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Computer model projected 10 mb geopotential heights (dam; contours) across the Northern Hemisphere for Jan. 2 through Jan. 18. Credit: GFS model via Judah Cohen/AER Verisk

Scientists are seeing signs that global weather patterns toward the latter half of January and into February may shift significantly to usher in severe winter weather for parts of the U.S. and Europe.

How it works: The possible changes are being triggered by a sudden and drastic warming of the air in the stratosphere, some 100,000 feet above the Arctic, and by a resulting disruption of the polar vortex — an area of low pressure at high altitudes near the pole that, when disrupted, can wobble like a spinning top and send cold air to the south. In this case, it could split into three pieces, and those pieces would determine who gets hit the hardest.

The big picture: Studies show that what happens in the Arctic does not stay in the Arctic, and rapid Arctic warming may paradoxically be leading to more frequent cold weather outbreaks in Europe, Asia and North America, particularly later in the winter.

During the past 2 weeks, a sudden stratospheric warming event has taken place, showing up first in the Siberian Arctic, and then spreading over the North Pole.

  • Such events occur when large atmospheric waves surge beyond the troposphere and into the layer of air above it. Such a vertical transport of energy can rapidly warm the stratosphere, and set in motion a chain reaction that disrupts the stratospheric polar vortex.
  • Sudden stratospheric warming events are known to affect the weather in the U.S. and Europe on a time delay — typically on the order of a week to several weeks later, and their effects may persist for more than a month.

"In general, we see colder than normal temperatures over much of the U.S. and Europe/Northern Asia, and warmer than normal temperatures over Greenland and subtropical Africa/Asia" in the 60 days following sudden stratospheric warming events, Amy Butler, a research scientist at the Cooperative Institute for Research in Environmental Sciences, told Axios in an email.

What's next: Polar vortex projections show it's likely to split into possibly as many as 3 "sister vortices," spilling cold air out of the Arctic and concentrating it in spots across Eurasia and North America.

  • In the past, polar vortex splits have been associated with major snowstorms, including 2010, when the Mid-Atlantic region was buried by blizzards.
  • A sudden stratospheric warming event and polar vortex disruption was associated with several March snowstorms in the Northeast last winter, as well as the "Beast from the East" cold spell in Europe.
  • Such events can have major ramifications for energy markets, leading to natural gas price spikes, for example.

What they're saying: “Arctic change has increased the frequency of these polar vortex disruption events and following these polar vortex disruption events you get more severe winter weather," says Judah Cohen, director of seasonal forecasting at AER, a Verisk company, who studies the connections between Arctic climate change and altered weather patterns.

  • Cohen and Michael Ventrice, a meteorologist at The Weather Company, told Axios that there are increasing signs of high pressure forming over the North Atlantic near Greenland as well as close to the North Pole in late January, which can block the progress of weather systems moving from west to east.
  • Such blocking patterns may be a manifestation of the polar vortex disruption, and favor colder and stormier weather in the eastern U.S. and parts of Europe.
  • “Eventually we do think this blocking will set up,” Ventrice said. “I would not give up on winter.”

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An underwater view of swimmers including Team USA's Caeleb Dressel (R) in the final of the Olympic Tokyo Games men's 100m freestyle on July 29. Photo: François-Xavier Marit/AFP via Getty Images

There's been plenty of Olympics drama on day six of the Tokyo Games Thursday — notably China's women's swimming team beating the U.S. and Australia in the record-setting 4x200-meter freestyle relay.

The big picture: Katie Ledecky helped the U.S. win silver, which also beat the previous world record smashed by China's team. Team USA grabbed two more swimming gold medals, when Caeleb Dressel won the men's 100m freestyle and Bobby Finke triumphed in the first men's Olympic 800m freestyle.

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Junxuan Yang, Muhan Tang, Yufei Zhang and Bingjie Li of Team China react after winning the gold medal in the women's 4 x 200m freestyle relay final. Photo: Al Bello/Getty Images

China grabbed Olympic gold in the women's 4x200m freestyle relay, in a surprise record win in Tokyo Thursday.

The big picture: Katie Ledecky made up time as Team USA's final swimmer to help the U.S. take silver. Australia, which was the heavy favorite, won the bronze. All three teams finished ahead of the previous world record pace.