Model Output Discussion - Winter arrives

[northwestsnow]

GEM doesn't quite get there but is more GFS than that awful EC ...

[Chesil View]

Interesting to see that on this occasion it is the ecm det run that is flip flopping regarding scandi heights rather than the gfs which seems to have found a modicum of consistency in recent runs. 

Ukmo raw output seems to be siding with gfs for now

As ever time will tell.

[Griff]

16 minutes ago, northwestsnow said:

GEM doesn't quite get there but is more GFS than that awful EC ...

You're right, to be fair, there's an awful lot that could change but the trend is fun for now. 

Reasons to be cheerful if non standard synoptics are your thing

2 minutes ago, Broadmayne blizzard said:

Interesting to see that on this occasion it is the ecm det run that is flip flopping regarding scandi heights rather than the gfs which seems to have found a modicum of consistency in recent runs. 

Ukmo raw output seems to be siding with gfs for now

As ever time will tell.

Very true. 

Edited November 28, 2021 by Griff

[nick sussex]

Some strange goings on with the ECM which at day 4 was the most amplified upstream , day 5 looked good if you look at the more sharper ridge ahead of the shortwave near Newfoundland and then it hit the buffers big time .

The wheels come off as it’s then more progressive with the troughing over southern Greenland and you can clearly see the difference with the GFS which is more sharper and digging further south .

Realistically any Scandi high won’t sustain but with the GFS you can at least get enough easterly flow for a battleground scenario .

The troughing is also effected by shortwaves running east post day 7 across the USA where there’s also disagreement .

 

Edited November 28, 2021 by nick sussex

[mulzy]

Early view of the mean EPS days 9-11 suggest heights in mid-Atlantic and heights to the north east.  Lower heights over Europe and in the Greenland locale.  The good news is that the low height anomaly over Greenland is much less intense,

I would say the ECM Det has only limited support from its ensemble suite.

 

Edited November 28, 2021 by mulzy

[northwestsnow]

Mean eps sound like an upgrade...

I like upgrades

No repeat on 12z please EC ...

[Ali1977]

Latest bbc graphics vs reality - they really should try and keep up!!! The precip is in the right area I guess

Edited November 28, 2021 by Ali1977

[Mark Smithy]

Another fascinating GFS run.

In these circumstances I guess you'd say that usually the Scandinavian High easterly never seems to come off but it does seem to at the wrong times of year so there's no reason why this feature, which is starting to appear increasingly on the models, should not happen.

If we really do get to c. 10th December with a solid Scandinavian High, intense cold there and pooling down into the continent, with an easterly knocking on our door then we are back to a winter set up not seen for many many years in this country.

A long way to go.

[sheikhy]

Not the best ecm has to be said!!gfs and ukmo continue to upgrade though!!if gfs and ukmo show the same 12z i expect ecm to move over later on!!judging from the ecm mean the op has kinda lost the plot this morning!!if ecm joins ukmo and gfs  im gona have a lot more to say bout this model later on!!!

[IDO]

The potential transient Scandi heights are again likely from the ebb and flow of the trop and seems to be wedge derived:

T138 GFS>  T168>

A wedge at D5 from a rolling Atlantic high and then again at D7 when the high bells up, feeding that wedge. From last year, this was a regular FI development, that proved very hard to model, and I suspect that this is the case here. The spread highlights that:

D8 spread>  D8 GEFS: 

Looking at the GEFS for that period and a wedge looks most likely, but no consistent take on how it evolves. I suspect this is the case with the ECM ensembles and a case of wait and see?

[Ali1977]

This is great news that the Op was one of the warmest , looks like temps are actually dropping off at the end in the ENS 

[carinthian]

23 hours ago, carinthian said:

Morning all from a very snowy Eastern Alps this morning. Woke up also to pictures on the news over here showing the damage caused by the North Sea storm over Blighty. Yes, the models still not in 100% agreement of how @nick sussex short wave/ disturbance between Iceland and Ireland shown on the chart below from GFS is going to interact with the Northerly jet and the developing colder block close to the British Isles. Period 120-138 t still could lead to various outcomes out at day 5/6. Personally, still think we are better placed to end up with a (old school Scandinavian high ).

C

Morning all from a very snowy Eastern Alps . Just an update with my thoughts following on from my post yesterday morning. Firstly, regarding the little feature forecast for next Friday morning, both GFS/UKMO have a further squeeze westwards on it progress with a limited window of warmer air. The snow models forecast small amounts at this stage but with any transient snow now also further west than shown yesterday. Looking forward at 168t it would seem going by the jet profile below from UKMO extended that it is heading in the same camp as GFS. In fact even looks a more amplified profile than the latest GFS run at the same stage. So are we heading for a Scandinavian High ? Without ECM not really on board there remains the usual doubt , but if we can hit the jackpot for you guys, some serious cold could soon envelop Blighty as Scandinavian Highs are quite rare in December but if in place will deliver special winter weather. I remain again optimistic this morning for you guys from what i can work out.

C

[bluearmy]

To ridge or not to ridge ……..

I think that the likely success of this feature and it’s ability to gain enough northerly traction to bring CAA rather than being a sceuro feature depends on the polar profile. 

no shock at the ecm evolution on that score but I was surprised at how amplified the gfs managed. At the moment it looks like too much upstream energy to allow the ridge to make it and stick but even a half way house of a couple days could provide interest if it builds far enough north to split the jet with enough headed south. It’s all about timing and there are too many variables for the modelling to currently have a hope of making the correct call. 
 

But with the tpv continuing to ebb and flow between n.e Canada and ne Siberia, there should be space on our side of the NH for some build in heights, even if it’s only wedges left from amplified ridges. 
 

can’t see it being a quiet first half December in here ……

[Methuselah]

Well, I was hoping for more substantive pressure rises out near Scandinavia, and the GFS 00Z tries its level best to deliver (eagerly awaits the 06Z!). But a lot will depend on how cold things, to our east, get/stay? The potential is definitely there. And it sure beats zonality!

    

    

    

But, as a caveat, if things are about to take a turn for the 'worse', it's not yet reflected in the GEFS mean and might explain why the anomalies are not 'aware' of it. Good times ahead, nonetheless!

  

[Ice Day]

UKMO / GFS / ECM @ 144

    

I think there's enough differences at this stage to ensure we treat anything beyond this timescale with even more scepticism than usual.  As Ed said above, the GEFS aren't particularly supportive of the GFS yet, but having followed them religiously last year I'm not overly sold on them being too instructive, especially where the weather pattern is not the norm (i.e., potential easterlies).  That said, they're still another tool and fun to look at!

I think we'll know by probably Tuesday whether this will be a proper chase or an early season bust.  I suspect the ECM will probably be nearest to the correct solution.... but we shall see.  Cracking start to the season though, it's not even December yet. 

[damianslaw]

Continued 'interesting' fayre from the models for the foreseeable, a topsy turvy spell, lots of change day to day, mid atlantic heights still gain a hold on things, sending the jet profile on a NW-SE trajectory whilst at the same time we have a signal for heights to develop over scandi. As others have said the outlook for the first part of December will depend on how much amplification we can maintain, the overall jet profile looks wavy so it suggests quite a bit.. evidence of this is clear in the coming week, low pressure dropping to our SE not east.

Always a little dubious of GFS when it comes to heights to our east, traditionally ECM does much better in spotting developments in this direction, whereas I rate GFS more for developments to our NW. Mind UKMO is going with GFS rather than ECM, Lets see how the models pan out through the day, if GFS maintains the theme into early next week, I'd be surprised if ECM doesn't follow suit.. conversely if ECM doesn't, expect GFS to quickly fall into line.

One thing we can see we are starting December on an interesting note, with lots of possibilities.

[SLEETY]

ECm looks way too progressive this morning,computer probably running too hot this morning..Run looks wrong and a huge mild outlier at the end.

Expect  much better 12z run

[northwestsnow]

3 minutes ago, SLEETY said:

ECm looks way too progressive this morning,computer probably running too hot this morning..Run looks wrong and a huge mild outlier at the end.

Expect  much better 12z run

WRT the last sentence...

As a cold zealot  burned many times one always expects/ fears  downgrades

[SLEETY]

On 28/11/2021 at 09:10, northwestsnow said:

WRT the last sentence...

As a cold zealot  burned many times one always expects/ fears  downgrades

Just seen the ukmo 168 hour chart  on twitter ,awesome,if it verifies

[blizzard81]

8 minutes ago, SLEETY said:

ECm looks way too progressive this morning,computer probably running too hot this morning..Run looks wrong and a huge mild outlier at the end.

Expect  much better 12z run

Yep I'm hoping the ecm op had too much sauce last night. We can't rule it out though unfortunately. Like Northwest says, bitter experience has taught us the hard way. That op also ties in with the Exeter updates as well so we should sit tight and see what the 12z run brings. 

[blizzard81]

1 minute ago, SLEETY said:

Just seen the ukmo 168 hour chart  on twitter ,awesome,if it verifies

That really is a nice chart . Great to see ukmo agreeing with the gfs. 

[Anthony Burden]

Morning all,some very interesting charts this morning,Gefs ensembles very interesting could be an

easterly on the horizon.My take look for low pressure diving southeast bringing easterly winds and

high pressure development in Scandinavia very encouraging in my book.

 

[Nick F]

All three EC, UKMO and GFS looks similar up to T+168

EC

UKMO

GFS

It's after that EC and GFS diverge, EC keen to push east a lobe of the TPV towards NE Atlantic which makes any amplification brief. Whereas GFS moves this lobe NE across Greenland - which helps build heights over the GIN corridor and Scandi.

EC T+192

GEM similar to EC T+192, but after that at least it disrupts the Atlantic trough with energy going SE into mainland Europe while heights build to the NE. 

EPS H500 mean does show a growing +ve height anomaly by day 10 over Svalbard and what looks like Atlantic energy disrupting SE into mainland Europe - so be interesting to see if we start seeing some high latitude blocking appearing to our NE in the coming deterministic runs with Atlantic troughing and lows disrupting over NW Europe.

Some interesting model watching ahead ...

Edited November 28, 2021 by Nick F

[Dennis]

Goodmorning WINTER freaks

 

alot of good opportunities - lets count down to DECEMBER

 

[Cambrian]

10 hours ago, PiscesStar said:

Which means in layman's terms please guys??............. 

Thank you, @PiscesStar. The post was a reflection on the last few runs of the GEM model showing further episodes of the same broad pattern that we have been looking at off and on for several weeks now, that of an undulating meridional jet stream pitched at the UK and Ireland along a NW-SE trajectory from Greenland. This keeps us in a slowly mobile pattern and rather chilly air flow from the northwest, with some occasional shots of colder air more directly from the north that can bring more general chances for wintry weather, like this weekend. It has to be said that it’s not the only pattern being seen in the models and there are some indications of potential for a change to having high pressure to our north or over Scandinavia after the next week or so which could bring us into a more sustained cold flow from the east.

The 0z GEM operational run keeps this NW-SE pattern again this morning. Here’s an example in the 72-96h timeframe. The meridional pattern undulations in the Atlantic jet stream at 72h lead to the arrival of a low pressure system in the North Sea, where the jet stream buckles. If travelling in the stream, from NW to SE, the lows are forming at the left exits of the jet, where it takes a turn to the left.

 

By 96h, the jet stream dives more directly south, bringing us into a more direct northerly with some colder upper air, perhaps cold enough for some snow in northern parts and on the higher ground.

  

It’s similar to how the jet stream was over us this cold Sunday morning.

There are further repeats of this general pattern later in the run, though each buckling is slightly different in amplification and in how far south it is, which means that some of the northerly or northwesterly blasts are colder and more sustained than others, some will have more precipitation wrapped up in the circulation of the resulting lows, and these details are getting firmed up at the moment all the way through to only 2-3 days before the lows arrive.