Lets have a look at the continuing trend to weaken the polar vortex. Now as I said the 18Z yesterday was a little more significant than previous runs, so it should be no surprise that the weakening was toned down on the 0Z. However on the 6Z the weakning is pretty evident again. Again this is all consistently happening after 192hrs so let's start there.
This is a pretty robust polar vortex, there is some fraying around the edges however note the central core of cold temperatures at the 500hpa. Indeed the geopotential height contours are about as symmetrical as it is possible to be, with the polar vortex essentially centred directly above the north pole. However, this is not to last as we will see...
By 240hrs the polar vortex is still strong, however it is becoming a little distorted. Over America a chunk is about to be chipped off, while over the central arctic the core of cold temperatures and low heights is becoming stretched and distorted.
By 300hrs the polar vortex has been pinched into a sausage shape and there is a rather large hold developing in our part of the world too. It is possible that if the weakness manifests itself in the right way we could actually even see a cold spell by this point; however that is secondary to the bigger picture here which is the weakening itself.
By 360hrs we see a very unhealthy looking polar vortex, there are bits of debris in the low lattitudes everywhere, including a rather large piece in SE europe. A large hole has developed in the European part which has invaded so far into the arctic that it has split the polar vortex in two with a major vortex lying over the Beaufort and a minor vortex over siberia. The distortion is becoming rather significant at this point.
We finish up with this; essentially we have a small polar vortex sitting to the north of canada, and a load of debris over Russia and SE Europe. Although the polar vortex may attempt to regroup; its possible the damage here could be irreparable and we could see a collapse.
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
Total: 8 days with snow/sleet falling.
2022/2023 Snow days (approx 850hpa temp):
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
Total: 7 days with snow/sleet falling.
2021/2022 Snow days (approx 850hpa temp):
26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.