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By Amanda Greenwood
Associate News Editor
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An unusually early disruption of the polar vortex could shake up weather patterns across the United States in the coming weeks, potentially opening the door to outbreaks of Arctic air as the country heads toward winter.
Forecast models “indicate the potential for a stratospheric polar vortex disruption,” potentially developing into a “sudden stratospheric warming” event, which would be "very rare" for November, the National Weather Service Climate Prediction Center (CPC) said in its updated November outlook.
During a sudden stratospheric warming (SSW), the air high above the Arctic rapidly heats up and the strong winds that usually circle the pole weaken, or can even start blowing in the opposite direction. NOAA research says that in particularly dramatic cases, stratospheric temperatures can rise by 40°C to 50°C within days.
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The warming high above the Arctic can disrupt the winds that normally keep the coldest air near the pole, making it easier for cold Arctic air lower in the atmosphere to move south toward the U.S.
While the development can’t guarantee that there’ll be a major cold snap in the U.S., the disruption of the vortex can quickly change weather patterns in ways that make outbreaks of unusually cold air at lower latitudes more likely.
What Is the Polar Vortex?
The Arctic polar vortex is a band of westerly winds that forms roughly 10 to 30 miles above the North Pole, high in the atmosphere (or stratosphere) during winter, trapping a large area of extremely cold air around the Arctic. So when those winds are strong and stable, they help keep the cold air concentrated around the Arctic, limiting how much of it can move south toward the U.S.
"As this system weakens, some of the cold, Arctic air can break off and migrate south, bringing plenty of cold air with it," NOAA's National Environmental Satellite, Data, and Information Service explains. In some circumstances, Arctic weather can reach as far south as Florida.
Research involving NOAA scientists similarly finds that a weakened stratospheric polar vortex can allow pockets of cold air to plunge much farther south than normal, although predicting precisely when and where that happens remains challenging.
When Could the Cold Air Arrive?
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Don’t reach for your hat, gloves, and scarf just yet. Any significant impact on U.S. temperatures isn’t necessarily immediate.
In its update for November, the CPC said that its forecast models indicated a possible sudden stratospheric warming during the first week in November. If the disruption occurs, its effects could last for up to two months, potentially changing weather patterns to make it easier for cold Arctic air to move south toward the U.S.
That makes late November and potentially December the period to watch for changes in U.S. weather patterns.
There are already hints of where a pattern change could develop.
The CPC said there is "some potential for troughing to settle over the Southeast by the end of the month," which means weather patterns could shift toward cooler conditions across parts of the Southeast toward the end of November, although forecast models remain uncertain about its placement and strength.
The agency also said the ongoing El Niño is expected to remain the dominant large-scale climate influence, with the potential polar vortex disruption adding uncertainty to the forecast, particularly for the eastern United States.
For now, the developing disruption should be seen as a possibility that there might be a colder snap in the U.S. later in November or into December, rather than guaranteeing a widespread Arctic outbreak.
Newsweek has contacted the CPC for comment.
Newsweek’s reporters and editors used Martyn, our AI assistant, to produce this story. Learn more about Martyn here.
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