Winter and the Polar Vortex

[jssailem]

What is it:

The polar vortex is a large circulation of cold, low-pressure air around the poles, strongest in winter. The stratospheric version, 10–30 miles up, is most important for surface weather. When strong, it keeps Arctic air confined near the pole and the jet stream farther north, favoring milder mid-latitude winters. When it weakens, stretches, or splits—often after a sudden stratospheric warming—the jet stream becomes wavy and lobes of frigid air plunge southward.​

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In North America, this produces multi-day to multi-week Arctic outbreaks with extreme cold, dangerous wind chills, and snow or ice, sometimes reaching the Gulf Coast or Florida. Not every cold snap is polar-vortex driven, and impacts vary by region.​

Here is what it looks like from 30km. Images are 13 days apart. 05Nov and 17 Nov


At 500 hPa (about 5500 m), you can see how the jet stream is affected. No longer smoothly circulating the globe. Nodes appear bringing Arctic air south


What is interesting is that this year the Vortex shape is varying early. Variations usually do not occur until later in December/January.

This will impact our winter weather conditions as this cold Arctic air spills out across our homes.

It looks like an interesting winter, thanks to El Niño conditions in the South Pacific this year.

 

[Will Gilmore]

Variations usually do not occur until later in December/January.

Here in New England, we usually get a January thaw called, Indian Summer. Supposedly, the natives convinced the early European settlers that the January thaw was the end of Winter, and Summers come early to the NE region of the Americas. I can tell you that is not so. Summer is never early here.

Thank the good lord for trailers.

-Will