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Hi. I just wanted to create a post from an educational perspective and also be a point of reference regarding the importance of the GSDM and the AAM on the medium and long term. Hopefully, anyone who questions this should change their mind after reading the below. The reason it is worth doing this is because there is no better, clearer, example of the importance and connections between those upstream, Pacific developments and the downstream influence. I'll attempt to highlight and stitch this together using some of the usual plots and charts which tell the story so very well indeed and it is this which, hopefully, helps people to at least better understand the influences of the GSDM and what to look for moving forward. OVERVIEW: Firstly, we have just endured a very wet December, this comes as no surprise given what happened to the AAM in late November. Interestingly, seasonal models all pointed towards December being a +ve NAO month, in keeping with the long-term teleconnections with regard El Nino and a +IOD in early winter. The late Nov and early Dec cold spell can be linked back to the behaviour of the GSDM too, while what followed through much of December certainly can and what is happening now and looking ahead, most certainly is. Despite a weakened stratospheric polar vortex, it is the troposphere that is 'leading the dance' rather than the stratosphere for the most part even though it is lending a hand. The late Nov/early Dec blocked pattern has links to the temporary rise in the AAM in mid-November, with the usual lag in place. We can see this first evolution in the below plots... The second and more obvious evolution was then the more pronounced fall in AAM through late Nov as the MJO returned to the W Hem and westerly inertia was removed from the GSDM budget and, as usual, AAM fell along with a -FT (Frictional Torque) and -MT (Mountain Torque) event. The result was, as ever, propagation through the extra-tropics and then into the mid-latitudes of more westerly momentum, propped up by easterly momentum at circa 30-40N - Remember the inflated Azores high in the run-up to Christmas? - We can see how the +AAM anomalies, in particular, were distributed through the atmosphere within the usual window of approximately 14 days. No surprise we then saw an enhanced period of +AO and +NAO conditions just before mid-December onwards. Lastly, comes the 'big event' within the last week or so in terms of the pronounced rise in AAM. Once again, in complete contrast to what happened through mid-November, with a lag of course, we can see how the marked rise in AAM has allowed the propagation through the sub-tropics and into the mid-latitudes of more easterly inertia (-AAM) very well indeed, this is particularly obvious on the relative AAM transports plot, as highlighted below. Once again, no surprises at all and of which has been documented by the usual few on the group we are now seeing a complete reversal of that +AO and +NAO period with an array of mid-latitude and, eventually, high latitude blocking patterns. We can also see this visually on the zonal wind plots at 100hPa (top of the trop/bottom of the strat) too. While like in many areas of meteorology, there is never often a usual "a+b=c evolution", but this is about as close to that as you can get. We have certainly had help from the stratosphere here mind because a robust stratospheric polar vortex that is downwelling westerly winds into the troposphere can often be the dominant player, overriding what has occurred over the last month. There is likely to be some 'help' here from the El Nino and eQBO combination this winter as the sPV continues to remain disorganised and far weaker than it can be at this point in the winter with far less influence on the troposphere too. When it comes to the AAM it is crucial to be able to accept and acknowledge when there are other overriding influences and counterbalances. Tamara et al often talk about not taking the MJO at 'face value', it is similar with the AAM, but when you combine the usefulness of the GSDM and all it incorporates then, as I have perfectly examined here, nobody can ever say the likes of the GSDM and the AAM is "flawed or useless" when it comes to pre-empting NWP, at times, and also gauging how the broader patterns may evolve and shift. As I mentioned at the start of the post, I wanted to put this one together because there is no better example of the usefulness of the GSDM than what has occurred over the last month or so. The evolution and 'story' of the atmosphere have been well played out in these plots. For those who want some winter weather after the last few weeks of very wet conditions then 'this is your time'. We approach mid-winter with such solid footing for cold synoptics that it should be a pleasure to watch the more unusual patterns being modelled in NWP and, interestingly, this continues to link in well with the majority if not all of the seasonal models with regards to how Jan and Feb and perhaps even Mar should progress. Winter is about to start... With regards, Matt.

"Background Zealots"? Hmm. Is this where we are at now, where those trying to unravel the complex task of forecasting get labelled as zealots? Either you know what that word means and are therefore genuinely trying to put the boot in, or you don't know what it means and perhaps shouldn't be using it. I see in general the knives are out today. Disappointing. Let's have a go at a broad response: 1. There are 2 areas of ongoing research that interest those with a passion for this kind of stuff. First is the GSDM theory first put together about 15 years ago by Ed Berry. The second is a greater understanding of stratospheric impacts on our weather, another fledgling science that has also been around for 15-20 years approx. 2. One of the challenges of both approaches is to try and understand the inter relationship between the two. GSDM is largely anchored on developments in the Pacific alongside momentum impacts created by the big mountain ranges - Tibet and Rockies probably most importantly, Urals also. Strat modelling tries to interpret the impact of vertical wave propagation and how the column of air above the arctic is shaped/squeezed/stretched/split (or not) by these waves. Tropospheric patterns feed into the strat and vice versa - so they are definitely linked - but an understanding of the links is still in its infancy. When Amy Butler tweets that the reasons for the failed SSW in early January are not understood (given models tend to under rather than over model the likelihood of an SSW) then you know you are walking in a world of grey. And that failed SSW and what has transpired instead has had a huge hand to play in how January has developed. 3. From this, we have 2 options. Label these areas of research as a waste of time, as likely to produce accuracy as the advice of a cat (!!), or we engage with what is going on and try and unpick it. CC is not making this any easier because CC is making a mess of analogues - the atmosphere and the overall climate just isn't what it was in the 1960-90 period and adapting to the pace of change and how it impacts forecasting is a challenge. 4. Some of today's posters would clearly favour the former. Don't bother trying to unlock the door to understanding because it cannot be done. Fair enough - but not for me. I'm not a nihilist and wish to continue to try and learn. Perhaps those who see chaos theory as the only answer to our weather should have a thread all of their own, though the thread would probably make for pointless reading. 5. Finally - you might want to read posts more carefully. Only the other day I acknowledged in a post that the Xmas forecast was a bust, and that the recent cold was shorter lived than expected. Reasons for both were set out, bust was advertised. Two successes at the same time, early Dec and the snap just gone. And it looks as though next week will bust too. There you go - is that clear enough? If you want the reason laid out again, reflective strat event. Not forecast, not spotted even by those with proper qualifications in relevant climate science. But this winter is not done yet, and I still see distinct opportunity for further cold in February and again into March. As a concluding comment, we are dealing in probability forecasting. No one will ever get to the stage where we say "in 10 days' time it will snow in London and 6 inches will fall and stick." Nonsense. We look at probabilities. And when dealing in probability a 95% chance does not always land. I see some criticism of the MetO today as well. Really? Those of you happy to criticise forecasting methodology and happy also to criticise (possibly) the most advanced national Met Office in the world and its choice of language are seeking a level of absolute clarity that is unattainable. If you have something to say that adds to the debate, say away. If your words are designed to tear, rip and demolish - silence is a better alternative.

Good God...its been my dad's funeral today..just a small service for close family as he didn't want a big fuss! This may seen insensitive me posting weather charts at such a time..but I will tell you this folks.. My Dad would have been just as excited as many of us and especially at the prospect of snow. Thanks Dad continue to smile down on me..and thanks for so many well wishes over the last couple of weeks. GEM is well...its a diamond

Thanks Briciu.. With a sad heart I report to say my Dad lost his fight on Wednesday...he passed away peacefully with closest family around him. I'm gutted. So many things to now sort out and at such a terrible time of the year. Hey..Xmas aint gonna be the same for me and I know that it won't be gr8 for many others on here also.. so I send you my best wishes. I think my Dad would have wanted me to keep up with my passion for the weather,as he never liked to see me unhappy..so I will try to keep up with the occasional bit of input. Don't get so downhearted over the models not really going for a cold and snowy Xmas! This is just a small part of the Winter duration....and we are here for the long haul. I've noticed the mogrep 6z ens have a fair bit of support for colder around the big day, if it's cold enough or are there enough disturbances in the flow for snow will be the big question. It's into the New Year where things could shake up... there are some signs of the strat taking a hit and just one look at that met update,with the hints of a more prolonged cold snap shows there models are perhaps sensing it out. In the meantime folks try and enjoy your Xmas festivities and remember that a milder Xmas period means nothing for how the rest of the Winter could shape up. God bless you all.

Hey folks hope your all chasing that next cold snap down.. it will come trust me. As many of you will be aware my dad has been poorly for some time now with parkinsons disease..in the last week he as become very poorly and is now entering that final stage of life..So we have palliative Care coming in daily to keep him comfortable..and god bless he is really comfortable and that's all I could really hope for. As his carer for many years and working by his side as a builder for many years..this coming Xmas is going to be the hardest me my brother and dear mother have ever endured. A lovely man who deserved non of this. But you know these things are completely out of our control. So I would like to send some some positive Xmas cheer and joy for all my netweather friends on here,and this includes the netweather team who do a great job with this site and even better job with this model thread. Some of you will also have a sad Xmas for numerous reasons..ie lost loved ones...missing families and friends you rarely see.....money problems and the dreaded loneliness! As always like every Xmas my heart goes out to any of you who encounter these problems. So all of you do try and enjoy your Xmas as best as you can...maybe that old friend or family member will turn up out of the blue. And if this can't be the case then here's hoping you all have a better 2024. It's gonna be a heartbreaker for me but I won't give in. And for the weather,perhaps colder next week....hopefully we can get that favourable phase of the mjo...as it will put pressure on the PV. And once again the zonal winds look encourage for the strat to take a hit,perhaps next month. Thanks guys and gals for a gr8 model thread this current year,which wouldn't be possible without your contributions. Live it large...and let's get some cold in Much love Matt.

Bom dia e todos I make no apologies for yet again re-pasting this sequence originally posted just prior to New Year, because it has become an even more focused roadmap. Not just for the upcoming 10 day period, but indeed confidence increasing as a blue-print for well into the second half of the winter: .................................................................................................................................................................................... With the Nino attractor phases fully engaged, the amount of westerlies propagated into the atmospheric circulation between tropics & extra tropics do, as you suggest, indicate a higher floor to the angular momentum budget in the 'lull' ahead of the next upswing as the MJO traverses the tropics during January. GWO Phase 4 is a good medium base floor level I would think. If we were to take a diagnostic template of GWO Phase 4 (and account for a likely return shallow orbit through phases 0,8 & back to 4) during an intermediate 'lull', then that very intermediate lull phase you describe will likely feature the return of a flat upper flow extending towards Europe. The difference to recently though with the Atlantic forcing will be the jet suppressed further south - and with a cold pool established then attritional forcing of lows against the blocking likely to be a feature. (This accounts for some of the thinking as expressed within my previous posts in respect of the sub tropical jet) With a cold pool established, any erosion from the south/west into NW Europe is likely to be attritional and not likely to displace cold pooling totally. Taking into account we are still now in the lag period for the effect of +ve momentum from FT/MT mechanisms c/o the recent tropical>extra tropical cycle, we are seeing the new convective signal come into the Indian Ocean. Sea temp anomalies are supportive of deep thunderstorm convection. This, allied to convection in the western Pacific, will generate further mean zonal west wind anomalies to propagate across the tropics into the sub-tropics. With the westerly wind additions generated in December still in the atmospheric circulation, total and relative angular momentum will increase sending the GWO back into a (potential high amplitude) phase 5 orbit. This progression & evolution suggests a strong -ve NAO with positive height anomalies shuffling between Greenland > Iceland and Scandinavia. Meantime southern Europe wet & mild under the sub tropical jetstream. Muito obrigada. Melhores Cumprimentos ...................................................................................... To update the template of this analysis: A very starkly high octane angular momentum budget is emerging and prolific within the global-wind-flow budgets. This translates to stockpile ammunition supply levels for deeply sustained poleward amplification eddies taking on veritable tanker sized reserves. Based on how much tropospheric led influence there has been on the NH pattern in recent weeks since the starting pistol was fired to destabilise the polar profile, these further poleward swathes of +ve momentum transport take on especially egregiously gargantuan proportions for future wholesale instability and implosion across the polar field. In this respect it is not hard to comprehend the latest sentiments of Amy Butler and how she sees the synoptic pattern imprinted The copied post referred to a baseline phase landing place for the Global Wind Oscillation. This baseline, ahead of the strongest wind-additions yet c/o eastward progressing high amplitude MJO wave back to the Pacific has remained higher than intermediate phase 4 (as discussed in the copied post) The latest GWO phasing, even under present lull stopgap at very low amplitude 5/6, reflects the remaining considerably high levels of +AAM anomalies within the atmospheric circulation as aggregate total AAM. (Phase 4 GWO would be more suggestive of flatter return of the jet and greater attrition from the Atlantic against blocking. (Though even this sharpens somewhat against late Jan/early Feb wavelengths) This GSDM wind flow budget situation is significant. More on this shortly. The GWO is a phase plot depiction of aggregate wind-flow within both the tropics (MJO related) and the extra tropics as a measure of how efficiently propagation of wind-flow is proceeding between the tropics & extra tropics. This matters, because it is a barometer for synoptic pattern (poleward) amplification potential and provides a diagnostic towards directional flux of wind-flow eddies. Poleward flux has now become quite supercharged What of the significance of this? As the intraseasonally driven MJO crosses the Maritimes at high amplitude, then very strong +ve torque mechanisms will be re-engaged to over top a system already awash with +AAM anomalies. The GWO likely to drill upwards into very high amplitude Phase 5/6. Taking into account maximum winter wavelengths, then this teleconnects ever more strongly to entrenched -ve NAO (under chaotic stratospheric diminution to spotweld a deeply -ve Annular Mode). How can this be visualised? The upcoming next cascade of westerly wind burst propagation into the extra tropics creates white water rafting within the sub tropical jet from the Equatorial Pacific downstream to the Atlantic -at the same time as the polar profile becomes riven with -ve mean zonal -ve wind anomalies. Defining solid roadblocks for southward directive of a deeply unstable thermal boundary. How can this in turn be visualised? With deeper upper cold air ensconced north of the polar boundary, this leads to feedbacks of entrenched surface cold with time to feed an ever starker thermal boundary, This encourages and emboldens larger progressions of numbers of kayaks slipstreaming below it. This translates to trains of low pressure undercuts - and it is not difficult to envisage the potential for high impact weather events to unfold in such a scenario. The kayak posse delivers an "atmospheric river" of saturated sub tropical air and a large jump of temperature into the upper teens for my part of the world well below the thermal boundary at the same time as in contrast... .... that is better left to the mercurial imaginations of any members who might be looking in from NW Europe. Putting all this diagnostic analysis together, it is hard to see anything other than a tanked -ve Annular Mode relationship dominating much of the rest of the winter. However, and as ever, further analysis is wholly prudent to document how proceedings unfold. Muito obrigada. Feliz quarta-feira

Just a little request to folk who are doubtful over telecommunications ie background signals please show a little respect for the members who spend time and have gained knowledge to enlighten the rest of us on this accepted form of meteorology. It all adds to enrich the forum and it would be a shame if unfriendly posts put these folk off from posting. I myself have gained much more understanding of what causes certain patterns to develop and i am 75years old but you can never stop learning about this great hobby if you keep an open mind.

References, as ever, crop up to x+y= responses to MJO phases in isolation. Again, to keep reiterating, tropical AND extra tropical wind-flow has to be assessed in respect of synoptic responses. There is no linear single interaction/response between the tropics and extra tropics without looking at directional flux of propagation of wind-flow as well, at this time of year, considering the interactions between the troposphere as a whole and the polar field. Eastward moving tropical convection waves (MJO) at high amplitude and set against very high +ve inertia within the aggregate global wind-flow budget is going to retain greater amplification tendency than a situation where angular momentum and angular momentum tendency are both suppressed. In this sense, and taking the present scenario where the MJO is moving through the so called "La Nina response phases" of the Maritime continent, it is not as simple as equating this to increased polar jet+ Atlantic westerly forcing = mobile +NAO pattern and breakdown of blocking patterns. The more extended period is fraught with so many pitfalls for NWP that I would genuinely stop trying to second guess the outlook for the last third of January. It makes sense that the Canadian lobe of the polar vortex will send energy towards the Atlantic but based on both the modelling within the polar field, which is highly unstable, and so much latent +AAM inertia within the aggregate wind-flow budget and then in addition to all that - another very sizeable push of inertia and momentum between the tropics and extra tropics during the period under consideration; there are so many hurdles for NWP to handle that extended ensemble data is next to rudderless at this time. This assessment is intended to be neutral in respect of the overall diagnostic - but it happens to be one that continues to keep cold blocked patterns in the ascendancy for N/NW Europe and tendency for the white water rafting within the sub tropical jet stream to be adjusted upwards within modelling suites day on dy. That doesn't inextricably mean another 1947 redux, but probabilities do suggest that attempted Atlantic breakdowns will be attritional and prone to be shorter lived, if they occur, rather than any wholesale mobile pattern change. Increased westerly mobility has higher probability for more southern parts of Europe - overall.

I hope the mods don't mind this but I would like to share something personal - After 8 years battling dementia, my sweet loving mum passed away last night. Her suffering is now at an end and she is at peace ❤❤❤ xxx

Just a quick post but the reason for the quick transition to the westerly type is, in my opinion, linked to the recent weakening of the strat vortex and how, within the lower layers of the strat/top of the trop are likely to behave following the consolidation of the vortex in the coming days. We can see this very well in the below four plots... The lobe of the vortex that has been bringing the extreme cold to N America is ejected eastwards over the N Atlantic and clearly to a locale where it then helps to drive the charts and patterns we are seeing for next weekend onwards, as the PV plots highlight very well and the vortex is then a more uniform system. Personally, the MJO through recent phases may also be helping the westerly push, but it is the above which is the key driver for the rapid breakdown of any HLB. Does this signal the end of winter after just a week of cold? - does it heck and don't let anyone tell you otherwise in this instance. The reasons for the potential/expected/likely return of blocking have been well documented by Tamara, Catacol et al in recent posts and it is likely to be a relatively short wait before further winter synoptics return by late Jan or early Feb onwards. All that aside as I mentioned the other day, for those who like the cold enjoy the week ahead. Kind regards. Matt.

The UK has had them between the UK and Southern Greenland. Apologies for the lack of Scandinavia in the current equation....Predicting the extent of blocking two weeks and more ahead defeats the best professional minds. let alone those studying the weather at at home. The elusiveness of snow in back gardens drives the unreasonable expectations within this thread. And it is very tiresome. As one who lives in PT, is not chasing or has no vested interest in any particular outcome and is purely interested in how the synoptic patterns played out then barring the suspicion that greater resistance to the end of the UK cold spell might have been stronger than it appears to be, the thinking since the last week of December when there was little sign of what was to come through the first half of January has played out very close to those expectations. And also the expectations of various others. I suspect alas nothing will ever be good enough for some on here. Including the task of finding a clairvoyant. Whatever the weather brings, hope all enjoy the rest of the season. Ciao. Melhores cumprimentos.

Premature ecmjulcation.

Tuesday 9 th Jan NOAA 6-10==15-19th, in other words inside the approximate date of ‘deep’ cold predicted some time ago.the 6-10 chart keeps the meridional flow across the chart, the shape is not the classic one but no signal for a developing mobile Atlantic, not on the 8-14 really. As usual the high +ve anomaly is much reduced but this is normal. IF this persists and the upstream becomes less conducive to another trough-ridge downstream then a change could be signalled but not so far and the 8-14 takes us to 17-23rd Jan? ECMWF has never been as +ve about the deep cold scenario and its latest output for 15-19 Jan is pretty similar. The 850’s show the -5C extending during the period to cover all of the UK by the 15th then it is moved north again so that by the 19th is is predicted be N Wales to about the Wash area. This as the 500 flow backs more west or even south of west with time. UK Met of course only shows surface and 500MB outputs for 3 days (13-15 th) but it looks to be on the same page for just prior to the two above from the 15 th. Ridge dominated both 500 and surface, over/just NW of the UK to a more trough dominated by the end of its run, again surface and upper air. So overall then, after a temporary slight warming at the surface and height, over the weekend a deeper colder spell seem likely to occur. The direction of flow, initially, being N’ly not E’ly. Looking on Extra at the skew-T diagrams, the colder air seems to start arriving over Doncaster by 14 Jan and much colder air continues to advect into the area from a N’ly direction as far as the run goes=T+180. All the time with limited convection, to around 6000 ft. So even well inland it is ‘possible’ for snow to fall. This is way ahead of any reliability from the synoptic models so patience is needed as to just what will happen over the UK regarding snowfall. Be that from showers and any possible troughs in the flow or from the Atlantic trying to move in giving more general ppn. To me it seems unlikely that milder air is unlikely to make much, if any, real progress against the cold airmass in the period under discussion on this post. All really interesting though to see just how the actual weather will turn out.

Hope the mods don't mind me dropping this message in here. I know its only Wednesday and Xmas is 5 days away but with so much going on right now and it being quite in here...and so many stressful things to go through in the next few days regarding my Dad's passing...ie...Chapel of rest and many loved ones and friends visiting us.....I would just like to thank you all again for being so kind with your messages of condolences that last few days. Many of you have taken the time out to wish both me and family well,and I know some of you have also had to deal with heartbreak over the last year or 2...and even @Dennis from Norway has dropped a message to wish me well...and others from across the North Sea also which is pretty surreal....and shows how much a tight fit community this is.. I cant name all of you right now as so many of you have sent me a message and I basically love you all. Xmas is a time for celebration for some,especially those with new families,and a time of great sadness for others who are so very much missing there departed loved ones. So my Heart goes out to you in any difficult times that you encounter throughout this period. I really do hope and prey that 2024 can bring you all the best life can throw at you...if not and your struggling feel free to pm me anytime and I will always be willing to try and lift your spirits folks. To summarise the weather we have some slightly colder air around Xmas but nothing to get excited about right now. But!! Our attentions turn to January and this is the time I feel things could change regarding the sypnotics and the strat. Keep the faith folks and remain a little patient. In the shorter term if you can then please do and try and have a fab Xmas period...life is short and we lose loved ones everyday...now could be the the time to Bury the hatchet if you can! Much love as always folks See you next Year!

The continual bickering, squabbling and oneupmanship in this thread is frankly becoming intolerable and needs to stop. I've had to remove many totally unnecessary posts this morning and deal with the reports submitted by other members equally fed up. Can people please be more considerate to their fellow members who want to log-in and head to the Model thread to catch up on the latest output and to read serious discussions about our weather prospects. Thank you.

Without going to into all the huge detail and nuances all over again (there isn't the time with other things to think about anyway) its worth reading exactly what is being suggested again. Not just by me but various others as well Bear in mind my own purpose is not to chase any particular weather type, but try to evaluate what is most likely to happen as to best of ability. And I do have a Portuguese head on at the same time. The analysis also bridges heading towards and into February and does not rule out, as said earlier, milder incursions for NW Europe. However, in the round, the emphasis especially earlier and then again a little later is probability weighted for cold blocked conditions to be predominate. This too, discussed in detail how and why previously. Also suggested was not to be reactive to each and every NWP suite and form instant conclusions - but evaluate them from day to day. One corner at a time. A very nice evening to everyone

Saturday 6 January re 500 charts etc The ECMWF looks to show deeper cold air advecting south of the 500 and surface ridging moving to around Iceland area. Date shown is 16 Jan, a week Tuesday! How long the upper ridge might last here is not clear as a largish upper trough is shown on the far nw of the EC chart. The NOAA 500 charts continue out to 8-14 with the upper ridge shown se-nw Greenland, the actual contour centre is about 55N 20W with the +ve height now shown as +390 DM over se Greenland on the 6-10 day chart. Similar on the 8-14, +ve is 270 DM. Upstream of this the pattern looks conducive to this probably extending some way beyond the 14 day period? This pattern has been consistently shown since about Xmas Day, obviously a developing set of charts but consistent in its direction and development. Just how long this pattern will last, how cold the UK will get, let alone will it snow is for the synoptic charts to gradually converge on what is likely. The UK surface and upper air only extend to the 12 th so obviously little of the above is on their public available charts. Given the consistency of the NOAA charts, now being picked up by ECMWF I would be surprised if deep cold was not being forecast by UK Met before next weekend! Egg on face possible! Usual charts below Climate Prediction Center - 6-10 Day 500mb Outlook WWW.CPC.NCEP.NOAA.GOV UK Met Office Fax Charts - UKMOMSLP Analysis and Prognosis WWW.WEATHERCHARTS.ORG UK Met Office . . Europe and North Atlantic MSLP analysis and prognosis charts

I needed to jump out of semi retirement for this post..hope the mods don't mind. When I joined this forum nearly 5 years ago I was sceptical of back ground drivers as I didn't really understand them..so I just played ignorant to it all....but I never disrespected any of the posters who shared this knowledge! As the years have rolled by the likes of Tamara..catacol...met4cast...chio..matt H.. eagle eye...(I could go on with this list as there's more of you) have completely changed my attitude to such a wonderful science,and the amount of work that goes into this subject with there posts is unreal! Do keep in mind many of the above are not professional! Yes you would think they were...they are that good at it,they simply have a gr8 passion for the subject and spend a hell of a lot of time studying,and then they pass this information on to us giving us the chance to learn something new! I for one know for a fact some of them in the past have come close to stopping posting due to non stop criticism...and I've actually talked one of them out of it privately on more than one occasion! Where do you think the Met get there long range forecasts from! A clairvoyant!! The tea leafs! It's all based on drivers around the globe and much of it is inputted into those monthly text updates.. yet when they're talking up cold and snow,everyone loves em! When they get it wrong they're useless! Get my point here! Let's all dismiss those drivers and base our forecasts on 4 gfs runs a day! One run shows Greenland blocking...the next a bartlett high! Exactly!!! Its not quite that simple. So I say to all of those that spend so much time bringing us these amazing insights with the teleconnections to please keep at it...most of us on this Forum want to keep learning from it. Keep the peace folks...no point in dismissing something you either don't understand,or are simply not willing to try and understand.

NWP playing the Hokey Cokey, but all roads leading the same way. Wave break is imminent, vortex right now is stressed and about to split, momentum set to be maintained for another week or so. When default westerlies are de powered modelling always struggles to get the small things “right” so just go with the flow and let the pattern unwind. Cold air is coming from the NE and will set up shop and we have a strong block that is going to be in play. And the AO is turning negative…all of which means cold for the foreseeable. Calmest I’ve felt all winter and I’m just enjoying the model ride. A moment to look further ahead. I mentioned before the belief that we will get enough from this pattern phase to keep the westerlies at bay once the less favourable MJO phases work their way through alongside the -AAM impacts that must inevitably follow a period of sharp amplification. Well - it’s good news tonight looking at these momentum patterns. First of all we can see that AAM is now climbing once again - earlier than I expected. Whether we end up with a bit of wobble in this gradient we will wait to see - I wouldn’t be surprised… but the fact we are back on the way up is great news and note that the dip we have just gone through is far less deep than the one that toasted our early December cold. This means the potential for a reignition of the amplification signal earlier than I expected, helped by a high orbit MJO that has stalled in phase 3, generally good news as 3 is better than 4 Overall this means wind flows have held on to a Nino imprint and from here I think we will be looking at finding a higher orbit again, especially if we get that +EAMT mid month. The plain language conclusion here is that it won’t be long before our block - which will inevitably begin to weaken in around 10 days’ time - will get reamplfiied soon enough to prevent a flat pattern reestablishing as happened in December. The MetO has alluded to as much today, providing the dual scenario of heavy snow and heavy rain hand in hand - code for that wonderful knife edge scenario stuff where some get big dumpings… and given the shape of the current pattern I think we can hold on to a decent amount of confidence that most of the U.K. will be on the cold side of any intrusions as we hit the final third of the month. From there, stronger block again. I’d go with our Greeny block subsiding towards Iceland, wedges deflecting weak Atlantic intrusions, movement towards Scandy and then amplified retrogression back to Greenland early Feb. It could all go wrong - of course it could - and if so I’ll flag it. But right now all remains on course.

Very well said C, as an ex senior forecaster for the often maligned Met Office much of what you discuss was barely seen in my days, an occasional very complex item in the more learned scientific magazines certainly nothing in practical meteorology. The science of meteorology has come a long way since then but some of you on here, yourself included, absolutely amaze me with your depth of knowledge. Keep going at it you will never, in my view, get a total answer but you will become more accurate as will the professionals. Thanks for all the hard work you and others on here do, way above me much of the time but well done.

You know something guys and gals I know some are sick of this long drawn out chase and especially if it fails to deliver snow in your areas..its been that much of a big thing...we even had a Scott Ingham day on when it lands.. but for me and I'm sure some will be getting sick of my long drawn out chases god forbid! But I'm growing in confidence that end of month into February could be much more potent and successful than the one we are heading into. Mjo on the rise again and further warming of an already weakened pv I feel could hit us the next time at the same time! For the met to favour blocking and NE/E winds shows we are getting not a lot of oomph from the zonal train.. displaced jet and solid El Nino backing coupled with EQBO are going to be strengthening to colder sypnotics option in my opinion! Next week good suprise snowfalls will crop up at short notice...BUT..dont be to downhearted if you miss out as I strongly feel this is merely just the first bite of a very big cherry..and guess what? This cherry is getting seriously ripe for the plucking..before sooner or later simply falling off the tree and exploding! A little fruit terminology for ya there folks In the short term do have a gr8 weekend be lamppost ready next week. Also I've got my Dad's ashes back today where he Will reside upon the mantle piece for as long as I live...hey dad love ya always and I know you would want snow as much as anybody...have a word with the big boss in the sky and see what you can do for us. Much love and respect as always peeps.

Fascinating model watching ahead. Long term trends are good, becoming a medium range model stand off. 144h is where it begins to get really interesting. Taking the top 4 performing models in order: ECM Atlantic approach angled steeply SE, wave break forced up ahead, low pressure previously sat over Scotland has dropped over Europe as pressure rises over Iceland. UKMO Less amplified over the Atlantic, different orientation of the Euro low and softer profile over Scandy. GEM Similar Atlantic shape to the ECM but again a different take on the Euro low and developments over Scandy. GFS 00z (taking from same data point) Similar wave break profile to ECM and GEM but another different take on the Euro low and profile over Scandy. In short - we have cross model agreement on the wave break (no surprise) but quite different outcomes to what occurs downstream of it and, indeed, the angle and composition of the momentum upstream causing it. Consequently anything beyond 144h is in Disneyland and we won’t know for a while yet just how much northerly traction the block will get nor the extent and angle of any undercut. We don’t get many of these knife edge, high potential scenarios in our part of the winter world so here’s hoping folk can enjoy the ride rather than play the doomsayer “told you so” card that often gets trotted out if a run shows less snow/cold than the previous one. There is a fine line between realism and pessimism, so let’s get it said now: yes…cold options in the U.K. are rare and often downgrade rather than upgrade. There is no wisdom or kudos for pointing this out ad infinitum. But when there is a chance - and there is a chance over the medium term - then let’s keep it optimistic. If it stays dry or westerlies win out then snowhunters can commiserate together (hopefully without the doomsayers playing that predictable card once again) but fingers crossed for some luck, some favourable alignment and some snow by the middle of the month. Remember Scotland has seen some good falls already, and the South got lucky in parts in early December. This has already been a better winter than many so fingers crossed it can continue. Broad scale drivers are favourable.

Ok, busy time coming up, and it's going to take an effort from the whole community to keep everything running smoothly: Please stay on topic and just keep to discussing the models in this thread. For more general chat, please use the winter chat thread, the moans and ramps thread, or the regional threads for localised weather discusssions. Please keep twitter style trolling and nonsense to twitter - don't bring it to the community Please report posts you think break the forum guidelines Please don't respond to iffy posts in thread Please enjoy the thread, the ups and downs and the drama - but please keep the real melodrama, toys out of prams and mega ramps to the moans and ramps threads. Thank you and happy model watching!

Completely agree. I wonder really why some of these folk are on this forum. In winter the momentum is always around the hope and search for rare winter synoptics and that should mean that the forum population are used to let down but optimistic by definition. Instead we have posters who see a single run that has slipped to a less cold picture - often at significant range - and who seem unwilling to contemplate the reality of the drivers that several of us try hard to explain and represent as accurately as we can. Of course the UK experiences let downs. We are an island on the eastern edge of a warm ocean no matter our latitude. But there is nothing happening at the moment that should do anything other than raise optimism. For my part I have not deviated from my confident sense that we are in a cold pattern for the extended. That was a bold thing to say yesterday, and partly driven I know by a desire to see cold, but I also try and keep my focus on what the data and the patterns and the likely predictions are putting out there (and I listen carefully to those who know a good deal more than me) and I dont see wet, windy and mild atlantic westerlies returning for a good wee while. I probably ought to qualify what I said by emphasising I am not expecting ice days for 28 days in a row nor am I expecting that all precipitation will be snow rather than rain. I'm not daft! But a cold pattern for an extended period is all I can see, with 22-29 Jan possibly the least cold part of that period, and unless something comes out of left field to skew the signals I think all will remain good for cold hunters.

My own take, given last night, and following up from a suggestion last week, explained how this weeks mid latitude Atlantic ridging was anticipated. I then expressed doubts about that regime's longevity at the expense of greater sub tropical flow. Tropical forcing now shows clearly increasing amplitude heading eastwards across I/O and renewed WWB's reversing the lull in momentum this week which led to the mid Atlantic ridge. This is important, because angular momentum tendency soaring heading into December, tied into seasonal wavelength changes and increasingly unstable tropopause boundary is ripe for high impact weather across Europe into December.That mid latitude ridging is set to become a road block to the polar jet as it becomes a higher latitude feature with undercutting jet flow. The expectation of renewed sub tropical flow was sooner than modelled up to today. What has been surprising today has been the even greater speed of return of that sub tropical flow. The suggestion of that stark thermal boundary in last nights post c/o a growing -ve NAO profile is being brought forward and provides great interest (of different kinds) for UK/NW Europe and for me down here in SW Europe. Confidence of undercut of blocking is exponentially increasing - though still a lot of detail to sort out. As stated just now, December has potential for high impact weather as cold air advection meets warm moist sub tropical Atlantic air. For all those of you in UK/NW Europe, I would look in the modelling in the extended period for lows to keep sliding along this boundary and bumping into increasingly cold air feeding in from the north and east.

Another fascinating year of studying the models comes to an end with another complete turnabout on the cards, but to be fair, a step forward from the usual “will it turn cold?” to “just how cold will it turn?”, which all in all, is not a bad place to be if you like that kind of thing Here on the 0z ECM ensemble mean, the transformation between day 4 and day 7, the second half of the coming week is astounding. How far north the high will ultimately sit by next weekend is still to be resolved. If this is right, it will be cold enough, but mainly dry, a very welcome anticyclonic period. Thereafter, it’s best just to look at the overall evolution at this stage. For hints about that, the 0z ECM control closely shadows the mean for pressure, a rise to 1030mb+ by around day 9, followed by a fall as the high sinks southeast, but doing so only to make way for a good chunk of the Siberian lobe of the PV to drop into Northern Europe. Day 8-15 Notably, not once in the T850 animation is there any flow from the west, Arctic air from the northwest at times, but no Atlantic sourced air. The core evolution surrounds a generally cold outlook with a trend towards even colder as January progresses. (If I may: It’s not anything I ever expected but I proudly accepted the offer of a role with the forum team as despite one or two rough edges that we all know we collectively have, I genuinely believe in the forum, its purpose, uniqueness and integrity. Already I see the challenge. Please help by staying on topic. Please try and avoid too many one liners, try and post a chart or at least refer to one, be as clear as you can in specifying details of model runs that you’re speaking of, avoid knee jerk posts that you just know afterwards you should have thought about a bit more before clicking submit. Don’t get wound up, report nonsense. If you have any questions or concerns, approach the team. I never realised how much work is done. Most of all, on a human level, please be kind. There is so much crap going on in the world, and we in our common interest, friendship and care are such a hell of a lot better than all of that. In addition to helping with the tremendous team effort of moderation, I will endeavour to maintain the same posting and reaction “presence” and try and make a good contribution to what we collectively enjoy so much.) Blwyddyn Newydd Dda i bawb, Happy New Year to everyone. Have a brilliant 2024.

Come on! You really can't be serious with this? Pessimism must be high to conjur up statements like this but unfortunately they just aren't true. For balance of presenting fact as opposed to dramatic headline grabbers .... here is yesterday's verified chart: Now compare that with a genuine pessimistic chart for this time of year, aka 2004: You can see the cause for pessimism diminishes somewhat.... and further to that, we have a more amplified MJO, phase 8/1, a pending significant weakening of the strat, and a host of other favourable teleconections which I won't go in to analyse given the great job that others do so well to explain to everyone and have been giving a running commentary on. Point being, there is plenty reason for optimism beyond the 7-10 range, its not your 2004 picture painted above. To keep the balance of realism for maybe newer members (as I suspect the seasoned will know that you threw a few statements out with no rationale, or indeed, maybe for the controversy) .... Here are 5 of the last 8 years for this same time of year: And here is the 3 remaining years of the last 8 years which have a slightly better viewing albeit, still don't show up the "abundant end of December northern blocking" Model fatigue can be a funny thing, but when you go back to looking for the basics, eg a roaring PV over Greenland, strong azores high or iberian high with a strongly positive NAO, or indeed strongly positive AO, a cold strat with zero warmings, an MJO in the COD and so on.... if you can tick all those boxes with no change in the forecast, only then will your statements hold credence. I envy the newer members this winter more than probably any before because the sheer amount of false factless based information being branded about this winter makes for a difficult read and gives a very poor foundation for learning.

For those looking further out, JMA monthly published yesterday for February. UK, as usual on this one, at 10 o clock. Otherwise the current situation is not what many on here would have hoped for. This GFS for tomorrow screams all kinds of wintry wonders: but closer examination shows that much of central and southern UK is stuck in a col, neither fed by the strongest and coldest winds from the N and/or NE nor quite in line for the channel runner. There is a day or so to go for surprises to turn up, and as we speak Scotland is getting pasted....but the snow hungry majority in the south are left gasping. Feels like rolling a double 1 and damnably unfortunate. Then comes week 2. 22-29 Jan approx was always flagged as a week of greatest concern because the impacts of lowering momentum would be greatest and the need to gave got a block cemented in a good place would be highest. But that double 1 effect may be about to land again. (is that like rolling 4 x 1s?!) The strat splits tomorrow and the zonal mean is much below average, even close to a technical (if very short lived) SSW - and we could be excused for thinking that there is little better context for ongoing northerly blocking. But look how steep the recovery is, and with little to no model disagreement. Back to average in a flash, and GFS largely puts the vortex back together again by the end of the weekend. So - what's happening? Factors leaning towards a cold and blocked outlook have had to work pretty hard to get our blocking pattern in place. Even with a favourable pulse of momentum, a good GWO orbit, and lagged impacts of an amplified MFO through the west pacific we have not quite got the block in place. Meanwhile, as soon as those signals fade into a period when it was well noted that things would get less automatically "good" for winter, we get a collapse of the pattern that is on the crazy side of fast. We go from the good chart at the top of this post to this within 4 days: No obvious lag here for the flatter MJO phases!! And a reforming vortex has helped support an atlantic pattern in double quick time. It is almost as though the wax wane nature of the atmosphere has been placed on a hill. To get to a blocked phase we have to sprint up the hill on our bike, in first gear, legs pumping and burning once at the top. But then to return to the starting point it is an easy cruise downhill, hands off the handlebars, freewheeling. Maybe this is CC in action. Or maybe it is just a reflection of some very poor luck for the coming week and the one after. I don't know. I guess in the end, other than to take the learning from it, I don't really care. It has never been easy to get snow to this country and 1988 to 2008 was a 20 year run of misery punctuated by a couple of good moments. Hunting those rare major snowfalls would be no fun at all if they came every year.....but it would be good if the fates could allow us 1 in 5!! This winter is not done. I read some guff on this thread that I find annoying, folk announcing the default return of a period of westerlies as though there is something wise and significant in doing so. Saying the UK will usually have westerlies and that the best way of approaching UK winter weather forecasting is to say "westerly" each time because you will usually be correct is both lazy and daft. I don't put my money on Ronnie O'Sullivan to win the snooker each time "because he usually does." I do it because I analyse the context and decide it is the most likely outcome....and I might still put £10 on a young outsider with half a chance of making it based on analysis and form, as per Luke Littler in the Darts. If Ronnie is ill the week before Sheffield I probably don't back him at all, despite the past run of success! And this is where we are right now. January 15, half way through winter. We had a decent start, a disappointing Xmas/NY and now sit in 4 days of frigid air but without widespread snow forecast. Bugger. Westerlies to return for a while. But the analysis doesn't change, and the weighted approach to appropriate forecasting remains. The next momentum cycle is underway, signalled by rising frictional torque as of a couple of days ago. The MJO will be back in the west pacific pretty quickly looking at model forecasts, and while the vortex returns to average it doesnt appear to launch itself into an above average phase. Read Tamara's work rather than mine on this - she expresses the technical aspects of wind flow much better than anyone else on here....but in essence we are set to have more wave action return, a meridional pattern embed and poleward flux that should bring blocking back to the table quite quickly. I haven't seen a seasonal do anything other than go with a negative AO for February and the combination of high momentum and a favourable MJO in a Nino year will bring things back. I had said 3-5 days of atlantic westerlies. That was based on the cold hanging on until Sunday as I had it down as a cold week....but it appears the cold is fading faster than we might reasonably have expected....so it pushes longer. I do think by the end of week 2, that's somewhere around 26/26/28 Jan, we will have a more favourable context back on the table....or at least sitting on the hot plate waiting to be served. Winter hunting in the UK has never been easy. C'est la vie. But we continue to look, and search, and roll those dice despite the fact that 80-90% of the time they don't give us what we seek.

For some, perhaps many, this is a final warning. This is not twitter. This is not a free for all where you can post what you want where you want. If you want to discuss the models, great please continue. If you want to post random, unrelated stuff, bicker, throw tantrums because it's not snowing or whatever else then this is not the thread and maybe not the place for you. So either stop and think about what you're posting or expect your posting privileges to be removed without further notice.

Nailed it. There are a surprising amount of egos for what is an enthusiasts/hobby forum by and large, and I mean that in both directions - there are also posters who will defend to the hilt that they were right to forecast something which didn't happen, when in reality sometimes we all just need to hold our hands up and say we got it wrong, let's all move on with our lives. But there is nothing more infuriating than seeing a lot of "I told you so" type posts when in reality they have forecast absolutely nothing. There's nothing wrong with coming onto here and not forecasting anything, in fact the overwhelming majority of readers and contributors to this topic do just that (I find myself doing more of that these days too owing to family commitments largely, though there is an increasing element of being put off from posting by some of the I Told You So-ers too). But when people do take the time to offer their thoughts, and particularly those posts which offer incredibly valuable insights, regardless of the outcome of the overall forecast we should not discourage such posters from contributing for the sake of some fast-tracked endorphin hit of saying "I told you so" to somebody you've never met on the internet, that in reality you would never say to them if you met them in person. This is not a new phenomenon either. Back to the earliest days of the BBC Snowwatch forums this behaviour was rife too. Maybe there is something intrinsically egotistic about a bunch of amateur weather forecasters (interspersed with a few pros too) all being brought together into the same space, but it does seem to be just a baked-in online behaviour nowadays. What I hope for more than anything is that these negatives never discourage people from posting overall and that the majority of members recognise this thread for what it is - one of the most fantastic learning opportunities available anywhere on the internet (really what the internet was intended for in the first place). I learned so much from these forums and this topic over the years in particular that it enabled me to become a paid weather forecast for a period in my life, something which I never thought would actually happen despite it being a (very cool and not at all nerdy, I'm sure you'll agree) childhood dream job. And what I would say from my slightly distant viewing of the forum this year so far is the learning opportunities, if you can overlook some of the bickering and peacocking, just continue to get better and better. Some of the recent posts from @Catacol, @Uncertainty, @Met4Cast, @Tamara, @Mike Poole, @bluearmy and many, many, countless others who I will have forgotten in that list are such a valuable, free resource of learning which I hope everyone really appreciates the true value of. You're getting daily free lessons in some of the most complex atmospheric/oceanic physics you could ever wish to learn about, all broken down into significantly easier to understand language which hopefully allows ever more people access to knowledge which otherwise is tied up in needlessly overcomplicated academic writing formats. So on behalf of everyone here to make sure all those countless, wonderful contributors feel a bit of love rather than pessimism and sniping, a huge thank you to all of the posters who have already or will continue to in the future keep helping hobbyists, enthusiasts and potential future meteorologists learning more and more about the weather on this tiny island (and way beyond) in the seasons and the years to come.

Let's strip this all back shall we and highlight the key points; Will it turn colder end of the week onwards? - Yes for many areas, the exception perhaps being far W and SW of the British Isles Is this a resolute, text-book Greenland block? - No, it isn't, it is an amplification of the N Atlantic pattern (Atlantic Ridge regime) as expected for several days Did the GFS 'win this one'? - Yes, IMO, it did. The consistency over the colder flow from the N, has been consistent from the GFS in some shape or form, EC poorest with the handling of this. Is widespread snow likely by the weekend? - No, the pattern is likely to be more anticyclonic than cyclonic, but still some 'give and take' in that Which areas could see snow? - Scotland and E England, primarily over higher ground, with little or no snow elsewhere Is this the first 'noteworthy' cold spell of the season for many? - Yes, it is likely to be so Without dredging up individual model runs and details, there is now high confidence for this cold spell to arrive as a cold front moves southwards on Thu into Fri. Logic dictates it will be in the N and E where the coldest air will be, less cold in the S and W. The 06Z GEFS highlights this now almost 'clean' transition and change in air mass, also worth noting that the 06z GFS and Control on the milder side into next week too. The long-term still carries a trend for a return to more Atlantic-driven weather, but the signal for the eastward propagation of the tropical signal and MJO is gaining traction for December and a potentially very interesting second half of December may still be on the cards. Despite some evidence for a strat and trop connection as well, there remains little evidence in NWP for an organised vortex either with certainly some 'unusual' goings on at the moment, in keeping with recent global extremes/variations/unknowns in past seasons too. Regards, Matt.

All valid points here and just replying to this so I can post some GWO analogs as requested by @Met4Cast about this expected rise in the GWO once again during the second half of January. As per the MJO plots mind, don't take a face value, but as you can see the overall likely outcome is obvious and supports all other ideas and information... No time at the moment for anything further, but yes, as per usual, be extremely cautious (everyone!) about individual model runs and variability, especially at longer lead times. The above quick set of bullet points is exactly what highlights the next 4 to 6 weeks and there is simply no reason to change all long-range thoughts, plus also the consistent signal from the Seasonal Models, for months, for the second half of the winter to be significant in terms of colder synoptics etc. Cheers, Matt.

Fantastic set of 12Zs. Shame the same cannot be said for some of the posts on this thread! The date has always been around 15th Jan for the cold spell to really start and that remains the case.

Going to be honest I am disappointed with the commentary on here these past 24hrs. So much so I couldn't be bothered to post. Lets begin by saying some of the model output these past 24hrs has been sensational and you could not draw any better charts for the UK. I would even go as far to say the best cold weather output I have seen. So when the bar has been set so high you are bound to see less impressive runs. However even the less impressive runs will deliver what many seek. The GEFS/ECM mean continue to be fantastic, especially the ECM. Some people have been referring to a W based NAO. The ECM mean at +240 does the opposite as to me a W based NAO is when the blocking backs W and allows SW,lys via atlantic low pressure systems moving in. The ECM mean is extending the block even further S. The ECM even causes a low pressure in the Atlantic to move W!! Lets also not forget the argument that all cold spells downgrade is flawed. Even recently some were suggesting the GFS would be right and we wouldn't even have an E,ly next week as low pressure was supposed to track NE into Iceland and our HP sinking over the UK. Moving onwards and at the moment even the transitional phase from the E,ly to a Greenland block is uncertain with regards to timing and detail and won't be resolved for another 72hrs. I could spend all day typing out various scenarios beyond this for mid Jan onwards. Overall a wintry outlook is most likely but could this be a convective N,ly or Bitter convective ENE,ly or will low pressure approach from the SW bringing a blizzard to some locations. Another option is low pressure in the atlantic phasing with the low that is moving S from the arctic, enhancing the bitter flow from the ENE.

Happy 2024 to everyone Not doing a full run down of the 500's but just posting the NOAA chart This has been consistent with this pattern for several days. The 6-10 is not often wrong and is more often right. Since Xmas day the intensity of the ridge and its position has developed steadily. The 8-14 keeps the pattern and about the same intensity of +ve heights in much the same area. It has gone pear shaped before but the probability is about 25%, at most. Even troughing over Europe is developed as the ridge develops. Will it snow and when-no idea, nor has anyone else. If you enjoy watching every GFS and other model churn out x times each day, fine but a better way if you do this. Is NOT to compare T+beyond 144 hours with the latest run, compare like with like, so 00 to 00, 12-12 etc. Until down to T+144, often keep doing it for another couple of runs. When that model shows consistency AND the other outputs continue to support that evolution, including sadly the much maligned teleconnections etc, then it is a high probability that that pattern will occur. Will it snow, just think back to summer and various models quite poor prediction of rainfall, both amount, and when and where. Not good quite often. To get snow you need about 8 additional parameters to be 'on board'. So try to be realistic PLEASE stop carping at one another it spoils the enjoyment for all of us. End of jh sermon, again Happy New Year, enjoy Net Wx.

Firstly folks I would like to say a massive thanks for all the well wishes I've received from many of you over the loss of my best mate and dad. I showed them to my mom and she was genuinely moved. Its given me a lift that so many show so much care and sympathy during difficult times. Your an amazing bunch and I really hope you get all the rewards you crave for. For the weather I said a while back that backend of December next month could change. And I'm seeing from a few ens that the pv could be about to be displaced maybe even a split....I feel your pain regarding the way things have gone wrong for this latter part of this month....but do remember we are not alone...The USA has been very mild and largely snowless also! No downgrade from Exeter regarding colder conditions perhaps becoming more likely next month. We have plenty of time and I feel the pattern will be completely shook up post Xmas. Once again...much love guys and gals...you've cheered up this rather sad individual right now. And I will continue to try and inject a positive vibe into this gr8 thread.

I blame Northwestsnow. I mean, since he had an interaction with some random bloke in McDonald’s while looking at Meteociel, there’s been a McFlurry of downgrades

As detailed fully earlier, it is easy to see why the models are looking to re-energise the polar jet. What still remains a question is how much flat west to east energy actually verifies beyond the meridian over a week away and how much instead is broken off. A lot of rationale has been given about the question mark over how sustained polar jet energy might be earlier today. The area between the UK and Iceland holds a key to a residual ridge and cold pooling that may well prove more resistant than modelling suggests 8 and more days away. Conceivably there is a route towards Scandinavia into the last week of the month and the start of a road back to late January blocking.

The extended period continues to look very problematic in respect of NWP to me. The MJO passing through the Indian Ocean has bumped up easterly inertia/trade winds and creating problems in the modelling with Pacific ridging and with the models gunning for booting up the polar jet downstream as a consequence. This at the same time providing insight into the modelling of the lobes of the polar vortex and the spectre of them fusing together. However, westerly wind inertia remains above average across the extra tropics and this presents a question mark about the Pacific amplification and downstream polar jet being over modelled. But most especially based on the passage of tropical convection quickly set to navigate through Phases 4 & 5 imminently during the period in question when the northern arm is being programmed to flatten the pattern. As the MJO hits the borders of Phase 5 the next starting pistol is renewed to ladder up angular momentum tendency. Putting all this together, a very squeezed timeframe for this sequence of polar jet modelling is only available in my book to complete, let alone sustain itself if it does. The suspicion I continue to have is that these poleward eddies that the models propose to increase polar jet momentum, will get sheared off and this whilst this still leaves a flat jet stream coming from upstream, the shearing off process will cut off the supply to the polar jet in mid stream and force it to backtrack into the sub tropical jet. Much the theme of discussion of late. That process, leaving some of the residual ridging between Greenland & Iceland intact and/or re-programming re-emergence of wedge type ridging and subsequent disruption of Canadian lobe energy in mid Atlantic. This leaves southerly jet kayaks to resume progress and changes the extended ensemble means that propose a flat westerly pattern across NW Europe & inflating Azores High. It will be very interesting (as I see it) to watch and monitor if this does actually transpire.

If I hear “west based -NAO” one more time..

The westerly wind anomalies which developed over the Equator early December onwards that have been fluxed poleward over the last three weeks c/o zonal mean transports cater for the upward spike in angular momentum. (This also paves the way for a cold pattern to return to N Europe later January into February - see further down). Relative angular momentum is up c/o fluxing of westerlies from the tropics into the sub-tropic. This, as we know, can be seen as a +ve angular momentum anomaly on the calculated aggregate tendency plot (shaded red) from 30N . Uniform extra tropical +ve mountain torque has driven tendency in relative angular momentum and the GWO well into phases 5/6 With the Nino attractor phases fully engaged, the amount of westerlies propagated into the atmospheric circulation between tropics & extra tropics do, as you suggest, indicate a higher floor to the angular momentum budget in the 'lull' ahead of the next upswing as the MJO traverses the tropics during January. GWO Phase 4 is a good medium base floor level I would think. If we were to take a diagnostic template of GWO Phase 4 (and account for a likely return shallow orbit through phases 0,8 & back to 4) during an intermediate 'lull', then that very intermediate lull phase you describe will likely feature the return of a flat upper flow extending towards Europe. The difference to recently though with the Atlantic forcing will be the jet suppressed further south - and with a cold pool established then attritional forcing of lows against the blocking likely to be a feature. (This accounts for some of the thinking as expressed within my previous posts in respect of the sub tropical jet) With a cold pool established, any erosion from the south/west into NW Europe is likely to be attritional and not likely to displace cold pooling totally. Taking into account we are still now in the lag period for the effect of +ve momentum from FT/MT mechanisms c/o the recent tropical>extra tropical cycle, we are seeing the new convective signal come into the Indian Ocean. Sea temp anomalies are supportive of deep thunderstorm convection. This, allied to convection in the western Pacific, will generate further mean zonal west wind anomalies to propagate across the tropics into the sub-tropics. With the westerly wind additions generated in December still in the atmospheric circulation, total and relative angular momentum will increase sending the GWO back into a (potential high amplitude) phase 5 orbit. This progression & evolution suggests a strong -ve NAO with positive height anomalies shuffling between Greenland > Iceland and Scandinavia. Meantime southern Europe wet & mild under the sub tropical jetstream. Muito obrigada. Melhores Cumprimentos

This post is going to explain the Stratospheric and Tropospheric circulation and link it with this current case study. This is a case study for my EPQ so any EPQ checker here, this is directly copied as I'm working on my EPQ not copied from here. During the winter months (more specifically, starting late November and going into late January) the Arctic is plunged into night throughout the whole day. Leading to large temperature differences between the mid-latitudes and the poles and so the jet stream is fired up into a polar-night jet that circulates around the Arctic. The jet still stays strong, especially in the stratosphere, through till early March. The strongest part of the polar-night jet is in the stratosphere and that’s important for top-down interactions with zonal anomalies. A stronger than average stratospheric vortex can push westerly wind anomalies further down into the troposphere. Similarly for the opposite but the processes that forces this is what we will be discussing in this research along with the extent we can attribute the stratospheric setup to the surface impacts by looking at what causes these connections and how strong they were in the January 2024 situation. The variability in the polar-night jet is importantly influenced by temperature anomalies, with diffusion of anomalous temperatures into the vortex, able to weaken the jet stream over the pole. The zonal jet for the pole (zonal jets being the different jets at different latitudes. The polar zonal jet is from 60-900 latitudes, the subtropical jet is from 30-600 and the equatorial jet is from 0-300 ,both north and south of the equator.) can be displaced or split under certain stratospheric polar warming conditions. Though the polar-night jet oscillation (PJO) is a low frequency intra-seasonal variable compared to a more varied tropospheric polar vortex, it is still influential, especially in certain circumstances. Stratospheric warmings can sometimes be strong enough to reverse the zonal wind and that is called a major warming when it does. That wind reversal pushes down into the troposphere through wave breaking. That wave breaking can cause reactions in both the tropospheric polar zonal jet but also the momentum budget and general patterning conditions. A major warming is linked with a negative (-VE) NAM (northern annular mode) or also known as the AO (Arctic oscillation) pattern where +VE (positive) pressure anomalies migrate poleward and –VE pressure anomalies filter down towards the subtropical latitudes. That is a perfect –VE NAM pattern though which doesn’t tend to happen, if at all, in the atmosphere due to the imperfect nature of the atmosphere. You can get lots of varied patterns associated with a –VE NAM pattern with the distribution of zonal winds and energy. The NAM is essentially just a representation of the atmospheric response to momentum being input, taken away or moved around the atmosphere. For what it’s worth, a perfect +VE NAM pattern also rarely, if ever, happens with an entirely zonal jet (both subtropical and polar) with the momentum budget always affecting the distribution of the jet. Given the SSW (sudden stratospheric warming) we’re studying, this isn’t necessary but a vortex intensification event has the opposite effect of an SSW. Neither setup shown on the AO images are perfect either, they’re just two strong events of both. The zonal response to a major SSW (assuming it can break down to the troposphere) is to weaken the zonal winds at higher latitudes through eastern enhancement propagating towards the surface and weakening the higher-latitude jets. This response is to increase amplification of the Rossby waves transversing the mid-latitudes and so the mid-latitude highs propagate poleward which pushes the Arctic air down towards the subtropical area, hence the –VE NAM response. Atmospheric Rossby waves are transverse waves like every other one, they’re just the connected high-pressure and low-pressure relationship. They’re also important for distribution of energy in the atmosphere, the poleward and equatorward movement of Rossby waves impart eastward zonal wind forcing where they propagate. Hence poleward waves are an important process for filtering cold air down from the Arctic towards where the subtropical jet propagated from. That’s what’s important for determining the tropospheric impact as that conditioning of the zonal jet can be more troposphere driven with the momentum budget and wave response. The ability of major warming PJO to affect surface conditions is well documented but minor warming’s effect on surface conditions is more event based. It depends on the tropospheric setup prior to the stratospheric warming and whether the troposphere to stratosphere (T-S) connections remain. Troposphere-Stratosphere connections The T-S connection is extremely important for the stratospheric variation with the transfer of heat flux through eddies forced by instability and in tropospheric Rossby waves, where they can ride along the waves transferring heat to geostrophically balance the atmosphere. Hence the eddy heat flux (EHF) acts for poleward heat amplification and carries equatorward cold suppression. EHF transfers heat vertically due to Rossby wave driving through zonal flow between atmospheric levels. This can be seen with an eddy-driven jet (EDJ) in the subtropics during times of large Rossby heat transfer. This EDJ migrates poleward with the poleward transfer of Rossby waves and thus EHF, which affects the balance in temperature between different levels of the atmosphere at the poles. The vertical temperature gradient diffuses the EHF upwards into the Stratosphere, transferring the Rossby wave. Assuming +VE heat transfer Stratospherically, the –VE zonal link with heat and zonal wind also transfers. However, Rossby waves cannot penetrate easterly zonal wind and so wave-breaking occurs, which is how easterly winds down-well after a major SSW. The stronger the temperature gradient where the transfer of EHF occurs, the stronger the diffusion occurs and therefore, the stronger the easterly zonal mean is imparted onto the zonal wind. A strong imparting of a Rossby wave poleward in the Stratosphere that completely reverses the zonal wind easterly is called a major SSW, whereas one that doesn’t fully reverse the zonal wind to easterly is a minor SSW. Stratosphere-Troposphere connection The connection between the stratosphere and troposphere is mostly done through wave breaking or wave reflection. There are certain setups favouring each of these, both are to do with the aforementioned Rossby wave driving. The –VE NAM imprint that can imprint on the stratosphere comes from a stretched polar vortex. However, compared to wave-breaking major SSW events, the zonal wind appears to be less of a factor. Only 1 in 5 wave reflection events (roughly) tend to be major SSW induced. However, it is harder to get a wave reflection event to occur during weakened vortex events. It’s almost exclusively stronger vortex events that are reflective when the reflection occurs in the lower-mid stratosphere, which is more frequent. Though in the upper stratosphere, reflectivity increases with a weaker vortex. Stronger reflection event past 10hPa become increasingly –VE zonal wind based. The onset of deceleration of zonal winds forms the reflective surfaces that forces the Rossby wave reflection and the heat diffusion vertically is distributed back surface-ward and are a strong force back towards the pre-conditioned state that the waves were forced from . The EHF re-follows the Rossby wave hence the stratosphere superimposes on the tropospheric state through both wave interactions but also the initial heat that’s imposed onto the wave state. However, that assumes that the Rossby wave hasn’t been forced to become barotropic in the stratosphere as a slow-moving wave packet would do, that disconnects from the quasi-stationary wave as it propagates meridionally, losing its initial base state. Then the wave and EHF connection dissipates as the heat flux is transferred at the same time as the baroclinic to barotropic link occurs. If the reflection can occur quickly enough for the wave to be quasi-base state, then the EHF should follow the wave back down. The strength of reflection is important for how much EHF is transferred back tropospheric-ward over the state that the Rossby wave packet imposes on. High reflection will clearly have a stronger impact upon returning to the –VE NAM base state that the wave driving likely was forced up with given the T-S links. It can influence the mean state of momentum transfer in the troposphere, important for the momentum budget distribution to tend to return to that initial driving state, especially with a stronger reflective response to induce that surface response. The wind shear response in the troposphere, important to show zonal flow against wave flow (horizontal against vertical zonal distribution. So, the zonal state forcing low pressures to form in the Atlantic when looking at influencing Europe’s weather, compared to the natural Rossby wave packet shear) and it’s in reaction to stratospheric influence. The westerly flow from the lower-mid stratosphere reflects and strengthens the polar vortex state, hence the shear showing both zonal and wave influence from the stratosphere. The wave energy can easily show itself based off the shear then because the difference in the western backing of the top of the wave between the heights showing the wave strength will also show up on shear. So the energy-shear link with Rossby waves for vortex disruption strength and linking it between zonal mean in the stratosphere imposing downwards is going to be important for understanding the case specific forcing. Case specific The reflective strength of the wave if it weren’t an upper stratospheric reflection of the –VE NAM state would be low, however, the upper stratospheric reflection means that we know that the reflection did at least have some strength. Given the weak zonal flow from the Rossby wave nearly reversing the upper stratospheric state, the thermal gradient would’ve been enough to force a large temperature flux to force that minor SSW which was a stretch and displacement of the vortex state. That stretch pre-displacement was what forced a reflective surface for the wave packet to reflect down off. The PJO occurs during a baroclinic wave setup, so the minor SSW is a clear showing that the wave hadn’t transferred to a barotropic wave yet and so the EHF was still wave-trapped remaining quasi-stationary and the pre-setup tropospheric state is still being reflected in the wave packet as it hasn’t changed its v distributed setup. Meaning that a perfect reflection would re-force the troposphere back to the forced state. However, as always, it won’t be perfect, so the response must interact with the setup it forced onto. Hence the strong –VE NAM response in the upper stratosphere shown will be watered back down as it approaches the surface, similar to the –VE NAM state that forced it. This is also likely due to the low wavenumber impact being stronger on the upper part of the atmosphere than the surface with a larger wavenumber at the surface being more normal so the deviation from average at the surface of the mostly wave-1 driven change, is translated to less at the surface than the stratosphere. The imprint of the reflection onto the troposphere can be seen by the linking on the time series, yet the surface driving of that through AAM wouldn’t be seen so it must be a balance between the two. This is especially given the built-up momentum pooled over the north Atlantic that could easily have been the main forcer of linear change in the evolution. So, the linear time scale of this is very important in determining the main force for change in the tropospheric state towards that weak –VE NAM. Normally, you’d say that the AAM and reflection destructively interacted to weaken the AAM signal towards just below average. However, this time, the Greenland high response being so high works linearly with the +VE AAM lag over the north Atlantic and the downwelling of EHF to re-imprint its own wave response. So, it is very possible that these waves constructively interacted to force such a strong Greenland high but then it becomes an almost impossible working out of surface drive against zonal wind drive. The stratosphere’s impact upon momentum though suggests that when looking at just the tropospheric response, the stratosphere would’ve influenced the momentum distribution throughout the northern hemisphere. This weakens the MJO influence because of the momentum being influenced more by the +VE EAMT event and stratospheric reflection. Therefore, we can work out through the Greenland high’s linear scaling, that the AAM and reflected wave constructively interacted to force the Greenland high. However, it is hard to link the AAM to the forcing of the Greenland high without assuming the stratosphere pooled momentum to force the wave. On the other hand, it is also hard to argue the other way with both working together assuming an in-phase wave evolution for a quite strong Greenland high to be forced despite only moderate strength of background signals with an out of phase MJO destructively interacting with the wave creation. The distribution of momentum being modulated by the stratospheric reflection however takes more of a precedence here because the +VE AAM event was relatively weak compared to the reflection taking place during a very weak zonal state. So, you could still make the argument that the stratospheric state is stronger of a force here because of how it projects onto the troposphere directly including previous events but because of the rising AAM, it’s hard to confirm it. Except using the zonal state, the zonal evolution clearly shows the surface development of poleward –VE anomalies pre-reflection reaching surface. The reflection forced onto the surface pattern and may have directed the pattern and strengthened the –VE zonal state at the surface but the AAM drove the initial wave. Initial wave driving was through momentum forcing but the stratosphere reflected the state it was initially forced from, hence the Greenland high was stratospherically influenced more than surface from the initial wave state of a UK-Iceland high. The stratosphere would have been what forced our potential prolonged cold episode then through anticyclonic wave breaking (polewards) and helped increase the strength of Arctic forcing projecting onto the –VE NAM state. This isn't done for anything specific but to show what forced this for future setup preferences. Especially in westerly lower Strat states w/high AAM as it can suggest a reflective tropospheric state is possible further down the line. Also, potentially suggests more Strat influence down the line w/the -VE NAM re-reflecting into the lower Strat from the AWB driving. AWB driving forced a minor SSW last year, however, the weak zonal mean zonal wind state after the minor SSW suggests to me that the wave should chip away at the lower Strat and could well split the lower Strat which re-works it's way back down for early February combing w/another rising AAM episode. So this is a long way of saying that we also need to keep an eye out for February because of the initial wave reflection we look to be getting at least 2 surface responses and given the driving AAM episode, I wouldn't be surprised if we got a 3rd reflective/wave-breaking and this ended up being a typical tripole major SSW reaction through multiple wave eflections forcing a weak SSWE from an initial minor SSW in the upper Strat. Potentially another setup from Strat-Trop connections to keep in case of a similar event. Away from the Stratosphere. We have now got a good consistent signal strong enough on the mean to show that we should be moving towards a retrogression towards Alaska w/the rising AAM and potentially another later mirroring of the wave reflection initially suppressed. Leading to the boxing in of a SW'ern USA low that forms as it works w/the retreating Greenland high. However, as the momentum budget redistributes likely due to either the re-reflection of the NAM state w/out a major SSW forced or if a major SSW is forced then it's through wavebreaking that the same reflection occurs. So the jets seperate and look to be slowly seperating well before the last few frames of the mean run. So we get another seperate jet situation w/favourably kinematics for the high just south of the Caribbean to be forced up again eventually as the momentum forces itself from jet to poleward forcing and so a mid-Atlantic block and/or a Greenland high is very possible. So going into February, we have multiple suggestions including the S2S models suggesting that there's a lot of support for a blocked pattern. The CFS weekly is showing the southern disconnected jet and the slow southern descent of - VE zonal wind anomalies into the 2nd week of February ish, hence the Greenland high support increases. The zonal component reflecting its state from Strat to Trop is a supported statement by the latest update w/a clear vertical suppression of the - VE zonal mean zonal winds through wavebreaking or reflection. Hard to tell here but if we can get wavebreaking from a major SSW it'd probably be better for total NAM circulation so easier for the prolonging of blocking w/less north American influence. Going into February and what I've said before is still represented by the low pass composite though it's still struggling to come up w/the north Pacific high w/Pacific trough (it still has the Pacific trough) bit maybe the signal for that wanes into February. However, the analog suggests that the atmospheric representation should be one similar to that of a La Nina probably phase 6/7 esque response rather than ENSO (most likely the Pacific trough signal supports an analog similar to this) which is perhaps a bit more transient than were it to be a La Nina signal and again, that Pacific trough is probably the signal for that. However, if we can get rid of that then we are really getting a good signal going through February. Thats all for now, might also look back at how the teleconnections did from late December to the current expected response. Given the 15/16 days lead time ish of the north Pacific ridge over the trough, I think both the mean and the teleconnections actually did well. I'm not great at current forecasts away from convection and sometimes using PV lobes to forecast small-scal precipitation but I tend to try to avoid it as people can tell.

Posted extract from 30 December: If we were to take a diagnostic template of GWO Phase 4 (and account for a likely return shallow orbit through phases 0,8 & back to 4) during an intermediate 'lull', then that very intermediate lull phase you describe will likely feature the return of a flat upper flow extending towards Europe. The difference to recently though with the Atlantic forcing will be the jet suppressed further south - and with a cold pool established then attritional forcing of lows against the blocking likely to be a feature. (This accounts for some of the thinking as expressed within my previous posts in respect of the sub tropical jet) With a cold pool established, any erosion from the south/west into NW Europe is likely to be attritional and not likely to displace cold pooling totally. Taking into account we are still now in the lag period for the effect of +ve momentum from FT/MT mechanisms c/o the recent tropical>extra tropical cycle, we are seeing the new convective signal come into the Indian Ocean. Sea temp anomalies are supportive of deep thunderstorm convection. This, allied to convection in the western Pacific, will generate further mean zonal west wind anomalies to propagate across the tropics into the sub-tropics. With the westerly wind additions generated in December still in the atmospheric circulation, total and relative angular momentum will increase sending the GWO back into a (potential high amplitude) phase 5 orbit. This progression & evolution suggests a strong -ve NAO with positive height anomalies shuffling between Greenland > Iceland and Scandinavia. Meantime southern Europe wet & mild under the sub tropical jetstream ................................................................................................ Cutting through the frenzy of intense reactive posting to NWP output, next to nothing has changed in the suggested outlook since this summary last weekend. In simple terms, NWP is teeing up the scenario of cold arctic air coming south through N Europe at the same time as momentum starts to return from the west c/o the sub tropical jet stream from next weekend. Based purely on attempted objectivity and looking at probabilistic solutions, rather than being wired to a desired outcome, the bold captions in the posted extract hold very true. This macro scale diagnostic is not a substitute for micro scale pinning down of thermal boundaries across a given part of the UK or any locality elsewhere in NW Europe, but clearly quite an envelope exists in respect of potential high impact winter weather outcomes where precisely this boundary sets up. For my own part of SW Europe, once the chilly static pattern of the coming week is dislodged from the end of the week, the envelope of probability is smaller in respect of the warmer moister sub tropical jet flow well south of the likely thermal boundary. That will be much welcomed in respect of turning down heating and removing the need for protecting tender plants & farm produce from any night time frosts. Longer term NWP means are next to worthless in the present scenario - the attritional boundary of the dense cold air advecting south and where it sets up against the returning jet stream cannot be pinned down at this stage and there is so much "noise" within the envelope that nothing can be discerned from such a wide blend.. But quite likely that any returning axis of vorticity to the Canadian side of the arctic will engage the sub tropical jet in such a way as to create an easterly vector above where the polar front eventually lies, and this as such define the high impact weather zone in itself. In this way, it might be worth watching how pressure orientates itself to the NE at such a time. But that is where a next updated analysis may be prescient. At times like these with seemingly complex factors at play, it helps to return to previous analysis and have confirmation that the main ingredients are panning out as anticipated. Boa tarde

I'm going to have a quick rant because I am fed up of seeing the same moans after an event like last night. First of all,I hope everyone is safe. It's pretty obvious scooting around the forums that there's been a significant amount of damage overnight and some areas are more badly affected than others. However, it's been a pretty nationwide event, even imby where we got away relatively lightly. However, I get really cheesed off with people who tell us this was a non event ( this is in general) and use it as an excuse to beat the models/metO/ other keen forcasters on here. Forecasting isn't an exact science and that's what makes it fun. The clue is in the name. So, if you got away Scot free last night, pethaps be greatful it didn't pan out as forecast. There's a lot of upset, cold and worried people across the country about to start a clear up/ attempt to get to work/ check in on families. Just because it didn't happen in your back garden doesn't mean it didn't happen. Be greatful and maybe extend a little thought and sympathy to those who are facing a pretty crappy day.

The developments are becoming very interesting in terms of the evolution of the N Hem pattern as we push deeper into autumn. Obviously, we are weeks away yet from the onset of winter and, as is always the case, the primary watch through November is on the development of the stratospheric polar vortex and how this interacts (or doesn't) with the tropospheric polar vortex. It should come as no surprise at all that if there is an organised sPV which then links and connects to the tPV into December there is usually only one outcome and that is an enhanced westerly, zonal flow, this is the "standard" evolution of the N Hem pattern in early winter. The likes of the MJO etc can help to alter this, a good example being the first half of December last year, but that is always the first port of call to keep analysing as November progresses. The +IOD event remains a troublesome feature mind, amongst favourable patterns and evolutions but we will just have to wait and see on that. Despite AAM having been persistently -ve for numerous weeks, the recent and consistent WWB near and just west of the dateline now seems to be having some impacts. We've seen a pronounced uptick in global MT and the recent tendency plot is 'off the scale', but does usually get watered down as each update progresses, but the broader development here is noteworthy. This links to what Tamara was mentioning with regards to finally a more gradual, linear increase in AAM and, importantly, this may progress and arrive at a time that has implications on the early winter patterns and the sPV too. The two dominant features are the -ve 850mb wind values near 60E, linked to the +IOD and now the more semi-permanent +ve 850mb winds (WWB) near and just west of the dateline, of which according to the Carl Shreck data is a noteworthy equatorial Rossby wave event. As we all know the MJO has been 'dead' for some considerable time now, the last noteworthy event way back in spring, clearly this links back into the evolution of the summer as well. It will be interesting to see how the MJO develops through the rest of the year as, eventually, a more pronounced development and event should make an appearance and that will also be key to some influence on the early winter pattern too. Generally speaking, the MJO is often more active during the winter months, than it is during the summer. As highlighted numerous times by Tamara over the years, a more Nina-like (-ve AAM) regime in winter is one that often supports more amplified mid-Atlantic ridges, which can build towards mid-latitudes. Amplification of this type, in winter, is often associated with inflated Azores high and with the usual tPV in play, which usually means a general +ve NAO pattern. There are also some links here to this stopping or inhibiting wave activity and flux that is required to help disrupt the sPV as well. The key thing towards winter is that a more atmospheric progression towards a Nino pattern (decline of easterly trade winds) means that the AAM pattern will lead to a greater risk of easterly anomalies at higher latitudes, bringing about a more amplified jet stream pattern. It is interesting to note that such a pattern has been in play of late, with a more dominant W'ly regime at lower latitudes, blocking, E'ly signal at higher latitudes. This is also why, over the next 7 to 14 days we see a dominant cyclonic pattern but one which is often set to see a more southerly tracking jet with high pressure trying to dominate at higher latitudes. Clearly, November blocking especially Russian and Ural blocking can have significant impacts down the line as well. The importance of the E'ly AAM anomalies at higher latitudes, compared with W'lies is exampled well if we look back a year ago on the below plot through Nov and into Dec - Note how through late Nov and into Dec, last year, the 50-60N region saw -ve E'ly anomalies dominant, being propped up by W'lies through the sub-tropics, overall it is this kind of AAM pattern that signals amplification and higher latitude blocking. If you then follow through last winter you can see how that pattern reversed with increased W'ly momentum being added to the mid-latitudes into the New Year as AAM fell to more negative territory - the key thing here, is that this year we could/should see the opposite occur with AAM rising. All in all, with the Nino/eQBO combination in play, some interesting signals already for a weaker vortex and, importantly, a likely progression towards a more +ve AAM pattern then the foundations remain firmly 'set' for a potentially interesting few months ahead, etc. Cheers, Matt

1070hPa over Greenland, menacing TPV to the East solidifying an already frozen solid Scandinavia, Europe directly into the freezer, ruined Vortex. Delightful !

Yeh Mike if I recall my first taste of proper winter was as a 7 year old in the 81/82 big freeze..there was never really any talk of background drivers then like we discuss now. A weather presenter would simply say high pressure is building over scandy which in turn will be dragging very cold air in from siberia..and I recall some real bruiser of heights around the scandy region back then. Countryfile forecast is about all we had to go on.(granted it was good as they were all met office trained and gr8 presenters) but like you say there was no way of us talking up or down the situation on social media like these days..we simply waited for it to come off,where as these days we simply wait for it to go wrong. Nearly 8 years old and waist deep in snow is when I got the buzz for it..I started drawing weather charts using an old atlas map,and putting all the symbols and isobars on...absolutely loved it...even run up a 200 phone bill as a 10 year old phoning around the UK for updates and weekly forecasts for different areas.. parents nearly killed me And at long last we are seeing some sublime output and I kinda have that 80s feeling all over again. Sorry for going off on one mods I'm having a nostalgic feeling looking back on those days.. Let's reel this in folks...and thanks for the commentary...its a complete blast.

Pfft. This is getting ridiculous. Getting bored of all the constant north easterly charts and anti-zonal flow. I'm hankering after some good old fashioned +NAO and a mild south westerly feed. Someone please find me a chart that shows the Fine Folk of Good Ol' Blighty what the weather round here is really all about. This really sucks. Cross model consensus of continental cold and snow is just so 1980s. Not.

This is genuinely one of the more bizarre evenings I can remember in here. You have the models showing things like this: And it's not good enough? I mean seriously! I get that there's not too much in the way of widespread snow shown at the moment, but a lot of the details aren't even close to being sorted out for next week yet. Yes, there's some discrepancy between runs and the ecm has gone a bit milder for a while tonight, but again that should highlight the difficulty of nailing down what's happening, rather than being seen as a definitive outcome. Perspective needed.

@Scott Inghamday. Vortex split right through the layers to 20hpa (I'll just show the 20) and vortex clearly very stretched. ECM signal for fast dropping overall windspeeds at this point midmonth is growing = little to no top down frictional support for a return of westerlies any time soon. Meanwhile, as I suggested might be happening a few days ago, relative AAM is on the way back up. Still negative, but climbing and by the time we get to the end of next week I would hazard a guess that the next spike in AAM will be in the wings. So....playing a game of lag: really cold jumps onto Scott's bandwagon about 15th Jan at a time when the vortex is gasping for air, and at the same point pacific momentum begins to climb again. Remember the Webb prediction of a +EAMT mid month too. This means reamplication roughly from week beginning 29 Jan. Can the cold pattern survive 2 weeks until we get that resurgence? No way to be sure, other than to look at the products available that are trying to calculate the physics of this. Not surprisingly EC weeklies read week 1 of this pattern as a definite cold to very cold NE for us by week 2 of the phase a much more muted signal but hardly one that looks mild. Tentative signs of breakdown? Maybe....but by golly it might be a very snowy breakdown and hardly a breakdown at all given NWP then sees a reignition of those Greenland Heights as we head into February. I'm going to call it now. I think we have week of cool down with the odd white surprise next week followed by 3 weeks of cool/cold/very cold with snowfall events along the way. I'm not sure there is much of a signal for anything else right now. How much snow falls and where it falls - well, who knows. But snow will be the theme. And 3 weeks might be pessimistic, because by week 2 of Feb the impacts of the next pacific wave will be in town, and the block will be getting fed plenty. NWP agrees for now.