Hurricane Dorian likely whipped up a 100-foot rogue wave near Newfoundland

While Dorian was pulling away from the United States Saturday night, parts of the Canadian Maratimes were getting battered with 100 mph wind gusts. But Dorian’s most terrifying feat in Canada may not have struck on land. Dorian whipped up a hundred-foot rogue wave.

A buoy owned and operated by the Marine Institute at Memorial University of Newfoundland recorded the monster wave Saturday night, while winds gusting above 60 mph struck the area. Three other waves topped 75 feet.

A 100-foot wave is taller than an eight-floor office building.

Readings like this are virtually unheard of, for obvious reasons. But Bill Carter, director for the Center of Applied Ocean Technology at the Marine Institute, confirms the buoy was calibrated and operating correctly.

“I make sure the equipment’s working, which it was,” said Carter. He explained that the hundred-foot figure indeed measures an individual wave crest to trough.

“Only ten minutes of the data from every hour is sent back to shore,” said Carter, citing costs for telemetering the data wirelessly to land. “There could have been even higher waves during the other fifty minutes. We’ll only know when we get the data off the buoy.”

Winds at the time were rough, but not terribly ferocious. They were clocked as high as 66.2 mph, although there’s a more than 80% chance they gusted higher, since we only “see” ten minutes’ worth of data from every hour.

The rogue wave occurred within the storm’s dry slot, meaning it wasn’t even raining. But a developing sting jet upwind likely added to the force of the winds to the west, agitating the sea state in the vicinity even more.

The buoy, moored two miles offshore, sits in about 160 feet of water normally. That’s not very deep, especially for a shallow-water wave to reach 100 feet. However, theoretical maximum height to depth ratios have been demonstrably proven in the past to range between 0.55 and 0.8, meaning that an 88 to 125 foot wave is possible. The upper bounds were extremely difficult to simulate under laboratory circumstances, but it indicates a hundred-foot wave is certainly not out of the realm of possibilities.

Brian Walsh is a meteorologist at PAL Aerospace in St. John’s. He’s confident the hundred-foot reading is legitimate.

“The fact that there were other reports of 26+ metre (85 foot) maximum wave heights leads me to believe it could be possible,” wrote Walsh.

One additional figure we can turn to is the significant wave height. It’s the average of the tallest one third of all the waves. The National Weather Service Ocean Prediction Center did analyze a small area of 50-foot significant wave heights Saturday night. Individual waves may be twice the significant wave height. Albeit an extremely low-probability event, these top-tier hundred footers wouldn’t be impossible under that scenario.

A number of other stations nearby also reported significant wave heights of 50 feet or more.

However, there are upper bounds as to how open water waves can grow in different environments. Given how relatively close this measurement was recorded to shore, odds are that this wave may have been helped along by two processes: bathymetry and interference.

Bathymetry describes the slope, topography, and elevation of the sea floor/continental shelf. That can have a role in forcing waves to ride upwards, causing waves to diffract, or otherwise affecting the propagation of waves.

“The Cabot Straits bathymetry is varied, with the Laurentian Channel creating a deep trench through its centre,” explained Walsh, “and comparatively shallow coastal waters closer to Newfoundland and Cape Breton Island.” While these conditions are impossible to validate, Walsh says that these conditions have been known to foster the development of these rare rogue waves before.

Interference could play a role as well. That means that several ordinary waves may have combined constructively, their amplitudes piggybacking to form one mammoth wave. Research has shown that waves intercepting one another at an angle can have this effect, with the “sweet spot” of a 120 degree intersection achieving the tallest waves.

Rogue waves have been the subject of folklore and fascination for years. It has long been rumored that a mythical – albeit possible – string of three rogue waves dubbed the “three sisters” abruptly swallowed the SS Edmund Fitzgerald during a storm on Lake Superior on November 10, 1975. All twenty-nine crew aboard perished, the ship vanishing at first without a trace. The cause of the disaster is still not known.

Rogue waves largely remained an old sailors’ tale until 1995, when what was before legend suddenly was proven a scientific reality. An oil rig in the North Sea off the coast of Norway was suddenly broadsided by an 84 foot wave on New Year’s Day, 1995. It was dubbed the “Draupner Wave,” since it slammed the Draupner E drilling platform owned by Statoil.

What happened Saturday night off of Newfoundland? We may never know for sure. But one thing is certain.

We’re going to need a bigger boat.