Model Output Discussion 1st January 2014-06z onwards.

[LomondSnowstorm]

I haven't really seen much evidence of a sustained eastward shift of the block to be honest, in fact the low getting held out to the west  is perhaps a bigger problem for us than the block being too far east (at least at the moment).We need to remember where we were two days ago in the modelling and that we have made some massive strides forwards - comparing Monday night from the ECM 0Z two days ago compared to now shows a massive shift westwards with much more jet energy going under the block:

 

 

With the blocking in place to the northeast and at least some jet energy getting under the block (helped by an emerging Euro trough) most of the differences are based around how far south and west the pattern can get rather than if there'll be an easterly flow at all for our longitude. Living further northeast than most members on here I'm not as despondent as some on here by the northwards shift of the pattern but equally we do want to see a shift towards more trough disruption to allow the cold pool to back westwards. These are fine margins, and as long as we have the basic 'trough to the south, high to the northeast' then the boundary between snow and rain will be fluid even into the mesoscale model range. Currently northeast Scotland away from the immediate coast is the place to be but at this range the Margin of error is big enough that I wouldn't rule out snow for any part of the UK within the next 8 days.

I'm also not all that concerned with the idea of a 'return to zonality' post Day 10 - it's worth noting but at that range a lot can, and very often does, change at that kind of range. We still have over half of winter left, with the second half always progged as being of more interest for HLB than the first, so even if this one doesn't work out there's still plenty of time left to get your share of snow. Last year it took until March, two winters ago it took us in Eastern Scotland until early April, so it's far too early to get hung up on the first real chance of an easterly this winter so far.

The only thing I will add that's a bit concerning is the potential for further heavy rain in the south - that's not what anyone needs, so for that reason I hope we can shift the troughing further south.

Edited January 9, 2014 by LomondSnowstorm

[snowice]

Fantastic post backed up by real evidence and as you say ECM mean wrong at 120hrs.(I don’t think so)

 

I think if more members read this post they will stop panicking.

 

How often do we see the gfs flip flop with little support.

Fascinating tussle between the ensembles this morning. ECM mean at T144:

Very good definition in the highs and lows suggests the ensembles are in fairly good agreement; 995mb low to west of Ireland and 1025mb high over Scandi. The meeting of the troughs (i.e. the dark blues) east and west is slap bang through the UK. That roughly indicates the border between Arctic conditions and less cold conditions - so basically it would be somewhere across the UK, absolutely no sense in trying to say where at the moment, but the chart says "Snow - somewhere in the UK". Mean charts at T168 and T192 suggest a slow sink south so areas without snow initially may get it later on if the Atlantic fronts don't fizzle out too soon.

 

GFS mean at T144

Quite different in that the lows between W Ireland and N Italy do not link up as well, and no link up of the troughs west to east. Probably not as much clustering as on the ECM as the colours in the Scandi High don't go green and the isobars are a bit more flabby. In fact, a look at the individual ensemble members is a bit like mayhem, no agreement between them at all!! http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=144

 

You would be tempted, after looking at the GFS, to think that there is no possible way to make a forecast as far out as T144. And certainly, whilst the GFS ensemble members continue to look chaotic, there is going to be doubt in the forecast, perhaps even a small doubt that cold air is going to reach any part of the UK. But you can see that the ECM ensembles are far more in agreement with each other than the GFS's, since by T192 the difference in definition of highs and lows between the two ensemble means is even more marked:

That suggests the ECM has far more confidence in its own evolution than the GFS has. The ECM is fairly confidently of some sort of block to our north still in place by T192 and even more confident that a decent low pressure system will be centred over Biscay (note - this is a fairly good set-up for cold and snow over the UK, as long as there isn't too much of a southerly flow). However, the GFS suggests there might be some blocking to our north-east and some sort of low pressure over France but goodness knows exactly where.

 

So although the GFS 06Z has raised the blood-pressure and caused some on here to cry "Game Over", my current thinking is that the easterly is probably still on, though depth of cold is still well up for debate. Looking at the ensemble mean for T850s, I'm guessing there will be members in the showing anything from 0C in the South West to -10C on the east coast - so too early to be certain of that one.

 

But these situations (Atlantic vs Easterly battle), considering it is January, usually involve a precipitation bearing front dividing the cold and the less cold, with the cold side having snow, the milder side having rain, but if it stays in situ for a while more and more of the front gets undercut by the cold and eventually more and more places have snow. Leaving out the extreme runs of the GFS, the front surely will be somewhere over the UK, perhaps North England/Southern Scotland being favoured on the latest charts. But that's a really crude prediction - best for now to say, at T144, the snowline somewhere between the Shetlands and the M4, edging south and west with time.

 

So uncertainly, yes, but not as much uncertainty as some are making out today. Final note - if the block to the north doesn't happen, the ECM mean is going to look pretty ridiculous even at T120 - it's happened but very, very, very rare that the ECM mean is that wrong at that short a range. I think it won't be far off.  

 

Edited January 9, 2014 by snowice

[fergieweather]

 

and there i was thinking that the signal beyond the colder period remained uncertain. seems that mogreps-15 must be keener on the jet blasting back through than ecm ens.

It's not so straightforward (nor has it been even since yesterday). MOGREPS-15's 00z suite was indeed less bullish about a colder solution and equally offered a more mobile signal throughout next week's 'event'. However, for now at least, UKMO have erred somewhat more towards the EC-NCEP ensemble consensus, i.e., with the easterly regime across the country by later next week with net result of coldest/snowiest to NE; more to normal temps W/SW. In the latter, PPN as rain (.e.g into Weds) but with potential for this to offer snow as it eases NE into colder boundary conditions. Now, inevitably this broad-brush is as far as can be offered, not least given the clear uncertainties on the areal boundary of coldest easterly feed (broad spread on this already very evident and discussed here on the forum). Equally of course, the 12z NWP suites might yet lean more towards the MOGREPS solution and lose the pronounced cold in any meaningful sense... or we could see a reversion back to where we were this time yesterday. In all honesty, there's no smoke and mirrors about this at UKMO - it's just not clear-cut but on balance, as the Dep Chief stresses, might manifest as a fairly typical January cold snap of possibly limited longevity (that's their current view), but nonetheless offering a chance of snow at least to northern areas, possibly to low-levels; and perhaps transiently elsewhere too. Let's await the 12z output. Edited January 9, 2014 by fergieweather

[tight isobar]

It's not so straightforward (nor has it been even since yesterday). MOGREPS-15's 00z suite was indeed less bullish about a colder solution and equally offered a more mobile signal throughout next week's 'event'. However, for now at least, UKMO have erred somewhat more towards the EC-NCEP ensemble consensus, i.e., with the easterly regime across the country by later next week with net result of coldest/snowiest to NE; more to normal temps W/SW. In the latter, PPN as rain (.e.g into Weds) but with potential for this to offer snow as it eases NE into colder boundary conditions. Now, inevitably this broad-brush is as far as can be offered, not least given the clear uncertainties on the areal boundary of coldest easterly feed (broad spread on this already very evident and discussed here on the forum). Equally of course, the 12z NWP suites might yet lean more towards the MOGREPS solution and lose the pronounced cold in any meaningful sense... or we could see a reversion back to where we were this time yesterday. In all honesty, there's no smoke and mirrors about this at UKMO - it's just not clear-cut but on balance, as the Dep Chief stresses, might manifest as a fairly trypical January cold snap of possibly limited longevity (that's their current view), but nonethless offering a chan ce of snow at least to northern areas, possibly to low-levels; and perhaps transiently elsewhere too. Let's await the 12z output.

nicely summed up.and just reinforces the uncertainty. ONCE AGAIN lets see what 12z throw up.or will most be throwing up after them, .:-/

[johnholmes]

my take for what it is worth using the inevitable pdf format and copied into the other thread as it may well be hard for me to find in here when I want it.

 

another update on thur 8 jan.pdf

 

it is a biggish file-please read it all it might help new folk and I am happy to try and answer any questions about it

 

[nick sussex]

Afternoon all

 

Just caught up with the  model outputs. It wouldn't be the same without some drama when theres a sniff of cold for the UK.

 

Overall today there still is a cold signal regardless of changes to the troughing near the UK, I still expect the easterly to get here IMO its more a timing issue.

 

A quick look at the ECM De Bilt ensembles for this mornings run:

 

 

That still looks healthy to me in terms of cold into Holland.

 

Now the wind directions are very good IMO:

 

 

You can see there the almost total support for the winds moving round to a more easterly/ne direction from around the 14th January.

 

This clearly shows that there will be some trough disruption and influence from the high to the ne, so of course the key thing for  the UK is if this occurs to the west or over but still the ensembles are rock solid that there is no sign of the troughing getting too far into mainland Europe.

 

Upstream there are timing issues with how quickly phasing occurs between a series of shortwaves running in from the Pacific across the USA, which will impact on the troughing near the UK.

 

However even though the pattern there is quickish it is expected to re-amplify next week, with a west coast ridge and troughing in the eastern CONUS, now this brings me to the models now toying with an extension to the cold, so in a sense they might be seeing another change and attempting to factor that in to the previous more flatter trend.

 

The upstream pattern and blocking to the ne do support a cold outcome for the UK, the issue is how long low pressure will take to disrupt and slide se allowing the ridge to back west, we have to factor in the last few weeks upstream, flatter became more amplified, because of the expected re -amplification upstream the Azores high is likely to edge west, low heights set to establish over the Med.

 

Because of the upstream pattern we should see a sharpening of troughing near the UK, with more elongation to any troughing.

 

In terms of tonights outputs given the signal for upstream and the pattern over the east Pacific I'd expect low pressure at first to the west of the UK will slide se'wards, rain increasingly turning to snow on its east/ne flank before this pulls away, the ridge to the east backing west and an easterly.

 

After that much depends on how long that amplification holds over the eastern USA, that's the next likely model drama!

 

 

 

[Downpour]

GEM has bitterly cold easterly, GFS easterly being pushed further back, ECM brings eventual easterly, who will be right?

GEM is rarely right when the others say no. It's not a cannon fodder model by any means but is rarely a trendsetter. I did see JMA set a trend correctly one winter but I think that was a one-off!

[Downpour]

I haven't really seen much evidence of a sustained eastward shift of the block to be honest, in fact the low getting held out to the west  is perhaps a bigger problem for us than the block being too far east (at least at the moment).We need to remember where we were two days ago in the modelling and that we have made some massive strides forwards - comparing Monday night from the ECM 0Z two days ago compared to now shows a massive shift westwards with much more jet energy going under the block:

 

 

With the blocking in place to the northeast and at least some jet energy getting under the block (helped by an emerging Euro trough) most of the differences are based around how far south and west the pattern can get rather than if there'll be an easterly flow at all for our longitude. Living further northeast than most members on here I'm not as despondent as some on here by the northwards shift of the pattern but equally we do want to see a shift towards more trough disruption to allow the cold pool to back westwards. These are fine margins, and as long as we have the basic 'trough to the south, high to the northeast' then the boundary between snow and rain will be fluid even into the mesoscale model range. Currently northeast Scotland away from the immediate coast is the place to be but at this range the Margin of error is big enough that I wouldn't rule out snow for any part of the UK within the next 8 days.

I'm also not all that concerned with the idea of a 'return to zonality' post Day 10 - it's worth noting but at that range a lot can, and very often does, change at that kind of range. We still have over half of winter left, with the second half always progged as being of more interest for HLB than the first, so even if this one doesn't work out there's still plenty of time left to get your share of snow. Last year it took until March, two winters ago it took us in Eastern Scotland until early April, so it's far too early to get hung up on the first real chance of an easterly this winter so far.

The only thing I will add that's a bit concerning is the potential for further heavy rain in the south - that's not what anyone needs, so for that reason I hope we can shift the troughing further south.

Sorry but that's rubbish. We didn't have to wait until March at all. We had snow on lying snow in LONDON in mid-Jan last year. Two inches in west London on the Friday followed by a royal all-day dumping on the lying snow on the Sunday. 

 

March will be remembered in the capital for one week where it snowed moderately pretty much every day, with not a flake settling! 

[Roadrunner]

Amateur question re the models. Does anyone follow the model output in the area for, say, areas around the great lakes? I am just curious as to whether they have all the model drama we have in this country or whether their model watching is much less up and down.

While I realise that we are an island and a million other factors make us and for example Toronto different, would a model watcher in the US be able to say with certainty at the range we are looking at that moment that 'x' will be happening a week in advance I. E. The recent big freeze over there? Did GFS Nail that 10 days before with very little wobbles?

[Downpour]

Afternoon all

 

Just caught up with the  model outputs. It wouldn't be the same without some drama when theres a sniff of cold for the UK.

 

Overall today there still is a cold signal regardless of changes to the troughing near the UK, I still expect the easterly to get here IMO its more a timing issue.

 

A quick look at the ECM De Bilt ensembles for this mornings run:

 

090100.png

 

That still looks healthy to me in terms of cold into Holland.

 

Now the wind directions are very good IMO:

 

W1.png

 

You can see there the almost total support for the winds moving round to a more easterly/ne direction from around the 14th January.

 

This clearly shows that there will be some trough disruption and influence from the high to the ne, so of course the key thing for  the UK is if this occurs to the west or over but still the ensembles are rock solid that there is no sign of the troughing getting too far into mainland Europe.

 

Upstream there are timing issues with how quickly phasing occurs between a series of shortwaves running in from the Pacific across the USA, which will impact on the troughing near the UK.

 

However even though the pattern there is quickish it is expected to re-amplify next week, with a west coast ridge and troughing in the eastern CONUS, now this brings me to the models now toying with an extension to the cold, so in a sense they might be seeing another change and attempting to factor that in to the previous more flatter trend.

 

The upstream pattern and blocking to the ne do support a cold outcome for the UK, the issue is how long low pressure will take to disrupt and slide se allowing the ridge to back west, we have to factor in the last few weeks upstream, flatter became more amplified, because of the expected re -amplification upstream the Azores high is likely to edge west, low heights set to establish over the Med.

 

Because of the upstream pattern we should see a sharpening of troughing near the UK, with more elongation to any troughing.

 

In terms of tonights outputs given the signal for upstream and the pattern over the east Pacific I'd expect low pressure at first to the west of the UK will slide se'wards, rain increasingly turning to snow on its east/ne flank before this pulls away, the ridge to the east backing west and an easterly.

 

After that much depends on how long that amplification holds over the eastern USA, that's the next likely model drama!

Hi Nick. I think it's more the bearishness from the Office that has put a downer on the thread, rather than the models themselves which, as many have said, are arguing the toss over marginal geographic changes at T100+ range that will in any event vary numerous times before we get there. Many members – and I include myself – are wondering why the Office are saying "no" to a cold blast despite NWP to the contrary. 

[LomondSnowstorm]

Sorry but that's rubbish. We didn't have to wait until March at all. We had snow on lying snow in LONDON in mid-Jan last year. Two inches in west London on the Friday followed by a royal all-day dumping on the lying snow on the Sunday. 

 

March will be remembered in the capital for one week where it snowed moderately pretty much every day, with not a flake settling! 

Good for you, all I meant was that a good number of people in the Northwest of England, Southwest Scotland and Wales saw their biggest snowfall of 2012/13 (for some their biggest in decades) in mid March, so, you know, plenty of time left for snow still

[WhiteFox]

Amateur question re the models. Does anyone follow the model output in the area for, say, areas around the great lakes? I am just curious as to whether they have all the model drama we have in this country or whether their model watching is much less up and down.While I realise that we are an island and a million other factors make us and for example Toronto different, would a model watcher in the US be able to say with certainty at the range we are looking at that moment that 'x' will be happening a week in advance I. E. The recent big freeze over there? Did GFS Nail that 10 days before with very little wobbles?

The answer is no! When I lived in New York every developing potential NorEaster was followed just as closely with exactly the same emotions as we get on here with Easterlies. Lots of hair-pulling and denial when what looked like a promising dumping for New York at 168 hours turned into a washout by 72 hours. So, it's the same everywhere.

Even in Minneapolis, where cold is guaranteed, PPN is not, so there is always a search for snow going on!

[Downpour]

 It's not so straightforward (nor has it been even since yesterday). MOGREPS-15's 00z suite was indeed less bullish about a colder solution and equally offered a more mobile signal throughout next week's 'event'. However, for now at least, UKMO have erred somewhat more towards the EC-NCEP ensemble consensus, i.e., with the easterly regime across the country by later next week with net result of coldest/snowiest to NE; more to normal temps W/SW. In the latter, PPN as rain (.e.g into Weds) but with potential for this to offer snow as it eases NE into colder boundary conditions. Now, inevitably this broad-brush is as far as can be offered, not least given the clear uncertainties on the areal boundary of coldest easterly feed (broad spread on this already very evident and discussed here on the forum). Equally of course, the 12z NWP suites might yet lean more towards the MOGREPS solution and lose the pronounced cold in any meaningful sense... or we could see a reversion back to where we were this time yesterday. In all honesty, there's no smoke and mirrors about this at UKMO - it's just not clear-cut but on balance, as the Dep Chief stresses, might manifest as a fairly typical January cold snap of possibly limited longevity (that's their current view), but nonetheless offering a chance of snow at least to northern areas, possibly to low-levels; and perhaps transiently elsewhere too. Let's await the 12z output.

Thanks for the update Ian. We really appreciate your contribution. 

[Downpour]

Good for you, all I meant was that a good number of people in the Northwest of England, Southwest Scotland and Wales saw their biggest snowfall of 2012/13 (for some their biggest in decades) in mid March, so, you know, plenty of time left for snow still

Oh I agree with your general point. Never underestimate March for snow – can often deliver some real dumpings. It is a wintry month in many years (just as December is often an autumnal one). 

[Staffordshire]

Eyes down for the 12z models, got a feeling this will be make or break, gfs just rolling out now

[cooling climate]

Well I for one think it will be a good afternoon model watching for all of us coldies

out there.Heights rising to the north and northeast with pressure dropping to the

south should aid in Atlantic trough disruption which is being underdone by the

models imo. We should soon find out hopefully.

[nick sussex]

Hi Nick. I think it's more the bearishness from the Office that has put a downer on the thread, rather than the models themselves which, as many have said, are arguing the toss over marginal geographic changes at T100+ range that will in any event vary numerous times before we get there. Many members – and I include myself – are wondering why the Office are saying "no" to a cold blast despite NWP to the contrary. 

 

 

Hi the issue for them is probably how far west any cold gets because of the models chopping and changing with the trough position and orientation, upstream you do have a pattern that will pull the Azores high west now between that and the block is that troughing, the main issue IMO is how long that takes to clear and separate allowing the high to ridge west.

 

The more amplified the pattern is over the eastern USA the sharper the troughing will be this will help to disrupt it, anyway the dramas about to start!

Edited January 9, 2014 by nick sussex

[Downpour]

GFS 12z rolling out...

[fergieweather]

 

Hi Nick. I think it's more the bearishness from the Office that has put a downer on the thread, rather than the models themselves which, as many have said, are arguing the toss over marginal geographic changes at T100+ range that will in any event vary numerous times before we get there. Many members – and I include myself – are wondering why the Office are saying "no" to a cold blast despite NWP to the contrary.

THEY AREN'T!!!I just re-iterated that above: they expect the easterly feed across UK established by later next week, BUT the degree to how pronounced this becomes; the areal scope of below-average temps (i.e. E-W, N-S); the propensity for snow; plus the longevity are all unknowns.So to be clear (again): for now, the lean towards the EC-NCEP colder solutions BUT note that MOGREPS is less bullish (and might yet prove correct).You will not hear terminology like 'cold blast' from Exeter at this juncture, because in their view, it's just standard January colder fare - contra Daily Express hyperbole.

[AWD]

Negatively tilted trough on the 12z GME;

[Cecil Hogmanay Melchett]

Low in the Atlantic slightly less intense than the 06z run at t54.

I'd like to think thats a positive sign

[Ali1977]

Not sure if this is good but, at T54 the low in the Atlantic is 100k ish further West

[karlos1983]

has a set of 12z ever been so nervously anticipated. speaking for myself that's a No!

[UV-RAY]

Well I for one think it will be a good afternoon model watching for all of us coldies

out there.Heights rising to the north and northeast with pressure dropping to the

south should aid in Atlantic trough disruption which is being underdone by the

models imo. We should soon find out hopefully.

I think it was the MetO update that took the wind out of my sails, but now Ian has kindly  given the reasoning behind this I'm inclined to agree with you somewhat. Eyes down for 12z.

[Ali1977]

10 mb higher pressure over Greeny at T66