The Polar Vortex Is Behaving Strangely. What It Means for the US

A strange disruption to the polar vortex is underway, but forecasters do not expect it to bring extreme cold to the United States. Private weather company AccuWeather said the polar vortex is behaving unusually for this time of year, with winds high above the Arctic expected to drop to 9 mph on November 3, which it said compared with an average of 58 mph and a previous record low of 32 mph for the date. Although a disruption of this scale would normally prompt concerns about Arctic air reaching the U.S. , the forecaster said its meteorologists do not expect this event to produce a major outbreak.

Read More on Weather ... What Is the Polar Vortex? The polar vortex is a large region of low pressure and cold air that surrounds both of Earth’s poles. It is always present near the poles but weakens in summer and strengthens in winter. The term "vortex" describes the counterclockwise flow of air that helps keep colder air near the poles. During the Northern Hemisphere’s winter, the polar vortex can sometimes expand or become disrupted, allowing Arctic air to move south with the jet stream.

This happens relatively regularly and can bring periods of unusually cold weather to the U.S. ‘More Like Fall Than The Arctic’ "The polar vortex is weakening at a time when it should be gathering strength, but a key ingredient for a significant Arctic blast in the United States is missing. There simply has not been enough cold air building across Canada to send south," AccuWeather meteorologist Tyler Roys told Newsweek . Roys explained that most of the coldest air is now centered over northern Russia, meaning any shift south would be more likely to affect Asia and Europe.

"This is an extraordinary atmospheric event, but it may end up having very little impact on weather in the United States," Roys added. While temperatures are expected to trend cooler in parts of the country during the first half of the month, this will be driven more by local cold air rather than the polar vortex, said Accuweather. The forecaster added that some of the sharpest drops in temperature may take shape over the Southwest. "While some amount of disruption to the polar jet is pretty typical for fall as the transition to winter begins, the current polar jet pattern appears more like it's midwinter than midfall," AccuWeather meteorologist Lydia Burroughs told Newsweek Sunday.

"The largest factor preventing a major Arctic outbreak in the United States is the warmth that remains to the north in Canada. Not only is it early in the cool season, but persistent high pressure has kept temperatures in the territories and northern prairie provinces 10-20F above the historical average. This is the air the polar jet brings with it when it dips into the central and eastern U.S. "Until these areas become cooler, that air will feel more like fall than the Arctic."

Conditions could cool further during the second half of November, according to AccuWeather, which reported the jet stream pattern may change enough to allow periods of chillier air to move south later in the month and into December. Contact Newsweek editors on this story: Daniel Orton and Trevor Davies .