10
Loading video...
By Anna Skinner
Associate News Editor
0
Share
Newsweek is a Trust Project member
See more of our trusted coverage when you search.Prefer Newsweek on Googleto see more of our trusted coverage when you search.
The polar vortex is breaking down in an “unprecedented situation” unusually early in the season, and it will send a burst of cold air into the United States right at Thanksgiving, temporarily clashing with the warmer conditions previously expected from the strengthening El Niño.
The breakdown comes after meteorologists warned of a Sudden Stratospheric Warming (SSW) event beginning to take shape at the end of October, unusually early for the season. When the air in the stratosphere warms suddenly during an SSW event, it can disrupt the polar vortex, which allows the frigid air to spill southward into the U.S. a few weeks later. Impacts could be felt as early as this weekend and again over Thanksgiving in a direct clash with what typically occurs during a strong El Niño climate pattern, which typically causes warmer, drier conditions across the northern tier of the U.S.
“This is an unprecedented situation,” AccuWeather long-range forecaster Paul Pastelok told Newsweek on Thursday. “Generally, we don’t see these kinds of SSWs of this magnitude in the month of November.”
Read More on Weather
The weather phenomenon is more common in January and February, when it is associated with Arctic blasts that can plunge the feels-like temperature in parts of the U.S. to minus zero or colder.
...
What Is a Polar Vortex?
The polar vortex is a large area of cold air and low pressure surrounding Earth’s poles, according to the National Weather Service (NWS). It is present year-round but weakens in the summer and strengthens in winter. The vortex often expands during winter, sending blasts of Arctic air southward over the U.S.
Winds high in the stratosphere trap 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.
What Is a Polar Vortex Collapse?
During an SSW event, the stratosphere warms considerably. This disrupts or even reverses the winds, which can cause the polar vortex to break down and allow Arctic air to escape.
"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 said.
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.
How Will the Polar Vortex Impact Weather in the US?
When the polar vortex breaks down, it allows for frigid Arctic air to descend into Canada and the U.S. Typically, the polar vortex breaks down later in the winter season, when there’s more snow across Canada. This is important because the snow can help maintain colder temperatures, which can contribute to more significant and prolonged cold events in the U.S.
Since it’s so early in the season, that snow doesn’t exist yet, Pastelok said. So although the polar vortex will cause a plunge in temperatures across the U.S., it won’t be as significant or as long-lasting as if it had occurred later in the season.
However, impacts will still be felt. The breakdown is likely contributing to a system bringing cold, rainy weather and high-elevation snow to the Northeast and Mid-Atlantic this weekend, Pastelok said. Another round of weather impacts will blast the U.S. later in November, over Thanksgiving weekend, and into the first week of December.
That sudden dip in temperatures could be accompanied by the first snow of the season for some areas across the Northern Rockies, Montana, North and South Dakota, the Midwest, and the Great Lakes regions over Thanksgiving weekend.
What to Expect from Polar Vortex Clash with El Niño
The SSW and resulting polar vortex impacts will “flip” the forecast that was expected with El Niño, Matt Jones, meteorologist and manager of weather presentation at the Weather Channel, told Newsweek on Thursday. More cold air and snow is likely across parts of the U.S. that were previously expecting a warmer, dry winter because of El Niño’s influence. However, it’s too early for specifics, such as how cold it will get or how much snow will fall, Jones said.
While the drop in temperatures might not be as cold as if the SSW occurred later in the season, Pastelok warned the plunge could feel shocking considering the above-normal temperatures the U.S. has felt so far this fall because of El Niño.
Many forecasts do not yet reflect the SSW behavior, Pastelok said, but Americans should be aware of a cold snap over Thanksgiving weekend that might feel sudden given the above-average November temperatures that have been felt across the U.S. so far this month.
The NWS Climate Prediction Center currently shows chances of above-average temperatures across most of the U.S. over the next eight to 14 days, with a small chance of below-average temperatures in the Southwest. Meanwhile, most of the U.S. has an above-average chance at precipitation during the same time period, which includes Thanksgiving Day. Should cold temperatures become more widespread but precipitation chances stay the same, widespread snowfall could be possible.
Contact Newsweek editors on this story: Gray R. Thomas
View 0 Comments
Submit Correction
View Editorial & AI Guidelines