Feb 10, 2023 - Energy & Environment

An event high above the Arctic may turn winter sharply colder in U.S., Europe

Computer model image depicting a strong stratospheric warming event over the North Pole.

Air temperature anomalies in the stratosphere Feb. 17 as simulated by the American GFS ensemble. Image: WeatherBell.com

A complex and highly consequential weather phenomena is slated to take place next week, as air temperatures about 100,000 feet above the surface, skyrocket and swirling winds around the Arctic slow or even reverse direction.

Why it matters: Known as a sudden stratospheric warming event (SSW), this can disrupt the polar vortex and displace frigid air masses into Europe and the eastern U.S.

The big picture: The main computer models forecasters rely on to help predict the weather are in near lockstep agreement that a sudden stratospheric warming (SSW) event will occur beginning next week. This one may be especially strong, too.

  • "The SSW looks quite certain at this point," Amy Butler, a NOAA meteorologist, told Axios via email.

How it works: Such events can occur when large atmospheric waves surge beyond the troposphere and into the stratosphere above it.

  • The vertical transport of energy can rapidly warm the stratosphere and set in motion a disruption of the stratospheric polar vortex, which is a circle of strong winds surrounding an area of low pressure above the Pole.
  • Over time, sudden stratospheric warming events are known to influence the troposphere below, which can affect the weather in the U.S. and Europe — typically a week to several weeks later.
  • Their effects may persist for more than a month.

Of note: In the recent past, sudden stratospheric warming events have led to major cold snaps in Europe, including the "Beast from the East" pattern that drove frigid air from Siberia westward into the United Kingdom in 2018.

  • They have also led to prolific snows in the Northeast U.S., though experts tell Axios that connection is a bit more tenuous.
  • Still, these events offer some hope to snow lovers in the Mid-Atlantic and Northeast, two regions that have seen little frozen precipitation so far this winter.

Zoom in: Judah Cohen, director of seasonal forecasting at AER in Massachusetts, said the jury is still out on exactly how the disruption of the stratospheric warming event will affect the weather in the U.S. and Western Europe in late February into March.

  • "How and whether this translates to exciting weather is still challenging in my opinion," he said via email. 
  • Simon Lee, a weather researcher at Columbia University who studies the polar vortex, said much depends on the extent and speed at which the changes in the stratosphere, including a slackened polar vortex, affect the troposphere below.
  • Already, computer models are signaling the likelihood of air pressure patterns over Greenland and the North Atlantic shifting into positions that favor cold and snow in Europe and can do the same for the eastern seaboard from Washington to Boston.

What they're saying: Butler said the polar vortex disruption is only one of many factors that will influence winter weather during the next few weeks.

  • "I think it's also important to recognize that the stratosphere is not acting in isolation on the weather but as one part of many other things going on; including the current La Niña."
  • "These factors may either reinforce or cancel out the impacts of the SSW in some regions," she said.

The bottom line: A strong stratospheric warming event is likely to take place next week, and there is the potential for high impact shifts in weather patterns to affect Europe and parts of the U.S.

  • However, there is considerable uncertainty on the specific impacts to come.
  • For example, if it takes several weeks for shifts to occur in the lower atmosphere, Cohen noted, the clock on the winter of 2022-2023 may quickly run out.
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