The skaters begin their leaps to the music of the British rock group "Wham!" The soundtrack fits. They fall out of spins, trip over toe loops and skid across the ice. There is one, however, who does not fall.

Debi Thomas quite obviously is the favorite in the women's figure skating competition at the National Sports Festival. She is slightly more composed, her jumps are a little higher, the arm movements a little more graceful, the mistakes not as frequent. An 18-year-old from San Jose, she is one of the few among the 3,300 athletes here whose name likely will be emerging over the next three years as a contender for the 1988 Winter Olympics in Calgary.

The second-ranked skater in the United States and fifth in the recent World Championships, Thomas has come to the National Sports Festival, which her more established rival, Tiffany Chin, decided to forgo, to get a little recognition. It will happen quickly, and it already is beginning here. While Chin, who finished fourth at the World Championships, is reaching her peak as a skater, Thomas is just beginning to challenge her, and is improving at a meteoric rate.

"The idea is to sneak up on everybody, and then go, 'Boom!' " said Thomas, already the United States' most successful black skater ever.

She came from behind to lead going into Sunday's long program with a spectacular short program today. She had trailed Caryn Kadavy (who dropped to fourth place after falling on her first combination jump) following the compulsories. Three of the final five women had falls or stumbles on their routines but Thomas had a near-flawless performance.

Thomas' imminent arrival is liable to be sensational because there is nothing of the usual ice princess about her. At 5 feet 7, she is not petite and she likes a little rock and roll with her classical music. Her style combines athletic leaping ability and artistry. She is a powerful jumper and her distinctive spins earned her roars from the crowd today.

She plans to enter Stanford in the fall as a freshman. In between premed classes while preparing for a career as an orthopedic surgeon, she will continue her six-hours-a-day training at the nearby skating rink of her coach, Alex McGowan.

If Thomas is only now being recognized as competition for Chin, it is because her progress has been so startling recently. In four international competitions in the last year, she has placed first in three and second in another. But she never has won a major title in the United States, where she usually has finished second to Chin.

"We're getting close," McGowan says. "She's at that point. This past year was hers."

Thomas was 10 when she began working with McGowan at his Redwood City, Calif., arena. At 12, she placed second in her first national competition, in the novice division.

"That year was a bit of a shock," McGowan said. "I didn't expect her to even qualify, so I booked a trip to Hawaii."

The pattern of unexpected success has continued. In 1983, her first year competing as a senior, she defeated Chin in a Los Angeles event called the Arctic Blade, the last loss the top-ranked skater suffered to a current competitor.

Thomas' most impressive achievement came at the recent World Championships in Tokyo. Her fifth-place finish -- she was third in the freestyle competition -- was the highest by a freshman skater there since Janet Lynn in 1968. Once again, McGowan was surprised.

"I was just trying to get her in the top 10, like sixth or seventh," he said.

Thomas has shocked even herself with her sudden emergence, after eight years of trying to balance skating with her Stanford ambitions.

"I don't think you ever realize it," she said. "You just gradually move up each level, and all of a sudden you're there. You never really know while you're younger because so much can happen. A lot of the kids who are hot shots at 12 aren't there any more. They run out of money, gain too much weight, lose interest.

"You just hang in there. It's more a question of longevity."

The next three years are the crucial ones competitively, which makes accepting her scholarship to Stanford something of a risk. But Thomas plans to take light course loads during the winter and contends college life will be more conducive to training than high school was, since she then had a 45-minute commute to her training site.

"Everybody says it's impossible," she said. "I think it's going to be easier. The surgeon thing is a long way away. Skating is what's important to me for the next three years. I know that to be satisfied when I retire I'm going to have to do everything that I want to do. So, if I want to be fulfilled, I'd better get my act together pretty soon."

This week, Thomas is at a disadvantage in her training. Because of her decision to go to Stanford, she has worked only five weeks in preparation for the Festival, taking a long break after the World Championships to raise her grades. That has led to a little tension between student and coach.

"She's not at her peak," McGowan says, frowning. "If this were the nationals, we would have trained five months."

A little bickering breaks out after the warmup session before the short program because she has gone through her entire routine when he told her not to. "I had to," she said. "I'd freak if I didn't know I could do it."

Thomas' preference for doing things at her own, generally breakneck, speed is McGowan's only complaint against his prize student.

"She's a little stubborn," he said. "Sometimes I ask her to do things she might not want to do. I explain it's for her benefit and she usually comes around, like a normal teen-age kid. It helps her sometimes though, because she's stubborn with herself, and that helps her out there. She's stubborn about being beaten."

The opportunity for publicity made Thomas compete here, despite the chance of upset. McGowan saw an opportunity to steal some of Chin's corner on the recognition market, and also a chance to win corporate sponsor backing, which would help her family with the cost of financing her skating. It also might provide the chance to curry favor with the judges.

"Tiffany is the one to go after," McGowan said, "She has the name. The judges get to know you, get to know your reputation. Sometimes you can make an error, but they want the best field in the finals, so maybe they'll overlook it, compensate in the marks. Whereas if you're unknown, you have to climb the ladder for the recognition."