Tamara

Which is what those who (try to) use them objectively continually stress time after time. I live in Portugal anyway with different weather entirely to think about. In all honesty the outlook down here is pretty good for the time of year. Some rain to help the national drought and also some pleasant temperatures to enjoy. Like many though, I still have an affection for the magic of snow, and it would be nice to see those back in the UK enjoying a share from one place to another. But, and its a big but. When it comes to trying to look at and analyse weather patterns it is self defeating to skew the diagnostic processes involved to a favoured outcome. But even attempted neutral objectivity can go wrong dealing with the complexities of the atmosphere. The current strongly suggested 8 to 15 day period being one good example of where that can happen. That doesn't mean the diagnostic processes are wrong, it is simply that the more you try to learn, and think you understand - the more you realise how much more there is to learn and that curveballs can still crop up at any time. With this in mind, it can be very resentful seeing parochial snow goggle types moaning because the so called "background signals" (I have grown to grind my teeth at this term!) have not made it snow outside their window and therefore "don't work"

This is a very good post from yesterday evening that appears to have been missed in the UK "it won't snow in my garden" cacophony. It looks like precise timing of movement of SPV lobes between Canada and Siberia scuppers the notion that the polar jet return was being overplayed following initial amplification that is now in progress. My niggle of the last few days has been about what should be immense wavebreaking pressure from the MJO progression through Phases 4 and 5 and then continued rossby wave driving on into the Pacific at the high amplitude expected - all being instrumental on diminution within the SPV in such a way as fracture the polar jet more sustainably around the time that this passage of tropical forcing is happening (circa up to 23rd Jan). Which is coincidentally very close to the period the amplified pattern flattens out. In that sense, whilst a cyclonic period made sense from upstream, following the ongoing current amplification response, the degree of polar jet return to follow didn't. One of those broken clock situations where taking NWP at face value at more extended time periods does turn out to be correct. Notwithstanding the override of the SPV lobe movements, I am still suspicious of any over muted response to the colossal momentum drive from the MJO induced tropics to extra tropics passage to the Pacific (and associated tangible effects of surging angular momentum) on any sustainable basis heading to late month and beyond.

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. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5009046

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.

For quite some time, in anticipation of the blocked pattern and sub tropical jet, I have used the word "attrition" in respect of the eventual attempted breakdown. I am always open to evidence that changes the picture to reflect the extended modelling but it is equally my natural instinct to question anything that gets taken at face value. This second half of January has too many aspects that at present make me question the degree (at least the degree of latitude) that the Atlantic returns. Thereafter there seems no evidence on the other hand to question a reload of blocking (caveat being how much this does actually break down fully in the first place). Everything points to AAM soaring regardless heading into, or just before, the last week of January to early February and with the GWO likely at high amplitude in the Nino attractor phases under stratospheric diminution, the representation of height rises in a spectrum between Greenland, Iceland & Scandinavia, alongside a fully brooked sub tropical jet - and so therefore good vindication of the latter winter seasonal modelling. This is one modelling outlet that does make complete sense at this time. Sometimes its the case that the conclusion point is clearer than the path towards it. Which does sound rather odd, but there we are!.... Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5008841

For quite some time, in anticipation of the blocked pattern and sub tropical jet, I have used the word "attrition" in respect of the eventual attempted breakdown. I am always open to evidence that changes the picture to reflect the extended modelling but it is equally my natural instinct to question anything that gets taken at face value. This second half of January has too many aspects that at present make me question the degree (at least the degree of latitude) that the Atlantic returns. Thereafter there seems no evidence on the other hand to question a reload of blocking (caveat being how much this does actually break down fully in the first place). Everything points to AAM soaring regardless heading into, or just before, the last week of January to early February and with the GWO likely at high amplitude in the Nino attractor phases under stratospheric diminution, the representation of height rises in a spectrum between Greenland, Iceland & Scandinavia, alongside a fully brooked sub tropical jet - and so therefore good vindication of the latter winter seasonal modelling. This is one modelling outlet that does make complete sense at this time. Sometimes its the case that the conclusion point is clearer than the path towards it. Which does sound rather odd, but there we are!....

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. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5008660

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.

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 Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5007593

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

Two things: The energy distribution on UKMO is much more separated upstream than GFS and hence tendency towards a more split flow/ sub tropical jet is emphasised. Also the -ve inertia (-ve zonal wind pockets) at higher latitudes is modelled much more and the amplification inertia within the extra tropics has less low AAM bias than GFS - which piles all into the polar jet and ends up with the scribble in the extended period that it does. It sees a brick wall but models/simulates attempting to drive straight through it anyway. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5007273

Two things: The energy distribution on UKMO is much more separated upstream than GFS and hence tendency towards a more split flow/ sub tropical jet is emphasised. Also the -ve inertia (-ve zonal wind pockets) at higher latitudes is modelled much more and the amplification inertia within the extra tropics has less low AAM bias than GFS - which piles all into the polar jet and ends up with the scribble in the extended period that it does. It sees a brick wall but models/simulates attempting to drive straight through it anyway.

Based on the modelling of the huge gyre of vortex across NE Europe and that part of the arctic to retrograde in tandem with the Greenland amplification it makes sense that height anomalies will respond accordingly to a more cyclonic regime. But is is within that regime with embedded upper and increasing surface cold across N/NW Europe and remaining pockets of -ve zonal mean -ve zonal winds at high latitudes that considerable resistance must surely make it difficult for flat westerly inertia to cleanly navigate the road blocks. Additionally, it will not be long before a further push comes from momentum transport from the tropics into the extra tropics to replenish the sub tropical jet stream and equally further poleward amplification. Putting that together, disruption of vorticity is more intuitive to expect than positively tilted wholesale displacement of -ve higher latitude inertia & its associated dense cold air. NWP is not ignoring the tropospheric diagnostic and not battling it. NWP doesn't lead the diagnostic. It is rather led by it, but trying to decode a lot of complex factors that do not align with the traditional westerly gyre of a +ve AO and NAO. Lastly and finally on this, the term "rudderless" refers much more to collective smoothed ensemble means. It is of course possible to look at individual clusters of ensemble solutions to see which are maybe in the ascendancy or vice versa. But even here, if the overall modelling is blindsided by a false signal or jet stream bias calculation at a given distance, then members within the clusters will also reflect that inaccuracy. They are best looked at as a snapshot in time of progress (or otherwise!), and not any definitive prediction at that given distance. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5007043

Based on the modelling of the huge gyre of vortex across NE Europe and that part of the arctic to retrograde in tandem with the Greenland amplification it makes sense that height anomalies will respond accordingly to a more cyclonic regime. But is is within that regime with embedded upper and increasing surface cold across N/NW Europe and remaining pockets of -ve zonal mean -ve zonal winds at high latitudes that considerable resistance must surely make it difficult for flat westerly inertia to cleanly navigate the road blocks. Additionally, it will not be long before a further push comes from momentum transport from the tropics into the extra tropics to replenish the sub tropical jet stream and equally further poleward amplification. Putting that together, disruption of vorticity is more intuitive to expect than positively tilted wholesale displacement of -ve higher latitude inertia & its associated dense cold air. NWP is not ignoring the tropospheric diagnostic and not battling it. NWP doesn't lead the diagnostic. It is rather led by it, but trying to decode a lot of complex factors that do not align with the traditional westerly gyre of a +ve AO and NAO. Lastly and finally on this, the term "rudderless" refers much more to collective smoothed ensemble means. It is of course possible to look at individual clusters of ensemble solutions to see which are maybe in the ascendancy or vice versa. But even here, if the overall modelling is blindsided by a false signal or jet stream bias calculation at a given distance, then members within the clusters will also reflect that inaccuracy. They are best looked at as a snapshot in time of progress (or otherwise!), and not any definitive prediction at that given distance.

No. In a nutshell. There is such a wide envelope within those means, and, as outlined the overwhelming suspicion that the jet stream will keep tending to align to send too much polar jet energy on a flat eastward path, that the best that can be said is that assessment of these means should sensibly be incremental day on day. This, much rather than the folly of instant face value extrapolations. Extended means are especially volatile, over smoothed, and subject to considerable further much more detailed evolution than they are within much more traditional zonal winter patterns. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006967

No. In a nutshell. There is such a wide envelope within those means, and, as outlined the overwhelming suspicion that the jet stream will keep tending to align to send too much polar jet energy on a flat eastward path, that the best that can be said is that assessment of these means should sensibly be incremental day on day. This, much rather than the folly of instant face value extrapolations. Extended means are especially volatile, over smoothed, and subject to considerable further much more detailed evolution than they are within much more traditional zonal winter patterns.

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. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006946

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.

January/February 1978 comes to mind with a match to present GWO/GSDM expectations and also the bulleted points. The diagnostic as discussed in my own post earlier today in considerable details suggests a sustained Nino attractor phasing principally focused on Phases 5 & 6 (high amplitude) set against stratospheric diminution as we head to the late Jan & Feb period. The GWO spent much of February 1978 in these phases and the Icelandic/Greenland roadblock and very active sub tropical jet are well known for their high impact conditions for those of you in the UK. In this respect, take note of the disrupting jet stream of January 78 as arctic height rises forced the pattern. While each situation is taken on its own merits and never is exactly the same, especially in the changed climate background these days, it is still worthwhile taking present NWP into context on the basis of the forcing similarities Boa noite. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005882

January/February 1978 comes to mind with a match to present GWO/GSDM expectations and also the bulleted points. The diagnostic as discussed in my own post earlier today in considerable details suggests a sustained Nino attractor phasing principally focused on Phases 5 & 6 (high amplitude) set against stratospheric diminution as we head to the late Jan & Feb period. The GWO spent much of February 1978 in these phases and the Icelandic/Greenland roadblock and very active sub tropical jet are well known for their high impact conditions for those of you in the UK. In this respect, take note of the disrupting jet stream of January 78 as arctic height rises forced the pattern. While each situation is taken on its own merits and never is exactly the same, especially in the changed climate background these days, it is still worthwhile taking present NWP into context on the basis of the forcing similarities Boa noite.

Typo indeed. Thanks for pointing it out In respect of the pattern, I am very interested in the stratospheric lead as the second half of the winter approaches and under the tropospheric considerations as laid out again in todays summary and which other GSDM analysis from @Met4Castand @Catacolare equally observing. There is so much poleward tropospheric ammunition to hand, it does make one wonder how the polar field will respond in respect of persistent diminution bombardment. There is an argument for suggesting that too much forcing can actually alter usual pathway responses. But the GSDM diagnostic fully evidences the latest seasonal updates such as from Glosea. The kayaks and shuffled polar roadblock are emphatically there to see. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005206

With the atmosphere now very tightly coupled to El Nino, +ve AAM westerly wind burst anomalies propagating from tropical convection traversing the tropics to the Pacific either usually manifest in A) downstream blocking patterns across Europe in stable Annular Mode patterns (and other countervailing aspects that discourage poleward momentum transport) or, B) close to Iceland and Southern Greenland as under the present destabilised polar field and as assisted by E QBO Brewer Dobson circulation of tropical tropospheric air that ascends the stratosphere and augments poleward propagation of extra tropical +ve torque mechanisms and hence perturb the polar field and lead to an HLB outcome. So though this is a deliberately generalised categorisation (and each situation has to be taken on its own merits) - as already indicated, clearly this winter is meeting criteria B. The present alert system seems well primed ahead of next weeks cold air advection. I cannot see this changing for a while yet based on, (and as my own little "at home" posts have been giving heads up for some time) there being still such an envelope of probabilistic outcomes for the first high impact weather zones and where the kayak procession first choose to navigate. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005280

With the atmosphere now very tightly coupled to El Nino, +ve AAM westerly wind burst anomalies propagating from tropical convection traversing the tropics to the Pacific either usually manifest in A) downstream blocking patterns across Europe in stable Annular Mode patterns (and other countervailing aspects that discourage poleward momentum transport) or, B) close to Iceland and Southern Greenland as under the present destabilised polar field and as assisted by E QBO Brewer Dobson circulation of tropical tropospheric air that ascends the stratosphere and augments poleward propagation of extra tropical +ve torque mechanisms and hence perturb the polar field and lead to an HLB outcome. So though this is a deliberately generalised categorisation (and each situation has to be taken on its own merits) - as already indicated, clearly this winter is meeting criteria B. The present alert system seems well primed ahead of next weeks cold air advection. I cannot see this changing for a while yet based on, (and as my own little "at home" posts have been giving heads up for some time) there being still such an envelope of probabilistic outcomes for the first high impact weather zones and where the kayak procession first choose to navigate.

Typo indeed. Thanks for pointing it out In respect of the pattern, I am very interested in the stratospheric lead as the second half of the winter approaches and under the tropospheric considerations as laid out again in todays summary and which other GSDM analysis from @Met4Castand @Catacolare equally observing. There is so much poleward tropospheric ammunition to hand, it does make one wonder how the polar field will respond in respect of persistent diminution bombardment. There is an argument for suggesting that too much forcing can actually alter usual pathway responses. But the GSDM diagnostic fully evidences the latest seasonal updates such as from Glosea. The kayaks and shuffled polar roadblock are emphatically there to see.

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 Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005089