In some spots, waves could be large enough to damage piers, and could cause coastal flooding and significant beach erosion. Breaking wave heights of up to 40 feet are possible along the Northern California coastline, with the peak swell arriving near high tide late Thursday morning.
“People are advised to stay out of and well away from the water, and keep a close eye on kids and pets,” the National Weather Service for the Bay Area wrote on Wednesday. “These are deadly conditions that can easily overpower the strongest swimmers.”
Satellite data showed waves about 42 feet high in the open ocean far offshore on Wednesday, said Alexis Clouser, a meteorologist with the Bay Area weather office in Monterey, Calif.
“These are not the highest wave heights we’ve seen, but they’re certainly on the larger side,” she said. “They are deadly due to their size and the potential run-up — our biggest concern is people getting too close to the water and potentially getting swept in.”
Waves between 10 and 20 feet and up to 25 feet high could strike parts of the central and Southern California coasts, and could flood vulnerable low-lying areas including beach parking lots and roads. West-facing beaches face the greatest risk, and the large swell could cause impacts as far south as San Diego County. Weather offices are advising that “everyone” should stay out of the water because of the hazardous surf.
“These are forecast to be EXTREMELY DANGEROUS conditions, as powerful waves and life-threatening rip currents pose an exceptional risk of ocean drowning and damage to coastal structures such as piers and jetties,” the National Weather Service in Oxnard, Calif., warned on Wednesday.
Because of the holidays, there may be more visitors than usual at beaches this week.
“What happens a lot of times is somebody goes to the ocean to watch the waves — they go to a beach or parking lot or walk out onto a jetty — and then a bigger set of waves comes and overwhelms them,” said Tom Fisher, a meteorologist with the National Weather Service in Oxnard.
High surf is an underappreciated and often fatal hazard during California winters. During an especially tragic stretch from November 2020 to February 2021, eight people died in the San Francisco Bay Area, including children, as they were frolicking near the water and got swept out to sea by giant “sneaker waves.”
Such waves surge well beyond the normal surf line and can easily overtake those unaware of the danger, pulling them into cold, rough seas.
A recent study found that California’s winter waves have grown bigger since 1970 because of climate change, a result of increased storminess and an intensification of the wintertime low-pressure center near the Gulf of Alaska known as the Aleutian Low.
This week’s enormous swell is being pushed by winds racing across the Pacific Ocean, thanks to an area of strong low pressure off the West Coast. An active weather pattern is sending a pair of storm systems and associated atmospheric rivers into the Pacific Northwest and California this week — one that moved through Wednesday and into Thursday, and another arriving Friday.
The highest precipitation totals are expected at the California-Oregon border and along the Northern California coast, where more than 4 inches of rain could fall through Saturday.
The wet weather will also reach into Southern California this weekend and light rain could fall on the annual Rose Parade on New Year’s Day in Pasadena. It rarely rains on the parade — there is only about a 12 percent chance of rain on any given day this time of year in the area, the Los Angeles Weather Service said.
