[Model Output Discussions 06z 04/11/16]

On 11/21/2016 at 14:55, Summer Sun said:

@OldMetMan is still around he last visited on Thursday

https://www.netweather.tv/forum/profile/13989-oldmetman/

Yes I'm still here, just too busy with work and the like. I appreciate the kind comments though, thank you all.

This autumn/early winter looks so different compared to recent years, I am impressed by the significant temperature fluctuations up in the stratosphere, not to mention the relative weakness of the Atlantic systems coming our way (apart from Storm Angus of course). I note that quite regularly in runs over the last week or two the GFS has shown a real wintry setup in the longer term, with the jet travelling way south. 

There's quite an arctic plunge heading into W Europe in the next few days, bit too far E for our purposes but if HP stays anchored close to us and LP going over the top, further incursions of cold air seem likely very near to us. I'm looking for signs of cold air pooling over Europe in the coming days. There has already been very intense HP last week in Russia (near to 1070mb) so if the cold air gets a real chance to settle over Europe, I think it would only be a matter of time before it spreads our way.

I've a feeling in my old bones that the weather might make headlines this winter and not from rain, wind and floods as has happened so much in recent years, but "The Big Freeze" type story. I think a really cold winter is well overdue (the last one that I think qualifies as that was 1978/79). I've even beefed up my home heating in preparation! 

If I see anything I think looks promising in the coming days, I'll be back!

 

[Model output discussion pm 13/01/2016]

Audaxian, FI stands for "Fantasy Island". The further out the model predictions are, the more they go off into the realm of fantasy!

[Model output discussion pm 13/01/2016]

I felt I had to comment on developments in model output this morning, even though they are tentative and a long way off yet.

There has already been some back-tracking on the forecast return of the Atlantic systems over several days, but what I have been watching with interest is the large HP off N Russia and towards the Pole. In spite of the models trying to kill it off, it's still there. In fact, the GEM is creating a new scenario this morning involving linking it to developing HP over W and NW Europe, with a significant easterly developing.

 

Actually, it bears some striking similarities to what happened in January 1947!

I can't help but think there is still too much ambivalence over the usual return to the SW flow from the models. I think we need to watch how the upper flow develops in the next few days as this could be crucial in deciding how the longer term will pan out. A big sturdy ridge extending NE, as portrayed by the GEM might seem too much to hope for but as I see things setting themselves up at present, I think it remains a distinct possibility.

 

 

[Model output discussion pm 13/01/2016]

Interesting variations in the model output over several days, basically will the Atlantic systems return once again, which has been the consensus today certainly. But I have been looking at both the upper pattern and surface features with strong HP in polar regions, stretching across the Arctic to N Canada, as well as in mid-Atlantic. Looking at this particular pattern reminds of a number of other occasions where pressure builds SE from Greenland and fends off frontal approaches from the SW.

 

 

There is quite a substantial cold pool developing over W Europe and Scandinavia. The models are sweeping this away far too easily I think, and I expect at least one trough disruption over the SW and subsequent LP activity and the jet taking a more SE path. If this happens, cold air will continue to filter S across Scandinavia strengthening the cold pool.

The appearance of a hurricane in the Azores area is remarkable in January. It may have an impact on Atlantic developments and serve to reinforce the upper low over the W Atlantic and strengthen the mid-Atlantic ridging. 

Over the hemisphere as a whole, there much more of a meridional look to it. I wouldn't be surprised to see the cold air getting more firmly entrenched over the UK with the threat of snow from stalling frontal zones. 

 

 

 

 

[Model output discussion - 1st December onwards]

Hi everyone, I hope you all enjoyed your Christmas.

I have been watching the models well struggle basically, with the developing HP over Scandinavia, coming up with a variety of solutions. It seems pretty likely that the HP will develop, although it is a bit far E, as is the associated upper high, from the point of view of the UK. Given the remarkable persistence of the S to SW flow and the resulting insanely high temperatures we've been getting for the best part of the last 2 months (I have had EIGHT days this month with temps over 15C), I cannot see how this can last much longer, without the upper pattern somehow shifting, most likely retrogressing. The first appearance of really cold air over E Europe has got to mean a change in pattern as I see it.

There is still too much energy in the Atlantic systems I think for anything immediate to happen, but if as I suggested above, should the pattern shifts W, and should the upper high take up position to our N, then we may at last have an opportunity for something more seasonal to spread from the Continent, 

I like the look of the significant upper trough now across the US, and still amplifying it seems. It might encourage similar amplitudes downstream. But again, the positioning of the upper pattern will be crucial.

Let's see how the HP holds its ground against the vigorous Atlantic onslaughts over the coming days. Winter may at last arrive!

[Model output discussion - 1st December onwards]

Hello everyone. I thought it about time I chimed in for the first time this winter. Having gone on and on about a cold spell that never happened last winter, I shall be more cautious in my comments this time around!

I have found this autumn and winter's warmth quite remarkable, and cannot recall anything quite like it in my lengthy weather memory. I've been following model output quite closely these last few weeks, as the relentless Atlantic domination continued, but something caught my eye a couple of days ago when the GFS, out of nowhere, decided to treat us to building pressure from Greenland SE, halting the Atlantic systems completely, and streaming very cold air southwards. This development was gone in subsequent runs but there are still hints of it even now:

There has been signs of a new trend with model output dithering rather over developments from this weekend onwards. I can't shake the feeling that the GFS had picked up an early trend. 

There isn't much else to support such a change at the moment. The PV is strong, remarkably low temps of -85C at 30MB, way below normal. It seems unlikely that it could go still lower and there has been much speculation on the possibility of a SSW this month. So maybe January will see something very different.

As I said, I kept saying that last winter so don't hold your breath! But after SO much warmth and SO much rain, the pendulum will have to swing the other way - eventually!

[Model Output Discussion - 14th Jan 12z Onwards]

I've been keeping my head down for a while, with no sign of any "proper" cold showing in the models, by that I mean, a N, NE or E flow. But recent runs of both the GFS and ECM keeping showing variations on an easterly flow, so as I see it now, the prospects look more encouraging than they really have all winter.

 

The shape of the 500mb flow seems to be slowly shifting, with that small polar upper high re-appearing for the first time in a while, plus the amplifying upper trough over and to the W of us.

 

 

What's been lacking for much of the winter has been HP in higher latitudes, close enough to us to send an offshoot our way, but instead what seemed like an endless succession of LPs travelling within the Arctic circle. So too over Greenland, where there has also been little chance for cold air to get entrenched and thus for HP to strengthen. But latest runs have continued a trend of showing HP finally putting in an appearance, either over Greenland or off the NE.

 

The problem in the near term is how far east the Atlantic systems will come, will the air ahead be cold enough anyway for any snow, or will it just degenerate into a flabby cyclonic mess, swilling around for a few days before the progression kicks in again! I do think we are about due a Scandinavian HP or something like if the energy goes out of the westerlies for a while. It certainly looks more likely than previous model promises of this which failed to materialise.

 

In any event, I think we will be under the influence of a cold pool (thickness values at or below 528dm) for a while, so there is the promise of snow for some of us. Until such time as the upper pattern stops progressing and settles into a more static pattern, I think we will have to accept short term cold for now.

 

Although the weather has proved me wrong so far this winter, I still feel a more pronounced cold spell will happen this winter.

 

 

[Stratosphere Temperature Watch 2014/2015]

I wonder if someone could explain something to me, with my very limited understanding of the mechanism of the SSW process?

 

I have noted that the temperature at 1MB has been 35C for 6 days straight, in spite of the ECM forecast dropping it back to less tropical levels every day. Surely temperatures of this magnitude mean something significant? I haven't been studying such charts for very long but I am intrigued by the persistence of such high temperatures. I note also that there have been rises further down in the atmosphere.

 

Is there some kind of tipping point where sustained high temperatures at the top of the stratosphere suddenly propagate downwards and destroy the polar vortex? Or is that the $64000 question every time in these conditions, not knowing if the warming is sufficient to cause such destruction?

 

I find this area fascinating and I realise there is not an exact correlation to events further down in the troposphere, but any explanation would be very welcome!

 

Thanks, OMM

[Model Banter, Moans and Ramps Autumn/Winter 2014/15.]

I don't post here normally but it seems like a good time to add a bit of perspective to the current disappointed view of this winter so far as it's very early days.

 

I first became hooked on the weather in 1967 when I was still at school and have been an addict since. I have witnessed some spectacular weather events and even in my advanced years, I find the weather interests me more than anything else.

 

I loved the snow when I was younger, not so much now as it's harder for me to keep the cold out, but I love to watch cold situations developing (such as the remarkable December 2010) and I am constantly on the lookout for any sign. Apart from 1962/63, every winter with significant cold weather that I remember happened after December was over. Indeed, the coldest spells in my youth were always in February. So, for those who are writing winter off, there is tons of time for things to change.

 

I was thinking today about the current long wave configuration around the hemisphere, with several high-amplitude waves, and that what we have here, a big, fat 500mb ridge over and to the west, in different circumstances would see us benefiting from a surface HP to the N and NE, with bitter east winds. But this is not so and it looks decidedly odd to me that we apparently are about to launch straight into a very unsettled progressive flow from this situation. Why is this long wave pattern collapsing so quickly and easily? That remains to be seen.

 

Having the benefit of a long weather memory, as well as noting when snow used to occur, I can also recall many winters in which snow was virtually absent and living as I did on the south coast, I accepted that this was a feature of my location, with the relatively warm sea close by. Yet in my younger days, I never imagined that global warming would soon become a major issue and for a while, I was somewhat impressed by the evidence.

 

However, I once took a course with the OU on the subject and after about 2 months of studying the material, including projections of warming well into this century, it dawned on me that this was utter rubbish! When I look at day to day model output, I can usually tell if the predictions look reasonable or possible, and I try not to put too much faith in the longer term. Yet, this course was asking me to accept predictions out to 2050! I packed it in because even with my limited scientific understanding, it all just looked plain wrong.

 

Since then, if for no other reason, I have concluded that any predictions of temperature rises of the order predicted are based on a minute sliver of data within the massively long history of this planet, and as such are flawed at source.

 

So too with our daily model runs that we set so much store by. If a chart verifies at 5 days we consider that a success. Therefore, I would urge people to use their experience and their common sense when considering output and not take anything for granted. In our massive climatological history, the variations that have occurred, even in the thousands of years for which we can deduce data, have been huge and of infinite variety. The various indicators that have gained credence in relatively recent years I see as just that; indicators not causes in themselves. The weather is a system with myriad interacting parts, so assessing the role of any one indicator is future weather can never be done in isolation. Indeed, I maintain our conscious minds do not have the capacity to weigh up so many variables and come to any conclusion. That ability resides in the subconscious - intuition and hunches are its output.

 

Study the current charts, that's what I believe in and learn the patterns to our fascinating climate in this country. Anything is possible if you look at how far we've come and what we must have already experienced, so never pre-judge and expect the unexpected!

 

So ends the lecture from the OldMetMan!

 

 

 

 

[Model Output Discussion; into 2015]

On the face of it, the current situation would look perfect for pressure rises to the NE -  slack LP field for the first time on ages over Scandinavia, strong upper ridge to our W, LP pushing NE on its NW flank which you'd expect to build the upper ridge and carry surface pressure rises with it. But alas no, well at least not yet. All the really cold air according to the models looks destined for E and SE Europe - just too far away darn it!

 

But this, as espoused by the GFS-Para looks more like it:

 

 

Now that is how it should be looking now. It'll be interesting to see if that idea persists.

 

 

 

 

[Model Output Discussion - The final stretch to Christmas]

Some snow fun for some of us tomorrow, with a considerably downscaled LP tracking across us.

 

Although there are model agreements on the developing HP that is predicted for us in the coming days, I can't help but feel that the location of the HP is too far SW and higher pressures look more likely for Scandinavia, and to our N,  rather than over us. This would involve a more SW-NE orientation to the associated upper ridge. With so many changes in output models recently, it seems a possibility. With that, of course, a more direct, colder continental flow would happen. As things stand, we are still likely to import some pretty cold surface air.

 

 

Beyond that, as ever the GFS brings back the progressive flow but I very much doubt it will be that easy. If cold air gets entrenched over Europe then we may at last see some useful (for us) blocking. HP has been stationed pretty close by us for quite a while, I would be surprised to see it remaining so. Recent trends have shown several of the sub-tropical HPs shifting significantly eastwards, the Azores HP included.

 

http://meteocentre.com/analyses/gem/get_anim_analyse.php?stn=PNGZ&map=hnord〈=en

 

Don't despair at the current bland output (apart from tomorrow). I am sure more interesting, colder possibilities will appear soon.

 

Merry Christmas everyone. I hope Santa brought you everything you needed.

 

 

[Model Output Discussion - The Run In To Christmas]

The models' ambivalence as to what happens on or after Christmas Day continues. The spectacular looking LP for 27th would indeed be interesting, but I guess the chances of anything like it happening at this distance are pretty remote, although having said that, it is a possibility.

 

What I find odd still is that there have been no real signs within the models of a pressure build from the NW after Christmas. Pressure rises to the S or SW yes, but that is all. Several days of cold air coming S across the Norwegian Sea, LP much weaker over Scandinavia, a situation which has in the past given rise to some noteworthy frontal battle grounds between cold and mild.

 

Here's a nice example from 1982.

 

 

That one produced significant snow across the S as an advancing frontal zone stalled as it pushed into the cold air to the N.

 

As always, I am aware that no 2 situations are ever the same, and I wouldn't mention it but for the indecisiveness of model output at that time, but it's an intriguing possibility and, dare I say it, no less unlikely than the GFS major storm!

 

It will be interesting to see later model output and whether we have any sort of consensus developing.

 

 

 

 

[Model Output Discussion - The Run In To Christmas]

The 12Z GEM shows what I had in mind in my last somewhat cryptic post!

 

 

I would think the LP to the SW might be a little closer and the ridge from Greenland maybe stronger but as the cold air spreads S, the frontal zone would split, with a warm front headed W around that LP.

 

Something similar I remember happened once before at Christmas as cold air pushed the mild Atlantic air away - rain turned to snow on that occasion.

 

 

 

 

 

 

 

 

[Model Output Discussion - The Run In To Christmas]

I think both the GFS outputs are suffering from an excess of Christmas spirit. Ah well, no doubt later runs will change it all again.

 

Beyond 4-5 days at the moment with the models is just too silly, so instead I shall look at where we actually are.

 

 

One thing I found encouraging today is the appearance of a closed upper high north of Iceland. The US ridge is also holding its own and continuing to move E. The wretched upper low over the W Atlantic has finally lifted out. It seems the pivotal moment is around Christmas Eve, as the cold front drifts SE. Is there likely to be a developing LP to the SW on Christmas Day as the GFS shows?

 

Well, I think not, at least not as shown. It still looks to me as if this is where a marked reversal of the flow is starting. What's needed is for a low development to occur to the SW, for that to deepen in situ, absorbing the LP to our N as pressure builds S to the E of Iceland. SE flow then turning E over the UK as the cold air continues to push southwards.

 

That little closed upper high already in place as mentioned is the sign I have been looking for - a tentative indication of northern blocking to come.

 

OK, a flight of fancy perhaps. In spite of the numerous different model solutions confusing things  I still believe the trend towards cold is developing and I think that whatever form that takes, the models will have much trouble with it, until it's nearly upon us.

 

Interesting times ahead!

[Model Output Discussion - The Start Of Winter]

The latest ECM at T240 has that "shape" again - LP strung out across the Atlantic south of 50degN, associated with an extended upper trough aligned E to W. Above this, an upper high stretching from Canada to Greenland, with associated HP.

 

So much depends on cold air extending far enough S, both in terms of its depth and extent. Given enough of a block, and a continuing cold feed down across the Norwegian Sea, LPs in this situation will run NE and glance off the cold block, until finally one runs far enough SE to fully engage the cold air to its N - perfect recipe for a good dumping of snow.

 

Such a situation only rarely works out just right but it does happen and it's a delight to watch. That would be enough for me this winter to see one of those develop, I wouldn't care what happened for the rest of it!!

 

[Model Output Discussion - The Start Of Winter]

Nice one Old Met Man, hope your hunch comes off against all odds. The fairly strong Baroclinic zonal developing to the north of the Azores high looks like creation of convergence and ultimiately the formation of low pressure system into Southern Britain that the GSF (PARA ) has aspired too over the latest runs. Not too un similar to what your instincts were a few days ago with a resultant NEer. Its a start.

C

Thanks Carinthian. Such situations can be very finely balanced. Quite rare are the classic setups like the one I mentioned the other day from 1978 - hell of a blizzard that was! Too often the warm Atlantic air will push into the cold air and win, not before dumping a load of snow. It's a shame they don't last longer!

I'm curious really as to why the GFS keeps producing these kind of scenarios, even though they change run to run. Let's see how the models deal with the run up to Christmas, which is still itself a bit open at this stage.

[Model Output Discussion - The Start Of Winter]

Ah would that such a chart should verify, some substantial snow would be falling for many. There's that build up of cold air again that I was talking about in my last post, stretching from Canada to Russia. The GFS keeps coming up with similar variations on this theme so definitely something to watch here I think!

[Model Output Discussion - The Start Of Winter]

which happens to be a year thats been chosen on a lrf on an american weather site.

 

the problem is the azores heights is also well and truely at home to our south and could be there for weeks to come judging by the model outputs and could possibly move futher east setting up a bartlet type block.

 

theres lots of talk on the american sites of a winter storm dated around the 19th to the 21st of this month over the pond in the states.

and also talk of the vortex setting up like last year over there in the states,

so dare i say a return to a rerun of last winter ?

 

although id be very intrigued to how much effect this could have here,

 

i suspect a return to a more typical zonal that we are getting now,

but less intense than last winter as the vortex is not as strong as last year.

how weak is the vortex currently is there a chance of a strengthening vortex.

 

http://theweathercentre.blogspot.co.uk/2014/10/official-2014-2015-winter-forecast.html

I wish I knew the answers!

Looking at this time last year, things were very different indeed:

Never say never, but I would have expected to see something in place over Canada already if we were in for some sort of re-run. As it is, the pattern over most of continental N America has been strangely benign. That in itself makes me a bit suspicious, because I am wondering how the pattern will change. It just seems most unlike a typical mid-December situation there and I can't get a handle on what exactly will happen - yet

I cannot point to any specific "drivers" and say those are my reasons for expecting a major change. I rely solely on my "weather instinct" for want of a better term!

I wouldn't worry overmuch over the Azores HP. Sometimes it can work in our favour when it comes to coldness.

I follow the US WV satellite imagery a lot because it highlights the changing long wave pattern very well. Hurricane forecasters make use of these a lot because of this.

I'm keeping an eye on the jet strength and path, watching for any noticeable change. When I can get a clearer idea of what is changing and how, I shall post about it to be sure!

[Model Output Discussion - The Start Of Winter]

Having been searching (rather desperately at times I’ll admit!) for some sign, any sign of a breakdown in the relentlessly progressive flow affecting us, no such sign has been forthcoming. The 500mb vortex over the W Atlantic is continuing to spawn LPs in the southern stream, destined for our shores, which has been added to at times by LP in the northern stream which have kept crossing Greenland, preventing any prolonged build-up of cold air, and thus HP there.

The GFS has been coming up with some intriguing long-term fantasies, but the short to mid-term has been fairly consistent across the models in the run up to Christmas, including the cold-lover’s worst nightmare – HP over France and Biscay!

However, I am with TEITS on this and feel strongly that a major pattern shift is gearing up for after Christmas and into the New Year. One of the first tentative signs of that today I think is the appearance of an upper high over W Canada, not much in itself but maybe an early sign of a trend to greater upper flow amplification, at least in the W hemisphere.

That flow does, I think, have a most peculiar look for mid-winter, with quite a number of fairly shallow vortices, showing little sign of moving. Indeed, between the vortex over the W Atlantic and the one over Iberia, that has done much to keep the Azores high firmly entrenched.

But what I am seeing as a possibility is for the slow but steady build-up of cold air and thus HP to the N, The Greenland HP would at last have a chance to intensify.

Many notable cold spells in the past have been preceded by a string of LPs heading across us from the SW, as cold air deepens to the N and NE, and the track of these has shifted slowly but steadily SE, finally allowing the cold air to break through. Here’s a spectacular example from 1978, a few days before a bitter E-NE flow set in.

In one of its many end of run variations, the GFS actually showed such a development recently, not that it means much admittedly, but it must have come up with this idea from somewhere!

OK, a certain amount of straw-clutching you might think, but even in the face of current evidence, I am still inclined to trust my instincts here. If such a development is going to happen, then I suspect it will take a while for the models to catch on.

So if the current setup looks bleak, then look ahead and watch for the signs!

[Model Output Discussion - The Start Of Winter]

I was just going to keep quiet for the time being, given the mundane model output in recent runs, but this morning's 06h GFS shows some very interesting changes from previous runs. Not that you can attach too much significance to a single run, especially that far ahead, but it does show potential.

The most striking features that caught my eye were the appearance of a high-amplitude ridge over central US/Canada by next weekend, plus the appearance of the Arctic HP. Indeed, on the chart below, there seems to be a noticeable sign of HP attempting to link northwards over and to the W of us. There is also signs of a slower moving upper vortex off the Canadian east coast, all of which would finally slow down the zonality.

Another possibility could be HP finally building SE into Scandinavia as the ever-present LP there at last fills. So potentially a NE stream heading our way or an E one.

I haven't seen the end of the 06 run yet, but I can guess it will be south-westerly zonal. No matter, this to me is a very important sign of change so I shall await later runs with great interest.

[Model Output Discussion - The Start Of Winter]

I was somewhat inclined to keep my mouth shut today after prattling on about northerly blasts yesterday! But I suppose a 24 hour-ish one is better than nothing, enough to make the MetO issue a Cold Alert anyway.

However, I will stick my neck out again and say that in spite of the relentlessly mobile pattern portrayed by the GFS, I still believe a more significant northerly flow is possible next week, assuming of course there is enough mid-Atlantic ridging by then, which is sadly lacking right now.

The ECM looked most promising:

A quasi-stationary polar front straddling the country in the situation shown for the coming days is not usually something that stays that way for very long, and as I keep saying, the cold air usually wins. All that is needed is a deeper, more slow-moving vortex off the US coast, plus the amplification I mentioned (not necessarily a high amplitude one) and the polar front could finally head south.

I don't have a lot of faith in the longer term GFS right now, so we'll see what the ECM has to say in later runs. Anyway, make the most of our mini-northerly!

[Model Output Discussion - The Start Of Winter]

Not trying to knock you an ex colleague at all just trying to put another viewpoint in here.

I also mean no 3 day or longer deep cold is likely not the current output of 1-3 days deepish cold for the northern half of the UK, to me that seems likely to occur through the next 2 weeks so some will be happy some not.

 

got to agree with you totally about the 'weather bomv' a lot of other misused meteorological terms on here though.

Not to worry John. I should once more describe my own peculiar method, if you can call it that, which relies more on instinct and intuition, after many years of studying charts. My ability to synthesise the many different factors determining future weather trends is largely subconscious, so in that sense not exactly scientific. I just look at the model output and it looks "wrong" to me sometimes. I fully accept your reasoning and logic.

It'll be interesting to follow future trends as I find this kind of situation most interesting, with a lot of potential

[Model Output Discussion - The Start Of Winter]

I've been studying model output on and off all day, and for the life of me I cannot make much sense of anything shown beyond about 3-4 days. The sticking point for me has been the insistence of maintaining progression (except for the GEM earlier, but even that has now backtracked) when, to me, the whole situation right now is shouting "amplification"

So, in such cases, I take a look at what is actually going on right now, that is, current analyses and satellite imagery.

First, the current surface analysis:

So what do we have? A strong PM airstream, LP to the N, a good solid looking HP over Canada, stretching SE towards the Azores and LP heading NW into the E USA. Developing from this is a northern stream wave heading E, engaging the cold air and deepening. So far so good. But after that, we have a) maybe another such wave, b) maybe the polar front meandering across the Atlantic, c) a flat W flow with a series of LP, taking us in and out of the cold air. In other words, quite a confusing mixture.

So, why progression? Why not a solid blast of cold northerlies, lasting more than a few hours, maybe with short-wave features heading SE from the S Greenland/Iceland area?

The hemispheric WV loop is interesting.

http://mp1.met.psu.edu/~fxg1/SAT_NHEM/animweur.html

This shows the extending upper trough off the US. the same off the W US coast. Even some extension of a trough towards the Med. Amplifying long waves.

All of which suggests to me ridging in mid-Atlantic and a more long-lasting cold northerly outbreak.

I may be way off here of course! Maybe the last GFS today might look a bit more realistic!

BTW, who else is sick of hearing this silly "weather bomb" expression?!

[Model Output Discussion - The Start Of Winter]

I do hope your instincts are correct on this but the GEM is the king of the amplifiers and has seemingly performed quite

badly recently. What better time though to thoroughly redeem itself

Indeed yes it would be! It was the only run that "looked right", according to my unscientific appraisal! If the GEM model is the amplifier, then I guess the GFS is the opposite, so maybe the actual outcome will be somewhere in between. We'll see!

[Model Output Discussion - The Start Of Winter]

Out of all the latest model runs this evening, I think the only one that seems to have any sort of a handle on future developments past 3 days is the GEM. The GFS has seemed to bring the colder air slowly southwards over successive runs, but both it, and the ECM seem quite clueless as to longer term trends.

I would say that as a general rule, once a W-NW cyclonic flow has become established, as it will have within 24 hours, any subsequent frontal development that may occur to the NW, in the Iceland/ S Greenland area, would tend to head SE and reinforce the upper trough that is now developing to our N. As a result, progressively colder air tends to get dragged further S.

I'd go along with the initial wave development over the next couple of days which looks reasonable, possibly having quite a tight gradient on its western side, but beyond that things seem to come a bit unstuck.

The latest GFS analysis:

The upper low is digging SE. Bear in mind we still have a weakish vortex in the Med area which this is feeding into. Good HP upstream developing S of Greenland, whilst the upper trough over the E Us/Canada seems to be going nowhere. Further upstream from that, quite a pronounced upper vortex heading into the SW USA from the Pacific, which I would think likely encourage heights to rise over the central US. All in all, quite a stable pattern I would say, looking likely to persist for a few days.

Now, as I see it, this is how the GEM is taking it forward and its chart at T180 is a logical and quite plausible progression from where we are now.

So, we are left at that stage with a cold, unstable airmass, always with the possibility of small convective disturbances (polar lows/troughs) forming within it, which can mean snow almost anywhere.

Beyond that, well, as I mentioned earlier, the possibility of a pressure rise over us and importantly, as the low fills, a chance for a pressure rise over Scandinavia and an opportunity for some significant continental coldness to head our way.

All the above I base on what I have seen happen before in similar circumstances. Hardly conclusive I know but I do feel the models are struggling a bit with future developments, We'll have a better idea within a day or 2 I think.