MARK SPONSLER SITS in his home office, surrounded by eight computers, studying a spinning pink blob over the North Pacific. He’s looking for a storm—one big enough to send a massive oceanic swell barreling toward the California coast. Ideally, that swell will slam into an underwater ridge a half mile offshore from Pillar Point, creating waves that are 60 feet high. And a handful of lunatics will descend on Northern California to surf them.
This is Mavericks, the notorious break that’s home to some of the heaviest surfable waves in the world. And Sponsler, renowned surf forecaster and founder of Stormsurf.com, is responsible for green-lighting the Titans of Mavericks big-wave competition held just north of Half Moon Bay between November and March. But the contest doesn’t happen every year; waves must be at least 40 feet high and somewhat structured—as in, not exploding with Poseidon’s rage—hard to predict in a winter that could produce one of the strongest El Niños on record. That’s where Sponsler comes in.
Sponsler is a cautious weather scientist and big-wave surfer. (He surfs at Mavericks often but says he draws the line at 40-foot waves. On contest morning, he’ll paddle out with all the competitors and watch just off to the side—the 58-year-old says he’s too old and feeble to “keep up with those madmen.”) Most of his routine forecasts rely on wave models parsed from National Oceanic Atmospheric Administration weather data, but for important events like Titans, Sponsler crunches the numbers by hand. He uses a mix of swell-decay tables—old-school charts that estimate the rate at which swells steadily lose power as they travel through the ocean—and his “secret sauce” of algebraic equations. Finally, he compares his models against readings from the Jason-2 satellite, which measures sea height to within about an inch. (Even so, his models can be thrown off by opposing winds, currents, and other swells.)
Sponsler began forecasting in his native Florida, drawing “rustic and inaccurate” wave models based on satellite photos from his local newspaper. Then, when he was working as a software engineer for NASA’s shuttle program in the ’80s, a colleague changed his forecasting forever. “He said, ‘Come here, I want to show you something,’” Sponsler says. “It was the Internet. I was like, ‘I want this.’”
With access to weather data from across the globe, Sponsler left Florida to hunt waves at Waimea Bay and Sunset Beach in Hawaii—two world-renowned big-wave breaks. Then he heard about Mark Foo’s death at Mavericks. Foo, a legendary Hawaiian big-wave surfer and Sponsler’s acquaintance, drowned after wiping out on a relatively unremarkable 18-foot wave. Sponsler says he thought to himself, “This Mavericks place must be pretty serious.”
Sponsler paddled out for the first time in 1995, with pioneer Jeff Clark, who showed him the ropes. Twenty years later, Sponsler says he has it dialed in. “The game is to paddle out right before the sweet spot, sit there, surf it, taste it like fine wine,” he says. “You learn to pick out the very best barrel in a batch of a whole year’s harvest.”
As for this year’s harvest? Sponsler says this winter is almost guaranteed to produce a number of swells powerful enough to “make the call”—well over 30 if it’s anything like 1997, the last “super El Niño” year. (A swell is essentially a sine wave through the ocean composed of wave after wave.)
Sponsler wants to see a storm that’s at least 1,000 miles offshore, covering 800 nautical miles, with winds in excess of 45 knots, propagating a 15- to 18-second swell period. He says storms typically follow the jet stream and work their way across the North Pacific. “Mavericks is at the end of that pipeline; all the energy is focused right there, in a perfect place to catch the ball when it comes,” he says. But just because the storm’s a-comin’ doesn’t mean Sponsler can stop running the numbers.
“There’s nothing worse than sitting here, it’s contest morning, looking at all the data, going, ‘Where’s my friggin’ swell?’” he says. “That’s my nightmare.”