Model Output Discussion - 1st - 7th January

[SP1986]

Personally I wouldn't use the De Bilt ensembles to show temperature trends, unless there is a genuinely large chance of an easterly occurring, because De Bilt is much more prone to continental influence than the British Isles in general.

As for the ECM, well it's good in terms of weather types, a period of dry weather away from the south-east would be beneficial at the moment, and cooling down with that scenario too, somewhat. Inversions are not always evident in high pressure, it depends on the airmass, the direction of air movement etc, so if that occurs we'll have to see whether inversions occur.

I don't see anything actually cold on the runs, aside from the potential cold thereafter, but a move away from a persistent Atlantic pattern is likely, and probably welcome in most cases.

(I ask kindly for my post not to be jumped on because I am not necessarily championing the snow ramping ethic*)

[legritter]

yes ,enjoy the ride .we are starting to see what most of us wanted . cold air coming into europe , the atlantic slowing down ,the models at longer range will always chop and change , just think as iv pointed out before 50 miles plus per day over next 240 hrs = 500 miles at least =,all that high pressure could finish up in the right place gang , i know there are other types of physics involved but the bottom line is the heavier the amount of molecules above a given place especially if warmed up ,the higher the pressure , im sure we have a possible strat warming event now about to show its hand . hope im right , going by my limited knowledge of strat warming , and iv read the posts from our threads ,north america , canada and astronomical sights , also quarterly journal , but its a bit thechnical ,but still informative , anyhow going by this i will stick my head out and say continental feed by 12th jan cheers

[kold weather]

I don't see anything actually cold on the runs, aside from the potential cold thereafter, but a move away from a persistent Atlantic pattern is likely, and probably welcome in most cases.

I think thats a pretty good sentence to describe the model output at the moment. Certainly hints of something better down the line but the models still are not showing anything other than 'normal' conditions...alas that can change quite quickly in the world of weather!

[Liam J]

(I ask kindly for my post not to be jumped on because I am not necessarily championing the snow ramping ethic*)

This isn't the cold & snow hunt thread so nobody should have any reason for jumping on you after giving a balanced interpretation of the current outputs

We may well be looking at the beginnings of a pattern change which would take us away from the current Atlantic driven scenario, certainly nothing overly cold on offer but as you mention the potential cold could follow, lets just get the change in place first and not start to run before we can walk.

[bobbydog]

i have to say, it would be great if we could get a measured assessment of the trend of the models, even over a 24 hour period. as opposed to a thread that appears to 'mood swing' every 6 hours. i have a rough idea how to read the charts, however it is very difficult to pick out the bits that matter, when we constantly get 'dire run for cold' then 6 hours later ' much better run for coldies' the meto dont update their forecast every 6 hours, so they must look at the trend rather than each individual model run. some people seem to react to each run like it is written in stone! even with my rudimentary knowledge of the models, i know it doesn't work like that. even i know that there are about 20 ensembles to choose from so i'm not taking the op as gospel. its like watching a bee flying towards its destination- they never fly in a straight line.....

rob

[Jason M]

Two separate clusters showing up in the ECM ensembles for De Bilt:

http://www.knmi.nl/e...M_06260_NWT.png

The operational run is the coldest right at day ten, before that the ensembles go their separate ways, you can tell by looking at the ECM ensemble maps at 168hrs which members have the best chance of bringing a colder continental feed into the UK.

For the UK as a whole member 37 gets my vote!

http://www.ecmwf.int...t!2009112700!!/

There is quite a spread of solutions regarding the placement of high pressure , still waiting for the extended ensembles to come out.

Hi Nick

De Bilt ensembles may be a bit misleading for us in this set up as if the high sits over the top of the UK De Bilt will be a fair bit colder than London say as the colder air sinks into Europe but fails to back west.

I'm praying it won't happen, but experience is screaming 'UK High' followed after a couple of weeks by another spell of zonality as the high sinks again. There now seems increasing agreement between the models and GFS enemble suite on the first stage of this set up. Renewed zonality is usually the outcome from that although it could take a couple of weeks. This isnt a reaction to one set of runs, its been a trend for a couple of days that is gathering speed.

To me, this is the nightmare scenario as it effectively writes of January if it comes to pass (ie 10 days for the high to settle over us, 10 days for it to clear off followed by minimum 10 days zonal period).

Jason

[Stormyking]

Right 18z should be starting to come out, will be interesting if it can continue to show the potential pattern change

[nick sussex]

Personally I wouldn't use the De Bilt ensembles to show temperature trends, unless there is a genuinely large chance of an easterly occurring, because De Bilt is much more prone to continental influence than the British Isles in general.

As for the ECM, well it's good in terms of weather types, a period of dry weather away from the south-east would be beneficial at the moment, and cooling down with that scenario too, somewhat. Inversions are not always evident in high pressure, it depends on the airmass, the direction of air movement etc, so if that occurs we'll have to see whether inversions occur.

I don't see anything actually cold on the runs, aside from the potential cold thereafter, but a move away from a persistent Atlantic pattern is likely, and probably welcome in most cases.

(I ask kindly for my post not to be jumped on because I am not necessarily championing the snow ramping ethic*)

In terms of De Bilt I do agree regarding that its location means its more likely to be effected by a continental influence but it still gives us an idea of trends, as we can see from the extended ensembles any high pressure is likely to get flattened as the main clustering goes less cold, the cold outlier by the operational is due to the winds falling out under a surface inversion,however before the operational becomes a cold outlier there is a decent clustering supporting it, this is where the ECM ensemble maps come into their own.

And you can see here by looking at the spreads:

http://www.meteociel.fr/modeles/ecmwf.php?ech=192&mode=1&map=0&type=2

And following the run through to 240hrs, possible troughing over northern Italy, and whats that to the north!

Of course the smart money is on any ridging not getting far enough north because of the jet but perhaps a chance for at least some surface cold before the high is likely to get flattened by the jet.

[Frosty.]

I think thats a pretty good sentence to describe the model output at the moment. Certainly hints of something better down the line but the models still are not showing anything other than 'normal' conditions...alas that can change quite quickly in the world of weather!

I'm looking forward to the normal weather, it was such a mild christmas but a colder week coming up with some of the white stuff although mainly on hills and some signs in the models and ensembles of pv disruption, IMO we have made a bit of progress since 25th/26th dec.

[phil nw.]

I think thats a pretty good sentence to describe the model output at the moment. Certainly hints of something better down the line but the models still are not showing anything other than 'normal' conditions...alas that can change quite quickly in the world of weather!

Yes i agree.We have mixed zonality for a while yet.Any likely changes are beyond the current period of High resolution modelling, and likely just outside the ECM range yet.

I did allude to this in my earlier post.

As i said in the StratoThread,the likely change to wavelength patterns does not gaurantee immediate cold for the UK-we still have to be on the right(cold)side of any troughing as the cold air comes south.

Edited January 1, 2012 by phil n.warks.

[bluearmy]

I'm praying it won't happen, but experience is screaming 'UK High' followed after a couple of weeks by another spell of zonality as the high sinks again. There now seems increasing agreement between the models and GFS enemble suite on the first stage of this set up. Renewed zonality is usually the outcome from that although it could take a couple of weeks. This isnt a reaction to one set of runs, its been a trend for a couple of days that is gathering speed.

To me, this is the nightmare scenario as it effectively writes of January if it comes to pass (ie 10 days for the high to settle over us, 10 days for it to clear off followed by minimum 10 days zonal period)

jason, given the developing polar profile, i doubt we will have zonality following a mid lat high sat close to us. infact, given the pushing and pulling already evident on the fi charts, i'm not sure how long a mid lat high will be able to stay too close to the uk.

ian's point about WAA with the current p/v location is well made and fwiw, i think that Baffin is likely to be its destination

[Jason M]

jason, given the developing polar profile, i doubt we will have zonality following a mid lat high sat close to us. infact, given the pushing and pulling already evident on the fi charts, i'm not sure how long a mid lat high will be able to stay too close to the uk.

ian's point about WAA with the current p/v location is well made and fwiw, i think that Baffin is likely to be its destination

I take your point, and hope your right because if we do manage to drag an easterly out of this its likely to be a 'good un'. I'll stick to my guns for the moment though .

[Zakos]

PV looking much weaker already on the GFS 18z compared to the 12z.

[Osbourne One-Nil]

But comparing the 18z to the 12z is like comparing apples and pears....or so I'm lead to believe.

[SMU]

A fairly dramatic change in the last 24 hours-

First picked out by the 00z ECM then the 06z GFS & then some consolidation on the 12z ensembles from the ECM-

I think The overall NH 500 MB LONGwave pattern looks quite well modelled by the ECM with the vortex getting kicked NW, however we have been here before & the models dont always capture a proper Scandi high on Each run, so the placement of that 'cell' could well be furtehr NW- remember the model response often overuns the scandi high before it gets a hold, however when we approach its full development they last longer & amplify the pattern more-

The issue with the NW europe plots from the models is that that 'shunt' of the Azores high & possible scandi high say 1000 miles NW ( as depicted by the 00z ECM V the 12z ECM) has a dramatic effect on our little 'patch- because there be some CAA under the southern flank- its whether this runs through france & towards Spain, or whether the UK gets in on the act under the block..

Things also remain positive across the polar heights- seeing them rise to +VE values out of the aleution highs- this will send the AO index hopefully below -1 for the first time this winter ( day 12 range)

All in all very positive runs today=- I think the ECm 12z is to far SOUTH EAST with the WAA plume at 144-

18z GFS will look to be better!!

FWIW this is the WAA plume depicted by the GFS 18z

http://176.31.229.228/modeles/gfs/run/gfsnh-5-138.png?18

regards

Steve

Edited January 1, 2012 by Steve Murr

[Zakos]

But comparing the 18z to the 12z is like comparing apples and pears....or so I'm lead to believe.

oh yes I am aware of this. Its only one run, but I'm just pointing out that the trend is for upgrades, which is good sign , for coldies.

[BLAST FROM THE PAST]

Maybe we are now beginning to see the change and not just a model blip, timing 7-10 Jan looks good BUT my niggle remains. However, of the two scenarios I mentioned ie LP tracking south up channel or LP moving on NW/SE steep angle with pressure rise behind and advection west of cold HP from east, it looks that latter is the set up to watch/I prefer. 'Watch' that is, as plenty to happen and develop yet BUT looking E/NE was the early word for Jan and that remains...not NW.

Lets see what happens but I bet these very recent charts have stirred a little.

BFTP...Happy new year

Edited January 1, 2012 by BLAST FROM THE PAST

[Matty M]

I wonder in the coming 2-3 days could be see a dramatic shift at around T144hr + and turn what looked like a toppler into something more significant?

A New Year and new hope.

[Geordiesnow]

18Z shows a slightly more amplified ridge in the medium range thus a slightly better and longer flow from the North but very little proper cold to play with so the uppers are reasonable but unspectacular but there should briefly be some snow for Northern Scotland/Shetland before the high slowly topples.

Theres also a cold shot attempt but it topples even before it wants to be begin!

Even though my posts have been downbeat, at least the output does not look too mild for the time of year, should see more polar airmasses than tropical maritime airmasses in the coming week but sadly any cold does not look strong enough to suggest that we should be dusting off the sledges anytime soon but at least the GFS is trying to break the PV up.

[Cecil Hogmanay Melchett]

All I see is the azores high ridging NE towards the UK and then being flattened out by the jet.

Quite baffled by some of the posts TBH and if i was looking for cold,personally i'd be thinking NW,certainly not NE.

[Matty M]

Best chart i have seen all winter to be honest.

Cold wise!

[mountain shadow]

Maybe we are now beginning to see the change and not just a model blip, timing 7-10 Jan looks good BUT my niggle remains. However, of the two scenarios I mentioned ie LP tracking south up channel or LP moving on NW/SE steep angle with pressure rise behind and advection west of cold HP from east, it looks that latter is the set up to watch/I prefer. 'Watch' that is, as plenty to happen and develop yet BUT looking E/NE was the early word for Jan and that remains...not NW.

Lets see what happens but I bet these very recent charts have stirred a little.

BFTP...Happy new year

Glad to see both yourself and Steve M remain positive, however with charts like this at ten days out..

http://hw.nwstatic.co.uk/gfsimages/gfs.20120101/18/240/npsh500.png

There is more chance of Pat Butcher's resurrection than a snowy spell.

[Matty M]

Glad to see both yourself and Steve M remain positive, however with charts like this at ten days out..

http://hw.nwstatic.c...240/npsh500.png

There is more chance of Pat Butcher's resurrection than a snowy spell.

But why does that have to come off?

It doesn't

Although i understand it is probably a lot more likely than the option i am thinking of!

[JP1972]

This isn't the cold & snow hunt thread so nobody should have any reason for jumping on you after giving a balanced interpretation of the current outputs

We may well be looking at the beginnings of a pattern change which would take us away from the current Atlantic driven scenario, certainly nothing overly cold on offer but as you mention the potential cold could follow, lets just get the change in place first and not start to run before we can walk.

Perhaps a bit of a weak comment to make but ...

Surely looking at the bigger picture and the winter season thus far, a change to a colder set up further down the line would have to be more likely than not based on law of averages, particularly bearing in mind the Strat warming.

Or am I talking tripe?!

Edited January 1, 2012 by JP1972

[Geordiesnow]

All I see is the azores high ridging NE towards the UK and then being flattened out by the jet.

Quite baffled by some of the posts TBH and if i was looking for cold,personally i'd be thinking NW,certainly not NE.

Well it actually tries to ridge towards Greenland but it does not break the PV up therefore the high starts to topple however I think what the GFS is saying at this range is quite a low possibility because of the ECM/UKMO outputs which are alot flatter and we know the pub run likes to lead us on one.

Suppose we got to start from somewhere though and we might see upgrades but whilst the models are trying to break up the PV with height rises to our North/Azores high, I'm still unsure about any snowy spell.