Science of big waves

 

From LiveSciences

The world's best surfers are gearing up for Mavericks International, an elite surf competition that pits big-wave riders against the monster swells at a Northern California Beach.
The competition happens every year in the winter at Pillar Point in Half Moon Bay, Calif., at a time when the waves and weather align.
When the forecast looks good, surfers have just 48-hours to make it to the competition.

Big-wave surfers competing in the Mavericks Invitational can thank Mother Nature for producing 40-foot-high breakers -- and the forecaster who predicted the perfect surf was on its way to Half Moon Bay.
The huge waves are part of the same weather pattern responsible for California's severe drought.
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Waves this year are forecast to reach up to 40 feet (12 meters) tall, with the peaks coming every 18 to 19 seconds, SFGate Reported.
The biggest waves at the competition can sometimes reach 70 feet (21 m) high.

But just why do the waves get so big at this particular time and spot?
[In Photos: Famous Surf Spots Around the World]

Winter storms thousands of miles away over the Pacific Ocean near Alaska provide the energy.
There, a low-pressure front from the north collides with a high-pressure front from the south.
The resulting pressure differential generates strong, fast winds that blow over a vast area of ocean for long periods of time.
This wind energy then transfers to the ocean, where it creates big swells.

The tides also play a role in Maverick's monster waves.
During the transition from high to low tide, wave energy roiling the ocean reaches the seafloor.
This energy has nowhere to go but up, increasing the wave's height, according to Bay Nature, a San Francisco-area magazine.

The Weather Channel Storm Surge Expert Michael Lowry explains
the secret behind the huge waves in Northern California's "Mavericks.

But the real magic comes from Half Moon Bay's bizarre geometry.
After all, the beaches nearby don't get the same massive waves.
The crests at Pillar Point, by contrast, can get so big that they register on seismographs miles away.
In 2007, researchers from California State University at Monterey Bay and the National Oceanic and Atmospheric Administration used sound waves to create contour maps of the ocean floor near the competition.
These maps show a ramp that rises sharply, but drops steeply off on either side, creating what the surfers call a launching pad.
When waves come from the right direction, the big ones touch the ocean floor and slow down, then curve into a 'v' that focuses the wave's energy.
With its energy thus focused, the wave quickly jumps in height, and the Big Kahuna is born, KQED's Quest reported.

Links :

• GeoGarage blog : Maverick moments / Surfing Mavericks : aerial footage /