The coastal flooding that damaged homes and flooded roads this week from Newport Beach to Long Beach came from a highly unusual combination of events that underscores the challenges California is facing amid predictions of a “super” El Niño winter.
The flooding was extraordinary, and scientists said they show how the approaching Tropical Storm Rachel, along with high tides, a record-hot ocean and El Niño-fueled waves, can overwhelm coastal areas.
“The combination of high tides, Kelvin wave, hurricane waves — and then a whole summer worth of that? This is unprecedented,” said Jonathan Warrick, a research geologist with the U.S. Geological Survey. “And this is what we got to look forward to in the future,” with a long El Niño season ahead, and the possibility of a relentless parade of winter storms and king tides during the holiday season.
The center of Rachel was expected to move onshore in northern Baja California on Saturday night. Its San Diego office said Sunday morning would carry the highest flooding risks along Orange County and San Diego coast as swells, onshore winds and high tides combine. High tide on Sunday morning is at 9:43 a.m. in La Jolla and 9:48 a.m. in Newport Beach.
Warrick and others say this week’s events could offer clues to next season.
“I won’t say 100% sure we’re going to see this this winter, but this is a type of thing we may see a lot more of this winter,” Warrick said. “And then looking forward into the coming decades with continued sea level rise, this is exactly the type of event that will be seeing a lot more of in the coming decades.”
The highest high tides of the year hit California roughly around the summer and winter solstices. Some are expected on Thanksgiving Day, Christmas Eve and Jan. 22. Should they coincide with strong winter storms, coastal erosion, flooding and damage are likely, according to Reinhard Flick, a researcher at the UC San Diego Scripps Institution of Oceanography.
Roughly every 18.6 years and every 4.4 years, the tides are especially big. And we are near the peaks of those cycles. “That means that around Christmastime, California will see some very strong king tides that will superpose on the high sea levels caused by El Niño,” said Mark Merrifield, director of the Scripps’ Center for Climate Change Impacts and Adaptation, earlier this year.
El Niño is a climate pattern marked by unusual warmth in the central and eastern equatorial Pacific Ocean, and results in changes to the atmosphere that, typically, lead to above-average precipitation in Southern California.
Two of the strongest El Niños in the last 75 years were associated with extensive damage to the Southern California coast, battering homes, flooding streets and damaging piers. Another one did not result in above-average rain, but did cause record coastal erosion.
A Long Beach resident stands by coastal floodwaters amid strong waves and high tides generated by Tropical Storm Rachel.
(Mario Tama / Getty Images)
This week’s flooding seen in Orange County is likely the result of not only swells from Tropical Storm Rachel, which has been downgraded from a hurricane, but also the recent arrival of an El Niño-fueled Kelvin wave that moved slowly up the coast of the Americas from Peru, at a speed of about 6 miles per hour. It’s not the kind of wave that can be surfed or obviously seen at the surface, but it can raise background sea levels by perhaps 6 to 12 inches, bringing along warmer waters that — because hotter water takes more volume — increase the sea level.
“I mean, I grew up down there. I was on Newport Beach every day, you know, when I was a kid, and I’ve never seen anything like this. This is completely unprecedented. It’s shocking,” Warrick said.
This Kelvin wave could keep sea levels elevated for months before its effects fade. And there’s already another Kelvin wave that he’s monitoring that’s coming up the coast of Mexico, said Dillon Amaya, an expert on Kelvin waves and an assistant professor at North Carolina State University’s Department of Marine, Earth and Atmospheric Sciences. It’s at least a few weeks away from Southern California.
The leading edge of the current Kelvin wave has already passed L.A. as well as San Francisco.
“The hurricane is definitely the triggering factor in terms of providing the storm surge, but the Kelvin wave almost certainly conditioned the background sea state such that flooding was more dangerous this time,” said Amaya, who got his doctorate in oceanography at the Scripps Institution of Oceanography at UC San Diego.
City officials have been frantically preparing for Rachel, building sand berms and fortifying vulnerable areas with sandbags.
Water at the Los Angeles Harbor tide gauge peaked at 7.7 feet Saturday morning, about 1.6 feet above the predicted tide, the National Weather Service said. “The projected high tides of around 8 feet for Sunday morning would approach or exceed recent record tide levels for L.A. County,” it said.
In the modern record, only two storms have passed through or just offshore of the state at tropical-storm strength.
The first — nicknamed El Cordonazo, or the Lash of St. Francis — hit Long Beach and San Pedro in September 1939. It dumped 5.62 inches of rain on L.A. over three days, spawned wind gusts of up to 65 mph and resulted in 45 deaths from flooding, with an additional 48 deaths at sea.
In September 1997 there was also Nora, which was briefly at tropical storm strength as its center passed along the California-Arizona border, but California was spared the kind of damage it delivered to Baja California. Street flooding was reported in Imperial County, the Coachella Valley and San Diego, while big waves boosted by Nora and another storm sent breakers crashing into beachfront properties in Seal Beach, seriously damaging three homes and resulting in minor damage to 45 others.
Nora arrived during a “very strong” El Niño season. El Niño is linked to above-average hurricane activity in the eastern Pacific.
The National Oceanic and Atmospheric Administration’s Climate Prediction Center said Thursday that there is virtually a 100% chance that the El Niño this season will be categorized as “very strong.” There’s also an 83% chance that this El Niño will be the strongest on record, which goes back to 1950, up from a 75% probability forecast last month.
Times staff writers Jasmine Mendez, Hannah Fry and Jaweed Kaleem contributed to this report.