Model discussion highlights

[sebastiaan1973]

26 minutes ago, Penrith Snow said:

I a  not sure Singularity is correct about the Iberien High being a response not a cause, its chicken and egg.

Check out a 100 years of historical data pre 1988 and you won't find such a massive and persistent Iberain/Mediterranean High as we see modelled now, it just didn't happen and of course the current persistant Bartlett is only the latest in a long line since the 1999's.

IMO, the Iberian High dominance is due to the expansion of the sub tropical Hadley Cell in response to a warming world, the expanse forces the Jet Stream north preventing the PV leaving its natural home ie Greenland, it happens occasionally of course like last week but any change is pushing againt the new normal and is quickly crushed.

This I feel is the over riding factor and overwhelmes other natural signals that might encourage Northern Blocking, hence the late January early February forecast debacle.

Watch the MJO if you like but it will make little difference 

Andy

Science seems to back your thoughts. 

he Azores High is a persistent atmospheric high-pressure ridge over the North Atlantic surrounded by anticyclonic winds that steer rain-bearing weather systems and modulate the oceanic moisture transport to Europe. The areal extent of the Azores High thereby affects precipitation across western Europe, especially during winter. Here we use observations and ensemble climate model simulations to show that winters with an extremely large Azores High are significantly more common in the industrial era (since ce 1850) than in pre-industrial times, resulting in anomalously dry conditions across the western Mediterranean, including the Iberian Peninsula. Simulations of the past millennium indicate that the industrial-era expansion of the Azores High is unprecedented throughout the past millennium (since ce 850), consistent with precipitation proxy evidence from Portugal. Azores High expansion emerges after ce 1850 and strengthens into the twentieth century, consistent with anthropogenically driven warming. https://www.nature.com/articles/s41561-022-00971-w

 

5 minutes ago, Duane S. said:

It will change of course but thats incredible how the mean, over 6 days, steadfastly refuses to enter phase 8 !
 

Amplified P7 should (eventually) at least help our cause P6 at this stage of winter in this ENSO state is more of a wild card I’d say?

I guess we all remember BOM in december  

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5022912

[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.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5022974

[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.

 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023036

[Penrith Snow]

I a  not sure Singularity is correct about the Iberien High being a response not a cause, its chicken and egg.

Check out a 100 years of historical data pre 1988 and you won't find such a massive and persistent Iberain/Mediterranean High as we see modelled now, it just didn't happen and of course the current persistant Bartlett is only the latest in a long line since the 1999's.

IMO, the Iberian High dominance is due to the expansion of the sub tropical Hadley Cell in response to a warming world, the expanse forces the Jet Stream north preventing the PV leaving its natural home ie Greenland, it happens occasionally of course like last week but any change is pushing againt the new normal and is quickly crushed.

This I feel is the over riding factor and overwhelmes other natural signals that might encourage Northern Blocking, hence the late January early February forecast debacle.

Watch the MJO if you like but it will make little difference 

Andy

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5022897

[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.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023136

[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.

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

[Cambrian]

The ensemble means have been an outstandingly useful indicator this winter. As noted by @bluearmy last night, only in the run-up to Christmas, when they toyed with the northerly, that got put back and back and then didn’t happen, have they erred. They’re great, but not faultless. For example, they also have the characteristic of often not being able to extend a more decisive trend to days 12-15 due to the averaging out that is incident upon them by their nature. All in all though, I do find them consistently very informative up to date 12. 

So here are the 0z ECM ensemble means to day 12 for heights and pressure, and the T850s. Again, as with the GEFS yesterday, we see the PV getting torpedoed, but here we also see the subsequent setting up of the main lobe over northern Scandinavia and northwest Russia. 

 

Notice the Iberian heights steadily on the wane from day 9. Ideally, for a proper cold shot it would be good to see the trough settle in a tad further west, hanging south into Denmark, but no bones about it, this is a much better prospect now developing in week 2 than we’ve been looking at of late.

The T850s past around day 7/8 are never that numerically informative but are useful for observing trend. The milder / colder zonal pattern that removes the cold air from Scandinavia through the coming week is itself replaced, over Scandinavia at least, by a good push back of the cold air from the northeast from around day 9 through to day 12.

It looks to me that it’s from around there that it begins to get more interesting again in terms of potential wintry weather for northwest Europe. Cold air reinstalled to our northeast, along with a relaxation of the Iberian heights. It still looks changeable but incoming systems are going to have to negotiate interaction with the cold air. 

And the day to day adjustments are getting interesting too. The 0z EPS for day 12 from yesterday, compared with the 0z from today for day 11.

 

Not only is the trough deeper and the low heights further south and west closer to the Finnish border, but the heights up through Greenland and to the west of Iceland are markedly better too. The cold to the northeast is gaining a foothold.

It’s attritional, but bit by bit, the outlook is getting steadily more and more interesting.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023690

[Tamara]

 

@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

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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

[Tamara]

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

[Catacol]

@RainAllNight - Tamara has answered your question and I'll add a bit to it. Recent discussion around failed blocking at the end of this month has not centred on a "failed" process. Indeed, as expected, the pendulum nature of momentum swings started back in favour of blocking at about the expected time (ended up 16 Jan, could have been a day or 3 earlier but this fits within the noise) but what changed was the overriding strength of a reflective stratospheric event that was not forecast. I'll go a bit further than that - unless you are Simon Lee who has written on this subject I'm not sure that the way the stratosphere responds to vertical wave assaults is well understood at all. Simon himself, a pretty modest and helpful X poster, would probably quickly agree that there is a lot we still need to learn.

So - this reflective event has overridden the tropospheric signal that started as expected. The week we are in now was always flagged as vulnerable to a flattening pattern, and the strat response has flattened it hard and fast. The impacts of that flattening will now endure through next week it appears....but all the while the forcings pushing us towards renewed northern blocking are gathering in strength as many of us thought they would through this period and out into February.

The question will be - can the bottled up effects of a momentum surge overcome the strat quick enough to make an impact before we get too far through February? Earlier this week I felt quite glum about that - chances in my mind reducing. I look at strat forecasts for the month and am still not confident that these tropospheric forcings can seize control from the strat once again....but I feel a bit more optimistic about that today. Why? Well - not as a result of this chart which looks horrendous...

but more maybe as a result of this - already posted by Tamara

and linked to that the high spiking nature of the calculated tendency which is, without doubt, going to drive us back towards a tropospheric disposition towards higher lat blocking.

That MT spike is very significant. It has arrived as expected but looks bigger to me than I expected and that is good for winter fans.

I cannot help but curse our luck this month. First a failed SSW, and noone expected it to fail - indeed the strat big guns all came out and started to celebrate in the run up - and then a really positive tropospheric setup that has been undermined and stalled by an unexpected and not fully understood impact of strat developments. It could all have been so very very different!

Watching battle commence between this momentum-led forcing and the strength of the SPV will be an interesting watch if nothing else. We can but try and learn. Perhaps, after 2 bouts of poor fortune and a truncated cold snap sandwiched between them, we can strike it lucky in February. I remember some epic snowy February weeks - 1991 and 1996 at the top of the pile and it would only take a week like that to save this winter from mediocrity. 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023764

[Kirkcaldy Weather]

No need for me to spend too much time adressing those who still like to bash and dismiss the teleconnective aspects and in turn us that base our work / posting on them, I'll refer to my post from 7 months ago

 

I can assure everyone that the 500hpa setups which are developing are very much in line with said teleconnective feedback. So building on from my previous post 

 

I've not done a single post over in the stratosphere thread since October 12th 

 

however 104 days on I feel its time to add my input

Everything is coming together nicely through the rest of Jan and into February 

 

Starting with how the Stratospheric Vortex has behaved of late, using the zonal wind data off stratobserve we note there was a reversal in zonal winds albeit relatively brief in nature 

Classification on stratospheric warmings are a bit of a point though I'd hazard a guess we can technically class that as a major SSW but I'll leave that aspect to those who specialise in the stratospheric element.

Credit Butler et al 2015 to explain my above statement 

You can also see from the zonal winds we've seen a quite rapid increase to a point which is hovering roughly slightly above - on average for zonal winds at this timeframe however we are seeing an excellent showcase of the 500hpa and surface temperatures as a result of a stronger vortex.

Bear in mind this includes La Ninà responses however it's effectively the same.

As discussed in my previous post and in line to MJO feedback these are paired to bring above average temperatures across wider swathes but there are still colder temperature anomalies which become focused over the southern regions in the Northern Hemisphere again a good amount moving into Asia, also Greenland, Alaska and the West Coast of America go below avg.

Patterns we are witnessing into February are exactly what to expect 

b and d 

e and h ignore the ticks that is from a post I done last year, however those are pretty close to the patterns we've had during our recent cold setup

Heading through the 1st week of February we are seeing precursor 500hpa pattens which are conducive for stratospheric warming(s)

We'll also have feedback from the MJO entering the Pacific.

As things stand we're looking at at least two weeks of the MJO being active in the Pacific roughly January 24/25 through January 7th but the extended data is supportive ATM of a 3rd week still prominent within the Pacific Taking the progress into / nearer Mid January 

This also plays into stratospheric warming with phases 6 and 7 having a stronger correlation with weakening the stratospheric vortex and a large portion of prior warmings having occured with the MJO within the Pacific 

 

All classic El Ninò characteristics into February week 1

 (a)

Thanks for reading.

KW

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024019

[Cold Winter Night]

The EPS regime chart is helpful for showing overall regime tendencies in the EPS ensemble out to day 8.

Two days ago it showed us staying on the Pos. NAO side:

Yesterday a bit more spread appeared:

But today in the 0z, we see a firm signal for a move towards Neg.NAO (left side of the chart) / Atlantic Ridge (bottom half of the chart) in about 7-8 days time:

Some light at the tunnel, or so it seems, with a potential switch to a more promising pattern, well within the period when winter still can have teeth.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024219

[Cambrian]

The devil will be in the detail as ever, but there is a consistent story emerging in the broad evolution in week 2, of a slow and steady fall in heights and pressure through Northern and Western Europe, the southwestward extent of which is important and to be firmed up over the coming days.

From the 0z and 6z GFS mean (note the inter-run variability) and 0z ECM mean…

  

0z ECM ensembles for Birmingham and Madrid. The ECM can be hawkish with respect to letting go of heights, so a universal 12mb drop in pressure on the mean during the first few days of February is significant…

 

…and particularly so in the context of those heights rises out west and the diminishing zonal flow - yesterday”s EC46 for 5-12 February, pressure and heights…

 

Very clear in all these is the establishment of the trough in and around Scandinavia and northwest Russia, and in some runs this is setting up further west over Denmark like here on the 0z ECM control, with some cold air and good wintry potential entrained for the UK and Ireland…

 

Though this doesn’t appear to have much scope for being deeply cold or long lasting, it is in keeping with the gaining trend by that stage for synoptics that are looking to actively entertain incursions from the northwest or north. 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024227

[johnholmes]

Upper air analysis 26 January 2024

One week on so another update; not done earlier as nothing was showing on any of the 3 charts to suggest anything even slightly different from our weather this past week.

NOAA 6-10 has slowly over the past week changed troughs/ridges, or at least, some aspects in the far west. In the UK area/Europe then the European ridging, more especially, the position of the +ve heights has shifted from way east to a more westerly point ( on the 6-10 it is now centred 50N 20W at 210 DM. This movement is not dissimilar to how it developed prior to the last cold spell! I’m not saying this will happen again simply stating facts. The 8-14 edges it a shade further west but, as is almost always the case, with a lower +ve height value.

ECMWF shows a general flow just north of west on its output (31/1-4/2) with a flattish upper ridge over central/eastern Europe being replaced by a flattish trough in much the same place. Its 850 temperature values eventually by day 5 the 0C lying from N Wales to the Thames estuary.

UK Met on their 3 day charts from T+144 30/1-1/2 a mainly westerly flow with an upper ridge finally settling just west of Portugal

So all 3 show a similar upper air pattern developing over the relevant periods of their forecast period.

As is often quoted on the model (forecast) thread, more charts are needed to see what is likely to transpire.

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

UK Met Office Fax Charts - UKMOMSLP Analysis and Prognosis

WWW.WEATHERCHARTS.ORG

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UK Met Office . . Europe and North Atlantic MSLP analysis and prognosis charts

 

 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024623

[Tamara]

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

[Catacol]

1 hour ago, Tamara said:

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

Agree - spot on. I've been keeping my head down as we live through this westerly, mild mush that darkens my day so much - not because I dislike getting up into a warmer house or dislike opening the windows when the sun pops out and it is 13 degrees outside....because I enjoy that very much in Spring!! But the seasons define the ebb and flow of the yearly calendar, and when winter is routinely so mild and damp and windy and dross-like it does not improve my personal mood. I grew up with snow in the 70s and 80s and would love those days to return. CC likely means not for a generation or 3 at least.

Back on topic - I agree with you - this is what it will be all about. Can these substantial tropospheric drivers seize control of a pattern that could yet be held tight by the SPV? Showing another representation of peaking momentum, here is the relative tendency from earlier this week

Here is the sharply rising total AAM budget

and here now is the fast rising GWO orbit, a representation of windflows that demonstrate how predisposed to a blocking pattern these windflows are

This is all good news - as good as the last rising phase at an earlier stage I would say, and likely therefore to exceed the totals we got that set up the mid January cold snap.

Meanwhile....the vortex stays strong

but according to GFS a growing signal that the lower layers are going to be firmly displaced over to the Siberian side as they were in December by early season warming from Canada

The door for a NW centred block is very definitely being opened here. Can we push it wide and let the wintry floodgates open? The latest CPC text on the MJO, a key feature of the overall wave driving operation, is rather tasty:

"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:

January has done a lot to knock the stuffing out of cold winter forecasts and forecasters, whether that be because of failed late month progression that indicated cold longevity or the comments of those quick to jump on the fail as evidence of the pointlessness of trying to forecast the unforecastable. We move on from all that. February starts next week, there is a distinct chance of a cold spell through mid month and beyond and that without a SSW or even a weakened vortex. The cold light of post season analysis is going to provide some very useful bits of guidance and information for seasons ahead, whether or not we land a proper cold snowy surge this winter or not. And there is still March to come, arguably the month that has delivered the most over the last 10 years or so.

So.... here we go again on another chase. Winter would be dull without them even if, like the a tiger, we fail more than we succeed in our hunt.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024700

[Kirkcaldy Weather]

As mentioned in my post here 

 

"With the above we can see some of the important 500hpa setups developing into our current timeframe and into week 4 of January (and beyond)

Low pressures from Greenland and into the Arctic

High pressure forming across the Maritimes. A secondary high toward the Northwest of the US and Canada which links with PNA behaviour more on that shortly.

Formation of cut off low(s) in that southwestern America > Mexico regions which also will lead into PNA behaviour.'

'Following on from this as the preceeding MJO phases input begins to feed into the setups from week 4 of Jan onward the above remains true with further developments.

Looks like this initial cut off low will develop into a +PNA during the very end of Jan"

As the positive PNA feedback progresses eastward pairing with the MJO patterns I've covered in depth, a +PNA does have a tendency of being supportive for Atlantic ridging / blocking which moves in the direction of Greenland and in connection to a trough further east ie Scandinavia, Baltic regions which gives a doorway for something cooler > colder from the north.

 

 

Though I'm not putting a massive amount of emphasis into exact timeframes from my POV ATM it's looking favoured for this by approx February 4th / 5th and starting to see a possible redux around 1 week later ie 11th / 12th February.

 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024752

[northwestsnow]

EC det looks a milf outlier 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5025088

[Cambrian]

0z ECM nails it from my perspective, day 1-15 animations for the control (in effect the op past day 10) and mean.

The main PV moving east out of Canada / Greenland to Scandinavia during the next week, before regathering and drawing a proportion of the Scandinavian lobe back west, on the op and reinforced by the mean.

 

Chances for a northerly blast for a few days around day 10 before the pattern flattens again, except with the jet stream markedly further south, the flow is by then zonal but cold. The jet stream on the op and the mean T850s.

It’s not deep cold but far from wall to wall mild either, the clear trend for colder air further and further south into week 2. 

 

It’s what the op is showing signs of doing at the end of the run is what is most eye-catching though. The regathering of the PV over Greenland is brief, the (by then) Siberian lobe is dominant, and successive systems are being passed from Greenland southeast to the base of the Siberian lobe. 

By the end of the run, the remnant limb of the PV over Greenland looks like it’s going to catch the same train, swing south east and reconsolidate the PV from Siberia through to Scandinavia, with very little PV left back out west. A system is working its way through Canada and the US and is looking to pump heights up into Greenland. Very interesting.

A very long way off for now, but we’re getting close to the beginning of the initial very well telegraphed evolution with regard to the PV now, so for me, this is getting exciting - from a mild start, the models showing signs of being on the all go from here into a progressively colder February.

Have a great day.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5025137

[WYorksWeather]

Slightly odd setup on the GFS 18z. Ends up being a cold outlier, but how about this for a bit of ridiculousness.

At T+72, we have a deep low to the south of Greenland, but a block setting up above it.

This low then moves eastwards and deepens absolutely explosively, getting down to 935mb at T+96.

Extreme conditions resulting for northern parts of Scandinavia at T+120, an exceptionally severe storm. Between T+96 and T+120 at one point the central pressure dips below 930mb!

 Here's the mean wind chart at T+96 from the OP run.

130km/h mean winds. That would be equivalent to a mid-range Category 1 hurricane. Absolutely bonkers.

ECM usually has a more realistic outlook on intensification, and though it still becomes a very deep low, the 12z run only deepened the feature to 945mb, and kept it further north.

I think with this we can consider the GFS 18z run a little bit suspect, as the forecasted intensification of the feature looks very unlikely.

 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5025377

[Duane S.]

Much better signs of a change in our favour, albeit possibly quite a slow transition, from second week of Feb onwards. Very difficult to pinpoint many (any?!) details at this stage though…

The MJO dipole progression out of the Indian Ocean, through East Asia and into the Pacific was fairly rapid. It has continued motoring and has already powered through the western Pacific, where it will probably slow down. That quick-ish eastward propagation I assume was aided by the existing ENSO state. Although interference between the two tends to create a lot of noise and especially downstream in model output.

Net result though, it is virtually into P7 at a decent (maybe surprising?) amplitude.

Then perhaps… a slowly decaying El Niño may (just) prevent a more natural slide back into the COD later in the month, and the MJO even potentially progressing further to phase 8

Certainly not a prediction, just musings, but I think it will definitely be worth watching. A decent amplitude 7/8 for a period of time would (in all probability) greatly improve our late winter prospects.

 

Longer term output…

 

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5025525

[Cambrian]

One of those times when it’s of particular benefit to have modest expectations of the models in the nearer ranges, not be swayed too much by individual operational runs and focus on the core evolution of what is actually being shown. 

6z GEFS staying true to form with the modelling of recent days.

Stage 1 : day 1, getting some fresher air in behind the cold front passing through tonight. Might see the sun tomorrow! Note the low to the east of Greenland. 

 

Stage 2 : day 3-5, the low moves through the Norwegian Sea to northern Scandinavia. This is the first (unsuccessful) attempt at setting up a Scandinavian trough. A strong build in heights to our west over the Atlantic is squeezed flat by day 5 as the next low exits Greenland. However, this one’s the boy for Scandinavia.

 

Stage 3 : day 7-9, the low pressure sets up over Scandinavia, while there is another northwestward build of heights up through the mid Atlantic, an important phase as it pushes more directly north through Iceland, ridging north to Greenland. This build in heights keeps a substantial separation between the Scandinavian / NW Russia and eastern seaboard troughs, and pulls the flow through northwest Europe around more to the north.

 

Stage 4 : day 10-12, the trough extends back west through Western Europe, clearing the heights out of Iberia, a decent cold signal developing by then, and at this range, not to be sniffed at.

  

It’s a very well repeated core evolution of the models of the last few days. I’m looking forward to seeing if and how exactly something like it might transpire!

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5026060

[Kirkcaldy Weather]

 

Warnings issued

 

Starting to get a cleaner idea of the likely direction / evolutions through February and heading into March, firstly I'd like to show whats been happening with the below average temperatures zone I mentioned which is running across the southern regions of the Northern Hemisphere 

Azerbaijan & Iran

 

 

 

The colder temperatures at surface and upper levels will gradually continue eastward and move across Asia by one of the timeframes I'll talk about in a sec.

 

'As the positive PNA feedback progresses eastward pairing with the MJO patterns I've covered in depth, a +PNA does have a tendency of being supportive for Atlantic ridging / blocking which moves in the direction of Greenland and in connection to a trough further east ie Scandinavia, Baltic regions which gives a doorway for something cooler > colder from the north'

"Though I'm not putting a massive amount of emphasis into exact timeframes from my POV ATM it's looking favoured for this by approx February 4th / 5th and starting to see a possible redux around 1 week later ie 11th / 12th February."

Looking like a decent set of estimates and further excellent representation of exactly what I'd expect from the MJO feedback.

Low pressures crossing the UK in particular the northern portions which feed into the Scandinavian trough developments, Troughing and aforementioned colder conditions into Asia > East Asia, High pressure / block across the East > Northeast of America and the Maritimes with further above average temperatures no surprises from my POV on that. Continuing trough and noteable cold across Alaska too.

 

Looking to the 2nd and latter half of February with the MJO currently being in a phase 7 for the last days of January This gives the following feedback 

I'm really liking the CFS for this period already matching really great.

January phase 7 does give a window for colder conditions from the Northeast perhaps Easterly at times.

Moving forward a February phase 7 sees feedback bringing high pressure development to our East Northeast and extending across the UK

Both of these setups can be seen in the below

With the supportive precursors and MJO the stratospheric warming did indeed begin in small amounts during week 4 of January and as the MJO influence within the Pacific takes place the warming increases during the first half of February 

Prime time showcase of El Ninò in February 

We might have a brief re entry of phase 6 during week 1 of February though there is no complete agreement for this, however it's relatively similar to the setups currently materialising should it occur.

We'll continue seeing patterns which link to El Ninò throughout March and I'd favour potentially the first few weeks or so of April, following that time it's a gradual move into ENSO Neutral with some themes continuing of heading into La Ninà by late spring and particularly Summer 2024.

As 2012>2013 is among my top analogues it wouldn't be shocking for relatively similar setups to occur should MJO progression be conducive and potential feedback of stratospheric events.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5026092

[Met4Cast]

The MJO has moved into the western Pacific and this eastward progression over the past couple of weeks has resulted in a strong rise in total AAM following the recent very strong +MT events. The impact of the +EAMT event in particular has led to another strong Pacific jet extension eastwards (warm USA signal and down stream propagating Rossby waves) Cyclonic wave breaking in the western Atlantic may help to amplify heights northwards towards Greenland but modelling this is extremely complex, some runs manage it but many don't. Quite a complex setup as per usual.

This surge of momentum into the atmosphere should begin to reshuffle weather patterns somewhat into February. On balance for the UK - I'd expect the persistent Iberian heights to begin weakening into the 2nd week of February with the possibility of weak heights developing to the north/north west allowing for the risk of colder weather & increasing snow risks, particularly in the north, things are less clear cut further south but NWP modelling is signalling a cooling trend across the board in any case.

I'm not currently seeing anything to suggest prolonged deep cold or widespread significant snowfall within NWP modelling or otherwise, but certainly an increasing risk of colder weather as we go through February (more primarily week 2 into 3)

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5026437

[Mike Poole]

 Northern Sky Hi, yes, I think I do.  The ECM T240 leaves a good space open after the low clears the UK east for a ridge to build towards south Greenland, while the CAA on the lee side of the low establishes the Euro trough.  The fact that it is supported by 32 of the EPS is worth noting, and also it is consistent with MJO phase 7-8, with some lag.

One thing I’ve been watching lately is how the MJO is behaving compared to how it’s modelled.  Here’s the ECM 46 take today:

Now here’s the same plot yesterday, looking at phase 7:

The grey square is where it was yesterday, the cloud of red dots are the 1 day forecast from all 100 ensemble members yesterday, I’ve put a gold star roughly where the actual data from today’s plot goes - none of the members are near it!  And that’s day 1 - the models don’t seem very good at predicting this measure of the MJO at all, and on this occasion, it has consistently verified at higher amplitude through phase 7 than modelled.  This may mean that as we are now in the key MJO phases 7-8, the models may increase the signal for blocking as they get to grips with their own error on the MJO, and that might also bring the pattern change a little earlier.  But all looking very interesting from 10 Feb onwards, I would say.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5027140