This is the question I've been asking for sometime. This doesn't resemble the truely sudden warming over the Pole last February but seems to be imported from elsewhere. (Siberia).  I don't think the two are directly comparable and certainly the impact on hemispheric weather patterns has the potential to be entirely different....that's assuming it happens as progged of course. 

We also are now into the westerly phase of the QBO - which will have its say before long. Which big driver will win out ??

Mild towards Christmas DAY? - makes a change doesn't it??

According to the Met, 7-8 both sat and sun 

I don't know either - but like last February the SSW started in Siberian side if I remember. I don't understand why It doesn't warm up over the N, POLE/ARCTIC. - Why does it always warm up either side of the Arctic for warmer uppers in strat to push into Arctic /N. Pole? Why doesn't the warming ever start off in Arctic/North Pole? Anyone?

One reason could be that it's totally dark and away from the fringes of the Arctic circle. It's only a suggestion and there are many other factors that also fit into this jigsaw.

ECM 00z ensemble for London

Finally the GFS op has deciphered the pattern for this week with the cold air becoming established until late Friday - or Saturday per ECM.

The warm up shown by ECM (for the second successive run) is notable: a high of 3c on Friday to a high of 13c 24 hours later. The op was amongst the mildest options, but double digits looks quite possible at this point.

Beyond that nothing exceptionally cold but the milder options diminish somewhat. At this stage you'd favour a Christmas with normal to slight cool conditions, with highs of 5-8c and lows of 3-5c.

 riveting...

The charts certainly have a non-descript look to them at the moment.

Instead its all rather... tame.

You're likely to see one every time there's a depression with a non-occluded warm sector, so they're going to be very common whenever the set-up is more or less zonal.

It's a good question and is something that concerns me too, especially as the centre of the warming seems to be pretty much right on the opposite side of the Pole to us. The effect seems to be to "squash up" the polar vortex towards our side of the Pole. It doesn't look from those charts as if the normal stratospheric westerlies would be any weaker than usual in our neck of the woods.

As has been said on here many a time over the years, major SSWs are defined by a reversal of zonal winds, not just temperature. So even if it gets to +20 over the pole, if the overall circulation is zonal it's not a major SSW.

What you see in those charts is a minor SSW, the sort that displaces the vortex rather than causing a reverse zonal flow. If it's a breakdown of the pattern you want, you want a major, not a minor.

(The Holy Grail was said in the old days to be a Canadian Warming. We saw one of those prior to the "Beast From the East" earlier this year and, as you can imagine, they're rare beasts!)

12Z GFSP gives a spell of snow from the E Midlands north on Saturday.

Then it runs a 945mb dartboard across Scotland early next week. Meanwhile the GFS operational tries to build another mini Scandi high, keeping things a little cooler for a while.

If there were to be effects from any SSW, the longer range NWP should start to pick them up in the next week (presumably). It otherwise looks back to unsettled Atlantic driven stuff after this weeks much discussed and dare I say it overanalysed cool snap.

-9c uppers into London Fri with light snow flurries !!!

-10C at 850 on the ECM on Friday

And then a cheeky wraparound of colder air as a breakaway low goes through.

Still just delaying the inevitable mild mush though.

So the models have completely backtracked in the last 3-4 days, It just goes to show that continually forecasting the same atlantic scenario often comes to bite you on the bum-

@Shropshire @moomin
Even Mr Hugo probably wishing he hadnt tweeted dismissing the cold-

Even the ECM not immune to change ---Just 3 days ago ECM predicting -3c 850s for London at day 7 with the atlantic moving through- today the 96 chart is at -10c with atlantic a long way stepped back-
So much westward correction & downward change of the uppers it really does cement the UKs chances of a decent snow event this weekend...

Well, I'm pretty underwhelmed by the block hanging on for an extra day or two before being robustly shunted aside by the end of Saturday.

 A fairly low key event, serving if nothing else to at least cool things off a bit to something more akin to winter.  

10 days now and the days will start to lengthen, the long climb out of the darkness begins.

Given that the block was supposed to be shunted aside by Wednesday and it's now Saturday, that's still five days agreed.  I don't think it's yet certain to be 'shunted away' either.  We've seen days now of the models constantly shifting as the signals have shifted and I'm not convinced that process has ended, nor is there any reason to believe it must have ended.    The block to the east doesn't get blown away and the jetstream isn't being modelled to become reenergised into the weekend.

I've gone through the GEFS and I don't seem many hints in the way of blocking.

Looks like we will have to wait for 2019 before we see anything of note