GMAC at 100ft? The Difficulty of Measuring Waves

DID Garrett McNamara surf a 100ft wave at Nazare yesterday, January 28th, 2013? The jury is out but here are the things we know for certain....

It was an extremely large wave, at first glace it could be 100ft, or it could be 70ft, who knows? It's a decision us wave watching mortals are not qualified to make.

But nestled somewhere in your social feed is a post from a friend saying "Wooaaah check it out, GMAC has finally surfed a 100ft wave." Attached to this puff of enthusiasm will in all likelihood be a Guardian headline claiming such a thing, albeit in inverted commas. The Guardian's source is Surfer Today who said no such thing.

So where could the Guardian have come up with their headline? Somewhere between a lack of understanding of surfing and the difficulty of claim-and-counter-claim over wave height has resulted in them getting a bit confused. To their credit on having been contacted by us and a few other Tweeters they toned the story down a bit. However even after two revisions they are still carrying the unsubstantiated 100ft headline and are referencing their own out-of-date claims of 90ft being surfed back in 2011. That GMAC wave was officially recognised as being 78ft in height by Guinness World Records in May 2012.

This issue of wave height is a problem of perspective, angle and distance the judges at the XXL have to address every year when awarding the tallest wave gong. Bill Sharp, director of the XXL Awards told Grind "The hard part isn't locating the top of the wave, it's finding the bottom of it, because that's the point where you start measuring from.

"The challenge is photos and video can both be deceiving depending on the angle of the shot, the size of the lens used, and even stuff like mist and water color. We should be seeing video of it in the next week or so, and that will be a lot more revealing because it allows us to see where and when the surfer reaches the bottom."

Nazare in Portugal is a spot that is sure to bring more records due to its unique bathymetry. Magicseaweed Forecaster, Ben Freeston explains. "What makes Nazare unique on the shortlist of spots able to handle this sort of swell is constructive interference created by the deep water canyon heading away from the coast. This particular swell peaked at a max height of 28ft on the entrance of the canyon.

"Starting miles out to sea this canyon refracts and bends the offshore swell, and the results go beyond the sort of focussing we see at a world class deepwater reef like Mavericks or Jaws. The effect is the same as two 20ft swells arriving in combination, giving that classic shifting combo swell a-frame shape and creating the colossal waves we saw ridden yesterday."

Certainly it is a huge wave. Perhaps it is over 100ft? Good luck to anyone able to measure it accurately and well done to GMAC for surfing what could be another record-breaker, putting Nazare firmly on the big wave map.