The Stratospheric Polar Vortex normally forms a circle around the Arctic Ocean in Winter. You see the current pattern at Earth Nullschool with the settings for Air, 10 hPA, wind. Right now it's split and far from centered.
FishOutofWater has a great article. Polar vortex splits, record high heat into polar stratosphere, reco...
Normally there is one cyclonic vortex centered near the pole. Right now, there is a weak, warm anticyclone above the pole and there are two cold cyclonic vortices spinning over north America and Eurasia. There is intense compressional heating above the Labrador sea and central Eurasia caused by this planetary wave number 2 of unprecedented power. ...— warm over the Arctic and oceans — cold over the continents.
... warm water in the fall and winter in the seas on the Atlantic side of the Arctic, that used to be mostly ice covered, is destabilizing the polar vortex in late winter and changed fall and winter weather patterns across the northern hemisphere.
... cold air will be be displaced towards northern Eurasia for the next six weeks. Thus, northern and central Siberia, which are normally very cold this time of year will be even colder than normal. Western Europe may also be colder than normal because cold easterly flow off of the continent will be enhanced by strong Siberian high pressure. Most of the continental U.S. will likely be cooler than normal in March while Alaska will be likely be warmer than normal.
The Arctic is finally rapidly refreezing. See the temperature drop.
Overall, 2018 was the second-warmest year for the Arctic since record-keeping for the region began in 1900,...