Model output discussion - Closing in on Christmas

[Jason M]

2 minutes ago, Tom Jarvis said:

Chaps we have differences at t120 which greatly affect the pattern afterwards we need to watch this circled low for what it does before we can properly understand what is happening going forward. 

This is an interesting feature that's been floating around the output for a while now. It may be one of those things that causes some local short term entropy but actually has little bearing on the final destination. I just don't see this as being significant in the broader scale picture. That said, I watch with interest in the hope that I'm proved wrong. Lets see if the pub run has been on the sauce tonight.

[MATTWOLVES 3]

10 minutes ago, Mike Poole said:

The ECM EPS mean (the one we mortals see) has given some probability for cold scenarios for quite a while, and still does so today. Given the massive upfront uncertainty, highlighted in earlier post, do you think that a lower resolution model (which I assume the 46 is, happy to be corrected if not) will have a better idea, Matt?

Mike im not sure on the resolution bit...I've only viewed out till end of the month so far on the mean..  I will run through all 50 member a little later and give you more of an update mate..

Looks settled into the first week of January...Still keen to have low Heights around Iceland.. 

Edited December 17, 2020 by MATTWOLVES

[Tom Jarvis]

1 minute ago, Jason M said:

This is an interesting feature that's been floating around the output for a while now. It may be one of those things that causes some local short term entropy but actually has little bearing on the final destination. I just don't see this as being significant in the broader scale picture. That said, I watch with interest in the hope that I'm proved wrong. Lets see if the pub run has been on the sauce tonight.

Jason look through the 12z run of the ICON, the low is key as it helps keep the high propped up and is an linking path for lows to undercut the high. 

[Mike Poole]

11 minutes ago, Tom Jarvis said:

Chaps we have differences at t120 which greatly affect the pattern afterwards we need to watch this circled low for what it does before we can properly understand what is happening going forward. 

I disagree, it is this low or couple of lows that is causing the problem, ICON 18z T120:

[stodge]

1 minute ago, Tom Jarvis said:

Jason look through the 12z run of the ICON, the low is key as it helps keep the high propped up and is an linking path for lows to undercut the high. 

Oddly enough, it was being floated as far back as Monday by a couple of the models and then dropped as it was phased in to the circulation of the current LP. It's an interesting evolution but as I recall it didn't end well in terms of cold (surprisingly). 

[Jason M]

2 minutes ago, Tom Jarvis said:

Jason look through the 12z run of the ICON, the low is key as it helps keep the high propped up and is an linking path for lows to undercut the high. 

Yep, get that. 18Z ikon runs out to 120 hours so its impossible to be definitive but my own (possibly wrong)  view is that we still end up with similar to what's being shown elsewhere by day 8 or 9. Either way, we will probably know soon enough. 

[sheikhy]

Gfs following ukmo/icon at 96 hours?

[northwestsnow]

1 minute ago, sheikhy said:

Gfs following ukmo/icon at 96 hours?

Yep..

GFS has put the breaks on the low(s) and made a move towards ukmo....

[blizzard81]

2 hours ago, Bricriu said:

It's not a good sign when the CFS is being referenced. This is the same CFS that was showing very impressive upper around Christmas a while back.

I agree that cfs is to be treated with caution. However, it has touted a cold Christmas for a while now and it certainly looks cold from what I am seeing in the modelling. Glacier Point often quoted and cited the cfs weekly anomalies in his analysis and if they are good enough for him then they are certainly good enough for me. 

[chionomaniac]

Been busy with work so unable to post much last few days. Main thing that is important, is that whilst background signals remain the same, then so do the chances of something wintry greater than a toppler remain. Strat is disconnected still, tropical movement in our favour is still looking likely too. So, keep watching. Upper strat disruption is winding down with days rather than being static at the end of FI. Whilst that continues, then this increases the chance of a wave 1 upper SSW displacement.  If this coincides with MJO  movement then chances of lower wave 2 increase, and this is likely to be more productive with upper strat attack. When we get upper vortex intensify and this propagates to the trop then hope fades. Not looking likely presently. 

[northwestsnow]

Which leaves EC isolated and the choreography to me anyway,suggest ukmo is on the money here...

[Mike Poole]

This is getting ridiculous now, GFS 18z T114, compared with GEM and UKMO at T120 from 12z, uncertain feature circled on GFS:

Getting this low right is pivotal to getting the degree of amplification right in the Atlantic, and everything else that follows on from it.  

[sheikhy]

Wow!!!that is some serious move towards ukmo!!if it shows the same in the morning expect ecm to follow!!colder air much further south!!

[northwestsnow]

18z..

126

12z

132

[swfc]

2 minutes ago, northwestsnow said:

Which leaves EC isolated and the choreography to me anyway,suggest ukmo is on the money here...

Choreography, are you the Andrew Lloyd webber of netweather anyway another gfs run another change. See how all three main models sit Tom. 

[sheikhy]

Just now, northwestsnow said:

18z..

126

12z

132

Look at the amplification in the atlantic as well!!got the best of both worlds so far on this run!!!colder air way further south in the uk and then the amplification in the atlantic!!

[Ultima Thule]

18z better to my eyes, high building N

[Griff]

5 minutes ago, northwestsnow said:

18z..

126

12z

132

I'll be told I'm wrong by somebody no doubt , but looks an improvement. 

Edited December 17, 2020 by Griff

[Allseasons-Si]

Finally the gfs breaks away from that trough in the Azores and takes the UKMO route...

126 18z v's 132 12z

more downstream trough resulting  in better WAA into west Greenland.

 

[blizzard81]

1 hour ago, Tim Bland said:

16-30 Day GFS ensemble has Greenland ridging into Jan. 

Which ties in nicely with cfs week 3 which I posted earlier. I attach again. 

[Vikos]

Oh, this butterfly effect... gfs swings

[northwestsnow]

A swift change in 850 profile now it has trapped the low....

18z..138

12z 144

[chionomaniac]

It’s a definite improvement griff

[Matt H]

Cold northerly flooding in for Christmas Eve, what an improvement!

[MATTWOLVES 3]

Blooming hell trying to go through 50 ensembles is head banging...i pointed out that the mean was not great regarding cold..but there are a fair few colder members out towards the 1st week of January...some have serious Heights to the North and low Heights over Southern Europe.. I've just viewed a few runs with sub zero air in place of us...

So early conclusions....plenty of options on the table and I wouldn't rule out any outcome, Now I see why Exeter forecasts are low confidence into next year, we could make a case for anything goes..I wouldn't rule out really mild,or really cold tbh...but obviously I would be happier with the cold.

 

Edited December 17, 2020 by MATTWOLVES