Model output discussion - Closing in on Christmas

[ITSY]

Goodbye SPV - don't hurry back! 

And she's in two! Ahead of schedule indeed...

In ordinary years we'd be laughing if we were seeing our current synoptic forecast a week prior to this kind of stratospheric event. Still only forecasts, caveats caveats, project fear project fear bla bla, but it's a good place to be. 

Edited December 18, 2020 by ITSY

[Kasim Awan]

6 minutes ago, Vikos said:

The air flow over the warm North Sea and the lack of really cold air masses in the north is the problem we have in Central Europe for a real significant onset of winter within the next 10-12 days. Unfortunately, this is a fact. Sleet showers at 2 degrees floor temperature is not 

There may be some sleet mixing on the coast / low levels in the centre of any shortwaves where uppers moderate, apart from this all snow / hail ~95% of all ppn for the 28th there.

525 at 500/1000z, etc etc

 

edit, don't forget the heavy showers would drag down the polar air above.

so soundings would change 

Edited December 18, 2020 by Kasim Awan

[Matt H]

I’m in no way convinced yet that a decent cold spell will come off considering how many times the models have backtracked from decent synoptics. However, I do get the sense that some people in here could be staring at a blizzard unfolding outside their front doors and still be on here moaning that the uppers won’t be cold enough for snow.

Edited December 18, 2020 by Frosty Winter

[sheikhy]

Aaaand the control run aftter making a hash of it for a while decides to join the op!!!thats the op telling it please dont resist cos it dont matter what you do you will stick yourself into greenland❄!!

[Glaswegianblizzard]

4 minutes ago, Portsmouth Sun said:

Because it's so far off it hardly ever verifies and people end up with egg on their face.  Happens every year, be it hot summer weather or snowy winter forecasts.  

Only people will have forgotten as when the time comes the same posts will be getting made about another ten days time. I get what everyone is saying about patterns, trends etc, but until I see it forecasted on met office, BBC, my iPhone weather app or even the Norwegian met, then I’m not buying it I’m afraid. 
 

Accompanying these excited posts are forecasted highs of 4c in glasgow on 23rd and 24th. Frigid it absolutely is not. Why does everyone fall for this still?

[Vikos]

1 minute ago, Kasim Awan said:

There may be some sleet mixing on the coast / low levels in the centre of any shortwaves where uppers moderate, apart from this all snow / hail ~95% of all ppn for the 28th there.

525 at 500/1000z, etc etc

That’s 39 gfs runs from now on. Good luck and keep the faith! ?

[SLEETY]

7 minutes ago, Weathizard said:

Why do the same people constantly feel the need to remind everyone its at day 8 or 10? Genuine question.

Atlantic amplification is fairly reliably modelled, of course we could still end up being unlucky but you have to say it looks absolutely primed.

Because they hardly ever verify as you should know I would have thought anyway, seen countless gfs and ecm  charts at day 8 onwards showing a winter wonderland but they never actually make it into reality 99 % of the time, waste of time to be honest that they go out so far. 

[Cold Winter]

GEFS at T192 looks to be about a 50/50 split between lovely ridging to Greenland with subsequent northerly and a horrid flatter westerly pattern... but I don’t think op will be a major outlier.

[Ali1977]

5 minutes ago, ITSY said:

Goodbye SPV - don't hurry back! 

The best thing about this happening late Dec is the ramifications will be mid to late Jan. IF this does become an SSW and we do profit from the effects -  it will be perfect timing.  

Edited December 18, 2020 by Ali1977

[STRiZZY]

1 minute ago, SLEETY said:

Because they hardly ever verify as you should know I would have thought anyway, seen countless gfs and ecm  charts at day 8 onwards showing a winter wonderland but they never actually make it into reality 99 % of the time, waste of time to be honest that they go out so far. 

Only a waste of time if you focus on details 8 days onwards. 

[Mike Poole]

4 minutes ago, Uncertainy said:

Yes GEM trending more amplified after a soggy Wednesday, even though it develops the mid week low it’s the upstream amplification a few days later  that’s key to the post Xmas day pattern.

Regardless of Uppers, PPN etc, the fact that 3 successive GFS, the GEM and to a lesser extent ECM op and control get to this point is significant. Given the strat support for a Scandi trough we can now say that some manifestation of this broad pattern is probable. The question is how high can we get this ridge to go? 
 

In other news...

Positive temperatures in the strat alert!

That is less than two weeks away and a consistent signal.

Ahead of schedule surely? No complaints from here  though if this run verifies at either atmospheric level!

Yes, the strat signal is now looking very consistent.  I have to admit to being a bit worried by this if the current trop output continues.  A SSW will shuffle the deck, which with the usual Atlantic dross would be fine.  But should a Greenland high develop, the deck would be in our favour, and a SSW risks something less favourable.  Still that is so for another day.  

Re today’s output, as others have said, remarkable consistency from GFS, and good to see GEM on board too.   I would like to see the ECM follow suit tonight.  

[Mucka]

1 minute ago, Vikos said:

That’s 39 gfs runs from now on. Good luck and keep the faith! ?

The MetO have gone for it now 

Any real cold pattern won't deliver until after Xmas if this pattern is correct.

[Allseasons-Si]

3 minutes ago, Polaris said:

It’s 10 days away, be Gobsmacked when it’s T72 

Yes polaris,i  am fully aware of that

i will show you a little explanation as to what happens at just 156 hrs

firstly(circled) is a trough that gets sheered/disrupted S/SW thanks the opposing heights to the NW and E/SE,this in turn would build the two ridges over the top creating one hp cell,also with a downstream trough in E America this also in turn would amplify the ridge upstream in the Atlantic

this is quite plausible but it is still just out of the reliable timeframes(96-120 hrs) and any other disturbances/shortwaves can scupper what is being shown at the moment.

 

[Rocheydub]

Those of us around here long enough, will remember the winter of 09-10 where the models, nearly in unison, counted down the days from 12 days out with northern blocking, coming in with every run! This has the same sort of feel about it, consistent and all singing from the same hymn sheet.

That said, we've been bitten before, at 96 hours out, but that happens mostly with Scandi highs. GHP's are that bit more reliable IMO.

My advice would be, enjoy the eye candy charts, and if they come to pass, then super. If they don't, then so be it. This year has been horrible for hundreds of thousands of people across our islands, this comes as a nice distraction to us weather enthusiasts. Enjoy it, try not bicker, and pray to whatever God or deity you follow that they do come to fruition!

[ITSY]

As per prior posts, you don't need -15 uppers to have a notable cold spell. Control goes for a back-edge trough causing snow down the central belt of the country


 

[Uncertainty]

2 minutes ago, Glaswegianblizzard said:

Only people will have forgotten as when the time comes the same posts will be getting made about another ten days time. I get what everyone is saying about patterns, trends etc, but until I see it forecasted on met office, BBC, my iPhone weather app or even the Norwegian met, then I’m not buying it I’m afraid. 
 

Accompanying these excited posts are forecasted highs of 4c in glasgow on 23rd and 24th. Frigid it absolutely is not. Why does everyone fall for this still?

It’s still fun to get excited about it though pal. Make your own judgement regarding whether it’s actually going to happen.
 

Those excited posts are part of the lifeblood of this forum, just as the ‘winters over’ memoirs after the Inevitable 0z backtracks appear are!
 

This pattern is more than just a one-run GFS wonder though. But, as you say, it’s a long way off being ‘in the bag’. And any exact details regarding surface temps, precipitation types and amounts are moot as this stage.

[Mucka]

GFS 12z ensembles at 192

show around 35% giving a clean evolution to blocked and potential Greenland high, prolonged cold spell type scenario as with the Op including the control.

Cautious optimism...

Edited December 18, 2020 by Mucka

[Georgina]

It’s so confusing some people say it’s a terrible run and some are saying it’s a stonker ! I’m not very up on the charts and all they show but I do try and I’m just getting really confused

[iowpompeylee]

Hi all, for me I’m too long in the tooth to be looking at precipitation charts etc for Xmas day and beyond! Delighted we having cross model agreement on a cold spell! Trends, trends, trends!! But I’ve got my guard up til Tuesday! Get the cold in first and anything is up for grabs! Exciting model watching

Edited December 18, 2020 by iowpompeylee

[Ali1977]

You think we are chilly for Xmas, look at the Eastern side of the USA

[Geordiesnow]

3 minutes ago, Glaswegianblizzard said:

Only people will have forgotten as when the time comes the same posts will be getting made about another ten days time. I get what everyone is saying about patterns, trends etc, but until I see it forecasted on met office, BBC, my iPhone weather app or even the Norwegian met, then I’m not buying it I’m afraid. 
 

Accompanying these excited posts are forecasted highs of 4c in glasgow on 23rd and 24th. Frigid it absolutely is not. Why does everyone fall for this still?

The problem as usual is none of the GFS FI runs will look like that if we don't get proper ridging into Greenland and let's be honest sadly, we have not seen many  Greenland highs developing despite the models want to indicate otherwise.

As for the colder shot in the shorter to medium term, I'm getting more confident this will happen now, I thought the UKMO 120 hours is a decent cold chart in fairness. I just hope the ECM drops its deepening low pressure system over the UK set up so we get into the colder air quicker. 

All will depend on the Atlantic ridge of course, the first northerly is likely to be a toppler but there could be some wintry weather around for some. 

[Mucka]

1 minute ago, Georgina said:

It’s so confusing some people say it’s a terrible run and some are saying it’s a stonker ! I’m not very up on the charts and all they show but I do try and I’m just getting really confused

It's a stonker. 

All you can look at is the general theme that far out not the detail which will change run to run.

It is a V cold signature of Atlantic blocking that typically brings widespread snow to the UK.

[Osbourne One-Nil]

If anybody wants to take advantage of this busier than average period we're experiencing at the moment, but trying to make a name for themselves by being contrary for the sake of it, or a little bit snappy or otherwise just trying to spoil what should be a nice harmonious discussion about the weather....good luck! 

[Kasim Awan]

In theory the ECM should get a better grip on the flow dynamics between Iceland and Svalbard D6-8, icon, gfs and gem all favour dynamics here more conducive of slower development than the local cyclogenesis shown on the ECM 00z. This (should) give us a fantastic ecm run. I'm betting on it anyway.

[northwestsnow]

1 minute ago, Mucka said:

GFS 00z ensembles at 192

show around 35% giving a clean evolution to blocked and potential Greenland high, prolonged cold spell type scenario as with the Op including the control.

Cautious optimism...

35%...?

Think I will stick to the Doubting Thomas role for now !