Model Output Discussion - Spring Has Sprung

[Stephen W]

2 hours ago, Singularity said:

Some here seem to view a strong Iberian high as a driver of weather patterns - but this is not so, it’s a response to drivers. In this case the forcing leads to attempts to establish a high over N Europe which are countered by the AO being too positive (likely related to the unusual stratospheric events - who’d have rationally bet on that one?), meaning that in a sense, amplification becomes trapped over S Europe.

Due to the MJO & AAM setup, further attempts to shift the high N are likely in the coming weeks (which can happen abruptly even with a strong Euro high). Signs are the first of those in 6 days time will likely fall short & boost the high over C/S Europe instead. Then, however, we are seeing the models tend to raise polar heights as we head into Feb. That improves the chances of the next attempt being successful, regardless of how current modelling paints the picture (they’re not actually that reliable for week 2+, it’s just easier to predict +NAO because it happens way more often than -NAO in N Atlantic climatology).

Emphasis on chance here. As Tamara has said many times over the years, there’s no magic bullet for HLB patterns. As I’ve said before, the most likely outcome isn’t always what happens. With this in mind I’ve found forecast model watching a lot less stressful.

Very interesting and helpful analysis, thank you.  So, it comes down to whether we can remove that strong AO signal in order for heights to build sufficiently north. Background signals are there and as you have highlighted there are some tentative signs in the latter stages of output but all too far away to be taken seriously at this point. At present, it does seem as if it’s rinse and repeat up until end of first week of Feb. All a bit underwhelming…

[bluearmy]

45 minutes ago, Derecho said:

We all know how the BOM MJO phase 7 prediction turned out in December.

I hope we do get into phase 7 but it looks very uncertain to me going by the other models. Phase 6 in January is followed by very mild weather and in February it is cyclonic. We could get stuck in phase 6 for quite a while.

EC does get there on it's ens mean but If we are to get out of this rut, the increasingly slow progression towards a phase 7 means I'm not hopeful of much interesting until the second week of Feb (around the 10th).

By that point we have to start relying on increasingly impressive synoptics to get a good cold spell. If we can't get that I'd prefer a Feb 1998 type of month.

Feb 2018 did show we can get something potent but time is starting to work against us now.

Sorry but my glass is half empty today.

I also do believe the Iberian high is becoming more prominent due to climate change. Problem with that is if we get lower heights over the Azores (which is more common in El Nino late winters), this can actually make things even milder if the Iberian high doesn't subside we end up with a deep fetch SW'ly. Feb 1998 again being a prime example.

Not suggesting it will go that way at this early stage but the GFS is very stubborn with the Euro heights. EC also very poor at day 10.

Ec MJO forecast mean looks low amplitude phase 7 but if we remove the cluster that dies in phase 6 then we should get a decent arrival of amplitude in phase 7 before it heads into COD 

[Singularity]

The Hadley cell is the driver, not the high over S Europe.

An expanding trend to that cell is indeed making such highs stronger & a bit more resistant to change, but it hasn’t given them the power to self-manifest or sustain. The net forcing has to be there in the first place.

As per Eagle Eye’s post, if the net forcing (both tropical & extratropical e.g. polar vortex state) is against a Euro high then it will vacate regardless. This would well prove to be the case by about a week into Feb. If that wasn’t true, the Met Office wouldn’t have been mentioning easterlies & cold temperatures so much lately.

Importantly, the models typically overdo persistence of near term patterns. We notice it often with HLB because of how anomalous that setup is, but it periodically happens with +AO, +NAO setups too. Hence you don’t tend to see me ‘writing off’ a possibility one way or the other based on what the models, even entire ensemble suites, indicate for more than about a week ahead in time.

[Paul]

32 minutes ago, Penrith Snow said:

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.

You may certainly want to look again at things, but would you not also seek to learn why things didn't turn out the way that may have been expected rather than just throwing out an entire set of theories and indicators?

If you just dismiss things as flawed and ignore them if they don't go to plan, where does that end up? On that basis, all the forecasting models would have been in the bin years ago and we'd be back to using seaweed.

Edited January 23 by Paul

[Don]

54 minutes 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.

Are we now at the stage where one has to question, will this country actually see a genuinely cold winter again, or have we now reached the stage where CC has made this virtually impossible?!

[Tamara]

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.

Edited January 23 by Tamara

[johnholmes]

I am pretty sure that meteorologists and climatologists will probably already be preparing learned texts explaining why certain meteorological parameters are now different to what we remember, in my case, 60+ years ago. Just whether they will be proved correct is something that will be evident in a decade or several decades time.

I'll watch with interest from my 'perch' up above!

[MAF]

4 minutes ago, Tamara said:

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).  snip

was it this one?

Quote

Always expect the unexpected.  What doesn't make sense, usually gets supplied with an answer why if one waits for it.  

Equatorial fluxing between the tropics & extra tropics has created intense sub tropical ridging and a vastly inflated Azores/Atlantic ridge. That does, contrary to prior expectations in absence of it, make complete intuitive sense. With this, and stubborn legacy of -ve inertia within the extra tropics on the back of two large -ve MT events across both Asia & NA in mid late November and again in the early part of this month, then angular momentum falls shorter than it otherwise would and much greater polar jet energy is present as a consequence - in tandem with the strong sub tropical ridging.

In the absence, at this time, of any switch in fluxing between the tropics & extra tropics to boost amplification in the extra tropics than a continued mid latitude ebb & flow of ridges is well modelled by NWP and the polar front restricted with its inroads in longevity towards NW Europe. SW Europe stays under the influence of the resident anticyclone.

  On 15/12/2023 at 12:31, northwestsnow said:

Your post the other day was so so true with reference to teleconnections ,they have limitations insofar as our tiny island is concerned

.The biggest elephant in the room is GW ,and the Hadley cell, its a winter killer for Europe..

Looking at the MJO in isolation is not a magic bullet, especially to try to fit to idealised synoptics. As seen in the ongoing scenario where the tropics & extra tropics are so out of kilter and producing a-typical Nina-esque patterns in what is an El Nino background. Any fluxing from tropical eddies into the extra tropics is muted and rather than eddy waves propagating poleward, they serve instead to boost the Hadley cell and bottle up the pole. In this context also, any displacement of the polar vortex is equally subdued by the ferrel cell asserting itself over the polar cell.

Macro-scale meteorological tools are not intended to micro scale forecast for a very small geographical area in the first place. They assist a framework for the larger hemisphere scale pattern to be evaluated within which that micro scale area exists. But more than anything else, as is always on auto-repeat - no diagnostic approach is intended to be skewed into fitting an idealised weather preference & outcome. Which is why so much mood driven emotion consumes this thread between about November and March.

  On 17/12/2023 at 11:16, Kasim Awan said:

Often happens in El Nino years, warm September was a giveaway aswell. EQBO + El Nino combination works in our favour a little though.

x+y= theory does not work in straight equations like this. The precise atmospheric circulation in existence at a given time has to be taken on its own merits - there is no given linear response. This post detail, again, tries to illustrate that. 

 

[Rain All Night]

15 hours ago, RainAllNight said:

An overview of this afternoon's global model runs.

Deterministic runs, Tue 23rd to Mon 29th

The prospect of dry weather for the south looks reasonable from Saturday onwards. Not sure the wind direction is going to go down too well with many of my fellow members here though!

Ensemble means, Tue 30th to Mon 5th

And it looks as though the theme continues. I would rather this than more storms.

A summary of this morning's global model runs.

Deterministic runs, Tue 23rd to Tue 30th

Ensemble means, Tue 30th to Tue 6th

Bonus

If this is how it's going to be, then I hope we might at least do it properly!

Edited January 23 by RainAllNight

[Catacol]

4 hours ago, Singularity said:

Some here seem to view a strong Iberian high as a driver of weather patterns - but this is not so, it’s a response to drivers. In this case the forcing leads to attempts to establish a high over N Europe which are countered by the AO being too positive (likely related to the unusual stratospheric events - who’d have rationally bet on that one?), meaning that in a sense, amplification becomes trapped over S Europe.

Due to the MJO & AAM setup, further attempts to shift the high N are likely in the coming weeks (which can happen abruptly even with a strong Euro high). Signs are the first of those in 6 days time will likely fall short & boost the high over C/S Europe instead. Then, however, we are seeing the models tend to raise polar heights as we head into Feb. That improves the chances of the next attempt being successful, regardless of how current modelling paints the picture (they’re not actually that reliable for week 2+, it’s just easier to predict +NAO because it happens way more often than -NAO in N Atlantic climatology).

Emphasis on chance here. As Tamara has said many times over the years, there’s no magic bullet for HLB patterns. As I’ve said before, the most likely outcome isn’t always what happens. With this in mind I’ve found forecast model watching a lot less stressful.

This is a really good explanation of the real context behind the latitude of high pressures in winter. For those who believe that an Iberian High drives the pattern it would be worth scanning your eyes over general north atlantic patterns in summer when there is no vortex. This gives you a sense of the "true" tropospheric inclination towards pattern evolution and you will note that, in general, we see a lot more high pressure cells floating around at a more northern latitude than in winter. The impacts of the winter polar vortex are the reason why these high pressure tendencies are squashed down, and the latitude of the jet, impacted itself by the polar vortex, is key in this too.

The Hadley Cell exists, and there is evidence it is getting stronger. But the idea that a specific Iberian ridge is acting as a driver of the pattern in our sector is a stretch. It is a symptom of other goings on. If we go back to the origins of generally more dominant westerly patterns I think we start with the temperature of the stratosphere, being driven down by the impacts of rising CO2. 

And to keep this post relevant, this is not a chart that fills my wintry heart with icy joy. Strat vortex now spinning faster than average and forecast to remain so

Doesn't tell the whole story because, lower down, we have temperatures continuing to run a fair bit above average

and this will be aiding in preventing a full on downwards coupling of westerly forcing. We need the fates to jump onto our side a bit here and prevent this kind of solid looking 10hpa forecast on GFS today downwelling through February.

Looking at pressure anomalies at present I'm not seeing anything digging in to suggest significant disruption of the vortex as we move through February. Snow lovers like me are going to need place a lot of faith in a very active pacific pattern and (hopefully) a jump in momentum. The MetO text continues to keep the door open to a cold outbreak, though I'm starting to wonder if the constant mention of low probability cold air from the east with snow impacts is anything more than a media marker against a low probability outcome to keep all bases covered. It did feel that the text in late December was seeing something develop in January. My fear would be that the failed SSW and now up gunned vortex at 10hpa has spoiled that potential. I'd love to know what Glosea based the strong February -NAO outlook on.

 

Edited January 23 by Catacol

[Battleground Snow]

Latest gfs and gem/CDC mjo plots have moved towards the ecm (non BC) in gaining some amplification, through 6 towards 7.

After that then potentially reamplfiying right at the end.

Cfs really goes for it.

Obviously just one piece of the puzzle but, it should promote blocking in favoured areas around 13-14th February with the lag factored in ( just outside the extended model range) but the signal is there on the weekly ecm graphs.

Just a hunch, but there is a probably a good chance late February and March will once again be the best time for some cold and snow outbreaks in Western Europe.

It is infuriating watching that tpv stuck to Greenland every run atm in the heart of winter

 

 

 

[Don]

39 minutes ago, RainAllNight said:

Bonus

If this is how it's going to be, then I hope we might at least do it properly!

It's look increasingly likely that February will usher in an early spring as opposed the the 'main course' of winter!  I know there is the 2nd half, but experience tells me this is a long shot once a pattern sets in as modelled, thinking back to the likes of February 1990 and 1998 etc.

Does not inspire me whatsoever! 

[Midlands Ice Age]

1 hour ago, johnholmes said:

I am pretty sure that meteorologists and climatologists will probably already be preparing learned texts explaining why certain meteorological parameters are now different to what we remember, in my case, 60+ years ago. Just whether they will be proved correct is something that will be evident in a decade or several decades time.

I'll watch with interest from my 'perch' up above!

John.

 I feel the same way.... I'd love to see this through ... but.. 

I have tried to rationalise (for my own piece of mind)... all of the above posts and come to the following conclusions.  (in very simple terms)-

The weather at our latitude say 45 - 65N , sees a constant battle between 2 major forcing 'agents'.

1) The polar vortex. It determines the strength of the polar and northern hemisphere jet-streams, - which frequently determine the weather at our latitudes. However strength of the vortex can be affected by factors such as the overall polar temperature (AGW?)  - and other agencies such as a stratospheric 'warming' or even more by a full SSW. .  These latter 2 'agents' are themselves  jointly produced(?) by ineraction between it  and the other major atmospheric feature of our northern hemisphere atmosphere -

2) The equatorial/tropical  climate pattern behaviour.  or whatever it is called. It is made up like a jigsaw and is in constant flux, though apparently does not see the same warming as at the pole.

It mainly originates in the massive Pacific ocean, by means of oscillations and eddies which  can drive up into our latitudes and even beyond at times. However, whilst a very strong vortex would probably he able to withstand these affects in one part  of the hemisphere it would still allow any  weakness else where for it to push up further north.

and in the Atlantic 

 3) The Hadley cell - our main buffer against  these southern intrusions - which can occasionally get pushed out of the way in the winter.. , but which can move northwards more  easily when the vortex dies back in the summer.  

So in my simplistic terms,  the Spanish 'high pressure' is an extension of the Hadley cell and is  one of those instances when the vortex is relatively weak. (as it is now in historical terms) and allows the  tropical interaction to be  able to find a jink in the northern jet (the southern arm at any rate) into which it gets promoted and can develop, and then can push further north.. 

It is a feature developed because of the constant ever changing balance within the equatorial and polar forces..

When the vortex is colder it will give more strength to the jets enabling them  to push further south, and then prevent any push northwards of the Spanish high..

Clearly, something has changed..  Mediterranean climate was characterised by warm very wet winters ... where have they gone in recent years.?

I hope my simplistic way of looking at things is useful to some...

MIA

Edited January 23 by Midlands Ice Age

[TillyS]

@Midlands Ice Age

Indeed and as mentioned previously by @Penrith Snow, the one teleconnection that is frequently left out of discussion here on the model outputs is climate change. I know that sounds horribly vague when we’re dealing with intricate scientific weather patterns, but it’s affecting so many of the upstream signals. Right down to the SST anomalies off the Azores, for example.

Someone mentioned the other day that we seemed to have had in place the synoptics for last week's cold snap to be memorable. To turn into something that was seen by those older than I in the 1970’s and 1980’s. It really was looking juicy, with some truly eye-popping charts on the ECM for instance. Then it all went down the pan.

Maybe every time we see a juicy looking chart that’s out beyond T168 we should then stop and ask ourselves, 'now how might a warming climate affect the outcome?'

It was always knife edge in this country. Now it seems to fall the wrong side 19x out of 20.

 

[Dennis]

 

Febr is heading for a new winter phase , days of ideas between 3-5 febr 

but thats only the first setup......

 

Edited January 23 by Dennis

[Dennis]

AO and NAO ideas 23-1

[BarnetBlizzard]

Is it me or have there been some small upgrades to MJO forecasts in last day or two? 

 

Edit: Just seen Battleground Snow's post agreeing that there has been some amplification in some forecasts towards phases 6 and 7

Edited January 23 by BarnetBlizzard

[Penrith Snow]

Some great debate in here today, I have learnt a lot.

We might not all agree but it’s been great to read informed post without anyone point scoring.

I am pleased the mods allowed this as it was a little off topic but important nevertheless 

Andy

[Stravaiger]

@Penrith Snow - totally agree.

I think the bottom line is that the impacts of CC are manifesting in the increased frequency of certain weather patterns in the winter, as @Catacol alluded to.

My simplistic understanding is that GHGs stop heat escaping from the troposphere into the strat, cooling the strat, which in turn gives us a tighter sPV and tPV, with the polar jet pulled poleward, which allows HP to ridge north into southern Europe.

Fascinating discussion though and just hope the tropical forcing comes to our aid soon.

Thanks all!

[Daniel*]

I think the met office update is more a reflection of what models are showing not that it’s necessarily right. ECMWF and most of guidance now converging on entering phase 7 this weekend factor a 10 day lag. Surely with rising AAM which I hear GFS especially has a low bias an opportunity can arise before mid point of Feb? Unless vortex scuppers northward blocking potential. Feeling sceptical at the moment in general.

[Catacol]

@Stravaiger Spot on. Your analysis of CC impacts I would say nails it.

To the Mods - taking out the Quote option completely is a mistake. Anyone who wants to know what it is I am agreeing with here now needs to backtrack through the thread. For any who choose to follow key posters only, rather than read every single post, that is hard work. Can we have quote as well as reply??!

Minor edit - this is Stravaiger's good analysis, copy and pasted:

"My simplistic understanding is that GHGs stop heat escaping from the troposphere into the strat, cooling the strat, which in turn gives us a tighter sPV and tPV, with the polar jet pulled poleward, which allows HP to ridge north into southern Europe."

Edited January 23 by Catacol

[Paul]

2 hours ago, Catacol said:

To the Mods - taking out the Quote option completely is a mistake. Anyone who wants to know what it is I am agreeing with here now needs to backtrack through the thread. For any who choose to follow key posters only, rather than read every single post, that is hard work. Can we have quote as well as reply??!

You do - more info here: 

 

[Daniel*]

Not sure this is entirely relevant but I thought it would be of interest with recent discussion. I recently plotted January mean temperature the station is Heathrow and the trend for past 30 years has been rather flat, with 10 year moving average. This contrasts with December and February. The idea this winter month in particular is rapidly changing does not conform with temperature data, to have memories of those cold Januaries of 1980s for example you will have to be at least 40 years old. The reality is a rather large segment of the population has never experienced frequent cold midwinters. This is not a new revelation it has been happening for decades now.

Edited January 23 by Daniel*

[Mike Poole]

23 minutes ago, Penrith Snow said:

Some great debate in here today, I have learnt a lot.

We might not all agree but it’s been great to read informed post without anyone point scoring.

Yes, I agree.  Some very interesting contributions today, thanks everyone.  (And so much better than the kind of ’I didn’t get any snow so everything's rubbish’ argument that derails the thread.)

I have always had the view that Iberian heights in winter were a consequence, not a driver, but it is really useful to have read more in-depth views on this, because it will no doubt be a subject that continue to crop up in winter, if the frequency of these patterns has indeed increased due to climate change.

I agree with @Battleground Snow that the MJO predictions are improving.  Particularly, the additional data point for 22nd Jan is considerably more amplified in phase 5 than the models predicted it on 21st Jan, so let’s hope that this trend can continue until it gets round to phase 7 or 8.  

[Duane S.]

I agree with @Mike Poole, I'd say the bulgey Iberian high is more of a consequence than a driver in its own right, but... at the point of forming, it now becomes a driver.

It is more than just semantics as well.

It is probably just too simplistic to label xyz as a pure and simple driver. The feeback mechanisims involved within the atmosphere will have us going around all chasing our tails as we seek the chicken from the egg (or vica versa etc etc etc... ) .

I tend to view it on a simple pretext that high pressure fills in as low pressures are created and driven around the globe. Not withstanding of course, the fact that low pressures can't exist without high pressures and and the continued redressing of equilibrium in the atmosphere.

 

 

Edited January 23 by Duane S.