Model Output Discussion - Snow for some, but what else is in store?

[Don]

18 minutes ago, Mike Poole said:

Agreed NWS, UKMO must have this right at T144 or we are all condemned to a weather purgatory of nothingness for the rest of winter.

Really, for the rest of winter?  It all seemed to start on a more positive note this evening!

Edited January 16, 2021 by Don

[badgerhud]

Hi all

I'm more of a reader of these forums than a poster and have only a basic knowledge in chart reading.

I've never seen so many ups and downs run to run as I have in the last month, currently on a down for us cold lovers.

One thing I will add is there is plenty to be optimistic about, to me there isn't as much atlantic influence influence this year so within 5 days we could be looking at cold again or of nowhere, no point looking past that at all. We had a decent snow event in Huddersfield on Thursday and even 48 hours before that it looked like we were getting nothing at all!

Chins up and enjoy the next month or so, literally anything can happen!

 

 

 

 

 

 

[Hotspur62]

Have really enjoyed the last 24 hours on this forum and a good discussion from Vikos and Feb1991 blizzard last night both whom put their reasoning forward in terms of POSSIBLE implications of SSW going forward.To me we will find out in 7 days time or so but it doesn’t matter who was right or wrong as both backed up charts etc with logical reasoning and that was just a good discussion last night that showed respect in each other’s views.

Quickly moving on to today’s latest models in the short term I feel in terms of cold we need the UKMO to be right at 120hours and ideally I would like the low another 50 miles east and the Arctic High stronger to push it further South and East.Sadly I feel there is only about a 25%chance of this happening but we will have maybe a clearer picture by tomorrow evening.The worrying trend for me is the consistent 10 day mean showing on the gfs ecm and gem and I think it was that wise man John Holmes who hinted on his review earlier that 8-14 day charts look to be heading in that direction too but maybe give it another 2-3 days on that one.The one good thing is that 10 days is still miles away in this current volatile world of modelling so do not give up hope yet for colder uppers to still be in existence as we head towards the end of January,although this is probably the less likely outcome for Uk wide snow(Scotland Northern Ireland and Northern England still look primed for show events as we head through January.

[Don]

48 minutes ago, chionomaniac said:

I wonder how many times that west based -NAOs have followed SSWs?  And then moved further west allowing for the initial Atlantic undercut leaving the UK in the firing line, with the NAO slowly turning positive and a return of more zonal conditions.  It has happened before in 2009. I wonder has it been a recurring theme over the years.

Are you now seeing this as a likely scenario Chiono or just one option?  That would be a bitter pill to swallow as at least the first part of February 2009 delivered copious amounts of snow before turning very mild!  However, what will be will be.....

[Matt H]

18 minutes ago, feb1991blizzard said:

Has anyone seen this run from the CFS for March, run the whole month through, this would absolutely cripple this country with snow and cold, even allowing for surface heating being stronger in March, you could be looking at the coldest March of all time, it is quite spectacular, it would be one of the best months in my life overall, never mind Marches.

https://www.meteociel.fr/modeles/cfse_cartes.php?ech=1074&code=0&carte=1&mode=0&run=0

 

This is why I love the CFS extended runs. Always shows some wild and interesting synoptics to admire even though they have no chance of verifying. One day!

[PiscesStar]

43 minutes ago, BLAST FROM THE PAST said:

I think it’s looking better than yesterday.  Next proper review for me is on Tuesday.  T120 could be an interesting marker today

 

BFTP

19th has been een for me the turnaround point as well mate 

[stodge]

Evening all

Well, some saw so/me snow this morning (if they were up early enough, lived high enough or were far enough east). Nothing of course in lowland East London but it was nice to see some sunshine to end the day. Last night's models had a central theme and that was rain - plenty of it especially for southern and western areas. Worryingly high totals given saturated land so I'll be having a look at the precipitation numbers tonight on the GFS OP.

All the models went mild by T+240 last night so let's see what tonight's manifestations have to tempt and tantalise:

12Z GEM: it's been singing from the mild hymn sheet for the past few days and has in my view led the way on the evolution. T+120 takes us to Thursday and by then the LP has moved east to Southern Scandinavia but the residual heights are preventing the trough dropping too far to the south. Instead, it has phased west into the Atlantic to create an extended complex trough linking right back to the eastern seaboard.  West or North-west winds cover the British Isles by this time. Uppers of -4 to -8 away from the south of England where zero to -4 air holds sway. Moving on, the trough remains dominant with secondary LP moving east across southern Britain with the main LP centred just off the Norwegian coast keeping the secondary features to the south and linking back to a large mid-Atlantic LP. Heights remain over Greenland but with the warmer air starting to move west while heights also persist over Iberia and North Africa.  Uppers of -4 to -8 remain by T+180 but with milder air approaching from the south west. From there, little changes - the jet moves back north briefly but by T+240 the next LP is crossing central Britain with strong W'ly winds across southern parts. It's mild everywhere by this time with uppers of +4 across the south.

As I've been saying for days, our problem is or are the heights to the south which are fed by the mid-Atlantic trough which has nowhere to go in the absence of a strong zonal jet to kick it east. The main theme is rain and I've added the cumulative rainfall chart to show 4 inches or more or rain for southern and western areas in the next 10 days.

12Z GFS OP - differences with GEM at T+120 with a more vigorous LP closer to the British Isles - indeed, that's quite a storm for the North Sea and real storm winds for Denmark's west coast.  Small secondary LPs sit in the trough upstream. 850s of -4 to -8 coming down across the British Isles but zero to -4 further south. From there, the storm moves north then fills and moves back west to be just to the north of Scotland by T+180. The trough extends south through the British Isles with secondary LP within its circulation so it's a cyclonic flow over the British Isles with positive uppers close to the south coast but colder air persisting further north. From there, the LP to the north of Scotland gets drawn south and west and merged into the general circulation as heights move into Iberia and push the jet back north but at T+240 one of the LP centres has started moving east to be over northern Scotland with the main LP still in mid-Atlantic. Positive uppers cover not just the British Isles by T+240 but most of north western Europe with a wash of TM SW'ly air. Again, I've added the cumulative precipitation chart for T+240 with approaching five inches of rain for parts of south wales in the next 10 days.

Wet, wet, wet - sounds like an 1980s pop group, doesn't it?

12Z Parallel - not hugely different to the OP at the same time though the storm perhaps a smidgen less intense. From T+120 Parallel diverges a bit from OP and GEM. The initial LP moves east into Scandinavia and a new LP centre forms to the north of Scotland and by T+180 is over the Faeroes. Meanwhile, a separate Atlantic LP from the eastern seaboard phases into the circulation and rushes eastward deepening to be across southern England by T+180. Cyclonic flows over the British Isles by this time with positive uppers over southern and eastern England but -4 to -8 air still to the north. The LP crosses southern England and continues east into northern and north eastern Europe and is over Belarus and Lithuania by T+240. A ridge is moving in not from the south but from the north and this has cut the flow to the trough leaving the main trough spinning in mid ocean. Cold air continues over the British Isles with -4 to -8 air generally and colder air moving into Scotland. I've added Parallel's precipitation chart showing a slightly different rain profile - note the high rainfall totals for eastern coastal counties.

Parallel goes cold at T+240 - the first sign of a new trend. We'll see - to be fair, Parallel was quite early in calling an end to the cold spell so it's not to be ignored for all it's early days.

12Z ECM - I'm expecting bugger all from the Mild Model so I'm not going to be disappointed when it shows a raging blowtorch at T+240. The T+120 looks very close to GFS OP but with perhaps a less active upstream profile. Uppers of zero to -4 generally by T+120. From there, the trough aligns positively to the west and with height rises to the south, a SW'ly covers the British Isles by T+192. However, the cold air hangs on at this time with uppers still -4 to -8 generally but positive uppers are approaching. From there, areas of LP cross the centre of the British Isles as heights continue to rise from the south with the residual Atlantic LP far to the west. Positive uppers have extended through Ireland, Wales and England but colder air hangs on in Scotland.

I make that 3-1 to mild overall but not as convincing as last evening by any stretch so overall an upgrade for cold fans.

Let's have a look at the extended FI from GFS OP and Parallel respectively:

OP brings the PV back over to our side of the globe but Parallel doesn't really and I note the return of the Russian HP on Parallel albeit it's no influence on the weather over the British isles at this stage. Control ends very unsettled with a strong PV back over Greenland/NE Canada.

Conclusion: a step forward for cold fans tonight but no more. It still seems unlikely we'll end up on the cold side of the trough given the strength of heights to the south but Parallel shows this as an option so we have to consider it. The main theme remains rain and some serious amounts in the next 7-10 days. Little or no sign of anything settled in the next 14 days to be honest with the Atlantic trough dominant through all charts and all models despite (or perhaps because) of the absence of strong zonal winds.

 

 

 

[Tim Bland]

3 minutes ago, Frosty Winter said:

This is why I love the CFS extended runs. Always shows some wild and interesting synoptics to admire even though they have no chance of verifying. One day!

Ahh good old spring...how’s next December looking? Any signs of a SSW

[Mike Poole]

Just to unpack the ECM ensembles a bit, here’s the mean and spread at T240:

Re the mean, there’s the easterly - it just goes north of the UK (yellow)!  And there’s not much uncertainty about that on the spread (yellow region).  The red region which we are in, there’s nothing much driving that at all, so might behave much like summer!  Black region is the main trop vortex, and blue region is the major region of uncertainty and we don’t give a flying toss about it.

 

So either this entire ensemble suite is wrong, or the cold spell is up in smoke.  I think the entire suite is wrong and the UKMO is right, but we will find out in the next day probably. 

[chionomaniac]

2 minutes ago, Don said:

Are you now seeing this as a likely scenario Chiono or just one option?  That would be a bitter pill to swallow as at least the first part of February 2009 delivered copious amounts of snow before turning very mild!  However, what will be will be.....

We’ve seen it happen before, and with the current models we can’t rule it out, despite the uncertainty.  I would say 60% in favour of the west based -NAO scenario or weak block allowing the Atlantic to progress underneath in the median term. The 40% would be the UKMO option of increasing the blocking - but this is far less likely. The risks of the SSW is that the previous non Nina pattern was dislodged by the variability of the trop blocking following downwell. If this kicked the trop pattern to be more in line with La Niña then that would be a real p*****. But time will tell and After an SSW I never rule anything out.

[Hotspur62]

27 minutes ago, feb1991blizzard said:

Has anyone seen this run from the CFS for March, run the whole month through, this would absolutely cripple this country with snow and cold, even allowing for surface heating being stronger in March, you could be looking at the coldest March of all time, it is quite spectacular, it would be one of the best months in my life overall, never mind Marches.

https://www.meteociel.fr/modeles/cfse_cartes.php?ech=1074&code=0&carte=1&mode=0&run=0

 

Yes ,tbh it starts getting colder from early February with some dry frosty weather and then from about 12th February it goes on an insane run with snow events galore,sliders galore,you name that run has it!!That would put March 2013 in the shade which was the coldest in the UK for about 50 years!!We can but dream ..

[Matt H]

7 minutes ago, Tim Bland said:

Ahh good old spring...how’s next December looking? Any signs of a SSW

There’s a lovely Halloween plume at t6996. Can’t believe I’ve just gone through the whole 9 month run, the lockdown boredom is shining through.

Edited January 16, 2021 by Frosty Winter

[Jason M]

56 minutes ago, General Cluster said:

This thread's starting to do my 'ead in!

I know that Snowmageddon, at least in the immediate future, has locked itself firmly in the wardrobe -- but, really: oh yes it is, oh no it isn't (which would of course be a whole lot easier, were I able to discern the latest 'upgrade' from its doppelganger, the latest downgrade)

Aaaaaaaaaaaaaaaaaaaaaaaaaargh!

But, on the other side of the coin, what would this thread be like, were it only 'deemed' suitable for dry, reasoned scientific debate? Zzzzzzzzzzzzzzzz?

Empty? 

[Don]

6 minutes ago, Mike Poole said:

So either this entire ensemble suite is wrong, or the cold spell is up in smoke.  I think the entire suite is wrong and the UKMO is right, but we will find out in the next day probably. 

I do hope you're correct, make or break for winter coming up soon.

[Don]

7 minutes ago, chionomaniac said:

The risks of the SSW is that the previous non Nina pattern was dislodged by the variability of the trop blocking following downwell. If this kicked the trop pattern to be more in line with La Niña then that would be a real p*****. But time will tell and After an SSW I never rule anything out.

I think this is something you've been concerned about since the SSW came into the equation, if I'm not mistaken?

[chionomaniac]

Just now, Don said:

I think this is something you've been concerned about since the SSW came into the equation, if I'm not mistaken?

Lol, yes one minute and no the next.  It’s a difficult game to predict. 

[Mike Poole]

1 minute ago, Don said:

I do hope you're correct, make or break for winter coming up soon.

Yes, I think it is a bit make or break here, the issue is not that reversal to easterly winds due to the SSW doesn’t happen, it is that it happens but at a far higher latitude than us and we are left to the south in a kind of no mans land with no cold air to tap into anywhere, winter would be over effectively because the  pattern would last for weeks as it is the result of the strong SSW.  

[Uncertainty]

5 minutes ago, Roger J Smith said:

GFS mean wasn't as strong as the ECM at 120h but five or six of the thirty perturbations show something similar. The main difference seems to be that the GFS has one additional wave in the chain of them, and that robs the ECM feature of some potential energy, and reserves it for a slightly later time when on average it doesn't deepen as rapidly. But as I say, some of the variants are just as strong, one or two look further south as well, reaching peak intensity closer to the Midlands than northeast England. 

At the risk of being Capt Obvious, the further north or west you are, the more likely you're going to see snow from this, at least up to a point, maybe some places would be too far northwest, let's say a zone from Aberdeen to Glasgow to Belfast to Yorkshire arcing around the ECM low at this point has a fairly high risk of disruptive snowfalls, the arc further out than that has somewhat less risk. 

Yes Roger I had a look through the EPS members for Thursday night, a significant number have some huge snowfall totals by Thursday in and around the arc you mentioned.
 

This is a fairly representative example. Some are weaker but there are quite a few even more extreme examples than the above.

A small but noticeable cluster have a more diffuse area extending much further south, around central England. 

I am not foolhardy enough, and nor are most of you, to take these depths seriously. But the sheer number of members - id say nearly 50%, including the Op that are showing this event ( the scenario Roger has described) would translate, if  it were to persist into Monday morning say, into the introduction of a dual rain / snow warning to account for the risk of a disruptive rain / snow and perhaps even wind event midweek. 

Into the far reaches of the EPS, Northern blocking remains the major player, but most members feature a low somewhere near S U.K. and therefore the opportunities for further high impact rain, snow and wind will persist.

Very little appetite for last February’s hideous Euro high / Atlantic storms scenario in the EPS. 
 

And finally you simply can’t categorically say this SSW is in the 30% which don’t bring us cold as it hasn’t even finished reversing yet. If @sebastiaan1973is right with his slow -NAM drip theory (due to Euro blocking at 5 days before SSW onset, which I personally feel it was as we had a Scandi / U.K. high around that time...) then we need to wait until mid Feb at least before calling time on this event. Indeed it is already having a fundamental effect on NH patterns presently, the flow from Siberia to Florida attests to that. Alas, as some would say, it has handed us southwesterlies, but the persistence of its influence over NH dynamics is still very much open to debate and, if the EC46 is to be believed, then that persistence will last well into February. 
 

[Jason M]

11 minutes ago, Mike Poole said:

Just to unpack the ECM ensembles a bit, here’s the mean and spread at T240:

Re the mean, there’s the easterly - it just goes north of the UK (yellow)!  And there’s not much uncertainty about that on the spread (yellow region).  The red region which we are in, there’s nothing much driving that at all, so might behave much like summer!  Black region is the main trop vortex, and blue region is the major region of uncertainty and we don’t give a flying toss about it.

 

So either this entire ensemble suite is wrong, or the cold spell is up in smoke.  I think the entire suite is wrong and the UKMO is right, but we will find out in the next day probably. 

They could easily both be right. Its perfectly possible the the METO 144 takes us to broadly the same place as the other models by day 10. From watching the GEFS over the last few days I've seen quite a few give a more favorable outcome short term only to end up with our friend the Iberian high at day 10 anyway. I just see the METO chart as within the envelope of the bigger pattern. In essence its still taking us to the same place but in a slightly better car!! Obviously i hope you will be proved right but for me the Iberian ridge now looks the strong favorite which means we look to Feb (cue blizzards on the pub run ).

 

[MJB]

1 hour ago, Djdazzle said:

Maybe, but who wants it in April? I’ll be looking for warmth then!

Why April ? Where are your facts to support that ? 

[Don]

3 minutes ago, Mike Poole said:

Yes, I think it is a bit make or break here, the issue is not that reversal to easterly winds due to the SSW doesn’t happen, it is that it happens but at a far higher latitude than us and we are left to the south in a kind of no mans land with no cold air to tap into anywhere, winter would be over effectively because the  pattern would last for weeks as it is the result of the strong SSW.  

Lol, it's times like this I (almost) wish we had the PV of doom like last year as there was hardly any point in looking or hoping for anything more than a brief cold snap anyway!  This knife edge stuff is not good for the nerves lol!  Still just another winter at the end of the day and far more important things to be concerned about in the world currently!

[sebastiaan1973]

5 minutes ago, Uncertainy said:

And finally you simply can’t categorically say this SSW is in the 30% which don’t bring us cold as it hasn’t even finished reversing yet. If @sebastiaan1973is right with his slow -NAM drip theory (due to Euro blocking at 5 days before SSW onset, which I personally feel it was as we had a Scandi / U.K. high around that time...) then we need to wait until mid Feb at least before calling time on this event. Indeed it is already having a fundamental effect on NH patterns presently, the flow from Siberia to Florida attests to that. Alas, as some would say, it has handed us southwesterlies, but the persistence of its influence over NH dynamics is still very much open to debate and, if the EC46 is to be believed, then that persistence will last well into February. 

 

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

---

<p><strong class="journal-contentHeaderColor">Abstract.</strong> Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in...

It's a theory of Domeisen et al

[feb1991blizzard]

7 minutes ago, chionomaniac said:

Lol, yes one minute and no the next.  It’s a difficult game to predict. 

I wanted the SSW (against your better judgement), reason for that is we just were not getting anywhere with uppers, cold rain from usually banker airmass sources, but only wanted a split, once that stratospheric wave was in the Atlantic and it wasn't a proper split, i thought there would be residual shortwave energy to the NW, i was wrong, there now looks to be a worse case scenario of low after low just barrelling through us, i have noticed this before with non perfect but interesting strat events, the models still promise greatness for a while but they all then back off in the space of a few runs, i wonder why this happens, even the EPS a while back had a large cluster with max's of freezing  or 1c for London.

[Kentspur]

1 hour ago, feb1991blizzard said:

Has anyone seen this run from the CFS for March, run the whole month through, this would absolutely cripple this country with snow and cold, even allowing for surface heating being stronger in March, you could be looking at the coldest March of all time, it is quite spectacular, it would be one of the best months in my life overall, never mind Marches.

https://www.meteociel.fr/modeles/cfse_cartes.php?ech=1074&code=0&carte=1&mode=0&run=0

 

Interesting I've been checking daily the CFS runs and they seem consistently very cold. March 2013 anyone?

Edited January 16, 2021 by Kentspur

[Don]

5 minutes ago, Kentspur said:

Interesting I've been checking daily the CFS runs and they seem consistently very cold. March 2023 anyone?

I think you mean 2013?  I would take a cold March if the rest of winter does not deliver TBH.  Beggars can't be choosers at the end of the day!

Edited January 16, 2021 by Don