SAN FRANCISCO (KPIX 5) – Most of the free world thinks the “Polar Vortex” was born last year, when it became perhaps the ‘hottest’ weather term (pun intended) ever used since “positive vorticity.” Here’s a secret for you: The Polar Vortex has been around as long as there has been a North Pole (a long time) and as long as there has been a jet stream (also a long time).
The coldest air in the Northern Hemisphere typically hangs out near the North Pole, but there is an ebb and flow to this atmospheric system. This super-cold air sometimes gets sent south due to a dip – or “trough” – in the jet stream. n this side of the planet, the most common landing spot for this polar air is Canada. But every once in a while, the jet stream drops far enough south to bring much-colder-than-average temperatures to the United States. And that’s usually when it starts to Twitter…
It happened last winter. And it’s happening again soon. But this time there’s a cool twist.
If you follow weather on social media, you’ve likely heard of Super Typhoon Nuri. It’s a huge storm out in the Western Pacific Ocean, and as it becomes extra-tropical, it’s going to be one of the biggest storms to hit Alaska since the Carter Administration. Storms of this magnitude can create a huge “kink” in the jet stream.
In this case, Nuri has carved out a significant dip in the Pacific Jet. Downwind of that is an equally large ridge (of higher pressure). Further downwind is another big trough. And so on…
Follow this inter-connected path 5,000 or so miles, and you hit the West Coast of the United States. In case you haven’t been outside this week, it’s quite mild and dry for November in the Bay Area, and thanks to a strengthening ridge of high pressure, it will likely hit 80 this weekend away from the water. East of Denver, though, it will be a whole different story. Thanks to a big dip in the jet stream, it will be 20-30 degrees colder than average with widespread rain and snow. That dip will be referred to the Polar Vortex.
Maybe it’s the meteorologist in me, but I find it fascinating that a typhoon thousands of miles to our west… is helping grab polar air thousands of miles to our north… and all of that will make it snow on our friends in Cleveland this weekend.