Model Output Discussion - moving into Winter

[Chertseystreamer79]

Several people are typing!!!....says it all. 

[ICE COLD]

Get in there there gfs

[Mark wheeler]

Bank , Bank , Bank , Bank

[keithlucky]

45 minutes ago, Fozfoster said:

Another great post Edd,“this last bit of your post I quote because with climate change warming we get increased weather extremes, and maybe this cold could be extreme . I also think someone else alluded to this earlier. 

Tell that to Australians Americans Russians Chinese South Anericans all breaking cold records And near record Northern Hemphere snow cover.

[Snowy L]

Looks west based but absolutely no problem if the Iberian Low goes where it has on this run. Big chunk of that Siberian energy sent down to us before the Greenland High tilt and it's looking good.

[LightningLover]

Looks like the GFS really did get silly at the Pub!

[Geordiesnow]

Very good 18Z slightly better amplification and a cleaner northerly too boot. Sure if your nit picking on details you want it further south and east in the 120 to 144 hour range so its a slightly quicker and smoother transition to the colder air but no complaints from me. 

Hopefully the UKMO will come back on board with its ridge into Greenland in the morning. 

[Mark wheeler]

2 minutes ago, Chertseystreamer79 said:

Several people are typing!!!....says it all. 

I always see that but he never posts

[Allseasons-Si]

WOW,...get the cold in first and the polar lows will follow

[Eagle Eye]

Stratosphere'e looking a bit wavy 

[tight isobar]

Have a word ref!!.. absolute txt book aligned format blocking.. and Siberia puffing... what are these models smoking . Put on ya tuxedos.. we are going Michelin star  

Edited December 1, 2022 by tight isobar

[Singularity]

1 minute ago, Catacol said:

Does falling AAM matter when there is little to no top down forcing of westerlies and a significant block that cuts through the vertical layers a good way up is in place?

The AAM drop will initiate a poleward propagation of westerly momentum anomalies and they usually overpower blocking highs... but when one of those effectively extends well up into the stratosphere (in terms of positive geopotential height anomalies), that momentum can be diverted southward, resulting in a strong, flat jet stream that's well south of the UK.

That's what we're seeing in the modelling for later next week.

The thing is, this also encourages retrograde motion of longwave features to the north, such as blocking highs. So, we're left looking at whether that happens in one smooth transition, or 2+ steps that keep the UK in a cold weather regime for longer.

I expect the latter becomes more likely the stronger the stratospheric support for the initial blocking feature is.

This month, we also have the added possibility of a cold surge out of East Asia across the Pacific initiating new MJO activity, or something similar to it, over the tropical West Pacific sometime in the 2nd half. So, there exists a possibility that the HLB pattern gets reinforced, in which case it would become a very big deal how much the pattern has retrograded. At least some retrograde is pretty much inevitable, so I daresay the question would actually be whether there's been enough retrogression to place a blocking high close to our northeast (or even due north of us) by then.

Got way ahead of myself there, best concentrate on next week for a while yet!

[bluearmy]

5 minutes ago, TSNWK said:

Faster approach of the cold trough.. big test of the theroy that faster is more risk of it going more west of us….

Faster = bigger risk west base -nao does also rely on some other factors. If we get the pattern far enough south then most of the risk that the U.K. misses the deep cold disappears, even if the trough heads west somewhat 

the day ends much better than it started. Would be nice to see the 00z suites carry on the themes

 

[Catacol]

Shameless theft from Twitter - but a great image showing cold continuity in the medium term. Note on this EPS image that the trough has deepened out to our east. Much better than having it deeper out west. Again - looks like ongoing continental flow from the North through East quadrant ongoing. 

Those analog comparisons aren’t too shabby either…

Edited December 1, 2022 by Catacol

[Eagle Eye]

1 minute ago, Mark wheeler said:

I always see that but he never posts

We're going to get a full debriefing of everything in about an hour  that confirms that we're 100% going to see what our heart desires from this @several people . Can't seem to tag them .

[matty40s]

16 minutes ago, Kreftysoton said:

What models do the BBC use? Just watched the 10pm forecast and the temperatures are no lower than 4 or 5 in scotland nxt wed/thurs?  Down south its rain start of the week and 9 or 10 degrees???

Primark models

[Cloud 10]

Cut-off Greenland HP on the 18z which is a tough cookie.

 

[Ali1977]

Greeny high still going getting at day 8, getting stronger so could reload another Northerly to back up the first 

[Johnp]

8 minutes ago, sheikhy said:

Bloody good shot son at 156 hours!!!

Bloody good shot son at 156 hours!!!

Why are your posts always duplicating?

[damianslaw]

A much cleaner and quicker north easterly flow from GFS 18z this evening, this is now coming into the reliable 1201-44 hr timeframe. This is the limit timeframe to look at I feel in the days ahead, as once the cold arrives, short term sudden developments - frontal/trough/shortwave features can pop up out of nowhere, shallow low features giving sudden wintry precipitation out of nowhere,  indeed it becomes a nowcast.

We are now just about turning the point of no return - that one being cold is coming.

[Snowy L]

Greenland High actually getting reinforcements from Canada! Has the Atlantic ever been more dead than this.

 

[sheikhy]

Just now, Johnp said:

Why are your posts always duplicating?

Its bloomin net weather it keeps doin that

[Bats32]

GFS, get in there!

[blizzard81]

2 minutes ago, bluearmy said:

Faster = bigger risk west base -nao does also rely on some other factors. If we get the pattern far enough south then most of the risk that the U.K. misses the deep cold disappears, even if the trough heads west somewhat 

the day ends much better than it started. Would be nice to see the 00z suites carry on the themes

 

Yep, the 00z runs will be crucial

[chionomaniac]

3 minutes ago, Singularity said:

The AAM drop will initiate a poleward propagation of westerly momentum anomalies and they usually overpower blocking highs... but when one of those effectively extends well up into the stratosphere (in terms of positive geopotential height anomalies), that momentum can be diverted southward, resulting in a strong, flat jet stream that's well south of the UK.

That's what we're seeing in the modelling for later next week.

The thing is, this also encourages retrograde motion of longwave features to the north, such as blocking highs. So, we're left looking at whether that happens in one smooth transition, or 2+ steps that keep the UK in a cold weather regime for longer.

I expect the latter becomes more likely the stronger the stratospheric support for the initial blocking feature is.

This month, we also have the added possibility of a cold surge out of East Asia across the Pacific initiating new MJO activity, or something similar to it, over the tropical West Pacific sometime in the 2nd half. So, there exists a possibility that the HLB pattern gets reinforced, in which case it would become a very big deal how much the pattern has retrograded. At least some retrograde is pretty much inevitable, so I daresay the question would actually be whether there's been enough retrogression to place a blocking high close to our northeast (or even due north of us) by then.

Got way ahead of myself there, best concentrate on next week for a while yet!

Great post, and explains exactly why in plain English that this may well be a more than a transient cold outbreak.