Tamara

August 23, 2023

2 hours ago, MattH said:

All eyes on the Pacific in approx a week's time and then a close eye on FT and MT tendencies within the opening 7 to 10 days of September and then potential changes towards mid-month, as a rough guide.

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.

August 22, 2023

16 hours ago, MATTWOLVES 3 said:

By the way did Tams mention a Mountain Torque event by any chance....as I've not heard it mentioned much on here just lately

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

August 18, 2023

5 hours ago, Addicks Fan 1981 said:

it was @TamaraI think suggested we look at hovmoller charts in past model threads.

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

August 18, 2023

5 hours ago, Addicks Fan 1981 said:

it was @TamaraI think suggested we look at hovmoller charts in past model threads.

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.

August 16, 2023

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

August 16, 2023

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.

August 12, 2023

11 hours ago, CreweCold said:

That’s ok.

Hopefully we’ll see some autumn as autumn commences. Warm Septembers aren’t good in terms of correlation to cold winters. So a trough returning to end August will set us up well as we enter September.

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

August 12, 2023

11 hours ago, CreweCold said:

That’s ok.

Hopefully we’ll see some autumn as autumn commences. Warm Septembers aren’t good in terms of correlation to cold winters. So a trough returning to end August will set us up well as we enter September.

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.

August 7, 2023

1 hour ago, Uncertainty said:

Indeed, rising AAM to high levels in early July did little to shake out the U.K. trough.

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

August 7, 2023

1 hour ago, Uncertainty said:

Indeed, rising AAM to high levels in early July did little to shake out the U.K. trough.

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.

August 7, 2023

1 hour ago, In Absence of True Seasons said:

Well, the updates in the model thread from this morning and yesterday evening are enough to make even the most zen of Monks throw a glass against the wall. My thoughts...

Am I shocked that the 'plume' of warmth/heat has been massively downgraded? No.

Did I expect this would happen, but refrain from mentioning it because I'd just be dismissed as having a "crystal ball"? Yes.

Has this happened quite literally every single other time since April when a warm/sunny spell has been predicted (outside of the June spell obviously), so it stands to reason from law of averages that it'll also happen this time again? Also yes.

Are we the only area in Europe (outside of Iceland and the Faroe Islands lol) where this cooler, wetter and cloudier than average weather has persisted for 5/6 weeks, and is STILL set to dominate August outside of the warm 'blip' this week? Again, obviously, it's yes.

Considering this looks to be the warmest spell on the horizon for the next 2 weeks or so (which is now looking to be just 2/3 days of slightly above average temps for my area anyway lol), it's with sadness that I announce what I felt in my heart was the case since weeks back...summer 2023, effectively, is over. At least, from the perspective of any genuine heat and/or prolonged above-average, sunny weather. Well, if we are honest with ourselves, it never really truly took off to begin with unfortunately - because the summer season for this year started and finished in June!

Indeed, we may get some warm and sunny settled spells in September, but it is simply not the same as having such spells in July or early to mid August. It's early Autumn by then, and is notably different in feeling, even if its 20c+ weather.

This is - as grim as it sounds - the reality of living in these isles and being someone who enjoys either A) proper seasonality, and/or B) warm or hot sunny weather. Many years, we get very little of either of these things. Likewise for those of us who enjoy proper wintry and snowy weather. Ultimately, the only real winners weather-wise in this country are those whose favourite conditions are 10-16c and mostly overcast, as that's what we have for 9/10 months of the year...

It's a real, real shame, because when we get years like 2022, or 2018, that bring an actual summer season, we get a brief taste/glimpse into what it'd be like to live in a country/climate where such weather is the norm - or even, a guarantee - from May to Sept, and good god it's a complete game-changer from a perspective of lifestyle/activities, wellbeing and productivity! But then, after experiencing summers such as these, we're then left feeling short-changed and disappointed (or in cases like mine, genuinely less physically and mentally well), when we get years like this one (or 2012). It's a bit like getting to try a bite of the finest fillet steak, before promptly being shoved back to the other table to chew on rubbery, overcooked rump - if the rump was your only point of comparison, you'd eat it without complaint, but once your eyes are opened to something far, far better, it's difficult to then enjoy something that is unequivocally sub-par.

What's the take-aways here for us warmth/heat and sun-chasers?

Take holidays when / if you can - as this July and August has shown irrefutably, holidaying in the UK is simply a gamble, and an expensive one at that, in regards to any settled or warm weather. I shudder at the thought of how many thousands of £ have been wasted by families who had booked expensive coastal holidays over the last 5/6 weeks off the back of the actual summer we had last year.

Take vitamin D tablets - Whilst it's not equivalent to spending some time in the fresh air and the sunshine, this definitely helps my mood and overall mental state, and they're a default supplement for me from the months of Oct to March, and during summers like this one they're also very worthwhile to take.

Utilise the extra time indoors to engage in hobbies/past-times that you otherwise wouldn't during summer - so, for me, this is painting/drawing, gaming, and guitar.

Resign to the reality that our climate is a flip-flopping, capricious mistress and one year has zero bearing on the next in terms of how the season will play out. So, basically, don't have any change in expectations as a result of years like 2022, and remain a level of "detached amusement" to whatever 'summer' arrives on this rock. Alot of people in the other threads make comments like "Well, we're paying this year for our boiling hot summer last year". Because quite obviously, that's not how any of this works - the 40c that was reached at Heathrow last year has nothing to do with the dross that has transpired this year. We may as well have been in two alternate dimensions for how different these two summers have been. It just is what it is - our climate brings very random weather patterns/conditions, and this has always been the case, and I suspect it will continue to be the case for as long as we can see. When hot summers like last year occur, there's all sorts of ideas that emerge from the media and their pundits, such as London transitioning towards a climate akin to Barcelona's within the next 10-15 years. As with most things - best to 'believe it when you see it'....

Wild card advice - smash something / chop some wood / unleash a flurry of punches against a bag or pillow / consume several pints of Guinness in quick succession

Happy Monday folks, and onwards and upwards to a warmer (and hopefully sunnier) blip this week, and then finger's crossed for an Indian Summer in September...

In the meantime, I shall be day-dreaming of living in a land where true seasons were not absent

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.

August 6, 2023

7 hours ago, MattH said:

Morning.

Just a quick addition to recent posts, but with the overall trend in AAM yet again on a downward path, it is, perhaps, no surprise that any sort of build of heights over W Europe continues to be blown away looking ahead and we end up with a more cyclonic pattern soon returning.

We can see from the GWO plot that we are heading back towards phase 8 and, no doubt dropping down into phase 1, all indicators of a falling AAM regime. The tendency plot highlights this well, with a pronounced change in recent days. The actual AAM profile is quite interesting with a 4-way split in terms of the expected +ve W'ly anomalies through the tropics (linked to the recent WWB/MJO activity), weak E'ly anomalies circa 40N, W'lies again near 50N and a very weak E'ly anom at circa 60N and above. Once again the story of the summer can be well told by the GSDM pattern and evolution since late May onwards.

In terms of model data looking ahead, we can see the downward trend in the expected AAM pattern through the rest of Aug on the below...

Obviously, there is some evidence for another rise into September, but it's probably not even worth bothering about that too much at the moment, but what are you betting we end up with summer synoptics, through some part of September, that many wanted in the previous 6 to 8 weeks. Equally, after the way July and, most likely, August will pan out, a fine week or two of September weather wouldn't go a miss!

As I mentioned a week or two back even I have been surprised by how 'locked in' the cyclonic pattern has been since early July, even though the initial trend towards a more cyclonic period into July was most certainly expected, once the huge WWB event through May and into June eased away, etc. I think it was Tamara who highlighted well also how the unknowns, linked to AGW and all the mesoscale and macro-scale extremes around the planet may well be providing and producing 'curve balls' that cannot be foreseen and can tip the balance away from what is usually/most likely expected.

In terms of the rest of August then I think the best one can hope for is a repeat of the pattern that plays out this week, with a transient S or SW'ly bringing some warmth and humidity. Otherwise, IMO, the writing is on the wall now for the rest of meteorological summer and I can't see much evidence if anything, that will mean a solid week or more of anticyclonic, late summer weather will arrive before the end of Aug, and this summer will end up going down as yet another one of those where the best of the weather of the year was through May and June and then the 'wheels came off' again as has happened a handful of times now over the last 10 to 20 years.

Regards, Matt.

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.......

2 hours ago, summer blizzard said:

For longer term prospects i have also circled two areas to try loosely highlight what has happened (forcing mainly in the west pacific) vs where we want it (forcing over/east of the date). While it's not a hard and fast rule because the MJO is not static or the only factor, peristent convection in the west Pacific (though worse if strong over the Indian Ocean) tends to produce downstream lows for the UK in my experience (no idea why and wavelengths do change but this is very much an Autumn/Winter/late summer observation) regardless of whether it pushes AAM (hence potential plumy shots but probably not high pressure over the UK). Stronger convective anomolies in the central and east pacific tend to correlate better to mid-lattitude pressure building over the UK. I wish I had the above chart for 2018 to highlight because i remember that thinking being quite demonstrative.

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

August 6, 2023

7 hours ago, MattH said:

Morning.

Just a quick addition to recent posts, but with the overall trend in AAM yet again on a downward path, it is, perhaps, no surprise that any sort of build of heights over W Europe continues to be blown away looking ahead and we end up with a more cyclonic pattern soon returning.

We can see from the GWO plot that we are heading back towards phase 8 and, no doubt dropping down into phase 1, all indicators of a falling AAM regime. The tendency plot highlights this well, with a pronounced change in recent days. The actual AAM profile is quite interesting with a 4-way split in terms of the expected +ve W'ly anomalies through the tropics (linked to the recent WWB/MJO activity), weak E'ly anomalies circa 40N, W'lies again near 50N and a very weak E'ly anom at circa 60N and above. Once again the story of the summer can be well told by the GSDM pattern and evolution since late May onwards.

In terms of model data looking ahead, we can see the downward trend in the expected AAM pattern through the rest of Aug on the below...

Obviously, there is some evidence for another rise into September, but it's probably not even worth bothering about that too much at the moment, but what are you betting we end up with summer synoptics, through some part of September, that many wanted in the previous 6 to 8 weeks. Equally, after the way July and, most likely, August will pan out, a fine week or two of September weather wouldn't go a miss!

As I mentioned a week or two back even I have been surprised by how 'locked in' the cyclonic pattern has been since early July, even though the initial trend towards a more cyclonic period into July was most certainly expected, once the huge WWB event through May and into June eased away, etc. I think it was Tamara who highlighted well also how the unknowns, linked to AGW and all the mesoscale and macro-scale extremes around the planet may well be providing and producing 'curve balls' that cannot be foreseen and can tip the balance away from what is usually/most likely expected.

In terms of the rest of August then I think the best one can hope for is a repeat of the pattern that plays out this week, with a transient S or SW'ly bringing some warmth and humidity. Otherwise, IMO, the writing is on the wall now for the rest of meteorological summer and I can't see much evidence if anything, that will mean a solid week or more of anticyclonic, late summer weather will arrive before the end of Aug, and this summer will end up going down as yet another one of those where the best of the weather of the year was through May and June and then the 'wheels came off' again as has happened a handful of times now over the last 10 to 20 years.

Regards, Matt.

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.......

2 hours ago, summer blizzard said:

For longer term prospects i have also circled two areas to try loosely highlight what has happened (forcing mainly in the west pacific) vs where we want it (forcing over/east of the date). While it's not a hard and fast rule because the MJO is not static or the only factor, peristent convection in the west Pacific (though worse if strong over the Indian Ocean) tends to produce downstream lows for the UK in my experience (no idea why and wavelengths do change but this is very much an Autumn/Winter/late summer observation) regardless of whether it pushes AAM (hence potential plumy shots but probably not high pressure over the UK). Stronger convective anomolies in the central and east pacific tend to correlate better to mid-lattitude pressure building over the UK. I wish I had the above chart for 2018 to highlight because i remember that thinking being quite demonstrative.

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.

July 29, 2023

57 minutes ago, Alderc 2.0 said:

You make lots of good points here that I mostly agree with however one thing that irks me, especially with the pro forecasters is when it’s got wrong no one ever comes out and says ‘yup effed that up and got it wrong by a mile’ no one ever seems to be able to admit they are wrong at the time and instead drag it usually by using an evolving scenario to water things down and turn direction.

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.

July 29, 2023

13 hours ago, Nick2373 said:

Why you ask? To be honest and quite frank your post have been if anything vague and close to a stopped clock is right twice a day. I’ve noticed that you post with all the big Synoptics and quite a lot of this does that and if this happens then we will see this. When in fact if I recall you looked at the long range and said the opposite to a warm and settled second half of July. The fact is being a professional an amateur or a pro, the weather past seven days is like the lottery. If you can get it right you are quids in. Please feel free to review all my posts regarding the GEFS all the way through July and I think it was pretty much smack on.

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.

July 28, 2023

On 22/07/2023 at 12:22, Tamara said:

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.

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.

1 hour ago, Nick2373 said:

Credit to anyone who called July to be this big hum dinger

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

July 28, 2023