Arctic storm: How bomb cyclone will morph into polar bomb

The tatters of Super Typhoon Nuri battered the Bering Sea and its Aleutian Islands Saturday with historic winds and rains, as the rest of the US braced for the moment when the so-called bomb cyclone transmogrifies into something more like a polar bomb.

Snow could start falling in Montana and the Great Lakes as early as Wednesday, and New York could easily face temperatures 15 degrees below normal by next weekend as Nuri, now downgraded to a mid-latitude storm, forces a heavy wedge of Arctic air deep into the middle of the country and then across the South and East next week.

“This strong low pressure system will cause the jet stream to buckle, creating a ridge in the western United States and solidifying a deep trough in the Eastern US,” writes McCall Vrydaghs, a meteorologist for WHIO TV in Dayton, Ohio, predicting highs rising only into the low 30s for many parts of the country. “Keep in mind, if this same weather pattern were to set-up during the heart of winter, we would be looking at temperatures far lower.”

Indeed, the displaced Arctic air will mark another early attack of cold and snow on an eastern US that has been harangued by long, cold winters for several years, even as other parts of the globe, and even the US, has seen above-normal temps.

And there were few signs of a let-up. Last Saturday, parts of the Appalachian South, including upstate South Carolina, saw significant early snowfalls of the kind that hadn’t been seen in 40 years.

The Farmer’s Almanac has called for an early and cold winter for large parts of the country, but research into another early and thick Siberian snowpack suggests that the winter may hang on, as well, deep into next year.

“There’s a theory that the amount of snow covering Eurasia in October is an indication of how much icy air will sweep down from the Arctic in December and January, pouring over parts of North America, Europe and East Asia,” writes Bloomberg’s Brian Sullivan. “Last year, the snow level across Eurasia was the fourth highest for the month in records going back to 1967. In January, frigid temperatures dubbed ‘the polar vortex’ slid out of the Arctic to freeze large portions of the U.S.”

The storm that remained from Typhoon Nuri on Friday had a central pressure of 924 millibars, according to the NOAA Ocean Prediction Center, making it the most intense storm ever in the wind-whipped Bering Sea.

In 1977, Dutch Harbor, Alaska, recorded the previous low pressure of 925 millibars during another real howler.

A "bomb" as a meteorological term is a drop in a storm's central pressure of more than 24 millibars in 24 hours. What remains of Nuri is expected to drop as much as 50 millibars in 24 hours – arguably a "double bomb." It's that intense low pressure that's going to buckle the jet stream as ex-Nuri bulldozes across the Bering Sea.