Ocean waves up to 20 feet tall slam San Diego County beaches in wake of big storm

One of the largest ocean swells to hit San Diego County in years produced 10- to 12-foot waves in many spots Friday and periodic breakers that reached up to 20 feet, according to the National Weather Service and San Diego lifeguards.

The biggest surf was reported at and near La Jolla Cove, where the swell peaked at 20 feet before dawn then dropped to about 18 feet. The waves also hit 18 feet at Mission Beach. The swell will weaken throughout the weekend.

Lifeguards say that one surfer had to be rescued off Windansea Beach and another required assistance not far from La Jolla’s Children’s Pool. The waves damaged a safety railing on the pool’s breakwater.

A surfer takes off on an early morning wave at La Jolla Cove on Friday.

(Denis Poroy/For The San Diego Union-Tribune)

The Ocean Beach pier was closed on Thursday, about the time the first huge sets started rolling in.

The west-northwest swell was generated by a “bomb cyclone,” which is how meteorologists describe a low-pressure system that rapidly intensifies into a huge storm. The explosion occurred off the California coast and sent drenching rains ashore across the state. The system’s waves also heavily damaged the famed Capitola Pier near Santa Cruz.

The North Pacific storm gained additional strength by drawing moisture from the subtropics. It was the fourth time this season that a storm generated a so-called atmospheric river.

Forecasters say the next atmospheric river-infused system could hit Northern California on Monday, then drop into Southern California on Tuesday. It appears that San Diego County’s coastal cities could get about a half-inch of rain while some inland areas receive twice as much.