The Bering Sea west of Alaska hosted a whopping storm system over the weekend, with sustained winds equivalent to a Category 1 hurricane and gusts up to 115 mph.

Having dropped 49 millibars between Saturday and Sunday, the incredible Aleutian cyclone constitutes a meteorological “bomb” — a storm that drops at least 24 millibars in 24 hours — more than twice over.

Early Sunday morning, the storm’s central pressure finally bottomed out at 924 millibars, tying the record for lowest wintertime pressure in the North Pacific Ocean since records began in the winter of 1969-1970. The previous strongest storm in this region occurred just one year ago.

Except for those engaged in the meteorological community or maritime professions — merchant marine, military, fishing — these massive storms essentially go unnoticed in the remote and relatively un-populated Arctic and near-Arctic regions. But they are the maritime cyclones of winter, roaring across the Atlantic and Pacific oceans at high latitudes.

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Surface weather analysis from the National Oceanic and Atmospheric Administration (below) reveals a very hurricane-like pressure gradient, shown by the circular brown lines. Cold air (blue arrow) wrapped into the system from the north, west and south, while warm air (red arrow) streamed in primarily from the east.

Along the cold front, cold air undercut warm air, and there were two distinct warm fronts. This happens when the storm deepens so rapidly, the primary warm front gets fractured. The purple frontal boundary is an occluded front — the location where cold and warm fronts merged. Amazingly, the storm is so strong that the occluded front completely wrapped in on itself, creating a logarithmic spiral.

Unlike hurricanes, these large and powerful storms go unnamed. And unlike hurricanes, they derive their energy from an entirely different process. While hurricanes extract heat from the ocean, maritime cyclones create energy by drawing together warm and cold air masses. When the warm air rises and cold air sinks, the kinetic energy of swirling wind is generated. The juxtaposition of warm and cold air is also what powers the polar jet stream — and indeed, maritime cyclones and the jet stream are inextricably linked — the one feeding back upon, and enhancing, the other.

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Conditions on the open sea during one of these huge storms are nearly unimaginable. Waves swell to 30 feet or more and the wind rips spray into the air, such that the distinction between the surface of the ocean and the air above it becomes blurred. In the storm’s warm sector, heavy rain is blown sideways, dropping visibility to near zero.

On the cold northern side, true blizzard conditions prevail in heavy snow and high wind. Ocean spray freezes fast to anything solid, including ship hulls, leading to dangerously thick ice accumulations that hamper sensitive navigation and radio equipment, and alter a ship’s center of gravity.

The image above provides a rare snapshot of the winds near the surface of the ocean inside the storm. These winds are measured by satellite in a technique based on scatterometry, whereby microwave pulses aimed at the ocean are bounced back to the satellite sensor. The degree of scattering increases per increased wave action (ocean roughness), which in turn correlates with wind speed.

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In an area otherwise hidden by thick overcast and precipitation, the satellite measurements reveal an elongated pocket of hurricane-force wind just south of the vortex center, referred to as the “sting jet” in these wintertime ocean storms.

The forecasters at NOAA’s Ocean Prediction Center routinely use scatterometry data to assess the intensity of ocean cyclones and provide crucial maritime warnings.

The previous recordholder: Post-Tropical Typhoon Nuri

During early November 2014, a potent marine cyclone entered the Bering Sea with an astoundingly low pressure of 924 millibars, establishing the wintertime low pressure record for the North Pacific Ocean. Like this month’s Bering Sea storm, the 2014 storm also “bombed out,” undergoing a very rapid drop in central pressure. It, too, had cold and warm fronts that wrapped in on themselves, twisted by the extreme circulation. Satellites also revealed the characteristic pocket of hurricane-force, sustained wind.

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But the 2014 cyclone had vastly different origins. A week earlier, in late October, Super Typhoon Nuri emerged from Japan. As the system pulled away to the north and east, it rapidly weakened, but then came under the influence of a strong wave in the polar jet stream.

Post-tropical Nuri underwent a process of extratropical transition and did so explosively. Nuri got a “second wind” as it tracked north and became an extremely fierce maritime cyclone in the Bering Sea.

The cyclone and its jet stream underwent a feedback process that altered the structure and course of the jet stream over North America, setting up a highly contorted jet stream flow configuration called an omega block. The block, in turn, was tied to the first intense polar air outbreak over central North America. Meanwhile, the West Coast and Alaska roasted under a wintertime heat wave.

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In the case of this weekend’s storm, there was no predecessor typhoon; multiple waves in the jet stream phased together, leading to a rapid drop in pressure.

The comparison of these oceanic titans, while both extreme, reveals the under-appreciated nature of wintertime, marine cyclones.  It’s interesting how these storms can emerge from vastly different circumstances. They can also foster seemingly disconnected, high impact weather thousands of miles downstream, including persistent cold and warm spells. And without satellite technology such as scatterometry, much of the real identity of these maritime monsters would still be unknown.

This post has been updated to include the full pressure drop of 49 millibars from Saturday to Sunday.

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