Sunday's forecast calls for a series of substantial waves to surge down Pacific Coast Highway near the Huntington Beach Pier.

The first swell is expected to hit the fabled coastline at 6:30 a.m. and successive swells are to follow over the next hour and a half. But not to worry: The incremental swells are made up of a sea of humanity.

Twenty thousand runners are signed up to participate in the 2012 Surf City USA Marathon, known as the largest combined oceanfront marathon and half-marathon event in the state, according to General Manager Amy Tomchak.

Race spots were sold out for this year's event by Jan. 5, the earliest sell-out yet for the marathon.

Tomchak said the races, held each Super Bowl Sunday, will draw competitors from all 50 states plus 18 other countries.

"We've almost doubled our out-of-state participants in the last couple of years," said Tomchak, who is in her eighth year as general manager. "When I first got started with the event, we had 5,000 participants in 2005. In 2006, that list grew to 10,000 and it continued to take off. This is the third year that we've had 20,000 for this event."

Tomchak said a "very specific" marketing strategy was used to draw more out-of-state competitors.

"We focused on programs with local hotels in Huntington Beach to really attract runners," she said. "We picked out all the key markets — Boston, New York, Chicago, Arizona, Seattle. This year, we are up to almost 3,000 out-of-state competitors.

"We also reached out to participants to get their feedback on what they liked and what they would like to see improve with the event. I think our success is all about staying focused on creating an experience that inspires runners, making sure every detail is made to bring about a perfect experience. We do this from the finisher medals, to through the medical stations along the course. We listed to what the runners needed."

One key aspect of Sunday's event is that the races will be staged in "wave starts" — 19 of them, to be exact. Tomchak said between 1,000 and 2,000 runners will be released at a single time in two- to three-minute starts.

"It's really important that we do that," she said. "The goal has been to make sure that runners don't feel crowded. We also want to make sure that there is enough space for parking. Again, it's all about creating a great experience for the competitors. Setting runners out in 'waves' is so key to doing that."

Race day Sunday begins with the full marathon, which is scheduled to start with the first of four wave starts at 6:30 a.m. The half marathon follows at 7:45 a.m. starting with the first of 15 wave starts. Races start on PCH at Huntington Street in front of the Hilton Waterfront Beach Resort. The finish line is approximately 300 yards north of the starting point on PCH.

The top male and female finishers in the marathon and half marathon will receive commemorative awards, and age division winners also will receive special recognition.

The full and half marathons are USA Track & Field certified, and the full marathon is an official qualifier to the Boston Marathon on April 16. Last year, Gilbert Salazar of Long Beach and Beth Woodward of Orrville, Ohio, won the full marathon. Jimmy Grabow of Long Beach and Cheryl Smith of Laguna Beach won the half marathon. Salazar is the lone returning champion this year, Tomchak said.

Preceding the races is a two-day California Lifestyle Expo, which runs between 3 and 7 p.m. Friday and between 9 a.m. and 6 p.m. Saturday. The expo will be held at the beach parking lot located across the street from the Hilton Waterfront Beach Resort.

The one-mile event has been eliminated from this year's marathon. A five-kilometer race was also cut last year.

"The focus is on distance runners," Tomchak said. "We're working to do the Surf City Beach Derby next October for short-distance runners. We did a trial run with that late last year."

The Surf City USA Marathon is part of the Beach Cities Challenge that includes two other Southern California marathons, the Orange County Marathon (May 6) and Long Beach International City Bank Marathon (Oct. 7). Runners who complete either a half or full marathon at each of the three events receive a Beach Cities Challenge medal.

michael.sciacca@latimes.com

Twitter: @MikeSciacca

2012 Surf City USA Marathon

Where: Hilton Waterfront Beach Resort, 21100 Pacific Coast Hwy., Huntington Beach

When: California Lifestyle Expo: 3 to 7 p.m. Friday, 9 a.m. to 6 p.m. Saturday; Full Marathon: 6:30 a.m. Sunday; Half Marathon: 7:45 a.m. Sunday

Information: http://www.runsurfcity.com