Forecasters stick to dry weather predictions

Forecasters reached a consensus last fall, predicting another extremely dry winter in the Southland. Then came the rains, with the latest scattered showers beginning Monday, driving up rainfall totals to levels meteorologists admit look a lot like . . . normal.

But don’t ask them to revise the dry winter forecast just yet.

“I’m sticking with it, even though we have a storm coming in,” said Bill Patzert, a climatologist for the Jet Propulsion Laboratory in La Cañada Flintridge. “I haven’t heard of anybody that’s broken ranks.”

Local forecasters track rain from July to June, and as of 4 p.m. Monday, downtown Los Angeles had received 5.99 inches of rain since July 1, 0.21 inches more than average for this time of year, according to the National Weather Service.

Average annual rainfall in Los Angeles is 15.1 inches, with the rainy season ending in March, and weather experts say it’s too early to change their long-term forecasts, particularly because of dry underlying weather conditions related to La Niña.

“We’re going to get more rainfall this week, especially later this week, but that doesn’t mean it can’t turn around after that,” said Ken Clark, a Rancho Cucamonga-based senior meteorologist for AccuWeather.com.

“We’ve been blessed with more precipitation than I would have thought at this point, and we really needed that rainfall, but that doesn’t mean we won’t finish the year below normal,” he said.

Clark recalled last year, when forecasters mistakenly predicted a wet winter based on a powerful El Niño, ocean warming along the South American coast that produces more frequent and intense rainstorms in Southern California. Instead, El Niño was weak and Southern California saw the driest year in 130 years.

Now, Clark and other forecasters are staking their dry winter predictions on La Niña, the opposite of El Niño, in which cooler South American ocean waters diffuse tropical storms, aggravating Santa Ana winds and leading to drier conditions across Southern California.

La Niña-based forecasts tend to be more accurate than those based on El Niño: Eight of the last 10 La Niñas forecast resulted in drier-than-normal local weather conditions.

Cool ocean temperatures show a moderate La Niña, just what forecasters predicted earlier this year, according to Stuart Seto, a weather specialist with the National Weather Service in Oxnard. A NASA satellite gathered images Jan. 14 that showed a band of cool water on the surface of the ocean, concentrated at the equator and fanning out toward North and South America.

“The La Niña is still going strong. It will still go strong until springtime,” Seto said. “It may not be dry all the time, but overall, the picture looks like we will be below normal.”

Patzert predicts that by the end of June, area rainfall would be 20% to 23% below average. National Weather Service forecasters were also still expecting a drier-than-normal winter.

This winter likely feels wetter than usual because it comes on the heels of last year’s record dry spell, forecasters said. This time last year, Los Angeles had received just 1.32 inches of rain.

“People’s memories are short. Last year was so very, very dry, it’s like this year is very wet, even when we get the puny little rain we’ve had so far,” Patzert said.

So far this month, rainfall in L.A. has totaled 2.23 inches, below the January average of 3.35 inches. December rainfall totaled 1.73 inches, below the average 1.91 inches. Rainfall totals have been below average for four out of the six months since July.

Even if Southern California sees rainfall reach average levels later this month, forecasters said the rain would likely disappear in coming months because of an ongoing drought that has sapped water supplies in several Southland cities, forcing some to ration water.

Although some plants are moisture-rich from recent rains, “within the context of the past few decades, it’s been particularly dry,” said Jon Keeley, a research ecologist for the U.S. Geological Survey.

It would take a deluge of rain, the two-day, 15-inch downpours more typical of Miami or New Orleans, to put a damper on dry weather, Patzert said.

“When you’re in a drought, normal’s not good enough,” he said of recent rainfall. “We have to recharge our snowpack, our groundwater, our reservoirs, feed Lake Tahoe, Northern and Eastern Sierras.”

For now, the forecaster is watering his garden by hand, and when he ventures out, he doesn’t take an umbrella.

molly.hennessy-fiske@ latimes.com