The polar vortex is nothing new. We've known of its existence since at least November 1853. It is a word the media just learned a few weeks ago, and since it sounds scary and new, they ran with it in order to drum up ratings. It's the same phenomenon as when everyone first learned the word "derecho" back in 2012.

So, what is it?

A model run from January 2013 showing the polar vortex dipping down into the Great Lakes region. This image is a year old -- don't misconstrue it as a current forecast.

The polar vortex is a long-lived area of low pressure that exists near the North Pole. It strengthens during the winter and weakens during the summer. Since it occurs during the northern winter, the air mass associated with the polar vortex can reach well below -50°F. Sometimes when a strong area of high pressure near Greenland blocks a portion of the polar vortex, a piece breaks off since it has nowhere to go but south, and it temporarily moves down into the middle latitudes.

Usually when the United States sees cold snaps during the winter, it's because a mid-latitude cyclone (a low pressure that originates here in the United States) drags cold air from Canada southward into the continental United States, freezing everyone's off for a couple of days and generating no less than thirty "ugh it's so cold #FML" tweets per minute.

If you think of a strong cold front as the air conditioning unit in a grocery store, think of the polar vortex as a jet engine that blasts freezy doom upon the middle latitudes.

Terrible map depicting the frigid air flowing counterclockwise around a low pressure system in the general area where polar vorticies like to sit when they move into Canada/the US.
Air circulates counterclockwise around low pressure systems in the Northern Hemisphere, and since the polar vortex itself is extremely cold, when it moves south into southern Canada or the United States, it brings some of the coldest air that is meteorologically possible to see in this region of the world.

It is not new. This phenomenon happens every couple of years or so, sometimes even multiple times per winter. We've had it relatively easy the past couple of winters where, even if it snowed a lot, it didn't get too terribly cold. This winter is more than making up for our past pleasures.

Why am I just getting around to writing this now? Sorry to be the bearer of bad news, but it's going to happen again towards the end of next week.

Jason Samenow wrote this over at the Washington Post's Capital Weather Gang about the upcoming "polar vortex déjà vu," describing what the cold snap could entail for the Washington DC area:

The first several days of this cold wave -from January 21 to around January 25 – will be cold but won’t share the intensity of the polar vortex event of January 7 and 8. In other words, expect highs in the 20s to low 30s, with lows in the teens (perhaps single digits on the coldest mornings). (Readings would be slightly colder than this north and west of the District.) These temperatures would be about 10-20 degrees below normal.

The potential for a more severe cold snap exists between around January 26-28. That’s around the time when both the operational GFS and European model show a huge piece of the polar vortex crashing south into Canada with tentacles extending deep into the U.S., not dissimilar to the January 7-8 event.

Weather models are showing temperatures becoming insanely cold across the eastern two-thirds of the United States starting later next week and lasting through the following week, with high temperatures on some days struggling to escape the 20s as far south as Mississippi.

You're going to start hearing a lot more about this on the news and weather sites as the weekend and next week continue. While temperatures probably won't be as cold as they were at the beginning of the month, it appears that it'll be a longer duration cold snap than the previous one, with temperatures still approaching the dangerous range.

So to recap...

-The polar vortex is not new.

-The polar vortex is like the angry gallbladder of the North American winter.

-The polar vortex is not new.

-It gets very cold when a piece of the polar vortex migrates southward.

-The polar vortex is not new.

-It's probably going to get very cold again starting later next week.

Since I don't come around these parts much nowadays, you can follow me on Facebook, on Twitter, and over at the Washington Post's Capital Weather Gang where I write articles every couple of weeks.

Stay warm.

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