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Santa Ana winds: Rare weather system produced powerful gusts

December 1, 2011 |  4:50 pm

Bina Takeuchi, 15, jumps off an uprooted tree on Duane Avenue in San Gabriel. School was canceled for Bina on Thursday due to heavy winds Wednesday night, which uprooted many trees in this neighborhood. Credit: Gary Friedman / Los Angeles Times

The destructive Santa Ana winds that hit Southern California produced some of the strongest gusts in more than a decade and was caused by a highly unusual weather system.

The winds were produced by two separate weather systems that channeled cold air from the north into the Los Angeles area.

A counter-clockwise low-pressure system was parked over California while a clockwise high-pressure system hovered over Arizona, Nevada and the Great Basin.

PHOTOS: Santa Ana winds | Submit your photos

Like two massive gears spinning in opposite directions, the systems funneled the winds.

“In some places we’ve seen gusts over hurricane force, which for the southwest part of the country is not something that usually happens. This is a one every 10 years kind of thing,” said Brian Edwards, a meteorologist for AccuWeather.com.

Indeed, the blustery conditions extended across the Southwest, including Utah, Nevada, Wyoming, Arizona and New Mexico. In some places, including Utah, wind gusts topped 100 mph.

Experts said one reason for the extensive damage was that the winds were remarkably choppy and unpredictable. In some places, winds suddenly shifted from 10 mph to 20 mph to more than 80 mph. The shift made trees as well as roofs and power lines vulnerable.

“Everything lined up perfectly,” said Bill Patzert, a climatologist for the Jet Propulsion Laboratory in La Canada-Flintridge.

Trees were no match for the winds, especially  those with heavy canopies. Patzert noted that since the vast majority of trees in Southern California were planted, they don’t have the strong root system of native vegetation.

“L.A. trees don’t have deep roots. The urban forest is artificial and is primarily watered by lawn sprinklers,” Patzert said. “So what keeps our urban forest alive is people watering their lawns, which are not natural, so you don’t have deep root systems. So our trees are very vulnerable to Santa Ana events.”

RELATED:

High wind forecast: 'It isn't over yet'

California windstorm: Widespread damage, more wind coming

Santa Ana winds: Trees toppled on Christmas Tree Lane in Altadena

--Hector Becerra and Matt Stevens

Bina Takeuchi, 15, jumps off an uprooted tree on Duane Avenue in San Gabriel. School was canceled for Bina on Thursday due to heavy winds Wednesday night, which uprooted many trees in this neighborhood. Credit: Gary Friedman / Los Angeles Times

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