The National Oceanic and Atmospheric Administration (NOAA) defines the Polar Vortex as “a large area of low pressure and cold air surrounding the Earth’s North and South poles. This definition generally refers to atmospheric circulation in the stratosphere, and not the troposphere.
In polar regions, the bottom edge of the stratosphere starts about 5 miles above the ground and extends upwards to around 30 miles. The troposphere is the layer between the ground and the stratosphere and is where we live, work, and play.
When the Polar Vortex is stable, cold air remains around the polar region and there is less chance of winter weather in the Mid-Atlantic and Northeast regions of the United States. In Canada, our neighbor to the north, the early part of the winter season has featured above-normal temperatures, according to The Weather Network.
Schematic is by NOAA Climate.gov and is adapted from Waugh et al., 2017, Bulletin of the American Meteorological Society.
However, like NOAA’s forecast, The Weather Network also has models showing several drivers that are already in place to support a major pattern change that would send Arctic air plunging south into Canada, and even further south, into the United States, sometimes in either mid-January or late January.
What is happening right now
A sudden warming event in the stratosphere ( that region above the Troposphere) has sent temperatures shooting up to as high as 89 degrees Fahrenheit (31.6 degrees Celsius) in the last three weeks, according to the International Business Times.
Amy Butler, a research scientist at NOAA’s Chemical Sciences Laboratory, says that stratospheric warming events that knock the polar vortex off balance are triggered by “an upward flow of large-scale atmospheric waves” from the lower atmosphere. This means the stratosphere can then transfer energy in downward-moving waves, leading to blizzard conditions in some areas, reports The Hill’
Think back to the winter of 2013-2014, when broken-off pieces of the Polar Vortex caused blizzards and heavy snow in cities like Chicago, Washington, D.C., and Boston.
Dr. Judah Cohen of Atmospheric and Environmental Research in Massachusetts, along with other experts predict that this year, the stratospheric warming will likely lead to a split polar vortex scenario, with one center over Eurasia, and the other elsewhere.
Cohen adds that while “Polar vortex splits do favor big snowstorms,” it is still unclear whether the warming will impact parts of the U.S., as similar warming last year did not throw the vortex off-balance enough to lead to a particularly harsh winter.
“The first push of Arctic air seems likely to begin later during the second week to early in the third week of January (11th to 15th) from part of western Canada and the U.S. Rockies,” AccuWeather’s Lead Long-Range Meteorologist Paul Pastelok said. However, keep in mind other players that could influence the severity and track of storms coming down the pike.
“An ongoing active storm track in the southern U.S. will then help to pull the colder air through the Midwest and into the East in the wake of the storms,” Pastelok added.
“After the first surge of Arctic air, there are likely to be additional waves of cold air that spread from the Central states to the Eastern states during the latter part of January and into early February,” Pastelok explained.
There will be other forces that come into play, like the amount of snow already on the ground, or the temperature of the waters over the western Atlantic, which have tended to be above the average of late, explains Pasteiok. “But, on the other hand, Gulf of Mexico waters have cooled and will likely cool off even more during the balance of January and may allow easier access to cold waves.”
