may see gusts of up to 50 mph this morning.
“Another system will be moving into place Saturday night, and right now it looks more like it’s out of the northeast or east, which is more typical. So that would kind of shelter the Pasadena areas.”
Winds now focused on the typical Santa Ana corridor – including the Santa Clarita and San Fernando valleys – are not expected to be as strong, Boldt said.
source: pasadena star news
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