The National Weather Service issued a coastal flood advisory for Los Angeles County beaches starting at 5 a.m. Sunday, Oct. 25, and lasting through 1 p.m. Thursday, Oct. 29.
The advisory covers South Bay shorelines including Manhattan Beach, Hermosa Beach, Redondo Beach and El Segundo as part of the broader Los Angeles County beaches zone. The NWS expects tides to reach 7.5 to 8 feet above mean lower low water each late morning, about 1 to 1.5 feet higher than astronomical projections, according to the Daily Breeze.
The highest tides are forecast Monday through Wednesday.
The weather service warned of "minor to moderate flooding of sea water" over low-lying coastal areas around high tide, including beach parking lots, bike paths and harbor walkways. Moderate to significant beach erosion is likely, and isolated structural damage from seawater is possible in the most vulnerable spots, the NWS said.
This round of coastal flooding differs from earlier episodes driven by hurricane-generated swells. Surf along L.A. County beaches is expected to stay in the 1- to 3-foot range, KTLA reported. But the unusually elevated ocean levels alone could still cause flooding during late-morning high tides.
Todd Hall, warning coordination meteorologist for the NWS office in Oxnard, told the Los Angeles Times that areas with existing beach erosion or infrastructure damage face added risk. Any additional flooding "exacerbates the issue because the damage is already there," Hall said.
Scientists point to several forces behind the elevated tides. A rare alignment of the Earth, sun and moon, part of an 18.6-year lunar cycle, is pushing peak tides higher. Record-warm ocean temperatures off the California coast, fueled partly by El Niño, are also raising sea levels because water expands as it heats, the Times reported.
The NWS said actual tides in Southern California are running 1.25 to 1.75 feet above what astronomical positioning alone would produce.
Cities across the region have been preparing by building sand berms, positioning sandbags in harbor areas and readying pumps in case water flows into streets, the Daily Breeze reported. No specific emergency declarations or preparedness announcements from Manhattan Beach, Hermosa Beach, Redondo Beach or El Segundo had been reported as of Saturday, Oct. 24.
The advisory could be upgraded to a coastal flood warning Wednesday or Thursday if larger surf develops, the NWS said.
The weather service urged residents to protect flood-prone property and not drive around barricades or through water of unknown depth. Residents can monitor advisories at the NWS Los Angeles forecast office.
