Model output discussion 24/01/21

[sebastiaan1973]

1 minute ago, Griff said:

You might want to review the other models as the ECM is just starting to trend towards them, or am I missing something? Been some interesting 12z runs, you should check them out

Thanks. I will check them

[Griff]

Just now, sebastiaan1973 said:

Thanks. I will check them

[nick sussex]

The ECM doesn’t make it on this run this is because the displaced Azores high flattens too early .

For newbies just to explain in more detail . The two key features are the displaced Azores high and the building ridge to the ne .

Between both the energy from that UK troughing . The key to getting the ridge sw cleanly allowing the cold into the UK is a joint venture between the two key features .

The Azores high ridges nw , this delays the progression of low pressure out of the USA and Canada , it needs to remain amplified and sufficiently north at the same time because of that amplification the energy flow from the UK troughing is se not east . Combined with the forcing exhibited by the ridge to the ne the troughing over the UK weakens and eventually gives up the battle . The ridge can then extend further sw .

You can see from the ECM the displaced Azores high flattens and allows the low eastwards , this also means your energy downstream is moving more east than se .

Theres plenty of time for changes given this is really the start of the next drama ! Hopefully the cards will fall kindly this time .

[Vikos]

Well, EC12z repeated 00z and shifted the cold block westwards over to canada.

---->  

  --->

This ignites the cyclogenis. Where this ends up for NW-Europe, everybody should know.

Ok, still a long way to go, but atm things don't look primed. Not depressive, not sarcastic, just realistic.

[BLIZZARDMAN]

Don’t take anything in FI as facts, I was supposed to have a sleety mess according to most models on sunday this time last week but I did just fine! Upgrades nearly always appear nearer the time.

[Anthony Burden]

Still lot’s to be sorted out with the charts,chopping and changing GFS good tonight but will it

be different on the pub run,probably my take need to wait to at least the weekend for more

clarity.One thing for sure this winter has still plenty of surprises for us cold lovers.

[sebastiaan1973]

Perhaps this is the story of winter 2021. No real cold for large parts of NW-Europe despite many negative AO-days.

 

Edited January 26, 2021 by sebastiaan1973

[Vikos]

6 minutes ago, Anthony Burden said:

Still lot’s to be sorted out with the charts,chopping and changing GFS good tonight but will it

be different on the pub run,probably my take need to wait to at least the weekend for more

clarity.One thing for sure this winter has still plenty of surprises for us cold lovers.

Wouldn't put to much trust into GFS (op+P) atm

Edited January 26, 2021 by Vikos

[Daniel*]

8 minutes ago, Vikos said:

Well, EC12z repeated 00z and shifted the cold block westwards over to canada.

---->  

  --->

This ignites the cyclogenis. Where this ends up for NW-Europe, everybody should know.

Ok, still a long way to go, but atm things don't look primed. Not depressive, not sarcastic, just realistic.

One major detail you’re missing out there’s a high pressure cell on latest 12Z moving north up east coast that would block the very cold air from spilling out.

[Cold Winter Night]

6 minutes ago, Vikos said:

Well, EC12z repeated 00z and shifted the cold block westwards over to canada.

---->  

  --->

This ignites the cyclogenis. Where this ends up for NW-Europe, everybody should know.

Ok, still a long way to go, but atm things don't look primed. Not depressive, not sarcastic, just realistic.

You are ignoring the heights between North Canada and Northern Europe though.

That makes this 12z much different from the 0z.

And I think that N-Canadian low is too far Northwest to ignite cyclogenesis on the North Atlantic.

[MJB]

2 minutes ago, sebastiaan1973 said:

Perhaps this is the story of winter 2021. No real cold for large parts of NW-Europe despite many negative AO-days.

 

4 weeks after the 1970 SSW MBY was cut off from local villages by very heavy snow 

[topo]

I have mentioned this before but I am surprised on how consistently the ECM operational is much warmer than its ensembles after 168hrs..

It is like a repeated pattern, I am wondering if it just a matter of luck or something else..

[Vikos]

32 minutes ago, Daniel* said:

One major detail you’re missing out there’s a high pressure cell on latest 12Z moving north up east coast that would block the very cold air from spilling out.

For me those are "smaller details" in an overall pattern of moving the cold into the west. As we are in a forecast, locations of H and L will change a lot, also travelling routes of those. By now, the overall pattern is (I repeat myself) the transition of the cold block east to west. This pattern is also seen on the GFSop, GEM, JMA and even ICON

00z +12z 24th

  

25th

 

 

 

 

 

Edited January 26, 2021 by Vikos

[Singularity]

Ideally for Sunday we need to see ECM's trough shape combined with GFS(P)'s wedge shape with the cold air having made more inroads from the NE.

 

ECM & GFS 12z runs both seem a bit aggressive with the small low that grazes past on Saturday. Such a vigorous low increases the cyclonic mixing and flow off the Channel, making it harder to see any snow via cold air undercutting from the northeast.

UKMO looks better for that but can't compete with GFS(P) for the wedge shape.

Going to be difficult to get the right combination of cold air undercut and precipitation duration to achieve much, though.

So, I have more interest in the disrupting trough against cold air possibilities for Sunday.

It's really something to see ECM adjust toward what GEM has been showing for a few days now. I swear ECM used to be much better at picking up on trough disruption in the midrange? Goes to show - we could see strong ensemble signals prove misleading (looking at GEFS). There's a reason why I tend not to mention ensembles in the 7-10 day range, even when they show high agreement. They can be prone to playing 'follow the leader' when there's an error in the shorter term caused by model bias.

This, of course, applies even more in the longer range. So I'm reserved on the 11-16 day signals at this time.

[stodge]

Evening all

The arrival of the milder air brought in a grey overcast and evening rain after a final overnight frost. Fascinating output last evening with GEM leading the way for an early return to colder conditions but other models keeping it mild until T+240 but GFS certainly went cold with a vengeance at the end of FI so it'll be interesting to see if the signal for a pattern change in the second week of February remains tonight.

12Z GEM: - T+120 takes us to Sunday January 31st. A weak HP area over Scandinavia is retreating as an Atlantic trough advances from the west but the tough is struggling to come in against the block and a SSE'ly air flow ahead of the trough is part of it as is the trough's slight negative alignment suggesting more progress east than north. Milder air with positive uppers has returned to the south west but uppers of -4 and below cover most northern and eastern areas at this time. Moving on and changes to T+180 are small with heights persisting to the north east over Scandinavia and the LP moving slightly north in response but unable to advance far to the east. However, a W'ly flow across southern Britain suggests milder air has got in but with returning PM air into northern and western parts by T+180 behind the cold front. From there, the Scandinavian HP continues to expand to the north and the Atlantic trough disrupts back west apart from a cut-off LP which sits over the British Isles at T+240 with a cyclonic flow in place. Colder air is moving into northern Britain on the northern flank of the LP in an E'ly flow but the south remains in less cold air at this time. 

Not as good as last evening but a clear signal for Scandinavian heights from GEM this evening after a battleground evolution in the medium term.

12Z GFS OP - the T+120 differs slightly from GEM with a more S'ly flow and less defined heights to the north east but the trough is aligned negatively for the moment. Milder air with positive uppers across Ireland and the far south west but colder air with uppers of -4 or below over northern and eastern areas. From there. the trough extends across the British Isles but heights building to the north cause the trough to disrupt but by T+180 a small secondary LP is over southern Britain while a slack SE'ly flow covers northern areas. Milder air is confined to southern Britain while uppers below -4 are over northern Britain. Moving on and heights continue to build to the north and the trough further disrupts to thr south and east leaving initially a slack NE'ly flow but by T+240 it's calm over the British Isles with much colder air (-8 uppers) over most areas and a push of -12 uppers from the east.

OP ends cold if not very cold though the evolution from there isn't easy to define.

12Z Parallel - at T+120 again slightly different. A weak ridge of HP is over the British Isles by this time. Parallel has the trough further to the west than GEM or GFS OP but it is trying to extend a lobe of energy east towards the British Isles. Colder air persists over more of the British Isles with negative uppers persisting over all parts and uppers below -4 for eastern areas. As I suspected, it's not such a promising evolution for cold fans moving on from T+120 though we do see heights building to the north east while the Atlantic trough tries to move in but fails to make much progress east and instead a series of secondary LP move past the west of Ireland. A SSW'ly air flow covers most of the British Isles at this time and milder air with positive uppers covers England and Wales with only Scotland in slightly cooler air. From there, heights continue to build over Scandinavia and extend west to Greenland in the face of which the Atlantic trough disrupts west though keeping a residual energy lobe over the north west of Scotland. I also note a new LP over Iberia and North Africa. To be honest, I find this synoptic evolution a little odd but in terms of 850s, the south east remains mild with colder air slowly spreading south from Scotland.

To paraphrase Fleetwood Mac, Parallel "goes its own way" but all three models so far have gone their own way from T+180.

12Z ECM - at T+120 a clear signal for negative trough alignment as the main core LP runs east towards southern England. A SE'ly further north and east with weak heights. Milder air with positive uppers coming into the south west but colder air with 850s below -4 over northern and eastern Britain at this time. From there to T+192, the trough to the west and north west dominates with the core LP sitting to the south of Iceland and the trough extending SE to north west Britain.  A WSW'ly airflow of PM origin dominates by T+192 - positive uppers over eastern parts but a dip to slightly negative uppers behind a cold front to the north and west. From there, the trough extends east across northern Britain with heights to the north as a new Atlantic trough phases with the flow at T+240 and keeps a SW'ly air flow for southern areas. Uppers of -4 or below for many areas but milder air approaching again from the west. 

There's no point sugar coating it - ECM is a poor evolution for coldies tonight but it may be an outlier though it may not. To be fair, all four T+240 evolutions shown are very different suggesting there's a lot of uncertainty in the models tonight.

I'll put up, as I always do, the T+312 (Feb 8th) and T+384 (Feb 11th) charts from GFS OP and Parallel:

If I were a bluff old cynic, I'd say any trick to prevent the British Isles from getting a cold spell was being wheeled out tonight. The synoptics almost get there but then they don't. It may be best not to pay too much heed to the far FI charts given the huge uncertainty at T+240. Control doesn't do too badly with a solid 7-10 days of cold weather.

The 10 HPA charts continue to show a weak and disorganised PV and Parallel forces another split in the second week of next month.

Conclusion: a night when there are more questions than answers as the song has it. In the short term, the weekend's brief colder interlude is followed by a return of milder air early next week but from there plenty of options remain on the table. To be fair, all bar ECM show a strong rise of heights to the north and north east (Parallel adds Greenland heights as well). This causes the Atlantic to pull back and ideally we'd get a clean release of that energy but as you might suspect that doesn't always happen. ECM isn't interested in height rises to the north and keeps the trough and milder air in charge. Plenty to keep us interested and intrigued and to keep the nerves frayed as we go into February.

Edited January 26, 2021 by stodge

[Griff]

5 minutes ago, Singularity said:

Ideally for Sunday we need to see ECM's trough shape combined with GFS(P)'s wedge shape with the cold air having made more inroads from the NE.

 

ECM & GFS 12z runs both seem a bit aggressive with the small low that grazes past on Saturday. Such a vigorous low increases the cyclonic mixing and flow off the Channel, making it harder to see any snow via cold air undercutting from the northeast.

UKMO looks better for that but can't compete with GFS(P) for the wedge shape.

Going to be difficult to get the right combination of cold air undercut and precipitation duration to achieve much, though.

So, I have more interest in the disrupting trough against cold air possibilities for Sunday.

It's really something to see ECM adjust toward what GEM has been showing for a few days now. I swear ECM used to be much better at picking up on trough disruption in the midrange? Goes to show - we could see strong ensemble signals prove misleading (looking at GEFS). There's a reason why I tend not to mention ensembles in the 7-10 day range, even when they show high agreement. They can be prone to playing 'follow the leader' when there's an error in the shorter term caused by model bias.

This, of course, applies even more in the longer range. So I'm reserved on the 11-16 day signals at this time.

ECM following GEM is curious isn't it (cue verification stats and pin the tail on the week or day that proves our own confirmation bias - I know I'm fallible in that respect), but my thanks to @Tim Bland who first pointed this out to me (well first time I noticed).

Hard to discount or ignore once you spot it. Genuinely and respectfully perplexed that some people can't see a trend this evening towards the GEM and GFSP. That's not to say ECM brings Narnia, just a step in the right direction. Also, not to confuse my point of view, I accept things might go backwards tomorrow, but today seems positive. 

Ta 

[Man With Beard]

Very interesting progression on the ECM mean chart from T120 to T144

   

Suggests the milder side from Atlantic is far from certain to push through even southern areas, and a fair chance of a low splitting off into Europe.

The more progressive runs on the ensembles may see a very quick snow to rain event, but the runs that follow the mean could require a digger to dispense with all the snow. 

My suspicion is that latter will outnumber the former ... I'll check later

EDIT: Checked all 51 runs for snow by Monday morning - Yes, most runs have a strip of snow running in a line running in a SE to NW direction, somewhere through the UK (and particularly England/Wales) - but where exactly that line will be, you'll need to fight over for now. Could be anywhere. 

Edited January 26, 2021 by Man Without Beard

[chris55]

39 minutes ago, MJB said:

4 weeks after the 1970 SSW MBY was cut off from local villages by very heavy snow 

I thought that said 'local villagers" for a second there...... ill get my coat .

[Cold Winter Night]

10 minutes ago, Vikos said:

For me those are "smaller details" in an overall pattern of moving the cold into the west. As we are in a forecast, locations of H and L will change a lot, also travelling routes of those. By now, the overall pattern is (I repeat myself) the transition of the cold block east to west.

 

That could very well turn out to be a good thing for us to be honest. Especially combined with those Heights to our North popping up in several runs now.

As long as that mass of cold, low heights doesn't get comfy sitting over Greenland proper, but instead takes up residence West of Greenland, with developing heights to our North it will help to either prop up a Griceland or Scandi High, or undercut a Greenland/Griceland High.

For now, I don't see a well supported tendency to a +NAO to get worried about and having those low heights over to our Northeast has not brought us much cold, but instead it hindered opportunities for Scandi Highs developing.

[georgiedre]

4 minutes ago, Man Without Beard said:

Very interesting progression on the ECM mean chart from T120 to T144

   

Suggests the milder side from Atlantic is far from certain to push through even southern areas, and a fair chance of a low splitting off into Europe.

The more progressive runs on the ensembles may see a very quick snow to rain event, but the runs that follow the mean could require a digger to dispense with all the snow. 

My suspicion is that latter will outnumber the former ... I'll check later

 

Don't say things like that abc hahahha

Edited January 26, 2021 by georgiedre
Changed abc to abc for some reason

[MJB]

6 minutes ago, chris55 said:

I thought that said 'local villagers" for a second there...... ill get my coat .

Christ that would have been some fall of snow if  we'd have been  cut off from our  next door neighbours 

[Daniel*]

26 minutes ago, Vikos said:

For me those are "smaller details" in an overall pattern of moving the cold into the west. As we are in a forecast, locations of H and L will change a lot, also travelling routes of those. By now, the overall pattern is (I repeat myself) the transition of the cold block east to west. This pattern is also seen on the GFSop, GEM, JMA and even ICON

00z +12z 24th

  

25th

 

 

 

 

I wouldn't put too much trust into GEM to be honest

 

 

No they aren’t smaller details as Nick S mentions domino effects from smaller changes. There’s nothing wrong with Canada going very cold it’s very normal for them when part of polar vortex visits them, we don’t see same as there’s big modification from sea. There’s satisfactory cold to NE as long as E Conus doesn’t go into freezer it’s not a concern. You’re worrying over nothing. 

[Chesil View]

So here's a thought. Looking at the Meto update. The 31st Jan-9th Feb  section says ' towards the end of this period high pressure is expected to build across northern UK.  I have notionally taken a date of 7th Feb for that.  ECM and Gem only go out to 5th but are both building high pressure over or close to Northern UK by that date. GFS does so from the 4th. So it could be argued that all three models are possibly indicative of or building towards where today's wintry Meto update wants to take us.

As I say just a thought.

[Matt H]

The CMA 12z is clearly following the UKMO long-range update today.

“Towards the end of this period, we may see high pressure build over the north of the UK, bringing colder temperatures and wintry outbreaks.”

 

[Bricriu]

1 minute ago, Broadmayne blizzard said:

So here's a thought. Looking at the Meto update. The 31st Jan-9th Feb  section says ' towards the end of this period high pressure is expected to build across northern UK.  I have notionally taken a date of 7th Feb for that.  ECM and Gem only go out to 5th but are both building high pressure over or close to Northern UK by that date. GFS does so from the 4th. So it could be argued that all three models are possibly indicative of or building towards where today's wintry Meto update wants to take us.

As I say just a thought.

Yes I think so. The ECM, although it does not end as some posters want, is broadly in line with what the UKMO suggests. If it ran to day 12 or 13 it could be quite interesting. You've got to hand it to the UKMO if this is indeed where we end up.