Model Output Discussion - 18z - 25th Nov onward

[Weathizard]

I like the NOGAPS at 144hrs

And does anyone have a link to the major american models for the eastern seaboard so we can have a look at them, I seem to remember someone posting a chart from the AMA or something which was the American Model.

Edited November 26, 2012 by Weathizard

[The Eagle]

UKMO now following (as usual) GFS and ECMW:

UK Outlook for Saturday 1 Dec 2012 to Monday 10 Dec 2012:

Wintry showers are expected to affect some eastern areas on Saturday with snow on hills, possibly to low levels in the north. Elsewhere, largely dry and fine, but cold with the risk of frost, icy patches and overnight freezing fog. By Sunday, rain may spread into the far west, preceded by snow, mainly over higher ground. There is a lot of uncertainty for the remainder of the period but it is likely that northern and eastern areas remain cold with wintry showers for some. Elsewhere, it will probably become milder, at least for a time, but also more unsettled, with rain and hill snow accompanied by stronger winds. Later in the period, colder but drier conditions may become re-established across the UK, with frost and icy patches for many.

Updated: 1107 on Mon 26 Nov 2012

Hopefully the second shot will be more fortuitous.

That may be the case but the factual evidence is that on Sunday their model has us on the cold side of the polar front

I'm happier than I was last night. The ECM has come more toward where most of us want it to be. It's not quite there yet. Hopefully better on the 12z.

[andymusic]

In a strange sort of masochistic way I'm quite enjoying this latest model drama! It's certainly more compelling viewing than anything on the tv at the moment.

Going back to SM's post he sums things up very well , thanks again SM for all your in depth analysis.

It really is impossible to say exactly how this will turn out and so we just have to wait and see what happens off the eastern USA.

In the meantime I'm teleporting myself over to the eastern USA and will be trying to find as much info as possible on what could happen!

gotta agree with you there Nick - TOO MANY FLIPPING REPEATS - anyway it does look like the meto have made some changes this morning - 5am according to their update - and slightly milder weather (with some possible hill snow) will feature in the south rather than yesterdays output of full on snow and cold for the weekend - so the pro forecasters are seeing the minute "milder blip" changes and responding to this! - this is definitely better than any of the soaps - "tune in next week to see how the raging blizzard comes in and takes over Albert Square! LOL

[bradymk]

A last chart before we recess before the 12z. I have project work to do :'(

Comparing the NAM 6z and GFS 6z @T84hrs

I know which one i prefer!

GFS

NAM

Yes the NAM is encouraging, however a slight rise in temperature looks more likely now for a time but the long range prospects are still very encouraging. Even if the 12z are bad news in the short term, im weirdly excited to see what their output is, have we ever had so much disagreement before t96? Looking forward to seeing where they go, keep an eye on the higher res models like NAM and GME. Matthew

[bluearmy]

i think that had nov/dec 10 not happened, with its clockwork countdown, this would be a much more reasonable thread. steve, stewart and ian F have given good advice this morning. its the weather - its complicated - nothing is certain. maybe an episode like this one is good to have as we approach winter. those of you fortunate enough not to have been watching the models prior to dec 2010 may now have a good idea of what model watching was normally like for the uk on the cusp of a cold period. and most of the time, the cold spells never verified and we got a two day toppler.

fwiw, it looks like the first half of dec will be below av tempwise but that doesnt mean a countrywide freeze with deep snowcover. cold, dismal and drizzly is probably still below average. also, the way the models are currently moving, the interaction between cold and not so cold is generally when we see our most impressive snowfalls. (although the norm for the uk is for them to melt within a few days)

Edited November 26, 2012 by bluearmy

[Catacol]

Seems like a parallel universe with the modelling I'm seeing and the reasoned assessment of teleconnectors compared to some other interpretations doing the rounds. The interesting period emerging where we establishing just where residual bits of polar vortex are positioned.

At the crucial t72-96 range, ensemble means and the balance of operationals appearing to suggest the troughing south of Greenland will disrupt allowing for an advection westwards of the cold air and lowering of pressure across Europe.

At t144-t168, we have some reasonable agreement for the second low to break through and head SE towards the European trough. Losts of complications there yet to be resolved but with blocking signature still in place to our north, probably not going to alter things too much - likelihood that the low will become adbsorbed with the main European trough with a temporary rise in temperatures towards average before falling away again, The mean temperature anomaly for the 15 day period looking between 2C and 4C below average (which is not far off ECM mean).

The day 6-10 and 11-15 GEFS H5 anomalies and T850 anomalies still very persistent in suggesting a sustained below average start to December.

Note the persistence of the upper low over Europe and the development of another ridge in the North Atlantic south of Greenland which re-inforces our cold block towards the end of the period. Note also, the ridge over the North Pacific which has not been well modelled in the last week. That teleconnects very strongly with the mid Atlantic ridge solution.

So a cyclonic cold block looks the order of the day for December, pressure higher to the south of Greenland.

The voice of reason which perhaps a few might listen to. Overall pattern is blocked; the nova scotia low in the short term might lead to a temporary 48 hour blip, but otherwise a return to atlantic dominated weather is not going to happen - unless all the ensemble mean products and teleconnective signals suddenly go haywire... and I am yet ever to see that happen (though I guess there is a first time...)

Battleground snow as both IanF and SteveM alluded to looks like the sensible call for next week once the cold has become established by the weekend. Dont even bother trying to work out where it might occur based on operational runs this far out - keep an eye on the means and then look to the high res operationals sub 72 hours once we get to next week.

[ISAAC]

On a side note, synoptics such as the GFS tend to favour marginal snow events. And from experience IMY the best snowfall usually does come from marginal situations.

Some may prefer prolonged cold, frost and snow showers. But who would brush away the chances of a huge snow event regadless of uppues of -3c.

Just saying

[chionomaniac]

i think that had nov/dec 10 not happened, with its clockwork countdown, this would be a much more reasonable thread. steve, stewart and ian F have given good advice this morning. its the weather - its complicated - nothing is certain. maybe an episode like this one is good to have as we approach winter. those of you fortunate enough not to have been watching the models prior to dec 2010 may now have a good idea of what it was normally like for the uk on the cusp of a cold period. and most of the time, they never verified.

fwiw, it looks like the first half of dec will be below av tempwise but that doesnt mean a countrywide freeze with deep snowcover. cold, dismal and drizzly is probably still below average. also, the way the models are currently moving, the interaction between cold and not so cold is generally when we see our most impressive snowfalls. (although the norm for the uk is for them to melt within a few days)

Agree here, Nick.

Too many people are getting confused with a leakage of energy across the Atlantic with a return to zonal conditions. The block appears to be waxing and waning rather than diminishing completely. If you look at one run then this may show the wax, wane or even something more out of kilter. Looking at the anomaly composites that GP has posted they look the same as they did yesterday - so the background signals are not changing here.

One can see the fight in the GFS high resolution that the computing process has trying to work out how much energy to allow through against the background signal. When adding in the other models we see the struggle.

Good posts from Ian F, SM and GP who have all correctly identified this.

[No Balls Like Snow Balls]

To be perfectly honest with the folks looking for a lenghty severe cold spell (including myself :-) today's ECM/GFS 500mb height anomalies may just be starting to suggest a change in the upper air pattern, this is in regards to the GFS and ECM starting to show a short cold spell followed by LP breaking through the block, if you look at the GFS mean it does show a more Wsterly flow in 7-10 days time with lower heights filling the void between Northern UK and Southern Greenland, whilst the ECM mean is different to the GFS it would suggest that when these anamolies are at odds with each other a change in upper air pattern is likely, but it needs at least 3 days of continous agreement to suggest the change is likely to happen

Of course the upper air pattern may not change but there is a suggestion withing the 500mb mean that the GFS and ECM op's showing LP breaking through the block may well be right and we could be heading towards a "milder" few days after the cold spell before possibly the block re-builds again??????

I haven't looked at the NAEFS and the above drivel is just based on todays 500mb ECM / GFS anomalies :-)

[Pixel]

In a strange sort of masochistic way I'm quite enjoying this latest model drama! It's certainly more compelling viewing than anything on the tv at the moment.

Going back to SM's post he sums things up very well , thanks again SM for all your in depth analysis.

It really is impossible to say exactly how this will turn out and so we just have to wait and see what happens off the eastern USA.

In the meantime I'm teleporting myself over to the eastern USA and will be trying to find as much info as possible on what could happen!

Excellent Nick..

if only this had a jet overlay on it : http://www.meteo.psu.edu/~fxg1/SAT_NHEM/animweur.html

would be good to see how the low off the west coast of the states is going to develop and in turn maybe effect what comes out from the east.

It's all a bit like trying to push liquid mercury with the head of a pin to make it go in a favoured direction..! Really enjoying this discusion tho

[Frosty.]

On balance, it looks like the Gfs 06z is a load of old tosh since the latest meto update reads nothing like it. The 6z shows a very zonal outlook with occasionally some aplification that quickly gets flattened out, a fired up raging atlantic with deep fast moving depressions crossing the uk with brief flat ridging seperating the bad weather, at least the flooding risk would be less because the systems would push through quickly but it's a generally awful pattern that we are too used to in our winters. Coming back to this week, at least it turns colder through the week and we finally lose all the persistent heavy rainfall, it becomes much drier and brighter with sunny spells and scattered showers, the showers mainly across the north and east and trending more wintry after midweek, the 6z then shows a ridge pushing in from the west by next weekend and next weekend itself looks cold and bright with frost early and late, quite a crisp wintry feeling weekend with max temps of only 3 or 4c and widely down to -1 or -2c overnight, slightly milder air then pushes east across england and wales next monday with temps returning to near average ( just below), then cooler again as fronts clear through with colder, showery weather but never lasting long and the airmasses rapidly alternate further into FI with some milder interludes, some very stormy spells pop up at times but i'm sure the atlantic fire up is being totally overblown, but that's the gfs for you.

[Jason T]

Still if we went back a year ago....

http://www.meteociel.fr/modeles/archives/archives.php?day=28&month=11&year=2011&hour=12&map=0&mode=0

http://www.meteociel.fr/modeles/archives/archives.php?day=1&month=12&year=2011&hour=12&map=0&mode=0

http://www.meteociel.fr/modeles/archives/archives.php?day=4&month=12&year=2011&hour=12&map=0&mode=0

Gladly take what is shown now.

[Bobby]

People are talking about plenty of Northern Blocking, I can't see much sign of that on the ECM 00z mean

Day 10:

At least there's ensemble P2 to provide some fun in deep FI

Overall, putting everything together, my opinion is that this first attempt at a proper cold spell will now fail to deliver, with the Atlantic returning for a time. It was always looking dodgy with the consistent lack of ensemble support and swinging OP runs. There's certainly a possibility of another attempt later down the line but the only thing certain at the moment is that things are uncertain.

NAEFS lends supports the Atlantic making a move in around +168/+192

Edited November 26, 2012 by Barb-

[CI Weather]

I don't really post but have been watching the models for years and have seen enough near misses to realise how difficult it is to get really cold weather to the UK, as we have seen over the last 24-48 hrs small changes can have huge affects. One things for sure there will be more changes in the output, as per Steve Murr's excellent post if the low to the SW of Greenland does phase in our favor this may flip back if not we may be looking at another shot in a few weeks.

It's great to see Ian Ferguson giving an insight to the thoughts at MO. Any new comers just need to get to know the posters with the real knowledge and those that are waiting for a 'winters over' post or making ridiculous statements after a few frames of a run. A huge thanks to the more experienced posters over the years a lot of good posts and a lot to learn from them.

Certainly had much better winters over the last 4 years so maybe have been a little spoilt with cold prospects and blocking scenarios (even if last winter was poor still had 12cm snow fall IMBY in Feb)

I'm looking for the ECM to move towards UKMO if it doesn't and in the end get a disappointing cold zonal type that's just the weather and why we enjoy watching the model ouput and even those that don't still talk about the British weather!

Edited November 26, 2012 by CI Weather

[bluearmy]

To be perfectly honest with the folks looking for a lenghty severe cold spell (including myself :-) today's ECM/GFS 500mb height anomalies may just be starting to suggest a change in the upper air pattern, this is in regards to the GFS and ECM starting to show a short cold spell followed by LP breaking through the block, if you look at the GFS mean it does show a more Wsterly flow in 7-10 days time with lower heights filling the void between Northern UK and Southern Greenland, whilst the ECM mean is different to the GFS it would suggest that when these anamolies are at odds with each other a change in upper air pattern is likely, but it needs at least 3 days of continous agreement to suggest the change is likely to happen

Of course the upper air pattern may not change but there is a suggestion withing the 500mb mean that the GFS and ECM op's showing LP breaking through the block may well be right and we could be heading towards a "milder" few days after the cold spell before possibly the block re-builds again??????

I haven't looked at the NAEFS and the above drivel is just based on todays 500mb ECM / GFS anomalies :-)

at the risk of sounding like a stuck record, this may not be the best time to be using charts derived from operational data . this being one of those periods which supports my dislike of that particular tool.

[london-snow]

So basically reading between the lines we have three options? -

A -

A battleground where milder weather tries to push in from the west and colder air is established to our eastern half the two join together and we have a snowfall event on the eastern side and sleet to rain on the western side. Colder air to win out and re establish in a few days after while the east stays cold throughout.

B -

A battleground where milder weather tries to push in from the west and colder air is established to our eastern half the two join together and we have a snowfall event on the eastern side and sleet to rain on the western side. Milder air to win out on that occasion however this is just very temporary as a renewed push of cold establishes in the uk.

C -

That low out to the west is forced north and west and does not make any inroads east thus allowing the cold to spread further west and the Atlantic not firing up and keeping the uk in a cold spell throughout.

Is that a fair assessment of options on the table at present?

[UV-RAY]

Agree here, Nick.

Too many people are getting confused with a leakage of energy across the Atlantic with a return to zonal conditions. The block appears to be waxing and waning rather than diminishing completely. If you look at one run then this may show the wax, wane or even something more out of kilter. Looking at the anomaly composites that GP has posted they look the same as they did yesterday - so the background signals are not changing here.

One can see the fight in the GFS high resolution that the computing process has trying to work out how much energy to allow through against the background signal. When adding in the other models we see the struggle.

Good posts from Ian F, SM and GP who have all correctly identified this.

One question which puzzles me Chio and that is would there still be enough residual energy left to push through the block once it re-establishes itself at a later date.

[jimben]

So a cyclonic cold block looks the order of the day for December, pressure higher to the south of Greenland.

Is this a rex block? because these have produced some memorable winters in the past

[No Balls Like Snow Balls]

at the risk of sounding like a stuck record, this may not be the best time to be using charts derived from operational data . this being one of those periods which supports my dislike of that particular tool.

No worries, everyone is entitled to there own opinion :-)

[Methuselah]

No worries, everyone is entitled to there own opinion :-)

And, let us be honest with ourselves, all most of us are really doing - apart from Gibby & the likes - is cherry-picking charts in order to back-up our opinions? And there's nowt wrong with that!

[bluearmy]

No worries, everyone is entitled to there own opinion :-)

No slant on your post - you went on to explain the uncertainlty. i just used the occasion to illustrate why those particular charts are chocolate fireguard stuff when the fi ops are very unreliable.

[Catacol]

NAEFS ensemble data for T+180 shows clearly that heights are not going to be lowered behind this ejection of energy from Canada. The low may well punch through - though that is currently a long way from certain - and then heights swiftly build back behind. This is absolutely not zonal.

[No Balls Like Snow Balls]

And, let us be honest with ourselves, all most of us are really doing - apart from Gibby & the likes - is cherry-picking charts in order to back-up our opinions? And there's nowt wrong with that!

Yep, no-one really knows what is going on LOL

[No Balls Like Snow Balls]

No slant on your post - you went on to explain the uncertainlty. i just used the occasion to illustrate why those particular charts are chocolate fireguard stuff when the fi ops are very unreliable.

Yeah that's cool, I like to know what other people think, as to be honest i don't have a clue LOL

[karlos1983]

What time do the 12z roll out?