In February 1933, on its way from San Diego to Manila, the US Navy ship Ramapo was caught in the teeth of a relentless storm. The wind had slowly gathered momentum across thousands of nautical miles of the open Pacific, piling up monstrous swells: twenty feet, then thirty, then higher. On the seventh day of the storm, with the east wind howling at sixty knots, the swells grew to an average of fifty feet. Every fifteen seconds a new behemoth — large as a five-story office building — shouldered its way into the stern.

In the deep night of February 7 — around 3 am — the clouds parted, and for a moment the clear, glittering moon could be seen from the deck. The sea came alive with reflected light: splashing, roaring, tumbling. And the watch officer on the bridge glimpsed an oncoming wave: vastly larger than the rest, rushing toward them at fifty knots from astern.

The wave seemed to gather the surrounding seas into itself, into a great shadow of turbulent water. It caught the ship from behind, lifted its stern toward a towering crest, and plunged the bow into a deep, black trough. The entire length of the Ramapo — almost five-hundred feet — lay steeply along the face of the wave. The watch officer looked to the stern — buried in the wave’s crest — and to the bow — plunging and spuming in the trough. He kept his wits, and noted that the ship’s crow’s nest — amidships, ahead of where he was standing — was precisely horizontal to his line of sight. This observation enabled subsequent calculations which showed the height of the wave to have been 34 metres (112 feet). It was 350 metres long (more than a thousand feet), with a potential energy equivalent to about 17,000 kilowatts per metre — more power than the world’s largest hydroelectric dam (the Itaipu dam, on the border of Brazil and Paraguay).

It was not a tidal wave, a tsunami created by seismic events, but a storm wave generated by wind, current, and the mathematics of distance. A rogue that arose suddenly from the surrounding swells, as such waves do, and grew to twice the size of its neighbors. It climbed from the dynamic chaos of the sea, bore down on the ship, and raced onward.

The Ramapo was extraordinarily lucky. If the ship had been shorter, by perhaps as little as fifty feet, it would have slid down the face of the wave, hit the well of the trough at significant speed, and would likely have pitch-poled into a fatal capsize. A small craft — a yacht, say, or a fishing boat — would simply have been crushed by the wave’s crest, which exerted something like one ton of water pressure per square foot (possibly a great deal more, if recent research predicting one-hundred tons of pressure is accurate). Conversely, a ship longer than the Ramapo would have taken the crest of the wave over the bow or stern. The water would have burst the deck open and flooded the interior. This is what happened to the Derbyshire, a thousand-foot long British bulk carrier sunk by a rogue off the coast of Japan in 1980. The Derbyshire’s front hatch buckled and the ship went down, taking all 44 of its crew, in under a minute.

But the size of the wave that overtook the Ramapo, its angle of approach, and the size of the ship itself, all conjoined perfectly. The ship fit neatly into half the wavelength of the rogue, and was allowed to pass. This synchronicity of factors allowed the captain and his crew to reach Manila, and subsequently to relate the tale of what is still the largest reliably recorded wave: high as an eleven-story building, wide and long as a shopping mall. A monster wave.

It’s worth noting that eight years after its encounter with the rogue wave, the Ramapo was moored in Pearl Harbor on the morning of the Japanese attack. The ship was lucky again that day: a bomb fell into the sea a dozen feet from the bow, where a crewman stood firing his pistol at the oncoming planes, tears streaming down his face. The bomb exploded into a great column of water, but the ship was unhurt. And though the Ramapo was at the heart of the action, was one of the first ships to return fire, no crewmen were killed or wounded, and the only damage was from a single, nickel-plated machine-gun bullet that was later pried from the teak base of the aft gun platform.

Five large warships were sunk during the Pearl Harbor attack. This is roughly the number of large ships (over 600 feet) lost every six months on the world’s oceans. Over the last twenty years, more than two-hundred large ships have gone down. And until recently, most of these sinkings were attributed simply to “bad weather.” But at the end of 2003, the results of a European Space Agency research project demonstrated what mariners have claimed for centuries: that rogue waves likely account for a large number of ocean disasters.

The MaxWave project utilized ERS (Earth Remote Sensing) satellites to sweep the ocean’s surface — through daylight, darkness and cloud — for three weeks. The sensors collected 30,000 radar images of 5 by10 kilometre swaths of the sea, with a resolution of ten metres, every 200 kilometres. The images were then processed at the German Aerospace Centre, and showed at least ten individual waves more than 25 metres (81 feet) in height. But the satellite survey was only a snapshot: each satellite recorded a radar image, skipped over 200 kilometres, then took another image. As such, the survey did not show all the rogue waves around the globe at a given time. That number would be much higher. A radar survey from the Goma oil platform in the North Sea, for example, showed almost a rogue per week in the vicinity of the rig. And the North Sea is not known for rogues.

Most large ships and oil rigs are built to withstand 15 metre (about 50 foot) waves. An encounter between a container ship or an oil rig and a 25-metre wave is thus a potentially deadly scenario. Indeed, a 26-metre rogue wave was the principal cause of the capsize of the Ocean Ranger, a drilling rig that sank off the coast of Newfoundland in 1982. The Ocean Ranger catastrophe was the worst marine disaster in Canada since the Second World War. 84 lives were lost. A Soviet container ship, the Mekhanik Tarasov, also went down in the same storm, with a loss of 33 lives.

No one is sure what causes rogue waves. Strong winds and open water are factors, as are ocean currents: like the Agulhas, off the east coast of South Africa, the Atlantic’s Gulf Stream, and much of the Southern Ocean (north of Antarctica, south of Africa and South America) where the path of the ocean is unimpeded by land all the way around the globe. In 2001, two cruise ships in the Southern Ocean, the Bremen and the Caledonian star, were hit by 30-metre rogues in the same week. Their bridge windows were smashed, and the Bremen was left drifting temporarily, without navigation or propulsion.

In the Pacific, rogues seem to occur most frequently along the path of the Kuro Siwo (‘blue salt’) current. It runs off the east coast of Japan, and continues in a northeasterly direction to about 40 degrees north and 160 degrees east. Rogues also appear off the coasts of Oregon (where lighthouse beacons have been hit by 30-metre waves), British Columbia, and Alaska.

The National Data Buoy Center, part of the National Oceanic and Atmospheric Administration in the United States, has recorded 20-metre storm swells near the Aleutian Islands. These are not rogues, but simple swells: thousands of them, marching in lockstep across the reach of a storm. Based on calculations of the relationship between swell height and potential rogue height, rogues as high as 50-metres (about 162-feet) have been predicted for the North Pacific. No waves of this height have actually been recorded, but the complex mathematics of wave dynamics suggests that waves may well reach such heights in the most severe storms.

The traditional theory that rogues are a series of waves piled on top of each other — a set of swells that have somehow fallen together — no longer prevails among oceanographers. The current view, which is sketchy at best, involves the action of currents moving opposite to wind direction, and the compression of wavefronts along eddies in the path of a current. Some emerging perspectives employ the Schrodinger Equation of quantum physics and the famous “butterfly effect” of chaos theory, in which small changes in a system create massive results. Various researchers are working on ways to further develop these non-linear ideas. But it’s difficult to study rogue waves: they appear and disappear unpredictably, they move fast, and they are immensely dangerous.

Some extreme surfers try to find and ride rogue waves and colossal reef waves. Projects such as Surfline and WaveAtlas aim to provide accurate meteorological data to assist mariners in finding or avoiding massive waves (finding, in the case of Surfline, and avoiding, in the case of the nascent WaveAtlas). Since rogues tend to be about twice the height of the surrounding seas, one strategy for avoiding them is to stay away from wave conditions that, if doubled, represent a danger to your boat. This corresponds to a redundancy factor of two, a principle in safety engineering. In experiments conducted in the wake of the 1979 Fastnet yacht race disaster, in which 14 sailors were lost, it was found that a 12.5-metre (40-foot) mono-hull yacht could be capsized by a breaking sea as small as 4 metres, or about 13 feet. A wave of this size was a principal cause of the capsizing of the Cap Rouge II off Steveston, BC, in 2002, with five lives lost. The Cap Rouge II was 21 metres long.

Ship design standards are likely to change as rogues are increasingly acknowledged as a major cause of marine disasters. For now, and for the average boater in the Pacific Northwest, the most effective means of avoiding rogues is simply to pay attention to the weather. But weather systems sometimes change quickly, and without warning. When at sea, watch for unusually large waves (and use radar at night, in storms, or in poor visibility). The rogue that destroyed the Ocean Ranger was visible for several minutes before it struck. This would have been enough time for a small vessel to get out of the way. When on the beach, be particularly cautious in conditions of high wind and high tide: people have been snatched from shore by rogues and carried off without a trace.

Terrifying and beautiful and majestic all at once, rogues are archetypes of the mighty and unpredictable character of the sea. They suggest an attitude of extreme caution, possibly even of reverence, in the face of something unfathomable. For many mariners, this is the chief reason for going to sea: to partake of its great mystery. Rogues embody that mystery.