Take more notice of the discussions than you usually do. There hadn’t been a better chance as this of a severe wintry period for many years and it’s always nice to see, in retrospect, how it all developed 😎

Amongst the TV Church and eating and games of a family Christmas, I always make room for some model watching.  I find the lack of data often leads to nice Christmas Presents of stella charts in FI.  As long as one doesn't take them seriously, its all a bit of festive cheer.

Im pretty sceptical of SSW events insofar as where the easterlies will set in at the surface and how many weeks later.  I tend to ignore and wait for the models to gain some consistency in the medium range.

Sounds good, Neil.

Not far off of my thoughts too. I think sometimes there's almost an assumption that SSW = UK cold, which clearly isn't true. It raises the chances but as ever where any resultant block sets up has to be in the right place for us to get any cold weather. I'd also be interested in any correlation between where the SSW occurs and cold weather incidences for our part of the globe.

In terms of the current models still some hints of a colder pattern in the mid to long term although arguably the near term has trended a bit milder. GFS is suggesting most likely route to a colder set up is our HP moving SW and then ridging North imo. 

All to play for and all that🙂

where it is mod pizzalled to take place gives positive thoughts about the pattern we will see. Look at the trends as well in ENS

I would be interested too. A split vortex that acts as the gateway for cold air to flood southwards is all well and good but if that residual lobe of PV persists to our due north or somewhere over the north west Atlantic then its always going to be a struggle to get the block in the correct place for our part of the northern hemisphere. Late December 2001 had a major SSW...after a cold start to the new year high pressure settled into Europe and resided there for the remainder of the winter. A very mild Jan and Feb 2002 for us resulted.

Back to the here and now there are tentative signs of retrogression of the high pressure cell and a trough digging into Scandinavia circa 3rd January ish. It will be interesting to see how that looks when I come back on New Years Day ! 

Probably best just to say that a SSW definitely changes things down here at the surface, and from the point of view of what the British winter is usually like, that's got to be a good thing. It couldn't make it any worse, could it?

Mind you, this is all just me thinking aloud. I'd love to know if anyone can answer Hippydave's question more authoritatively.

Nothing overly cold during the coming week next Sunday could see temps widely in double digits if the chart below on the right comes off

At least if the charts are poor tomorrow it can be blamed on missing data

Booked skiing in Italy for February half term but even that looks dire with rain snow limit yesterday was as high as 2400m in some resorts. majority of the resorts now do not have snow at lower levels. very disappointing so far.

Wrong thread 😉

I hope this thread stays clear of moaning and irrelevancy as it’s going to get busy from Boxing Day. 

Confident? 

Well they do say Christmas is the Time of Miracles, but I'm not holding my breath Neil.

Once again some candy from 6z GEFS , mostly in the GH camp.

At least it will be dry.

There are still large differences between EC & GFS Stratospheric vortex behaviour. In GFS vortex is displaced more than anything else, with anomalies stopping propagating downwards. Just think talk of cold UK is a bit premature for now... https://t.co/7Fj6kSk7Mk

— Chris Fawkes (@_chrisfawkes) December 24, 2018

On the Gary Sarre scale, about 80% 😉

I’ve made an effort to try to learn more about teleconnections and the effect of sst, solar, MJO etc in the last year - aided by Gavins excellent contributions - and I’m realising longer term forecasting (beyond the range we get to freely see) can be attempted. To this end I’m looking for some big developments from end of week one Jan.

SO tell me guys - Taken 2 days break from model watching, hoping to see a change to some stella eye candy cold and blocked charts but I have come back only to find a really strong/strengthened PV despite signs of a NAO Negative and AO as well as the fact this is after a SSW and on top of this we do have a weakening of the zonal westerlies - with many models going negative too!

My question is - Why so much low pressure over the N,. Pole? It was meant to become more blocked and cold?

Never seen the PV so strong in  many months! This below 06Z OP run is in FI but surely now we should be looking at more blocked conditions in FI not the opposite or shall we have to wait another few days? anyone?

There is a SSW underway, displacing the PV high up at 10HPa but the tropospheric response (300hPa and lower) relies on polar wind reversal which isn’t due to go negative until 31st Jan. Surface features influenced by wind reversal will not appear until 5-10 days after this.

I don’t know why people can’t accept that these things take time. IF the troph responds we should start to see it modelled on GFS from Boxing Day. And of course running through the heart of all this is the chance that the surface response (HLB) may not be positioned in our favour. The research suggests a split vortex is better than just a displacement but not all models gibwith the split at the moment.

Patience.

Tally, have a look at the tweet from Chris Fawkes a few posts up and Neil's post just above.

The SSW has to propagate down into the troposphere and there has to be a wind reversal.  Firstly that takes time - typically 2+ weeks; Secondly there's no clear relationship between a SSW and the response below.  Plus, as Darren pointed out several days ago, this is the time of year when the PV is usually at its strongest and therefore hardest to disrupt; last year it occurred at the end of the winter when the PV is weaker and easier to disrupt.

Again, as Chris Fawkes has said, GFS and ECM are showing markedly different effects, with GFS less favourable if you're looking for blocked conditions. That being the case it means studying GFS is going to be less encouraging.

The US guys are talking increasingly of cold plunges into the North Eastern States into January, and I worry that this could manifest itself with the PV over Canada and a fast flow Westerly across the Atlantic - all too familar. I think if the models start to converge on the High sinking by day 11 or so then it will be a squeaky bum time for hopes of Northern blocking.

That is one possibility, and one that has manifested itself with reasonable frequency over the years. There are other, perhaps less likely scenarios, such as a UK or Euro High. 

And there are other options like the PV over us or blocking in the North Atlantic but this is not a guesswork thread.

I wonder which, if any of those guesses, the GFS 12z op run (which is just starting to come out) will go with in the new year.

Indeed Michael.

It is also worth noting that very cold air over the NE of North America doesn't guarantee cyclogenesis off the eastern seaboard and even if areas of low pressure are generated the track they take depends on the jetstream pattern.  It is as possible that the jet dips over North America and then heads north, creating a ridge in the Atlantic.

I not 100% of this Peter but I think the SSW that took place during the 2012/13 winter happened around the middle of the season; sometime that January I think it was but I stand to be corrected if I am wrong. I do remember that the Xmas 2012/New Year 2013 period was very unsettled and mostly mild and this pattern continued until the second week of that January IIRC. As it happens, I do have a vague recollection of reading about a forecast SSW in these threads around that time.

Even with all of that, is there any direct connection with the SSW event in Winter 2013 and the pattern in the following March? Could not this have occurred independently of SSW?