Cold weather could hit millions of Americans as polar vortex shifts (Image credit: LPETTET via Getty Images)
Forecasters warn that a shifting polar vortex could send Arctic air into millions of Americans in the second half of March.
The polar vortex typically traps cold Arctic air over the North Pole, but experts suspect it is beginning to shift and expand. The disruption could create conditions for spring snowfall and storms in the central and eastern United States, according to a statement released by weather service AccuWeather.
“Don’t put away your winter coat and gloves just yet,” said Paul Pastelok, lead long-range forecaster for AccuWeather, in a statement. “Winter isn’t over yet. Parts of the central and eastern U.S. are set to see a surge of spring-like warmth next week, but a polar vortex could cause temperatures to plummet across parts of the country the week of March 17.”
The shift in the polar vortex will allow Arctic air to rush south into North America. However, it’s unclear how much of an impact this will have on the weather. With warmer spring temperatures on the horizon, any Arctic air that does enter the U.S. won’t be as cold as it would have been if it had happened in January, according to the National Oceanic and Atmospheric Administration’s (NOAA) Polar Vortex blog.
The polar vortex is an area of low pressure and cold air that circulates around the poles in the stratosphere, a layer of the atmosphere 7.5 to 31 miles (12 to 50 kilometers) above Earth's surface. The Northern Hemisphere's polar vortex typically expands in the winter, sending a stream of cold air south along with the jet stream, according to the National Weather Service.
There are many different factors that contribute to cold weather, so not all cold snaps are linked to the polar vortex. This winter, the vortex has actually been strong and stable for much of the time, with fast-moving west-east winds keeping Arctic air contained within the Arctic. However, a sudden warming will reverse that trend.
The temperature difference between the North Pole and the equator maintains the polar vortex's strong west-east winds during the winter. However, a sudden warming in the stratosphere could disrupt this rotation and change the winds' direction. Such warming could shift the polar vortex or split it in two, according to the Polar Vortex blog.
The polar vortex may not regain its strong west-east winds after the warming, making this the last stratospheric warming event of the season. The so-called polar vortex event occurs each spring (usually later in mid-April) when sunlight returns to the North Pole and the temperature difference between the North Pole and the equator decreases, according to the Polar Vortex blog.
Patrick PesterNavigate Social LinksPopular News Author
Patrick Pester is a well-known news writer for Live Science. His work has appeared on other science platforms such as BBC Science Focus and Scientific American. Patrick retrained as a journalist after working in zoos and wildlife conservation earlier in his career. He received a Master's Excellence Scholarship to study at Cardiff University, where he completed an MA in International Journalism. He also holds a second MA in Biodiversity, Evolution and Conservation in Action from Middlesex University.
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