Once considered a sailor’s tale, scientists say rogue waves are more common than thought
Don’t tell Fran Murray there’s no such thing as a rogue wave.
Murray, of Rockville Center, N.Y., was cruising home with his family this past July after a weekend in Newport, R.I., when his 46-foot Sea Ray literally went airborne off an 8- to 12-foot rogue wave.
The weather was sloppy and rainy, with seas 2 to 4 feet. (Technically, a rogue wave is any wave more than twice the height of the average for the sea state.) “We weren’t going fast — 16 to 18 knots,” Murray recalls. He was at the helm punching a waypoint into his chart plotter east of Point Judith, R.I., when suddenly his wife, Barbara, screamed. Murray had just enough time to see that he had turned into an enormous wave rolling in off the port bow.
“We went up it and were completely airborne, then slammed down,” Murray says. “Straight down. There was no back to the wave.”
The Sea Ray plunged deep into the water and popped back up like a cork, its hull rising clear of the water again and falling back down hard a second time. Below, his 23-year-old daughter, Deidre, and 19-year-old son, Terrance, were asleep in their bunks. “They went up in the air, saw each other suspended,” Murray says, then came down — hard.
Off the Murrays’ stern, the crew of one of the boats they were cruising with witnessed the Sea Ray launch off the wave. “They said the entire boat was out of the water,” Murray says. “They could see the props.”
Then it disappeared behind a wall of water. “They thought, The Murrays are dead,” he says.
When the boat fell off the wave, it knocked both engines off their rear mounts. A shaft started to fall out later in the trip, disabling an engine and leaving the Murrays to limp slowly home to their Greenport, N.Y., marina on one power plant. The encounter left a long crack in the hull’s starboard side and popped the television cabinet out of the overhead.
“It’s a mess,” Murray says.
Rogue waves are real. Even scientists are reaching consensus on that. A study of satellite photos of the world’s oceans has produced irrefutable evidence of the existence of rogue, or “monster,” waves and in far larger numbers than scientists previously thought.
“Before, this was not accepted as a true science — study of freak waves or rogue waves,” says Wolfgang Rosenthal, senior scientist at the GKSS Research Center in Geesthacht, Germany.
Though mariners long have known of the existence and danger of rogue waves, skeptical scientists often debunked reports of waves the size of 10- story buildings as wildly exaggerated. “They automatically were put in the box of [sightings by] a drunken sailor,” Rosenthal says.
Mathematical models suggested these freak monster waves occur only once every 10,000 years in any given locale in the open ocean.
MaxWave, a three-week project in August and September 2001, tasked the European Space Agency satellites ERS-1 and ERS-2 with monitoring the oceans by radar. The satellites sent back 30,000 “imagettes,” or pictures, of 6-by-2.5-mile swaths of sea surface, taken every 120 miles and covering all the oceans.
Rosenthal and his researchers pored over the photos, and in July reported 10 waves measuring more than 81 feet tall from that limited sampling. “We found more monster waves, more rogue waves, than we had expected,” says Susanne Lehner, associate professor at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. Rosenthal says the MaxWave project has opened the door to a new research direction. “In the next few years, we will find out a lot more about these singular waves,” he says.
The European scientists are looking at rogue waves because of the danger they represent to worldwide shipping. The ESA reports an estimated 200 ships larger than 650 feet have sunk over two decades, with the loss of many lives. These losses typically are attributed to “severe weather.” Scientists now believe many could be due to run-ins with rogue waves.
“The letters I receive [from mariners] say, ‘I encountered waves like that,’ ” Rosenthal says. He says it’s time scientists tried to find out enough about them to warn mariners when they might be coming.
ESA says a Jan. 1, 1995, wave measured at 85 feet by an on-board laser device broke over the Draupner oil rig in the North Sea, while waves around it averaged 39 feet. Radar data from the North Sea’s Goma oil field recorded 466 rogue waves over 12 years, helping persuade skeptics to look more closely at the phenomenon.
Around the time satellites were collecting data for MaxWave, 100-foot monster waves in the South Atlantic smashed into two tourist ships, Bremen and Caledonia Star, breaking out their bridge windows and leaving the Bremen without navigation or propulsion for two hours.
ESA has archived 12 years of satellite radar images of the oceans. In a new project, WaveAtlas, researcher Lehner plans to analyze two years’ worth of those images and create a worldwide atlas of rogue wave events, along with statistical analyses of significant wave heights for different seasons. As scientists get a clearer picture of the weather conditions that spawn these waves, rogue-wave forecasts may be possible, she says. She also hopes to see realtime satellite radar data become available to forecasters so they can make rogue wave predictions.
Scientists aren’t exactly sure how rogue waves form, but they theorize there might be several ways. For example, a wave running headlong into a current can become a rogue. The current slows the wave, compressing it, building its height and giving it a steep face. Killer rogues seem to spawn off Africa’s Cape of Good Hope and South America’s Cape Horn, usually when a storm off Antarctica sends huge swells booming up toward the capes to meet fast currents.
Rogues also can develop behind islands and shoals. They refract around the obstacle and come back together on its back side in a confused sea. If the waves converge behind it in phase — with troughs and crests lined up — they merge into a new wave as high as their combined heights. In open ocean, disturbances in the wind field can create crossing seas and waves that, when they meet in phase and at the optimum angle, merge into a rogue. Rosenthal says fast-moving storms exceeding 12 hours also may build up a rogue wave when it runs at an optimum speed in sync with the wind over a long distance.
MaxWave researchers found the largest concentration of rogues between Cape Horn and the Cape of Good Hope, as one would expect, in August and September — winter in the Southern Ocean.
The biggest rogue wave recorded is a 115-footer, reported by the U.S. Navy ship Ramapo in 1933 in the Pacific. In 1942 a rogue wave nearly capsized the passenger ship Queen Mary during a storm 700 miles off Scotland as it transported 15,000 soldiers to England. Fiftythree years later on Sept. 11, 1995, Cunard Lines’ Queen Elizabeth 2 survived a 95-foot rogue in the Atlantic during Hurricane Luis. It rose more than twice the height of the storm’s 40-foot waves.
Rosenthal says MaxWave’s finding that rogues are more common than once thought could result in stiffer standards for oceangoing ships. He says the International Maritime Organization already has required stouter hatches on ships. “They were a little bit weak for the load of water that rushes on deck if a freak wave encounters a ship,” he says.
That’s further evidence that rogues finally are being taken seriously.more monster waves in the world’s oceans than scientists had expected.