June 21, 2024
There is a 95 percent chance of an El Niño occurring between December 2023 and February 2024, and a 66 percent that it will be a "strong" El Niño.

Phil Diehl | The San Diego Union-Tribune

San Diego County’s fragile shoreline and vulnerable beachfront properties could be in for a rough winter, according to the California Coastal Commission, the National Weather Service and some top San Diego scientists.

“We are looking at an emerging El Niño event,” staff geologist Joseph Street told the Coastal Commission at its meeting Wednesday in Eureka.

An El Niño is a meteorological phenomenon that occurs every two to seven years. The water temperature at the surface of the Central Pacific Ocean along the equator warms a few degrees above its long-term average, creating conditions for stronger, more frequent seasonal storms across much of the globe.

“El Niño conditions can generate a triple threat for coastal hazards in California,” said Adam Young, an integrative oceanography researcher at Scripps Institution of Oceanography in San Diego.

“Increased rainfall triggers landslides, powerful waves can accelerate erosion of beaches, sea cliffs, and bluffs, and cause coastal flooding, and strong El Niño conditions can raise sea level on the California coast by 6 to 13 inches,” Young said. “Combined, these factors increase coastal erosion and flooding … which can threaten public parks, beaches, critical infrastructure, highways, and homes.”

The Coastal Commission’s webpage at www.coastal.ca.gov has been updated with El Niño information and resources, and staffers are working to publicize the situation.

“We are kind of raising the flag on this,” said commission Chair Donne Brownsey.

“Every single day there is a new report about the warming ocean, the rising seas, and the accelerated melting of the arctic,” Brownsey said. “It just goes on and on. This is a harbinger that is really scary.”

Powerful storms can be “a formula for disaster” in coastal communities already subject to seasonal flooding, said Imperial Beach Mayor Paloma Aguirre, who represents San Diego County on the Coastal Commission.

“We see it first-hand in Imperial Beach,” Aguirre said. “We just had the first-ever tropical storm make landfall in San Diego County. It’s extremely concerning to say the least.”

Tropical Storm Hilary dropped more than 2 inches of rain on most parts of San Diego County in August, and as much as 7 inches at the highest elevations. August is normally one of San Diego’s driest months of the year, with an average precipitation of about one-third inch along the coast.

There is a 95 percent chance of an El Niño occurring between December 2023 and February 2024, and a 66 percent that it will be a “strong” El Niño, according to an update issued Tuesday by the National Weather Service. Indicators include above average sea surface temperatures and “atmospheric anomalies” in the Pacific.

Still, predicting the weather is notoriously difficult.

El Niño conditions do not cause individual storms, rather they influence the frequency and characteristics of storms.

“El Niño alone is not a reliable bellwether for a major storm season,” said Street, the commission’s geologist. “We’ve had several fizzles.”

Many variations can take shape for an El Niño, and only time will tell if this winter brings a whopper.

Two of Southern California’s strongest El Niños occurred in the winters of 1982-83 and 1997-98, bringing extensive flooding, landslides, coastal erosion and damage to coastal structures. Statewide storm-related damage in ’97-98 was estimated at more than $1 billion, according to the Weather Service.

In January 1993, considered one of the milder El Nino years, Camp Pendleton Marine Corps base shut down after 11 consecutive days of rain to deal with water 15 feet deep on the air station and parts of Vandegrift Boulevard. A Marine general estimated the damage to property and military equipment at $70 million.

El Niño conditions last occurred in Southern California in 2015-16 and brought powerful waves and coastal erosion. But there was less rainfall than expected and little structural damage simply because the jet stream carried most of the storms to the north.

A year ago, the winter of 2022-23 was unusually wet with powerful storms and some of the biggest ocean waves the area has ever seen. Still, that season did not have the ocean temperatures and atmospheric conditions of an El Niño.

Rail service in Southern California is particularly vulnerable to the landslides and bluff failures brought by winter storms.

Weather-related landslides at two coastal trouble spots in San Clemente forced the suspension of passenger service for months at a time over the past two years. The tracks along the coast through Orange County are the only link between San Diego and Los Angeles for rail passengers and freight.

Emergency bluff repairs in 2021 cost more than $10 million at Del Mar, where a series of railroad stabilization projects have been underway for more than 20 years.

Any series of strong storms can cause a temporary rise in sea level that increases flooding and erosion, said Jeremy Smith, an engineer on the Coastal Commission staff. That happened in 2016, when ocean waters rose as much as 8 inches along some parts of the California coast.

“Strong storms in quick succession can be damaging,” Smith said. “The worst damage occurs when large swells combine with high tides.”

The highest tides of the year, known as “king tides,” occur on a few days in mid-summer and mid-winter. This winter’s king tides will be Jan. 11 and 12 and Feb. 9 and 10, 2024.

“Widespread coastal damage that occurred during the winter of 1982-83 was due in part to the combination of large storm waves with very high tides,” states a commission staff report.

“Some of the highest tides for the 2023-24 winter will occur close to holidays,” it states. “This highlights the need for early preparation since holidays are times that people tend to travel and go on vacation.”

Preparation includes cleaning out gutters, storm drains and flood control basins, inspecting roofs for leaks, and planting ground cover on bare spots.

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Narrow beaches and low sand volumes, an increasing problem along the Southern California coast, also make coastal regions more vulnerable to storm damage.

Even if this year’s El Niño is mild, intense storms are certain to occur in the next few years, staffers said.

In addition to warming the ocean’s surface, the El Niño phenomenon brings warmer temperatures in deep water and the atmosphere that also affect the weather. There’s a related term, La Niña, in which cooler temperatures and drier conditions prevail.

“El Niño and La Niña are the result of complex interactions between the ocean and the atmosphere,” said Shang-Ping Xie, a professor of climate science and physical oceanography at Scripps.

Both conditions originate far from San Diego along the equator in the tropics.

“The tropics are like the engine room of the Pacific,” Xie said. “Heat in the tropics drives global atmospheric circulation. In that sense, variations in the tropical Pacific like El Niño can have huge impacts on global weather patterns.”

The El Niño phenomenon was first noticed by South American fisherman. The name is Spanish for “little boy” or sometimes “the Christ child,” because the conditions usually occur around Christmas.

This story originally appeared in San Diego Union-Tribune.