Model Output Discussion - The Run In To Christmas

[nick sussex]

Positively the short ensembles suggest that the spread narrows towards day ten so even if theres a delay they still bring in the cold.

 

Of course it might be nicer to get the low further se earlier, theres still a lot of support for the quicker route to cold.

 

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

[SMU]

Evening Festive weather goers...... :smiliz64: 

 

is it me or does it feel like we are really having to grind a cold spell out here, I mean santa give us a break.  For those south of the Scottish border Our Xmas wish list is just to see a bit of snow!!

Well its good news, now all models have generally converged on the original ECM solution then in the long term ( post 144-192 ) we may reap the benefits of a high that initially starts with the ridge over Eastern Canada drifting East as it comes under pressure from a deep low pressure moving north out of central canada

 

http://www.meteociel.fr/modeles/ecmwf/runs/2014122012/ECH1-168.GIF?20-0

 

You can see here the teleconnective pattern means the azores high has nowhere to go other than get moved out - this is because finally the jet is attenuated enough to be moving near due south out of the pole as opposed to move SE & sliding along the high.

 

The ECM mean at 168 is solidly in support for the OP which after being to progressive with the cold pattern have finally flipped to have a very short mild interlude before things rapidly get colder again.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2014122012/EDH1-168.GIF?20-0

 

In terms of differences the only real issue is the day 10 operational 500 Anomaly V the ensemble mean, the OP has a VERY stable high pressure south of Greenland that will just continue to feed to the polar air south, the ensembles are slightly less keen - however day 10 still sees the -5c line in the south of the UK>

 

So plenty to keep our eyes on, still the chance of the shortwave tracking further SE at 144 however heres the line up its only the GFS that's touting that solution now

 

ECM

http://www.meteociel.fr/modeles/ecmwf/runs/2014122012/ECH1-144.GIF?20-0 no snow for the UK

 

UKMO

http://www.meteociel.fr/modeles/ecmwf/runs/2014122012/ECM1-144.GIF?20-0

 

GEM

http://modeles.meteociel.fr/modeles/gem/runs/2014122012/gem-0-144.png?12

 

GFS

http://modeles.meteociel.fr/modeles/gfs/runs/2014122012/gfs-0-144.png?12

 

Expect the GFS to move north in line with the other models.

 

 

lets hope the next 48 consolidates the big push south of the cold & that it can be a little more sustainable.....

 

S

 

 

[Cloud 10]

Lots of confusing output over the last few days which is highlighted in the differences between the day 7 ECM and GEFS ensemble means.

 

ecm..  gefs..

 

 

 

 

[karlos1983]

Mean backs the op up for a change on the ECM. Shock horror

Edited December 20, 2014 by karlos1983

[Captain Shortwave]

Looking at the ensembles, the op looks on the progressive side with a milder spell sandwich between Christmas and the potential around days 9/10.

We have been saying that for 3 days now though. The northerly during week 2 has reasonable support. Some sort of wedge of heights in the northern Atlantic looks reasonable.

Edited December 20, 2014 by Captain shortwave

[fergieweather]

It's ironic seeing talk of EC backtracks/climbdowns etc etc. The clusters have remained pretty stark versus DET, and let's not lose sight that exactly 24hrs ago, yesterday's 12z DET, albeit with 15% ENS support, was running a wave across S'rn UK on Xmas Day, yielding circa 10cm snow on it's northern flank across southern England to give a truly white Xmas. And yet people here just berated it...!! Bizarre. Anyway, the very cyclonic look post-Xmas remains well set, despite uncertainty on temperature regime and amount of cold entrainment here in any such development. Clearly however, fair agreement on any snow threat further north, but confidence on the whole gig still low.

[on the coast]

It's ironic seeing talk of EC backtracks/climbdowns etc etc. The clusters have remained pretty stark versus DET, and let's not lose sight that exactly 24hrs ago, yesterday's 12z DET, albeit with 15% ENS support, was running a wave across S'rn UK on Xmas Day, yielding circa 10cm snow on it's northern flank across southern England to give a truly white Xmas. And yet people here just berated it...!! Bizarre. Anyway, the very cyclonic look post-Xmas remains well set, despite uncertainty on temperature regime and amount of cold entrainment here in any such development. Clearly however, fair agreement on any snow threat further north, but confidence on the whole gig still low.

 

The storm shown on GFS is a worry. Whats the Met take?

[karlos1983]

It's ironic seeing talk of EC backtracks/climbdowns etc etc. The clusters have remained pretty stark versus DET, and let's not lose sight that exactly 24hrs ago, yesterday's 12z DET, albeit with 15% ENS support, was running a wave across S'rn UK on Xmas Day, yielding circa 10cm snow on it's northern flank across southern England to give a truly white Xmas. And yet people here just berated it...!! Bizarre. Anyway, the very cyclonic look post-Xmas remains well set, despite uncertainty on temperature regime and amount of cold entrainment here in any such development. Clearly however, fair agreement on any snow threat further north, but confidence on the whole gig still low.

I must have missed that, I'd have happily walked that to the Bank! 10cm snow across Southern England on X-mas day.

[John Snow]

Showing my ignorance here but who or what is DET?

[SMU]

Extended ECM ENS

 

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php?run=12

 

I would hazard a guess the control holds the Greenland high pressure in situ out to 15 with perhaps a slight drift EAST.

 

S

[10 Days Away]

Extended ECM ENS

 

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php?run=12

 

I would hazard a guess the control holds the Greenland high pressure in situ out to 15 with perhaps a slight drift EAST.

 

S

 

 

The EPS wind direction compass seems to have the wind more likely from a W/SW/NW direction all the way through to the 29th  http://www.knmi.nl/exp/pluim/windroos.php

[Backtrack]

Showing my ignorance here but who or what is DET?

 

Operational run maybe? I honestly can't work out what that might mean either.

[03jtrickey]

Operational run maybe? I honestly can't work out what that might mean either.

Deterministic

[bluearmy]

Extended ECM ENS

 

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php?run=12

 

I would hazard a guess the control holds the Greenland high pressure in situ out to 15 with perhaps a slight drift EAST.

 

S

 

the control similar to the op but it maintains the extension to the azores low which then runs up just to the se of the uk day 9/10. thereafter, the high drifts east and slowly sinks across us but not before w shortwave drops in from the north se across the country (bringing inevitable snow event). the run actually ends with a large atlantic trough and euro ridge to our south and east. (the atlantic would probably go on to undercut a building scandi ridge)

 

there are clearly several clusters of ecm ens days 6 thru 10. thereafter, this run goes back to previous output with the euro low anomolys intensifying and this time encompassing the uk whilst the atlantic ridge holds to our nw. with a southerly jet, we then see an atlantic low anomoly coming in from the west to join the sceuro one. far too many options on the table there and need to see a few more runs before drawing any conclusions. could be snowmageddon or could be a mild souwester!! probably something inbetween which could get very interesting, given that we would probably have entrenched cold over nw europe.

Operational run maybe? I honestly can't work out what that might mean either.

 

correct

 

det = op

Edited December 20, 2014 by bluearmy

[Backtrack]

Deterministic

 

"In mathematics and physics, a deterministic system is a system in which no randomness is involved in the development of future states of the system."

 

I'm still no wiser as to what that might mean mate haha! Sorry!

[karlos1983]

Deterministic

Great now I have to get the dictionary out. Someone save me the effort.

Cheers backtrack I'm glad I didn't bother, none the wiser lol

Edited December 20, 2014 by karlos1983

[Mark Neal.]

"In mathematics and physics, a deterministic system is a system in which no randomness is involved in the development of future states of the system."

 

I'm still no wiser as to what that might mean mate haha! Sorry!

http://tornado.sfsu.edu/geosciences/classes/m698/Determinism/determinism.html - Find this interesting. 

 

Always known the OP to be DET, Deterministic.

[fergieweather]

Great now I have to get the dictionary out. Someone save me the effort.

Cheers backtrack I'm glad I didn't bother, none the wiser lol

Deterministic! As in the deterministic forecast!

[shaky]

Deterministic! As in the deterministic forecast!

fergie is there anything behind closed doors suggesting any widespread snow and is there still a chance of that snow event on Christmas day?

[BLAST FROM THE PAST]

I totally agree Caroline was fantastic and wiped the floor tonight, that showdance was incredible and really brave. If anyones wondering why I wasn't commenting on the ECM, even the models can't keep me from the best show on television! lol

 

Okay so having seen the ECM its an improvement and at least the direction of travel is positive, it does have a better looking block to the nw. Overall I'm a bit more optimistic tonight for colder prospects and so everyone will be spared one of my theatrical type tirades!

Just a name drop but nice one, Caroline is the sister of the wife of my wife's cousin....... and she's a nice woman too?  Try saying that after a few sherbs :smiliz19:

 

BFTP

[bluearmy]

                

 

 

naefs and ecm day 10 mean

 

something is wrong somewhere and likely its both !

 

 

btw, the ecm mean at day 8 is a fair representation of its day 10 from thursday though the ridge/trough to our sw and south now replaced with trough ridge as the influence of the operational trends are gradually absorbed by more members.

 

                       

 

the new mean perhaps more preferable in that it provides for the ridge to be cut off to our nw and could well feed up something interesting into the broad nw euro trough.

[03jtrickey]

Great now I have to get the dictionary out. Someone save me the effort.

From my understanding the deterministic forecast (i.e. operational run) calculates one particular outcome/forecast at high resolution based on one set of initial weather conditions (which are estimated based on observations).

However, the initial weather conditions can never be perfectly known due to incomplete geographic coverage of weather observation networks and uncertainty in measurements etc.

To account for this uncertainty, ensemble predictions are created by running the same model multiple times at a lower resolution using a range of slightly perturbed/adjusted (but still plausible) initial weather conditions as input data. Examining the range of different forecasts that result from the set of slightly different weather conditions gives an idea of the uncertainty in the forecast and allows the deterministic run to be considered in the context of these possible outcomes (e.g. mild outlier etc.). However the deterministic run is still valuable because its higher resolution resolves weather features better, particularly small scale features that may be critical for how a forecast develops.

[Mark Neal.]

Interesting to see what Mogreps is showing, What the UKMET think of model output at moment, so Ian Fergie snippets are brilliant for us model watchers.

GFS 18Z rolling...

Edited December 20, 2014 by Polar Maritime
To remove deleted quote.

[Essan]

Comments like this add nothing to the mode output discussion in here. Interesting to see what Mogreps is showing, What the UKMET think of model output at moment, so Ian Fergie snippets are brilliant for us model watchers.

 

GFS 18Z rolling...

 

Sometimes that is the only answer - especially when people can read prior comments and look at the model output themselves.

"is there anything behind closed doors suggesting any widespread snow and is there still a chance of that snow event on Christmas day?" 

No.  There is not.  What more can you say? 

[Midlands Ice Age]

My twopence worth....  (probably 10p worth today, but I don't charge!)  LOL

 

......

 

 

The net result is that the GFS has picked up the trend early but has failed to stick with it. It was too early to  ever have a chance. As Tamarra, Steve , TEITS and all us oldies have alluded to the atmospheric rubber band was not taut enough for it to go twang at that stage.

 

Tamarra has again indicated above the background signal is getting stronger. The longer we have to wait for the bang, the bigger will be the twang.!!

 

I still feel that the problem with the GFS is although it picked up the signals it was 2 days too progressive. 

 

So what happens next.....

 

I feel that we could end up with the original GFS blizzard, not coming down from the north, but from the Southwest.

 

IF has suggested massive cyclogenisis is likely with the proximity of the two massive air masses clashing.

 

The longer it takes for this to happen, I feel the deeper and more more exciting the weather will become.

 

If it is in the new year, I would expect a massive battleground over the UK, with the cold air setting in for quite a while after winning out. 

 

If it between Xmas and the new year all sorts of possibilities are possible from a total miss out on snow for the south, to a 3 day snowmaggedon,  followed by the Atlantic train. The final alternative would be  a blizzard in the north followed by mild for all. .

 

The current models are trying to get to grips with a fascinating situation. I hope we don't have to wait too long.

 

MIA

 

 

My posts from thursday and yesterday combined into one above and now being updated.

 

Looks like it is slowly evolving now.

 

The slower evolution looks like the correct option. To me this is getting really interesting now.

 

The rapid conversion to cold was always doomed to failure. The atmosphere was not fully primed

Give it a week from now and it is looking possible for an 'explosion'

 

It may take 2 weeks, if it does, it will be worth the wait.

 

How, why? I still feel a mlb somewhere around the UK will signal  that  the NH atmosphere is ready for being 'pricked'. This is exactly what happened in 62, from similar synoptics.

 

The ECM, MO,, GEM, JMA  are all signalling this block over the Xmas period.

It is at this point I feel the lows to the southwest will become important and these lows  will start to be driven south under the block, with a snow event for all and bingo we are stuck in cold from the N or NE  Europe.

 

During the next week (whilst we encounter warmer weather) Europe will cool down rapidly care of the lows moving down bypassing the UK . Eventually a Scandi will develop and we will be in the freezer for several weeks with a memorable (possibly record breaking)  cold spell.

 

Awaiting the 18Z with interest.

 

MIA