Model Output Discussion 4th Dec.2013-12z onwards.

[That ECM]

the charts below give what will probably be a pretty accurate idea of what the upper air pattern will be over the Christmas period, not mild most of the time, and not calm most of the time! http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Saw this earlier and didn't like what I saw. Mr Murr has posted twice in five days! Not looking good for a decent cold spell for awhile IMO. For those that enjoy strong winds and sideways rain, it does not get much better.

[bluearmy]

The extended ECM ens do push the trough into Europe, though on a nw/se axis. We are on the ' mean' colder side which will translate to some milder incursions and colder ones, though on the whole, probably the lower side of average. That will allow for some possible snowfall on the north side of features running w-e. the higher anomolys over s Europe and the eastern med, with the latter looking more convincing. cool to cold zonality the buzz phrase, once the trough has pushed in. If we can get under the trough, it is a good time of year with min solar input. Nothing tedious - now where's that three month Bartlett?

[lorenzo]

GFS relentless with the uber lows.. Continues firing the out on the 06z.

 

Wonder where the UKMO and ECM will see things this evening, another 'lively' week.

 

Mean Jet at day 10 from ECM

 

 

[SnowBallz]

Don't think I have seen such a wide range of option as after the 20 th the GFS at the moment does not know which way to go, ... a sign of possible major change? 

 

Hi,

 

With that thought, conceptually you're not far wrong.  A common misconception is often that variance implies that the data holds no discernible trend or pattern.  With stochastic mathematical modelling the opposite can often be the case as you are using parameterisation to resolve a lot of dynamic process.  Computing uses an inherently deterministic method of calculation, and will therefore follow certain patterns.  If you mix non-deterministic mathematical methods with that though, then you can produce patterning which infers a high degree of variance.

 

The underlying trend though, is that the variables which are calculated though stochastic parameterisation, are displaying that the 'end result' is not determined.  Okay, so why is that important?  Well, you can infer from it that the atmospheric state is non-determinable; the base variables are such that their propensity to change state, is statistically high.  To coin a phrase, the atmosphere looks finely balanced, and the stochastic elements of NWP is displaying this base state within the output.  Tighter grouping is often evident of a more settled atmospheric state, and a confidence in using the underlying laws of motion to hypothesise its change of state.

 

How 'major' a change is very - if not impossible - to judge.  A lot of atmospheric change is consequential of other variables; and variables that can amplify or suppress in equal measure.  Amplification is probably the hardest calculation to apply within NWP, as its consequences do bear disproportionate influence on the rest of the calculation process.  I think this is where the human eye is still the most discerning expert, when determining plausibility of NWP output.

 

Anyway I hope that helps?  It's a bit detailed, but in layman's terms I suppose the bottom line is that lots of variance or 'scatter' can - as you posed - reflect that a change is in the offing.  It doesn't by any means guarantee it, more that the underlying conditions seem far more conducive to it.

 

SB

[nick sussex]

The extended ECM ens do push the trough into Europe, though on a nw/se axis. We are on the ' mean' colder side which will translate to some milder incursions and colder ones, though on the whole, probably the lower side of average. That will allow for some possible snowfall on the north side of features running w-e. the higher anomolys over s Europe and the eastern med, with the latter looking more convincing. cool to cold zonality the buzz phrase, once the trough has pushed in. If we can get under the trough, it is a good time of year with min solar input. Nothing tedious - now where's that three month Bartlett?

You seem confident in that BA but I'm yet to be convinced especially after yet another ECM climbdown, yesterdays T240hrs which had some forcing on the pattern with that weak height rise over the pole and the east Pacific ridge  helping matters has bitten the dust!

 

The ECM seems to be just useless at the moment past T168hrs even allowing for the normal unreliability past that point it continues to perform poorly.Until I see that nw/se jet axis modelled within 168hrs then I'm going to be dubious.

[IDO]

You seem confident in that BA but I'm yet to be convinced especially after yet another ECM climbdown, yesterdays T240hrs which had some forcing on the pattern with that weak height rise over the pole and the east Pacific ridge  helping matters has bitten the dust!

 

The ECM seems to be just useless at the moment past T168hrs even allowing for the normal unreliability past that point it continues to perform poorly.Until I see that nw/se jet axis modelled within 168hrs then I'm going to be dubious.

 

 

Yes the Op is not the best guide at the moment but I believe BA was more instructive towards the Mean:

 

 

 

Certainly they do suggest a mean trough with a NW/SE jet axis, and somewhat less boring than a westerly jet.

[nick sussex]

Yes the Op is not the best guide at the moment but I believe BA was more instructive towards the Mean:

 

EDH101-240.gif  EDH1-240.gif

 

Certainly they do suggest a mean trough with a NW/SE jet axis, and somewhat less boring than a westerly jet.

Still not very good though, the troughing hasn't made enough inroads into Europe and the PV in one blob is not good. We need to see something like the T240hrs ECM of last night which lifted heights over the top half of Greenland , weak polar height rise and help from the ridge in the east Pacific, for newbies a bit more explanation in my post of last night no1789, page 90.

 

The far reaches of the GFS 06hrs  lower resolution highlight my point, I don't see any nw/se jet axis without help from the Pacific side and changes over Greenland.

Edited December 15, 2013 by nick sussex

[A.J]

Hi,

 

With that thought, conceptually you're not far wrong.  A common misconception is often that variance implies that the data holds no discernible trend or pattern.  With stochastic mathematical modelling the opposite can often be the case as you are using parameterisation to resolve a lot of dynamic process.  Computing uses an inherently deterministic method of calculation, and will therefore follow certain patterns.  If you mix non-deterministic mathematical methods with that though, then you can produce patterning which infers a high degree of variance.

 

The underlying trend though, is that the variables which are calculated though stochastic parameterisation, are displaying that the 'end result' is not determined.  Okay, so why is that important?  Well, you can infer from it that the atmospheric state is non-determinable; the base variables are such that their propensity to change state, is statistically high.  To coin a phrase, the atmosphere looks finely balanced, and the stochastic elements of NWP is displaying this base state within the output.  Tighter grouping is often evident of a more settled atmospheric state, and a confidence in using the underlying laws of motion to hypothesise its change of state.

 

How 'major' a change is very - if not impossible - to judge.  A lot of atmospheric change is consequential of other variables; and variables that can amplify or suppress in equal measure.  Amplification is probably the hardest calculation to apply within NWP, as its consequences do bear disproportionate influence on the rest of the calculation process.  I think this is where the human eye is still the most discerning expert, when determining plausibility of NWP output.

 

Anyway I hope that helps?  It's a bit detailed, but in layman's terms I suppose the bottom line is that lots of variance or 'scatter' can - as you posed - reflect that a change is in the offing.  It doesn't by any means guarantee it, more that the underlying conditions seem far more conducive to it.

 

SB

After I read the highlighted final paragraph I realised that this was an good post thus the 'like' but reading the previous paragraphs I had to ask myself 'Do you speak english?'....lol

 

Anyhoos, back to this morning's output, the 06z GFS continues the unsettled zonal theme for the bulk of the run with a seemingly endless train of deep lows battering the UK with plenty of rain and wind, with interspersed PM airflows giving numerous shower days, some wintry, especially (but not totally restricted) to northern parts of the UK

[Purga]

You seem confident in that BA but I'm yet to be convinced especially after yet another ECM climbdown, yesterdays T240hrs which had some forcing on the pattern with that weak height rise over the pole and the east Pacific ridge  helping matters has bitten the dust!

 

The ECM seems to be just useless at the moment past T168hrs even allowing for the normal unreliability past that point it continues to perform poorly.Until I see that nw/se jet axis modelled within 168hrs then I'm going to be dubious.

I agree Nick, although there is a vague hint of heights lowering over Europe in the very long term, the overall signal from the NWP main models is very much 'more of the same' i.e. supercharged zonality. Alternating mild and cooler interludes with a lot of unsettled & windy stuff is the form horse.

We're locked into this pattern for some weeks.

[IDO]

Still not very good though, the troughing hasn't made enough inroads into Europe and the PV in one blob is not good. We need to see something like the T240hrs ECM of last night which lifted heights over the top half of Greenland , weak polar height rise and help from the ridge in the east Pacific, for newbies a bit more explanation in my post of last night no1789, page 90.

 

The far reaches of the GFS 06hrs  lower resolution highlight my point, I don't see any nw/se jet axis without help from the Pacific side and changes over Greenland.

 

 

Yes , I agree. However at the moment we are look for small crumbs of comfort, I for one am not confident of any pattern change till the vortex has worn itself out sufficiently, probably mid January onwards, or we see some help from the Strat.

 

Pacific ridging looking less of a driver now, with current indications of a possible split vortex over Siberia as well as Greenland. The Pacific area will also be flattened by the strong jet on the Siberian side: 

Edited December 15, 2013 by i'm dreaming of...

[nick sussex]

I agree Nick, although there is a vague hint of heights lowering over Europe in the very long term, the overall signal from the NWP main models is very much 'more of the same' i.e. supercharged zonality. Alternating mild and cooler interludes with a lot of unsettled & windy stuff is the form horse.

We're locked into this pattern for some weeks.

In the very long term do you mean by the time I'm getting my pension or at the turn of the year! lol It's a dismal set up overall for any sort of decent cold, save for a few cold blips.

 

The troughing sinking is a first step especially if that gets to the east of the UK but we haven't even got close to that even verifying. We'll see over the next few days whether that can at least get within T168hrs.

[Rocheydub]

Purga, you may be misleading a few with the 'locked into this pattern for a few weeks' type of comment. It can, and will eventually change. But going for it lasting weeks is incorrect when FI is after 120/144. Just look at the scatter in the ensembles!

Meanwhile, lots of cross model agreement on Wed/Thurs storms. Looking nasty. Warnings out soon I reckon!

[EML Network]

It can't have escaped people's attention that XMas Eve, XMas Day, Boxing day right through until the turn of the year all have the potential to deliver damaging gusts of wind. not to mention this Wednesday and the coming weekend !!!

 

 

 

Here's what the ''highlights'' of what the 06z GFS has to offer up

 

XMAS EVE

Boxing Day

28th Dec

[Frosty.]

but reading the previous paragraphs I had to ask myself 'Do you speak english?'....lol

 

 

I learned 2 new words today...stochastic parameterisation..I feel clever now, hold on..what does it mean 

Edited December 15, 2013 by Frosty.

[Cloud 10]

I learned 2 new words today...stochastic parameterisation..I feel clever now, hold on..what does it mean 

 

 An important characteristic of weather and climate data is its pronounced variability with a continuous density spectrum over all scales of variability from the viscosity scale up to the Earth’s radius. The variability of the larger scales is reproduced by deterministic numerical weather prediction (NWP) and climate models. However, because of obvious computational and technological limitations, these models cannot resolve explicitly all scales of motions. We thus have to resort to parameterisations that describe the effect of unresolved scales as functions of resolved variables. Deterministic parametrisations make rigorous sense if we have a (wide) scale separation between resolved and unresolved processes. However, the continuous density spectrum precludes any meaningful scale separation. Over recent years, a new approach was introduced to help solve these problems: using stochastic mathematics to formulate the impact of processes at unresolved scales on the resolved scales of motion (stochastic parameterisations). Although it has been demonstrated that stochastic parameterisation schemes produce promising results and more skilful estimates of uncertainty, the development of rigorous stochastic formulations in weather and climate models is still very much at an early stage and the demand for more fundamental research in this area is large. A comprehensive, process oriented implementation of stochastic parameterisations in model systems is still a great challenge and requires widely interdisciplinary effort.

 

Stochastic Parameterisation in Weather and Climate Models — Meteorologisches Institut

 

 

Pretty straightforward really. 

[UV-RAY]

I learned 2 new words today...stochastic parameterisation..I feel clever now, hold on..what does it mean 

Lol, I'm nicking that one for the next time I play Scrabble.

Looking at the models and I don't see the same despondency as most others here, we have a jet which is looking likely to dive further and further South with time once any fronts push well into Europe. From there we could start too see tentative signs of height rises to our NW towards the months end, yes it's a glass half full viewpoint of the models but least we forget some were talking about a long fetch from the SW only a week ago and look how that prediction went.

[Purga]

Purga, you may be misleading a few with the 'locked into this pattern for a few weeks' type of comment. It can, and will eventually change. But going for it lasting weeks is incorrect when FI is after 120/144. Just look at the scatter in the ensembles!

Meanwhile, lots of cross model agreement on Wed/Thurs storms. Looking nasty. Warnings out soon I reckon!

There is some scatter in the ENS but not much! This shows me an architypical zonal pattern with oscillating unsettled mild / cool periods within which the different nuances of the individual members will of course vary. The overall zonal pattern remains solid right up to the end of the month.

 

I'm not saying it will not change in due course just commenting on what the models / ENS are showing right now and have done for several runs.

Edited December 15, 2013 by Purga

[Frosty.]

Lol, I'm nicking that one for the next time I play Scrabble.Looking at the models and I don't see the same despondency as most others here, we have a jet which is looking likely to dive further and further South with time once any fronts push well into Europe. From there we could start too see tentative signs of height rises to our NW towards the months end, yes it's a glass half full viewpoint of the models but least we forget some were talking about a long fetch from the SW only a week ago and look how that prediction went.

I agree SI, just thinking back to this time last week and the models were showing a benign, mild stagnant snooze fest with a mega limpet euro high..it looks more like winter now.

[Frosty.]

I like the end of the Gfs 06z op run, a few frames later it would be even more wintry and as for the run as a whole, no change to the general direction the models are taking, cold zonal mixed with less cold but the tendancy being towards cold zonal taking charge between christmas and new year with the jet being forced further and further south by deeper lowering heights swinging down from the northwest which will increase the risk of sleet and snow plus ice & frosts.

[Iceaxecrampon]

Ulster on Wednesday

 

 

And the rest of the UK for that matter.....

 

 

Southerlies for Christmas Eve? 

 

 

Christmas Day - 15% for Cumbria. 

 

 

 

Cant tap in to Frostys enthusiasm on these last runs at present for cold to be honest!

 

 

 

Ian

Edited December 15, 2013 by Iceaxecrampon

[cooling climate]

The extended ECM ens do push the trough into Europe, though on a nw/se axis. We are on the ' mean' colder side which will translate to some milder incursions and colder ones, though on the whole, probably the lower side of average. That will allow for some possible snowfall on the north side of features running w-e. the higher anomolys over s Europe and the eastern med, with the latter looking more convincing. cool to cold zonality the buzz phrase, once the trough has pushed in. If we can get under the trough, it is a good time of year with min solar input. Nothing tedious - now where's that three month Bartlett?

I made a post a couple of days back that this looked the way forward but only if the trough gets

to the east of the UK. The GFS has backed off of this but It is not unusual for the model to do

this and then pick it up again.

[Frosty.]

Ulster on Wednesday

 

ukwind.png

 

And the rest of the UK for that matter.....

 

h500slp.png

 

Southerlies for Christmas Eve? 

 

ukwind (1).png

 

Christmas Day - 15% for Cumbria. 

 

uksnowrisk.png

 

 

Cant tap in to Frostys enthusiasm on these last runs at present for cold to be honest!

 

 

 

Ian

It's the overall pattern I like most, there is good potential for cold incursions during the next few weeks which is a far cry from how desperately poor the models looked around a week ago with a seemingly all conquering euro high snuffing winter out for the next 4 weeks, things are on the up I think.

Edited December 15, 2013 by Frosty.

[nick sussex]

I like the end of the Gfs 06z op run, a few frames later it would be even more wintry and as for the run as a whole, no change to the general direction the models are taking, cold zonal mixed with less cold but the tendancy being towards cold zonal taking charge between christmas and new year with the jet being forced further and further south by deeper lowering heights swinging down from the northwest which will increase the risk of sleet and snow plus ice & frosts.

You need to get a job with the Tories they could do with someone like you Frosty to spin mediocre/bad news into something more positive! Do you have an aversion to uttering the word mild? The much vaunted cold zonal is a rarity in the truest sense, you certainly need some forcing on the pattern to head south and unless theres a pressure rise to the ne/n then its not going to happen.

 

I admire your optimism Frosty but I do think you've gone into spin overdrive here, the jet axis nw/se isn't even showing up in any more reliable timeframe, a couple of GFS lower resolutions at T360 are really not worth taking seriously.

 

The ECM which is fast becoming a major irritation for me throws out a more positive solution at T240hrs which never sees the light of day, overall its not the worst zonal set up I've seen as in at least there might be the odd cold blip and a little snow in the north but my sledge rating is flatlining at 1/10 and that's being charitable.

 

The jet doesn't just say hey lets head south it needs a trigger and that needs to come with a relaxation of those low heights to the north , something like last nights ECM T240hrs would be a start, show me that at T144hrs and I might be a bit more optimistic. We'll see over the coming days if theres any real progress to a southwards jet adjustment.

 

Keep up the good work though Frosty, if the power of positive thought could change this pattern you would have succeeded already!

 

PS I hope people don't think I'm being a miserable sod here, I'd love to see a change in this pattern but we're a long way from what many coldies would like to see especially for the Xmas period.

Edited December 15, 2013 by nick sussex

[radiohead]

Some wild looking output on the 06Z GEFS for the Christmas period, with some of the ensemble membrs trying to wipe us off the map.

 

[Purga]

OK some crumbs of comfort.

 

Here are the ENS for Rome showing the mean SLP edging down in time.

 

 

Same for Vienna.

 

 

Ditto Warsaw

 

 

 

Back to Vienna - being right in the centre of the continent (more or less) & the 850 hPa's show a more unsettled picture developing

 

 

So if the trend is correct and bear in mind that quite a few ENS members do not support it, then there could be some hope of at least the first steps towards getting a somewhat colder pattern.

Very tentative I must stress!

Edited December 15, 2013 by Purga