Despite all the concerns about a historic El Niño fueling epic storms hitting California this winter, there’s still a surprising amount of debate among experts about how serious the situation really is.
Scientists are very confident about the risk of coastal seawater flooding and beach erosion – fueled by sea level rise and strong waves – with king tides approaching Thanksgiving, Christmas and Martin Luther King Jr. Day.
But when it comes to predicting the strength of winter storms, there is much less consensus.
Officially, confidence on this subject is tempered, with some emphasizing a wide range of possible outcomes. “We have only more moderate confidence, at best, in freshwater flooding and associated debris flows if we see some of this stronger storm activity in Southern California,” said Robbie Munroe, a meteorologist with the National Weather Service in Oxnard.
Official seasonal precipitation forecasts released by the National Oceanic and Atmospheric Administration indicate that Southern California has a 60 to 70 percent chance of above-normal precipitation for January, February and March. “But that still leaves about a 30 to 40 percent chance that precipitation will be near or below normal, and so this winter is a no-brainer in terms of how the season as a whole plays out,” Munroe said.
Three of the past four winters have brought above-normal rainfall to Southern California, and only one of them coincided with an El Niño event. “So even if we see above normal precipitation, that doesn’t mean it’s going to be much different than what we’ve seen recently,” Munroe added.
“The big El Niño sets the stage,” said Julie Kalansky, deputy director of the Center for Western Weather and Water Extremes at UC San Diego. “El Niño doesn’t really dictate the outcome, but it does tip the scales in favor of a wetter winter, especially in Southern California.”
Others are putting more emphasis on why this winter could go down in the record books, in terms of rain.
Much of coastal California could receive nearly double the average precipitation for January, February and March, especially in Southern California, the San Francisco Bay Area and the Central Coast, according to Daniel Swain, a UC Agriculture and Natural Resources climatologist.
This is revealed by the ensemble mean – or mean – of the European Center for Medium-Range Weather Forecasts’ SEAS 5.1 model, which issues forecasts of the ocean and atmosphere months in advance.
A reasonably pessimistic scenario would involve precipitation more than two and a half times above average, Swain said. And it’s a scenario the state and local emergency planners should prepare for, he added.
Rain and snow are expected to return to California starting Friday, and “I expect we will start to see significant wet storms by December, especially from the San Francisco Bay area southward,” Swain said. “Right now it appears that January and February are the months most likely to experience heavy rain and potential flooding issues.”
In fact, “the chances of having a winter that is at least among the 10 wettest we’ve ever seen are very high,” Swain said. Additionally, “across the California coast, there is likely at least a 10 percent chance of a record wet winter, and the chance in a typical year of a record wet winter would be less than 1 percent.”
El Niño has already hit coastal California this year, causing flooding from San Diego to Marin County, damaging many homes and other structures and eroding coastal bluffs. But exactly how that will play out this winter is still to be determined. In early 1983, a powerful El Niño coincided with a historically memorable storm season, severely damaging docks and flooding many homes. But the last strong El Niño season, in 2015-2016, exceeded expectations and the winter was relatively dry in Southern California (although the coast saw record erosion).
On Oct. 26, crews are moving sand from the bottom of Alamitos Bay to widen the beach on the Long Beach Peninsula, where homes have been severely damaged by rising sea levels.
(Robert Gauthier/Los Angeles Times)
El Niño is a climate phenomenon marked by warmer ocean waters in the central and eastern equatorial Pacific Ocean, near Peru and Ecuador, which cause changes in the atmosphere that can affect weather patterns around the world. El Niño is usually, but not always, associated with a wetter than average winter in Southern California.
On Thursday, the National Weather Service’s Climate Prediction Center said El Niño continues to strengthen, with sea surface temperatures continuing to rise. There is virtually a 100% chance that this El Niño will be classified as “very strong,” and there is a 60% chance that this El Niño will be the strongest on record since modern record keeping began in 1950.
Some experts caution that very strong El Niño events are not a 100% bet on massive flooding in California. “Everyone sees El Niño — they think of massive flooding everywhere. Well, we’ve known that since 2015-2016 … that was a different situation, but it was still El Niño, and, you know, coastal southern California had 77 percent of normal precipitation,” said meteorologist Jan Null, an assistant professor at San Jose State University.
People should certainly prepare for heavier-than-normal precipitation, Null said, but the intensity of the destructive power depends on “the spacing of those rains throughout the winter.”
Swain noted that predictive models are now different than those available before the 2015-2016 El Niño season, and that new factors are coming into play this year, noting the intense rains that recently flooded swaths of the Four Corners region of Arizona, New Mexico, Utah and Colorado. “We’ve never seen oceans this warm before. We’ve never seen an atmosphere this hot before. We’ve never seen this much atmospheric water vapor in the air.”
Nov. 1: Members of the Tucson Fire Department rescue a woman from her car after she got stuck in a flooded wash.
(Mason Kumet/Associated Press)
“All of this tells us that I really think we need to be vigilant in a place like California about the risk of very heavy precipitation and the resulting risk of inland flooding this winter. The risk of coastal flooding,” Swain added, “is already there and it’s getting worse.”
Indeed, historic sea level records were broken in October in Southern California, San Pedro, Santa Barbara, San Diego Bay and La Jolla. Not only are we seeing unusually high astronomical tides (because we’re near the peaks of what’s known as the 18.6-year lunar node tidal cycle and the 4.4-year lunar perigee tidal cycle), but record warm ocean water off the California coast is causing sea levels to rise as warmer water takes up more volume.
All that ocean heat, influenced by El Niño and human-caused global warming, has caused average sea levels in Southern California to rise about 16 inches higher than would normally be expected by astronomical forces alone. This is much higher than any past record during an El Niño.
“We’ve never seen anything like this in terms of sustained sea level rise at this time of year on the Southern California coast. It’s truly extraordinary,” Swain said.
When king tides approach during the Thanksgiving holiday week, astronomical tides alone will be between half a foot and a foot higher than they were at the end of October, Swain said, depending on location. Added to this is the impact of winter storms and rising ocean temperatures, which are causing sea levels to rise further.
That means total sea levels could be 2 to 3 feet higher than recent record highs in late October, Swain said, “if a moderate or stronger storm aligns with the main tides.”
Swain has been outspoken about the criticism he received over his posts, which accused him of fear-mongering and, in essence, “El Niño means nothing to California. It can be wet. It can be dry.”
“What I’m doing here is not scaring people just for the sake of being dramatic,” Swain said. “But,” he added, “when there’s a remarkable signal for something that’s potentially very important… I’m going to say it clearly, and I’m the one doing it now.”
A series of storms is expected to hit California starting Friday and lasting until early next week. Through Saturday, between a quarter and an inch of rain will be common across Southern California, and there is a slight risk of thunderstorms along the coast. High waves are expected, perhaps enough to cause damage to piers, especially during the weekend on the Central Coast, the National Weather Service said.
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