Predicting waves and wars with Walter Munk

My friend Joe and I are standing at the edge of the water on Coronado’s Central Beach. He’s a surfer. I’m a body surfer.

“So do waves come in batches?” I ask him. “Can you predict when the big ones are coming?”

“So they say,” he says.

This gets me thinking, back to an interview I did with Walter Munk, who died a couple of months ago at age 101. Munk was San Diego’s most famous oceanographer. The New York Times called him the “Einstein of the Oceans,” and the moniker stuck, despite his annoyance at it.

Scripps Institution of Oceanography’s reputation owes a lot to him. And guess what one of his most famous studies was? How to predict waves. A big deal, because this was back in World War Two. And the military, which was planning D-Day, needed to know exactly when to land 100s of thousands of troops as safely as possible.

I met him at his low, hilltop ranch ocean view home, “Seiche” (“Sinking water”) right up the road from Scripps. He was in his office-living room with huge views out over the Pacific, working away at a research paper. This sprightly man with lots of hair was 100 years old.

Ahead of a zillion questions, I had to know: Can a surfer predict waves?

“Surfers today have gone a thousand times beyond [our predictive abilities],” he started. But that’s exactly what he spent his time trying to do to help win the war. “Hal Sverdrup (Scripps’ director) and I worked for months in the Pentagon. And nobody had ever done any wave predictions. I’m quite confident of that. And we examined the ways of doing it. And we thought of dividing it into sea, swell, and surf. Sea being the dimensions when the waves come out of the storm area, swell being what is left of it when they get to a distant landing beach. And surf takes into account the very major modifications when waves come into shallow water.”

“And Sverdrup was satisfied by my [work showing] that one can do a useful forecast. And indeed our student graduates went on to predict the many landings in the Pacific Theater of war. And two of our students did the predictions for the landings in Normandy.”

Many say that it was these accurate predictions that allowed the Normandy invasion to succeed, and started the final unraveling of Nazi Germany.

So, from San Diego’s own Einstein, the man who discovered wave patterns, can you predict waves? Do they arrive in groups of say five…?

“No! That is a gross simplification. The number of waves per group is of the order as the distance of the storm area divided by the diameter of the storm area. The diameter of the storm area is called the fetch. The fetch is the distance over which the waves are generated. The total distance [breadth] of the storm. If the storm is seven diameters away, you’d expect something like seven waves per group. In other words, if the fetch is 1000 kilometers [wide], and you are 7000 kilometers away, you might expect [groupings like that].”

“So?” says Joe, after I’ve told him all this.

“That’s a maybe,” I say.