General Model Output Discussion

[Duane S.]

Into next week I am VERY interested to see what actually occurs. Most charts are quite bullish about the polar vortex splitting to some degree. I have to admit I wasn't expecting this considering how cold (and for how long) the Stratosphere has been. Goes to show how many forces there are out there conflicting with each other!

The MJO forecast seems quite adamant that it will amble around phase 4 before edging towards phase 5, so I guess all eyes should be to Scandinavia later on in the month??

The AO and the NAO are showing no sign of a recovery to some sort of positive state, there are no real tangible signs that the Northen arm will be firing up any time soon. So, I would say whilst all that is the case our weather will remain very interesting.

My take is that the Southern half of the UK will eventually see a return to mild(er) conditions but the Northern half is likely to remain very much on the cold side.

[TEITS]

Max temps of -28C!

http://www.wetterzentrale.de/pics/Rtavn30017.png

I might be a hardcore ramper but even I wouldn't want that pool of cold air to hit us!

[weather eater]

I see the set in concrete return of the Atlantic seems to have passed the GFS 06z run by. All that really shows is that the devil is always in the detail, and that detail has to be at very short range before drawing any conclusions.

[mushymanrob]

Eh, the GFS certainly doesn't - it has backtracked somewhat from its previous suggestion with high pressure once again building over Greenland and the jet heading south. Less cold yes, but certainly not mild by any stretch of the imagination. Think you're going to have to wait a bit longer for those mild temperatures you desire Rob

what i see (on the few models i get to view) is a general trend away from full blown 'freezing' to less cold, even towards mild (albeit in deep fi). ok each run varies, and offers cold sometimes mild others, but a few days ago all were cold. they arnt now. ok nothings set in stone, the milder weather might not win out, i think something between mild and freezing could well be the outcome (yep, misty, grey, dull, slow thaw cold but not freezing)... but that all depends upon the behaviour of the expected atlantic trough ... so imho the trend is away from these bitter synoptics towards less cold and possibly eventually mild.

could be some fun and games though as the battle commences!

[Duncan McAlister]

More signs than yesterday that the cold spell may come to an end at the end of next week. Still a week away though and a lot could change. Even if it does get milder I don't think too many of us could complain!

[NorthNorfolkWeather]

I see the set in concrete return of the Atlantic seems to have passed the GFS 06z run by. All that really shows is that the devil is always in the detail, and that detail has to be at very short range before drawing any conclusions.

We're back to the "to and fro" of the old GFS, which is amazing as when this was the parallel run, it seemed to be doing much better.

Overall, for the next week, Scotland to remain very cold, but the minima may be rather higher than the last few days. Wales, Northern Ireland, Northern England, down to the midlands, above a line from Bristol to the Wash, a touch warmer, but not mild, and, apart from the wind over the next couple of days, not a lot happens. South of that, fun and games. Maybe, as Ian Brown has alluded to, we may have a truely memorable dump of snow, but, on the other hand if the low travels more than 150 miles further south, it will be windy, but relatively dry.

a difference of 150 miles over a 3,000+ miles track is not much. JH said yesterday that the outlook is a forecasters nightmare, I think he's hit the nail on the head. Again, we'll be down to nowcasting at the end of it

[NorthernRab]

what i see (on the few models i get to view) is a general trend away from full blown 'freezing' to less cold, even towards mild (albeit in deep fi). ok each run varies, and offers cold sometimes mild others, but a few days ago all were cold. they arnt now. ok nothings set in stone, the milder weather might not win out, i think something between mild and freezing could well be the outcome (yep, misty, grey, dull, slow thaw cold but not freezing)... but that all depends upon the behaviour of the expected atlantic trough ... so imho the trend is away from these bitter synoptics towards less cold and possibly eventually mild.

could be some fun and games though as the battle commences!

That's all very well Rob, but your original posted stated that mild temperatures would make their way in to the UK by next week, this doesn't at all seem to best the case as 10'C day time max temperatures only just make it in to Cornwall and Devon by Sunday night (17th). Indeed, the GFS shows a push over VERY cold air towards eastern europe and Scandinavia.

[Climate Man]

You may be surprised, I predicted little or no breakdown over Christmas and this was correct. The models are struggling and whilst it may be a litttle less cold at times I believe that temps will stay below normal and a breakdown will continue to be pushed back.

[Frosty.]

I see the set in concrete return of the Atlantic seems to have passed the GFS 06z run by. All that really shows is that the devil is always in the detail, and that detail has to be at very short range before drawing any conclusions.

We have to take the the 6z with extreme caution because this run is frequently trashed every day when it doesn't show what we want to see. A step in the right direction though for hardcore coldies.

Edited January 8, 2010 by Frosty039

[sandstorm2]

Am I right in saying that the GFE has done an about turn and the ECM is the one wanting to bring in less cold weather next week, the GEM on the other hand keeps it very cold right throughout its run, haven't looked at the UKMO. I think the models are having real problems dealing with the situation.

Maybe one or two of the more knowledgeable members can have a look and see what they think.

SS2

[weather eater]

We're back to the "to and fro" of the old GFS, which is amazing as when this was the parallel run, it seemed to be doing much better.

Overall, for the next week, Scotland to remain very cold, but the minima may be rather higher than the last few days. Wales, Northern Ireland, Northern England, down to the midlands, above a line from Bristol to the Wash, a touch warmer, but not mild, and, apart from the wind over the next couple of days, not a lot happens. South of that, fun and games. Maybe, as Ian Brown has alluded to, we may have a truely memorable dump of snow, but, on the other hand if the low travels more than 150 miles further south, it will be windy, but relatively dry.

a difference of 150 miles over a 3,000+ miles track is not much. JH said yesterday that the outlook is a forecasters nightmare, I think he's hit the nail on the head. Again, we'll be down to nowcasting at the end of it

Yep the likes of Mr Holmes and GP have been pretty much spot on. GPs analysis that the lows will undercut the UK are certainly demonstrated on the 06z run. I always find it really odd how some get taken in by a couple of runs jumping onto an apparent new trend, how often have we seen this happen, the models have a day of uncertainty only to revert to an earlier evolution on later runs. It might well be that this mornings 00z runs are on to a new trend but I think I’ll wait awhile before jumping to any conclusions.

[BLAST FROM THE PAST]

Folks

Model detail will change BUT THERE IS A BREAKDOWN COMING just as much as this cold spell was coming. The dates are 12-20 but mainly from 14th where New Moon influence comes in. An attack from the SW approaches, two shots, snowy breakdown. First won't do damage to cold but will bring heavy snow, second will signal the breakdown [but maybe not for the NE UK]. Last week to 10 days for sure will be less cold to average but cold to very cold up until then. Still looking at Feb [enjoy what we have because it could be 'horribly mild'...but signals are conflicting at the mo.

BFTP

Edited January 8, 2010 by BLAST FROM THE PAST

[Strider]

...So according to GFS, the Jet Stream will continue it's holiday in the southern hemisphere until around Thursday, then it'll be coming right through your back garden!

[Hammer]

Folks

Model detail will change BUT THERE IS A BREAKDOWN COMING just as much as this cold spell was coming. The dates are 12-20 but mainly from 14th where New Moon influence comes in. An attack from the SW approaches, two shots, snowy breakdown. First won't do damage to cold but will bring heavy snow, second will signal the breakdown [but maybe not for the NE UK]. Last week to 10 days for sure will be less cold to average but cold to very cold up until then. Still looking at Feb [enjoy what we have because it could be 'horribly mild'...but signals are conflicting at the mo.

BFTP

Blast yesterday you mentioned cold to remain to at least 22nd poss 24th, do you mean attempts at breakdown between 12th and 20th, and they may fail, the cold or less cold could last out to 24th.

So Wednesday onwards next week is a date to keep an eye on, it would seem, as to a possible start of breakdown, snowy at that.

Edited January 8, 2010 by Hammer

[Thundery wintry showers]

GFS 06Z goes with yesterday's ECM in sliding the low to our south and keeping things pretty cold with easterly winds like yesterday's ECM, but with slightly less cold uppers, so dry and cloudy would be the most likely result for next week.

With UKMO and ECMWF backing some kind of incursion of milder weather from the south, the possibility has to be taken a lot more seriously now, as the UKMO/ECM have been much better than the GFS recently (albeit not foolproof- this is quite a significant backtrack from the ECM). But to me, it doesn't look particularly convincing, with even the ECM operational run holding the block firm to our east and eventually sending it back west again at T+240.

Ensembles for GFS and ECM still seem to support the "slider" solution that yesterday's ECMWF showed. At the moment I think we have a 20% chance of the whole thing breaking down, 40% chance of a temporary warm-up late next week, and 40% chance of the cold staying locked in with the milder air confined to the extreme south-west. Note those figures- I don't think the cold will break down so easily on the first attempt like this, it will probably take another attempt or two after that before milder weather eventually takes hold over the whole country.

[NorthNorfolkWeather]

A couple of charts of the Northern Hemisphere 500.

First is at T156. Vortex is distinctly split with 3 centres,

But at T360 (far FI I know), but it's back to one centre which is much more likely to produce our normal zonal weather.

Personally, I think the GFS is overdoing the reunification of the PV, much more likely that it will still be split, maybe at a lower level, with perhaps just 2 centres. If that is the case, it's really all about where those centres are

[Iceberg]

What the GFS shows to me is a model that hasn't got a clue still, It wants to bring the atlantic in, but never quite succeeds, blocking is still the form horse, still no agreement on how we will get rid of the cold and until there is, cold to stay has to be the favourite.

The ECM London Ensembles show that the ECM ops 00Z was far milder than the average, and that the ensembles are predicting the cold to continue with the average max temp not getting above 4C for London at all and it goes out to the 23rd of Jan.

The GFS 00Z was equally a mild run with little support.

The models are still suggesting that a return to average is not really in sight atm.

[casparjack]

Max temps of -28C!

http://www.wetterzen.../Rtavn30017.png

I might be a hardcore ramper but even I wouldn't want that pool of cold air to hit us!

Don't be a spoil sport why not!!?

[nick sussex]

It's funny how the model merry go round continues with the gfs jumping back onto the colder scenario. NOAA this morning think the ecm and gfs operationals are at each end of the spectrum so have gone with the GEM and GEFS ensemble mean which if you want the cold to continue is a positive sign. I think whatever happens it's been a great cold spell for the UK. For people worried about any southerly or se flow which may happen with certain models,here in sw France we missed the worst of that Med winter storm but still have a good covering of snow with current temps here at -3c. The cold is expected to ease here by Tuesday but further north there will be alot of cold air for the UK to draw on in that circumstance.

In these situations even if the upper air temps recover it takes some time for the same rate of recovery at the surface as the embedded cold and snow cover drag these down. Also unless there is a major change to the AO and NAO and given that the flow across the USA is expected to flatten out then the cold pool over the UK together with higher heights to the ne will act together like a weight doing their best to cause shortwaves to track to the sw.

So although we see some movement towards a possible breakdown the fact that this is coming more likely from the sw means it's not straightforward and could well take several attempts or even fail completely given the current state of the AO and NAO.

If the ukmo think theres likely to be a breakdown i'm sure this will be highlighted in their further outlook when it's updated later today.

Edited January 8, 2010 by nick sussex

[Duane S.]

I must admit, what I do see less and less of every day is any sort of reload situation. I think the end is near, let's just hope it goes out with a fight and not a whimper!

I agree with BFTP comments about February, it is showing all the signs of being a bit of a horror show (unless you are Mushymanrob of course ). Whether or not some sort of MMW can hurry up and get going to help avert it remains to be seen.

But.. whatever happens from now on in, this will go down as a classic and memorable winter for all the right reasons for sure!

EDIT: I'm talking IMBY for 'the end', those in the North will be able to cling on for a fair bit longer IMO

Edited January 8, 2010 by s4lancia

[casparjack]

It's funny how the model merry go round continues with the gfs jumping back onto the colder scenario. NOAA this morning think the ecm and gfs operationals are at each end of the spectrum so have gone with the GEM and GEFS ensemble mean which if you want the cold to continue is a positive sign. I think whatever happens it's been a great cold spell for the UK. For people worried about any southerly or se flow which may happen with certain models,here in sw France we missed the worst of that Med winter storm but still have a good covering of snow with current temps here at -3c. The cold is expected to ease here by Tuesday but further north there will be alot of cold air for the UK to draw on in that circumstance.

In these situations even if the upper air temps recover it takes some time for the same rate of recovery at the surface as the embedded cold and snow cover drag these down. Also unless there is a major change to the AO and NAO and given that the flow across the USA is expected to flatten out then the cold pool over the UK together with higher heights to the ne will act together like a weight doing their best to cause shortwaves to track to the sw.

So although we see some movement towards a possible breakdown the fact that this is coming more likely from the sw means it's not straightforward and could well take several attempts or even fail completely given the state of the AO and NAO.

I think the point about surface cold being embedded is very relevant, my 30cm soil sensor is at 1.1c under 15cms of powder snow, the lowest ever, that is an awful lot of locked in cold for the Atlantic to handle even if it does get in for a few days.

I did a comparison of the three main models earlier at T+144, at first glance they all looked quite similar, but on further consideration the UKMO looked the most progressive bringing in the low, as has been said on here many times before, what a shame it doesn't go to T+168 as thjat might hold the key to where we go after that...

Guess we'll have to wait until later/tomorrow - as ever!!

[derrylynne]

I must admit, what I do see less and less of every day is any sort of reload situation. I think the end is near, let's just hope it goes out with a fight and not a whimper!

I agree with BFTP comments about February, it is showing all the signs of being a bit of a horror show (unless you are Mushymanrob of course :lol: ). Whether or not some sort of MMW can hurry up and get going to help avert it remains to be seen.

But.. whatever happens from now on in, this will go down as a classic and memorable winter for all the right reasons for sure!

EDIT: I'm talking IMBY for 'the end', those in the North will be able to cling on for a fair bit longer IMO

Given the solar conditions I would be very surprised to see February turn out to be anything like mild. There are bound to be milder interludes as shown on the charts, although these in my mind are very likely to be temporary. There were many instances in the winter of 1963 when milder air tried to get in, but simply did not make it. The GFS of course is programmed for 'modern winters' - and finds it hard to handle these kind of synoptics. The fact though the other models are going for some kind of breakdown indicates that something is going on though, and that some milder, not maybe the steaming Atlantic, may make it in - albeit for a short time. With the AO staying in our favour, and the jet stream seemingly staying further South, conditions will always be right for a reload. Be interesting what the next 24 hours bring in the charts. Ok I am not as expert as many others on here chart wise - but just putting in my ten pennyworth as to my thoughts......

[Duane S.]

Given the solar conditions I would be very surprised to see February turn out to be anything like mild. There are bound to be milder interludes as shown on the charts, although these in my mind are very likely to be temporary. There were many instances in the winter of 1963 when milder air tried to get in, but simply did not make it. The GFS of course is programmed for 'modern winters' - and finds it hard to handle these kind of synoptics. The fact though the other models are going for some kind of breakdown indicates that something is going on though, and that some milder, not maybe the steaming Atlantic, may make it in - albeit for a short time. With the AO staying in our favour, and the jet stream seemingly staying further South, conditions will always be right for a reload. Be interesting what the next 24 hours bring in the charts. Ok I am not as expert as many others on here chart wise - but just putting in my ten pennyworth as to my thoughts......

And you make some very good points. Although a negative AO, even a deeply negative AO does not equal cold conditions for the UK. A while ago I did a correlation study between a -AO (below -2 I think it was) and cold conditions for the UK and although it showed that it certainly improved our chances, other factors could sometimes override it and leave us with mild conditions. I think as long as we see the NAO play ball and not suddenly shoot upwards we are going to be staying on the cold side for a while to come yet.

Edited January 8, 2010 by s4lancia

[BLAST FROM THE PAST]

Blast yesterday you mentioned cold to remain to at least 22nd poss 24th, do you mean attempts at breakdown between 12th and 20th, and they may fail, the cold or less cold could last out to 24th.

Yes attempts between 12-20. Remember further N / E you are the longer it'll last. SW to lose cold first BUT only relevant to how cold its been. I doubt the rapid breakdown by some models shown will occur, the block and cold is strong and the jet is south.

BFTP

Edited January 8, 2010 by BLAST FROM THE PAST

[Thundery wintry showers]

I think the days of this cold spell are numbered and that it's only a matter of time before the lows come in from the SW, because it looks unlikely that the high will move over to Greenland which is what would be needed to continue the pattern of alternating easterlies and northerlies. It may take just a week but I'm expecting it to be more like two or three weeks due to the strength of the block, which is why I'm not convinced by the UKMO/ECM breaking it down next week.

For me, the real "meat" of the wintry spell is destined to be over by next week regardless, for while it will probably remain cold & snowy for some time yet, we will lose the theme of sunshine and snow showers which has dominated proceedings since the 17th December. But of course for those who are looking for big frontal snow events, and particularly if they haven't seen many snow showers recently, the next 2-3 weeks could turn out to be the real meat of the spell. Other than that, the easterly flow will be more stable, cloudier and with less in the way of showers.

Regarding February I'm pretty sure it will be milder and will have some spells of south-westerlies. However I'm not convinced that it will be mild all the way through. My eye turns to the Februarys of 1966 and 1985, both of which followed cold snowy Januarys and were mild early and late but had an easterly spell in the middle, which in the case of 1985 was enough to make it a fairly cold month overall.