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Tamara last won the day on May 11 2019

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  1. Suffice to say, it won't be a surprise to hear me say that I support the comments that Tom has made related to the NAO. I did promise that I would stay out of discussions in this particular thread yesterday, so I am not going to add any of my own illustrations, based on official reanalysis data, of NAO definition to this debate for fear of, however unwittingly, adding even further to divisions - but I would just like to say this in light of your good post @CloudIridescenceand against the background of the repeated posts that Tom has made to try to stick up for himself. Tom was his own worst critic last winter with his forecast, and which did follow majority consensus for cold potential and increasing -ve NAM domain through the winter. The general debate through the winter was probably one of the best I have witnessed anywhere previously, and equally participated in myself, since right back when I started to learn about weather patterns .There was detailed discussion throughout the progress of the winter as to why the macro pattern was not according to consensus opinions, both amateur and professional (including seasonal model forecasts), and with persistent expectation that this would "rectify" to consensus through time. That timetable came and went, and the SSW with it. It is documented that Tom among many others went out of his way to critique his own forecast, as part of his own contribution to that season, and at the same time additionally also went out of his way to answer questions from others that were generally aired. On that basis, and meant in the nicest way, it is harsh to impugn him for being "stubborn" and not admitting he is somehow wrong regarding his forecast this year (only a few weeks in) . Putting aside those of us who agree with him thus far, and indeed looking ahead as well, and the much larger number evidently that do not do so - in my opinion he doesn't deserve to be singled out and equally notwithstanding some of the critical comments that he/some of us made related to strong biases and over-popularity for obviously biased viewpoints ad and which do not bear anywhere near the same level of hard scrutiny.. My own views on this winter are well known and accord with those of Tom, but this is not to discuss me and is simply to try to be fair where fair is due to someone who has made an "official" forecast. One third of winter is almost up, with two thirds remaining - it is probably prudent that everyone, including Tom, is given a chance to have judgement suspended on their forecasts/opinions this early otherwise the discussion will not make it to the end of winter. In stark contrast to the courteous and vibrant debate last time that went all the way to March and with no negative attitudes about sensible weather not providing anticipated excitement and equally with very very few negative personal attitudes and agendas. But also perhaps fair that trust is put in Tom that he is genuinely not being bloody-minded in defence of his analysis and predictions to date - simply exercising his right to be self critical at the right times, but not, however, when he is being made to feel he has to bow to pressure due to having a minority opinion that conflicts with others because it is not a "cold forecast" It is this that is behind the recent issues in my opinion on a larger and wider scale. No-one posts and goes against popular opinion to be difficult, obstructive or to troll others - it is simply providing objective opinion. Much as happened last winter - the difference is that most everyone (including myself) was on a very similar page towards an outcome that a majority happened to want to see (and despite the same personal neutrality of outcome(s) that I hold this year as last time)). Self evidently it is clearly much harder to apply the same principles of respect and fairness when opinions are more split and tribal views develop and intervene, And with a very broad brush post completed that deliberately avoids getting into technical details to further muddy a teleconnection debate that is going round in circles, I will, as indicated leave this particular thread to proceed accordingly
  2. Thankyou for the comments 1) I wasn't grandstanding in any way, - simply standing up for comments I previously made and which most other folk who use this site are (usually) respected for doing so. 2) The first third of the winter is going to see a +ve NAM domain evident taken in the round (despite the local departures within the NE US for such a wider pattern)- which was the essence of those early posts and which I did try to suggest are obtainable within personal profiles - and was added as means to deter anyone trying to dissect the greater thrust of the post. I regret not being able to micro forecast snowfall from across a wide Atlantic, but then I also know this is not my personal priority. 3) So my emphasis is not IMBY snowfall, but focus on broad-scale hemispheric pattern. I live in the UK, and not the NE US - but sure wouldn't expect anyone in the US to base their own thinking with any consideration towards the micro scale corner of England I live in. As much as I realize I am posting on a site that caters specifically of the NE US., it remains the case that nevertheless I post from a NH perspective wrt global wind-flow effects on both Pacific and Atlantic patterns. With that in mind it also rubber stamps point number 2) in terms of the overall macro scale hemispheric return for this first third of winter. I don't personally see any conflict within my rationale there. 4) I therefore stand completely by the early prognosis of lack of sustained unstable polar profile and unpropitious for sustained -NAO and see no reason to question verification vs issues of sensible weather variance - irrespective of IMBY NE US considerations.. 5) I freely admit I don't pay the same attention to cold and snow outcomes as most do on this thread and will have to be forgiven for having the detached view I do when it comes to overviews of hemispheric patterns. I have seen the snow pictures on the observations threads in recent weeks and appreciated their beauty, but my perceptions of weather patterns are not dictated by "snow myopia" 6) I acknowledge none of this makes my posts popular, make me seem out of touch with the IMBY population of the thread and in recognition of that will attribute relatively few "likes" due to the apparent detachment and lack of micro scale focus of my views - but then, once again, as I also tried to covey in my post -,I am not interested in popularity contests and simply say it as I see it. For better, or worse. 7) As stated at the conclusion of the main post - I am not partaking further in discussions on this thread this winter, and I think these exchanges that emphasis the very different priorities and the cross purpose, very much illustrate my rationale behind not doing so. On that basis this type of issue will not re-occur.
  3. Thinking has remained very quietly consistent since October, and continues to accord with others - who are equally consistent with likely progress into January as per the first third to half of season evolution as originally envisaged . Its always easy enough to re-trace posts within independent profiles, that simultaneously concur with others on a similar page. The record strength +IOD and very slow weakening of the w/QBO in the transition process are being too progressively discounted c/o ebullient over eagerness to be buried in snow avalanches. The reality has been, and continues for the foreseeable to produce no more or less than transitory amplified mid latitude sub tropical ridging profiles and equally ephemeral weak perturbing of the polar field, with interspersions of faster Pacific jet flow phases - as distinct from characteristic slow moving and more enduring blocking features as a product of sustained -ve zonal wind anomalies at higher latitudes. Mindful of previously expressed emotive irritation from a few when it comes to bias discussion - to be honest, I initiate from a starkly different inception point of application and approach to the populist twitter>board conveyor that is so sassy these days - and which exhibits a proclivity to ramping up saleable outcomes to garner maximum pique of interest and profile views. Largely attributable to selectively assenting to NWP extrapolated perceptions of diagnostic signals that appear to convincingly assign solutions to "when is it going to snow" scenarios. My particular interest, more mundanely perceived no doubt, exists within the beige layers of contemplating solutions that converge around all potential probabilistic outcomes, and irrespective of accordance with any bias solution. So some GLAAM, but without much applied glam then.... Consideration continues of wind-flow momentum responses within the auspices of available bandwidth the atmosphere has capacity for poleward momentum fluxing at a given time as determined by gauging the most likely seasonal evolution of BDC assistance of ozone transport capability to disrupt stability within the polar stratosphere - hence heightened planetary wave-breaking effectiveness potential within the troposphere/stratosphere layers Through objective diagnosis, it is possible to pick out dubious "red herring" modelling that will inevitably skew perceptions in the medium and longer term. It is far too easy and predictably common-place to cherry pick a computer model of choice at any given time if it appears to support the outcome the individual is looking to artificially fit data diagnostics to Increased susceptibility of slow moving blocking and decelerated zonal wind deposits at higher latitude c/o smooth passage of progressive QBO transition and rapid weakening +IOD allowing more dominant +ENSO Pacific convergence of tropical forcing is one main wish-cast mechanism towards the bias solution this winter - but those who have perceived the longer range of the time envelope, and/or are neutral of outcomes (like me) largely are seeing the slow act on the stage play out with an intermission included. Verification states of the NAM so far this season point to a greater +ve outcome vs the overstated diminution predictions via populist twitter>board chatter that ramp up hype and provoke over-expectation. Though there are some early winter similarities to GSDM budget and associated Global Wind Oscillation choreographing of the atmospheric wind-flow profiles, the QBO phasing transition towards easterly continues to show a distinctly retarded progression compared to the likes of late 1986/1987 which had already made easterly phase transition, and is apparently I do believe, the latest buzz analogue to sustain the anticipation of the next incoming freeze - which continues to remain "just around the corner". 1986 8.74 10.15 11.96 9.11 3.56 -2.15 -5.25 -9.60 -10.21 -9.60 -8.01 -10.51 1987 -9.93 -11.37 -14.23 2019 9.02 9.25 11.82 13.36 14.59 14.36 10.96 9.97 8.25 7.27 5.07 (to date) QBO Calculated at NOAA/ESRL PSD 30mb zonal wind at the equator, zonal average For info https://www.esrl.noaa.gov/psd/data/climateindices/list/ Based on the different base state conditions and distinctly weaker +ENSO profile than apparent heading through winter 86/87, the benchmark for tropical>extra tropical atmospheric Nino attractor phasing such as occurred then is less. In the nearer term, an opportunity for a spike in angular momentum does indeed exist c/o westerly wind bursts in the CPAC during festive week... ...and is likely to lead to weakening of sub tropical ridging pattern following the Christmas period with accordant fall in pressure downstream in the Atlantic and reversion to Wave 1 pattern of which a lot of emphasis is being placed wrt sustained action leading to full stratospheric diminution in January. I presently remain pertinacious to longer timelines related to anything close to such attenuation within the polar field - and by association equally persist in not overly dismissing the legacy of the w/QBO and its lagged constrains on the effectiveness of any Nino-esque tropospheric/stratospheric pathway within the popularly wish-casted timelines commonly exhorted by the masses. A good health warning addendum attached to related long range stratospheric forecasts in this respect (and indeed the nature of any tropospheric fall-out should it actually come close to an SSW ultimately) continues to point to a sensible position advocating potential for changes within the tropospheric/stratospheric interaction relationship cycle being most likely (if at all) heading to the final third of this season and so beyond the period of most recent tranches of hope-casting that are evident, Such an outcome still does not guarantee a NH freeze notwithstanding that With ultimate switch to e/QBO in mind, its also worth pointing out that the solar cycle is most effective in maximum gravitation of poleward blocking as it starts its ascension from the bottom of the cycle (not there yet at this stage in 19/20). 2009/10 was an example of this combination coming together strongly - and where a stronger El Nino pathway combined with deepening pivot phase -ve QBO and the solar cycle beginning to climb from its minimum to strongly heighten and augment tropopause instability in the early winter and then deliver an SSW in the later winter. e/QBO : .2009 10.71 12.33 11.44 9.11 1.56 -5.47 -12.21 -14.45 -13.81 -11.69 -13.83 -15.57 2010 -16.02 -16.98 -19.68 Please exercise rebuttal according to the democratic freewill - I am especially ambivalent according to personal position not influenced in any way by desire or drive/motivation to have to arrive at, or be seen to arrive at, any particular vested outcome and compete with ongoing popularity stake.votes. Simply the same approach as adopted all year round - after all, the atmosphere doesn't take a break between March/April to October/November. She keeps doing her thing without taking lunch break. With that, I send Christmas wishes and bid adieu, till opportunity arrives to enjoy personal interests in the quietness of Spring and Summer seasons
  4. Further to the latest excellent summation from @Isotherm I have posted a recapture with perhaps the bolded part the most ratiocinating to the here and now. The captioned extract was typed at the start of October within the pm thread I inhabit. This is not an exclusive club Ostensibly, the basis of it is to "think-tank" the variables and blend ideas to plough back into the main public arena and hopefully help assist discussion and provide balance. Suffice to say, a lot of the suggestions have played out according to sign-posting. Some, not all, discourse in this thread keeps faith with NWP prediction of teleconnections, but prediction and verification are two different things. So its a prudent endeavour to proffer verification statistics as a means to temper hyperbole and over exuberant expectations based on future extrapolations of numerical products Intra seasonal tropical and extra tropical cycles influence the patterns on the basis that the atmosphere "remembers" its recent history. Its a case of deciphering whether these cyclical momentum transports will lay "faux trails" towards consolidating the majority human weighted bias solution and so douse the flames of exuberant exultation - or whether they do indeed result in the bias solution gaining longer term sustained traction with time With the latter option in mind, and cutting through my verbiage as re-posted, nothing has changed sentiment according to early perceptions. And hence no doubt will be perceived to continue to rain on the parade 1) Slow -ve QBO transition restricts the stratospheric pathway and is acting as a surcease to any potential offered by the atmosphere/ocean circulation feedbacks. The low point of solar cycle in terms of sunspots and geomagnetic activity creates added uncertainty to the speed of transition of the QBO phase this winter and this will have very important consequences as low solar activity augments the state of the polar field both ways according to whether a +ve (stable/colder SPV) or -ve QBO state (unstable/warmer SPV ) prevails. I have "borrowed" this image depiction of solar cycle acidity from another site to depict the current position relative to the longer term history. 2) Despite the ever appreciable Panglossian-esque backdrop within the daily chatter of the room, driven by exuberant loyalty allegiance to distant (and equally mendacious) GEFS stratospheric suites - the observed interposing of +ve momentum tropical >extra tropical phasing has remained and continues to remain, for the foreseeable, unpropitious to greater diminution within the polar field and so ephemeral poleward ridging/cold air advection distribution is the maximum bandwidth allowed by the momentum budgets. 3) It is necessary here to state emphasis on "ridging" and not "blocks" per se. The latter implies a more sustained, ubiquitous holding pattern. Despite chatter to the contrary, reality shows a paucity of slow moving blocking patterns c/o of any major -ve zonal wind reversal and instead simply artefacts of Pacific wind-flow patterns allowing periodic jet extensions permitting short lived downstream split flow as part of a two speed/.two phase alternating tropospheric pattern 4) With that in mind it would seem that the GEFS is in the process of capitulating to ECM caricature of the upstream Pacific pattern. Beyond the 2nd week of December the +EAMT induced ingress on the pattern which has acted as catalyst to bullish overtures and posting overspill, there are increasing signals for the AO and NAO domains to follow the scenario painted in early season thoughts c/o seasonal wavelength evolution of angular momentum trends vs strengthening of the SPV 5) I think that circumspection, rather than arrogation should prevail related to the feedbacks this season from the highly +ve IOD. The precise relationship that the atmosphere adopts to the base state is salient in this respect. If tropical forcing short-falls within the central Pacific than popularly envisaged within echelons of observers, and greater emanative forcing is disgorged from within the Western Indian Ocean (where warmest waters exist) then a greater Nina-esque type feedback (in relative terms to the base state) will restrict poleward planetary wave dispersal as part of +ve momentum budgets as westerly wind burst propagation is kept in check within the tropics. 7) This in turn will inhibit any potential of -ve QBO transistion to the stratospheric pathway adding effectiveness to poleward rossby wave propagation, especially if the present very slow transition persists through the mid winter period. In this scenario, it adds to the existing predilection of this season towards displaced vortex effects c/o wave activity (hence re-organization capacities enhanced than evidenced during a split vortex under more sustained diminution)
  5. Some six weeks forward from this considered opinion, and a suitable moment to reflect and compare expectations with reality. This particular post is restricted to the bandwidth of such considerations and should not be interpreted or attempted to be represented in any other context. 1) An intra-seasonal high frequency tropical cycle completed amplitude orbit of the Pacific and assisted promotion of poleward +ve momentum transport, transferring into an amplified tropospheric profile during November to date - and in tandem with planetary wave perturbing of the tropopause layers. We have been seeing a predilection towards a spasmodically displacing polar vortex profile - both consistent with this type of regime as consistent within the current "mini ENSO cycle" at this time of year, and most especially also wholly consistent with a late autumn Nina-esque tilted atmospheric disconnect vs a very weakly Nino oceanic state. 2) Being intra-seasonally related, it has not in my opinion, reflected the type of underlying step change in ocean>atmosphere relationship, (and ahead of further QBO transition assist to a potentially more sustained amplified profile) required to sustain a -NAO domain. One that has mostly been contained within normal NWP parameter expectations of overstated departures at distance and correcting less -ve and more neutral with time. 3) Pertinent to a recent post of mine, I do think that the updated Global Wind Oscillation orbit (subject to typical two day lag) is clearly reflecting the sensibilities of managing those expectations as depicted within its modest current orbit within the phase spectrum vs the GWO Phase 4 synoptic pattern reflection of an amplified downstream profile in the Atlantic, split flow and downstream cold trough. Note the most recent orbit position - on the cusp of low amplitude Phase 4 and weaker than the most recent extra tropical orbit that attained a higher amplitude orbit 4) This weak signal accords with the late November/start of December advertised pattern with the composite for Phase 4 over the coming days - but it needs to be taken in context of the ephemeral drivers that underpin it and not taken at face value as a sticking pattern. The composite should not be taken precisely at face value in terms of strength of any Aleutian low signal and EPAC trough as depicted in this sampled composite - as clearly no surprise that numerical suites are clearly progged to abort the current scenario relatively quickly afterwards with an upstream NE Pacific ridge and the downstream amplified Atlantic ridge losing latitudinal buoyance as polar jet energy starts to return and replaces split flow in accordance with falling angular momentum 5) This is not to play down the current/upcoming short term regime unduly, but its my view that expectations for the peak lag period related to recent tropical>extra tropical forcing should not be viewed with unduly exaggerated upside potential based on its self limitations and expected duration 6) With those limits and duration in mind, trends in angular momentum and tropical>extra tropical momentum direction of travel continues to support the thinking expressed leading into mid autumn that the ongoing wavelength scenario would ultimately give way to a return to a phase of low momentum attendant with new month and seasonal changes from autumn into winter and allow a more zonal profile to emerge - at least for a period. Low suppressed momentum in early winter, and ahead of any major potential stratospheric warming event later on, is an assist to coupling polar westerly gyre to the tropopause and a flatter more zonal pattern and with sub tropical ridging in both upstream Pacific and Atlantic as part of a downstream +NAO profile 7) As highlighted in point 4) this +NAO transition is clearly advertised in present numerical model suites as coming into the 10 day period, and on is right on cue with provisional suggestions at mid autumn This does not add up to any more general winter seasonal prognostication, simply consolidation of provisional thinking, and ahead of attempting to decipher any much longer seasonal considerations 9) I would finally like to warmly thank Tom @Isotherm for his clarity of explanation on my behalf and which was considered to be a sensible way forward as circumstances dictate
  6. Hello. To be honest, I haven't been sure how to reply to this post and am still just as uncertain as to how I could have qualified my own any further But I will nonetheless provide a duplicate analysis which basically amounts to exactly the same thing. it is always sensible, in my view, not to conflate the near term micro and macro scale pattern with the overriding bigger picture - and especially avoid doing so to (effectively) reduce in value the contribution of any assessment geared towards the bigger picture (and which is not trying to fit any given bias solution into that framework) . So my own contribution, and those of my "colleagues" to whom you also have apparent disagreement and/or pursuing a separate argument to your own - have been trying to take such a wider neutral view, and assess a range of probabilistic solutions that exist within the macro scale longer range. My own post yesterday gave an overview of a suppressed momentum regime and hence my suggestion that increased zonal westerlies are a consequence of that. I think that my reference to laws of conservation of angular momentum in this context is watertight and requires no further explanation here.... It is the precise relationship that the atmosphere adopts to ocean base state at any given time that matters here - and any signal for a sub tropical ridge regime in the Pacific (in the context of the prevailing regime) is redolent of an (ephemeral) Nina atmospheric type response and not a Nino atmospheric artefact. On that basis, increased easterly inertia within the tropical>extra tropical circulation (Nina-esque) will underpin such a ridge and compensating westerly momentum will be observed in flow above this ridging. Indicated cyclone activity in the WPAC, on the other hand, around the period of "interest" circa early December is redolent of an equally (ephemeral) Nino atmospheric structure and is one that was indirectly the subject of my discussion yesterday - and so my argument that any +ve momentum Phase 4 GWO excursion in association with Pacific jet extension and downstream split flow, needs to be seen within the context of a mix of split flow episodes and interrupting zonal westerly suppressed phases as the default longer term pattern. With this in mind, its important to look at any shorter term +ve torque exchanges within a bigger picture suppressed momentum regime and assess their impact/duration on the pattern to that diagnostic accordingly. It surprised me to be honest because it is integral to your own argument that you made no mention of it at all in your attempted deconstruction of my thinking - but in my opinion you should consider exactly why I posted that GWO Phase 4 composite and then why I attempted to explain how and why the synoptic reflection of this (amplified downstream Atlantic/Southern Greenland profile and -NAO) might be relatively ephemeral/short lived and/or watered down in nature. Time will naturally always tell what exactly happens. But also, in my very honest opinion, its more about (attempting) accurate analysis of what is transpiring, and helping others understand what is happening, and less about actual popular outcomes - though of course everyone is interested in outcomes and most all of us like to see the weather gods oblige with our meek suggestions. Its possible to eschew watertight principles that can cater for a disparate conceivable range of outcomes at range in terms of sensible weather - and not necessarily select the bias outcome on each occasion I do think, and gently try to suggest, that observing these respectful measures and approaches reduces some of the hierarchy and one-upmanship on both twitter and forum discussion sites because egos are put aside and it is more to do with the science than packaging the diagnostic towards a favored outcome via condensed tweets, and irrespective of how plausible the package may be and associated knowledge and status So to repeat in summary...and for clarity: Any prognosis to split flow in my opinion needs to be taken in context of the longer term (suppressed momentum) macro scale picture which does not see sustained spilt flow, but also sees transitory periods of greater polar flow - and when sub tropical ridging is more prevalent within the Pacific. The oceanic (very) weak/neutral Nino is seeing an atmospheric relationship adopted to it - which is more towards a Nina regime than a Nino. Probably (ok definitely!) repetition of themes of split and polar flow in that reply, but it seemed it was necessary to have to do so. Apologies to all for duplications/triplications accordingly
  7. Over the course of the last month, globally averaged angular momentum has risen some +3SD c/o the intra seasonal high frequency MJO wave completing a full mini ENSO cycle orbit through the tropics. This eastward moving amplitude progression has injected significant westerly inertia into the atmosphere and these westerlies propagate poleward with time and account for the amplified tropospheric pattern and early season perturbing of the tropopause. However the context of this angular momentum rally, and the westerly momentum it has added to the atmospheric circulation - is that it represents a peak of total global angular momentum only back to parity after a -3SD disconnect at the mid-way point of this season. The eagle eyed with access to the budget plots will notice the current reality showing both frictional and mountain torques are trending -ve following the recent high frequency signal induced AAM spike, and as the tropical wave through the Pacific completes the latest mini ENSO cycle. Easterly winds are therefore being added to the global wind-flow circulation and constraining the Global Wind Oscillation into descending momentum Phase 8 (opposite transitional phase to rising momentum Phase 4) as +ve westerly inertia is scrubbed from the tropics and extra tropics So with momentum now falling back from its peak, there is no significant long term support for amplification mechanism unless further tropical>extra tropical ammunition is available beyond the usual lagged timelines of +ve momentum transport within the extra tropics. Short term deceleration of zonal winds within the lower stratosphere cannot be sustained in the absence of a continued supply of tropical westerlies propagating poleward to balance the wind-flow budgets with compensatory -ve momentum deposits at higher latitude, and according to the laws of conservation of angular momentum With all this in mind, and according to pre-winter wavelengths, any suggested blocking and potential -NAO signal has to be presupposed on a further robust Global Wind Oscillation Phase 4 signal stemming from another substantive increase in angular momentum tendency. Continuing churning within the tropics would suggest in these circumstances that another high frequency orbit recommences centred in the Indian Ocean, would head eastwards and equate to further westerly winds being added across the tropics and reflected by rising +ve frictional torque leading +ve mountain torque tendency. Here below is a suggested late November/early December composite for Phase 4 GWO - but for a holding +ve anomaly due south of Greenland as trailered by that composite, the strong caveat is it assumes lower stratospheric diminution and a sustainably subverted polar field which is far from assured. Otherwise, a quickly reverting return to a more neutral GWO orbit assumes an ephemeral amplification/ tropopause subversion leading to a less amplified profile and with greater polar jet flow. Much as Tom and David @Isothermand @Bring Back 1962-63 have corroborated and attested to. Also consistent with my own purported analysis of pattern progression this month and into December Following amplitude orbits of the high frequency tropical signal, suppression of convection occurs - and this is proscriptive to any especially early return to Pacific forcing and means that any deterministic high frequency modelling entertaining such a scenario carries an irresolute weighting. Consideration should be given to empirical recourse of the periodicity of high frequency waves based on circa 60 days (to maximum of 90 days) for such particularly active cycles. Temperature contrasts between tropical and polar stratosphere, solar and QBO transition considerations may err the fulcrum balance of timing of further active full progression to an early timing parameter end-of the-envelope. This adds implication and ammunition for discussion as to how the winter progresses beyond the New Year , but objectivity *should* allow for a range of possible solutions and not restriction to any bias solution, for those who hold one. By way of conclusion, a few related and other general observations : 1) The Global Synoptic Dynamical Model (GSDM) is a diagnostic instrument that calculates global-wind flow budgets and is broken down into separate momentum budgets that give some idea where exchanges of those wind-flows will exert a turning force on the flow, as manifested by torque mechanisms - and according to whether easterly or westerly additions are being added and removed from the atmospheric circulation. So helping to disseminate and identify decelerations and accelerations and trajectory switches of the jet stream. It also provides an assessment of planetary wave movement between the troposphere and potentially impacting the stratosphere according to strength of any poleward momentum transport. Importantly, though, it is a year round diagnostic that never "sleeps" and is not yet another magic bullet that comes alive in time for snow-making in winter. My own personal use of this diagnostic extends to the whole year and is based on detached impartiality as means to gain maximum educational benefit - with seasonal preferences that equally cover the whole year suspended as much as possible and which, in my humble opinion and experience, conflict directly with such aims 2) Using MJO composites alone cannot accurately depict wind-flow exchanges and risk fallacious and specious use when used for synoptic analogue comparisons because, as discussed above, the tropics are only one part of the momentum budget and consideration of wind-flow propagation and exchange between both the tropics and the extra tropics must be considered - and then how these may, according to season and seasonal wavelengths, influence the relationship between the troposphere and stratosphere. This is why the Global Wind Oscillation is a more reliable tool to use for composite assessment because it is a depiction of both tropical and extra tropical flow - with the tropics being the engine room for direction of momentum travel but not the full determinant, and especially if and when the tropics and extra tropics show disconnect and are acting in lag states to one another. In this sense, the dampening and exciting of torques is lead by frictional torque (the initial inflection point of where changing wind-flows meet and alter the jet stream) and mountain torques take their cue from frictional torque tendency 3) These diagnostics clearly drive the numerical model, the model doesn't drive the diagnostic signal. So using numerical model projections of teleconnections like the AO and NAO etc rely wholly on how accurately NWP interprets the diagnostic. NWP contains bias and is relatively poor at reading tropical >extra tropical momentum budget changes and large wind-flow switches that create the biggest torque mechanisms frequently cause the most intra day chaos within suites. Face value interpretation of such numerical model vacillation induces its own human variant of vicissitude, - driven by emotional and preference bias myopia. Abstemiously, there is no room and hiding place for bias preference when using diagnostic science to eschew pattern analysis
  8. Please excuse my self quoting - but as a quiet observer of proceedings I thought I would provide a reminder of my own previous analysis which anticipated latest trends and which underpins the wider context of Tom @Isothermthoughts. It might be suggested I am exhibiting poster bias by references to him and also others within a discussion group - however such analysis really serves as an example that commonly shared methodology leads to commonly shared perceived outcomes. When such methodology suspends preferences. This principle in truth applies at all times of the year and is not restricted to winter. The Global Synoptic Dynamical Model (GSDM) doesn't really offer bias "wiggle-room" if it is to be used objectively as its purpose demands. No single approach in the science of meteorology, which keeps us all on our toes, is ever bullet proof - especially if it is skewed towards bias outcomes as temptation may sometimes push. However, any methodology that serves to give good insight into global wind-flow inertia patterns as directed by torque mechanisms that create a turning force in the jet stream (changes to atmospheric angular momentum) is always a vital ally to a forecaster and can help to read between the lines of the vicissitudes of numerical models and also clues as to how the troposphere>stratosphere relationship may interact in the medium and longer term. The issue with NWP is that it can risk extrapolations of patterns too far out in time, or not reading when changes may arise due to dichotomous proxies within the tropics and extra tropics vs the polar field. Confirmation bias, however innocently it may be exercised, can contribute to these error risks if apparent consensus in NWP is reflected by the same (apparent) consensus amongst forecasters. Like shoals of fish, numerical models can switch direction in mid flow - and this often happens both leading up to and immediately after propitious wind-flow momentum transport budgets. In terms of the analysis itself, its hard to add too much to Tom's post. The periodicity (recurrence timeline) of the high frequency signal for amplitude cycles within the "mini ENSO cycle" allied to the QBO transition and solar state does support a "reminder" to the atmosphere through the course of the upcoming winter. This has potential implications beyond the New Year - though timing of any this clearly too uncertain to discuss so soon However, for the foreseeable future the seasonal trends for angular momentum, tied into wavelength changes c/o switch of month and season provide a strong argument for low AAM phasing into December, as foreseen and discussed. Also the Northern Annular Mode tends to couple according to these wavelength changes as we get right into winter wavelengths and so a NPAC ridge, polar flow and downstream +NAO signature underpins the seasonal model suggestions for the early stages of winter at least and as Tom suggests, this puts some context into recent/ongoing perturbing of the tropopause and what might be expected in the foreseeable future. Edit: Posted by Mr Webberweather: Quote: An objective, unbiased approach & characteristically stoic demeanor is one of the main qualities that "separates the men from the boys" per say. My reply: A minority of this audience might have something to say about that automatically applied assumed stereotype...
  9. Hi Tom Yes indeed, and coincidently I have recently also considered 2007/8 in parallel even though it wasn't part of our discussion back then! Some key considerations: We are seeing some westerly additions propagating between 30/40N and these suggest some increasing of tendency for mean zonal easterly anomalies at higher latitudes (shaded blue) to assist amplification of ridging and southward displacement of trough disruption What would be expected to follow the tropical pulse having passed through the Pacific phases that supports these westerly additions is a signal for frictional torque tendency to fall back and invoking a -ve mountain torque across the Rockies to start removing those westerlies and in tandem with a subsequent uptick in the polar jet at higher latitude. So support for a GWO response through Phases 4/ 0/8 - the former indicative of the +ve momentum transport c/o of the tropical passage and the latter indicative of a fall in relative angular momentum as the tropical cycle completes, coming from torques and rotation of the planet that favors a mean ridge solution at each opposite end of the GWO phase spectrum This extra tropical signal is consistent with the Pacific ridge re-setting the wavelength downstream with another anomalous downstream ridge in the Atlantic. Much will tie into the next phase of tropical convection in late November and December. The Atlantic blocking and -NAO scenarios being discussed and suggested as stemming from the twitter-sphere assume another round of amplified tropical forcing to boost repeated poleward fluxing But its worth noting that the seasonal cycle in angular momentum will likely (at this stage) increase in a low momentum base state during December c/o return of the GWO to Phases 1 and 2. Also its sensible/cautionary to not underestimate the strength of the seasonal vortex based on its initial uptick prior to the upcoming interruption to zonal speeds. This evolution of falling momentum allows the space for vortex re-intensification as the hemispheric wind-flow budgets reverses the tendency seen during November for westerly additions at 30/40N to that of easterlies. Compensated westerly inertia at higher latitudes simultaneously removes the propensity for amplification of ridging to higher latitudes as alluded to above . Such a hostile extra tropical circulation would negate poleward fluxing and mean that the repeated synoptic of November, and as dictated by seasonal wavelength changes as winter begins, would be less amplified than that of November. Time as always will tell. But this post is an endorsement of the momentum budget element which is one of the key components that Tom discusses in his detailed and highly objective seasonal forecast
  10. Its my own view that there is no single key area of consideration alone, when it comes to a diagnostic approach that assists seasonal analysis - and moving back and between, or switching from one to another doesn't achieve the necessary equilibrium that leads to a satisfactory assessment of all probabilistic outcomes I can wholly understand why followers of the winter season patterns will choose to attribute priority significance to a single key factor if there is a belief that such a factor increases the likelihood of a single bias outcome. However, the most coherent conclusion so far in my opinion is that ever increasing amplification of hemispheric patterns, which few now doubt has a good deal of attribution to unstable sea ice distribution patterns and feedbacks, has served to increase uncertainty of all possible outcomes rather than increase probability of any single outcome. This includes a cold air advection single bias outcome in winter that seems to have a parallel bias assumption, that thermal gradients will inevitably be sluggish because of this instability feedback and so increase the chances of slow moving and meandering blocking patterns - at higher latitudes. Its always possible to pattern-match and produce desirable results when extracting variables that are conducive towards leading to a given outcome most particularly when that outcome is steered towards, or meets any given desired end product. This applies at any season and not just winter. My opinion though is that in context of popular winter discussion on pages like these, there is no pure analogue existing these days which provides the desired clear cut tropospheric>stratospheric pathway solution with all the implications that go with it in terms of bias solution end product of potential reversal of polarity at higher latitudes, and a disrupted tropospheric pattern overwhelmed by frigid air at mid latitudes. Uncertainty remains about frequency and duration of the SSW mechanism, and this uncertainty also applies to any potential tropospheric fall-out. A cold air solution in any one place isn't a given, as much as a cold solution anywhere at all is not a given - especially as in winter there is simply less aggregate cold air to go around in general to begin with Such uncertainty is sustained through the overwhelming destabilization within the polar regions due to unchecked and vehemently pernicious warming processes. However this does not quid quo pro endorse rubber stamping of indefatigable empirical resolution of a contingent -AO/-NAO pathway relationship if an element of confirmation bias underpins it - and there is a danger that whilst it is of course highly welcome and vital that so much understanding and awareness has been advanced in this area of meteorological science, such awareness doesn't mean it is more likely to make cold spells within mid latitudes in winter occur, just because of that extra understanding. Each and every season (not just winter) has to be taken on its own merits, more especially because of the intense superimposed forcing on weather patterns/climate Equal to such consideration of the higher latitudes, one also needs to look at the tropics, and the additional anomalous warming of oceans across the tropics, which are increasingly frequently supporting stronger sub tropical ridging patterns at mid latitudes due to altered momentum transport processes created through skewed ENSO ocean/atmospheric SST distributions and resultant a-typical feedbacks. A superimposed elevated tropopause is more commonly propagated from tropics to mid latitudes due to increasingly active phases of the ferrel cell c/o warming processes - especially when tropical >polar stratospheric processes (QBO phasing) becomes aligned to further augment this. Diagnostic approach is as crucial to these vis tropical (over)heating as is the true arctic dilemma and consequent alarm over it. Tropical feedbacks are manifesting an increasing frequency and propensity for intense sub tropical ridging to propagate to mid latitudes. These are serving to bolster intense +NAO patterns, as much as any active polar destabilization, under any given conducive tropospheric>.stratospheric pathway that exists with a similarly conducive momentum transport structure, may be argued to serve to compliment a consequent -ve Northern Annular Mode. This means that one is also wise to equally apply diagnostic examination and scrutiny towards the role that slow moving, meandering, amplified mid latitude blocking patterns (so limiting cold air advection in winter and which have clearly also been seen to increase intensity and frequency of mid latitude heatwaves in summer) are playing in weather pattern distribution (and subsequent sensible weather on the ground. Based on the laws of conservation of angular momentum, such activated sub tropical>mid latitude patterns involve corresponding compensated polar jet strength at higher latitudes which is detrimental to, and to the eradication of, cold air advection processes. It is also not a given, under the wider remit of diagnostic variables present at any time, that sub tropical ridging inevitably always evolves poleward beyond mid latitudes (as it can under certain empirical rules progress towards higher latitudes, given total variables that augur such an outcome). This is where considerations to the individual components of the GSDM budget are key. These pertain to the relationship that the atmospheric circulation adopts to the ocean base state - and not ENSO per se. In a lot of communications within twitter and internet weather threads on various sites, there is an incorrect blanket link to ENSO itself without consideration of the increasing frequency with which an a-typical atmospheric relationship exists towards the macro scale base state, and which can mean the difference between poleward and equatorward flux of planetary wave activity - which in turn dictates whether ferrel or polar cell has the ascendancy. One has to also examine the atmospheric budget and break down that budget to see where the dominant aggregate wind-flows exist at any given time. Dominant inertia flow could exist within either global hemisphere - and within that given hemisphere, they could also exist at various latitudes that have a bearing on where jet deceleration or acceleration occurs. In turn determining where spatial inertia distribution permits developing blocking structures, set against compensating zonal velocities elsewhere according to the amplifying/de-amplifying proxy of change of (+ve or -ve) wind-flow torque mechanism that dictates the turning force within the atmosphere circulation and controls angular momentum tendency. If tropospheric momentum transport is a-typically skewed by sustained and unchecked artificial superimposed forcing, then one cannot make analogous linear assumptions about poleward transport of wave eddies through torque mechanisms that will perturb tropospheric layers. Large lessons were learnt last winter in this respect, when such assumptions were made that a tropospheric>stratospheric pathway existed, and permitted through the macro scale atmosphere>ocean signal vs arctic instability to create the conditions to trigger a cold-air advection brand of stratospheric disturbance. Stratospheric disturbance indeed occurred but its arctic>mid latitude distribution of expunged polar airmass was very much restricted vs expectation - and despite its very local intensity on the micro NH scale, it was out-stretched by the predominance of sub tropically derived warm anomalies. This is also an unbalanced relationship existing intra seasonally and not applicable alone to winter. In this respect and again in reference to this year, despite prolonged fall-out from a highly dynamic final warming of the stratosphere, and which continued to have quasi-permanent lag influence on a good part of the summer season - this did not result in a uniformly supressed jet stream sustained at mid latitude. A predominance of intense sub tropical ridges were often present alongside any propensity for enhanced summer easterlies at higher latitudes - the latter more especially in early summer however. Intense heatwaves were still very much a feature despite any spasmodic blocking at higher latitudes and the first of these appeared remarkably fast even when the higher latitude Atlantic blocking c/o of the final warming was starting to pass its peak. So a seamless intra seasonal approach, and appreciation of the role that changing wavelengths play alongside the timelines of intra seasonal phenomena, is required to be adopted to objective diagnostic approach, and not a truncated one dimensional approach that pertains to one season alone and omits consideration of what has preceded it. In conclusion of all the above, I welcome the paper dissemination posted on this page, which illustrates the open mindedness that David @Bring Back 1962-63 rightly alludes to above. This invites examination of all possibilities to advance the science without attempting to fit the science to any given bias outcome - at any time of year and not just in winter.. With respect to the here and now and moving forward : Its not a surprise to be seeing the amplified Atlantic ridge programmed over coming days underpinned by some -NAO troughing. This, in accordance and in tandem with advancing autumnal wavelengths, advertised through torque momentum now falling from its 'peak' and +ve momentum westerlies getting scrubbed once more from the atmospheric circulation. The recent momentum rally has cut the -ve GLAAM deficit to -1SD prior to probably renewed descent. The failure of the GWO to engage the transitional phase space 4, outside of the La Nina attractor phases, also of note in terms of the tropical/extra tropical cycle. Much of the tropics, and the Pacific now controlled in the days ahead by increased easterly inertia. Based on assessments for the season made in the first part of September, the pattern vs the atmospheric feedbacks are progressing close enough to what has been anticipated. It gets more difficult to decipher as winter seasonal forces start to align, and in some cases clash with one another, but for my own part there is no reason, yet anyway, to alter expectations looking ahead. Caution therefore remains for my own part about any early cold air advection scenarios c/o amplified Nina-esque ridges and what this might mean looking too far ahead. Wholly typical for the last third of autumn under low angular momentum regime wavelengths, and still relatively early for the tropospheric vortex in terms of timing for starting its traditional annual attempts to couple with the strengthening upper stratospheric vortex and organize within the polar field Objectively and to mitigate as bias adjustment (as is prudent and sensible at this of year) - then based on the discussed atmospheric budgets, replying on walker cell/ WPAC typhoon activity as a means to garner planetary wave disruptive elements is not likely to be enough to prevent vortex intensification impacts extending into the tropospheric winter - and it would require a sufficient push from within the mini ENSO high frequency tropical signal and also a signal that the QBO transition is becoming more progressive. There is no clear indication yet of the latter either, at this time. In my opinion.
  11. The key thing about the 62/63 unusual anomaly case (and not too different from late 2010 in this respect) was that +ve momentum transport processes preceded cold air advection/blocking and the GWO orbits in the Nino attractor phases in late autumn/start of winter 62 confirm that those +ve torque processes lead to the early season tropopause instability with poleward disruption within the tropopause taking place. Post SSW is indeed when a low AAM pattern (sluggish momentum) can serve to hold a higher latitude blocking pattern in place if the polar field is conducive to this. Quite the opposite though to a -ve AAM pattern pre-SSW where the increased westerlies at higher latitude run flat and fast and increase the polar gyre. Which was the gist of my earlier post. The GWO in autumn 2010 similarly responded to +ve momentum processes and a departure in terms of atmospheric /ocean de-coupling, temporarily, from an impending strong La Nina regime. So its very true that -ve momentum processes following poleward surges in momentum can 'lock in' slow moving blocking patterns. as happened in 62/63. The usual dominant polar branch of the jet that occurs with low angular momentum regimes - gets instead diverted/split by stratospheric>tropospheric downwelling which creates a shut down far greater than the residual polar jet momentum created by -ve AAM forcing within the tropics. Also, seasonal wavelength changes into late winter further prolong such pattern locks - much as also happened in late winter and Spring 2018 when the La Nina standing wave had been temporarily reversed by the +ve momentum transport processes in late January that led up to the SSW. But a subsequent return to low AAM and the GWO returning to the Nina attractor phases locked in the blocking, and according to those end of winter and start of Spring wavelengths Tropical/extra tropical forcing through +ve momentum processes create a poleward fluxing pathway to break the stability of a cold stable vortex - any resultant higher latitude pattern suddenly blocks any return to -ve momentum like a huge boulder in a stream, and returning polar jet energy is instead forced around the pole with the result that warm advection suddenly floods into channels that previously were cold zonal vorticity energy parcels. Of course, so many decades later, its necessary to factor in background warming trends and so many altered states between both the tropics and the pole before assuming any composites/analogues - especially where any fsvored outcome is involved. But diagnostics such as stratospheric/tropospheric interplay and GSDM momentum budgets vs computer model interpretation of these variables lack any such human attachment to weather type preference anyway - and Mother Nature does as she will despite how we interfere. alas, too much
  12. Yes indeed For what it is worth, the tropics and extra tropic are as far away from any co-operative Modoki El Nino atmospheric>ocean coupling as they could be at this time. The Global Wind Oscillation, a plot depiction of aggregate wind-flow inertia within the atmospheric circulation is rooted deeply at high amplitude within the La Nina attractor orbit phases 1,2 and 3 - and representative of total relative angular momentum at -ve 3SD as sum of aggregate wind-flow momentum budgets at this time. Notice the persistence of anomalous easterly momentum around 30N as identified by the blue shading on the plot supplied - and mirrored equally in the SH. Notice also that this regime corresponds with the Western Hemisphere and I/O high frequency tropical blueprint in evidence of the previous weeks. This extent of -ve momentum represents a firmly retrogressive synoptic pattern - but with the laws of conservation of angular momentum meaning that the easterly momentum being added from the tropics - is being compensated by increased westerly momentum at mid and higher latitudes. With stalled QBO transition, and of which uncertainty exists at this time (imo) in terms of speed of continued transition towards -ve phasing at a level compatible with BDC assist to potential stratospheric destabilization - this added momentum leans with time over the upcoming weeks towards coupling of developing seasonal stratospheric polar vortex with the troposphere heading into the first part of winter at least, without any significantly abrupt change to the global wind-flow budget and a very strong rally in AAM to ladder the GWO away from the Nina attractor phases via robust increase in tropical and extra tropical frictional and mountain torques. Factors such as solar minimum, low Barents sea ice etc discussed eloquently and with excellent insight across most twitter and international forum zones only become influentially meaningful in any forward plotting of events as I see it - if higher latitude westerly gyre is interrupted enough for these to start to create cold air advection feedbacks that most analysts are making their starting forecast assumptions hoping they will be. We all know that fitting drivers to bias outcomes, however well intentioned and thought out, still nevertheless creates margins for error when probabilistic analysis can (and often enough does) point to other possible long term solutions that are less palatable than the bias outcome and may exist in tandem with, or stand=alone isolating the bias outcome. I do not make forecasts within any season, and will not be attempting to make one this season either - but I do believe that something is going to have substantially give over the coming weeks for some of the analogue assumptions expressed on this very acquitted and informative thread and elsewhere to become reality. This may or may not be the case, but from my own point of view, whilst I subscribe to caution with seasonal modelling, there are times at least when these models reflect at the very least some compelling starting conditions that are being extrapolated forward and require a large catalyst to alter their expected destination. It will be interesting, either way, to see if these change in coming weeks and( trying to take a neutral position) I am open minded to this. However- at this time the seasonal modelling has some credence and can't be dismissed because it doesn't reflect sensible weather of choice, in my own opinion of course Just to add, as I should - the GSDM plots are restricted access only @OceanSnow I will send a pm in reply when I have time
  13. In the nicest way, things haven't turned out yet for this storm It is still subject to modelling that is set in the future, and subject to extremely sensitive and fine margins in terms of infrastructure risk vs probabilities of landfall (where and when) Anyone living in the SE US will remain on the highest alert right up to nowcasting situations with a highly dangerous and volatile storm such as this. Based on the life threatening risks of such a storm it will never be deemed a non event....until it is as certain as possible to know where impacts are most likely to be focussed. Indeed it only becomes a 'non event' when the storm has passed and it is known that impacts have been next to minimal. The NW Bahamas will certainly not be viewing this as a non event. This looks extremely worrying for them especially if Dorian stalls anything like suggested. The overnight EPS 'cone' has shifted to a solution that (as of this time) reduces the risk of Florida landfall..... . ….but as one who likes to pay attention to suggested diagnostic evaluations first and foremost, numerical models are always snapshots in time and are evolutionary in prediction and not face value absolutes. Its far too soon to suggest that the models will not shift back to a Florida solution, however much the trend may appear to moving way from it at this present time. Until, or if, the risk becomes zero in any given place, then the very high impact risk remains the crucial assessment vehicle. The suggested stall could prove quite a pivotal sequence in terms of the fate of the Florida east coast, (as much as it could prove a most unfortunate fate for the NW Bahamas - one can only hope for them) However, clearly most especially for those whose homes and livelihoods are most at risk from Dorian (including Floridians) its eminently sensible and wise that ears avert attention to overly premature declarations based on suggestions of intra day modelling suites who will continue to struggle with initiation data within a storm that, quite typically, will always be one step ahead of the number crunchers Notwithstanding any of that, eyes and ears should be spot welded towards forecasters. of whom there are many. who assess risk probability based on diagnostic evolution of modelling unfolding with time and not based on single snapshots of time Edit: The updated Euro model evolution rather illustrates the points made
  14. I think that some separation between GSDM data and proxy supporting data is useful to read between the lines a little to help distinguish between natural ebb and flow of momentum budgets and associated torque mechanisms as they can play quite different roles in determining short and long term variations as contextualized within the broad-scale ENSO cycle. Short term loss and gain momentum transports certainly impact sensible weather over relatively short term periods in terms of whether they decelerate wind-flow patterns and create associated -ve torque mechanisms or accelerate wind-flow patterns and create +ve torque jet extensions. But attempting to extrapolate these forward in respect of trying to correlate wind-flow to surface patterns is soon fraught with error as the atmospheric circulation is always in constant flux and one momentum budget 'transaction' alone doesn't inextricably alter the macro scale ocean>atmospheric relationship and associated sensible surface weather on any permanent basis. Such exchanges requiring monitoring of persisting trends over weeks at a time, not through one specific wind-flow event which has it its own limited wavelength or lifespan With that in mind, the -ve NAMT of the other week did/has created by its nature of deceleration of wind-flow, a regressive pull on both relative tendency and total angular momentum as part of a legacy of persisting trade winds across the Pacific during the first two thirds of June. But this is where its necessary to differentiate between the cyclical MJO 'mini cycle' and the low frequency walker cell signature with also the passage of convectively coupled kelvin waves which create separate upwelling and downwelling sequences which alter the composition of the SST ENSO zones over longer timeframes and also interfere with the budget wind-flow exchanges according to whether they act constructively or destructively on the base state. If we take a look at the low frequency signal, the CFS continues to advertise the persistence of convergence close to the dateline through July. Longer term ENSO forecasts should be precepted against shorter term proxies, as the former tends to be reactive to the latter, rather than necessarily proactive in themselves These dovetail with the z850 zonal winds on the Hovmollers plot, in the shorter term, that clearly depict this low frequency convergence Adding this together with the recent/ongoing passage of the convectively coupled envelope of the MJO, ( and associated tropical activity c/o Barbara as an artefact of that in the EPAC), one gets an understanding of why the trade winds have been dampened. This doesn't, however, account for the lagged effects of any wind-flow deceleration within the extra tropics that has scrubbed out westerly momentum within the extra tropics and is still working through its timescale feedback. When we consider the momentum budget, the tropics and extra tropics can exhibit periods of relative disconnect where contravailing wind-flows are present in each. Hence why care is required when extrapolating how the total budget may behave over a future period. So whilst the MJO is an engine room catalyst for accelerative and decelerative wind-flow propagation, it is not the only driving mechanism of z850 wind-flow in the Pacific - and fluctuations of wind-flow and propagation of momentum between the tropics and extra tropics that influences the orbit evolution of the Global Wind Oscillation should be assessed from broken down proxy analysis. In this respect any decline into the less +ve echelons of the neutral GWO octant phases does not automatically imply long term quasi permanent decline As alluded to above, torque events have a wavelength (lifespan) and as also impugned previously, they cannot, on their own, determine longer range atmospheric circulatory and reflected surface patterns in isolation, and it cannot be presumed that they are definitively part of a longer term trend in angular momentum tendency associated with macro scale ENSO shift. It is highly concurrent with any minor or major ENSO event, for interim waxing and waning phases to occur. Personally on that basis, but also as one who does not make definitive forecasts anyway, I would be highly cautious of extrapolating ahead through the rest of summer, let alone the coming two seasons. But for what little it is worth, I am not sure that a Nina//wQBO low solar combination,(if it hypothetically evolved) is necessarily a good thing for those already resting their hopes on NH winter in terms of upper polar vortex development - but this is clearly highly speculative at this range anyway, and open to considerable margin of outcome with uncertainties apparent within weeks, let alone months. Plus based on the downwelling sequences of the +ve QBO wave vs the waning late season dynamic warming into the troposphere, the coming few months looks to have an increasingly less blocked structure at higher latitudes. For now, a waning oceanic phase to warm/neutral is palpably apparent - but notwithstanding that, until, or if, the convergence zone Nino-esque walker cell breaks down (and there is not evidence of that within a forthcoming period that some are making assumptions to formulate forecasts built upon a more La Nina-ish feedback) what matters here is the relationship that the atmosphere adopts to the ocean base state, and not the base state per se. Taking into account the periodicity of the MJO cycle which is up to between 60 to 90 days for active amplitude cycles, and with the last active amplitude Phase through the Pacific in May, then assuming the Nino walker cell prevails, a further active phase, based on background proxy parameters becomes increasingly possible in the latter half of the summer. That, and a downwelling CCKW phase due (as opposed to the early summer 'destructive' upwelling phase) wrt ENSO zones, will be something that seasonal forecasting will not be 'seeing' very clearly at the moment. The rest of the year remains finely balanced, but whilst El Nino has clearly struggled to sustain its late winter 'peak' strength and has weakened further, other years like 1997 and 2009 for example have shown that twin standing wave straddling seasons (African and Pacific) which exert -ve destructive and +ve constructive action respectively on any +ENSO state, can achieve further waxing regimes after apparent mid year decline - and with renewed atmospheric/ocean co-operation coming into the final third of the year. Its far too soon to discount such an event at this time Edit: As a backing supplementary, this animation c/o Ben Noll illustrates how the Nino walker circulation created a sink in the Atlantic Ocean due to downstream wind shear during June The GFS is predicting an uptick of easterlies c/o the African standing wave across the Equatorial Atlantic, destructively interfering with the Pacific wave and ending the downstream wind shear across the EQA. In contrast to the Euro model.- as suggested above More reasons not to place too many bets too soon Tams
  15. Hi James - yes, I think that use of proxy data provides a bit of extra reading between the lines when apparent contravailing macro scale factors are present. In this respect good reason not to too directly correlate GSDM diagnostics to NWP synoptic patterns and instead focus closely on the "grey areas" There is a continued rossby wave train c/o the remaining weak Nino standing wave in the Pacific and it can be seen how the forward speed of the current eastward moving kelvin wave can be determined by the filtering of the velocity potential wave bands The SOI evidences the persisting wave trains c/o consistently recording -ve values and this has been determining frictional torque at 30N close to parity based on the momentum budget of the backdrop of globally averaged angular momentum remaining a little above average as is consistent with weakly +veENSO Capacity of any +ve torque response is proportional to the existing +ve wind-flow inertia that already exists in the greater atmospheric circulation. This means that the higher the macro scale inertia present is, the higher the extra additional supply of the same wind-flow is required to be added to create a greater still tropical>extra tropical momentum transport response. On that basis, it is loss of westerly momentum due to tick backs in angular momentum c/o trade wind bursts which would register greater downward fluctuation in frictional torque tendency. But unless the whole tropical>extra tropical circulation decouples as part of a longer term shift, too much shouldn't be read into such short term torque differentials attached to the "mini ENSO"/ aka MJO cycle. (Also see Hovmollers plot further below identifying continued weak westerly wind anomalies). Additionally, CCKW activity passing through the EPAC is responsible for helping dampening the trade wind burst east of the dateline, breaking down wind shear, and allowing the spawning of the first tropical activity of 2019 in the Eastern Equatorial Pacific. As per Mr Klotzbach : If one takes into consideration the persistence of the "destructive" suppressive phase on the Nino standing wave from late May and during the first two thirds of June, up to the recent resumption of Pacific +ve forcing from west of the dateline and eastwards - than one can conclude that both total and relative trend angular momentum have held up well. A clear sign that the atmosphere still remains receptive to wanting to retain some semblance of "westerlyness" to wind-flows rather than let that period of relative destructive -ve forcing totally re-configure the standing wave to the WH and I/O. A twin forcing regime has rather developed, which dictates active and suppressive tropical activity based on whether the Pacific or newly developed WH wave is engaged as part of the intraseasonal MJO cycle.. Other years like 1997, 2006, and 2009 saw a similar twin standing wave regime I think that ENSO forecasts and some tropical/oceanic commentators have exhibited a surfeit of Nina bias in this respect since late Spring. Its understandable though of course that a few eyes perhaps look well ahead to the Hurricane season and are keen to assess SST's in the tropical Atlantic and what presence (or otherwise) of wind shear might be evident depending on whether some degree of Nino forcing persists, In the more advancing mid summer centric focus, the evolved and evolving diagnostic proxies I think help assess the risk probability of amplification c/o -ve forcing in the Pacific as "restricted" and to take any amplified Pacific and Atlantic indicators from NWP as not sustainable on that basis. This would require a clear signal of shift in ocean>atmosphere regime and the Global Wind Oscillation, a key tropical and extra tropical indicator of global wind-flow, losing traction towards the lower octants of transitional/neutral phases 8,0,4 - with evidence of greater Phase 8 transitions which would suggest ever higher losses of momentum within the atmosphere as greater and greater amounts of westerly inertia is scrubbed out at the expense of growing -ve frictional torque at 30N in the tropics leading -ve mountain torque tendency at 50N in the extra tropics. However, the persisting pattern is one of the GWO maintaining a very tight knit orbit within the more +ve sections of the "transitional" wind-flow phases - and this is indicative of insufficient -ve wind-flow existing within the momentum budget to create any sustainable Nina-esque regime. There is no evidence, beyond natural fluctuation ebb and flow of wind-flow and torque mechanisms within a weak momentum budget, this is going to change much any time soon. With all this in mind, its sensible in my view to assess NWP cautiously against proxies and look at how they are reflected within the GSDM momentum flux and torque budget than attempt direct diagnostic > synoptic pattern matching. As interesting as that may be of course On that basis, extended ensemble and weekly outlook products require a regular updating watching brief based on diagnostic budgets first - rather than attempting working assumptions of how the diagnostics seem set to evolve according to whatever the numerical models might suggest.. Numerical models have biases, are characteristically prone to error reading the tropics at a given greater than 5/6 days ahead - and so therefore cannot always read wind-flow changes and fluctuations ahead which means they can be prone to change direction like shoals of fish in mid stream. As we all know, signals leads models. Models do not lead signals With that said *she reflects a little further *, I think that James assessment of the most recent EC weekly suite correctly identifies the Atlantic anomaly as part of a typical weak Nino pattern. I am also somewhat cautious in respect of the future modelling of the polar field and think that Tom's seasonal expectation of "spasmodic blocking" remains consistent with the medium and longer term - and with continued expectation of this to have a retreating tidal trend as the summer continues to mature. Tams Edit update : I think its worth me adding something wrt the GWO/AAM budget and the limited boundaries of ebb and flow I referred to. In the immediate term its true to say we are seeing something of a temporary divergence of this. The recent quite robust EWB in the EPAC has created an inverted wind-flow as momentum suddenly drops and a significant -ve NAMT has occurred this week. The two day lagged mountain torque budgets identify this clearly The extra tropical Global Wind Oscillation has responded with a jump out to -ve tendency transitional Phase 8 in response to the upstream wind-flow momentum drop This upstream vacuum creating extra amplification of the downstream omega block stretching from the Atlantic into Europe - with the Atlantic section of the block assuming dominance as a result of the temporary retrograde pull of the pattern. This has allowed the unusual situation of cool air advection being pulled around the strong upper ridge with a long fetch across relatively low northern Atlantic/Icelandic SST'S to the UK sharply undercutting an intense plume of hot upper air which by contrast is creating record breaking heat at the lower boundary layers across many parts of mainland Europe this midweek. EC map Atlantic/European view as of yesterday. A classic example of one occasion where macro scale wind-flow changes, which can be identified within GSDM diagnostic AAM/torque budgets, can be accurately pinpointed onto associated synoptic responses and produce micro scale contrasts owing to geographical location relative to the positioning of placement pattern features Based on the erasing of this -ve momentum wind-flow phase as the trade winds are ended across the EPAC c/o CCKW passage - the result looks to be a fast return GWO orbit back to the default prevailing wind-flow pattern. Hence NWP advertising the intense Atlantic amplification to cease the end of this week as momentum upstream recovers - and the ridge to edge back east and retreat through mainland Europe. At the same time the low level maritime cool air flow over the UK is cut off and due to be replaced by the residual hotter continental air for tomorrow and the first part of the weekend Further update based on above suggestion as quoted yesterday: Based on the erasing of this -ve momentum wind-flow phase as the trade winds are ended across the EPAC c/o CCKW passage - the result looks to be a fast return GWO orbit back to the default prevailing wind-flow pattern Evidence for this suggestion now apparent in latest European model trade wind forecasts with CCKW enabling WWB's across the central and eastern Pacific to replace the recent -ve forcing trade wind burst So this supports re-stabilization of the weakly +ve GWO orbit phasing as hypothesized previously
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