How Big Is This Wave?


photo: dana edmunds

How big is this wave? That depends. Ask the National Weather Service (which we did), and it’s about 27 feet. Ask a longtime Hawaii surfer (which we also did), and it’s more like 18 feet.

The discrepancy comes from dueling approaches used in Hawaii to measure wave heights. The Weather Service measures waves from the lowest point, the trough, to the highest point, the crest. That’s the scientific way of doing it. However, many Hawaii surfers use the time-honored Hawaiian scale, which underestimates heights in comparison to the trough-to-crest method. We asked Pat Caldwell, who is both a longtime Hawaii surfer and a surf forecaster with the National Weather Service (OK, he’s our Weather Service source and our longtime Hawaii surfer source), to explain how Hawaiian scale works. “Well, you just know,” he says. “It’s a learned art from season after season, year after year, watching episode after episode rise and fall, and absorbing the shared communication on the coconut wireless as to how big it was.”

The surfer in the yellow shirt, by the way, is big-wave surfer Keone Downing, who goes by the Hawaiian scale, the smaller number: “Better to call it smaller, don’t psych yourself out,” He says. Also, he says the Hawaiian scale isn’t a measurement of the back of the wave—the common misconception. “How dumb are we? We don’t surf the back of the wave.”