The polar vortex looks even colder from space

The Great Lakes are mighty chilly.

great lakes polar vortex 2019
Natural color image taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite on January 27, 2019.NASA Earth Observatory/Joshua Stevens

It's dangerously cold in the Midwest right now, and unless you've cut yourself off from the internet you know why: the polar vortex. Streams of cold air are swooshing down from the northern latitudes and they're bringing some spectacular scenery along with them (even if it's too cold to appreciate the outdoors).

This image comes courtesy of NASA's Terra satellite. Taken on January 27, it clearly shows streams of air moving south and east across the Great Lakes. Those ribbons of white are called cloud streets—yes, that is the technical term—and they're right in line with the prevailing winds. Cloud streets are bands of cumulus clouds that form when a layer of cold air gets sandwiched between (relatively) warm water below and air above. The water gives off heat, causing thermal columns to rise up and then roll back onto themselves, forming kind of a long jelly roll of moist air. Those jelly rolls are the cloud streets (you can see a diagram here).

You see them mostly over and downwind of the lakes in this picture because of the increased moisture content of the water (cloud streets can happen over land too, though), which helps clear bands of cloud form. It’s for a similar reason that you can see lake effect snow—it’s the more thickly white portion of the image on the downwind side of each lake. As the cold jets pass over the water’s surface, they pick up moisture that later gets deposited as precipitation over land.

Meteorologists are predicting wind chills below -40°F in some states. That’s cold enough to cause frostbite in under 30 minutes. So stay inside, stay warm, stay safe—and appreciate the imagery on your laptop instead.