Sonoma County hopes for return of El Nino rains

Gorgeous green hills and spring-like sunny skies are a feast for the eyes, but no indication that winter is over nor that the strongest El Niño in history - which Californians are counting on to make a dent in the drought - is petering out.

Valley Ford cattle and sheep rancher Joe Pozzi, surveying the verdant pastures and stock ponds brimming with storm runoff, said the rain season is off to an ideal start.

“It’s excellent right now,” he said. “A welcome sign.”

Increasingly longer days and balmy weather like Monday’s 75 degrees in Santa Rosa have the grass growing, a critical factor for livestock ranchers, Pozzi said.

North Bay water managers are equally happy, with Lake Sonoma near Healdsburg at 96 percent of water supply capacity and Lake Mendocino near Ukiah at 108 percent of target capacity. The two reservoirs hold most of the water delivered by the Sonoma County Water Agency to 600,000 customers in Sonoma and Marin counties.

While rain has taken a break, with no significant precipitation in Santa Rosa since Jan. 29 and no more expected until the middle of next week, forecasters say there is no cause for alarm.

“We still have a lot of winter to go,” said Jan Null, a Saratoga-based consulting meteorologist. He noted that big storms have come in March and April, and it is common to endure a midwinter dry spell.

This year’s El Niño, the strongest one recorded since 1950, peaked around Jan. 1 and is now weakening but still capable of offsetting some the state’s four-year drought, he said.

Sea surface temperatures at the equator, El Niño’s signature, posted the warmest-ever three-month period in November through January, said Null, a former National Weather Service meteorologist who tracks El Niño data.

However, even a “very strong” El Niño - this one just the third in history - is no guarantee of above-average precipitation in California, he said.

The National Weather Service’s Climate Prediction Center said last month, in its most recent report, that “a strong El Niño will weaken (to neutral conditions) during the late spring or early summer,” noting that the exact timing “is difficult to predict.”

The center’s forecast said there’s a decent chance all of California will get above-average precipitation in February through April, with the region north of San Francisco Bay having a 33 percent probability. Central California a 40 percent probability and Southern California a 50 percent chance of extra rain.

Santa Rosa should see continued dry, warm weather through Sunday, said Steve Anderson, a Weather Service forecaster. The daytime high is predicted to reach 72 Tuesday, with temperatures in the low 70s through Friday, according to AccuWeather. The city’s 30-year average high temperature in February is 60.5 degrees, according to Press Democrat records.

Light rain is possible by the middle of next week, he said.

In January, Santa Rosa recorded nearly 11 inches of rain, 36 percent above the 30-year average of 7 inches for what is typically the wettest month of the year.

The region’s warm, dry spell was generated by an unseasonably strong high-pressure ridge that shunted moisture into British Columbia, Anderson said. It will dissipate and is not a revival of the persistent ridge that brought about the drought of the past three winters, dating from 2012, he said.

Despite the winter’s wet kickoff, ranchers and water managers say the region needs continued precipitation through spring to head into the hot, dry summer. Pozzi said he would like to see 3 inches of rain each month in March, April and May.

The Sonoma County Water Agency wants sufficient rain to keep reservoirs topped off through March, or even later, spokesman Brad Sherwood said. Another significant storm now would put Lake Sonoma over its water supply capacity - a level that hasn’t been hit in at least five years - and prompt the U.S. Army Corps of Engineers to release water from Warm Springs Dam.

The corps has agreed to let Lake Mendocino temporarily exceed its target capacity, he said.

Regardless of what Mother Nature and El Niño may bring, Sherwood said he hopes residents and businesses will continue conserving water.

“What we’re getting now might be all we get,” he said. “We all need to save water.”

The North Bay’s water system is a bit unique in that it is independent of the Sierra Nevada snowpack and the network of reservoirs, canals and pipelines that move water around California.

On Monday, the snowpack covered 46 percent of the Sierra at an average depth of 17.5 inches. A month ago, snow coated 73 percent of the range at an average depth of nearly 22 inches.

“In short, we’re not getting the sustained storms that would be needed to significantly add to the snowpack - and perhaps achieve 150 percent of normal by April 1,” said Doug Carlson, a Department of Water Resources spokesman.

All but one of the state’s major reservoirs are about half full or lower, with Folsom Lake at 60 percent capacity.

You can reach Staff Writer Guy Kovner at 521-5457 or guy.kovner@pressdemocrat.com. On Twitter @guykovner.