Model output discussion - The run up to Christmas

[Bartlett High]

We're definitely due a prolonged cold spell...a repeat of 1947 or 1963 would be nice!!

....

[Daniel*]

I think it’s important to take stock of how far we’ve come the GFS model has its faults but it has been the leader in this situation while ECM and UKMO went flat the GFS caught retrogression signal first - the UKMO has performed poorly not only being last to go with low on 23-24th but also sharpening Atlantic ridge. GFS has been broadly identical for the last 9 models run that is utterly extraordinary and should be recognised more even to turn out wrong I’d still say good effort. Given it’s notoriously inconsistent, that suggests something unusual is happening. I think the last time I remember it like this was in 2010. But there wasn’t so much uncertainty it was very much locked in however now models appear to be converging all being well today should be a very good day, as I said early this week we should get an answer. 
 

We have charts like this just 6 days away.... there’s no reason to be downbeat the long term prognosis looks great, unless your knocker’s sidney and have yet to gather his nuts.  

[Stu_London]

2 minutes ago, Bartlett High said:

We're definitely due a prolonged cold spell...a repeat of 1947 or 1963 would be nice!!

....

More difficult with background warming, but as Dec 2010, Mar 2013 and Mar 2018 proved - not impossible.

Maybe when the gulf stream finally chucks in the towel - they will be more frequent

[Scott Ingham]

6 minutes ago, Stu_London said:

I noticed a few similar models scenarios cropping up in October and November that had shades of 2010 - however, 2010 was a one in 50 year event, even disregarding background warming. 

I'd be happy if 1990/91 proved a good analogue match - I don't know if there was a SSW in Jan 1991, so i might be talking rubbish.

Its the fact it was a moderate la nina the qbo was in a descending positive phase and the heat in Russia and Asia in the preceding summer was similar. I believe this heat creates higher than normal pressure in Asia driving torque events and a rise in AAM

[Scott Ingham]

12 minutes ago, Allseasons-si said:

That is a good set of gefs ens@-5.

 

I like the coldest plunge from the 2nd of january assosiated with the next expected rise in momentum. Each phase seems to get a little closer to producing colder weather. The colder ensembles on there what's the general synoptic pattern? Greenland high, Icelandic High? 

[Daniel*]

If you were curious what @mulzy was going on about regarding EPS...

[Zak M]

7 minutes ago, Bartlett High said:

We're definitely due a prolonged cold spell

I wonder how many times that has been said in the past few years...

The last week of December and into January is almost certainly going to be colder than average, so while it may not be prolonged, it is in most peoples eyes better than constant zonality. I'm not too focused on any specific details at this stage - these include 850s, places that will get snow etc. It's simply just too far out and will obviously chop and change. I will sometimes post them though if it's stonking, just because I always focus on the positives, not the negatives.

Great model watching to be had though, especially with what's going on in the world. It definitely has been an entertaining past few days reading all posts from the knowledgeable members. @Scott Ingham especially - good job mate. If only I was knowledgeable.

Night all. Whatever the models show, I wish you all a Merry Christmas and a Happy New Year.

[Fourty Point Three Degrees]

You shouldn't get too carried away with SSWs, they may boost the likely hood of a cold spell but cold spells are not always the case. Wasn't there a SSW in early 2019 which failed to deliver. 

[Scott Ingham]

19 minutes ago, Zak M said:

I wonder how many times that has been said in the past few years...

The last week of December and into January is almost certainly going to be colder than average, so while it may not be prolonged, it is in most peoples eyes better than constant zonality. I'm not too focused on any specific details at this stage - these include 850s, places that will get snow etc. It's simply just too far out and will obviously chop and change. I will sometimes post them though if it's stonking, just because I always focus on the positives, not the negatives.

Great model watching to be had though, especially with what's going on in the world. It definitely has been an entertaining past few days reading all posts from the knowledgeable members. @Scott Ingham especially - good job mate. If only I was knowledgeable.

Night all. Whatever the models show, I wish you all a Merry Christmas and a Happy New Year.

Thanks mate. Anyone is capable. Just work out what you dont know and use google or ask questions. Theres enough papers out there just on the net tbf!!

[Kasim Awan]

Just checked and the GFS op has sided towards the solution I was discussing yesterday, lower heights over Greenland and trough energy sliding south east. Less clean wave break. This continued cold source also means uppers are colder on the run. This had some support from ens. Will be interesting to see how the eps deals with the wave break.

[Iceaxecrampon]

00z

After Sunday’s fun and games GFS chucks us an Easterly in.

 

 

Edited December 21, 2020 by Iceaxecrampon

[Kasim Awan]

GEM also in with excellent polar low injection... permitted by weaker GL heights.

 

 

[Daniel*]

Fantastic charts. It’s not a biggie not having a Greenland high in fact these solutions appear to be more wintry and continental, the block appears to be self sustaining with waves of amplification coming up eastern seaboard - highly atypical times in atmosphere. 

[Daniel*]

The WAA over Greenland which forms Greenland high removes a strong cold air avenue take 12z which had a pretty Greenland high but unimpressive uppers, on this morning 00z we have a feed from cold Greenland which is beneficial with getting colder air.

Edited December 21, 2020 by Daniel*

[Daniel*]

The UKMO is very good could we manage a link up there? Has more pronounced blocking in Arctic compared to the GFS.

[Griff]

37 minutes ago, Daniel* said:

The UKMO is very good could we manage a link up there? Has more pronounced blocking in Arctic compared to the GFS.

Hang on... Isn't this potentially snow cold? 

 

[Griff]

Now I know some rather irritating Welshman now based at the base of the Chilterns has been banging on for days about the old Arctic high linking up with the Atlantic... Or perhaps it's just model induced insomnia... 

I was going to post some pretty 240s but the 144 are worth a  

[tight isobar]

49 minutes ago, Daniel* said:

The UKMO is very good could we manage a link up there? Has more pronounced blocking in Arctic compared to the GFS.

The ukmo is great this morning.. gfs still an 8/10 overall... over to the EC!

[carinthian]

Morning all. Good agreement between UKMO and GFS at 144t. Maybe UKMO speeding up the advance of the cold front on Boxing Day. Chance of snowfall in parts of SE Britain now increases to 30% based on the formula I mentioned yesterday from 29th December. Looks like the low will become elongated just to the east of the British Isles as we head towards the New Year with its centre close to the Low countries. Not a bad place to produce a prolonged colder spell.

Should get an up-date in an hour or so from the portal team over here.

C

 

[Griff]

57 minutes ago, Daniel* said:

The UKMO is very good could we manage a link up there? Has more pronounced blocking in Arctic compared to the GFS.

I watched a Gavin P video at least a month ago arguing the case for needing the PV over towards the Arctic and away from the Americas, seems to be some suggestion that this is happening.... 

FYI I'm loving the regulars' continued devotion and enthusiasm on the often challenging and disappointing hunt for the cold! 

Nice work

[Daniel*]

15 minutes ago, Griff said:

Hang on... Isn't this potentially snow cold? 

 

Cold enough for snow I reckon, probably some scattered flurries along eastern/southeastern counties on Xmas day pressure is a bit high for widespread activity. 
 

Christmas Eve interests me more low shown to track east over Normandy and colder air encroaching rain to snow potential in S/SE? 

It 

[Griff]

46 minutes ago, Griff said:

Now I know some rather irritating Welshman now based at the base of the Chilterns has been banging on for days about the old Arctic high linking up with the Atlantic... Or perhaps it's just model induced insomnia... 

I was going to post some pretty 240s but the 144 are worth a  

ECM 144

 

... Right off to tier 4 for some essential work, wish me luck. 

Edited December 21, 2020 by Griff

[Daniel*]

Much better with low further E/SE quite a lot colder....

[Kasim Awan]

ECM has a muchhh flatter Greenland ridge. As explained this is a positive, allows for a build in low heights to our east. Please don't misinterpret this as a negative. It is actually a potential route to prolonging cold.

[Kasim Awan]

I find use of the "laughing" emoji without any discussion leaves me a little confused @matthugo

P.s., I'm not stating this solution is favoured within the model bias - the gfs' dealing of the GL high is most likely to verify. However, in model analysis consideration of other solutions is very useful.