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Decent signal for a strong mid latitude ridge signal across Christmas week in the EPS and GEFS for NW Europe. This looks plausible on tropical and extratropical signals right now. Thereafter, EC locks in a -AO out until February and drives the NAO negative mid January onwards. I would be expect movement of mid latitude ridges north and north-westwards over time as the impacts of the stratospheric warming take effect.

Im here & the grass is trimmed ready Im trying to find the time to update the my winter NH thread - However for anyone that didnt read it its here- If anyone does browse - We are homing in fast on one of the key features which was a record breaking negative zonal wind anomaly - The forecast for the SSW for 15 Dec is going to be around a week out- which along a timeline of about 5 weeks is very pleasing The date that the record goes is ~ 22nd to the 1st being the lowest ever- My other highlight being that we could beat the record -AO daily score will be under threat most certainly in January - With an outside chance of the Monthly AO record of Feb 2010 going as well. The fireworks are coming soon guys.... - just not in time for Crimbo.

Thank god the "Murr sausage" is covered up

I If this doesn't get a 'boom' I don't know what will... Let's put this into persepctive. Firstly, it is a forecast, aka it hasn't yet happened and thus could still 'go wrong' .However, even a (more likely?) watered down version will still be quite something. However, let's assume it is roughly on the button, it is nothing short of spectacular, For an (at least) 8 day period every single member has reversed zonal winds.This is happening, not in Mid February but in December. Digest that. This is very rare for the time of year. Fun charts incoming...

Where is Mr Murr ??? Hold on I’ve found him . He’s cutting and levelling the grass ready for the dumpings of snow in Jan ?

I will also add my musings to @Bring Back1962-63's post, which was on the same US forum. Just a few random musings from me. As you can see to start, we have a +NAMT right now. Look at the ridging to the East of the Rockies. This demonstrates a +NAMT. This is what is creating the uptick in MT anomalies, which @Bring Back 1962-63 observed above. But what you can also see, is that this quickly dissipates, under the pressure of lower geopotential heights. The Aleutian Low in the very short term, is going to dislodge very quickly, under the pressure of an anticyclone in the Pacific, as well as brief NAO/B-K Ridging. It splits off north and south, with the zonal circulation taking the former Aleutian Low south into the CONUS, to create a -NAMT, on accord of the breaking down of the Aleutian Low structure in the Pacific. It also creates/helps this beast, which I am sure is being well discussed in the shorter term threads. This is basically to show that the -NAMT is the mechanism or at least the reality of lower pressures like this. You need a strong jetstream to build the pressure, but you need something to release it. This is the releasor for this particular event. The much stronger releasing factor in a fortnight will be the SSW and it's tropospheric impacts in the AO domain. Apart from Days 5-6 which show more of an extension, it is consistently showing a poleward shift, which is due to the fact there is no low up in the Aleutians to keep the Jet down. But notice there is no retraction. The extension remains in place for the most part. You can see that in the 250hPa jetstream chart on Tropical Tidbits (not going to post pic, otherwise there will too many charts). It moves north, which will likely keep the steam train of snowfall events into the Pacific Northwest and British Columbia alive, and leave California and Tahoe rather dry in terms of precipitation and snowfall for the latter. This means I don't think there is such a massive -EAMT trend. We will see more -EAMT anomalies distributed in the next 3 days, but that is followed by a +EAMT event on GFS on D4-5. Then another -EAMT on D6-7, then the current Eastern European/Barents-Kara Block dislodges over the next 7 days, and comes down as a strong Siberian High, and links up to bring another strong +EAMT event for a good 3-5 days, boosting the North Pacific Jet. The +EAMT pattern stays until the end of the GFS Determ run (Day 8- Day 16 period). So it starts from the 24-25 Dec period, so with a 7-10 day lag, PNA effects to occur from New Years Eve into the New Year. Because it's so far out, it is hard to gauge the impacts of this with NWP modelling. Like do we get another Aleutian Low in the Xmas-NY inter period? Will it feedback loop with the developing SSW? All I will say is that it what goes down, must come up again..... does that work We should see the +AAM coming up again properly in the days leading up to the first day of 2019. I like something like the CFS GWO forecast below. Perhaps it may be a bit stronger in terms of Phase 5 and 6 orbit, but similar progression and timing (maybe a tad earlier though, but it doesn't really matter). Linking up with the SSW, that should be gold for the Eastern US for snow lovers. With a Stratospheric induced eventual -NAO, probably good for Europe as well in terms of cold. I will just continue the discussion quickly about the SSW. I don't think we will see a fully split Vortex, nor do I believe that a split matters in order to get desirable (snowy or cold) effects for the United Kingdom. We will see a technical SSW, and we will see very consistent w1 forcing, that will almost push it to a split vortex, but not completely. The options for genuine w2 forcing before the New Year are slim, and while I think there will probably be some sort of w2 forcing in January, as stratospheric alignments change, I don't think it will matter much, because the SSW, which will primarily take place in the next two weeks, will be pretty much done. There will be plenty of energy about in January (think +AAM), so there is an opportunity for sustained SSW conditions, which would enhance the tropospheric impacts, and would be the best option for an actual split. A displacement vortex doesn't typically bade as well for Europe, as it does for North America in terms of cold, but given the extratropical factors, I think a -NAO will develop and Europe will get it's cold. Maybe not record breaking, but it will be cold. The descending westerly QBO Phase isn't going to change these mechanisms much, it actually is climatologically linked with SSWs. Takeaway from all of that is the UK will get it's cold, given all of the surrounding positive factors.

Normally the Azores ridging to mid latitudes with a rampant vortex over the pole would not promise much for cold prospects. This is a different scenario though. We have a forecast warming hitting the top of the Stratospheric vortex within a few days. As this filters down the slowing of mean zonal winds will eventually undermine the lower vortex and continuing ridging will head into higher latitudes. Most of our notable cold patterns evolve from Azores ridging into Scandinavia then, as reversal takes hold, regression of heights to Greenland. Yes still speculation by me but the forecasted strength of this warming would imo allow for such a pattern.

The last time the Met were this bullish about a potential cold spell of weather was in November 2010 the rest as they say is history. Could we be on the cusp of a memorable winter period? Stay tuned for some jaw dropping charts to start appearing in the next 10 days I recon. I’d gladly sacrifice Xmas week and New Years for a spell of cold in January.

Goodness me that is huge upgrade from Exeter!!!. They must be really confident .. East or north easterly? Yes please!!

Short post - still at work. 18th Dec today....and no high lat blocking. And no sign in the near future. What happened? Taking tomorrow's ECM you can see the nose of ridging that was anticipated as creating a potential Greenland block on the back of a strong +MT event....but we havent quite got the necessary forcing to drive the storm track further south and allow the block to build. End result is that we are now approaching the period of downward tropical cycle...and we have insufficient blocking to promote much more than occasional PM air. Given the length of these forcings we wont see much change in the next week or so. So - that was a fail. We had a similar fail actually round about this time last year - another cycle that flirted with sufficient momentum to drive a high lat wedge into action, but failed really to get off the ground. But....and it's a big but....this is only the beginning. The next tropical uptick in momentum will time nicely for New Year - and this time the MJO will be closer to the prime 6 - 7 - 8 orbit and we will have a vortex in a much more unhappy state. Indeed we may even have a vortex that is splitting as the New Year begins....and these kinds of events can have swift tropospheric impacts. So - I'm a bit disappointed with the lack of heights this week - cant deny that - but no less confident about the impact of pacific forcing as the current MJO progresses and the strat comes under well documented and observed squeeze. Strat talk is all over the forums at the moment, and for good reason. Only 18th Dec. Only just over the start line in terms of forecasts that argued for a cold season. Plenty of time for these processes to take hold.

SSW nearly into range on the EC The fact that the Mid-strat down to 30mb is predicted to look like th below means January should hold a lot of interest for us. Way more than your average January does. The vortex split seems to be the buzz word(s) at the moment. Far too much emphasis being put into that IMO. Of course historically vortex splits tend to favour us but it is not the be all end all. As in, no split equates to no cold. And I never buy into a split finisihing off the vortex either. It will stun it, that's all. Unless we get incessant and strong follow up waves and warmings (possible but rare to last all DJF) , It will reform in no time as soon as we wane for any period, descending W-QBO will do little to help in that respect. Far from meant to be a doom and gloom post, quite the opposite. I am just saying that, the fact we have what is looking like a substantial warming, a probable SSW (and crucially in December) should be good enough for us all to chill out and wait and see what occurs next. The cold will soon spill out of the Arctic, there is absolutely zero doubt about that, whether some of it is for us remains to be seen yet. Personally, I think we will be seriously unlucky not to have copped for a UK wide snowy spell by the end of January.

Well there you have it. Our model spot on with a Easterly across Southern Britain on Christmas Day . Some low temps over parts of Scotland under the high cell. C

We've being doing that for the past six weeks!!

Seems to be a growing theme to shove a large chunk of the trop polar vortex / low heights into Scandi and NW Russia in the medium range, 00z EC loop below highlights this best: … couple that with amplification upstream over the N Atlantic - could lead to an interesting period around New Year. Whether this tied in with the SPV displacement is not quite clear though

If you were happy with yesterdays MET update take a look at todays. Northerly or Easting winds dominating with frontal systems bumping into the west to produce frontal snow. Christmas come early?

Struggling to find comparable displacement episodes of this magnitude based off GEFS and EPS.. This one possibly:

Not sure which part of the forum I am allowed to say the Met outlook is erm... amazing.

Cold ENS members grow

The xmas period runs from xmas to-new yrs day!! There 'understanably' seems a lot of focus regards xmas day. The 7 day period ( xmas).. Is and has been the likely starting point....and i continue with that notion.....

I’m in watch mode currently and only comment I’ll make is that I don’t buy the runs that show total zonal and mildness over Xmas week. I still don’t see major blocking or a sudden flip to that this side Over next 10+ days....but that should become apparent a little further down the line. Still waiting to see if more ‘sting’ for Xmas comes into play.....little steps have been made over last 18 hrs. Will watch a bit more BFTP

It looks like becoming quieter between xmas and new year with the weather pattern becoming very slow moving as pressure rises according to the latest models so probably increasing frost and fog risk..where do we go from there?..hopefully as per the experts..into a much colder January with E'ly / NE'ly winds bringing wintry weather, especially to the east!!

EPS lending support, split signature day 11

The low by 168t will become a shallow feature and start to sink. Changes now gathering a pace for Christmas. C

3 way split vortex!!!... have we seen this somewhere before???... sorry mods

Oh GFS (P) is a beaut

Interesting Graph to highlight the Heat Flux only beaten by two others. Dusper_WkAIWx4Q.jpg_large

My daily notes copied here along with the charts. Tuesday 18 december Ec-gfs and both show a progression from the last couple of days with +ve heights and ridging from the original position over Iberia/western Europe linking s of Iceland west into ne n America; ec shows a 500 mb flow from n of w over the uk with gfs pretty much no flow under the ridge Noaa show slight signs of +ve heights on its 6-10 sw of Iceland but it’s the 8-14 that really changes from even 2 days ago showing a contour ridge over the uk with the c of g of +ve heights at the apex to this (150+) so fairly significant. Where does this go after? One would imagine e or possibly ne This suggests that the gfs synoptic idea, over an average of several runs for high pressure to be somewhere over the uk is perhaps not far from what we may end up with. To me there is no real signal, in spite of the changed upper pattern, of deep cold for the uk in the run up to, through or just past Christmas. As ever time will tell me if I am right or wrong! There is room from the charts shown below for post Xmas IF the upper ridging settles in the correct place for either a northerly flow or one from the NE. To me I would rate that, in the 15-20 day range as no more than 15-20%. The GFS version of the MJO suggests it moving into phase 5 which does not correlate to the 500 mb pattern being where cold lovers want it! http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Several hours later.... It's looking impressive again...

Without going into detail.. There is large gain via the models this morning. And to my eye...we've reached the crucial 'turning point'...(via model decipher)..as the notions are catching up.... Some good viewing from todays suites.....!!!!

Just been browsing this site, winter 1947 http://www.swanstonweather.co.uk/Pages/SitePlan.htm

The large cell...will/should likely retro-or expand and try to plot directly into the pole!.. Raw assumption's still in a non decipher/elevated stage. .....but are gaining/getting there.. Slowly slowly catchy.....

Pert 15 says Happy New Year

Obliteration of the strat on the GFS 06z - reversal from 264 hrs (29/12 06z) down to -18.7 m/s at t372

The has been fired!!!.. And the reverberations felt-noted!!.. The momentum and sync will now sniff the ramifications, as they are played out...and model conciencious.... and matching 'should begin alignment... As we have now gained....-as thought-.. And the countdown to cold....opens.. Starter...then main course. Note-compares of raws through todays suites.. I'll wack some data/support/snaps/Analysis..after the 12z ecm... Winter lifts off!!!!

A dream day ski-ing on the Aineck Mountain. Last one for 6 weeks before embarking on my trip to Vancouver via Sussex for a few days over Christmas. Well what a messy outlook from most NWP models for Christmas. None really showing the same out puts at 168t. Anyway , this what our shows this morning ( very latest ) and yes a Easterly drift over Southern Britain on Christmas Day as the Atlantic trough pushes slowly and erractically NE from the Azores towards the Channel with possible shallow low circulation. Pressure rises to follow across the UK generally in the period 168-240 . A lot of uncertainty in the medium longer term charts , so verification expected to be low. Interesting thoughts about ECM runs which seem to indicate much lower heights to the NE in the run up to New Year but as yet has little support from the main models but not to be discounted. As I say all a bit messy but further developments could move at a pace just before Christmas , so one to watch. C

Ukmo forecast 144hrs

That’s is really impressive, main point you mention is the timing, if we do benefit I’m not sure there is a more perfect timing - long nights, slightly warmer sea temps than Feb/March which helps convection and a sun that won’t melt lying snow when hovering around freezing . All fingers crossed, keep an eye on that METO medium and long range for guidance .

Temp anomaly plot is insane on EC. Good call @Glacier Point on Boxing Day... The 50hPa plot is intriguing what a set up that could be come should it imprint on trop. Totally fascinating and still feels a little surreal vs usual canonical vortex intensification periods we are 'seemingly' accustomed to. Part of me thinks - is this another canary in the coal mine a la 'QBO Blip'? Events clearly not helping the NWP at present!

Hot off the press ..... ec op 12z is different .... split at 10hpa begins at T210 and this downwells to 30hpa by day 10 Note the placement of that ridging ....... I wonder If that’s where it will settle in the trop a week or so later .....

And the Jet Stream is off to Spain! Olèèè olè olè olèèè!! ?️

It's not. Summer sun posted one but it hadn't updated. Here is today's. Through the first half of January, there is an increasing likelihood that colder weather may begin to dominate with a greater chance of seeing east or northeasterly winds. Should this occur, then wintry conditions are possible in eastern, southern and central areas with western parts of the UK staying relatively drier. Though should any Atlantic frontal systems try to make inroads western areas could also see some snow. Although signals suggest that a cold spell is the most likely scenario in early January, the extent and longevity of the cold weather is uncertain. Wet, windy and mild weather may still be possible at times.

A very very respectable split SSW showing on the 6z, big reversal

Strongest reversal yet for the GFS op on the 0z at -8.5 m/s. Parallel still not as interested, minimum +2.3 m/s, fascinating.

Not to over-hype, but I really am feeling we are on the cusp of something big! That is some reversal!! Given its middle Winter! Nice not to be chasing and Hoping for a February SSW and cold spring for a change! If we can tap in to some cold air from the east or NE the SST’s are primed for everyone’s favourite machine If we can get the Baltic Sea to cool down a bit more that would be good. Don’t want convection building to early and spinning up any spoiler shortwaves! (Should we tap into an easterly) all conjecture at this stage of course #justsaying

The coke can on the track has derailed nothing. It’s on like donkey kong! I’ve been sitting back and watching from a distance the past few weeks. But I feel we are closing in on something epic here. GFS tried to rise heights to our N towards the middle of the run, but then returns to its default mobile pattern. Looks to me like we could be seeing the first signs already. Let the fun begin! Worth remembering that a SSW doesn’t guarantee UK cold, but increases the chances very significantly but alas the weather will do what it will do! So don’t get to hung up. Especially as there is likely to be an awful lot of model volatility over the next couple of weeks at least! Be kind to each other people, ‘‘tis the season of jollyness enjoy the ride

The worst you can say about the current output is that the Atlantic onslaught slows down and allows for some transient colder spells, you could imagine some of those being potent enough to change the trend. I am not convinced that a stratospheric warming is a cause and surface cold is an effect, maybe they are just two things that happen at the same time. So hoping for the SSW is perhaps just a different form of hoping for cold weather. I think it's coming in January anyway, the feature interval of 21-23 Dec is not currently looking make or break but I could imagine it prolonging the Atlantic dominance in a more emphatic way, so that's some sort of win for coldies anyway (energy peak is not going into a major warming or stormy peak, but expect a little sting in the tail of low pressure around those dates, model upgrades possibly).

It wasn’t underwhelming Karlos - people were simply not comparing apples and apples - didn’t help that the week 3 set up was completely different to previous runs with the nw European block weeks 4/5 through 7 continue to look like the weatherbell anomoly chart I posted last week - think of a classic late seventies winter set up .......

Yes it's all looking on course for a Christmas time hit at the top of the vortex as already posted.What we see on day 1 comparing to forecasted day 10 is dramatic as the heat flux filters down from the top and those oranges turn to blue indicating the zonal winds are reversing. I like these graphs as they give a simple overview of the expected slowing and then reversing of the zonal winds at different levels along with wave amplitude and effect on temperature through the vortex. By day 10 on yesterday's forecast at 10 hPa we can already see the squeeze on the vortex from the warmings suggesting the first stage of displacement is underway. Looking at the day 15 GFS06z forecast we can see this progressing well All this time zonal winds lower down will be decreasing so the effects on our 500h Pa pattern will become more evident in NPW in the coming days .I would expect further weakening of the jet and signs of mid-latitude ridges extending further north into higher latitudes.

I’ll take an easterly with a side of channel low please

Yesterday’s ec op 12z was 3.97m/s at day 10. This mornings run continues to sink and stretch the spv so I expect tomorrows Berlin update will show a technical ssw by day 10