Caused by cooler than normal sea-surface temperatures in the Pacific Ocean, La Niña typically causes a colder and drier winter in the Southland. Typically.
Though last season also had La Niña conditions, the rain came down fast and hard, albeit not consistently, said William Patzert, an oceanographer and climate forecaster at Jet Propulsion Laboratory.
“Here in Southern California, after two weeks in December, my forecast was already busted,” said Patzert. “Last winter is an example of where the statistics led us astray.”
According to records kept by Descanso Gardens, just over 32 inches of rain fell on the Foothills between Oct. 1, 2010 and Sept. 30 of this year.
While an average season delivers about 15 inches of rainfall locally, La Niña years generally result in 10-12 inches of the wet stuff. El Niño conditions, caused by warmer than normal sea temperatures, bring an average of 18-20 inches.
Pat Anderson’s home at the top of Ocean View Avenue was heavily damaged in February 2010 when the Mullally debris basin above her property overflowed, sending fast-moving debris and mud through her Paradise Valley neighborhood. Anderson said that with her house still being rebuilt, she has a lot riding on this season’s weather.
“Until my home is finished, even one heavy rainfall could cause heavy damage to my house,” Anderson said. “So, do I get nervous when I hear there’s going to be a significant amount of rain? Yes I do.”
Anderson, president and chief executive of the La Cañada Flintridge Chamber of Commerce, said she will be watching the forecasts closely.
“I trust my sources, which are the Fire Department and the Sheriff’s Department,” she said, “but I just have to hope for the best, which is not a good position to be in.”
Chris Stone of the L.A. County Flood Control District said that the county will not be altering its preparations for the rainy season based on the La Niña forecast. Stone said the county has made sure the debris basins serving the area are at least 95% clear, and that channels and catch basins are clear and ready to receive any excess rainfall.
Stone said the county is expecting this year’s rainy season will be similar to 2010-2011.
“The weather patterns so far are very similar to what we had last year,” said Stone. “We expect short to longer periods of dry between the wet patterns.”
Stone noted that the areas damaged in the Station fire are not expected to be fully recovered for another three years.
“We’re only two years of recovery after the Station fire so there’s still a very high potential for debris flows coming off the burned watersheds,” Stone said. “There’s been lots of good growth, but there’s still lots of challenges remaining for this and next winter with debris flows.”
Still, JPL’s Patzert said residents should be fine.
“Odds are cool and dry,” Patzert said. “So far we’ve had some nice rain here, but nothing that heavy and nothing threatening the hillsides.”
In fact, Patzert said he’s hoping for more rain.
“I’d love to see a lot of rain,” said Patzert. “It suppresses the fire season and aside from some bad driving habits on the freeway by Southern Californians, in all other ways it’s a benefit for us.”
-- Daniel Siegal, Times Community News
Photo: The sun sets during rush hour on the Ventura (134) Freeway near Glendale, as rain showers move through the area on Friday, November 4, 2011. Credit: Tim Berger/Times Community News.
Editor's note: This story has been updated from an earlier version.