Why are Northern California surfers so interested in New Zealand storms? In a word: waves. Our windy summers don't make for very good surfing. California's legendary surfing waves are generated by winter storms that roar out of the Gulf of Alaska, crossing 3,000 miles to reach our shores. A good winter may see 25 storm swells. But by late spring, the storms are gone, the surf a memory. The fog rolls in and with it, the dreaded summer surf doldrums.
Luckily, a few times each summer a remarkable phenomenon occurs, delighting surf-starved wave lovers. It's a marvel of wave physics, courtesy of the Pacific Ocean, and here's how it works. While the Northern Hemisphere basks in summer, New Zealanders are hunkered down against Antarctic winter storms. Racing northward across the Tasman Sea, these monsters spawn winds of 70 knots and huge, 40-foot swells. Ten days and 7,000 miles later, their remnants miraculously find their way to our shores as perfect south swells.
Like radio waves, these swells lose only a fraction of their energy in their journey across the vast Pacific. In a neat twist, the water through which they pass barely moves. Each water molecule makes a tight vertical circle and passes on its energy to the next, and so on a million times until the wave reaches shore. There, it encounters a rising seafloor, steepens, and its peak pitches forward to break in a welter of foam. The longer the period -- the distance between two peaks -- the greater the energy. So, a three foot New Zealand swell can create a steady train of eight foot waves.
That's where that chap-lipped, sun-bleached tribe of waterpeople comes in. Rising at dawn, calling in sick, they surf until their muscles turn to rubber and their fingers to popsicles. It doesn't matter. It's a summer south swell: a rare gift to be savored.
So, the next time you overhear your surfer friends, assuming you have such friends, rejoicing about a giant storm off the Ross Ice Shelf, know that in about a week, they may disappear for a few days. Somewhere in the foggy waters off our beautiful coast, they'll be enjoying a firsthand lesson in wave dynamics.