Polar Vortex About To Go 'Haywire': What That Means For Temps In PA

The Arctic polar vortex is about to go “haywire,” and meteorologists are trying to figure out what an extraordinarily early disruption of the frigid air mass high above the North Pole will mean for Pennsylvania's winter weather.

“Everybody’s hair is on fire in the meteorologist community,” Judah Cohen, a research scientist at the Massachusetts Institute of Technology and director of seasonal forecasting at Atmospheric and Environmental Research, told Scientific American.

The uncertainty is especially significant this year because El Niño, which typically brings milder winters to much of the northern United States, is another wild card. An unusually early disruption of the polar vortex could complicate that outlook, but experts don't yet know whether it will send bitterly cold Arctic air plunging into Pennsylvania or somewhere else entirely.

For now, meteorologists with the private weather company AccuWeather say the shifting polar vortex isn't expected to unleash a bitterly cold blast across the United States. Northern Canada isn't particularly cold to begin with, and the coldest available air is expected to flow toward Siberia instead.

Pennsylvania is among a large swath of the United States which may turn wetter and warmer during the first half of November, Accuweather said.

"This time, what true cold air exists in the pattern will be directed to Siberia, rather than North America," senior meteorologist Brett Anderson said.

"The biggest change in the pattern that should become noticeable to just about everyone in the eastern half of the nation will be an end to the weeks-long sunny days with warm afternoons," Accuweather said. This stretch is probably more unusual for so long for so many areas than the upcoming cooler weather with some rain.

The second half of the month could be a different story for Pennsylvania and much of the east, with more significant cold outbreaks likely as atmospheric patterns change.

‘About To Go Haywire’

The last time the polar vortex experienced a disruption this early in the season was on Nov. 28, 1968, according to Cohen. Scientific American said in a report Wednesday that the vortex is “about to go haywire.”

Normally, the Arctic polar vortex spins like a top high above the North Pole, with strong winds circling a pool of bitterly cold air and keeping it largely confined to the Arctic. But like a spinning top knocked off balance, the vortex can wobble, stretch or even split apart when large atmospheric waves rising from lower altitudes disrupt its circulation.

When that happens, bitterly cold Arctic air can spill southward into the United States, sending temperatures plunging well below normal and sometimes locking large parts of the country into a deep freeze for days or even weeks. Such outbreaks are more common during the heart of winter, when Arctic air is at its coldest.

AccuWeather expects the polar vortex to weaken and shift out of its usual position in November, while the jet stream develops large bends that ordinarily allow frigid Arctic air to plunge southward.

An El Niño Wild Card

Complicating the outlook is El Niño, characterized by unusually warm waters in the tropical Pacific. It generally favors milder winters across much of the northern United States, but the disruption of the polar vortex introduces another variable that could alter the usual weather patterns.

Cohen cautioned in a separate interview with USA Today that the last El Niño winter, in 2023-24, featured two sudden stratospheric warming events but was exceptionally mild in the eastern United States.

“In short lots of uncertainty!” he said.