Tamara

Hello Matt. Already consistent upward trend in frictional torque at 30N (wind-flow additions according to jet eddy oscillations running parallel to their direction of travel within the tropics). These (westerly wind burst) wind-flow additions are set to change pressure differentials between tropics and sub tropics c/o the beginnings of the movement of the VP200 tropical convection anomaly to the Pacific - which should propagate +AAM anomalies (+ve AAM tendency) further towards the extra tropics in the time period you speak of. This changing dynamic has an ultimate effect on the strength of sub tropical ridging in the Atlantic. The Azores High in the Atlantic sector weakens according to a rising FT propagating from the tropics to the extra tropics. (The converse trend effect on the AZH also holds true) Subsequent tendency in Mountain Torques in the extra tropics is influenced by direction of travel of frictional torque tendency in the tropics. So the lifespan of such a torque (3 to 4 weeks) and its lagged effect in the extra tropics does point to falling pressure to the west and south west of Europe heading towards the second/third week of September as the Azores High weakens & downstream ridging evolves accordingly. This analysis of the dynamics of the atmospheric momentum changes that occur through interplay of tropical convection eddy anomalies propagating over time to the extra tropics fits well with the chronology of pattern change you outline and discuss over the end of summer/start of autumn period. In the scenario of Equatorial Atlantic developed tropical storms, and based on the evolution of the macro scale pattern though September to a trough/ridge structure in the Atlantic & European sector accordingly - these could serve one possible outcome where they bolster the amplification of upper troughs to the west in the Atlantic to push extra enhanced warm air advection draw ahead of them and sharpen the downstream ridge further. Not uncommon at all for the time of year under this type of macro pattern.

Um, yes she did The consolidated data AAM/torque plots now depict the -ve inertia clearly on latest update (subject to 2/3 days lag). The numerical models have done well with this retrograde signal at a distance. Its why I was intrigued to see the actual consolidated wind-flow data when I identified the modelling of it in a post last week. The Atlantic ridging and cooler air advection essentially cuts off progress of the main heat across the European continent that is advecting northwards from my part of the world during today, tomorrow and Thursday.. The weaker periphery of very warm +15 850's scrapes into SE England before defecting away south eastwards on Friday. Providing nice summer temperatures while it lasts rather than an inferno. It is also responsible for slowly pushing the stupid heat away from my part of the world after midweek. Roll on later Thursday and more especially Friday when pleasant (very warm) late summer temperatures return

I have suggested many times that the Hovmollers charts should be referenced alongside various other diagnostic proxies, not in isolation. In respect of an overview, there continues to be the summer disconnect between the Pacific and the Atlantic sectors. Another -ve NAMT (North American Mountain Torque) is effectively being signalled by the numerical models which overrides the split jet downstream flow from the Pacific and hence no longer supporting the sustaining of downstream ridging that had the potential to create a very hot finale to summer across greater parts of NW Europe including UK - and as discussed the other day. That potential more widespread heat is restricted accordingly, although many parts of France and into central Europe will still see a very hot spell before pressure falls from the NW and cooler air filters southwards. For the UK, especially in the south, it looks like pleasant enough temperatures with a range of low to mid/high twenties before cooler air arrives. Better than another round of above 40C to 44C in southern Europe. With that in mind - on the upside for SW Europe, this development should with luck (pending caveat in final paragraph) shift the stupid levels of N African heat dome influences further away more sustainably - and the next upcoming spell of excesses into the first half of next week will hopefully be the last one of this season (on basis that summer weather extends though September/October down here). Days of 27C to 32C heading towards and then into the start of autumn would be much more welcome. It could well be that the retrograde signal is less strong and lasting as that of July and ridging returns eastwards fairly quickly into the early part of September - but with such disconnect persisting between upstream and downstream and with such skewed micro scale anomalies, it is better to hold reserve on that b/c the next few days will reveal more about the strength of -ve torque inertia across the US. The models have different versions of this at present. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4907517

I have suggested many times that the Hovmollers charts should be referenced alongside various other diagnostic proxies, not in isolation. In respect of an overview, there continues to be the summer disconnect between the Pacific and the Atlantic sectors. Another -ve NAMT (North American Mountain Torque) is effectively being signalled by the numerical models which overrides the split jet downstream flow from the Pacific and hence no longer supporting the sustaining of downstream ridging that had the potential to create a very hot finale to summer across greater parts of NW Europe including UK - and as discussed the other day. That potential more widespread heat is restricted accordingly, although many parts of France and into central Europe will still see a very hot spell before pressure falls from the NW and cooler air filters southwards. For the UK, especially in the south, it looks like pleasant enough temperatures with a range of low to mid/high twenties before cooler air arrives. Better than another round of above 40C to 44C in southern Europe. With that in mind - on the upside for SW Europe, this development should with luck (pending caveat in final paragraph) shift the stupid levels of N African heat dome influences further away more sustainably - and the next upcoming spell of excesses into the first half of next week will hopefully be the last one of this season (on basis that summer weather extends though September/October down here). Days of 27C to 32C heading towards and then into the start of autumn would be much more welcome. It could well be that the retrograde signal is less strong and lasting as that of July and ridging returns eastwards fairly quickly into the early part of September - but with such disconnect persisting between upstream and downstream and with such skewed micro scale anomalies, it is better to hold reserve on that b/c the next few days will reveal more about the strength of -ve torque inertia across the US. The models have different versions of this at present.

Bearing in mind July, and then how early August turned out subsequent to writing it, its worth looking back at this post made on 10 July - in context with how the modelling is toying with precisely the suggested outcome based on the diagnostics described in that post....Just a few weeks later than was suggested! 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? ........................................................................................ The persistence of the N African sourced southern European heat dome through the summer, and its repeated attempts to try to influence greater parts of the continent, show how fine margins can produce very different outcomes for a micro scale geographical area. There has been a stark boundary between this fierce heat and the contrasting relatively cool maritime air across N Europe - which in itself produced repeated very high impact weather events across the central zone this summer. The truth is it has never taken much this summer for the trajectory of this heat to have been much more northward orientated and produce a truly inferno summer over much wider areas that would also have been knocking well on the door of the UK. That is, with less jet stream pressure induced by stupidly warm SST gradient induced anomalies in the Atlantic & a larger and more extensive repression of angular momentum that placed the polar jet in the downstream position to be further amplified by the spatial SST distribution within the Atlantic sector. As suggested above the pasted post caption, the modelling is toying with some of the more noteworthy outcomes for NW Europe that did not materialise as earlier expected. This is not a case of trying to claim some retrospective sense of being correct all along. It is simply down to these fine margins and especially as this site is devoted to a tiny island that is always on the cross roads of influences from all vectors, but most often from a large expanse of ocean upstream. For my part of SW Europe in Portugal - it has been all about bullet dodging. The truth is that the ever growing intensity and expansive influence of these heat domes are inherently dangerous and an increasing worry for the future. Values well in excess of 40C, when they happen more and more frequently and last longer periods of time, have obvious repercussions. Two/three days of these was more than enough in the first week of August IMBY (when 46C was recorded on the 7th) - but that was a small percentage compared to much of the Med earlier during July. Which Portugal largely escaped. However it is not over yet for this summer. Once again, from this weekend, another N African surge of heat heads northwards and yet again more values towards 45C restrict day to day routines for many in Southern Europe, and it also gets too hot IMBY again. The difference this time is that the expanse of this hot air advection has also some different geographical regions of Europe in its sight, and that also includes parts of the UK. So it could well end up true that August does manage to provide the hottest weather of the summer for NW Europe inc UK perhaps,, even if it is obviously another matter about it ending up the hottest month. At least in the UK based on the cooler weather of the first half of August. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4906416

Bearing in mind July, and then how early August turned out subsequent to writing it, its worth looking back at this post made on 10 July - in context with how the modelling is toying with precisely the suggested outcome based on the diagnostics described in that post....Just a few weeks later than was suggested! 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? ........................................................................................ The persistence of the N African sourced southern European heat dome through the summer, and its repeated attempts to try to influence greater parts of the continent, show how fine margins can produce very different outcomes for a micro scale geographical area. There has been a stark boundary between this fierce heat and the contrasting relatively cool maritime air across N Europe - which in itself produced repeated very high impact weather events across the central zone this summer. The truth is it has never taken much this summer for the trajectory of this heat to have been much more northward orientated and produce a truly inferno summer over much wider areas that would also have been knocking well on the door of the UK. That is, with less jet stream pressure induced by stupidly warm SST gradient induced anomalies in the Atlantic & a larger and more extensive repression of angular momentum that placed the polar jet in the downstream position to be further amplified by the spatial SST distribution within the Atlantic sector. As suggested above the pasted post caption, the modelling is toying with some of the more noteworthy outcomes for NW Europe that did not materialise as earlier expected. This is not a case of trying to claim some retrospective sense of being correct all along. It is simply down to these fine margins and especially as this site is devoted to a tiny island that is always on the cross roads of influences from all vectors, but most often from a large expanse of ocean upstream. For my part of SW Europe in Portugal - it has been all about bullet dodging. The truth is that the ever growing intensity and expansive influence of these heat domes are inherently dangerous and an increasing worry for the future. Values well in excess of 40C, when they happen more and more frequently and last longer periods of time, have obvious repercussions. Two/three days of these was more than enough in the first week of August IMBY (when 46C was recorded on the 7th) - but that was a small percentage compared to much of the Med earlier during July. Which Portugal largely escaped. However it is not over yet for this summer. Once again, from this weekend, another N African surge of heat heads northwards and yet again more values towards 45C restrict day to day routines for many in Southern Europe, and it also gets too hot IMBY again. The difference this time is that the expanse of this hot air advection has also some different geographical regions of Europe in its sight, and that also includes parts of the UK. So it could well end up true that August does manage to provide the hottest weather of the summer for NW Europe inc UK perhaps,, even if it is obviously another matter about it ending up the hottest month. At least in the UK based on the cooler weather of the first half of August.

This is another variety of the many x+y=theories on this forum which has no founding other than a sense of something anecdotal and hoped for to happen again. Finally some fragile coherence has come to the expected synoptic pattern vs diagnostic wind-flow pattern with downstream ridging and Atlantic trough as far as the European sector is concerned - but there is so much extreme oceanic micro forcing around the globe (very much including the Atlantic) that is now testing medium range diagnostic analysis to the limit, let alone seasonal predictions. Seasonal wavelength changes and the increasing gradient differentials between the cooling at the pole and the lagged heat in the tropic with such anomalously extreme pockets of ocean heat look set to cause further chaos heading into autumn based on this additional superimposed forcing. Truly, all bets continue to be off and sitting back and trying to grapple with the global tipping point that is clearly underway is required. This summer has been a stark red flag for what is to come. Sensationalism this genuinely isn't. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4904564

This is another variety of the many x+y=theories on this forum which has no founding other than a sense of something anecdotal and hoped for to happen again. Finally some fragile coherence has come to the expected synoptic pattern vs diagnostic wind-flow pattern with downstream ridging and Atlantic trough as far as the European sector is concerned - but there is so much extreme oceanic micro forcing around the globe (very much including the Atlantic) that is now testing medium range diagnostic analysis to the limit, let alone seasonal predictions. Seasonal wavelength changes and the increasing gradient differentials between the cooling at the pole and the lagged heat in the tropic with such anomalously extreme pockets of ocean heat look set to cause further chaos heading into autumn based on this additional superimposed forcing. Truly, all bets continue to be off and sitting back and trying to grapple with the global tipping point that is clearly underway is required. This summer has been a stark red flag for what is to come. Sensationalism this genuinely isn't.

Tendency in AAM is not the same thing as aggregate total AAM in the atmosphere at any given time Angular momentum tendency began falling quickly in early July from the total AAM peaks in June. Unexpectedly so. A much smaller and less extended drop in tendency had been anticipated. Very large -ve mountain torque mechanisms created the retrogressive movement that led to the amplified Atlantic ridge and downstream trough pattern of most of July. The net outcome of this was that total AAM readjusted to a lower base state during July than anticipated. But it was the direction of travel in tendency that instigated the initial pattern change from June Therefore it is whether tendency in the atmospheric circulation is rising or falling that helps decide the direction of travel in synoptic responses. In that sense how high (or low) total atmospheric angular momentum is at the time of a movement of AAM tendency is of lesser importance. Though again, every scenario is taken on its own merits. Much like tropical convection MJO forcing, too many over simplified x+y = equations arise with this particular type of diagnostic modelling. Not you personally obviously. Difficulty of understanding (which is understandable) but also in typical cases of a minority on this thread - antipathy, discrediting and scepticism are also among the range of usual reasons. There were many posts dedicated to this subject from a few members during July as to (just one) of the main reasons why expectations were not fulfilled (at least for the UK). It would help if some people (again not you personally) would read them to help the discussion move on a bit. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4901985

Tendency in AAM is not the same thing as aggregate total AAM in the atmosphere at any given time Angular momentum tendency began falling quickly in early July from the total AAM peaks in June. Unexpectedly so. A much smaller and less extended drop in tendency had been anticipated. Very large -ve mountain torque mechanisms created the retrogressive movement that led to the amplified Atlantic ridge and downstream trough pattern of most of July. The net outcome of this was that total AAM readjusted to a lower base state during July than anticipated. But it was the direction of travel in tendency that instigated the initial pattern change from June Therefore it is whether tendency in the atmospheric circulation is rising or falling that helps decide the direction of travel in synoptic responses. In that sense how high (or low) total atmospheric angular momentum is at the time of a movement of AAM tendency is of lesser importance. Though again, every scenario is taken on its own merits. Much like tropical convection MJO forcing, too many over simplified x+y = equations arise with this particular type of diagnostic modelling. Not you personally obviously. Difficulty of understanding (which is understandable) but also in typical cases of a minority on this thread - antipathy, discrediting and scepticism are also among the range of usual reasons. There were many posts dedicated to this subject from a few members during July as to (just one) of the main reasons why expectations were not fulfilled (at least for the UK). It would help if some people (again not you personally) would read them to help the discussion move on a bit.

I can understand & sympathise with how fed up many are in the UK with the unseasonable weather. But just as means to give a perspective that the grass is not always greener for what one might yearn for - here in Portugal it has been a very good and comfortable summer till now and was very grateful to be away from the conditions in the UK. However I was also even more grateful to be away from the intense heat further east in the Mediterranean. However that changed this weekend and the luck of the escape ran out. At the moment it is really stupid heat and simply not possible to go out at all during the bulk of the day. Say from about 10.30am to about 6.30 - 7pm in the evening. Have to put up with this to Wednesday when somewhat cooler conditions come by evening (to at least include my locale in Portugal) and there is no sign of such intense heat returning anytime soon as it gradually shifts subtly eastwards through the week to be focussed in the interior and southern parts of Spain (who could equally do without it). Thursday and Friday are back to about 34/35C IMBY with the Atlantic "air con" breeze kicking in to cool things down further by early evening. Night mins back to the high teens. That is closer to my idea of summer But right now, this is not fun at all and I am literally marking time and sitting tight till it is over. Living on a farm it is not good for the animals and that creates worry trying to keep them cool and hoping they are ok hiding in whatever extra shade they have been provided with. Two more days seems an absurdly long time with conditions like this. And I say that as a fan of classic summer weather. I admit to really yearning right now for a grey cool day with some rain. So, maybe in the UK it might help to know that hot sunny weather can also be far too much of a good thing in great excess.

A good summary Matt. The diagnostic GSDM plot profiles compartmentalise the wind-flow anomalies which helps to match the corresponding synoptic pattern. Its been an especially unstable profile - as the GWO plot shows with both -ve and +ve lunges in momentum as per the Phase 8/4/8 orbits. The fast +ve orbit of late and the fleeting nature of it speaks much about how the forcing relationship within the tropics & extra tropics is out of kilter and how no cohesive settling of the pattern at a UK latitude has been possible. Subtle changes in the strong jet profile across the Atlantic have steered the jet stream far enough away to cut-off the Atlantic "air con" influence to my part of SW Europe. So the luck that rode through most of the whole of July has run out. Winners and losers interchange more especially in a summer like this. The African heat dome has accordingly relocated influence to Portugal and parts of the Spanish interior. The latter of which also saw the intense heat during July. For my locale at least, two/three more days to endure of stupid heat before it starts to relax again. The Atlantic influences protect Western and Northern parts of Portugal and Northern Spain to some degree - but this "Saharan" type expansion c/o these increasing heat and dryness averages year on year is truly worrying. Weather is not the same as climate, but when the bar of average "weather" keeps rising to produce so many various ever escalating extremes in so many places across the hemisphere, then it is impossible to ignore the background trend. The impact of these, not too far away, on the environment & ecosystem of Southern Spain most particularly is very sobering for example. Yet there are still some who will keep saying it has always been hot in Southern Europe in summer and there is nothing to see here....... There is truth in all this. Convection convergence feedbacks too far west of the Pacific dateline, especially when there is additional high frequency or cyclone feedbacks scrambling the signal further across the IO and Indonesia will act to create a -ve frictional torque within the tropics (easterly inertia) which forges a retrograde pull on the circum-global sub tropical ridges, strengthening them at the same time. This means that within the Atlantic sector, the Azores sub tropical ridge is retracted and bolstered and helps steer and force downstream troughs to the UK. Eastward adjustment of tropical convergence in the Pacific towards and east of the dateline will reverse the frictional torque as -ve easterly inertia is wiped out in this ENSO region. Therefore westerly wind momentum transport has no resistance and the inflection point of converging wind-flows is removed west of the dateline. Hence a more +ve frictional torque signal drives a downstream rossby wavebreaking response and the retracted ridge is replaced by a trough and downstream ridge instead. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4901507

A good summary Matt. The diagnostic GSDM plot profiles compartmentalise the wind-flow anomalies which helps to match the corresponding synoptic pattern. Its been an especially unstable profile - as the GWO plot shows with both -ve and +ve lunges in momentum as per the Phase 8/4/8 orbits. The fast +ve orbit of late and the fleeting nature of it speaks much about how the forcing relationship within the tropics & extra tropics is out of kilter and how no cohesive settling of the pattern at a UK latitude has been possible. Subtle changes in the strong jet profile across the Atlantic have steered the jet stream far enough away to cut-off the Atlantic "air con" influence to my part of SW Europe. So the luck that rode through most of the whole of July has run out. Winners and losers interchange more especially in a summer like this. The African heat dome has accordingly relocated influence to Portugal and parts of the Spanish interior. The latter of which also saw the intense heat during July. For my locale at least, two/three more days to endure of stupid heat before it starts to relax again. The Atlantic influences protect Western and Northern parts of Portugal and Northern Spain to some degree - but this "Saharan" type expansion c/o these increasing heat and dryness averages year on year is truly worrying. Weather is not the same as climate, but when the bar of average "weather" keeps rising to produce so many various ever escalating extremes in so many places across the hemisphere, then it is impossible to ignore the background trend. The impact of these, not too far away, on the environment & ecosystem of Southern Spain most particularly is very sobering for example. Yet there are still some who will keep saying it has always been hot in Southern Europe in summer and there is nothing to see here....... There is truth in all this. Convection convergence feedbacks too far west of the Pacific dateline, especially when there is additional high frequency or cyclone feedbacks scrambling the signal further across the IO and Indonesia will act to create a -ve frictional torque within the tropics (easterly inertia) which forges a retrograde pull on the circum-global sub tropical ridges, strengthening them at the same time. This means that within the Atlantic sector, the Azores sub tropical ridge is retracted and bolstered and helps steer and force downstream troughs to the UK. Eastward adjustment of tropical convergence in the Pacific towards and east of the dateline will reverse the frictional torque as -ve easterly inertia is wiped out in this ENSO region. Therefore westerly wind momentum transport has no resistance and the inflection point of converging wind-flows is removed west of the dateline. Hence a more +ve frictional torque signal drives a downstream rossby wavebreaking response and the retracted ridge is replaced by a trough and downstream ridge instead.

Two very large inaccuracies and mistruths with this: Its like deja vu from winter in the UK when disenchantment sets in. First of all many various reasons have been given (in depth) as to how the summer pattern has played out contrary to various expectations. And equally at various times, there has been acceptance that expectations have not been met. Daily pessimism and grumbling about UK weather may have obscured this reality. And rather than point a finger - remember, beyond basic respect from one to another, no-one actually owes anyone anything on a voluntary platform... Secondly, it is a fact that scenarios do evolve and develop. The wave pattern responsible for the July pattern has evolved in the modelling, at least subtly, even if it has not changed the weather on the ground in the UK. The problem, especially for someone like me who is now commenting from another country in Europe, is that I have further increased detachment from emotional reactivity to (unemotional) computer models that had already been established in the UK before leaving. I can see though how such detachment might be difficult to deal with for you. Better to accept the departures from thinking as an opportunity to try and learn from them - than discredit and seek to blame the weather messengers, who are trying to do the learning. Better still, you could always give it a go yourself.... The truth is, at least speaking personally, my own home study ability is stretched more by this summer season that any previously. I genuinely think a tipping point has been coming for some time with plenty of evidence over recent years. I think that time has now come... @snowking summed things up well yesterday.

Your response illustrates my point. The broken clock analogy applies, anything but, to attempted analysis that is based on best information available at a given time. It might be information you don't understand, and the weather makes mugs of better people than me for sure, but I guess for your ilk it makes it much easier to toss into a file named garbage. You win a broken clock as a prize for endearing insight. To be referenced as vague is a large enough irony. Don't conflate personal lack of understanding with "vagueness" c/o apathy and cynicism related to perceived flaws in the science of weather analysis. Largely driven by parochial ignorance. This isn't fun and how to spend a weekend. Off to attend to the peahens,chickens, cats and the goats. Ciao e todos.

There is no clear sign still of this situation changing. Quite the reverse from late Spring and early Summer generally expressed expectations. Indeed thoughts expressed earlier in July have been consigned to history. Probably one of the most challenging seasons, in general, to decode - but then there are some answers as always to be found. What also is contributing to the feedback loop in the Atlantic/European sector is ridiculously warm (hot) waters in the NW Atlantic and off the Newfoundland coast which is superimposing the macro scale tropical>extra tropical feedback with the feedback ridging aligning this anomaly and amplifying the effects of deeper troughs running around the perimeter of the Atlantic ridge towards NW Europe within the defined stuck wave pattern. An unusual thermal gradient for summer is created along the polar front as this anomalous heat clashes with the colder air north of the jet stream path The feedback is self perpetuating - the longer the ridge pattern holds, the more the static pattern increasingly allows the regional SST's to increase. And so on and so forth. For UK & NW Europe, this feedback matters - because it is immediately downstream. From a Portuguese point of view, the unexpected broad scale summer pattern has actually done the country a favour with enough Atlantic wind-flow incidence based on the position of the Azores/Atlantic ridge to the west, and the passage of a few very weak trailing fronts from the N European troughs to allow an aircon effect through most of July. These fronts have produced barely any rain, away from NW Iberian coasts, but have been just about enough to keep the worst of the inferno upper air temperature profiles to the east. The predictions, in line with much of the expressed thinking heading into the summer, braced the country for the type of dangerously hot and damaging conditions seen across the Mediterranean to the east. So IMBY, (but with August still to come), there is a lot of gratitude so far in contrast to the feelings of many in the UK stuck under the N European trough. Just another, very different,perspective that shows that dangerous blazing heat is worse in many respect than the tiresome dirge of unseasonably wet & unsettled conditions which spoil summer activity, but in themselves are not harmful to people, animals, infrastructure & very much so the environment. No-one should doubt how superimposed warming is skewing the feedbacks and exaggerating and distorting naturally expected synoptic pattern responses. It does NOT debunk the diagnostic science that studies the natural feedbacks - but, as stated recently, it does reinforce the message that forecasting based on historical composites are increasingly prone to error and patterns, as they evolve, need to be taken on their own merits. Some of the very abnormal arctic, ocean and landmass heat anomalies around the globe are creating so many stark and intense micro scale feedbacks that the sum of all these is grossly distorting expected synoptic feedbacks on the larger scale It is actually very worrying. No-one should underestimate this. Ambivalent as I am and with no personal interest in cold weather outcomes for the UK in winter, this taking patterns on their merits approach should be adopted especially from this autumn, to save a lot of time and energy in trying to fit desired outcomes into composite frameworks which climate forcing is making more and more redundant as each year passes. This is all happening very fast. Whether it is to do with forecasting, or simply living from month to month, year to year, people who remain complacent and/or in denial need to wake up. If I may respectfully ask - why exactly? There is a big difference between defining the outcome of a month based on emotion/pessimism (or as per a minority of daily suspects, simply to childishly goad reaction and wind-up people) - and the people who are often the targets of reactions who take time out to try and offer some suggestions and then who are gloated at with pleasure when expectations are missed. Various posters have pointed this out, including the very good summary made by @Kirkcaldy Weather fairly recently. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4896443

There is no clear sign still of this situation changing. Quite the reverse from late Spring and early Summer generally expressed expectations. Indeed thoughts expressed earlier in July have been consigned to history. Probably one of the most challenging seasons, in general, to decode - but then there are some answers as always to be found. What also is contributing to the feedback loop in the Atlantic/European sector is ridiculously warm (hot) waters in the NW Atlantic and off the Newfoundland coast which is superimposing the macro scale tropical>extra tropical feedback with the feedback ridging aligning this anomaly and amplifying the effects of deeper troughs running around the perimeter of the Atlantic ridge towards NW Europe within the defined stuck wave pattern. An unusual thermal gradient for summer is created along the polar front as this anomalous heat clashes with the colder air north of the jet stream path The feedback is self perpetuating - the longer the ridge pattern holds, the more the static pattern increasingly allows the regional SST's to increase. And so on and so forth. For UK & NW Europe, this feedback matters - because it is immediately downstream. From a Portuguese point of view, the unexpected broad scale summer pattern has actually done the country a favour with enough Atlantic wind-flow incidence based on the position of the Azores/Atlantic ridge to the west, and the passage of a few very weak trailing fronts from the N European troughs to allow an aircon effect through most of July. These fronts have produced barely any rain, away from NW Iberian coasts, but have been just about enough to keep the worst of the inferno upper air temperature profiles to the east. The predictions, in line with much of the expressed thinking heading into the summer, braced the country for the type of dangerously hot and damaging conditions seen across the Mediterranean to the east. So IMBY, (but with August still to come), there is a lot of gratitude so far in contrast to the feelings of many in the UK stuck under the N European trough. Just another, very different,perspective that shows that dangerous blazing heat is worse in many respect than the tiresome dirge of unseasonably wet & unsettled conditions which spoil summer activity, but in themselves are not harmful to people, animals, infrastructure & very much so the environment. No-one should doubt how superimposed warming is skewing the feedbacks and exaggerating and distorting naturally expected synoptic pattern responses. It does NOT debunk the diagnostic science that studies the natural feedbacks - but, as stated recently, it does reinforce the message that forecasting based on historical composites are increasingly prone to error and patterns, as they evolve, need to be taken on their own merits. Some of the very abnormal arctic, ocean and landmass heat anomalies around the globe are creating so many stark and intense micro scale feedbacks that the sum of all these is grossly distorting expected synoptic feedbacks on the larger scale It is actually very worrying. No-one should underestimate this. Ambivalent as I am and with no personal interest in cold weather outcomes for the UK in winter, this taking patterns on their merits approach should be adopted especially from this autumn, to save a lot of time and energy in trying to fit desired outcomes into composite frameworks which climate forcing is making more and more redundant as each year passes. This is all happening very fast. Whether it is to do with forecasting, or simply living from month to month, year to year, people who remain complacent and/or in denial need to wake up. If I may respectfully ask - why exactly? There is a big difference between defining the outcome of a month based on emotion/pessimism (or as per a minority of daily suspects, simply to childishly goad reaction and wind-up people) - and the people who are often the targets of reactions who take time out to try and offer some suggestions and then who are gloated at with pleasure when expectations are missed. Various posters have pointed this out, including the very good summary made by @Kirkcaldy Weather fairly recently.

Its a good question. Velocity potential (VP) convection anomaly predictions have persisted with the idea of convergence shifting across the Central Pacific to return a more classic El Nino synoptic response. Much of discussion analysis has been focussed on this - quite reasonably so. Over recent weeks these predictions have backtracked a few times, putting back the shift in the low frequency signal. Its worth looking at a water profile across the tropics in this respect. This first image below is almost a week old, but very little has changed. The most intensely anomalous heat is focussed across Indonesia and relatively limited spread also across the Western Pacific. Strong trade winds persists at, and east of the dateline (shaded blue on Hovmollers plot in the third image). Convergence therefore mimics a more La Nina feedback pattern. Look where the main VP200 anomalies (shaded green) lie on the respective plot on the second image. The core is a long way further west of a typical El Nino convergence feedback & with suppression (shaded orange) at and east of the dateline. With so much heat in these areas well west of the dateline, it does call into question the vivacity of this El Nino, when repeated predictions of eastward progression of tropical convergence and associated westerly wind bursts is being delayed and watered down each time. The implication of that is the synoptic pattern response is bogged down with Nina feedbacks overshadowing the ocean base state El Nino transition. This type of oceanic > atmosphere feedback increases the likelihood of return to La Nina much sooner than has been widely anticipated and goes some way to further answering the longevity of the Nino disconnect as discussed already in much detail. In turn explaining the forcing from upstream which has been delaying synoptic upturn for N Europe at the same time as trapping heat across S Europe (Thankfully Portugal has had enough Atlantic influence and effective air con to avoid the worst of the July heat to date). The numerical models in response to these delays is to water down the expected split flow solutions across the Atlantic & Europe in extended modelling and retain the more retracted pattern which feeds downstream troughs across N Europe at the same time as the Azores/Atlantic ridge is withdrawn. This, rather than a ridge extending fully NE and then the split flow creating cut off lows behind it - which in turn create the ability for warm air (heat) advection northwards. Clearly, with these spatial wind-flow and VP200 anomalies in mind, it is worth exercising caution with forecasts and keep watching the discussed developments upstream. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4893247

Its a good question. Velocity potential (VP) convection anomaly predictions have persisted with the idea of convergence shifting across the Central Pacific to return a more classic El Nino synoptic response. Much of discussion analysis has been focussed on this - quite reasonably so. Over recent weeks these predictions have backtracked a few times, putting back the shift in the low frequency signal. Its worth looking at a water profile across the tropics in this respect. This first image below is almost a week old, but very little has changed. The most intensely anomalous heat is focussed across Indonesia and relatively limited spread also across the Western Pacific. Strong trade winds persists at, and east of the dateline (shaded blue on Hovmollers plot in the third image). Convergence therefore mimics a more La Nina feedback pattern. Look where the main VP200 anomalies (shaded green) lie on the respective plot on the second image. The core is a long way further west of a typical El Nino convergence feedback & with suppression (shaded orange) at and east of the dateline. With so much heat in these areas well west of the dateline, it does call into question the vivacity of this El Nino, when repeated predictions of eastward progression of tropical convergence and associated westerly wind bursts is being delayed and watered down each time. The implication of that is the synoptic pattern response is bogged down with Nina feedbacks overshadowing the ocean base state El Nino transition. This type of oceanic > atmosphere feedback increases the likelihood of return to La Nina much sooner than has been widely anticipated and goes some way to further answering the longevity of the Nino disconnect as discussed already in much detail. In turn explaining the forcing from upstream which has been delaying synoptic upturn for N Europe at the same time as trapping heat across S Europe (Thankfully Portugal has had enough Atlantic influence and effective air con to avoid the worst of the July heat to date). The numerical models in response to these delays is to water down the expected split flow solutions across the Atlantic & Europe in extended modelling and retain the more retracted pattern which feeds downstream troughs across N Europe at the same time as the Azores/Atlantic ridge is withdrawn. This, rather than a ridge extending fully NE and then the split flow creating cut off lows behind it - which in turn create the ability for warm air (heat) advection northwards. Clearly, with these spatial wind-flow and VP200 anomalies in mind, it is worth exercising caution with forecasts and keep watching the discussed developments upstream.

Its been said many many times that it is not as simple as taking the MJO in isolation to gauge weather patterns over a period of time. The MJO is just one part of the total global aggregate wind flow budget. Consideration of the extra tropics is required to gauge the full picture - as propagation of tropical convection propagates between the tropics>extra tropics and there is no linear progression as the two do not always interact equally. Late Spring & early summer did see a harmonious wind-flow signal between tropics & extra tropics with vast amounts of +AAM anomalies within the entire aggregate atmospheric circulation. The May surging peak in global +ve AAM lagged the feedbacks for a 4 to 6 week period. So the late Spring inertia provided the platform that led to the very anticyclonic wavebreaking pattern in June in N Europe. Since then, it is true that tropical convection went in to a lull period. This was anticipated - but what was not anticipated was the more profound effect than was expected that this had within the extra tropical circulation and the amount of -ve inertia c/o strong uptick in trade winds at, and east of the dateline in the Pacific that scrubbed out so much of the anomalously westerly (+ve) inertia from the early summer. The tropical convergence outcome well west of the dateline has been more reminiscent of a La Nina pattern - with a retrograde upstream mechanism in the Pacific leading to a retracted pattern downstream with a trough replacing the anticyclonic block across N Europe A slow process is now coming into view to start to reverse the mid summer disconnect and add back some of the westerly inertia lost from global windflow- but again it will be necessary to consider the extra tropical Global Wind Oscillation (GWO) response which depicts aggregate windflow in both tropics & extra tropics - and not the MJO, in isolation. In this respect, MJO composite,, do not always give a full picture b/c they risk assuming a linear extra tropical response according to the selected composite related to either a La Nina or El Nino forcing. Composite analysis can be erroneous b/c it assumes fixed given parameters within the tropics that do not always correspond to a fixed projected outcome in the extra tropics. The constant flux of the atmospheric circulation requires that each wind-flow exchange requires analysis according to its merits and not an x+y = assumption. It is also true that superimposed extra warming is skewing responses based on so many micro scale escalated anomalies creating enough "local" global extremes to strain the overall responses that Mother Nature put in place. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4892713

Its been said many many times that it is not as simple as taking the MJO in isolation to gauge weather patterns over a period of time. The MJO is just one part of the total global aggregate wind flow budget. Consideration of the extra tropics is required to gauge the full picture - as propagation of tropical convection propagates between the tropics>extra tropics and there is no linear progression as the two do not always interact equally. Late Spring & early summer did see a harmonious wind-flow signal between tropics & extra tropics with vast amounts of +AAM anomalies within the entire aggregate atmospheric circulation. The May surging peak in global +ve AAM lagged the feedbacks for a 4 to 6 week period. So the late Spring inertia provided the platform that led to the very anticyclonic wavebreaking pattern in June in N Europe. Since then, it is true that tropical convection went in to a lull period. This was anticipated - but what was not anticipated was the more profound effect than was expected that this had within the extra tropical circulation and the amount of -ve inertia c/o strong uptick in trade winds at, and east of the dateline in the Pacific that scrubbed out so much of the anomalously westerly (+ve) inertia from the early summer. The tropical convergence outcome well west of the dateline has been more reminiscent of a La Nina pattern - with a retrograde upstream mechanism in the Pacific leading to a retracted pattern downstream with a trough replacing the anticyclonic block across N Europe A slow process is now coming into view to start to reverse the mid summer disconnect and add back some of the westerly inertia lost from global windflow- but again it will be necessary to consider the extra tropical Global Wind Oscillation (GWO) response which depicts aggregate windflow in both tropics & extra tropics - and not the MJO, in isolation. In this respect, MJO composite,, do not always give a full picture b/c they risk assuming a linear extra tropical response according to the selected composite related to either a La Nina or El Nino forcing. Composite analysis can be erroneous b/c it assumes fixed given parameters within the tropics that do not always correspond to a fixed projected outcome in the extra tropics. The constant flux of the atmospheric circulation requires that each wind-flow exchange requires analysis according to its merits and not an x+y = assumption. It is also true that superimposed extra warming is skewing responses based on so many micro scale escalated anomalies creating enough "local" global extremes to strain the overall responses that Mother Nature put in place.

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. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4891808

A response to this is merited. The GSDM is not an aid to support weather biases & preferences or to try to fit its findings at any given time into a desired outcome. It is a diagnostic model completely devoid of human emotions. Therefore the same applies all year around in respect of neutral objectivity rather than hope-casting preference. Used properly, but more importantly (and this is the hardest part) used as accurately as possible it will give as useful guidance to any part of the NH (indeed in the SH if one lives in that part of the globe) as it comprises both a tropical & extra tropical gauge of global wind-flow which can assist with trying to anticipate downstream patterns based on evolution of forcing in the tropics which propagates into the extra tropics and influences jet stream patterns from upstream. Taking preference out of the occasion, the GSDM appeared to "work" in the later Spring & early Summer b/c it was much easier to read a very emphatic wind-flow signal that favoured downstream amplification. What was much harder to envisage was the lull downturn in the tropics which led to a disconnect much greater than most anticipated. The GSDM still "worked" but various forecasters and lesser mortals like me misread the depth of the new signal and therefore misread the diagnostic and prompted too premature an uptick in momentum.. It is clearly more complex than that, but for purposes of this reply it should suffice So that discrepancy is not any flaw in the GSDM, It is all part of challenge of using the diagnostic tool to try and anticipate the never ending flux of the atmosphere. The challenge is the reward, especially when things go wrong and further investigation is required - it should not become the finger of blame & myopic scepticism. Personal frustrations are very much linked to this Timing, based on intra-seasonal timescales of forcing in the tropics (MJO &CCKW related just for example) also meets challenges - based on the margins of periodicity (timeline recurrence of the phenomenon) - but again that is down to the analyst to evaluate as accurately as possible and not any culpability of the diagnostic product itself. Original post: https://community.netweather.tv/topic/99056-model-output-discussion-mid-summer-onwards/?do=findComment&comment=4891909

A response to this is merited. The GSDM is not an aid to support weather biases & preferences or to try to fit its findings at any given time into a desired outcome. It is a diagnostic model completely devoid of human emotions. Therefore the same applies all year around in respect of neutral objectivity rather than hope-casting preference. Used properly, but more importantly (and this is the hardest part) used as accurately as possible it will give as useful guidance to any part of the NH (indeed in the SH if one lives in that part of the globe) as it comprises both a tropical & extra tropical gauge of global wind-flow which can assist with trying to anticipate downstream patterns based on evolution of forcing in the tropics which propagates into the extra tropics and influences jet stream patterns from upstream. Taking preference out of the occasion, the GSDM appeared to "work" in the later Spring & early Summer b/c it was much easier to read a very emphatic wind-flow signal that favoured downstream amplification. What was much harder to envisage was the lull downturn in the tropics which led to a disconnect much greater than most anticipated. The GSDM still "worked" but various forecasters and lesser mortals like me misread the depth of the new signal and therefore misread the diagnostic and prompted too premature an uptick in momentum.. It is clearly more complex than that, but for purposes of this reply it should suffice So that discrepancy is not any flaw in the GSDM, It is all part of challenge of using the diagnostic tool to try and anticipate the never ending flux of the atmosphere. The challenge is the reward, especially when things go wrong and further investigation is required - it should not become the finger of blame & myopic scepticism. Personal frustrations are very much linked to this Timing, based on intra-seasonal timescales of forcing in the tropics (MJO &CCKW related just for example) also meets challenges - based on the margins of periodicity (timeline recurrence of the phenomenon) - but again that is down to the analyst to evaluate as accurately as possible and not any culpability of the diagnostic product itself.

I have quickly seen all I needed to see with this new ? symbol. That is not intended in any smug way. Seeking change is a good thing - but superficial emoticon change of this kind appeals only to those who seek to divide, show no appetite to learn themselves & yet are first to criticise & discredit. And also will be, and indeed are, the first to react when the truth of this is pointed out. It might be intended well, but it panders to the wrong people. Abuse is the outcome.