In Hawaii Surfers are waiting for that giant wave

d ~ 133'785'600 km: day 52

On the other side of the planet, surfers are waiting. Fortunately, Hawaii isn't such a bad place to wait, being home to "the most beautiful beach in the world", luaus, very blue water, and more pineapples than you can shake a cocktail stick at. It is currently the season for big waves in Hawaii, but those keen to risk their lives on the biggest waves of them all like what was expected to kick start the Eddie Aikau competition in Waimea Bay Hawaii rely on the conditions being just right.

Why Hawaii? Is this just an excuse for an exotic holiday? You can surf in lots of places, but these isolated islands win the prize for some of the biggest waves on the planet because of two things. They're in the right place to intercept the huge swells crossing the Pacific Ocean, and they're the right shape not to waste any of the energy heading their way. I suppose that sunny warm islands are good for surfer street cred (can you imagine the Beach Boys in Alaska instead of California?), but it turns out that's just a convenient coincidence.

It all starts with a big storm in the north Pacific. Waves grow in storms because the water surface is pushed along by the wind. You can see ripples form if you blow sideways on the top of a cup of tea, and Ocean waves start in the same way.

If the wind keeps pushing on the waves, they keep growing. But storms make complicated choppy waves, terrible for surfing on. This is why it's so important that Hawaii is far out in the middle of a very deep ocean. As the newly-formed waves race away from the storm, a sorting process happens. Waves with a long wavelength (a long distance from one peak to the next) travel more quickly than waves with short wavelengths. They can also travel further before they give up their energy. Storm waves can travel thousands of miles, and after such a long journey, the nasty messy choppy water has turned into smooth long tidy swells.

Our cool surfer dudes (who are still waiting) are actually waxing their surfboards close to the top of a huge mountain. If they could see for miles underwater, they'd probably have vertigo. Most of the Pacific ocean is about 5 km deep and the seafloor is fairly flat. The Hawaiian islands are tall volcanoes sticking up out of this vast plain. And this is the other reason that Hawaii gets big waves. Shallow water weakens waves, but this isn't a problem in Hawaii. These ocean swells reach the shore with most of their energy intact. If the right combination of conditions occurs, the waves breaking on the north shore of O'ahu can be 20 metres high. When the surfers finally catch their giant wave, they're surfing on moving energy from a storm that happened two thousand miles away, and 1-2 days previously. It sounds amazing, but I think I'll stick to watching.

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