Tamara

February 10

This is my last response on this subject as your latest resply tells me you didn't read the (albeit very brief) explanation about wind-flow, torque, angular momentum (and what it means in parlance of weather patterns)

. It should be clear from that, that the jetstream is influenced by the basis science of what causes acceleration of momentum, or conversely, deceleration of momentum in the atmosphere and a background to the waxing and waning & movement of cyclones and anticyclones across the globe. It might be technical in its GSDM data sets with a lot of acronym speak, but it is actually in truth a basic starting point for getting a structure of the global patterns. If it is not understood what influences basic jet stream patterns,and also the cyclical nature of teleconnection phenomena (which is another part of the equation) then how can any of the other drivers be placed in the jigsaw?.

I am more and more convinced that if this winter had produced more widespread and sustained snowfall this thread would never have been triggered. I resent being implied as some kind of cherry picking soothsayer and equally that there is some arrogance about being right and not admitting errors.

Why is it my responsibility to be held account for the lack of desired winter weather? I have produced continuity analysis throughout my more recent years on this site, for the very purpose of being transparent. In an effort to stand up for myself, I am going to say that these continuity analyses have left little room for conspicuous error and so the latest charge of yours of not admitting any error is deeply untrue, unfair & unreasonable and I am not going to stand for it. And yes this is defensive, and yet you winder why!...

I have not been paid to contribute anything on this site, and while we all (including you actually!) make mistakes, none of us, including me (though sometimes I wonder!) have any particular obligation to be apologist to anyone.

It just so happens that I have been pro-wintry weather patterns for this particular season. The truth, which I am not going to be pressured into conceding on, is that very fine lines have driven the outcomes of this winter. It *should* have been, or it should be, a spectacle of interest and discussion as to outcomes and not a scapegoat seeking exercise for those, like you, who want to vent their frustrations onto other people.

As far as I am concerned the present evolution of the pattern between troposphere and stratosphere are playing out accordingly to expectations. Feel free to go pick out the recent summaries and dismantle them to pieces if you wish. Tropospheric +EAMT pathway in tandem with eastward propagating tropical convection triggering rossby wave perturbing of the stratosphere ( upcoming) and amplified state mid latitudes. Now, what that means in respect of cold air advection to mid latitudes, and where, remains uncertain and there are complex and somewhat countervailing aspects of fluxing between the stratosphere & troposphere- but it does NOT debunk the GSDM mechanisms which have played a part, already, in creating the evolution of the pattern underway.

February 10

Nick F

The availability of the data has been already answered in most part with the references to Ed Berry etc & his rights to his work. He retired and took those rights with him. Hence NOAA no longer published them at his request. NOAA did not stop publishing the data due to some lack of credibility as you appear to want to imply.

Many have been on this site, or referenced it long enough, to know that the GSDM has been sourced for analysis since at least 2007/08. Glacier Point pioneered it for Net Wx with much success in its use. So much so that it led to his further employment opportunities with Centurea weather, where he was appointed a head forecaster using the GSDM as the forefront of forecasting.

The names (implied) under criticism in this thread are just some who have aspired to try and get their heads around the complexities of the science. Difficulty in understanding does not equate to lack of credibility or simply tossing under File 101 as gobbledy-gook.. Quite modest, very ordinary amateur enthusiasts have taken the challenge, very much including me. so not really any excuse for anyone thinking somehow they are treated as also rans by being left out from the GSDM data sets. If the will and enthusiasm is there, then it is open to be studied.

The fact there is now a mix of both pro-Mets and amateurs across UK, mainland Europe and US who engage the GSDM methodology is testament to its credibility. I can see, therefore, why a pro-Met like Matt H might feel a little peeved as he made the effort to engage the GSDM diagnostic and include it in his professional analysis.

As for the METO, they have actually made enquiries about the GSDM on a private basis to some Net Wx and also US based forum members and there has been a background inspection of the diagnostic which includes recognition of angular momentum processes in the role of inducing jet stream pattern changes. I know this for a fact - but cannot be expected to answer to their actual decisions on whether or not they would be inclined to engage the methodology formally & officially but then again, it is the copyright of a late NOAA official and have no idea of the protocols etc involved in this.

Whichever way, its a bit disappointing to say the least to be trying all these rather confected avenues as means to discredit GSDM analysis as some kind of over hyped mystic meg thesis.

Especially bearing in mind what seems to have triggered this particular pique and GSDM bashing is some unbridled dissatisfaction with a UK winter! You yourself have employed some of the related teleconnection aspects in your (well laid out) forum seasonal forecasts. So with respect, it seems to be rather a contradictory position to take to your own efforts.

As for papers on GSDM there is a wealth of them. Including references to them on this site. There has been at least one dedicated thread in recent years to compiling a library of information on this very site. It took me a few years from about 2014 when I decided to take a big interest in this diagnostic to get my head around quite a bit of it. But just reading the in depth discussions between 2008/9 and about the time I started to try to get involved with learning about it, it was surprising how rewarding it was when some understanding started to click into place. Like chionomaniac and the strat threads also in the late 2000's, other have got inspired in this way.

February 10

I echo the words of @MattH And no, there is nothing unreasonable in he what said at all.

I have lost count of the number of times that I have tried to implore that the MJO is only one part of the total components that make up the "global wind-flow budget". This sounds a fancy term no doubt to the naysayers piling into threads like this in a queue to use it as a scapegoat for their snow being stolen, but if the atmospheric circulation is considered as the vacuum that it is, then it is not difficult to envisage that to maintain its parity, wind-flow that decelerates in one part, has to be compensated in another.

And vice versa when acceleration occurs in one part, there has to be equal compensation in another to maintain parity.

Angular momentum refers to the turning force (torque) exhibited where convergence, or divergence meet as inflection points to create that turning force on the jet stream. When decelerating wind-flow exceeds +ve momentum, then there is a greater requirement for more and more flow to be sucked back into the void that is left. This is represented by a -ve torque mechanism.

The converse again holds true to produce a +ve torque mechanism

The MJO represents wind-flow & momentum changes in the tropics. As part of Mother Nature's natural vacuum, it is necessary to consider the rest of the atmospheric circulation system in the extra tropics and top layers when catalysts for change of wind-flow begins in the tropics c/o MJO related forcing. In winter this means greater focus on not just interactions between the tropics and extra tropics in respect of +ve and -ve wind-flow interactions, but how both the troposphere itself as a whole further interacts with those "top layers".

Namely the stratosphere.

This is undoubtably the hardest task of all. And anyone who tries to relay context of the GSDM in respect of ultimate stratospheric evolutions and the subsequent tropospheric impacts is going to struggle and make errors. But that doesn't make the diagnostic wrong. It is simply the immense difficulty in making judgements set against complex and sometimes countervailing aspects.

There is so, so much more to this subject of the "global wind-flow budget". But it is the scientific essence of the Global Synoptic Diagnostic Model (or GSDM). I guess the title name itself makes it sound like it is the home for an elite echo chamber - but it is simply a title given by the late NOAA official Ed Berry in conjunction with others like David Gold. Who now has taken over fully its operation with others.

As @Met4Castsays, these are not untouchable gurus - and those of us who have been given access to the GSDM data plots are not a privileged elite, but people who have a genuine fascination & equally recognition of the insight into the atmospheric system that dictates wind-flow changes (aka the jet stream paths and strengths) and how convergence & divergence of wind-flows (torque mechanisms) change angular momentum tendency and in turn carve out the global synoptic patterns. Not just for UK postcodes.

Anyone else can choose to do this is they genuinely wish, by asking permission to the plots. The cautious issuing of permission rights over the years has been the late Ed Berry's wish for his pioneering work to be protected, as it developed more and more. In the same way as study of the stratosphere has come on leaps and bounds over the past couple of decades, this tropospheric diagnostic has slowly (more slowly) come forward as well. But somehow has contrived to be misrepresented as some kind of cultist elite movement. That is a big pity. Meteorology as a study as a whole loses out.

Other than incomplete over focus on the MJO in isolation of the rest of the wind-flow budget, the biggest factor for failure of messaging & understanding the value of these diagnostics is the emotional attachment to one desired synoptic outcome. Its one thing using an MJO composite in isolation (which increases likely error rate of probabilistic outcome anyway) but when these are also attempted to be fitted to bias outcomes as part of a bias confirmation process, then this further ups the error rate and ultimate disappointment when the bias outcome proves AWOL in reality.

The consequence? "The workman blames his tools"

To be blunt if these "workmen" are going to do this, then it is quite reasonable that anyone who tries to genuinely understand the purpose of the diagnostic as an objective, neutral process to ascertain ALL probabilities (as one does with ensemble & ensemble cluster groupings as per @Mike Pooleetc) to express resentment at the discrediting of the methodology. The frank answer is to either express a desire to hook up to the data and try to study the diagnostic objectively, or not bother at all . It is possible of course to continue to rely on NWP to look for outcomes. But as with the GSDM, continue to be disillusioned when persistent attempts to skew model data information or expectations to a bias outcome founders more often than verifies.

Neither using NWP and/or GSDM are wrong, and both of course are wholly valid. But the GSDM is meant to compliment NWP as a diagnostic insight into how synoptic patterns might evolve over time . Not some magic silver bullet to give faux insight into how it might increase the chance of snow in a given post code.

The GSDM is a diagnostic process not just for analysing winter patterns, but for all year round. The atmospheric circulation doesn't stand still from around March to October/November. So viewing tropical convection patterns is not a toy to play with snow-making for a few months and putting away in a cupboard till the next time - it is one component, just one component, of aggregate global wind-flow which is in constant flux 24/7, 365 days a year.

We would all not be here if it wasn't...

It is always quite possible to give an overview of the GSDM as an update to the present synoptic outcomes. However, as emphasised, this is only possible within a neutral framework as discussed in this post. That neutral framework would not justify its effort & existence as no-one would show interest because it would not be geared towards a favoured outcome. That is, if it was being used for the trur purpose it is geared towards & intended.

Sensible to leave it to one side based on the time it takes to put together analysis of the data. I can only say reasons have been given for why the disillusion itself is to blame and the "workmen" have to look at their own responsibility in inviting their own disillusion.

Melhores cumprimentos.

February 8

Met4Cast

Based on a likely spontaneous tropospheric response to what looks like a very robust SSW reversal of -ve zonal winds upcoming, the timing of tropospheric switch to a falling angular momentum regime implies that returning polar jet energy faces a roadblock across higher latitudes and result in actually perpetuating blocking effects across the NH.

I say this from a purely diagnostic viewpoint of a macro scale synoptic response & objectively as to how such a blocked regime may play out - without regard to surface weather responses at any given geographical location.

So protracted +AAM transport c/o +EAMT and tropical convection rossby wave driving has been incipient in initiating stratospheric diminution, and it could be that falling momentum heading into late winter & early Spring wavelengths augments -ve AO/NAO synoptic responses.

The same was said in January of course & the nature of the briefest of reversals underwent a reflective u-turn which allowed the polar jet to return unencumbered as angular momentum fell back The circumstances this time are quite different & the sheer scale of the stratospheric diminution heading towards the start of Spring puts at least a preliminary question mark over the return of the vortex as a final warming event.

In turn it suggests a relatively lengthy period of fractured jet flow betwixt & between blocking structures

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5034002

February 8

Met4Cast

Based on a likely spontaneous tropospheric response to what looks like a very robust SSW reversal of -ve zonal winds upcoming, the timing of tropospheric switch to a falling angular momentum regime implies that returning polar jet energy faces a roadblock across higher latitudes and result in actually perpetuating blocking effects across the NH.

I say this from a purely diagnostic viewpoint of a macro scale synoptic response & objectively as to how such a blocked regime may play out - without regard to surface weather responses at any given geographical location.

So protracted +AAM transport c/o +EAMT and tropical convection rossby wave driving has been incipient in initiating stratospheric diminution, and it could be that falling momentum heading into late winter & early Spring wavelengths augments -ve AO/NAO synoptic responses.

The same was said in January of course & the nature of the briefest of reversals underwent a reflective u-turn which allowed the polar jet to return unencumbered as angular momentum fell back The circumstances this time are quite different & the sheer scale of the stratospheric diminution heading towards the start of Spring puts at least a preliminary question mark over the return of the vortex as a final warming event.

In turn it suggests a relatively lengthy period of fractured jet flow betwixt & between blocking structures

January 26

1 hour ago, Catacol said:

"Good agreement exists in the dynamical models looking ahead, which initially favor a high amplitude MJO signal over the Western Pacific that weakens and slows after the week-1 period."

- because, weakening or not, a high amplitude west pacific signal that stalls is exactly what we would want to sustain this wave driving, with the potential to render the strong SPV less relevant than it might be. MJO plots, as ever a bit unreliable, are illustrated here and are lining up favourably:

I posted the VP200 anomalies earlier These will have resolution to identify tropical convection convergence much better than the RMM plots which lose reliability more than 4 to 5 days ahead. This winter has already proved this fallibility based on the previous undercooked RMM forecasts of wave orbit (set against a Nino standing wave to engage convergence in the Pacific at and beyond the dateline)

Based on the GSDM analysis - gravity wave amplitude> significant +EAMT> engagement of a robust upstream jet - all are hand in hand with a Phase.6,7,8 progression.

Those of you looking for the outcome you desire in UK/NW Europe would appreciate a slow but complete progression of the tropical wave through the whole of the Pacific - not withstanding the longevity of the poleward extra tropical momentum transport in respect of how it impacts the polar field.

I think a comparison analysis to follow with that of the events of Feb 2018 are valid. Not saying at all that the outcome and more especially the surface conditions will be precisely the same - but because there are a lot of tropospheric forcing similarities with that time.

Following the ongoing marvellous weather down here in PT, the return of the STJ would be very much welcomed by folk here who are eager for rain ahead of the heat and dryness of summer to come.

@Dennis Comments do not apply to your proactive posts in any way

January 26

Grateful to be immune to mood swings over the (emotionless) depictions of computer models. Enjoyment and great interest is derived from seeing how the diagnostic processes related to the atmospheric circulation play out in real time. Admittedly lucky for sure, related to where I live, to be fully indulged by a remarkable (record breaking) spell of weather down here in Portugal, but that doesn't detract from being immersed in February outcomes, whatever they may be, and are two quite separate and different things.

What is unfolding at the moment is a huge drive of planetary rossby waves. Amplitude intra-seasonal tropical convection (propagating across the tropics and to head right through the Pacific), which the velocity potential anomalies identify much better than the RMM plots.....

.....which has already triggered precursor gravity waves (explained the other day) and primed a very substantial +ve EAMT event to in turn imply a reconfiguring of the zonal wind anomalies within the stratosphere heading through February.

That much can be said with reasonable confidence. And to be blunt, it is all that should matter at the moment based on the timescales involved. My guess is that these tropospheric drivers are vigorous enough to overcome the strength of the SPV and, as a minimum, result in a de-coupling, if not major SSW (quite conceivable). But again, that is subject to watching the evolution over the timescales involved

A whole process measured over a few weeks at a time. Staring at a computer screen every 3 to 6 hours 24/7 is not going to provide the instant gratification that this thread persistently seeks. It is a pity b/c there is so much going on right now both in respect of current weather patterns and, looking ahead, what is being programmed within the atmospheric circulation itself.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024662

January 26

Grateful to be immune to mood swings over the (emotionless) depictions of computer models. Enjoyment and great interest is derived from seeing how the diagnostic processes related to the atmospheric circulation play out in real time. Admittedly lucky for sure, related to where I live, to be fully indulged by a remarkable (record breaking) spell of weather down here in Portugal, but that doesn't detract from being immersed in February outcomes, whatever they may be, and are two quite separate and different things.

What is unfolding at the moment is a huge drive of planetary rossby waves. Amplitude intra-seasonal tropical convection (propagating across the tropics and to head right through the Pacific), which the velocity potential anomalies identify much better than the RMM plots.....

.....which has already triggered precursor gravity waves (explained the other day) and primed a very substantial +ve EAMT event to in turn imply a reconfiguring of the zonal wind anomalies within the stratosphere heading through February.

That much can be said with reasonable confidence. And to be blunt, it is all that should matter at the moment based on the timescales involved. My guess is that these tropospheric drivers are vigorous enough to overcome the strength of the SPV and, as a minimum, result in a de-coupling, if not major SSW (quite conceivable). But again, that is subject to watching the evolution over the timescales involved

A whole process measured over a few weeks at a time. Staring at a computer screen every 3 to 6 hours 24/7 is not going to provide the instant gratification that this thread persistently seeks. It is a pity b/c there is so much going on right now both in respect of current weather patterns and, looking ahead, what is being programmed within the atmospheric circulation itself.

January 24

Another way of looking at the potential perturbing effects of rossby wave transport at high levels of the atmosphere is to look at this gravity wave drag plot.

In simple terms this refers to the strength of upward propagating waves that are created through torque deflection of wind-flows against very tall mountain ranges (e.g Himalayas and Rockies) and indeed wind shear c/o tropical convection (whose inflection point(s) of convergence zone(s) creates the eddies which propagate into the extra tropics in the first place)

Gravity waves at high amplitude induce high turbulence proportionate to the ever higher levels of the atmosphere they propagate into. The trend on the latest GSDM GWD plot shows the torque friction effects occurring at the latitudes of the East Asian mountain ranges.

There is quite the whiplash effect of global wind-flow in progress here. Recent deeply inverted reflective fluxing spilling from the stratosphere into the troposphere - now being sharply reversed by equally very strong +ve gravity wave propagation into the stratosphere. Strongly +ve AO to potentially robust -ve AO? Based on the lag time of the +EAMT.

In that respect, the poleward amplification mechanism has already undergone starters orders and is embedding within the global circulation - and this needs to be taken into account when pondering the eventualities of the MJO progression through the Pacific.

Yet again to say, the MJO, might be a catalyst for future wind-flow changes set in motion within the tropics - but in isolation it is not the be all and end all.

@RainAllNight This post may help answer your question in another way

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023753

January 24

Another way of looking at the potential perturbing effects of rossby wave transport at high levels of the atmosphere is to look at this gravity wave drag plot.

In simple terms this refers to the strength of upward propagating waves that are created through torque deflection of wind-flows against very tall mountain ranges (e.g Himalayas and Rockies) and indeed wind shear c/o tropical convection (whose inflection point(s) of convergence zone(s) creates the eddies which propagate into the extra tropics in the first place)

Gravity waves at high amplitude induce high turbulence proportionate to the ever higher levels of the atmosphere they propagate into. The trend on the latest GSDM GWD plot shows the torque friction effects occurring at the latitudes of the East Asian mountain ranges.

There is quite the whiplash effect of global wind-flow in progress here. Recent deeply inverted reflective fluxing spilling from the stratosphere into the troposphere - now being sharply reversed by equally very strong +ve gravity wave propagation into the stratosphere. Strongly +ve AO to potentially robust -ve AO? Based on the lag time of the +EAMT.

In that respect, the poleward amplification mechanism has already undergone starters orders and is embedding within the global circulation - and this needs to be taken into account when pondering the eventualities of the MJO progression through the Pacific.

Yet again to say, the MJO, might be a catalyst for future wind-flow changes set in motion within the tropics - but in isolation it is not the be all and end all.

@RainAllNight This post may help answer your question in another way

January 24

@Met4Cast

You are correct. The equatorward fluxing is very much related to the strongly +AO and vigorous polar jet. It is also true that the longevity of this has been uncertain.

But there are now clear signs of quite a potent momentum surge on the GSDM MT plots and a poleward directional +EAMT springboard and stratospheric pathway.

Those fine lines of synoptic outcome under recent discussion look set to swing a pendulum back again. I have no skin in the game, or interest at all, in respect of favoured weather type across NW Europe, especially living in Portugal, but there looks to be a good match to support extended modelling that migrates high pressure NW'ward beyond (approx) the second week of February.

How that fully manifests at this time, cannot be gleaned by anyone at this time. However the likely repercussions of the momentum transport, based on the updated evidence, looks set for the largest diminution within the stratosphere this season.

On the way towards 22C today. Amazing.

Previsão - Temperaturas podem bater recordes entre Quarta, 23, e Sábado 27 em Portugal - Calor em Janeiro

WWW.LUSOMETEO.COM

Previsão de tempo quente em Janeiro, com possibilidade de temperaturas recorde localmente - a Serra da Estrela pode chegar a 15ºC

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023710

January 24

@Met4Cast

You are correct. The equatorward fluxing is very much related to the strongly +AO and vigorous polar jet. It is also true that the longevity of this has been uncertain.

But there are now clear signs of quite a potent momentum surge on the GSDM MT plots and a poleward directional +EAMT springboard and stratospheric pathway.

Those fine lines of synoptic outcome under recent discussion look set to swing a pendulum back again. I have no skin in the game, or interest at all, in respect of favoured weather type across NW Europe, especially living in Portugal, but there looks to be a good match to support extended modelling that migrates high pressure NW'ward beyond (approx) the second week of February.

How that fully manifests at this time, cannot be gleaned by anyone at this time. However the likely repercussions of the momentum transport, based on the updated evidence, looks set for the largest diminution within the stratosphere this season.

On the way towards 22C today. Amazing.

Previsão - Temperaturas podem bater recordes entre Quarta, 23, e Sábado 27 em Portugal - Calor em Janeiro

WWW.LUSOMETEO.COM

Previsão de tempo quente em Janeiro, com possibilidade de temperaturas recorde localmente - a Serra da Estrela pode chegar a 15ºC

January 23

1 hour ago, Penrith Snow said:

Indeed, just been checking historical charts since 2000 and while persistent Bartletts are frequent (as we all know) the size and extent of the current Iberian/Mediterranean High is off the scale.

This is why I have now lost faith in using teleconnections as a forecasting tool, two weeks ago every signal pointed to HLB in late January resulting in great EC 4 weekers and an usually positive MetO MRF, it appears they all couldn't have been more wrong.

And before anyone says I am only looking at UK centred micro developments I am not, the whole NH profile is the exact opposite of those the teleconnections had indicated.

In science when you run an experiment and the outcome isn't what you expected you go back to the drawing board not run it again and again hoping for a different result.

Andy

My post profile does not now go back far enough to quote the relevant excerpts - but sometime around the festive period or early January, I made one particular summary which outlined the fine lines between +ve momentum transport pathway synoptic outcomes according to whether fluxing was poleward (and under unstable stratospheric conditions), or, equatorward (under stable stratospheric conditions or where a reflective warming event occurs). It is perfectly possible to have a compelling signal from a tropospheric diagnostic, but to have an unforeseen and quite unforecastable event within the stratosphere which either mitigates the tropospheric signal or completely reverses it. This make predictive skill harder in winter when the stratospheric and tropospheric relationship is much more volatile and dynamic when the polar vortex is present.

The latter equatorward fluxing is related to recent developments with a further boost to the Hadley cell which is already stronger than average based on climate trends. Believe me, the talk in Portuguese meteorological circles is the impact that these persistent amplified African/ Iberian ridges are having, not just in respect of the intense heatwaves of summer but also negating the rains which the south of the country depends.

With that said, and as it is, a quite glorious period of weather has embarked in this neck of the woods with local afternoon values between 21C to maybe even 25C this coming week which is quite astonishing ( and not normal) for the last week of January.

It is important to understand that the Hadley cell drives the degree of stability of the anticyclonic response and while the HC is undoubtedly in greater ascendancy and more frequently dominating, it still ebbs and flows according to the wider diagnostic forcing changes - and so when that wider scale forcing changes, the High pressure will respond accordingly,

There are no experiments whatsoever. To reiterate, these diagnostic tools are not intended to be fitted to one particular season and one particular weather type. The atmospheric circulation doesn't stand still, after all, between March/April and November/December.

Naysayers who persist with a 1+1=3 approach to applying these diagnostic are the ones that will keep hoping in vain for a different outcome (a HLB outcome) by continuing to try to fit those diagnostic elements to that desired outcome and hoping they shake the double six next time. Better to try and ascertain whether such an outcome is feasible within the range of ALL probabilistic outcomes.

Even then, unforeseen events will occur - but if the reaction is simply to say there is no point in trying to delve into such departures, then every weather bureau globally may as well give up the study of meteorology tomorrow and leave populations at the mercy of trying to guess what might happen from one morning to the next.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023010

January 23

1 hour ago, Penrith Snow said:

Indeed, just been checking historical charts since 2000 and while persistent Bartletts are frequent (as we all know) the size and extent of the current Iberian/Mediterranean High is off the scale.

This is why I have now lost faith in using teleconnections as a forecasting tool, two weeks ago every signal pointed to HLB in late January resulting in great EC 4 weekers and an usually positive MetO MRF, it appears they all couldn't have been more wrong.

And before anyone says I am only looking at UK centred micro developments I am not, the whole NH profile is the exact opposite of those the teleconnections had indicated.

In science when you run an experiment and the outcome isn't what you expected you go back to the drawing board not run it again and again hoping for a different result.

Andy

My post profile does not now go back far enough to quote the relevant excerpts - but sometime around the festive period or early January, I made one particular summary which outlined the fine lines between +ve momentum transport pathway synoptic outcomes according to whether fluxing was poleward (and under unstable stratospheric conditions), or, equatorward (under stable stratospheric conditions or where a reflective warming event occurs). It is perfectly possible to have a compelling signal from a tropospheric diagnostic, but to have an unforeseen and quite unforecastable event within the stratosphere which either mitigates the tropospheric signal or completely reverses it. This make predictive skill harder in winter when the stratospheric and tropospheric relationship is much more volatile and dynamic when the polar vortex is present.

The latter equatorward fluxing is related to recent developments with a further boost to the Hadley cell which is already stronger than average based on climate trends. Believe me, the talk in Portuguese meteorological circles is the impact that these persistent amplified African/ Iberian ridges are having, not just in respect of the intense heatwaves of summer but also negating the rains which the south of the country depends.

With that said, and as it is, a quite glorious period of weather has embarked in this neck of the woods with local afternoon values between 21C to maybe even 25C this coming week which is quite astonishing ( and not normal) for the last week of January.

It is important to understand that the Hadley cell drives the degree of stability of the anticyclonic response and while the HC is undoubtedly in greater ascendancy and more frequently dominating, it still ebbs and flows according to the wider diagnostic forcing changes - and so when that wider scale forcing changes, the High pressure will respond accordingly,

There are no experiments whatsoever. To reiterate, these diagnostic tools are not intended to be fitted to one particular season and one particular weather type. The atmospheric circulation doesn't stand still, after all, between March/April and November/December.

Naysayers who persist with a 1+1=3 approach to applying these diagnostic are the ones that will keep hoping in vain for a different outcome (a HLB outcome) by continuing to try to fit those diagnostic elements to that desired outcome and hoping they shake the double six next time. Better to try and ascertain whether such an outcome is feasible within the range of ALL probabilistic outcomes.

Even then, unforeseen events will occur - but if the reaction is simply to say there is no point in trying to delve into such departures, then every weather bureau globally may as well give up the study of meteorology tomorrow and leave populations at the mercy of trying to guess what might happen from one morning to the next.

January 21

1 hour ago, northwestsnow said:

I was really hopeful after reading Tamara's musings but alas there is precious little as it stands for us to hang our hats on

Fingers crossed we see improvements in the next few days, I personally thought EC det had some potential this morning ..

Just a response to this before vanishing into the background again. Musings based on the best information available at the time. Which matched the diagnostic evidence available at the time.

The SSW blip have been quite unusual with the incredibly powerful reflective nature of the wavebreaking. Equatorward fluxing, strong Hadley cell, and very strong polar jet. As posted a while back - in these situations +AAM momentum transport between the tropics and extra tropics to in turn perturb the polar field through +EAMT - will be negated by equatorward fluxing. Instead of poleward momentum higher latitude blocking, the downstream blocking resides instead across Europe. Sometimes these events hedge along fine lines which makes starkly different outcomes to the Annular Mode.

The science of the stratosphere has come a very long way in the past 15 yrs and the likes of @chionomaniacpioneered a lot of that for this site back at the time. However, and also in respect of the continued skewing of climate change effects - so much more is yet still to be unravelled.

On a personal note, following some very useful rain in the past week or so - the coming 10 days looks delightful down here. Blue skies, winter sunshine....and temperatures during afternoons into the low 20s across parts of the country. Portuguese weather bloggers are looking out for the 25C marker to be breached somewhere. Which even for this part of Europe would be quite something extraordinary in the last week of January.

Not what this thread is interested in, but best wishes to UK weather watchers despite their frustration.

Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5020335

January 21

1 hour ago, northwestsnow said:

I was really hopeful after reading Tamara's musings but alas there is precious little as it stands for us to hang our hats on

Fingers crossed we see improvements in the next few days, I personally thought EC det had some potential this morning ..

Just a response to this before vanishing into the background again. Musings based on the best information available at the time. Which matched the diagnostic evidence available at the time.

The SSW blip have been quite unusual with the incredibly powerful reflective nature of the wavebreaking. Equatorward fluxing, strong Hadley cell, and very strong polar jet. As posted a while back - in these situations +AAM momentum transport between the tropics and extra tropics to in turn perturb the polar field through +EAMT - will be negated by equatorward fluxing. Instead of poleward momentum higher latitude blocking, the downstream blocking resides instead across Europe. Sometimes these events hedge along fine lines which makes starkly different outcomes to the Annular Mode.

The science of the stratosphere has come a very long way in the past 15 yrs and the likes of @chionomaniacpioneered a lot of that for this site back at the time. However, and also in respect of the continued skewing of climate change effects - so much more is yet still to be unravelled.

On a personal note, following some very useful rain in the past week or so - the coming 10 days looks delightful down here. Blue skies, winter sunshine....and temperatures during afternoons into the low 20s across parts of the country. Portuguese weather bloggers are looking out for the 25C marker to be breached somewhere. Which even for this part of Europe would be quite something extraordinary in the last week of January.

Not what this thread is interested in, but best wishes to UK weather watchers despite their frustration.

January 14

2 hours ago, TSNWK said:

Where did the shuffling heights go?

The UK has had them between the UK and Southern Greenland. Apologies for the lack of Scandinavia in the current equation....Predicting the extent of blocking two weeks and more ahead defeats the best professional minds. let alone those studying the weather at at home. The elusiveness of snow in back gardens drives the unreasonable expectations within this thread. And it is very tiresome.

As one who lives in PT, is not chasing or has no vested interest in any particular outcome and is purely interested in how the synoptic patterns played out then barring the suspicion that greater resistance to the end of the UK cold spell might have been stronger than it appears to be, the thinking since the last week of December when there was little sign of what was to come through the first half of January has played out very close to those expectations. And also the expectations of various others.

I suspect alas nothing will ever be good enough for some on here. Including the task of finding a clairvoyant.

Whatever the weather brings, hope all enjoy the rest of the season.

Ciao. Melhores cumprimentos.

January 14

1 hour ago, Windysun1 said:

So basically you cannot forecast with any great accuracy with these signals as there are too many variables?

No, totally the opposite as the post quite clearly explains. It is using the combination of the GSDM data that was discussed which is most inclusive. The MJO composites need to be used in conjunction with those parameters and other daily proxies.

January 14

3 minutes ago, Derecho said:

I think now that things are quietening down I thought it'd be interesting to go through some teleconnections for this period... how well did they verify?

The MJO has been amplified recently and has been my main source of focus. Just before Christmas there was a strong indication we would go into phase 7 and phase 8 and from that I suggested things may start getting interesting from January 5th...

So from the diagram below you can see we went into phase 1 on December 23rd. There is a 10-12 day lag with these...

So what follows a Dec phase 1 in an El Nino year? and what did we get 10 days later?

IMO a good match as you can see the troughing over the UK following some ridging over the mid-Atlantic. Next we went into phase 2 around the new year...

This looks quite different, instead we got the cold easterly following on from the troughing in the north Atlantic. Then we went into a phase 3 around January 4th which strangely looped round into phase 2. Looking at both these composites and what actually happened...

The MJO composites appear to be onto something here with an upper trough dropping towards the UK with heights to the NW, however the area of low heights was focused over Scandi instead. Despite the prolonged period in phase 3 we also see the Atlantic coming in early. My thoughts were the Atlantic would start ramping up around the 25th but it looks to be several days early.

Phase 4 we went into yesterday which can be cold if we are on the right side of a battleground but it looks like we won't be.

If the MJO really is a key driver then is the lag time of 10-12 days reliable because it looks like the phase 4 composite sets in after 5-6 days rather then 10...

Into the future now and as you might expect, phase 5 is poor... and phase 6 is very strongly zonal.

Applying a 6 day lag rather then 10 the mild pattern will take us up to around February 3rd... then the phase 7 Jan and Feb Nino composites are as follows...

A cross between the two suggests a strong mid-Atlantic ridge or a northerly around the turn of the month. However will the MJO remain amplified at this point? We know what happened in December.

However if we can stick it out to phase 7 and 8 we should see some good blocking.

In the more reliable, still some ensemble members are dropping SLP off the west coast of Spain towards the end of the week. It probably won't stop the Atlantic onslaught next week but it may reduce the window for mild air... and keep the weekend more cold and Anticyclonic as the Atlantic is slower to push in.

The discrepancies are accounted for b/c the MJO is only one part of the total global wind-flow budget. As repeated very often on this thread there has to be analysis of the relationship of the tropics with the extra tropics c/o using the diagnostics from the GSDM (Global Synoptic Dynamical Model). Its another fancy sounding acronym, but it provides data that gives a fuller guide to the global atmosphere and associated jet stream as a whole. The MJO composites used in isolation make too many x+y= assumptions about how the extra tropics might behave in a linear fashion to the MJO based on a given ocean base state. The reality is that the fluxing of the atmosphere is more flexible than that and the extra tropical wind-flow can be disconnected from the tropics at a given time based on inertia lags and variations of directional fluxing of MJO eddies into the extra tropics..

Equatorward fluxing of AAM anomalies within the extra tropics will offset propagating poleward attempts of momentum transport and scramble the MJO composite if used in isolation that doesn't account for the contrary signal within the extra tropics. That is, it doesn't read the disconnect in the extra tropics, it just assumes a typical amplification pathway associated with the base state that the composite was selected upon. On this basis, it is not as simple as MJO propagation through Phases 7,8,1 inevitably = HLB. Each situation has to be taken on its own merits.

Based on readiness for the atmosphere to be conducive to poleward (not equatorward) momentum of MJO +ve AAM anomalies associated with a high amplitude propagation to the Pacific, this is one occasion however where a higher latitude synoptic response is much more likely. As reflected by the Global Wind Oscillation which takes account of the extra tropical wind-flow budget as well as the MJO itself.

Equatorward fluxing on the other hand in stark contrast can produce an inflated sub tropical high response through the same amplified Pacific phases. A good example of this was back in February 2019 - where expectations had widely been for a very strong HLB response (and associated with an SSW).

The converse happened with very mild Springlike weather in the UK.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5011584

January 14

3 minutes ago, Derecho said:

I think now that things are quietening down I thought it'd be interesting to go through some teleconnections for this period... how well did they verify?

The MJO has been amplified recently and has been my main source of focus. Just before Christmas there was a strong indication we would go into phase 7 and phase 8 and from that I suggested things may start getting interesting from January 5th...

So from the diagram below you can see we went into phase 1 on December 23rd. There is a 10-12 day lag with these...

So what follows a Dec phase 1 in an El Nino year? and what did we get 10 days later?

IMO a good match as you can see the troughing over the UK following some ridging over the mid-Atlantic. Next we went into phase 2 around the new year...

This looks quite different, instead we got the cold easterly following on from the troughing in the north Atlantic. Then we went into a phase 3 around January 4th which strangely looped round into phase 2. Looking at both these composites and what actually happened...

The MJO composites appear to be onto something here with an upper trough dropping towards the UK with heights to the NW, however the area of low heights was focused over Scandi instead. Despite the prolonged period in phase 3 we also see the Atlantic coming in early. My thoughts were the Atlantic would start ramping up around the 25th but it looks to be several days early.

Phase 4 we went into yesterday which can be cold if we are on the right side of a battleground but it looks like we won't be.

If the MJO really is a key driver then is the lag time of 10-12 days reliable because it looks like the phase 4 composite sets in after 5-6 days rather then 10...

Into the future now and as you might expect, phase 5 is poor... and phase 6 is very strongly zonal.

Applying a 6 day lag rather then 10 the mild pattern will take us up to around February 3rd... then the phase 7 Jan and Feb Nino composites are as follows...

A cross between the two suggests a strong mid-Atlantic ridge or a northerly around the turn of the month. However will the MJO remain amplified at this point? We know what happened in December.

However if we can stick it out to phase 7 and 8 we should see some good blocking.

In the more reliable, still some ensemble members are dropping SLP off the west coast of Spain towards the end of the week. It probably won't stop the Atlantic onslaught next week but it may reduce the window for mild air... and keep the weekend more cold and Anticyclonic as the Atlantic is slower to push in.

The discrepancies are accounted for b/c the MJO is only one part of the total global wind-flow budget. As repeated very often on this thread there has to be analysis of the relationship of the tropics with the extra tropics c/o using the diagnostics from the GSDM (Global Synoptic Dynamical Model). Its another fancy sounding acronym, but it provides data that gives a fuller guide to the global atmosphere and associated jet stream as a whole. The MJO composites used in isolation make too many x+y= assumptions about how the extra tropics might behave in a linear fashion to the MJO based on a given ocean base state. The reality is that the fluxing of the atmosphere is more flexible than that and the extra tropical wind-flow can be disconnected from the tropics at a given time based on inertia lags and variations of directional fluxing of MJO eddies into the extra tropics..

Equatorward fluxing of AAM anomalies within the extra tropics will offset propagating poleward attempts of momentum transport and scramble the MJO composite if used in isolation that doesn't account for the contrary signal within the extra tropics. That is, it doesn't read the disconnect in the extra tropics, it just assumes a typical amplification pathway associated with the base state that the composite was selected upon. On this basis, it is not as simple as MJO propagation through Phases 7,8,1 inevitably = HLB. Each situation has to be taken on its own merits.

Based on readiness for the atmosphere to be conducive to poleward (not equatorward) momentum of MJO +ve AAM anomalies associated with a high amplitude propagation to the Pacific, this is one occasion however where a higher latitude synoptic response is much more likely. As reflected by the Global Wind Oscillation which takes account of the extra tropical wind-flow budget as well as the MJO itself.

Equatorward fluxing on the other hand in stark contrast can produce an inflated sub tropical high response through the same amplified Pacific phases. A good example of this was back in February 2019 - where expectations had widely been for a very strong HLB response (and associated with an SSW).

The converse happened with very mild Springlike weather in the UK.

January 13

6 minutes ago, Eagle Eye said:

Still a while away from the next?+VE EAMT event w/tangible results. Not in the GFS 5 day forecast yet.

Double rise to a significant AAM rise by early February which is what Tamara was talking about w/MJO phase 5/6. That would result in tangible results by mid month. CFS has been insistent on this for the last 3 runs. General support is for a high rise GLAAM response which should be enough to re-invigorate momentum distribution in the Northern Hemisphere to displace the zonal pattern if it did happen. Winter is far from over. It's not all doom and gloom. This would be the strongest rise in a while with it moving towards a 2 S.D rise where GLAAM has spent most of my time in this forum very close to the COD. GLAAM forecasts are rarely that accurate but gloom posters are trying to invoke a response if they're saying Winter is over in January. Im not even going to bother deep diving into the potential responses when looking at the MJO propagation, clearly it's not worth it. Just kidding of course I will.

MJO Nino Phase 6-7 response to have high latitudal blocking and combined with tropical forcing, there should be a constructive interaction signal. Wouldn't get overly confident of x+y = x again, the GLAAM will intefer with the RWT signal either favourably or unfavourably depending on the strength of the GLAAM input into the total distribution. However, a high rise GLAAM + MJO + weak vortex suggests either a wave reflection of the 6-7 state or a total Strat buster and double major SSW technically possible given the Arctic and lower Strat vortex basing of the current one meaning that it should recover well despite the slowest recovery occurring in the lower Strat, it just doesn't really do much damage the major warming though it may cut off momentum feed vertically for a bit post SSWE (appearing likely). Either way, February or maybe March if delays occur are looking good.

Easy to lose momentum and MJO strength and the vortex can recover properly but for now general synoptics are favouring that high tropical forcing. The ENSO support for active MJO phases should probably get some work done soon otherwise we'll have been really unlucky.

While indeed unlikely to show for 5 days based on timetable for eastward propagation of tropical forcing through Maritimes, I would add that those GFS forecasts have never been overly reliable based on a -ve tropical forcing bias that underplays +ve momentum transport.

In respect of potential impacts moving forward, the MJO forcing is better permed with the extra tropical GWO. As @Singularitynoted, global angular momentum levels are still above parity overall during this "lull period" following the easterly inertia added c/o Indian Ocean forcing. Rapid convective suppression will follow in this area and that will be in tandem with the engagement of +ve torques as the MJO cuts through the Maritimes.

Based on existing relatively buoyant levels of AAM in the atmospheric circulation, the GWO is primed for a high amplitude Nino attractor Phase rebound.

Additionally e/QBO shear stress is likely to augment the effects of Rossby wave action on the vortex within enhanced Brewer Dobson transport between the tropical > polar stratosphere at the same time as ensure that the intraseasonal MJO wave itself, based on the periodicity of amplitude waves, does not weaken from forecasted status & via convective velocity potential indicators

For those predisposed to cold outcomes in NW Europe I still see relatively earlier in Feb rather than beyond midmonth for arrival of maximum potential impacts.

But first much to continue to monitor in respect of the next momentum uptick.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5010849

January 13

6 minutes ago, Eagle Eye said:

Still a while away from the next?+VE EAMT event w/tangible results. Not in the GFS 5 day forecast yet.

Double rise to a significant AAM rise by early February which is what Tamara was talking about w/MJO phase 5/6. That would result in tangible results by mid month. CFS has been insistent on this for the last 3 runs. General support is for a high rise GLAAM response which should be enough to re-invigorate momentum distribution in the Northern Hemisphere to displace the zonal pattern if it did happen. Winter is far from over. It's not all doom and gloom. This would be the strongest rise in a while with it moving towards a 2 S.D rise where GLAAM has spent most of my time in this forum very close to the COD. GLAAM forecasts are rarely that accurate but gloom posters are trying to invoke a response if they're saying Winter is over in January. Im not even going to bother deep diving into the potential responses when looking at the MJO propagation, clearly it's not worth it. Just kidding of course I will.

MJO Nino Phase 6-7 response to have high latitudal blocking and combined with tropical forcing, there should be a constructive interaction signal. Wouldn't get overly confident of x+y = x again, the GLAAM will intefer with the RWT signal either favourably or unfavourably depending on the strength of the GLAAM input into the total distribution. However, a high rise GLAAM + MJO + weak vortex suggests either a wave reflection of the 6-7 state or a total Strat buster and double major SSW technically possible given the Arctic and lower Strat vortex basing of the current one meaning that it should recover well despite the slowest recovery occurring in the lower Strat, it just doesn't really do much damage the major warming though it may cut off momentum feed vertically for a bit post SSWE (appearing likely). Either way, February or maybe March if delays occur are looking good.

Easy to lose momentum and MJO strength and the vortex can recover properly but for now general synoptics are favouring that high tropical forcing. The ENSO support for active MJO phases should probably get some work done soon otherwise we'll have been really unlucky.

While indeed unlikely to show for 5 days based on timetable for eastward propagation of tropical forcing through Maritimes, I would add that those GFS forecasts have never been overly reliable based on a -ve tropical forcing bias that underplays +ve momentum transport.

In respect of potential impacts moving forward, the MJO forcing is better permed with the extra tropical GWO. As @Singularitynoted, global angular momentum levels are still above parity overall during this "lull period" following the easterly inertia added c/o Indian Ocean forcing. Rapid convective suppression will follow in this area and that will be in tandem with the engagement of +ve torques as the MJO cuts through the Maritimes.

Based on existing relatively buoyant levels of AAM in the atmospheric circulation, the GWO is primed for a high amplitude Nino attractor Phase rebound.

Additionally e/QBO shear stress is likely to augment the effects of Rossby wave action on the vortex within enhanced Brewer Dobson transport between the tropical > polar stratosphere at the same time as ensure that the intraseasonal MJO wave itself, based on the periodicity of amplitude waves, does not weaken from forecasted status & via convective velocity potential indicators

For those predisposed to cold outcomes in NW Europe I still see relatively earlier in Feb rather than beyond midmonth for arrival of maximum potential impacts.

But first much to continue to monitor in respect of the next momentum uptick.

January 13

19 minutes ago, Singularity said:

Based on the high AAM state limiting the strength of westerlies, I’d not be surprised to see the shift to a more settled outcome next weekend into the week after be repeated again tomorrow such that UKM & ECM keep wet weather north of most or all of the UK, perhaps even with the south holding onto light winds.

Regardless, the high across W or NW Europe should tend to migrate further N or NNE during the final third of Jan as the new high AAM cycle plays out in tandem with an active MJO setting out across the Pacific.

In Feb the response to a Pacfic-crossing MJO becomes most strongly in favour of HLB out of the winter months. No surprise that the seasonal models have been so keen on a HLB dominated month.

Hi James

Agreed The starting pistol for AAM tendency to jump sharply upwards, as I stated yesterday, is from MJO Phase 5/6. Taking into account the very high amplitude of this intraseasonal wave, NWP is likely to come to a screeching halt with attempts at a low pressure conveyor into NW Europe and as you say, the downstream European ridge start to migrate NNE.

Your comment about Feb holds very true about Pacific feedbacks. Significant inflection of +ve MT torque within the extra tropics and likely very strong rossby wave action on the polar vortex. Peak winter wavelengths would support the most extensive blocking regime of the season.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5010799

January 13

19 minutes ago, Singularity said:

Based on the high AAM state limiting the strength of westerlies, I’d not be surprised to see the shift to a more settled outcome next weekend into the week after be repeated again tomorrow such that UKM & ECM keep wet weather north of most or all of the UK, perhaps even with the south holding onto light winds.

Regardless, the high across W or NW Europe should tend to migrate further N or NNE during the final third of Jan as the new high AAM cycle plays out in tandem with an active MJO setting out across the Pacific.

In Feb the response to a Pacfic-crossing MJO becomes most strongly in favour of HLB out of the winter months. No surprise that the seasonal models have been so keen on a HLB dominated month.

Hi James

Agreed The starting pistol for AAM tendency to jump sharply upwards, as I stated yesterday, is from MJO Phase 5/6. Taking into account the very high amplitude of this intraseasonal wave, NWP is likely to come to a screeching halt with attempts at a low pressure conveyor into NW Europe and as you say, the downstream European ridge start to migrate NNE.

Your comment about Feb holds very true about Pacific feedbacks. Significant inflection of +ve MT torque within the extra tropics and likely very strong rossby wave action on the polar vortex. Peak winter wavelengths would support the most extensive blocking regime of the season.

January 13

14 hours ago, Eagle Eye said:

Despite a potential major warming and split (sort of) , the increasing barotropic wave disconnects between wave heat and the wave itself pushing it polewards. This is usual, however...

1) The reversal is unlikely to be strong

2) We are relying on wavebreaking

3) This rules out a reflection unless it occurs before the SSW. This does not rule out future reflections though.

Further on point 2

Longevity of wavebreaking appears to be short and overriden by other factors. Nor does it push equatorward, so it's just a downwelling of - VE zonal mean anomalies for a few days, a failed major SSW proper response if it happens. 2nd in the last 2 major SSW's (pretty sure that one that was in I think 2021 didn't connect with the troposphere). It's possible wavebreaking could still make it down but it appears unlikely.

This is a very good post from yesterday evening that appears to have been missed in the UK "it won't snow in my garden" cacophony. It looks like precise timing of movement of SPV lobes between Canada and Siberia scuppers the notion that the polar jet return was being overplayed following initial amplification that is now in progress.

My niggle of the last few days has been about what should be immense wavebreaking pressure from the MJO progression through Phases 4 and 5 and then continued rossby wave driving on into the Pacific at the high amplitude expected - all being instrumental on diminution within the SPV in such a way as fracture the polar jet more sustainably around the time that this passage of tropical forcing is happening (circa up to 23rd Jan). Which is coincidentally very close to the period the amplified pattern flattens out.

In that sense, whilst a cyclonic period made sense from upstream, following the ongoing current amplification response, the degree of polar jet return to follow didn't.

One of those broken clock situations where taking NWP at face value at more extended time periods does turn out to be correct.

Notwithstanding the override of the SPV lobe movements, I am still suspicious of any over muted response to the colossal momentum drive from the MJO induced tropics to extra tropics passage to the Pacific (and associated tangible effects of surging angular momentum) on any sustainable basis heading to late month and beyond.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5010215

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