It seems likely that the GFS 12z op run was over-amplifying the mid-Atlantic ridge in 4-5 days time; every other major op run (UKMO, ECM, GEM, JMA) has a flatter pattern and the GFS 18z has more or less joined in with that line of thinking.
However...
The notion of an immense area of high pressure over Asia, centered over Sibeira or thereabouts, that resists the attempt by the convective flare up in the Indian Ocean to take it down and if anything may grow even stronger - well, that's gained plenty of cross-model support today
Now here's the thing - that blocking high may in fact give us a hard time before it's able to bring us much in the way of cold, snowy weather. You see, there's a lot of background support from the atmosphere (via the teleconnections - El Nino and the westerly QBO in particular) for there to be deep trough activity in the vicinity of Greenland, as the polar vortex descends on the region from the stratosphere, yet that Siberian High also has a lot of support, not just from the El Nino event but the feedbacks from the October snow cover advance as well, with the arctic sea ice also shaping up nicely for giving the block a boost. It really is no wonder that the feature is looking exceptionally large and strong on some of the model output at the moment.
Long story short, a mighty Siberian High battling a strong polar vortex is highly likely to end up displacing that vortex into the North Atlantic, placing it not far NW or N of the UK. For us, that means a wild ride with a real mix of warmer and colder airmasses but probably not getting all that cold for the most part. I believe this chart from the GFS 18z op run is a very good example of what I mean:
There's also an Alaskan Ridge attacking the PV from the other side of the pole. It can be traced back to the flare up of convection in the Indian Ocean, but as that convective activity is looking increasingly likely to die back down before long, support for that ridge should collapse soon into December. Believe it or not, that's actually a good thing in terms of lending the support to attacks on the vortex from an angle that's more likely to interfere with the vortex in ways that tend to bring the cold and snowy conditions our way. So today's developments - reducing the longevity of that ridge in favour of a continued, supersized Siberian High - have been promising in that regard
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T-Max: 30.2°C 9th Sep (...!) | T-Min: -7.1°C 22nd & 23rd Jan | Wettest Day: 25.9mm 2nd Nov | Ice Days: 1 (2nd Dec -1.3°C in freezing fog)
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