Tamara

EPS & GEFS extended ensemble members now starting to pick up on split flow in both the Atlantic & across Europe into early August. Chaotic & erratic still, but at last starting to at least reconcile the long suggested diagnostic with some kind of numerical model interpretation of it. This change in downstream flow increasingly likely to assist cut off lows to the west and south west of Europe at the same time as a downstream ridge ultimately replaces the N European trough. Additionally, the sinking motion across N Africa that has led to the intense 600 dam furnace anticyclone subsides as downstream jet flow reconfigures, leading to the static heat across S Europe becoming more mobile as moist Atlantic air bumps up against the stagnant heat. This implies, eventually, forward momentum developing on a thermal boundary to create a potential thundery low mechanism and advect the heat pool further north and east as cooler air tries to come in behind across SW Europe. So that is a latest updated suggestion for the further outlook. Still some way off in meteorological terms? Yes it is. Considerably delayed from initial expectations? Most certainly & emphatically yes. Guesswork, tea leaves etc etc and other similar nonsense from parochial observers? Mostly emphatically & certainly not..... Alas that type of baiting is what creates a brain drain and drives people away from places like these.

My last reiteration on this as I accept that no amount of rationale is going to be worthwhile when disillusion with the weather in the UK overrides any reasoning behind it. There is no "theory". And there is certainly no "fad". That is, frankly, unwarranted trivialisation. These atmospheric drivers in the tropics and extra tropics are steeped in empirical science of the atmosphere & the physics of the turning force of the jet stream through angular momentum processes. All put together into a diagnostic framework. There is nothing wrong with the science,. What can go wrong is natural human error in decoding the complexities from time to time - but that doesn't make the teleconnection tools related to the science themselves wrong or of little use. As much as it doesn't make the 500mb charts wrong at any given time, irrespective of the fact that they may change in their outlook subsequently according to the diagnostic that drives then and there can equally be human error with these. The point is that they attempt to model the diagnostic processes that are in never ending flux - and such flux constantly evolves the outlook. The 500mb charts are the best overview of numerical overview interpretation. There is no disputing that. However, as stated, these evolve & change as much as NWP evolves & changes its outlook according to its interpretation of the diagnostics that drive them. The reasoning for the changes this July have been stated umpteen times. it is not the teleconnections that are to blame for departure from expectations (in the UK). And neither is the present situation to do with any butterfly or random effects. It is a natural cyclical ebb in the state of the atmosphere that has produced a pronounced disconnect much greater than was anticipated. Nothing more, nothing less. Finally, and with that in mind, ownership has to be taken for the fact that the focus of the downturn happens to be in the vicinity of the focus of a UK weather forum. Better to accept the reality of that disappointment, and own the disappointment - than blame the science, or the tools used based on the science. Whatever the weather, hope as many of you can enjoy the remainder of the summer. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4889208

My last reiteration on this as I accept that no amount of rationale is going to be worthwhile when disillusion with the weather in the UK overrides any reasoning behind it. There is no "theory". And there is certainly no "fad". That is, frankly, unwarranted trivialisation. These atmospheric drivers in the tropics and extra tropics are steeped in empirical science of the atmosphere & the physics of the turning force of the jet stream through angular momentum processes. All put together into a diagnostic framework. There is nothing wrong with the science,. What can go wrong is natural human error in decoding the complexities from time to time - but that doesn't make the teleconnection tools related to the science themselves wrong or of little use. As much as it doesn't make the 500mb charts wrong at any given time, irrespective of the fact that they may change in their outlook subsequently according to the diagnostic that drives then and there can equally be human error with these. The point is that they attempt to model the diagnostic processes that are in never ending flux - and such flux constantly evolves the outlook. The 500mb charts are the best overview of numerical overview interpretation. There is no disputing that. However, as stated, these evolve & change as much as NWP evolves & changes its outlook according to its interpretation of the diagnostics that drive them. The reasoning for the changes this July have been stated umpteen times. it is not the teleconnections that are to blame for departure from expectations (in the UK). And neither is the present situation to do with any butterfly or random effects. It is a natural cyclical ebb in the state of the atmosphere that has produced a pronounced disconnect much greater than was anticipated. Nothing more, nothing less. Finally, and with that in mind, ownership has to be taken for the fact that the focus of the downturn happens to be in the vicinity of the focus of a UK weather forum. Better to accept the reality of that disappointment, and own the disappointment - than blame the science, or the tools used based on the science. Whatever the weather, hope as many of you can enjoy the remainder of the summer.

Bom dia! A frente prevista para as próximas horas já está a... FB.WATCH Bom dia! A frente prevista para as próximas horas já está a penetrar o noroeste peninsular, trará algo de água ao litoral norte e centro durante as... Boa tarde e todos (my Portuguese!) A departure from recent broad scale NWP vs diagnostic discussions The above link discusses the trailing front straggling all the way down to the NW Iberian continent from the unseasonal deep Atlantic low plaguing the UK today and this weekend. This front is bringing some mostly light but welcome rainfall to the NW coastal fringes of Spain & Portugal and even a light shower possible into central parts of Portugal (inc IMBY tonight and at first tomorrow) Portugal has been on the periphery of the ongoing southern European heatwave and largely escaped the worst of it -with only parts of the Alentejo and Algarve in the SE of the country seeing values close to 42C early in the week. Mostly low to mid/upper 30s has been the daily maximums and with Atlantic breeze influences helping to temper the heat. This is hot enough of course but nothing unusual obviously & considered within the boundary of relative normality by the Portuguese. Nights have been comfortable enough also - mainly the high teens rather than the upper twenties and low thirties across the border in inland Spain! The weekend provides a break from the most intense heat across the Spanish border, as these Atlantic influences penetrate a little further into the interior, before the pattern re-sets again next week to be similar to this week. So the looped jet stream keeping N Europe, esp UK and Scandinavia, cooler and more unsettled than average has on the other hand helped to restrict westward advancement of the (dangerous) heat dome from also covering the Atlantic side of the Iberian continent on this occasion. Swings & roundabouts with these things.

Modelling forecasts from ECM, as a quality example, in respect of AAM will give some insight into the numerical models synoptic outlook. More reliable in respect of initiation data etc than the CFS vs 2 AAM forecast on that mapwall site. However, if the numerical models (including ECM) are blindsided by the strength of an existing diagnostic signal this can, and sometimes does, create errors in extrapolating the length of that signal forward. This is the essence of the posts being made of late in terms of trying to urge caution in too much fixation with extended NWP. With all that in mind, its worth looking again at the actual consolidated GSDM data to try to get some clues as to the longevity of the AAM lull and how it is possible that some blindsiding may increasingly likely to be in operation. As posted a few times, large amounts of surplus westerly winds ( Nino-esque inertia) have been scrubbed from the extra tropical circulation. These surplus +AAM windflow anomalies ensured the downstream ridging of the first part of the summer. Sub seasonal effects such as the Indian monsoon are now scrambling the low frequency Nino ENSO signal & feedbacks are emanating from a more Nina-esque background in the absence of high frequency forcing in the Pacific which drove the early part of the summer. The periodicity of the -ve MT is predicated on largescale retrograde effects in both tropical and extra tropical mountain torques. Total aggregate MT in both tropics & extra tropics has fallen this week to -ve 3 standard deviations (from parity). The -ve inertia is identified by the circled anomaly on the plot and the reflected arrowed aggregate STD drop. (There is also -ve inertia corresponded in the SH c/o South America Andes -ve MT processes) Based on the increasingly El Nino-esque base state, a very large disconnect is in process and consequently a very unstable GSDM profile - with the Global Wind Oscillation advertising this disconnect orbiting through GWO Phase 1 which is a La Nina attractor phase. Ergo, the atmospheric circulation is acting "destructively" (currently) on the ocean base state c/o this disconnect. The retrograde -ve inertia phase (easterly) is proving increasingly prolonged. The -ve MT periodicity, as mentioned above, relates to lag timescales of up to 12 days from when westerly winds start to be re-added in the tropics (c/o high frequency MJO/CCKW activity). These initial westerly wind additions are represented by frictional torque momentum (i,e a surface flow inflection convergence point created where these re-added westerly winds meet the easterly inertia that the -ve torqe processes had dumped into the atmospheric circulation) New WWB additions added can be seen on the equatorial scale of the FT plot. Over time, these propagate through the tropics into the extra tropics Consolidated GSDM data lags by about 2 days. There are signs of an uptick just beginning in the re-addition of WWB's as the next tropical convection cycle propagates eastwards though the tropics. This signal requires a few days monitoring for persistence - hence the suggestion to not jump on each and every day intra day modelling suite - especially based on the lagged periodicity for the existing -ve MT effects to be eradicated from the extra tropical circulation (ahead of the propagation of renewed WWB's) From all this, it is possible to see how numerical models might be too blindsided by the strength of the prevailing signal (and its periodicity timescale) However, in the outlook period at some stage the numerical models become increasingly likely to screech into reverse as they start to see what is ahead of the roadblock. The mantra remains that the last third of the summer may ensure a bookended season - with a seasonal disconnect as at present in the middle. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4888563

Modelling forecasts from ECM, as a quality example, in respect of AAM will give some insight into the numerical models synoptic outlook. More reliable in respect of initiation data etc than the CFS vs 2 AAM forecast on that mapwall site. However, if the numerical models (including ECM) are blindsided by the strength of an existing diagnostic signal this can, and sometimes does, create errors in extrapolating the length of that signal forward. This is the essence of the posts being made of late in terms of trying to urge caution in too much fixation with extended NWP. With all that in mind, its worth looking again at the actual consolidated GSDM data to try to get some clues as to the longevity of the AAM lull and how it is possible that some blindsiding may increasingly likely to be in operation. As posted a few times, large amounts of surplus westerly winds ( Nino-esque inertia) have been scrubbed from the extra tropical circulation. These surplus +AAM windflow anomalies ensured the downstream ridging of the first part of the summer. Sub seasonal effects such as the Indian monsoon are now scrambling the low frequency Nino ENSO signal & feedbacks are emanating from a more Nina-esque background in the absence of high frequency forcing in the Pacific which drove the early part of the summer. The periodicity of the -ve MT is predicated on largescale retrograde effects in both tropical and extra tropical mountain torques. Total aggregate MT in both tropics & extra tropics has fallen this week to -ve 3 standard deviations (from parity). The -ve inertia is identified by the circled anomaly on the plot and the reflected arrowed aggregate STD drop. (There is also -ve inertia corresponded in the SH c/o South America Andes -ve MT processes) Based on the increasingly El Nino-esque base state, a very large disconnect is in process and consequently a very unstable GSDM profile - with the Global Wind Oscillation advertising this disconnect orbiting through GWO Phase 1 which is a La Nina attractor phase. Ergo, the atmospheric circulation is acting "destructively" (currently) on the ocean base state c/o this disconnect. The retrograde -ve inertia phase (easterly) is proving increasingly prolonged. The -ve MT periodicity, as mentioned above, relates to lag timescales of up to 12 days from when westerly winds start to be re-added in the tropics (c/o high frequency MJO/CCKW activity). These initial westerly wind additions are represented by frictional torque momentum (i,e a surface flow inflection convergence point created where these re-added westerly winds meet the easterly inertia that the -ve torqe processes had dumped into the atmospheric circulation) New WWB additions added can be seen on the equatorial scale of the FT plot. Over time, these propagate through the tropics into the extra tropics Consolidated GSDM data lags by about 2 days. There are signs of an uptick just beginning in the re-addition of WWB's as the next tropical convection cycle propagates eastwards though the tropics. This signal requires a few days monitoring for persistence - hence the suggestion to not jump on each and every day intra day modelling suite - especially based on the lagged periodicity for the existing -ve MT effects to be eradicated from the extra tropical circulation (ahead of the propagation of renewed WWB's) From all this, it is possible to see how numerical models might be too blindsided by the strength of the prevailing signal (and its periodicity timescale) However, in the outlook period at some stage the numerical models become increasingly likely to screech into reverse as they start to see what is ahead of the roadblock. The mantra remains that the last third of the summer may ensure a bookended season - with a seasonal disconnect as at present in the middle.

(Fairly) briefly two things 1) The comments related to the current snapshot of the middle to latter part of July - which as was explained does not really constitute an LRF within the wider discussion on this thread that had been, by some, discrediting seasonal forecasts. Such seasonal forecasts being much closer to fitting the description of an LRF. Hence it rather gave the impression that the present departure from the default pattern of the summer to date meant that seasonal LRF's were somehow wrong b/c of the present 10 to 15 day outlook. 2) The rest of the post was a general address to the nature of some of the responses in the thread itself and not specific to the post under reply. It is possible to read the post back and see that this was actually made clear, There is a lot of (interesting) discussion outside of this thread about the ongoing disconnect of NWP vs the GSDM & teleconnectic outlook which is where the repeated suggestions come from that NWP is over egging the sustainability of the latest low AAM signal in the longer term. It is on that basis that the idea of sitting back and measuring this dichotomy over at least a few days might be better than jumping over each and every NWP suite each day as if to declare the "the teleconnections don't work" . This kind of situation can and clearly does take some time to resolve and in the time it does take it is possible to gather more data and update about progress and provide further answers and explanations. This is just not possible to do when that time is not allowed to gather that data as more diagnostic information comes in.. Being only at the half way point of the month and indeed summer itself it seems a sensible thing to do before jumping to conclusions. That was one of the central points in the general address and part of the frustration. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4888257

(Fairly) briefly two things 1) The comments related to the current snapshot of the middle to latter part of July - which as was explained does not really constitute an LRF within the wider discussion on this thread that had been, by some, discrediting seasonal forecasts. Such seasonal forecasts being much closer to fitting the description of an LRF. Hence it rather gave the impression that the present departure from the default pattern of the summer to date meant that seasonal LRF's were somehow wrong b/c of the present 10 to 15 day outlook. 2) The rest of the post was a general address to the nature of some of the responses in the thread itself and not specific to the post under reply. It is possible to read the post back and see that this was actually made clear, There is a lot of (interesting) discussion outside of this thread about the ongoing disconnect of NWP vs the GSDM & teleconnectic outlook which is where the repeated suggestions come from that NWP is over egging the sustainability of the latest low AAM signal in the longer term. It is on that basis that the idea of sitting back and measuring this dichotomy over at least a few days might be better than jumping over each and every NWP suite each day as if to declare the "the teleconnections don't work" . This kind of situation can and clearly does take some time to resolve and in the time it does take it is possible to gather more data and update about progress and provide further answers and explanations. This is just not possible to do when that time is not allowed to gather that data as more diagnostic information comes in.. Being only at the half way point of the month and indeed summer itself it seems a sensible thing to do before jumping to conclusions. That was one of the central points in the general address and part of the frustration.

I live in Portugal, so at face value should be ambivalent about the work in progress of a UK summer that (like everywhere else in the NH) is barely half way through. But scrutiny based on 10 to 15 days of the middle third of July does not change a whole seasonal perspective half way through that season and apparently override the known outcome that preceded it for a whole first month of summer (which broke national UK records). The actual "LRF" under discussion is not even the first 20 days of July. It is based, as stated above, on expectations for the middle to latter third of the month. Which is not in the true sense even an LRF at all..... This quoted post also ignores the fact that the first 10 days of July blended out overall in itself is still very close to the suggested seasonal anomaly and that which the diagnostic elements towards framing the summer as a whole were based on. Even taking into account many, including my humble self, overlooking the depth of the retrograde low angular momentum period which now dominates that middle to latter part of July. Notwithstanding that, the seasonal diagnostic (framing a true LRF & not an intra monthly interlude within that season as a whole) is equally pertinent still with a whole month of summer to go which has been discussed in detail for all that could, and very well might entail,.Unless doubt on that is also already being made- subject to the (apparent) absolutes of face value numerical modelling. Contributions to a voluntary forum by a mix of amateur, professional & simply weather pattern studiers like myself are not paid for. Yet, and speaking more generally outside the response to the quoted post, some of the commentary on this thread acts under a microscope that reacts emotionally to numerical model output and does not attempt to listen to, or understand the complexities behind the diagnostics that drive the weather patterns. No-one owes anyone else anything on here - especially as many of those who criticise the most offer little themselves in terms of attempted insight. As such, and with so much else of more importance to do in the real world, it is, frankly, quite reasonable to wonder if there is any point in taking spare time out to bother.

Based on a record breaking June (in UK) and the first 10 days of July actually perfectly respectable against long term temperature averages, there is a lot of excess reactivity instead of proactivity to be waded & skipped through. Considering calling time on seasonal LTF's is just as absurd (based on a good match overall so far) and extrapolating weeks ahead at a time based on face value numerical model interpretations. Signals lead models, not the other way around - and models do always read signals impeccably particularly in periods of excess of 10 to 15 days ahead. The facts are repeatedly laid out as to how & why the pattern is the way it is and what will change it (and will change it) Latest GSDM updated consolidated data confirms a full volte face to a Nina-esque type of forcing, so the synoptic response should not be a surprise with such a collapse of angular momentum, As part of the broken record, one context of this is a natural lull in the mini ENSO cycle ahead of the next upswing (and associated reconfiguring of the pattern which for NW Europe means a return to more summer like weather) It just so happens that this cyclical downturn has coincided with (part) of the peak of summer. However, another context is the record breaking June that came before it & the fact that this lull phase is not long term sustainable. Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4887663

Based on a record breaking June (in UK) and the first 10 days of July actually perfectly respectable against long term temperature averages, there is a lot of excess reactivity instead of proactivity to be waded & skipped through. Considering calling time on seasonal LTF's is just as absurd (based on a good match overall so far) and extrapolating weeks ahead at a time based on face value numerical model interpretations. Signals lead models, not the other way around - and models do always read signals impeccably particularly in periods of excess of 10 to 15 days ahead. The facts are repeatedly laid out as to how & why the pattern is the way it is and what will change it (and will change it) Latest GSDM updated consolidated data confirms a full volte face to a Nina-esque type of forcing, so the synoptic response should not be a surprise with such a collapse of angular momentum, As part of the broken record, one context of this is a natural lull in the mini ENSO cycle ahead of the next upswing (and associated reconfiguring of the pattern which for NW Europe means a return to more summer like weather) It just so happens that this cyclical downturn has coincided with (part) of the peak of summer. However, another context is the record breaking June that came before it & the fact that this lull phase is not long term sustainable.

This summary and the sentiments about NWP vs GSDM diagnostic is something I especially agree with based on repetition of such in so many of my own analyses. Clear evidence by way of consolidated GSDM data as to why we are where we are currently. Large scale upstream deceleration of wind-flow underway in the extra tropics as westerly inertia is scrubbed out of the atmospheric circulation c/o -ve mountain torque processes. Angular momentum tendency accordingly taking this cue downwards & in turn leads leads aggregate global AAM through the parity boundary to enter -ve total budget wind-flow. The Global Wind Oscillation, the phase plot depiction of the above data, moves accordingly through transitional Phase 8 towards La Nina forcing phase 1. All adding up to a negative Nina-esque type interval underway as advertised by the retracted upstream pattern forging a downstream Atlantic ridge and NW Europe & Scandinavian trough. The looping jet between the broad-scale features creates a "sink" as it dives towards southern Europe. Good explanation here: This, in contrast to the relatively cool unsettled conditions on the polar side of the looping jet across NW Europe. All the analysis has been given as to what is required to lift out the ongoing pattern including detailed description of the eastward propagating tropical convection forcing to ultimately return westerly inertia from upstream and reconfigure the downstream jet profile in the extra tropics. The notion that NWP will be prone to change of tack becomes stronger and the status quo less sustainable the longer it tries to keep churning out the same old. I would not put too much purchase in extended data at present, especially that which retains the downstream trough all the way into August. Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4886926

This summary and the sentiments about NWP vs GSDM diagnostic is something I especially agree with based on repetition of such in so many of my own analyses. Clear evidence by way of consolidated GSDM data as to why we are where we are currently. Large scale upstream deceleration of wind-flow underway in the extra tropics as westerly inertia is scrubbed out of the atmospheric circulation c/o -ve mountain torque processes. Angular momentum tendency accordingly taking this cue downwards & in turn leads leads aggregate global AAM through the parity boundary to enter -ve total budget wind-flow. The Global Wind Oscillation, the phase plot depiction of the above data, moves accordingly through transitional Phase 8 towards La Nina forcing phase 1. All adding up to a negative Nina-esque type interval underway as advertised by the retracted upstream pattern forging a downstream Atlantic ridge and NW Europe & Scandinavian trough. The looping jet between the broad-scale features creates a "sink" as it dives towards southern Europe. Good explanation here: This, in contrast to the relatively cool unsettled conditions on the polar side of the looping jet across NW Europe. All the analysis has been given as to what is required to lift out the ongoing pattern including detailed description of the eastward propagating tropical convection forcing to ultimately return westerly inertia from upstream and reconfigure the downstream jet profile in the extra tropics. The notion that NWP will be prone to change of tack becomes stronger and the status quo less sustainable the longer it tries to keep churning out the same old. I would not put too much purchase in extended data at present, especially that which retains the downstream trough all the way into August.

Having jumped too soon with the early to mid July pattern in respect of the tropical>extra tropical wind-flow cycle & underestimated the strength of the present lull -ve inertia cycle, the onus still remains as to "when" rather than "if" the upswing returns. Not an official forecaster but am prepared to stick a neck out for the extended period in respect of a quite spectacular upswing with trough amplification in the Atlantic finally killing off the Atlantic blocking and driving a replacement trough and strong downstream ridge. Extended GEFS most especially & to some extent CFS tropical convection products are day by day ramping up expectations of a high amplitude tropical convection wave (CCKW related as spoken about in previous posts) to propagate eastwards to the Pacific and probably finally provide a sustained ocean>atmosphere coupling of El Nino. ECM is, presently, lower key with this suggestion, but the RMM plot tends to erroneously "lose" signal progression within the Maritime continent and subsequently fade the signal before making much inroads into the Pacific. Taking into account MJO periodicity of 60 to 90 days of amplitude high frequency tropical convection cycles, this event would be on the later timescale end of that envelope, based on the previous strong intraseasonal activity seen in May. So such an event, taking into account the current ENSO transition and CCKW events which progress the evolution of these, is therefore due within diminishing limits of time. Taking into account spatial warmth of SST arrangement across the Western Pacific and sub surface heat anomalies, such a CCKW has quite the hallmarks to be a significant inducer of pattern shift for the last third of the summer as strong tropical convection convergence, and associated deep thunderstorm development, becomes more coherent across the Pacific It would also be guaranteed to see angular momentum tendency soar with a fast reversal in the presently -ve extra tropical torque mechanisms leading to re-configuration of the jet stream and a split flow returning lower pressure to the west and south west of Europe and ridging downstream across mainland Europe into Scandinavia. Assuming a bone fide credence to this signal (and there is credence) then extended modelling has to accord with the diagnostic at some stage and start to blow a hole in the Atlantic ridge and dissolve the downstream trough on the way to reversing it. August the hottest month of the summer for NW Europe? Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4886388

Having jumped too soon with the early to mid July pattern in respect of the tropical>extra tropical wind-flow cycle & underestimated the strength of the present lull -ve inertia cycle, the onus still remains as to "when" rather than "if" the upswing returns. Not an official forecaster but am prepared to stick a neck out for the extended period in respect of a quite spectacular upswing with trough amplification in the Atlantic finally killing off the Atlantic blocking and driving a replacement trough and strong downstream ridge. Extended GEFS most especially & to some extent CFS tropical convection products are day by day ramping up expectations of a high amplitude tropical convection wave (CCKW related as spoken about in previous posts) to propagate eastwards to the Pacific and probably finally provide a sustained ocean>atmosphere coupling of El Nino. ECM is, presently, lower key with this suggestion, but the RMM plot tends to erroneously "lose" signal progression within the Maritime continent and subsequently fade the signal before making much inroads into the Pacific. Taking into account MJO periodicity of 60 to 90 days of amplitude high frequency tropical convection cycles, this event would be on the later timescale end of that envelope, based on the previous strong intraseasonal activity seen in May. So such an event, taking into account the current ENSO transition and CCKW events which progress the evolution of these, is therefore due within diminishing limits of time. Taking into account spatial warmth of SST arrangement across the Western Pacific and sub surface heat anomalies, such a CCKW has quite the hallmarks to be a significant inducer of pattern shift for the last third of the summer as strong tropical convection convergence, and associated deep thunderstorm development, becomes more coherent across the Pacific It would also be guaranteed to see angular momentum tendency soar with a fast reversal in the presently -ve extra tropical torque mechanisms leading to re-configuration of the jet stream and a split flow returning lower pressure to the west and south west of Europe and ridging downstream across mainland Europe into Scandinavia. Assuming a bone fide credence to this signal (and there is credence) then extended modelling has to accord with the diagnostic at some stage and start to blow a hole in the Atlantic ridge and dissolve the downstream trough on the way to reversing it. August the hottest month of the summer for NW Europe?

There is a lot of truth that this sort of downstream pattern pleases very few. In south west Europe heat is static in situ and just keeps building to such unpleasant levels which even the natives find difficult. The sub tropical jet stream pattern of early summer provided the best of many worlds - with values of 27C to 32C by day with sunny mornings and then thundery showers later in the day based on the (relatively) cooler uppers and lower pressure providing lapse rate instability in very strong insolation. Yes,some of these storms were destructive to agriculture & farming & caused flash flooding issues, but for many others who missed the strongest storms they simply provided some much needed rainfall to replenish the ecosystem They also provided spectacular weather watching. This diurnal convection faded through the evening to leave comfortably warm nights for sleeping. Though the events referred to were certainly destructive, the above perspective kind of also addresses this post. Conversely to the situation across southern Europe, higher pressure across Northern Europe gave the settled June (after a cool end to Spring) and as the low pressure anomaly west of Iberia increased its influence, then the thundery weather also migrated northwards as part of the classic summer feel. Now in the forthcoming outlook in the UK, the -ve AAM inertia pattern traps the cooler unsettled conditions in situ in the same way as the escalating excessive heat goes nowhere in southern Europe. A +ve or neutral profile across the polar field combined with a slightly -ve NAO in summer can provide some of the best summer weather across large regions of both NW and SW Europe - with the rinse and repeat mobile plumes a feature rather than trapped excessive heat to the south and trapped cool troughs to the north. Very much an extension of the sequence presently in the UK before the trough dominates in the wrong place. At the same time there is nothing to dislodge the intense heat static over North Africa and southern Spain & Portugal. 45C day after day and 24C night after night very quickly becomes intolerable. My own location looks to be on the periphery of next weeks main heat and with the "nortada" blowing in the afternoons from the Atlantic to also temper the heat. Based on factors as discussed, still every reason to anticipate something to emerge closer to returning to the expected long range seasonal modelling. The suggested synoptic outlook for this modelling after all had good diagnostic evidence to underpin it (and still does). The present rut should not detract from dismissing it and writing it off the rest of the summer as a whole. Especially on the back of a very noteworthy June. I wouldn't expect the GEFS mean to offer much useful guidance at all at especially at such a distance. The outlook that is going to evolve will never be picked out amidst so much over smoothed "noise". In many ways that is a good thing. As soon as the numerical models jump on to renewed VP200 convection anomalies re-stirring in the Pacific they will act like a shoal of fish and change direction in midstream...On that basis, also a good thing b/c it makes cut and paste numerical model extrapolation of the same stuck pattern somewhat mute.

Yes, It could well be Much tied into the following discussion and the timing of the mechanisms required to do so. This timing, much as people like @MattH fairly recently mentioned might be the case, is proving very problematic. Respectful genuine enquiries are welcomed, very much including when curveballs occur, and are helpful for all concerned Curveballs always provide new learning opportunities for all with (genuine) interest A question therefore related to an incorrect assertion of the NW European trough not being as as short lived as suggested, indeed readily admitting very much expected to be short lived, is a very reasonable one. Much of the emphasis about an Atlantic trough and downstream ridge related to the switch on the doorstep this weekend. And this has largely verified as suggested at intervals since the last third of June. This synoptic passage largely has been at the behest of short term "mini ENSO cycle" tropical>extra tropical cycling of westerly inertia to keep re-cycling June's (mostly) default pattern into July. There has been remarkable forcing from high frequency tropical convection injecting westerly wind burst inertia into the extra tropics since the Spring and the persistent anticyclonic wave breaking that has resulted. The record breaking June in the UK didn't happen for nothing after all... The anticipation of this re-cycling continuing through the heart of the summer, and, in fact, impacting even more strongly the synoptic pattern downstream across many central and NW parts of Europe has been (and still is) predicated on a meaningful shift of low frequency tropical convection cementing a more permanent Nino-esque ocean-atmosphere feedback. The timing of this has clearly proved much more problematic across the board in respect of longer range predications with diagnostic modelling (which determines numerical modelling) pointing to this sooner rather than later, Hence quite reasonable not to have expected any trough related solution across NW Europe to be prolonged. These particular summaries are also not UK centric & take into account macro regional synoptics, (including interests closer to home in Portugal) At present there are complex low frequency convergence signals across the Pacific, Atlantic and African continent which are scrambling the wind-flow (jetstream) feedbacks and meaning that there is no fluid inertia across the Pacific and stubborn trade wind effects are impeding the progress, currently, of Nino feedbacks in the Pacific. This means that split flow from upstream to downstream, introducing a more sustained sub tropical element of flow ( such sub tropical flow as was seen under the strong high frequency MJO driven forcing back in June) is not materialising as anticipated (yet). This delayed absence allows a retracted Atlantic/Azores ridge to retain stubborn strength and with a looped jet flow above and around a +NAO signature. The trough therefore sustained longer than expected. It is true in this respect that the extraordinary Maritime heat is not helping with the fuel provided for these disturbances and self perpetuating their longevity. The lull in the high frequency signal breaking down the westerly propagation in the tropics, and in the absence of the coherent low frequency convergence appearing in the Pacific creates a decelerating forcing (-ve low level flow frictional torque on the jetstream) and setting in motion further retrograde pull on extra tropical mountain torques in the extra tropics. This now looks likely to keep extra tropical torque mechanisms suppressed over the coming 10 to 15 days based on feedback lags. With that in mind, the interest persists in seeing when that more "formal" atmosphere/ocean coupling occurs and puts a proper halt to this retrograde motion that is retracting the Azores ridge and keeping it stronger than expected and in turn enabling the trough to sustain ahead if it.. Change likely will happen when the next CCKW (convectively coupled kelvin wave) drives both oceanic and atmospheric shift to couple El Nino sustainably and subtly alter the messy low frequency feedbacks to a more cohesive Pacific convergence zone. This development removes trade wind blocks at, and east of the dateline. These trade winds shut the door on the jet stream being able to straddle the Equatorial Pacific into the Equatorial Atlantic and so not being able to weaken the Atlantic/Azores ridging - much as often discussed in earlier summaries in late Spring and early summer when MJO driven forcing enabled sub tropical flow in a classic El Nino synoptic response A shift in the displaced Azores heights will be equally welcome down here in reducing build up of stagnant heat. This, rather that cyclical more mobile plume like heat building from south to north (and then repeating) which has been defined as the more likely default for the summer. Based on the above analysis, it still remains the case this is likely to happen & despite errors in recent estimations. The question remains the timing - and it is sensible to wait on this for the time being. NWP is not going to read such a signal especially well - so rules about baseless extrapolations of numerical model output still hold true, even at times when Mother Nature has just thrown a curveball. Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4883151

Yes, It could well be Much tied into the following discussion and the timing of the mechanisms required to do so. This timing, much as people like @MattH fairly recently mentioned might be the case, is proving very problematic. Respectful genuine enquiries are welcomed, very much including when curveballs occur, and are helpful for all concerned Curveballs always provide new learning opportunities for all with (genuine) interest A question therefore related to an incorrect assertion of the NW European trough not being as as short lived as suggested, indeed readily admitting very much expected to be short lived, is a very reasonable one. Much of the emphasis about an Atlantic trough and downstream ridge related to the switch on the doorstep this weekend. And this has largely verified as suggested at intervals since the last third of June. This synoptic passage largely has been at the behest of short term "mini ENSO cycle" tropical>extra tropical cycling of westerly inertia to keep re-cycling June's (mostly) default pattern into July. There has been remarkable forcing from high frequency tropical convection injecting westerly wind burst inertia into the extra tropics since the Spring and the persistent anticyclonic wave breaking that has resulted. The record breaking June in the UK didn't happen for nothing after all... The anticipation of this re-cycling continuing through the heart of the summer, and, in fact, impacting even more strongly the synoptic pattern downstream across many central and NW parts of Europe has been (and still is) predicated on a meaningful shift of low frequency tropical convection cementing a more permanent Nino-esque ocean-atmosphere feedback. The timing of this has clearly proved much more problematic across the board in respect of longer range predications with diagnostic modelling (which determines numerical modelling) pointing to this sooner rather than later, Hence quite reasonable not to have expected any trough related solution across NW Europe to be prolonged. These particular summaries are also not UK centric & take into account macro regional synoptics, (including interests closer to home in Portugal) At present there are complex low frequency convergence signals across the Pacific, Atlantic and African continent which are scrambling the wind-flow (jetstream) feedbacks and meaning that there is no fluid inertia across the Pacific and stubborn trade wind effects are impeding the progress, currently, of Nino feedbacks in the Pacific. This means that split flow from upstream to downstream, introducing a more sustained sub tropical element of flow ( such sub tropical flow as was seen under the strong high frequency MJO driven forcing back in June) is not materialising as anticipated (yet). This delayed absence allows a retracted Atlantic/Azores ridge to retain stubborn strength and with a looped jet flow above and around a +NAO signature. The trough therefore sustained longer than expected. It is true in this respect that the extraordinary Maritime heat is not helping with the fuel provided for these disturbances and self perpetuating their longevity. The lull in the high frequency signal breaking down the westerly propagation in the tropics, and in the absence of the coherent low frequency convergence appearing in the Pacific creates a decelerating forcing (-ve low level flow frictional torque on the jetstream) and setting in motion further retrograde pull on extra tropical mountain torques in the extra tropics. This now looks likely to keep extra tropical torque mechanisms suppressed over the coming 10 to 15 days based on feedback lags. With that in mind, the interest persists in seeing when that more "formal" atmosphere/ocean coupling occurs and puts a proper halt to this retrograde motion that is retracting the Azores ridge and keeping it stronger than expected and in turn enabling the trough to sustain ahead if it.. Change likely will happen when the next CCKW (convectively coupled kelvin wave) drives both oceanic and atmospheric shift to couple El Nino sustainably and subtly alter the messy low frequency feedbacks to a more cohesive Pacific convergence zone. This development removes trade wind blocks at, and east of the dateline. These trade winds shut the door on the jet stream being able to straddle the Equatorial Pacific into the Equatorial Atlantic and so not being able to weaken the Atlantic/Azores ridging - much as often discussed in earlier summaries in late Spring and early summer when MJO driven forcing enabled sub tropical flow in a classic El Nino synoptic response A shift in the displaced Azores heights will be equally welcome down here in reducing build up of stagnant heat. This, rather that cyclical more mobile plume like heat building from south to north (and then repeating) which has been defined as the more likely default for the summer. Based on the above analysis, it still remains the case this is likely to happen & despite errors in recent estimations. The question remains the timing - and it is sensible to wait on this for the time being. NWP is not going to read such a signal especially well - so rules about baseless extrapolations of numerical model output still hold true, even at times when Mother Nature has just thrown a curveball.

Based in Portugal the concern is about ongoing intense heat levels in respect of IMBY details. But those concerns are not for this thread. A bit of a broken record I know, but the situation for UK/NW Europe continues to revolve around interplay between a re-setting Atlantic trough and downstream ridge. The expressed thought developing and recurring in these updates has been that what is most likely is a rinse and repeat cycle with high pressure ridging in following a thundery breakdown and then things settling down a bit...and in turn followed by another slowing Atlantic trough advancing to buffer up against that ridge. Happily increasing amounts of NWP are bearing that out -with variations around a theme and around timing of the chronology of events. The GEM numerical model is rather underrated by many and is often by-passed due to scrutiny of the rest of NWP (especially over scrutiny of the GFS). But it is much respected by UK METO (and indeed f.e IPMA here in Portugal) Looking through the entire members of the latest suite actually gives a very good overview to back a very interesting outlook. EPS has members with a similar progression. Many of the GEM solutions that place the trough close to UK/NW Europe next weekend and into the start of the following week thereafter go on to either reload amplification of the trough to the west in the Atlantic and resurrect a follow up heat plume, or, the trough warms out and is replaced by high pressure (and a trough re-setting to the west) Strikingly a common theme in quite a lot of them is the build of significant heat across large areas of Europe (and this includes into many parts of the UK) The precise weather implicated on any given day(s) based on any intra day model run (usually GFS) for a random bench overlooking an English Riviera sea view, or outside an amusement arcade in Skegness is better posted in the relevant echo chamber. In honesty, if one is prepared to see past the noise of intra day operational model output (mostly again GFS) its hard to see what there is not to show at least an interest in . Especially as suggested might be the case, the numerical models will stumble with the upcoming pattern. Notwithstanding that, extended periods of Azores High dominance have not been deemed likely this summer - with sequences of sub tropical jet flow introducing spells of changeability & instability. This is a summer that looks set to above average overall, but not long spells of settled wall to wall sunshine With that punctuated emphasis in mind, and to reiterate what could well happen following on from the upcoming sequences is when the hottest weather of the summer may very well show its hand from the south.....I would/will be one of the first to give advance warning of that. Much like the middle/latter part of July last year. It is the second day of the month.. There is an infinitely much bigger picture than the one you are extrapolating forward. Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4881086

Based in Portugal the concern is about ongoing intense heat levels in respect of IMBY details. But those concerns are not for this thread. A bit of a broken record I know, but the situation for UK/NW Europe continues to revolve around interplay between a re-setting Atlantic trough and downstream ridge. The expressed thought developing and recurring in these updates has been that what is most likely is a rinse and repeat cycle with high pressure ridging in following a thundery breakdown and then things settling down a bit...and in turn followed by another slowing Atlantic trough advancing to buffer up against that ridge. Happily increasing amounts of NWP are bearing that out -with variations around a theme and around timing of the chronology of events. The GEM numerical model is rather underrated by many and is often by-passed due to scrutiny of the rest of NWP (especially over scrutiny of the GFS). But it is much respected by UK METO (and indeed f.e IPMA here in Portugal) Looking through the entire members of the latest suite actually gives a very good overview to back a very interesting outlook. EPS has members with a similar progression. Many of the GEM solutions that place the trough close to UK/NW Europe next weekend and into the start of the following week thereafter go on to either reload amplification of the trough to the west in the Atlantic and resurrect a follow up heat plume, or, the trough warms out and is replaced by high pressure (and a trough re-setting to the west) Strikingly a common theme in quite a lot of them is the build of significant heat across large areas of Europe (and this includes into many parts of the UK) The precise weather implicated on any given day(s) based on any intra day model run (usually GFS) for a random bench overlooking an English Riviera sea view, or outside an amusement arcade in Skegness is better posted in the relevant echo chamber. In honesty, if one is prepared to see past the noise of intra day operational model output (mostly again GFS) its hard to see what there is not to show at least an interest in . Especially as suggested might be the case, the numerical models will stumble with the upcoming pattern. Notwithstanding that, extended periods of Azores High dominance have not been deemed likely this summer - with sequences of sub tropical jet flow introducing spells of changeability & instability. This is a summer that looks set to above average overall, but not long spells of settled wall to wall sunshine With that punctuated emphasis in mind, and to reiterate what could well happen following on from the upcoming sequences is when the hottest weather of the summer may very well show its hand from the south.....I would/will be one of the first to give advance warning of that. Much like the middle/latter part of July last year. It is the second day of the month.. There is an infinitely much bigger picture than the one you are extrapolating forward.

Some of these US twitter gurus tend to become too ENSO centric without considering the extra tropical Global Wind Oscillation as a benchmark of both tropical AND extra tropical wind-flow signal on the ocean ENSO evolution The GWO is a phase plot depiction of the wind-flow relationship between the tropics & extra tropics and as such angular momentum is driven according to whether the atmospheric circulation is either adding momentum (+AAM) or decelerating momentum(-ve AAM) between the tropics and extra tropics. In respect of this diagnostic, it is a consolidated bellweather data proxy to test/analyse/gauge strength forcing of atmospheric circulation inertia on ENSO ocean state. Also, as stressed in so many of these analyses, the "mini ENSO cycle" aka MJO & relevant low frequency tropical convection cycles exercise natural ebb and flow in this relationship. It is not as linear and ENSO " one size fits all" as some of these tweet gurus suggest. It is much more sinuous and and requires a more flexible approach So a very simple way to look at what is meant here is to take a look at the GWO itself. Broken down into both 90 day and 40 day plots the ascendancy of newly coupling El Nino forcing from atmosphere to ocean is seen most emphatically. Clearly, based on the high amplitude orbit of the GWO through the "El Nino attractor phases" 5 to 7 during May and into June, a very harmonious +ve AAM wind-flow signal has contributed a considerable effort towards coupling of the atmosphere and ocean. This very strong sequence of westerly wind bursts were generated in the tropics during Spring and have persistently propagated into the extra tropics - driving a series of wave-breaking events and associated downstream amplification in the extra tropics itself. The arrangement of the downstream Atlantic/European pattern during that phase has been classically Nino-esque. The eye catching significant split jet & sub tropical jet stream strength has been the subject of many analysis posts made in this time as reference to the evolution of the late Spring and early Summer downstream pattern. As commented a few times in various recent posts, all that is happening presently is a natural lull to that inertia cycle. A Nino-esque forcing on atmosphere will lead the ocean evolution to such a Nino SST imprint, which in turn can become self re-enforcing, but the tropics & extra tropics require being kept acting in harmony to keep a given ENSO imprint sustained. That looks set to keep happening. Some of these tweets tend to appear to look at this relationship back to front -or simply not consider the GWO imprint at all. With all this in mind, it is not going to take much renewed forcing of westerly inertia to further strengthen the coupling - which is only in very temporary and very tenuous "disconnect" (it is not truly disconnected at all in the true sense) due to the natural lull of the mini ENSO cycle. Looking ahead at a renewed GWO "Nino attractor" period of wind-flow cycling with the associated wind-flow propagation from tropics into extra tropical to inflate downstream amplification and trough/ridge pattern arrangement respectively once again. Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4880651

Some of these US twitter gurus tend to become too ENSO centric without considering the extra tropical Global Wind Oscillation as a benchmark of both tropical AND extra tropical wind-flow signal on the ocean ENSO evolution The GWO is a phase plot depiction of the wind-flow relationship between the tropics & extra tropics and as such angular momentum is driven according to whether the atmospheric circulation is either adding momentum (+AAM) or decelerating momentum(-ve AAM) between the tropics and extra tropics. In respect of this diagnostic, it is a consolidated bellweather data proxy to test/analyse/gauge strength forcing of atmospheric circulation inertia on ENSO ocean state. Also, as stressed in so many of these analyses, the "mini ENSO cycle" aka MJO & relevant low frequency tropical convection cycles exercise natural ebb and flow in this relationship. It is not as linear and ENSO " one size fits all" as some of these tweet gurus suggest. It is much more sinuous and and requires a more flexible approach So a very simple way to look at what is meant here is to take a look at the GWO itself. Broken down into both 90 day and 40 day plots the ascendancy of newly coupling El Nino forcing from atmosphere to ocean is seen most emphatically. Clearly, based on the high amplitude orbit of the GWO through the "El Nino attractor phases" 5 to 7 during May and into June, a very harmonious +ve AAM wind-flow signal has contributed a considerable effort towards coupling of the atmosphere and ocean. This very strong sequence of westerly wind bursts were generated in the tropics during Spring and have persistently propagated into the extra tropics - driving a series of wave-breaking events and associated downstream amplification in the extra tropics itself. The arrangement of the downstream Atlantic/European pattern during that phase has been classically Nino-esque. The eye catching significant split jet & sub tropical jet stream strength has been the subject of many analysis posts made in this time as reference to the evolution of the late Spring and early Summer downstream pattern. As commented a few times in various recent posts, all that is happening presently is a natural lull to that inertia cycle. A Nino-esque forcing on atmosphere will lead the ocean evolution to such a Nino SST imprint, which in turn can become self re-enforcing, but the tropics & extra tropics require being kept acting in harmony to keep a given ENSO imprint sustained. That looks set to keep happening. Some of these tweets tend to appear to look at this relationship back to front -or simply not consider the GWO imprint at all. With all this in mind, it is not going to take much renewed forcing of westerly inertia to further strengthen the coupling - which is only in very temporary and very tenuous "disconnect" (it is not truly disconnected at all in the true sense) due to the natural lull of the mini ENSO cycle. Looking ahead at a renewed GWO "Nino attractor" period of wind-flow cycling with the associated wind-flow propagation from tropics into extra tropical to inflate downstream amplification and trough/ridge pattern arrangement respectively once again.

Most of the nonsense is either reaction seeking spam or simply ridiculously overreactive and lacking in any substance and belongs either in the bin or in the one line chat threads. As posted previously, numerical modelling will continue to stumble erratically back to a re-set of the Atlantic trough & downstream ridge. Westerly inertia in the central Pacific will start to drive some split jet stream flow back further downstream in the extended period and a change of amplification axis promote a digging south in the Atlantic of the trough to inflate that downstream ridge and resultant advection of some significant heat. This needs watching for possible further adjustments in forthcoming modelling. Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4879674

Most of the nonsense is either reaction seeking spam or simply ridiculously overreactive and lacking in any substance and belongs either in the bin or in the one line chat threads. As posted previously, numerical modelling will continue to stumble erratically back to a re-set of the Atlantic trough & downstream ridge. Westerly inertia in the central Pacific will start to drive some split jet stream flow back further downstream in the extended period and a change of amplification axis promote a digging south in the Atlantic of the trough to inflate that downstream ridge and resultant advection of some significant heat. This needs watching for possible further adjustments in forthcoming modelling.

This is good analysis based on this numerical model evolution & matches previous diagnostic summaries of late which suggested not getting too embroiled in the NW European trough scenario sticking around for the long term. Though in the extended period, the precise timing of this is less important than the trend towards it over the coming 10 to 15 days. The latter is consistent with the re-setting of the summer default pattern, which as you say, is reminiscent of what was seen from the second week of June. I would trust in this trend getting increased support in numerical modelling as a whole in the coming days. From my point of view such an evolution is equally welcome as it dislodges the excess heat from the Iberian peninsula, trapped under the Atlantic/Azores ridging, and that surplus heat is eventually advected further north and east which in turn improves the prospects for UK/NW Europe. Less anomalously hot down here in this part of the Iberian peninsula equates to ideal outdoor summer weather as the middle daylight hours have prohibited doing much since late last week. Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4878743