Model output discussion - Closing in on Christmas

[Skullzrulerz]

1 minute ago, alexisj9 said:

Unfortunately the little low could still do this, let's just hope not, all depends on when or if it phases with our jet stream.

Not to mention we have this shortwave business to get around too as well 

Starting to think that this run in general has pushed the cold back sightly 

[Vikos]

1 minute ago, Skullzrulerz said:

Not to mention we have this shortwave business to get around too as well 

Starting to think that this run in general has pushed the cold back sightly 

Classic GFS-style for me: predicting smthg big in fi, than swinging back or delaying it with every new run a bit more, until just a cold fart remains. Only hope: the big patterns this season are quite better then the last years have ever been...

[LRD]

The 6z GFS spaghetti had a brief boost in the 850 temps on 22/23 Dec

That's been ruthlessly crushed on the 12z (note - this is not yet full set) replaced by a proper divergence around the 22nd (the op taking the warmer route temporarily) before most take a tumble from Xmas Eve onwards

Something could well be afoot. Maybe

[alexisj9]

10 minutes ago, Skullzrulerz said:

Not to mention we have this shortwave business to get around too as well 

Starting to think that this run in general has pushed the cold back sightly 

I was talking about the gem here, it has the USA low come over us bring very mild air. GFS run somehow doesn't look to bad.

[MATTWOLVES 3]

Plenty of positives from those ens again..always best to hold fire until we have viewed them also..I would say 70% chance of colder Xmas,and a 50/50 chance of further cold scenario's beyond this point..all eyes on the ECM then the 46 later on...come on old misely guts EC bring us some cheer..

Edited December 14, 2020 by MATTWOLVES

[Kirkcaldy Weather]

36 minutes ago, Kirkcaldy Weather said:

It’s the main area to watch over the next week or so, it’s the big nor’easter,snowstorm which is set to impact the NE USA on Wednesday/ Thursday (see my snow and ice twitter thread) we have seen these systems cause quite a bit of confusion among the models over the years usually 2 options either it can go north as it moves across the Atlantic and bring the more typical Atlantic wind and rain (similar thing happened a few winters ago with the failed easterly ) or it can go to the south / south west of the UK and that’s usually something I keep a look out for as majority of the time u get a pressure rise to the north and can lead to an easterly - right on cue the latest gfs hinting at that. 

This ensemble is a lovely example (some others also trying for a similar pattern) 

[Panayiotis]

The GFS 12z run is something that I’ve been looking out for the last few days and it’s great to finally see it being modelled.

Pressure rise to the west > northerly > north-easterly > high topples over > rise in pressure over Scandinavia > easterly 

The PV towards the end does ramp up which flattens the pattern but if we get energy underneath/weakened PV then it’s game on. Watching out for this evolution over the next few days...

 

Edited December 14, 2020 by Panayiotis

[Skullzrulerz]

32 minutes ago, Vikos said:

Classic GFS-style for me: predicting smthg big in fi, than swinging back or delaying it with every new run a bit more, until just a cold fart remains. Only hope: the big patterns this season are quite better then the last years have ever been...

Indeed I have seen this before sadly and I can only fear it will happen again 

Also of note this GFS 12z was a cold outlier

[frosty ground]

4 minutes ago, Skullzrulerz said:

Indeed I have seen this before sadly and I can only fear it will happen again 

Also of note this GFS 12z was a cold outlier

Was it thou?

[chris55]

38 minutes ago, LRD said:

The 6z GFS spaghetti had a brief boost in the 850 temps on 22/23 Dec

That's been ruthlessly crushed on the 12z (note - this is not yet full set) replaced by a proper divergence around the 22nd (the op taking the warmer route temporarily) before most take a tumble from Xmas Eve onwards

Something could well be afoot. Maybe

That’s the short vs long ensembles there, confused me for a second! 

[TSNWK]

6 minutes ago, Skullzrulerz said:

Indeed I have seen this before sadly and I can only fear it will happen again 

Also of note this GFS 12z was a cold outlier

Incorrect. Mid to bottom of pack and leading the way nicely at the end I felt

[chris55]

2 minutes ago, frosty ground said:

Was it thou?

There’s the correct comparison.

[Mucka]

As ECM rolls out a quick look back at GFS 12z ensembles.

Here is optimal mean chart for Atlantic blocking, it is not quite as good as previous runs but suggests a cold snap over Xmas.

For those still learning how to read the various charts; 

for deeper more protracted cold, at least with any initial Polar air incursion, we would want that "bump" in the Atlantic reaching toward SW Greenland to be better defined, more a prong than a bump, and to reach further N into the heart of Greenland and most of all to be slightly W of Greenland.

The mean above suggest a toppler where the ridge instead of building into Greenland "topples over" due to Atlantic  shortwave lows developing just tot he SW tip of Greenland and pushing E preventing the ridge building N and flattening the pattern as ridge  collapses toward the UK and Europe which cuts off any Polar feed.

In some circumstances the ridge doesn't fully topple, if there is low pressure in NW Europe to prop it up or a ridge reaching back from Scandinavia which can produce an Easterly but 9/10 it will bring a miler W flow back in.

The caveat here is that mean charts need to be seen as exactly that, a mean of possible outcomes, not necessarily the most likely outcome on the day, and the further out they are the more diluted the signal becomes since it is often an either/either scenario where none of those scenarios are actually represented by the mean as it shows a an amalgamation of them both.

[Tim Bland]

^^ give it a few days and watch that mean improve. It will never show a defined ridge on a mean 10 days out!

[Allseasons-Si]

Love the evolution of the control run...

and the gefs ens

 

 

[Mucka]

4 minutes ago, Tim Bland said:

^^ give it a few days and watch that mean improve. It will never show a defined ridge on a mean 10 days out!

I thought I made that Perfectly clear Tim.

Another way to look at it is that if less ensembles went for a toppler and stronger ridge then that that mean ridge would better show the characteristics I described if we want to see a cold spell develop over Xmas rather than a more diluted version.

Edited December 14, 2020 by Mucka

[Kentish Snowman in Yorks]

4 minutes ago, frosty ground said:

Was it thou?

Not an outlier.  Towards the colder end of the ensembles though.

My twopence worth is that the GFS is far more reliable with Northerlies than Easterlies so my confidence for a Northerly of sorts on the big day is increasing.

Any Easterly shown thereafter should be taken with a truckload of salt though as I think we could just as easily end up with a toppler rather than the GFS evolution.

Let's see what the latter stages of the ECM brings....

[IDO]

ecm and gfs at d6:

Both have a similar perspective as to the low on the jet and it merging with the trough. Great to see continuity cross-models at this range. We shall see how the ecm deals with the Atlantic ridge?

[Ice Day]

Very nice GFS this afternoon., with plenty of cold GEFS as well.  I'm liking the direction of travel over the past couple of days.  Hopefully the ECM doesn't sour the mood in here!

[LRD]

7 minutes ago, chris55 said:

That’s the short vs long ensembles there, confused me for a second! 

Yep - I do say 'note - these are not the full set'

[northwestsnow]

Squeaky bum time at 144....

Cmon EC give us some cheer God knows we deserve some surely.

Edited December 14, 2020 by northwestsnow

[Allseasons-Si]

4 minutes ago, Ice Day said:

Very nice GFS this afternoon., with plenty of cold GEFS as well.  I'm liking the direction of travel over the past couple of days.  Hopefully the ECM doesn't sour the mood in here!

Are we seriously looking at a prolonged cold spell here instead of a snap?

there's every possibility looking at those uppers.

Edited December 14, 2020 by Allseasons-si
typo

[LRD]

19 minutes ago, Skullzrulerz said:

Indeed I have seen this before sadly and I can only fear it will happen again 

Also of note this GFS 12z was a cold outlier

GFS 12z wasn't an outlier. On the chillier side of things but not an outlier at all. I was surprised to find it wasn't

[Scott Ingham]

4 minutes ago, Allseasons-si said:

Love the evolution of the control run...

and the gefs ens

 

 

The end of that control run is where I expected us to be Christmas week with Greenland heights more prevalent after that in my head. I've never had Greenie heights being the first full story. In my head that was chapter 2 with retrogression and then west based NAO coinciding with PV intensification prior to a warming kicking in. But we'll see. What we know is amplification is being picked up on off the back of background signals and a lot of roads leading to Rome

[BLAST FROM THE PAST]

Nothing has changed, no reason why ECM won’t continue cold theme.  But then again .  Cold blast (beast I said but ok with a gruffalo) for Xmas on my sig since September...timing remains the same and hasn’t changed...we close in...

 

BFTP