Model Output Discussion 5/12/2012 18Z onwards - the one after THAT ECM

[weather eater]

Going to score this run at 9.5 out of a possible 12, mainly because it falls away at the end, The crucial thing now is not the many permutations of the easterly that the models may evolve over the coming days, but getting the building blocks right pre the 120hrs mark.

[Thundery wintry showers]

I'm refusing to get too excited about the "easterly potential" just yet, because the critical point of the evolution happens between T+96 and T+144- there is still room for some movement at that sort of range and we could still see a tone-down to a relatively dry and cloudy type of south-easterly, of the sort that some runs were showing a couple of days ago. The UKMO T+144 output is rather different to the GFS and ECMWF and shows lows engaging the cold air from the SW, although it is rather out on its own with this and even that evolution could potentially be snowy, as we keep pretty strong blocking to the north and potential for battleground snowfalls.

Despite the above words of caution, there's no doubt that the model outputs have shifted strongly in favour of an east to north-easterly type setting in after T+96. Most of us would then be looking at a few days of sunshine and snow showers, perhaps a wintry mix near east-facing coastal fringes but cold enough for lying snow elsewhere, and only sheltered western parts largely missing out. In such airflows there is also the chance of organised snowfalls via troughs embedded in the airflow, and frontal systems pushing into southern areas associated with southerly tracking lows. If those outputs get to within T+72 then I might be tempted to start ramping in the north of England regional threads.

Before that, we have some serious precipitation coming up tomorrow and into Friday which may well aggravate the flooding problems. Parts of southern Scotland and the north and east of England may also get a marginal snow event out of this with some significant snowfall for a time in some areas, though it will generally turn to rain at low levels. The second depression at around T+96 won't generate much rain but it will almost certainly be followed by the arrival of continental air- what type of continental flow remains less than certain but as noted above the majority of model outputs are suggesting a snowy east to north-easterly type.

Edited December 5, 2012 by Thundery wintry showers

[Southern Storm]

You simply couldn't make it up.

Well that's it then, its got to happen now! Lol

[PolarWarsaw]

Although there isn't a record set for a certain time of day. I wonder if we'l see the highest 0z turn out in living memory?

[Rob K]

Going to score this run at 9.5 out of a possible 12, mainly because it falls away at the end, The crucial thing now is not the many permutations of the easterly that the models may evolve over the coming days, but getting the building blocks right pre the 120hrs mark.

I actually think the final stages of the run in FI are quite encouraging, despite the fine detail. The PV relocating to Siberia is what needs to happen to keep the cold going. Otherwise the cold pool just runs out from the east and we get a gradual grey mushy warm-up.

[Rocheydub]

whaeres is mr murr has h fainted

also if the easetly came how much snow could the east sussex get

You need to find the regional threads here fella!

[TEITS]

For the newer members if you haven't seen enough eye candy this evening you can also view the GEFS ensembles which are now coming out.

I have found viewing the models tonight more exciting than looking at the Daily sport.

[Fred Sykes]

Sorry I know this is off model topic, but someone asked what the BEAST looked like

[Hodgheg]

Been following the models since october, surely something must happen soon form these. Lets face it though, just these cold proper winter days are something we thought were a bit of a distant memory until the last 4 years or so.

[Buzzit]

Cookie monster on the left? Didn't he turn up in the models earlier this year? Maybe its him tampering with the models...and may he continue.

He Did

[kold weather]

Well the GFS is a superb run, but its clearly not quite in the same league as the 12z ECM, which was an exceptional run by any standards.

I'll take the GFS run, though there are certainly ways that it could turn our even better than forecasts (By the upper high holding around the Greenland/Iceland area for longer and not allowing atlantic LP's to work in.)

[Bishop Brennan]

18Z = party time!

Edited December 5, 2012 by Bishop Brennan

[snowking]

By the way, just taken a look at the extended ECM 12z control.....after the initial easterly it goes very similarly to FI of the GFS 18z, with an undercutting low deepening over the channel and heading north, effectively removing the block altogether by preventing the feed of WAA, and its timing with the PV lobe out of scandi increases this effect.

Looks out of sorts with the pattern with a very quick tendency to lower heights over Greenland, however with both the ECM Control and GFS Op suggesting this longer term solution within hours of eachother, I guess its something longer term we have to give a little attention to

Of course in between then and now theres a couple of wintry showers to contend with

SK

[weather eater]

I actually think the final stages of the run in FI are quite encouraging, despite the fine detail. The PV relocating to Siberia is what needs to happen to keep the cold going. Otherwise the cold pool just runs out from the east and we get a gradual grey mushy warm-up.

Yes that’s true enough but I’m just judging on the cold and snow potential for the UK within the time frame of the run, a bit unfair on the GFS as it goes further out than the ECM so has more time for a breakdown in UK conditions. If we take it to the ECMs 240hrs then 10.5 or 11 would be nearer the mark.

[bryan629]

ok so its going to get really ,really cold, a real beast from the east on its way...well almost set in stone anyway... what can we expect temperature wise and snowfall wise....im new and a novice and im sure there are loads of people looking in that want to know too... lol if anyone says rain ill die hahah !!

i know from model watching snow forcasting is quite difficult and requires specific synoptics like uppers of -2 to -5 on the 850hpa, but different blues from the east have me confused as to the potential showery effect or troughs for that matter if they evolve.

ive seen it takes sometines the lake effect to kick in and understand it may take wind speed and convection to harbour a decent deluge on the east coast as well as further in land , but my question is will this all happen or is the air too dry for it ?

[snowking]

And lets follow up that slightly downbeat one with a much more upbeat post:

The consistent ensemble mean tendency to transfer the lowest heights out of the continent and across the south of the UK bodes very well for fans of snow

SK

[TEITS]

Just want to bring your minds back to E,lys over recent years.

Dec 2005.

http://www.wetterzen...00120051227.gif

Feb 2009.

http://www.wetterzen...00120090202.gif

GEFS 18Z Mean.

http://modeles.meteo...21-1-168.png?18

Now those E,lys did actually deliver the goods for me but if you compare those charts to the GFS/GEFS/ECM you will agree our current projected E,lys are looking far tastier.

So basically without tempting fate but even with a downgrade the outlook is looking very promising and the 12Z ECM will be virtually impossible to improve upon.

Edited December 5, 2012 by THE EYE IN THE SKY

[Dampdorset82]

And lets follow up that slightly downbeat one with a much more upbeat post:

The consistent ensemble mean tendency to transfer the lowest heights out of the continent and across the south of the UK bodes very well for fans of snow

SK

Its the southern half of the UK that gets the snowiest weather from an easterly and Im fulling expecting a lot of snow in dorset over the coming weeks. But i think a lot of the UK will see snow from this.

[SupaSnowy]

Been looking at GFS, ECM etc for years and never had such great fun viewing them over the past few days. Look forward to tomorrow, Im still going to hold back as I have been let down more times then not. If GP is right then this could be just the start and only get better by mid January.

As many people say get the cold here first then the snow will come.(most times) haha.

I'm sure the UKMO will look better tomorrow. If only the ECM would come true but that's pretty extreme. I am so tempted to wait up for the 00z I'm sure many other people are to haha.

[snowking]

And just one more ensemble chart to re-assure us all a little more

The spread on that trigger shortwave is now restricted to an area which would be favourable no matter what (at least taking the 18z ensemble spreads at face value)

SK

[damianslaw]

Background upstream signals do support an easterly airstream next week, with the jet taking a southerly dive and the polar vortex holding strong over Canada.. so not surprised to see this evening GFS and ECM output, but the strength of the block over scandi shown by both models for the time of year is exceptionally strong, this is when easterlies and scandi highs are least likely to set up shop, most of our severe cold weather in Decembers such as 1995, 2009 and 2010 came courtesy of a greenland high rather than a scandi high - the models are showing synoptics much more likely in the second half of the winter when the atlantic is much quieter.

In the reliable timeframe its a cold unsettled outlook, further snow for the north tonight and tomorrow morning, followed by a cold showery day for many on Friday, then hopefully a decent dry day on Saturday away from NW with an early frost, before we see more rain/sleet from the north later saturday into Sunday for all. The key to how quickly we pull in the easterly is the low pressure due to move down the N Sea, the BBC showed the feature quickly moving down to the low countries which would pull in the easterly quite quickly come next Tuesday.

Lots going on - and the medium term prospects for the middle of the month look very conducive for severe cold and snowy episodes, and on a personal level the forecast for the PV to switch to Siberia in the run up to christmas would be ideal as it would prolong the cold enabling a greenland high to develop and a very unstable arctic northeasterly to flow - my favourite winter synoptic.

[TEITS]

I'm sure the UKMO will look better tomorrow. If only the ECM would come true but that's pretty extreme. I am so tempted to wait up for the 00z I'm sure many other people are to haha.

Funny you say that and apologies mods im going to be slightly off topic for once.

When I first joined this forum my passion was probably greater than it is now. If a cold spell was on the horizon I would struggle to sleep and would get up at 4am to view the models before returning to bed. Now I haven't done this for years and since the cold spells of 2009, 2010 the chase is kind of over for me. However for the first time in many years I must admit I think I will struggle to sleep tonight and may even get up early to view the models!

The significant aspect of todays outputs isn't how cold or how much snowfall but the westward extent of the E,lys across the Atlantic. This isn't a projected E,ly where we're only just on the edge of the colder E,ly flow. The models if anything have this block moving further W into the end of next week. At the moment any attack from the Atlantic looks likely to come from the S/SW which could only increase snowfalls.

[peterf]

sheep are coming in off the lower fell!

[suffolkboy_]

I know it's not really the place.....but I think it's time to drag this old favourite out again.....could we see it again?

[ITSY]

....and here's a snapshot of how some of those GM modifications shape-up in our operational forecast:

Easterly looks good then?!