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Community Corner

Legendary Forecaster Explains Big Surf

High surf advisory now in effect until Sunday night. Sean Collins, chief forecaster and president of Surfline, tells Patch why the swell has a big impact.

Waves from a storm that originated near New Zealand have pounded Southern California beaches —and the National Weather Service on Friday announced that its high surf advisory for the Southland coast now remains in effect until 9 p.m. Sunday.

The dangerous surf has resulted in at least one  in Orange County and broken surfboards along the coast as surfers ventured to ride the waves.

Lifeguards across Southern California—from Imperial Beach to Zuma in Malibu—are patrolling beaches to make sure inexperienced surfers and swimmers stay out of the water and out of harm's way during Labor Day weekend.

Find out what's happening in Palos Verdeswith free, real-time updates from Patch.

Sean Collins, chief forecaster and president of Surfline, talked to Patch about the impact the recent swell has had on coastal communities.

Collins, known for accurately forecasting swells on a regular basis in the '70s and early '80s, created one of the first ongoing surf forecasts in California.

Find out what's happening in Palos Verdeswith free, real-time updates from Patch.

Now he and his team provide surf-related weather and forecasting services to local lifeguard agencies, the U.S. Coast Guard, Navy SEALs, National Weather Service and various surf companies.

Palos Verdes Patch: When was the last time we had a southern hemisphere swell this big hit California?

Sean Collins: Actually this is the biggest out of the southwest for quite a while. I think that the last one like this was April 2004. The swell in July 2009 that hit the U.S. Open of Surfing in Huntington Beach was actually a little bigger, but not as long a period.

Depending on the swell period, some areas will focus the swell energy better, like on Wednesday. The 20- to 22-foot periods were really focusing into some areas but completely missing others. Once the period dropped on Thursday, most other areas began to see the swell.

Patch: It seems like the swell hit earlier than forecast and the estimate of its duration is now longer than originally forecast?

Collins: Only because the spots that focus the longer periods picked up earlier. If we forecasted for that, most spots and surfers would have said we were wrong. We did say that the swell would be filling in Wednesday afternoon. Longer periods travel faster than shorter periods so that is why the long period spots flared up first.

Patch: Is it hard to predict the surf that is generated from southern hemisphere storms?

Collins: It’s the most difficult because there is so little data in the middle of the ocean to validate the models, and the models are off all the time. A difference of 5 knots of wind speed between 40 knots to 45 knots in a storm off New Zealand will result in a 24-hour difference in arrival time here in California and a difference of 4 feet in surf face height.

Patch: These large storms off Antarctica that produce massive swells are pretty unique. Generally, how often do we receive southern hemisphere swells?

Collins: On the long-term average we receive about 50 swells a year from storms in the southern hemisphere. Most of those swells create surf of 3 feet on the wave face, 40 percent of those swells are over 5 feet, 10 percent are over 8 feet. This swell is obviously in the top 10 percent and we usually receive about five major overhead southern hemisphere swells a year.

But this swell is definitely at the top of the best swells and will probably be the largest southern hemisphere swell we’ve received in the past few years since the July 2009 swell. Again, most of San Diego County is not exposed to all of the southerly directions like other areas in Southern California, so you may not see as many there.

Patch: When large sets hit one location, are they hitting different areas around the same time?

Collins: Powerful long-crested swells like this one do have sets that arrive at the same time along a few miles of beach. And the swell energy travels in these big patches through the ocean with big lulls in between.

Patch: Besides the Wedge in Newport Beach, what locations in Southern California received the brunt of the swell?

Collins: La Jolla wrapped in it great. And then everywhere from Oceanside up to Huntington Pier was solid. North of there was shadowed behind the Islands (Catalina and Channel Islands). The L.A. County South Bay around El Porto, north to Ventura was also very solid. Malibu was epic Thursday but saw very little of the swell on Wednesday, due to the swell period and island shadowing issues.

— Serge Dedina is the executive director of WiLDCOAST and author of Wild Sea: Eco-Wars and Surf Stories from the Coast of the Californias.

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