The polar vortex: What to know about the weather feature responsible for the arctic blast

One would wonder what is causing this impending period of below-normal temperatures, especially as the U.S. prepares for the biting cold of winter. The polar vortex is the explanation, to put it briefly.

What does that signify, though?

According to Paul Pastelok, a senior meteorologist at AccuWeathers and the chief long-range forecaster for the United States, the polar vortex is a consistent feature that starts to form around September and lasts until spring, perhaps April or May.

In essence, the vortex is a zone of low pressure in the atmosphere’s upper layers over the polar region. According to Climate.gov, this vortex is made up of strong westerly winds in the stratosphere, roughly 10 to 30 miles from the North Pole.

Because it is an area of low pressure, the rotation is typically not counterclockwise, according to Pastelok. Therefore, the majority of the cold is usually trapped and concentrated over the polar region when the polar vortex gets stronger and more powerful over the pole.

When this occurs, the U.S. and other middle-latitude regions often get chilly, possibly pleasant temperatures and a west-to-east air flow—nothing unusual, Pastelok added.

But occasionally, warm air influxes cause the polar vortex to break up. The vortex may halt or wobble when powerful air waves from the troposphere—the layer in which humans live—break through the stratosphere. According to Climate.gov, these occurrences have an impact on the polar jet stream, which is located between 5 and 9 miles above the Earth’s surface.

When the polar vortex is disrupted, the polar jet stream frequently takes on a wavy appearance with dips and ridges rather than remaining farther north and maintaining a steady flow. The impact of the disturbance in the polar vortex on the polar jet stream is not entirely understood, according to Climate.gov.

When this interaction occurs, cooler air fills the troughs and brings wintry weather with it, while warm air flows north into the Arctic.

An earlier disruption than initially anticipated

Such a break in the polar vortex will cause a blast of Arctic airout of the north to have some influence across most U.S. states as of Saturday afternoon.

Extended blow in the Arctic Monday through Friday: highs of 32 F (city/coast) and mid-20s (interior). Teenage lows. Wind chills are one degree above freezing at the coast and below freezing in the inland. Keep pipes from freezing!0HefvkzkNn pic.twitter.com/

Even for this time of year, when chilly temperatures are at their highest, conditions will feel below average due to surges of wintry air over the course of the coming week. AccuWeather predicts that temperatures in New York City will reach lows in the low 20s and highs of about 30 degrees throughout the course of the next week.

At first, in early November, Pastelok thought that this winter would bring about a sweep of the Artic air to the south, but he did not anticipate that it would happen so quickly.

Although it is challenging to forecast such disruptions, Pastelok initially thought that a disruption would occur near the end of winter after reviewing previous studies and conditions. Paradoxically, Pastelok initially believed that January would see a very powerful polar vortex.

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