The polar vortex is getting disrupted as temperatures climb high within the atmosphere above the North Pole, and this may lead to a major change in weather patterns over the U.S. and Canada as March approaches.
In simplest terms, the polar vortex describes a band of strong winds that circle the North Pole from around 55 degrees north latitude (the latitude of Ketchikan, Alaska) at about 10 to 30 miles above the bottom.
Why do those winds matter? Consider a spinning top. So long as the rotation is constant and stable, the highest stays spinning in a virtually fixed pattern. When the polar vortex is stable, the spinning winds circling the pole act like a wall that keeps the arctic air bottled up atop the planet.
In that situation, the midlatitude areas, including much of the U.S., will typically avoid bitterly cold conditions.
About every other 12 months, nonetheless, weather events within the lower atmosphere will send strong atmospheric waves up into the stratosphere, where they will interact with the polar vortex. The stratosphere is the layer of the atmosphere above the troposphere, which is where we live and where just about all the weather on Earth occurs.
Going back to the analogy, this has the effect of knocking the spinning top off its axis. It loses speed and severely wobbles and even topples over. Within the atmosphere, disrupting the polar vortex will cause it to decelerate and wobble, allowing the collapse of the protective wall around all that frigid air.
Now that the protective wall is gone, cold air is in a position to spill southward into southern Canada and the U.S., and milder air rushes into the polar regions to interchange it. That is if you might hear the term “sudden stratospheric warming” start getting tossed around – it’s a signal that the polar vortex has been disrupted, and the weather will start changing across the midlatitudes in the times and weeks ahead.
Based on NOAA, temperatures within the stratosphere above the North Pole and Arctic region are rapidly rising because of a sudden stratospheric warming event. This comes after the stratosphere’s temperatures in that region reached near-record lows in early January.
The sudden stratospheric warming event was kicked into gear by planetary waves, or disturbances, in each the troposphere and stratosphere, noted polar vortex experts Amy Butler of NOAA’s Chemical Sciences Laboratory and Laura Ciasto of NOAA’s Climate Prediction Center.
A planetary wave within the troposphere at the top of January gave the polar vortex a minor bump from below, which they said caused some rapid but modest warming. That event likely destabilized the polar vortex enough that a weaker disturbance within the stratosphere about per week later triggered a complete disruption and sudden stratospheric warming event, Butler and Ciasto explained.
“What the disruption will mean for weather down here within the troposphere remains to be uncertain, but sometimes these events result in extremely cold air outbreaks within the mid-latitudes of the US,” NOAA said in a blog post last week.
Because of this of the sudden stratospheric warming and coinciding polar vortex disruption, stratospheric temperatures have climbed by about 50 degrees prior to now week. NOAA noted that that is the fourth sudden stratospheric warming event within the last six years, which matches the frequency that’s been observed during the last six a long time of records.
Some guidance from long-range computer forecast models suggests a lobe of this disrupted polar vortex will first shift toward Europe after which proceed moving eastward over the subsequent week to 10 days. Other models take things one step further, first displacing the polar vortex after which splitting it into two pieces. Whatever the polar vortex’s configuration, NOAA said it’s becoming clear that the polar vortex won’t be in its typical form over the subsequent few weeks.
Sometimes, a disruption of the polar vortex has little impact on the weather. Other times, the impacts could also be delayed between two weeks to 2 months after the polar vortex initially gets disrupted, in response to NOAA.
Butler noted that arctic-air outbreaks followed a lot of probably the most recent sudden stratospheric warming events and polar vortex disruptions, however the resulting bitterly cold air happened in different regions on Earth and at different times after the disruptions.
“A disrupted polar vortex tends to have its strongest tropospheric impact over the North Atlantic, which increases the percentages for colder conditions across the eastern United States or northern Eurasia. But it surely’s not the one influence on the market,” NOAA said in last week’s blog post. “Other phenomena like La Nina, the Madden Julian Oscillation or the chaotic nature of the atmosphere may affect how our atmosphere reacts to a disruption of the stratospheric polar vortex.”
Butler told FOX Weather in an email that the earliest this sudden stratospheric warming event would affect the weather on Earth’s surface, based on the most recent forecast guidance, is in regards to the first week of March.
“The necessary thing is that this event can’t tell us of course that it’s going to get colder and snowier in any given location,” she said. “It merely increases the probabilities of those conditions occurring.”