An early season arctic blast has sent temperatures across most of this country plummeting well below average this week and brought last winter’s buzzword, the polar vortex, back into the spotlight. From advertisements for winter coats to social media hashtags for almost anything cold, this technical meteorological term is being widely misused.
A polar vortex, according to NOAA, is a massive and persistent high altitude low-pressure system present over both poles of this planet. Basically a whirlpool-like wind pattern, the northern hemisphere’s polar vortex is anchored above the Arctic. It, as a whole, does not move south over the US. That said, pieces of it can ocassionally meander southward and influence our weather via the position of the polar jet stream.
When the polar vortex is strong, the jet stream generally flows in a smooth circular pattern from west to east and bottles up the Arctic’s coldest air. When weak or displaced by an area of high pressure, the shape of the jet stream distorts into a wavy, more north to south pattern. This allows cold air influenced by the polar vortex to push southward. When this happens, it is called a polar outbreak.
This week’s unseasonably cold temperatures are the result of a large ridge in the jet stream to our west that was enhanced by former typhoon Nuri in the Pacific. It, in turn, has caused a sizable trough to develop east of the Rocky Mountains and allowed cold arctic air to flow deep into the US.
In the video below, Dr. Mark Serezze, Director of the National Snow and Ice Data Center, explains exactly what the polar vortex is, how it works, and how climate change may play a role in its future.
Video credit: EarthVisionTrust and YouTube