First El Nino Storm on the Way

The first true El Nino storm of the season could strike Southern California this weekend, and forecasters say it may live up to all the advance billing.

“It looks pretty impressive,” said John Sherwin, a meteorologist with WeatherData Inc., which provides forecasts for The Times. “Los Angeles will be under the gun on Friday night, Saturday and Sunday. There could be a whole lot of rain.”

Earlier storms--like the brief but powerful downpours last week and the remnants of Hurricane Nora that drenched the Southland in September--were steered toward Southern California by El Nino, but they weren’t generated by the much-discussed meteorological phenomenon.

This storm, Sherwin said, is different.

“Right now, there’s strong high pressure over the Northwest, undercut by a subtropical jet stream,” the forecaster said Wednesday. “That’s definitely an El Nino pattern.”

Sherwin said warm, moist air from a vast tropical storm south of Hawaii was being pushed by the high-speed jet stream winds toward a cold, northern Pacific storm that was hovering about 700 miles west of California on Wednesday afternoon--the sort of conditions that existed repeatedly during the last severe El Nino winter, in 1982-83.

“If that cold storm can tap into that moisture--and it looks like it will--you could get two to three days of rain in Southern California,” Sherwin said. “There will be at least an inch of rain in downtown Los Angeles, with three times that in the foothills. And if it all comes together, there could be a lot more than that. During a storm like this a few years back, up to 10 inches of rain fell in the foothills.”

Sherwin said it was still too early to make any firm predictions about mudslides and flooding, but he did say that storm-generated surf up to 15 feet high is expected to start hammering the Central California coast by Friday. He said that as the storm moves down the coast toward Los Angeles, the high surf will move with it, with a possibility of coastal flooding and wave damage to oceanfront structures.

A weakening cold front ahead of the storm is expected to drop a few sprinkles on Southern California today.