Interactive explainer

Vortex Lab

Everyone is talking about the polar vortex "collapsing". Here's what that looks like. Drag the sliders to change the wind and the two kinds of wave bulge, or jump to a preset. The map is a view from directly above the pole, with the dashed ring at 60° latitude.

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Where is it, exactly?

Cross-section of the atmosphere The troposphere runs from the ground to about 12 km and holds the weather and the jet stream. Above it the stratosphere reaches about 50 km; the polar vortex lives between about 15 and 50 km, and its wind is measured at 10 hectopascals, around 30 km up. 0 km1020304050 tropopause ~12 km stratopause ~50 km POLAR VORTEX ~15–50 km up, poleward of ~50° 10 hPa ≈ 30 km: where the 60° wind is measured ozone layer (~15–35 km) balloon jet stream ~10 km · weather lives down here ✈airliners ~11 km Everest 8.8 km

Two vortices, one name

There are really two polar vortices. The stratospheric one, which is in the news this week, sits 15–50 km up and only exists from autumn to spring. The tropospheric one is lower, around the jet stream, and is there all year.

Most "polar vortex" cold snaps on the news are the lower one dipping south. A sudden stratospheric warming matters because it can change that lower flow a couple of weeks later.

Altitudes are typical values: the tropopause sits lower near the poles and higher in the tropics.

Now break one yourself →

The polar vortex in nine cards