If you look into the stratosphere, around the 15th/16th January, a significant weakening of the zonal winds in 10 hPa at 60 N is ongoing.
This can be seen as a clear indicator of an SSW.
However, there is no indication of a polar vortex split, just a “displacement”.
Nevertheless, this process (“minor warming”) could pave the way for cold phases
over Europe because the westerly wind drift (weakening jet stream) is responding
Then about 7 to 14 days later often subsides and blocking highs cold
Air masses could shovel towards the European continent.
Since mid-October due to westerly weather conditions with lots of wind and rain and mostly
which was characterized by mild temperatures, has now been completely changed. The main cause is a
wedge rising far to the north over the northeast Atlantic, located between 2
powerful long-wave troughs (one over the North American continent, one
over Scandinavia) to the south of Greenland and to the Norwegian Sea
could. This Omega pattern proves to be very robust into the medium term.
Although it gradually shifts somewhat retrogradely, it acts as
Blocking into the lower atmosphere and even leaves the Rossby wave number
go back from the current 6 to 7 to 4 to 5. So the wave patterns move
slower, which could increase the persistence of the block.
from German DWD synoptic mid range outlook