Model Output Discussion - Into the new year

[Kasim Awan]

4 minutes ago, Weathizard said:

Let’s be careful, fantastic GFS 12z but DO NOT go and tell your families snow and cold is coming  

The way that 4 runs in a row have been so significantly different suggests we should be very careful, those height rises around Iceland are notoriously troublesome. 
 

When I woke up this morning and saw the laughable difference between the 0z and last nights 18z I said to be very wary with the GFS and I’d stand by that for now until we see some c3onsistency.

The flatter GFS run was one outlier in a trend as opposed to a divergence in the output.

Edited December 27, 2020 by Kasim Awan

[Ali1977]

I was going to cherry pick a few day 9 ENS but all are great. Expect even stronger wording ref cold/snow from the METO long range if all’s still looking like this in the morning - this isn’t a few days of cold being forecast here, prolonged job and the SSW hasn’t even kicked in !!

[That ECM]

Ten day mean

[Tim Bland]

Only a few stragglers now...

[Penrith Snow]

22 minutes ago, Jason74 said:

I'm still not allowing myself to get too drawn in by the charts. 

We all say that but we know we will be.......

[Allseasons-Si]

These at 240 inc the gefs mean...

gfs,gfs/p,control,GEM and gefs mean.

stamps and gefs ens at 240

i think that is pretty good consistency,...from the 12z anyway

 

Edited December 27, 2020 by Allseasons-si

[kold weather]

3 minutes ago, Kasim Awan said:

The flatter GFS run was one outlier in a trend as opposed to a divergence in the output.

To be fair though there was a trend to flatten out the pattern yesterday, every single model moved quite alot from the previously very amplified pattern to a much flatter pattern. not all were bad per say, but there is a big difference between raging upper high seen on the ECM on the 24/25th December, to the much weaker and more Atlantic based feature seen yesterday.

Since then the models have all again shifted back towards that original setup, though it is actually quite different in how it gets there.

Caution is defintely advised, I've been here 16 years and seen such features shift around  before at far shorter notice.

*However* I've not often seen such good global set-up go wrong from this point very often, just a couple of times from my memory. I just feel caution is probably still wise at this point until we have a longer period of consistency. it is GOOD news though to see several models have a very similar patrern from 120hrs onwards.

[Kasim Awan]

1 minute ago, That ECM said:

Ten day mean

Yes, shades of t w e n t y t e n 

[ScottSnow]

20 minutes ago, kold weather said:

Depends on he EXACT wind direction, ENE typically need lower than -5c because the water temperatures tend to warm up the surface flow somewhat and this makes things increasingly marginal the warmer the air is in the lower atmosphere to begin with. Of course the colder the SSTs the less modification there is, but also tends to lead to weaker precipitation.

Now if you can get more of an ESE then typically the air travels less time over water and typically will be colder at the surface, therefore you get away with having higher temperatures at 850hpa, in exceptional circumstance over snow fields right upto 0c in theory.

Yes when the wind is coming from a east or north easterly direction we need lower 850s. If it is coming from a south easterly direction it is blowing in from the continent and that’s when lower 850s will suffice.

[Daniel*]

26 minutes ago, kold weather said:

The models really are being very inconsistent at the moment, which would suggest to me that caution is needed, they could very easily swing back again tomorrow to what they showed yesterday.

With that being said I was a little suspect that the models were way over-correcting yesterday, and they often do that only to have to row back to a less extreme version of the previous pattern. Either way the models today have locked back onto a cold pattern and long may it stay that way.

I think you should change that to GFS. The Euro model hasn’t been inconsistent and nor its ens mean. Very steady indeed. 

[Mike Poole]

18 minutes ago, Battleground Snow said:

This showing on the para for the 4th of Jan too.

I'll let the more knowledgeable than me decide if this will split or not

 

The GFS para has been consistently showing this very pattern for quite a few runs now.  Be interesting to see how it pans out.  

I’m late to the party today, great to see the awesome output from UKMO, and GEM and GFS in particular.  Look forward to the ECM in half an hour.

[Met4Cast]

I laughed when @Scott Ingham said last week that this up-coming spell could be potentially "historic" in terms of length of below average temperatures.. I'm not laughing anymore. 

The GH block is well supported within the teleconnections, I feel the GFS might be "slightly" too progressive with the speed it builds it in, but not by much. The GEFS mean is a thing of absolute beauty and more importantly, is well supported within the EPS clusters.

[Northern Sky]

15 minutes ago, Met4Cast said:

GEM broadly similar to the 12z GFS, if a little messy..

HUGE upgrade on the GEFS mean too, cannot wait to see the entire ensemble suite, I suspect there will be a few very cold runs in there. 12z plays out pretty much how I'm expecting, albeit on a slightly faster timescale.

Brief relax of the pattern early January (albeit staying blocked in this case) before a resurgence of heights into the 2nd week as the +EAMT event kicks into action. Cold > getting colder > into the freezer. 

That's before any potential SSW..

Is there a possibility the strat warming could have the opposite effect and have a detrimental impact on our chances for cold.

Sorry to put a fly in the ointment but hasn't that happened before?

[MATTWOLVES 3]

I tell you what folks..looking at some of the ens,you would think a reversal had already taken place,and the Estly feeds were already building..obviously with the correct outcome,those 850s will become severe.

A COLD WEEK AHEAD..CHECK

SNOW OPPORTUNITIES...CHECK

THE ATLANTIC HAS LOST THE PLOT,AND DOESNT KNOW WHERE TO GO....CHECK

POSSIBLE MAJOR SSW ABOUT TO OCCUR...CHECK.

A WINTER OF MUCH MORE PROMISE THAN RECENT YEARS....CHECK,CHECK, CHECKMATE.

[Catacol]

Well I think the gfs is getting a bit ahead of itself in terms of speed of evolution - it ought to take a day or 2 longer than this....but this outcome fits with ECM earlier and the drivers listed earlier. All good. 

[Met4Cast]

2 minutes ago, Northern Sky said:

Is there a possibility the strat warming could have the opposite effect and have a detrimental impact on our chances for cold.

Sorry to put a fly in the ointment but hasn't that happened before?

Yes.. the current blocky pattern is trop led rather than Strat led. In theory an SSW could disrupt the pattern and shift it putting the UK on the milder side of the block.. on the other hand it could allow the pattern to double down and extend favourable blocking. We're a long way away from knowing what impact an SSW is going to have.

Just now, Catacol said:

Well I think the gfs is getting a bit ahead of itself in terms of speed of evolution - it ought to take a day or 2 longer than this....but this outcome fits with ECM earlier and the drivers listed earlier. All good. 

Ha! Great minds, just said exactly the same thing albeit with far more words.

[Mucka]

Somebody probably already posted it but GFS 12z Op is cold until the end of time (available on Wetter')

 

Those 850's are -8 to -10 BTW

Edited December 27, 2020 by Mucka

[kold weather]

3 minutes ago, Northern Sky said:

Is there a possibility the strat warming could have the opposite effect and have a detrimental impact on our chances for cold.

Sorry to put a fly in the ointment but hasn't that happened before?

Certainly possible, but that tends to be a bigger risk when you already have a fairly west based -ve NAO.

Ironically the current evolution with the HP semi-toppling but failing towards N.Europe buts it in a really strong position for a -ve AO to properly develop and sync up with a strengthening -ve NAO and develop a really textbook looking Greenland high.

Still a few hurdles to get over yet but looking promising.

[ScottSnow]

4 minutes ago, kold weather said:

To be fair though there was a trend to flatten out the pattern yesterday, every single model moved quite alot from the previously very amplified pattern to a much flatter pattern. not all were bad per say, but there is a big difference between raging upper high seen on the ECM on the 24/25th December, to the much weaker and more Atlantic based feature seen yesterday.

Since then the models have all again shifted back towards that original setup, though it is actually quite different in how it gets there.

Caution is defintely advised, I've been here 16 years and seen such features shift around  before at far shorter notice.

*However* I've not often seen such good global set-up go wrong from this point very often, just a couple of times from my memory. I just feel caution is probably still wise at this point until we have a longer period of consistency. it is GOOD news though to see several models have a very similar patrern from 120hrs onwards.

It does seem that the models are starting to come together for a sustained spell of cold weather. I notice as each day goes by the cold from East Siberia/Asia is starting to move westwards on the models. We need this trend to continue.

This week would of been great if we had a cold pool to tap into.

We have been led up the garden path many times before only for things to come crashing down however as you say the background signals are all stacked in our favour this time with the added bonus of a potential SSW.

 

[Updated_Weather]

5 minutes ago, Met4Cast said:

I laughed when @Scott Ingham said last week that this up-coming spell could be potentially "historic" in terms of length of below average temperatures.. I'm not laughing anymore. 

The GH block is well supported within the teleconnections, I feel the GFS might be "slightly" too progressive with the speed it builds it in, but not by much. The GEFS mean is a thing of absolute beauty and more importantly, is well supported within the EPS clusters.

Respect to you.

 

least your honest. Very exciting times ahead.

[Scott Ingham]

3 minutes ago, Met4Cast said:

I laughed when @Scott Ingham said last week that this up-coming spell could be potentially "historic" in terms of length of below average temperatures.. I'm not laughing anymore. 

The GH block is well supported within the teleconnections, I feel the GFS might be "slightly" too progressive with the speed it builds it in, but not by much. The GEFS mean is a thing of absolute beauty and more importantly, is well supported within the EPS clusters.

It is a bold claim i can understand why you would do and last week i wasnt all in really i just knew the next rinse and repeat would be more favourable due to it coinciding with the vortex displaced over to siberia and the mean wind speeds on there way down at the same time.

I agree with you on speed i expected to start to see effects on the 5th leading to retrogression to Greenland nearer the 8th or 9th. Maybe we do need to be careful if the gfs has over reacted and we see a day or two of delay not to think its not going to happen but synopically its completely realistic. 

Whats your views on stage 4. The tropospheric placement after the ssw? 

This is a weak area for me 

[Scott Ingham]

9 minutes ago, Catacol said:

Well I think the gfs is getting a bit ahead of itself in terms of speed of evolution - it ought to take a day or 2 longer than this....but this outcome fits with ECM earlier and the drivers listed earlier. All good. 

I agree Catacol just replied as much to @Met4Cast he thinks the same as well

[northwestsnow]

320 members online!!

Somethings brewing!!

Come on EC !!

We want more !!

[Gadje]

35 minutes ago, Faronstream said:

I mean for really wintry wise conditions, not about what you need for snowfall.

I think some posters might have missed your location. For us cold starved paupers in the UK a meagre -5C  850 hitting out shore get's our snow hopes up. Below - 12C might be magic to you it is a near mythical to us. But we dream.

[Mucka]

12z deep FI now available meteoceil, very cold.