Model output discussion - 1st December onwards

[January Snowstorm]

The ECM may not look a thing of beauty at 192 hrs but it ain't far off delivering a major freeze.

Frigid air moving ever closer as low pressure at last under cuts into central europe

[knocker]

Interesting GEFS anomalies this morning/

At T240 the vortex is at NE Canada and low pressure dominates the Atlantic with a trough over the UK so continuing wet and windy and temps a wee bit above average. At the same time the double whammy attack on the vortex from Alaska and Russia continues apace

By T360 no massive change to this scenario except the westerly regime is well established with the Russian HP weakening.

 

[knocker]

Regarding the ecm I assume 'undercut' was tongue in cheek as the negatively tilted upper trough swoops down into central Europe and brings tidings of snow and cold to the skiing fraternity. The ecm has been liking the scenario of a trough to the east for a while.

Edited December 27, 2015 by knocker

[SMU]

Morning All

significant mid term interest today as the theme of the overnights is to send more energy into Europe under the block - 

this teases the deep cold ever closer  ....

anyone thinking this was over may want to think again -

expect another chunk of the ECM ens to collapse today....

s

[tinybill]

well  looking at the gfs this  morning it don't bring  very good  news  for the flooded areas

dec.  29,30,31   rain

jan  4,5,6,7,8,    rain....../12 ...   snow  poss  for the  uk

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

[knocker]

24 minutes ago, THE CHOSEN ONE said:

Morning All

 

anyone thinking this was over may want to think again -

expect another chunk of the ECM ens to collapse today....

s

Would you care to elucidate on that because on it's own it's pretty meaningless. Thanks.

[IDO]

As Mucka has said that diving low is being played with by GFS and the op is a lot better with that regard on the 0z. On this run it gets carried on the jet and when it hits the block it disrupts going under the block providing a gateway for further LP systems:

Thats where the models will have problems, how much goes under, how strong is the energy block -v Atlantic? But to get that cold from the east this is at least the first step.

The control shows the other way, the LP system is split and no energy is able to go under the block at that crucial time:

Control:  By D11: 

ECM consumes that shortwave into the vortex lobe and we get a delayed attempt at an undercut as a later shortwave in the jet does the undercut: 

It is promising that the algorithms want to send energy below but we need to get under D4 before we can be more confident. Plenty of potential at D10 on the GEFS but lots of variation so anyones guess how this will evolve:

      

The MJO signal is now weakening with most models (COD after D7) and I believe that this relates to a WWB killing the easterly wave. Some members going colder on the GEFS^^^ out in FI but they will increase once the undercut is resolved favourably (or not if it isn't!). 

In the nearer term the storm looks like missing the UK according to ECM but a trailing front will bring more rain  for the NW on Wednesday:

The Met update still goes with the non-easterly in this morning's update (wet & windy westerly flow) with no mention of a colder conditions. As others have said we are in with a chance at a spell of colder weather either via an undercut easterly or the jet sinking with disruption of the lower heights over the UK as the block -v- Atlantic battles close by. Alternatively the Atlantic may send too much energy over the top and just push the block too far east for much help for the UK (cold wise). The latter according to the expert forecasters remains the short priced favourite. 

 

Edited December 27, 2015 by IDO

[nick sussex]

Oh dear what drama!

The ECM is close to delivering significant snow to parts of the UK with D-Day T168hrs as the trough disruption there will either have people dusting off the sledges or getting the umbrellas out.

The GFS isn't as good but does weaken the overblown low coming from the east but little trough disruption.

The UKMO has a poorly orientated high but at T144hrs that might still go onto develop some undercutting.

In these situations you want the high aligned more ne/sw and facing the incoming trough.

Very difficult call from this far out, anything could happen.

[SMU]

14 minutes ago, knocker said:

Would you care to elucidate on that because on it's own it's pretty meaningless. Thanks.

The T2m for debilt were about 20% in support yesterday & the day 10 mean was this

00Z 

Then 12z

i expect there to be a significant increase  of support ( hence a collapse of the T2m) up to 40-50%

s

[KyleHenry]

4 minutes ago, nick sussex said:

Oh dear what drama!

The ECM is close to delivering significant snow to parts of the UK with D-Day T168hrs as the trough disruption there will either have people dusting off the sledges or getting the umbrellas out.

The GFS isn't as good but does weaken the overblown low coming from the east but little trough disruption.

The UKMO has a poorly orientated high but at T144hrs that might still go onto develop some undercutting.

In these situations you want the high aligned more ne/sw and facing the incoming trough.

Very difficult call from this far out, anything could happen.

Complex and fascinating.

European WAA up first, allows us to see how high a latitude the ridging can get and how strong  HP system can become.

Euro WAA requires the assistance from US West coast WAA to become more established. 

Too much ridging over an extended period from US WAA hampers latitude of where Scandinavian/Kara ridge establishes by not allowing Trop vortex to move back towards Northern Canada. 

It is great model viewing. 

 

 

 

 

[tinybill]

11 minutes ago, *Sub*Zero* said:

11 minutes ago, *Sub*Zero* said:

Sledges for some up north and a dusting further south, 2m temp charts showing widespread sub zero temps   

Sledges for some up north and a dusting further south, 2m temp charts showing widespread sub zero temps   

love to see it!!!! just for one day  but i think all eyes will   see  what coming next!!!  possible  more heavy rain and problems!!!

Edited December 27, 2015 by tinybill
bad spelling

[SMU]

The ECM control for reading has maxima of 0c at day 9 this morning ...

increaslng momentum for a westerly push of the colder air-

s

[Captain Shortwave]

ECMs ens

 

GEFs

 

So lets get the easier bits out of the way. After the initial battle ground the 7-10 day rages suggest the heights over Scandinavia will move away towards northern Russia with a poleward ridge through Svalbard. Now this leaves the door open for the Atlantic to move in, likely on a NWN/ESE axis through the UK and into Europe. Given the evolution we should expect systems to be rather slow moving and elongated whilst sliding underneath the block to our north/north east.

Now the complicated bit, we will have a deep cold pool over Eastern Europe, the models are struggling on a consist point even at 5/6 days out (ECM/GFS/UKMO and GEM give different solutions). Now these deep low heights will likely engage the low heights moving ESE from the Atlantic. Now this will potentially mean that cold air could move westwards along the northern flank of these elongated systems.

Something like this...

This is very high risk/high reward here, if we could slide low pressure through the Channel keeping all of the UK on the cold side we could see a widespread dumping of snow as very cold air over Eastern Europe and eventually Scandinavia piles westwards through the UK. The risk of course comes from the potential for low pressure to be too far north, unfortunately again the risk of major flooding with prolonged spells of heavy rain (AKA Jan 14).

There is potential and at the moment the things written above (even the more certain aspects of this evolution) could change. I wouldn't like to call it at the moment, far too many complex features in the mix, the first being that eastern European cold pool, the second being the initial battleground between the Scandi high and the deep low heights to our north west which could yield a better position if modelled differently over the coming runs.

Worth noting one last thing, the coldest members of the GFS suite tend to have a little extra help, either from a stronger Scandi high or have a little Atlantic amplification or better still a weak high forming between Iceland and Greenland.

The better day 10 perturbations (used for examples and not to be taken seriously).

 

Edited December 27, 2015 by Captain Shortwave

[nick sussex]

Comparing yesterday mornings ECM 00hrs with todays the noticeable thing is the increase in strength of the Russian high and the more negatively tilted Atlantic troughing.

The key timeframe is around T168hrs as its at this point that the solutions will likely diverge between favourable trough disruption or too much energy going over the top.

So for comparison yesterdays ECM 00hrs at T192hrs:

Todays to T168hrs:

Its clear when you look at the ECM postage stamps that theres still quite a lot of variation in terms of orientation of Russian high and how much energy is spilling over the top.

At T120hrs I can count at least 15 members that are past the point of no return in terms of developing favourably for the UK so if the ECM operational is correct at T120hrs then those ensembles are likely to shift across.

Do we trust the ECM operational run at T120hrs?

[A.J]

2 minutes ago, REDWARNING said:

Why post a chart at 192 that will never come off I'm going  to save that chart and see how close it is on that day to the chart .i make that  8 days time today is the 27/12/15 so that means that chart is for  January 4 2016.

ok....1) why post a chart?....because it's the model discussion thread, that's why, 2) charts at T192 and post T192 are important for potting possible trends and evolutions.....not all evolutions will verify, naturally, but how on earth is the science of weather forecasting ever going to improve if meteorologists ignore all model output post T192??

[kev238]

Great to see some more interesting charts emerging if you like colder potentially snowy weather.

I don't see a 1987 style freeze up but potential is there for low pressures to move on a southerly track with snow on the northern and Eastern flanks 

 

This change , or potential change ,  might be good news for flood affected areas as the focus of rainfall and the exceptional Synoptics that have created it may alter - though not to a dry scenario 

 

[Cloud 10]

Nice to see a couple of the op runs actually deliver the cold pool into the UK from the East.

 

No doubt plenty more drama to come though.

 

 

 

[bobbydog]

9 hours ago, DAVID SNOW said:

 

So you are saying the strat animal is easier to predict than the weather down here?

Good luck with that one

no i'm not. the professionals are.

(and not bodie & doyle)...

[nick sussex]

The ECM De Bilt ensembles have the operational and control runs as the equal coldest solutions on days 9 and 10, theres more support for an easterly flow there on days 11 and 12.

The divergence point is around T168hrs. The wind directions clearly show whats going on, the main cluster  directions sw to nw push the trough further east with more energy going over the top.

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

[northwestsnow]

15 minutes ago, nick sussex said:

The ECM De Bilt ensembles have the operational and control runs as the equal coldest solutions on days 9 and 10, theres more support for an easterly flow there on days 11 and 12.

The divergence point is around T168hrs. The wind directions clearly show whats going on, the main cluster  directions sw to nw push the trough further east with more energy going over the top.

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

Yes if the ens are going to 'flip' and follow the higher res op&control i would imagine later today or the 00z runs tomorrow will be the cut off. Thats assuming of course the op&control look similar this evening/tomorow.

It would be marvellous to see some wintry weather after the vile Nov/Dec.

[cold snap]

37 minutes ago, nick sussex said:

Comparing yesterday mornings ECM 00hrs with todays the noticeable thing is the increase in strength of the Russian high and the more negatively tilted Atlantic troughing.

The key timeframe is around T168hrs as its at this point that the solutions will likely diverge between favourable trough disruption or too much energy going over the top.

So for comparison yesterdays ECM 00hrs at T192hrs:

Todays to T168hrs:

Its clear when you look at the ECM postage stamps that theres still quite a lot of variation in terms of orientation of Russian high and how much energy is spilling over the top.

At T120hrs I can count at least 15 members that are past the point of no return in terms of developing favourably for the UK so if the ECM operational is correct at T120hrs then those ensembles are likely to shift across.

Do we trust the ECM operational run at T120hrs?

Fergie always says to take a close look at them stamps and there very anti east winds ,

in a nutshell need to see mega support across the suites .

Atlantic still seaming a little to strong at present ,need the Ens to show more support and maybe they will eventually 

Would expect a Scandi High now to verify 

 

 

Edited December 27, 2015 by cold snap

[snowking]

Well I've generally stayed on the sidelines of this period of interest as to be honest, right from the get-go, it had a huge sense of Deja-Vu about it from a number of previous episodes - and what all of those previous episodes have taught the more seasoned members on here over the years is there is little to gain from fretting over inter-operational run nuances behind days 4-5 (sometimes even sooner than that!) given the very delicate energy balances we are dealing with here as the jet stream interacts with our impressive block to the North-East. As has already been said on here, it's all about how much energy goes North over the top of the block trying to 'sink' it and how much goes South trying to 're-enforce' it.

The first thing to say on this is in such situations I would almost always favour the higher-resolution operational and control runs over the ensemble suites, particularly if the two are in agreement with one another. Now this isn't to say that because at T+168 the op and control runs are in alignment means that the solution shown is definitely what will come to transpire at T+0 - I would argue, rather unscientifically, that the higher resolution runs are often guilty of over-complicating, underestimating or over-strengthening certain features in the medium range and this is why we run ensemble suites, to counter this potential. So we should not be totally ignoring ensemble suites, it's just that the higher resolution of the operational runs may prove more useful here from past experience.

Where do I think this is heading? Well in previous episodes you need an awful lot of luck with some perfect alignment of flows to get the very coldest air to our shores. It's by no means impossible to achieve this but generally speaking the form horse given the projected positioning and alignment of the block across the more reliable suites is for much of the coldest air to remain tantalisingly close to our East with just a little spreading its way across the North Sea - a la February 2012 (I'm not saying that synoptically it's identical, but it gives you an idea of my expectations for the upcoming spell).

 

But whilst we all follow the ups and downs of the model rollercoaster in the shorter term, and as Tony pointed out last night, the interest should be more in the longer term given the assault we are about to undertake on the vortex. No matter which angle you look at it from precursor patterns, tropospheric attacks or even stratospheric attacks, we look to be in a very strong position heading in to January to try to topple the beast:

I've seen far worse looking setups than this:

All in all, this is the most positive I've been feeling about this season so far, but I would potentially look to temper expectations in the shorter term given the high complexity of the setup.

SK

 

 

Edited December 27, 2015 by snowking

[knocker]

Looking at the ext ecm anomalies following on from the chart at T240.

Two days later we have the negatively tilted trough running SE from the vortex to just west of the UK with another trough Denmark SE down to SE Europe. A general WSW flow with temps a little below average.

By T360 the Atlantic trough is more neutrally orientated to the west and the trough to the east has gone with HP attempting to push up from the SW of the UK. Thus the flow still around the W/SW quadrant with temps around average. This is around the time when the EC32 had a week of influence from the southern HP. Await with interest/

Edited December 27, 2015 by knocker

[shaky]

O6z same as gfs 00z so far!!low coming in from south west lets see if it can undercut!!still a pretty strong scandi high at 1045 mb!!

[Carlrg]

Come to daddy.

 

Come on you can do it kid!

 

 

Babies first steps, Lovely.

 

 

Now don't go running off, stay where we can see you!

 

 

 

Go and get your big brother, see if he wants to play!

 

Edited December 27, 2015 by Carlrg