El Nino at last, parade of storms aimed at California | TahoeDailyTribune.com

El Nino at last, parade of storms aimed at California

Patrick McCartney

El Nino agnostics are heading for cover this weekend, as one potent storm after another is lined up to plow into an already waterlogged California.

Forecasters are calling for up to 3 feet of snow in the Tahoe Basin Friday, with another storm poised to move onshore by Sunday following a brief break in the weather.

After months of teasing residents of Lake Tahoe and the West Coast, El Nino is finally living up to its reputation, say climatologists who study fluctuating sea temperatures in the tropical Pacific Ocean. Warmer water in the eastern Pacific off South America is associated with wet winters across the southern United States.

“The storms are lined up across the Pacific as far as we can see them,” said Kelly Redmond, an El Nino expert with the Western Regional Climate Center. “This is the type of thing people had in mind last summer when (an El Nino) became a possibility.”

Friday’s storm is being propelled by one of the strongest jet streams on record, Redmond said, with wind speeds as high as 250 mph over the central Pacific. The National Weather Service has issued gale warnings for much of the Pacific Coast.

True to form, the El Nino influence in the past month has favored some areas of California more than other areas. For much of the winter, the split jet stream typical of many El Ninos has produced deluges along the coast but a lesser amount of snow and rain in the Sierra.

In a typical year, the Tahoe Basin will receive about 50 percent more precipitation during the wet season than San Francisco, according to weather records at Tahoe City that are the oldest and most reliable in the basin.

This year, however, the Lake Tahoe Airport had received 17.54 inches of rain and snow through Thursday, lagging behind San Francisco (28.8 inches) and even Sacramento (18.76 inches). Precipitation totals for Lake Tahoe are barely above average for the date, while San Francisco has received more than twice its long-term average and Sacramento 60 percent above average.

As it turns out, San Francisco’s seasonal precipitation has exceeded Lake Tahoe’s in just four years since 1931 – in 1941, 1973, 1976 and 1978. And three of those years (1941, 1973 and 1978) were El Nino years, while the fourth (1976) experienced the cold-water phenomenon, La Nina, Redmond said.

“Blue Canyon usually gets four times more precipitation than San Francisco. Last year, Blue Canyon received eight times more precipitation,” Redmond said. “But with the El Nino this year, what often happens is a splitting storm front drops its load on the coast, and then the energy that would usually go over the Sierra instead heads south to Southern California.”

With the current El Nino rivaling the 1982-83 event as the strongest of this century, the storm track has also drifted farther north than in some El Nino years, Redmond said.

“The main storm belt has been coming in around the latitude of San Francisco,” he said. “With the big El Nino of 1982-83, it shifted north a little bit and gave extra precipitation to Oregon and Washington.”

While this year’s El Nino is beginning to live up to its advanced billing, predicting how strong individual storms will be in the Tahoe Basin remains a precarious exercise, said Beth McNulty, a meteorologist with the National Weather Service office in Reno.

“We’ve had these things look very potent, and then they split and go south or north,” McNulty said, declining to forecast how strong the storm scheduled to arrive by late Saturday will be by the time it arrives in the basin. “Every storm can look the same coming in, but there are subtle differences that can make one split and not another. It’s all up to Mother Nature.”

Tahoe Daily Tribune E-mail: tribune@tahoe.com

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