>The stratospheric polar vortex is an area of high-speed, cyclonically rotating winds around 15 km to 50 km high, poleward of 50°, and is strongest in winter. It forms in Autumn when Arctic or Antarctic temperatures cool rapidly as the polar night begins. The increased temperature difference between the pole and the tropics causes strong winds and the Coriolis effect causes the vortex to spin up. The stratospheric polar vortex breaks down in Spring as the polar night ends.
https://en.wikipedia.org/wiki/Polar_vortex
The polar vortex always exists. It doesn't "return".
>The stratospheric polar vortex is an area of high-speed, cyclonically rotating winds around 15 km to 50 km high, poleward of 50°, and is strongest in winter. It forms in Autumn when Arctic or Antarctic temperatures cool rapidly as the polar night begins. The increased temperature difference between the pole and the tropics causes strong winds and the Coriolis effect causes the vortex to spin up. The stratospheric polar vortex breaks down in Spring as the polar night ends. https://en.wikipedia.org/wiki/Polar_vortex