Reading the Seas
How Walter Munk's Wave Prediction Method Helped Prepare for D-Day
Guests visiting Dr. Walter Munk's home may lose track of what they are visiting for, as they are captured not only by the beautiful panoramic ocean view, visible from the backyard, but also the art and memorabilia that fills the home.
Scripps Institution of Oceanography, founded in 1903, specializes in ocean, earth, and atmospheric science research, education, and public service. Munk, a physical oceanographer and Secretary of the Navy/Chief of Naval Operations Oceanography chair member at Scripps, has been working with Scripps for more than 70 years.
"I remember asking my commanding officer about how waves would affect small boat landings during amphibious operations overseas, and him telling me to forget about it because he was sure that the authorities had considered that."
Munk enlisted in the Army in 1939 and was later excused from military service to work on methods to enhance amphibious warfare for the Navy.
"I was 25 with no education and no background, but I just couldn't let go of it. So I called my old colleague Dr. Sverdrup, told him what I thought, and asked him to fly out and meet me in D.C., where I was working at the time," Munk lights up when speaking about his colleague and mentor, Dr. Harald Sverdrup.
"After months of trying to figure out how to predict waves, we were satisfied that it could be done. Harald had a major reputation in the world and they listened to him."
Sverdrup, an oceanographer and meteorologist, was the director of Scripps from 1936 until 1948.
The Sverdrup-Munk wave prediction method aimed to help Allied Forces predict waves, in order to land their troops safely on shore during amphibious invasions and to avoid failed attacks.
"The method tried to help the new types of crafts called Landing Craft, Vehicle, Personnel or "Higgins Boats," that would come on to the shore and drop the bow ramp so that people could run out and establish a beach head," says Munk. "We learned that when the waves exceeded 5-feet in height, the landing crafts would broach parallel to the beach and waves would break into them. This would lead to people getting hurt and the exercises being secured until there were calmer conditions."
The Sverdrup-Munk wave prediction method was first tested in 1942. Their basic swell forecasting scheme was paired with another similar wave prediction method created by Commander Claude Suthons. Suthons provided the British Assault Force with graphs that showed wave height, wave duration, and wave decay rates with wind speed. These methods were paired with aerodynamic and hydrodynamic concepts, which led to the successful invasion of French North Africa during Operation Torch, an American-British invasion during World War II.
"After the success of the landings in North Africa, we were authorized to open up a school for meteorological officers from both the Army and the Navy. We spent a year training 10-12 officers a month, and had 10 classes, so there were over 100 officers. The method we worked on in class is the method generally used now, which is divided into 3 components. The first is to compute the waves in the area, which we call the sea. The second is to estimate what happens when the waves reach their height, or what we call swell. Finally, the third thing we analyze is what happens when the waves come into shallow water, which we call the surf. When the method is applied properly, it is successful," Munk exclaims excitedly.
"Later on, two of the officers who had been in the class here at Scripps, participated in the wave predictions for D-Day," Munk recalls. "I myself did not make the wave predictions."
Charles Bates and John Crowell both had backgrounds in science. Bates graduated from DePaul University with a degree in geophysics, and Crowell from University of California, Los Angeles, with a degree in geology. Bates and Crowell would use the Sverdrup-Munk method along with the Suthons forecasting method to prepare for Operation Overlord.
Operation Overlord, led by General Dwight D. Eisenhower, was the code name for the invasion of Normandy by Allied forces, in German-occupied France, during World War II. It was the largest amphibious assault ever attempted, utilizing 7,000 vessels and 160,000 troops.
The officers used weather and swell data, aerial photographs, and Intel gathered by spending time with amphibious operations units to learn first-hand the capabilities of the crafts being used to properly plan for Normandy.
Munk learned of the events that took place during Operation Overlord from declassified information and speaking with Bates and Crowell.
"On June 5, 1944, when the operation was supposed to take place, there were very high winds, and Eisenhower made the decision to wait 24 hours," Munk explains. "However, 24 hours later, the Americans predicted it was still too risky."
"Eisenhower would still go ahead and proceed with the operation. In hindsight, we learned later that the Nazis wave prediction method was more accurate. They thought it would be too dangerous for Allied forces to attempt a landing. The German's assumption and the chance Eisenhower took, helped preserve the element of surprise that the Allies needed for a successful landing on the beach," Munk says, smiling again.
Although Munk was not directly involved with the wave predictions for D-Day, his work with the Navy and the United States would extend far beyond Operation Overlord.
"After the war, I tried to focus on other things besides wave predictions, but the waves kept calling to me," Munk says smiling.
In 1946, Munk helped with testing nuclear weapons in the Pacific Ocean. In 1968 he became a member of JASON, an independent group of scientists which advises the American government. Amongst his many awards, Munk was awarded the Maurice Ewing Medal sponsored by the American Geophysical Union and the Navy in 1976.
Munk has worked with the Office of Naval Research's (ONR) for 50 years analyzing long-range acoustics, acoustic propagation and wave studies. ONR appreciated Munk's work so much, they founded the Walter Munk Award, which is given annually to a scientist or researcher in the oceanography field, in 1993. The first recipient was Walter Munk himself.
At the age of 96, Munk has no sign of letting up, saying that he will continue to work as long as he can to help the Navy achieve their goals at sea.
"To my knowledge, we hadn't used wave predications for amphibious operations before World War II, but I'm glad to see how far we have come since," says Munk.