Southern California coastal communities are extending flood preparations through the end of the week as persistent high water levels, driven by El Niño conditions and strong ocean swells, continue to inundate low-lying areas.
The National Weather Service on Wednesday extended flood advisories for all coastal counties in Southern California through 2 p.m. Friday, according to Devin Black, a meteorologist for the weather service’s Oxnard office. Advisories were originally scheduled to expire Thursday afternoon. Orange and San Diego counties, which previously faced a more severe flood warning through Thursday afternoon, were likewise downgraded to a coastal advisory lasting through Friday afternoon.
Forecasters noted that seawater has pushed over low-lying areas, leaving some structures with shallow water reaching the base of buildings. The Balboa area of Newport Beach has experienced widespread flooding throughout the week, while Sunset Beach saw multiple flooded streets and a closure of the Pacific Coast Highway. Caltrans planned to keep portions of the highway closed through Thursday.
Long Beach emerged as a primary area of concern on Thursday, having faced acute impacts over the past several weeks. Tides across the region were projected to approach 8 feet Thursday morning before gradually subsiding into the weekend. While high tides affected the entire coastline, Black explained that the angle and magnitude of incoming swells played a major role, leaving San Diego and Orange counties particularly vulnerable due to their exposure to a southwesterly swell.
Some tides observed this week broke previous records, characterized by meteorologists as falling on the extreme end of the spectrum. These unusually high water levels are the product of multiple converging factors, including human-caused climate change, an El Niño-fueled Kelvin wave carrying warm water up the equatorial Pacific coast, and a separate, months-old marine heat wave.
Scientists report that the marine heat wave has elevated seawater levels by 1.25 to 1.8 feet beyond normal astronomical tides driven by the moon, Earth, and sun. Mark Merrifield, director of the UC San Diego Center for Climate Change Impacts and Adaptation, warned during a town hall months prior that the region would likely experience the highest sea levels ever recorded on the California coast due to the strengthening El Niño event.
Coastal communities now face the prospect of an arduous winter season. Forecasters warn that even higher tides are expected around the Thanksgiving, Christmas, and Martin Luther King Jr. Day holidays. The coincidence of a strong storm with these high-tide windows could trigger severe flooding reminiscent of the historic January 1983 storms, which battered the California coast during one of the strongest recorded El Niños and damaged piers up and down the state.
