Model discussion highlights

[Eagle Eye]

5 minutes ago, minus10 said:

Sorry Eagle Eye but i think you have kinda lost me... your knowledge on the higher atmosphere is fantastic and i am learning stuff but some of it is just over my head...perhaps i should do more reading of it if i had the time ....but is there a simpler definition of barotrophic / baroclinic as looking these up still leaves me confused....probable says more about me...er..

 

Just now, MJB said:

Eagle Eye 

 

Brilliant knowledge , not that i would know if it really means anything as BS can baffle - but is there any chance you can but it in simpler terms for the idiot in me 

 

Cheers 

 

M

As basically as I can put it.

Baratropic flow has the temperature following the pressure roughly.

Baroclinic flow has the temperature at a roughly 45° angle to the pressure. 

The reason I say roughly here is that it's not the full case as you are very unlikely to find a perfect system for both due to little disturbances along the way.

As we have been aware over the past Winters there's the horrible zonal flow is the typical form horse of Winter. That's a Baratropic flow and so we don't really want something to be Baratropic I'd its cold we're after. 

A Barolonic flow is where you get the mid-high latitude blocks that can help bring cold to us. They're good but of course depends where they occur.

I'd say that's more relative fluid flow as the blocks are still Baratropically flowing but relative to normal would be Baroclinically flowing.

A more 'absolute' flow for either would be the Strat example.  The changes in temperature are less constant with the height and isobars as far as I can remember. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801463

[snowking]

Always worth remembering when monitoring the stratosphere that temperature is just one element of what we're looking to shift.

When looking at heights too:

Not quite obliterated, but a huge Wave 1 pushes the vortex off of it's usual axis across to the Siberian sector and gives it a very good stretching too.

Battered and bruised at this stage, and we can also see from looking at the wind charts that a technical SSW has taken place (and a pretty significant one at that):

All in all very good signs again - vortex moved completely off-axis in a useful direction at 10mb at least and zonal wind speeds significantly reduced (and in fact here reversed).

 

However as always trying to figure out how this translates to conditions in the troposphere is a fun game for the coming weeks.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801502

[Rain All Night]

ChatGPT is good for this sort of thing...

 

Can you give me a simple explanation of baroclinic and barotropic?

Baroclinic and barotropic are two types of atmospheric or oceanic flow patterns.

Baroclinic flow refers to a type of flow in which temperature and pressure are not in balance, leading to strong horizontal and vertical variations in fluid density. This type of flow can result in the development of cyclones and fronts.

Barotropic flow, on the other hand, refers to a type of flow in which temperature and pressure are in balance, resulting in a uniform fluid density. In this case, the flow is characterized by simple and straight streamlines with no significant vertical motion.

In short, baroclinic flow is characterized by strong density gradients, whereas barotropic flow is characterized by uniform density.

Can you make it even simpler than that?

Sure! Simply put, baroclinic and barotropic describe how different the temperature and pressure is in a moving fluid, like air or water.

In a baroclinic fluid, temperature and pressure are not the same throughout, creating changes in density and leading to more complex and dynamic flow patterns.

In a barotropic fluid, temperature and pressure are uniform, leading to more straightforward flow patterns with no significant changes in density.

Can you make it even simpler still?

Sure, I'll try to simplify it even more!

Baroclinic and barotropic are terms used to describe the flow of a fluid, like air or water.

Baroclinic flow is when the fluid is moving in a way that the temperature and pressure are different, making the flow more complex and changing.

Barotropic flow is when the fluid is moving in a way that the temperature and pressure are the same, making the flow simpler and not changing much.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801460

[Mike Poole]

When a potential SSW is showing, a game I sometimes play is to look at the pressure evolution of the first half of a GFS run, and then guess whether the strat warming will be stronger or weaker in the day 8-16 period.  And I am absolutely rubbish at it!  I thought the 12z would be a stronger warming than the 6z, but actually it isn’t.  It’s good enough to do the job though, with a technical SSW at T264.  

I’ve noted before that the precursor patterns for a SSW are complicated, and the main one we look for is the Ural high Aleutian low combination, which has come back into contention after a week or so’s absence.  My understanding is that this, in and of itself, would lead to only a displacement SSW, not a split, with other patterns also required for the latter.  

There seems increasing evidence now for a SSW around 14th February.  And this one looks as though it could be a proper reversal with zonal winds dipping well below zero, with op and ensemble support:

I can see the obstacles to UK cold being removed one by one in the coming weeks.  The strong trop vortex, maybe aided by the flushing down of westerlies from the previous minor warming, should lose its grip.  The recent ‘failed easterly’ also tells us something - GFS would not have shown the scenario it did if it was completely outrageous, so the atmosphere could be primed for a proper scandi high later.  All the attention has been on the GFS miss, but now it did miss, actually for me the more significant story was how much the UKMO was wrong in predicting a return of the Atlantic on the same timescale - this failed massively!  

If this SSW does occur, in more or less the way shown in the current modelling, the trop response should be pushing at a partially open door to establish a favourable block this time, and an easterly before the end of winter is now a distinct possibility, in my view.  Which may well last into March - a month which, like it or not, seems to offer a greater chance of snow these days than any of the winter months.  

One more push - let’s chase this one down!

All the best.

Mike

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801519

[bluearmy]

Eps mean is just reversed (tech ssw) between T336 and T354 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801580

[bluearmy]

46 minutes ago, Premier Neige said:

At what point will we know if there is going to be a QTR, if it's possible to say?  (Assuming an SSW actually comes off)

Just have to watch the runs and see what they are showing - if it looks like it’s happening then you’ll notice it on the NH charts - around 21st onwards   Im amending that to be earlier depending on whether the run shows a strong reversal - in the 10/15 day period. Imo,  the stronger and more sudden the reversal, the more likely it will head down into the trop. 

the other signature of a QTR (or downwelling wave) is for the blues and purples to unexpectedly drain from the NH charts. in the past we’ve seen both a n pacific ridge punch across the hemisphere and on other occasions the sudden draining of low heights across the polar field allowing HLB to establish ….

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801581

[Blessed Weather]

33 minutes ago, Ali1977 said:

Does anyone know if the GEFS mean still had a SSW? Hoping not to lose that signal 

From what I can see the GEFS mean hasn't been showing a reversal of zonal mean winds at 10hPa (i.e. a technical SSW) over the last few days. But what is interesting is that when comparing the 0Z run over the period, the mean has been getting closer to a SSW with every run. This morning getting very, very close. Weatheriscool estimate the chances of a SSW now 48%.

Quite a few ensemble members (green) going for a reversal:

Source: http://weatheriscool.com/

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801697

[Cambrian]

Next few days a chilly anticyclone provides a comfortable early February place to sit back and await the further ramifications of changes in stratospheric wellness. In the meantime, there’s already a great deal going on in the troposphere, as shown in the 0z ECM ensemble mean charts. 

At the moment, we have our high, building in beautifully from the southwest, handsome looking thing by day 2, though never quite gets far enough north to make it really exciting, some reasonable frosts for many. The vast bulk of the tropospheric PV at that stage is centred with vivid strength Baffin way, from northeast Canada, extending to cover much of Greenland. No real vortex at all over western Siberia, or for, - hey (American nature documentary narrator voice, you know the guy) look at this cute little critter, he’s a Svalbard reindeer, called Isak. 

   

It’s only a temporary reprieve for Isak, though, as by day 4, the PV is on the move, through Svalbard, extending into the Barents Sea. It’s this move that helps to put the southeastward squeeze on our high, the eastward transfer of the PV complete by day 6. 

By day 8, the real power of the PV is very much on the Siberian side, linking through to Isak. For us at this stage, little has happened. The Atlantic trough remains south of Greenland, with a gentle western European maritimes feed into the UK and Ireland. Still anticyclonic,  largely dry, chilly nights, close to average overall. 

  

By day 10, we get a truer westerly feed, but this is only transitional, as by day 12, there’s a very definite movement east of the trough, some build of heights north from the mid Atlantic towards Greenland, so a smart reversal of the amplification profile, with low pressure sitting between Iceland and Scotland, heights much lower by then for the UK and Ireland.  That’s a fairly cold looking feed for us from the northwest, but originating from much further up north, close to you know who! Plenty of scope for cold trough developments by then, systems easily able to wrap in cold air from the Arctic, the mean wind direction steadily working around the dial to the north.

The Siberian PV is still very much in the driving seat, and the Atlantic by then is returning to even fuller quiescence, so if we get the trough to transfer fully east into Scandinavia just as we realise the effects of any wellings, splits, displacements, obliterations, etc., then things might well already be aligned very favourably for a quick transition to a much colder pattern, that won’t be getting shifted away any time fast. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801754

[Blessed Weather]

1 hour ago, Vikos said:

Was 61% yesterday…

Yes, despite today's GEFS mean edging marginally closer to a reversal than yesterday's mean. I'm guessing, but I wonder if the reason is because the 'mean' is basically an 'average' of all members zonal wind speed, whilst the % chance of a SSW is simply calculated by how 'many' members show a reversal? So yesterday 21 members went for a reversal, today 15 members, but today's 15 are going for a more significant reversal?

If anyone from weatheriscool is reading this, an insight into how the % chance is calculated would be gratefully received.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4801702

[Nick F]

Let's hope GFS/GEFS is more reliable up in the stratosphere than the troposphere, it should be, as you'd expect longer predictability from models for the stratosphere compared to the troposphere. Quite a robust reversal downwelling on the 00z GFS, though we still aren't seeing a split.

 

GFS has been very poor with handling the trop recently. Following it's phantom deep cold easterly it was hanging on to for a few days when the other models weren't interested, after it eventually backed away from a Scandi high it was still modelling the high too far north next week and trying to bring colder uppers towards southern UK from central Europe, again EC and UKMO weren't interested. Anticyclonic with average day time temps and frosty nights.

Fairly reasonable continuity for an Atlantic trough close to the UK with a cyclonic flow by day 10 in the EPS and GEFS means:

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802002

[Nick F]

Very high atmospheric pressure at the surface this morning, 1048 hPa over Wales, very likely linked to the intense trop PV dropping over the far NW Atlantic that is bringing very cold air to NE USA / eastern Canada atm and causing strong WAA aloft downstream.

Highest pressure for February in the UK, appears to be 1052.9 hPa recorded at Aberdeen on 1st Feb 1902. Probably be some individual weather station records being broken today, particularly Wales and parts of the southwest. 

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802020

[bluearmy]

56 minutes ago, Met4Cast said:

It’s worth emphasising that an SSW does not guarantee UK cold weather, especially displacement events. Split events are more reliable. 

Another potential factor is the disconnect between the strat & trop. It’s plausible that an SSW fails to downwell & impact the surface levels, this is more likely when there is such a stark disconnect as we’re seeing forecast at the moment. 2019 is a good example of this, the UK ended up with above average temperatures following that SSW. A warm March that year!

 

A displacement event seems most likely based on the GEFS/EPS and a quick trop response looks unlikely based on the current configuration of the atmosphere. 

So.. end of Feb/early March at the earliest, if we even see impacts from any potential SSW. 

It’s not the magical path to certain cold many seem to believe it to be. 

The eps mean has lost an ssw on the 00z run 

The spv tracks east into n Russia at too high a latitude because the Canadian ridge doesn’t exert enough pressure.  not worth taking much from one run but the momentum is broken on the eps and note that the gefs haven’t yet shown a mean reversal. 

will the decimation of the zonal flow late feb be enough if trop telecons dicate ??

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802061

[Tamara]

1 hour ago, Met4Cast said:

It’s worth emphasising that an SSW does not guarantee UK cold weather, especially displacement events. Split events are more reliable. 

Another potential factor is the disconnect between the strat & trop. It’s plausible that an SSW fails to downwell & impact the surface levels, this is more likely when there is such a stark disconnect as we’re seeing forecast at the moment. 2019 is a good example of this, the UK ended up with above average temperatures following that SSW. A warm March that year!

 

A displacement event seems most likely based on the GEFS/EPS and a quick trop response looks unlikely based on the current configuration of the atmosphere. 

So.. end of Feb/early March at the earliest, if we even see impacts from any potential SSW. 

It’s not the magical path to certain cold many seem to believe it to be. 

I live in Portugal, and am therefore detached from the interest in this thread, but you are correct in respect of the over "magic bullet" association to cold weather with SSW's. As interesting a phenomenon they are in themselves, the associated cold weather hype rather detracts from that appreciation. Similarly with the MJO - this is not the stand alone phenomenon it is treated as in this thread and equally as such not a magic bullet to cold weather preferences. It is just one part of the atmospheric circulation total wind-flow budget, and while clearly an important catalyst for changes in weather pattern, it has to be taken in association with the rest of the wind-flow budget which comprises the extra-tropics. The relationship between the tropical & extra tropical wind-flow circulation does not work on a linear x+y = equation (in the same way as the troposphere and stratosphere can have both a connected & equally often quite disconnected relationship). With this in mind the frequent use of MJO composites on this thread is not going to lead to accuracy, especially when attempted to be fitted to weather bias patterns, without considering the extra-tropical Global Wind Oscillation (GWO). The GWO incorporates analysis of the total circulation budget and gives analysis of each flux and torque component within the total atmospheric circulation and is therefore a much more accurate guide. That is, again, if one is willing to suspend skewing.such a diagnostic to try to fit to a desired outcome. This will also lead to inevitable error (and disappointment)

So to put some of this background rationale into practice:

The GWO, a plot depiction of total wind-flow, is firmly in a -ve inertia state taking both the tropics and extra tropics as a whole.

 

A disconnect is evident between both components - with westerly wind additions (orange shaded) in the tropics across the Indian ocean as measured by inflection of wind-flow frictional torque at the same time as being over compensated by anomalous -ve inertia across mid latitudes and a large vacuum evident as a result of this c/o -ve mountain torques across both Americas.

This vacuum, in order to be filled, has been driving an extended period of mid latitude retrogressive sequences of anticyclonic wave breaking (blue shading on MT plots) and hence the sustained elongated blocked pattern across the mid hemisphere. At the same time the polar jet is energised across the northern perimeter of these blocking structures in association with added assistance of downwelling of +ve zonal winds from the stratosphere into the tropospheric boundary layers.

The MJO tropical component continues to operate at amplitude (in accordance with a prediction of recurrence periodicity cycle made back in early December).  The complex relationship this winter between the stratosphere & troposphere makes it problematic ascertaining how eastward movement of amplitude tropical convection through the tropics propagates into the extra tropics and then how directional flux of AAM anomalies routes the amplifying wind eddies either poleward in association with weakening stratospheric vortex, or continued equatorward ( as in Feb 2019 following vortex destabilisation)

Rising AAM under equatorward flux would give rise to anomalous blocking structures across mainland Europe set against a highly amplified recurving jet stream around a deep upper trough in the Atlantic. In such a situation continued disconnect between the troposphere (equatorward flux) and an unstable stratosphere would lead to the negating of potential outcomes of cold air advection.  The Hadley/ferrel cell fuelling a strong +ve NAO signature disconnect to a likely displaced -ve AO vortex, as mused about in the post under response.

At present, it is still early in February of course,  I agree that there is no real evidence to suggest that a poleward stratospheric pathway to work in tandem with a weakened vortex will inevitably occur & give the QTR that the UK members of this thread hope for to fulfill cold weather & snow aspirations..

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802091

[Cambrian]

A high flyer 1048.8 mb on my Davis rig here at 11.33am, -2.3 degrees overnight, beautiful crisp morning but surprisingly hazy, quite a lot of high cloud. However, the pressure is very likely to fall away sustainedly from now through to mid month, as on the 0z ECM ensemble mean - the op and control even keener on a change to cyclonic weather, with a quite different feel possible by then. 

To be sure, the 0z ECM and GEM ops are going a bit Rollerball Rocco with the low to our north at day 10, a bit early to say whether it will be full-on maniac, but either way, probably the best chance of getting some colder uppers in around mid month, as all the cold air has been removed from Europe by then - mild from the Mediterranean to the Baltic. 

   

The GFS not on board with this so far today, but had similar for day 11 on its 12z run yesterday, and the development of low pressure to the north of Scotland enjoys good support from the ensemble means, like from the 0z ECM here, for day 10. 

 

I quite like the ECM development in particular, as shown in the op and mean anomalies…

 

as the deeper low cleanly punches through the heights to the south, between us and Portugal, keeps the Azores high further west, forcing heights northwest, leaving us open to those colder digs from Greenland. 

Indeed, there’s some generally good looking trends for a build of heights just off the Canadian seaboard up towards southwest Greenland, which with the Pacific not being so sure of itself, might be all the help we need in pulling us round into a truer northerly in time. The cross-polar trough is aligned nicely, and could deliver a cheeky little cold spell just after mid month if sufficient heights can move up the western side of Greenland and keep the Canadian lobe of the PV mollified. With the jet stream continuing to be restrained in that long hold, only slow manoeuvring going on, winter is far from being on the ropes and there could still be a lot worth wrestling with as we move on through February. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802071

[Mike Poole]

21 minutes ago, bluearmy said:

Gfs op shows what the fall out could be be reversal with flow in the lower strat and trop. No westerly momentum left to push down into the last third of feb  

Today                                                             Day 16 

      

Yes, that’s very clear, whether the trop plays ball after that, we will have to wait and see.  71% of 6z GEFS go for a SSW - and, notably, all the (higher resolution) op runs have had a reversal for some runs now, so hopeful that this time it will actually occur.  Best not to count chickens yet though!

2 hours ago, Met4Cast said:

So.. end of Feb/early March at the earliest, if we even see impacts from any potential SSW. 

It’s not the magical path to certain cold many seem to believe it to be. 

You make this point, or one similar, often.  I see no evidence that anyone on this forum regards a SSW as a magical path to certain cold!  I’d go further and say there are no magical paths to certain cold for the UK.  What we can say is that a SSW does shuffle the pack, with a few extra aces in there - after that, it is luck of the draw.  But - usually - that by itself gives us a greater chance of a cold evolution than the status quo, which as we know for the UK is often dire for cold chances.  

Agree last week in Feb is the earliest we would see impacts, though.  

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802098

[bluearmy]

Gfs op shows what the fall out could be be reversal with flow in the lower strat and trop. No westerly momentum left to push down into the last third of feb  

Today                                                             Day 16 

      

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802084

[bluearmy]

1 hour ago, Mike Poole said:

12z GEFS has SSW percent = 90%.

So I think we’re nearly home and hosed with a technical SSW around 15/2/23.  

What happens next, as you say, is to be decided.  Look out for interesting trop patterns in the last week of Feb.  

Second consecutive eps run with no mean ssw after three runs with one. Infact I’d say the three runs that had ssw were more marginally negative than the two runs today have been positive. Not a great deal in it but those assuming that we are certain of a tech ssw should be aware of the eps trend.  But we are seeing a displaced spv into Asia with a mean signature not far from the gfs op. (Of course without the reversal).  Looking at this hemispheric pattern, I’m not convinced that we need a tech ssw if we lose the westerlies. Even without a tech ssw, we will see the atmosphere north of 70 reversing and as long as we lose that stronger zonal flow in the trop above 55N, the Asian trough/Canadian ridge set up is surely positive for cold if Imprinted below. 
 

     

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802270

[bluearmy]

as per the 18z, the 00z also downwells the weaker zonal flow towards the trop at 10hpa - remember, this is the gfs op out to day 16 so expecting it to have the detail correct as the run goes on, especially lower down in the strat is unlikely (although NH zonal flow is not the same as detailed heights ) 

the point is that for two runs we have more of an impending connect with a weaker strat heading down 
 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802368

[bluearmy]

10 minutes ago, Mike Poole said:

That 52% was the 18z.  Must admit, i thought it had gone west!  Back to 84% on GEFS on the 0z.

And a much stronger warming with a split on the 0z op, with reversal at T240 - at this point we’d be reaching for the Berlin site to see what the ECM op is showing, but sadly it’s not available this year.  (It’s a bit shaky trusting the ensembles of either model due to lower resolution.)

The reversal on gfs mean is short lived but likely hides a multitude of solutions - hopefully someone will post them all on the single chart (but even that doesn’t allow for timings.) 

id say that we are currently looking at a short lived tech reversal (as part of a fairly significant wider upper strat reversal ). The spv then recovering back towards the pole in western Siberia but still displaced. this leaves is with a cross polar strat ridge into the Atlantic.  If we can imprint that down through atmosphere into the trop, then with the lower strat westerlies flushed away, late feb and into march offers the best chance of winter since mid dec. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802393

[MattH]

Morning.

Quick post but, overall, still nothing has changed looking ahead, both short-term and long-term and those hoping for late winter weather may still have to pin their hopes on the final third of February or, most probably, March.

We have fallen into the late winter trap of dominant -ve AAM anomalies through the sub-tropics, being propped up by constant WAA over the North Atlantic as the dominant trop PV remains a force to the NW, where it often sits through the late winter, as mentioned a while back any sort of Scandinavian block was never going to happen and, for now, the dominant outlook, as clearly shown by many on here already, is for a sub-tropical/mid-latitude high pressure system to remain influential over W-NW Europe and this won't move very far. The overall AAM profile highlights this pattern quite well, with plenty of -ve AAM anomalies flooding the sub-tropics, note as well the ECM dynamic trop plots, constantly showing a series of anticyclonic wave breaks which will do nothing but simply reinforce the block that many want nearer 60-70N.

The MJO is now on the move and is likely, at a minimum to progress through phases 4 and 5, most probably 6 as well. If your looking for a potential forcing or something to at least mix things up a bit then this may help the cause, but not for at least another 7 to 14 days, which clearly takes us past mid-February. Some of the composite anomalies of the MJO through phases 4-5-6 do bring northern blocking but, as ever, it is never A+B=C and other factors, especially the current dominant tPV may well have some say in this.

The increasingly strong signal for a potential early final warming or a very late winter SSW is gaining traction but, once again this is most certainly not going to immediately deliver synoptics to bring late winter weather any time soon, if at all, especially if it is another displacement event. There is, however, some science behind the risk of synoptics appearing in March that many would have wanted in January and February, how many times have we seen that happen before, especially as seasonal wavelength changes start to come into play as well.

Obviously one could argue the seasonal models have called the late winter pattern correct. There is clearly a connection between a more dominant +ve NAO regime through later winter within a La Nina state and, overall, that has come to fruition, not to the extent it could have, given the blocking pattern over 30-40N currently and lookig ahead, but the winter is likely to fizzle out, overall, IMO. Clearly, winter weather and synoptics can extend beyond February and that clearly does remain a possibility, especially through March, but by then you need some 'proper' synoptics for any significant cold weather and those kind of synoptics can simply delay the onset of spring for many.

Cheers, Matt.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802440

[Eagle Eye]

The meridional circulation tropopause leans towards a very strong Baroclinic instable pattern in the UK-Scandi region. That's good for the formation of horizontal and vertical Eddy's and heat flux perturbation . A very good Strat warmth driver is the Scandi high and though it's not perfect it looks decent here.

Also note that it appears to end up as an Arctic -Scandi/Ural dipole and you can see the smaller trapped Eddy in the charts above that appears to have possibly ended up as that small Wave-2 driver here. If so it's a good sign of potentially more background signals for a split. This is looking like a very good fluidity of a sign in my opinion. 

 

Though for a SSW to reach the Trop quickly there needs to be a decent amount of upwards wave flux at that time and according to the GFS that just doesn't seem to be the case but I wouldn't worry over it too much yet.

Perhaps I'll go more in-depth about tropopause-Strat fluid circulation another time but I'm too tired right now.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802497

[Cloud 10]

Random spot check on "how the models did"from 7 days ago...

 

Today's chart,then GFS,GEM,UKMO and ECM from this time last week.

 

 

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802649

[johnholmes]

Monday 6 Feb

The Noaa ouput from last evening shows a mobile atlantic flow across the atlantic giving a s of w flow into the uk with only the slightest sign of any ridging over n’ern Europe. So probably becoming more unsettled for many n and w’er n areas but fairly settled and less cold than now for se’ern parts of the uk.

Alongside is the 00z 500 mb chart, so at height, the 6-10 day outputs from around 30 th were close to what we have. The issue at the surface was always in doubt even trying to give a =ve view from a cold perspective. Teach me to be totally objective in future-slapped wrists!

please see 500 mb chart on Extra

What happens beyond 6-10 or 8-14 is for others to wrestle with.

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802410

[Catacol]

6 hours ago, Ali1977 said:

Well, we have an upgrade of sorts  on the METO long range , with a small but increasing chance of some colder conditions Sounds like the reversal is on, obviously this is just highlighting the chance of it effecting us of course. 

 

Best news all day , hoping something kicks in earlier than expected though as beyond the second week of March becomes harder for “big freeze” type set ups,  and even I’ll be ready for some warmth by mid March!! 
 

What’s the quickest we could hope for some implications if the reversal happens 14-17 Feb? In February still? If things fall right? Will the MJO heading through 4/5/6 help, even an a pretty low amplitude? 

It will be time to reengage with winter forecasting again soon as the current very predictable westerly pattern comes under pressure. We need MJO into 6/7/8 and the CPC today stated this:

"Dynamical models indicate a quick resumption of an eastward propagating MJO into the Western Pacific later this week."

So....MJO heading into 6 by Valentine's Day. Cue forcing for favourable blocking reemerging around 10 days later - so last week of Feb. And meanwhile the vortex is getting hammered far harder than looked likely a fortnight ago. Love this (hopelessly inaccurate because it is GFS extended) vortex 3D. Inaccurate - but kind of shows how a stressed vortex looks as it loses coherence

and this also - happy days.

Now..... let's be clear. This is very much a case of crumbs from the table stuff. Pot of Gold hunters have to accept that cold weather in the back end of Feb into March is not the ideal landing zone and the vortex is not predisposed to a split as it was in 2018. But it does at least add interest to what otherwise was beginning to look like a horribly dull month. Can we have a stab at how this particular displaced event might impact? Well - let's have a go. 10hpa extended here:

All data is leaning towards a substantial displacement event pushing the vortex over towards Russia. Layers beneath then follow as the impact downwells, with the time series average anomalies showing the beginning of what might occur as we move towards the end of the month

Given the parallel impacts of the MJO and a vortex being shunted to Russia I am going to punt for a cold block due north of the UK to form in that last week, with the possibility as we move into March of a cold NE feed. Last hurrah for winter....and a chance that it might be a good end. Note again that we are not looking at a 2018 split where we had a vortex shard back east to west, pulling in that amazing feed and climaxing with Storm Emma. Not this time. No split. But some snow in this final winter phase quite possible. March to me looks like a below average month.

 

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802781

[bluearmy]

29 minutes ago, nick sussex said:

Latest GEFS 0hrs mean doesn’t have a reversal . 

So yet more disappointment to add to the very poor output for coldies .

Eps mean still does between T224 and T278 

the current agreed trend is a displacement with a lowish level reversal at 60N.  Still no continuity on gfs op on how that might head down.  Eps at day15 don’t show much appetite for a trop repsonse. The Canadian tpv looks particularly strong out to day 16 on the ens. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802936