Coastal flooding from Newport Beach to Long Beach destroyed homes and inundated roadways this week, a highly unusual combination of events that underscored the challenges California faces amid forecasts for a “super” El Niño winter.
The flooding was extraordinary, scientists said, showing how incoming Tropical Storm Rachel and high tides, record-hot oceans and El Niño-induced waves could inundate coastal areas.
“The combination of high tides, Kelvin waves, hurricane waves — and then all summer long? That’s unprecedented,” said Jonathan Warrick, a research geologist with the U.S. Geological Survey. “That’s what we’re looking for in the future,” as El Niño approaches, with the potential for relentless winter storms and king tides during the holidays.
The center of Rachel is expected to move ashore over northern Baja California on Saturday night. Its San Diego office said the Orange County and San Diego coast will face the highest risk of flooding Sunday morning due to a combination of surf, onshore winds and high tides. On Sunday morning, high tide was at 9:43 a.m. in La Jolla and 9:48 a.m. in Newport Beach.
Warwick and others said this week’s events could provide clues for next season.
“I’m not 100 percent sure we’re going to see this this winter, but we’re probably going to see more of this this winter,” Warwick said. “Looking ahead over the next few decades, there will be more of these types of events in the coming decades as sea levels continue to rise.”
The highest high tides of the year hit California around the summer and winter solstices. Some disasters are expected on Thanksgiving Day, Christmas Eve and January 22nd. If these disasters coincide with severe winter storms, they could lead to coastal erosion, flooding and damage, said Reinhard Flick, a researcher at the Scripps Institution of Oceanography at the University of California, San Diego.
Approximately every 18.6 years and every 4.4 years, the tides are particularly large. We are approaching the peak of these cycles. “That means around Christmas you’re going to have some very strong king tides in California that are going to be superimposed on top of the high sea levels caused by El Niño,” Mark Merrifield, director of the Scripps Center for Climate Change Impacts and Adaptation, said earlier this year.
El Niño is a climate pattern characterized by unusually warm temperatures in the central and eastern equatorial Pacific, causing atmospheric changes that typically lead to above-average precipitation in Southern California.
The two strongest El Niños in the past 75 years caused widespread damage to the Southern California coast, destroying homes, flooding streets and destroying piers. Another spell of rain did not result in above-average rainfall, but it did cause record coastal erosion.
A Long Beach resident stands next to coastal floodwaters amid huge waves and high tides caused by Tropical Storm Rachel.
(Mario Tama/Getty Images)
This week’s flooding in Orange County is likely caused not only by downgraded Tropical Storm Rachel, but also by the recent arrival of El Niño-induced Kelvin waves, which move slowly along the American coast from Peru at about 6 miles per hour. It’s not the kind of wave that’s surfable or visibly visible on the ground, but it can raise background sea levels by about 6 to 12 inches, bringing warmer water that contributes to sea level rise (because hotter water requires more volume).
“I mean, I grew up there. I was in Newport Beach every day as a kid, and I’ve never seen anything like this. This is completely unprecedented. It’s shocking,” Warwick said.
Such Kelvin waves could keep sea levels rising for months before their effects wear off. Kelvin wave expert Dillon Amaya, an assistant professor in the Department of Ocean, Earth and Atmospheric Sciences at North Carolina State University, said another Kelvin wave he is monitoring is about to appear off the coast of Mexico. Southern California is still at least a few weeks away.
The leading edge of the Kelvin wave has currently passed through Los Angeles and San Francisco.
“Hurricanees are definitely a trigger for storm surge, but Kelvin waves will almost certainly affect background sea conditions, making this flood more dangerous,” said Amaya, who earned a PhD in oceanography from the Scripps Institution of Oceanography at the University of California, San Diego.
City officials have been frantically preparing for Rachel, building sand berms and fortifying vulnerable areas with sandbags.
The National Weather Service said water levels at tide gauges in the Port of Los Angeles peaked at 7.7 feet Saturday morning, about 1.6 feet above forecast tides. “Sunday morning’s high tide is expected to be about 8 feet, which will approach or exceed recent record tide levels in Los Angeles County,” the report said.
Only two tropical storm-force storms have crossed the state or been offshore of the state in modern records.
The first storm—nicknamed “El Cordonazo” or “The Whip of St. Francis”—hit Long Beach and San Pedro in September 1939. It brought 5.62 inches of rain to Los Angeles over three days and produced wind gusts of up to 65 mph, resulting in 45 deaths in flooding and another 48 at sea.
Nora also appeared in September 1997, its center briefly reaching tropical storm strength as it passed along the California-Arizona border, but California did not suffer the same damage it did to Baja California. Street flooding was reported in Pillar County, the Coachella Valley and San Diego, and large waves from NOLA and another storm caused seals to crash into beachfront homes in Seal Beach, severely damaging three homes and causing minor damage to 45 others.
Nora arrived during a “very strong” El Niño season. El Niño is associated with above-average hurricane activity in the eastern Pacific.
The National Oceanic and Atmospheric Administration’s Climate Prediction Center said Thursday that there is almost a 100% chance that this season’s El Niño will be classified as “very strong.” There is an 83% chance that this El Niño will be the strongest on record since 1950, up from the 75% chance predicted last month.
Times staff writers Jasmine Mendez, Hannah Fry and Jaweed Kaleem contributed to this report.