Model output discussion - Jan 3rd onwards

[ItNeverSnowsInWindsor]

First signs of SSW can be seen in the latest GEFS ensembles with the odd member hitting -15c!

Need the numbers of very cold options to increase in subsequent runs!

[Decemberof2010]

7 minutes ago, ICE COLD said:

I’ve always liked P2 . Always seems to verify the most

JFF of course, but can someone with more knowledge than me tell me what temps that would produce at the surface? 

[SLEETY]

14 minutes ago, Weather-history said:

GFS 12z Christmas Day chart for today

ECM 12Z

GEM 12z

 

And what actually happened

Not bad from GFS  but ECM thats why its latter ouput should be largely ignored I mean What the ....

ppp

Perm 2 would be sensational max temps below Zero with heavy snow for many.

Edited January 4, 2021 by SLEETY

[Anti-Mild]

1 minute ago, Decemberof2010 said:

JFF of course, but can someone with more knowledge than me tell me what temps that would produce at the surface? 

I reckon that would give daytime temps of -5 or lower in favoured areas, nightime probs -15 easily, maybe even breach -20.

Not often -16 850HPa hits us.

[bluearmy]

whilst earlier spread frames show that the trough to our northeast may well affect us more than the op and mean show, the day 10 below shows that the mean upper ridge is strongly supported ...

 

 

 

 

 

 

 

[ICE COLD]

2 minutes ago, Anti-Mild said:

I reckon that would give daytime temps of -5 or lower in favoured areas, nightime probs -15 easily, maybe even breach -20.

Not often -16 850HPa hits us.

Yep would certainly be very cold . There’s actually a blob of -18 850s in Scotland . We can dream ay

[bluearmy]

6 minutes ago, SLEETY said:

Not bad from GFS  but ECM thats why its latter ouput should be largely ignored I mean What the ....

A merger of ecm and gfs would have delivered the correct chart ..... but how can you work out which bits to choose ! 

[ScottSnow]

53 minutes ago, Tim Bland said:

Stay at 3 or 4? It’s been more like 5 or 6c for half of England? Can hardly call it a Cold spell at all in the south

I got laughed at last week when I stated that this was more of a ‘cool’ spell rather than a ‘cold’ spell. Lying snow is mostly confined to higher areas. Here in the north east inland areas with height have done quite well.

Looking at the models most of us will be lucky to have any meaningful snow before mid January.

Some people on here were saying that this cold spell was going to be in the UKs all time top ten. I never saw any evidence in the models that this would be the case. If you voice caution on the models you get shot down on here now and in my opinion it stifles debate.

From what I can see we have missed the boat this time mainly due to not enough cold pooling in our hemisphere. It looks like it will get a little milder next week although I don’t think it will be excessively mild. The models still have potential and hopefully this will manifest itself as the background signals are promising.

Hopefully we will see the benefits of the SSW and later in the month we will get the right Synoptics but this time with the cold pool in place to tap into. The cold air from East Asia is starting to transfer west on the models now.

I am no expert and I love cold and snow but shouting down anybody who adds a voice of caution or doesn’t interpret the models as a snowy cold nirvana I believe is the wrong route to go down as a forum.

[chris55]

20 minutes ago, ICE COLD said:

I’ve always liked P2 . Always seems to verify the most

This chart needs a disclaimer for any newbies! Though it is a beautiful, beautiful chart!

(newbies reading, this is one member out of 30 that is run with purposely incorrect starting data showing the prediction at day 14)

 

 

[Griff]

As per Marco P and the Met tweet earlier, latest ecm zonal chart shows 2 events... 

 

[Osbourne One-Nil]

Please everyone - I'm very grumpy tonight so please make an effort to stay on topic. It's not hard!

[sebastiaan1973]

Latest EC46

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[sebastiaan1973]

This doesn't reflect a SSW we want to see. Just look how small negative NAO is.

[stodge]

Evening all

A chilly day here in lowland East London but the models were preparing to call time on the cold spell last evening. GEM and to an extent ECM were bringing in milder air by the end of the week while for GFS the milder conditions were postponed for a couple of days. With events in the stratosphere providing an intriguing contrast, would this be a pattern change for the rest of winter or a brief interlude - probably too early to tell but perhaps this evening will offer some clues (or perhaps not).

12Z GEM:  T+120 is Saturday and by then the NE'ly has been pushed south as the Atlantic ridge builds across the British Isles. To the north, a significant storm has developed close to Iceland. The airmass remains cold over the British Isles at this time. From there, the LP heads SE into Scandinavia and by T+180 is centred over Sweden with a secondary centre to the west of Norway. A N'ly air flow covers the British Isles with weak heights over Iceland extending SE while the previous Atlantic HP has continued south. A brief milder interlude is replaced by a new push of colder air from the north.  The evolution up to T+240 gets messier - the Azores based HP moves back NE to be centred over or to the west of Iberia with a weak Atlantic feature moving toward Iceland and a hint of heights over Scandinavia.  Milder air moves slowly east across the British Isles by T+240 but significant cold air sits just to the east.

12Z GFS OP - GEM is unconvincing but as we've seen recently, there's no jet to power deep Atlantic storm systems from west to east. It's more like a summer chart than a winter one in some ways. On then to the GFS OP. By T+120 the general pattern is in place - a more pronounced trough over the western Mediterranean and a new LP over Iceland with a small ridge of HP across the British Isles at this time. The air mass over the British Isles remains cold - -8 uppers in the south east and a new push of cold air approaching from the north west. The LP pushes SE to the north and north east of the British Isles and is over Denmark by T+180 with a N'ly airflow to its western flank. Heights to the west look insufficient to stop a new push from the Atlantic. Uppers remain chilly at -4 by T+180. I am of course wrong about the heights which develop to form a new anticyclone over or just to the south of the British Isles by T+240. The residual trough remains over Scandinavia and again the Atlantic is doing nothing slowly. As with GEM, milder air is slowly encroaching from the west by T+240.

12Z Parallel - for all its modernity, Parallel has thrown up some interesting solutions in recent days but with GEM and GFS OP unusually close at T+240, let's see if it goes down another path. No real surprises at T+120 but perhaps a more defined ridge into Scandinavia.  Indeed, Parallel does go a different route - the Icelandic LP fills more or less in situ and after a final flourish from the European trough, the HP builds in by T+180 settling conditions down as milder SW'ly winds reach the far north and west of the British Isles. However, by T+180 milder air is over or close to all parts. Not much changes through to T+240 with the HP intensifying over or to the west of Biscay and feeding mild SW'ly wins over all parts.  Just to note Shetland stays on the colder aide with -8 uppers.

12Z ECM - Parallel breaks down the cold spell more quickly than GEM or GFS OP as the Icelandic LP doesn't get involved. On then to ECM and no surprises at T+120. By T+192 it has also brought back the milder Atlantic air with the HP to the south west and the Icelandic LP having moved east toward northern Scandinavia and a new LP forming to the far west to the south of Greenland. After a final cold push at the weekend, milder air is back over all parts by early next week. The T+240 map is strongly anticyclonic but I don't see a raging northern arm to the jet at this time so do we get a hint of height rises to the north east as well? Maybe but for the moment the milder Atlantic air has won out.

Moving further into FI I offer, as usual, the T+312 and T+384 charts from GFS OP and GFS Parallel respectively.

As we saw last evening, one builds a huge PV back over Greenland and NE Canada and the other doesn't. I'll leave you to figure out which is which.

Looking elsewhere, 12Z Control is also very anticyclonic. Beyond that, the 10 HPA charts show the PV recovering into far FI with core temperatures back to -72 - it's not the size or strength you'd expect in mid January to be fair.

Conclusion: can we push the cold through the coming weekend? Possibly and especially if the Icelandic LP is a player but the clear theme is anticyclonic with the initial HP build to the south or south-west which allows milder Atlantic air to push across early next week. From there and in the absence of a raging Atlantic, we have to wait for amplification (Parallel hints at this in far FI) to push the HP further north. GFS OP builds a strong PV in far FI with which I'm struggling and perhaps we need to keep looking for signs of heights over Scandinavia as frigid air isn't too far away.  Many areas which have seen huge rainfall totals will welcome drier conditions and of course fog and frost can be issues with clear skies at this time of year but that's detail to be resolved.

[TSNWK]

3 minutes ago, sebastiaan1973 said:

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Oh dear.  If they are correct we best make the most of this week before we are subject to Atlantic troughing.  

[Tim Bland]

EPS confident of a return to average next week

[Chertseystreamer79]

5 minutes ago, Howie said:

oh my god 

Was the last ec46.....THE COLDEST EVER! difference a week makes....

 

 

Still all subject to change....too many influences to be sure of anything!

[Tim Bland]

Who’s up for a double dip?

[TSNWK]

Just now, Tim Bland said:

Who’s up for a double dip?

No thanks if the outcome is a displaced vortex in the Atlantic... Jeeze I do hope ECM have got this all wrong.  

[IDO]

1 minute ago, winterof79 said:

You do love to purvey bad news 

It is a bit of balance, as the Met Office also hinted today by saying it is a zonal La Nina -v- blocking from a SSWE. It is not a simple case that an SSWE will usurp the trop drivers as it is often portrayed, there have been SSWE's that are milder than they are colder. I suspect the strat will have a harder time than normal to imprint and may need further warmings to get the job done, sometime in late Feb for a full meltdown?

It appears from the Twitter'sphere that it will be about 10-days before the models can get to grips with the effects of the SSWE. The models have come to an agreement up to about d10, the mean of ecm confirms this:

 gfs d10>

I think we have to accept that the transitional phase, from around d7-12 will not favour the uk for severe cold. After that, who really knows?

[Jason M]

1 hour ago, Weather-history said:

GFS 12z Christmas Day chart for today

ECM 12Z

GEM 12z

 

And what actually happened

Pretty good effort by the GFS I'd say. Far from model chaos looking at tonight's day 10 charts across all the models they arrive at broadly the same place. Maybe one of those scenarios where the destination is known but the route to get there still has some bumps to sort out. Notice the GFSP thought about a beasterly, but after some thought, packed it off to Greece. Some things never change!!

[sebastiaan1973]

18 minutes ago, winterof79 said:

You do love to purvey bad news 

I love cold weather. But I was and I'm not optimistic. I try to be realistic.

[warrenb]

I am afraid the ecm 46 has clearly lost the plot, now if those anomalies were in reverse order it would make far more sense after an ssw 

[NeilN]

The thing is, these are predictions and I guess any outcome can come off. 

 

[Don]

1 minute ago, Mr Frost said:

Interesting run for sure though from an above average outlook perspective!

We all know how quickly these can flip - cold/snow lovers no need to panic. 

Fascinating model/chart/teleconnections viewing at the moment - loads to view and discuss! Great stuff! 

Had better make the most of this week's cold weather if those charts come off.  However, like you say, could well flip to very cold on the next update and the SSW could be making modelling very volatile.