Hey L.A., El Niño Rain Is Far From a Sure Thing

UPDATE at 12:32 p.m., Wednesday, Jan. 6, 2016: Our skepticism was prudent, but El Niño arrived right on-time. Here's our latest on storms hitting Southern California.

We're excited about El Niño, and we know you are, too.

But El Niño bringing 1983- or 1998-style storms to Los Angeles is far from a sure thing. The Pacific warm-water phenomenon that created that wet weather has been simmering for months, yes, but nobody can predict with certainty where storm-producing jet streams will aim this winter.

You wouldn't know it from reading local news or listening to L.A.'s leaders. We could indeed be in the midst of historic, unprecedented El Niño hype.

Sorry to rain on your parade. 

Last week Los Angeles Mayor Eric Garcetti, putting on his climatologist hat, said, "While we can never completely accurately predict the weather, it's about a 95 percent certainty that we will (see) a huge impact from El Niño this season.''

Maybe his honor should go back and check the data. His office admitted to us that he based that quote on federal Climate Prediction Center data. According to the center, "There is an approximately 95 percent chance that El Niño will continue through Northern Hemisphere winter 2015-16, gradually weakening through spring 2016" (emphasis ours).

Indeed, words are crucial here, lest we descend into hysteria.

Even the story that started it all, the Los Angeles Times' Aug. 13 report on the impending "Godzilla" El Niño, is based on a more subtly worded quote from Bill Patzert, a climatologist with NASA’s Jet Propulsion Laboratory in La Cañada Flintridge.

"This definitely has the potential of being the Godzilla El Niño," he said (emphasis ours).

Catch that? This could definitely maybe be a massive El Niño. It could also definitely maybe not be one, too. But that hasn't stopped an avalanche of hype.

Just Friday the Times declared in no uncertain terms: "A 'Godzilla' El Niño is on the way." Really? This newspaper apparently has Godlike weather prediction skills that put the Climate Prediction Center's to shame.

That entity says there's a 60 percent chance for above-average rainfall in Southern California this year.

At times this El Niño has appeared to be stronger than the last most powerful one we've had, the event of 1997-98 (a season during which we snowboarded in local mountains almost until May). So there is good reason to believe we'll get wet.

"This coming El Niño is projected to be very strong," says UC Irvine earth science professor Jin-Yi Yu. "There's a higher chance Southern California will have a higher amount of rainfall. But we always say things are likely, without certainty."

There's no guarantee a jet stream will strike Southern California, for example. It could strike just to the north. It could strike just to the south. Even with a strong El Niño. 

Yu explained that this El Niño, produced by extraordinarily warm waters in the equatorial and eastern Pacific, could push the polar jet stream, which produces most of the West Coast's precipitation, south into SoCal. It could also push the subtropical jet stream, which normally aims south of us, into our region, creating the warm-storm machine known as the Pineapple Express.

He thinks a Pineapple Express pattern is more likely and would do more damage. It could also be less beneficial to our water needs, since it probably would create warmer, more southerly precipitation that would not fully recharge the Sierra Nevada snowpack that creates much of our usable water.

El Niño is "the way nature brings rainfall to solve the drought problem," Yu said.

He believes the weather phenomenon is an integral, historic factor in our drought cycles. "One of the reasons we have drought is because we haven't had this regular, strong El Niño for a long time," he said.

But where those El Niño-supercharged jet streams will go, nobody really knows.

"There is a little bit of worry that we won't get as much rainfall as what's being advertised," says Scott Sukup, a National Weather Service meteorologist. "Any storms we get this winter will be dictated by how the jet stream sets up."

Today's best computer models can only give us accurate forecasts of what the weather will be like seven days from now – max. There are separate, seasonal models, but for now they're engaged in a game of educated guessing.

January, when a strong El Niño would normally start to show us heavy rain, is deep space to forecasters.

"It's hard to predict how much rain we'll get or whether we'll even get it," says Amir AghaKouchak, assistant professor of civil and environmental engineering at UC Irvine. "With a strong El Niño, typically, jet streams end up in Southern California, but a lot of other factors can potentially influence that sort of jet stream."

Because this time around water is warmer at higher latitudes than scientists have ever seen (affecting the Bay Area's Dungeness crab season, for example), it's possible that storms could be blocked.

"It's possible we'll end up with high-pressure ridges, really sustained, that divert storms," AghaKouchak says. "We don't know."

Yu, his UC Irvine colleague, calls the phenomenon the "Pacific blob." The warm water could produce these high-pressure systems, responsible for warm, sunny days, that would wall us off from those storm tracks known as jet streams, which would be diverted north or south of us.

"When you have warm water on the U.S. West Coast, it's likely to favor the upper-level ridge sitting on the coast, which will block the jet stream from coming through," he said. "This is a battle between a very strong El Niño event and the Pacific blob to determine what is going to happen to rainfall."

The professor says that the current El Niño mirrors those (1982-83, 1997-98) that brought us significant rain, so that's a logical indicator of what we're in for this winter.

But while some measures have shown this is one of the strongest El Niños on record, Sukup of the NWS notes that average equatorial Pacific water temps are actually lower than they were at this time ahead of the '97-'98 phenomenon.

In 1982 the average temperature was 1.5 degrees Celsius above average. In '97 it was plus 2 degrees. Today it's plus 1.7, Sukup says.

If Yu was asked to put money on the table, he'd bet on wet, however.

"Based on what we know with El Niño in the past, it's going to bring the jet stream close to Southern California," he says. "But uncertainty is hung on the Pacific blob. My view is that, either way, it will bring more water to California."

Experts also point out that there's little downside to expecting the worst.

"It's always better to be prepared than not," Sukup says.


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