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

[Bristawl Si]

That's exactly what I don't want.

See GP's post on P21 - much more promising for our neck of the woods if any 'battleground' scenario occurs.

[Iceberg]

well after trawling through all the GFS ENS seperately between t180 and t240, its very apparent that the GFS has not a scooby as to what will happen at that point. A few generals though would be more likely cold to very cold (particularly given wind direction and temp inversions), High pressure persistent to the North, NE or NW. Low Pressures flirting with the south is a common theme, sometimes they make it across the country sometimes they dont.

Overall though i am happy just to get this general impression of trends from the models beyond T180.

[nick sussex]

That's exactly what I don't want.

How about a snow to snow event! Theres no certainty that any low pressure will get far enough ne to see a change over to rain.

If the block holds further west with lower heights in the Med and not just over Iberia then low pressure is more likely to cut ese into France.

[Weathizard]

I think if we look at this ens chart it shows us all we need to know

A definite split with regards to an Atlantic attack, the key thing for me here though is that there is more of a cluster around the colder option, the mild options aren't really in a cluster and are most varied in outcome. The mean stays at -2/3 throughout even FI which again I think is a real positive. Very happy with the charts this morning we just need the colder uppers but I have a feeling they will be significantly colder come the actual time it arrives (we hope) I noticed this with this weeks cold snap, at about 120 -10's weren't progged to be anywhere near that. However yesterday they got very close to the east coast and I think even skirted EA at one point. Emphasises the fact we shouldn't worry about the uppers just yet, get the block in and they will come!

[weecrunchie]

forgive me for being amatuerish but as a snow lover i am a bit concerned about the lack of -10 upper temps to go with the beast from the east. Iknow folks are saying dont worry but to me it looks like there is not enough embedded cold coming from the east.

Great start to winter though

[nick sussex]

As is the way with these types of set ups elation today can be met with disappointment tomorrow.

By this I mean if we see an Atlantic attack with frontal snow the favoured areas change frequently. It's incredibly difficult for the models to balance block versus Atlantic low until much nearer the time.

[EML Network]

One thing that's a bit worrying perhaps is an increasing trend for low pressure to the SW/S. NAEFS pressure anomalies 00z at +240

That low pressure anomaly to the South/South West looks a little too close for comfort for me, on some of the OP runs and ensembles too. Hopefully if there's low pressure to the south/SW it will slide underneath perhaps giving us big snow events and keep the cold easterlies going, we don't want too much influence of low pressure to the S/SW though or it could bring in rain and milder air from the Atlantic. Need that block nice and strong too.

Yes I think this is looking possible, running through the animations of all the various GFS 06z runs it's clear that the vast majority want to introduce Low pressure off the atlantic , I suspect the 06z ensembles are going to disappoint a lot of people with a quick rise in 850 uppers , but I'm not going to be too bothered about it as it's well into FI and subject to change, all the same you can't deny that the trend is there, the ECM thinks it as do the Met office as does the GFS.

EDIT * Wouldn't take much of a more Southerly track, or 'undercut' for that same chart to produce copious amounts of snowfall on it's northern edge , especially if it took a North Easterly route afterwards

Edited December 6, 2012 by EML Network

[Karl83]

See GP's post on P21 - much more promising for our neck of the woods if any 'battleground' scenario occurs.

Thanks Bristle Boy.

How about a snow to snow event! Theres no certainty that any low pressure will get far enough ne to see a change over to rain.

If the block holds further west with lower heights in the Med and not just over Iberia then low pressure is more likely to cut ese into France.

Snow to snow event! Yes please! I sure hope the block holds and we enter a snowy period. My bday is the 18th and I have had many birthdays where its snowed or there has been snow on the ground. I wonder if this year will be the same.

[Glacier Point]

Thing to note about both GEFS and ECM ensembles beyond day 10. The mean is in something of a no mans land. Both suites show a clustering heading back down in the extended range.

[Ian Brown]

As is the way with these types of set ups elation today can be met with disappointment tomorrow.

By this I mean if we see an Atlantic attack with frontal snow the favoured areas change frequently. It's incredibly difficult for the models to balance block versus Atlantic low until much nearer the time.

Yes, there is absolutely no point anyone getting hung up on this, the METO have to mention it in their updates because they see the possibilities of Atlantic attacks but don't forget that the models will always want to break down a blocked set-up quicker than is likely.

I think the sort of set-ups being progged in FI gave the West Country some huge snowfalls in the classic winters of years gone by. It is potentially more complex than a Scandi block being attacked from the SW because the HP belt could be aligned across towards Iceland. Anyway, I would be surprised to see an attack from the SW or S this side of T240.

[sebastiaan1973]

http://www.noodweercentrale.nl/nl/weer/weer-voor-professionals/stromingsfilm/nederland.html -> this might be usefull for you (part of the UK) across the NorthSea as well. It shows the direction of the wind in detail over a period of 48h.

[Iceberg]

. Anyway, I would be surprised to see an attack from the SW or S this side of T240.

I wouldnt be surprised, but i would be surprised to see a successful attack

[Thundery wintry showers]

My current feeling regarding the long-term outlook is as follows (based on current model outputs and teleconnection signals):

1. A cold continental airflow is highly likely to come off between around 10 and 16 December. There is still scope, in my opinion, for variation either side of the current model outputs regarding the specific direction of the flow from the eastern half of the compass, the 850hPa temperature and the amount of showery activity that we get over the North Sea (broadly speaking the lower the 850hPa temperatures, the colder and the more showery it will be) but continental air and below-average temperatures are looking highly probable.

2. As others have noted, there is a split between models favouring a transition to milder weather with lows attacking from the SW, vs. lows sliding eastwards to our south and keeping us locked in a cold east to south-easterly type, while highest pressure is likely to retrogress from Scandinavia to Greenland. My feeling is that we will maybe get two or three days of "sliders" before the milder air eventually pushes up from the SW as low pressure becomes slow-moving to the W for a time. but I will be surprised if mild weather establishes widely before the 19th December.

3. There is a very strong likelihood, in my view, of any transition to milder weather being temporary, as towards Christmas we are likely to have a strong belt of high pressure around Greenland and Iceland. The only "spoiler" I can foresee as a likely outcome is if low pressure remains slow-moving to the west of the UK leaving us in mild southerlies- otherwise chances are we will get a spell of northerlies. I am reminded of Christmas 1995, when we saw an attack from the SW bring mild weather around 21-23 December only for arctic northerlies to return on 24-25 December. Thus, although it's a long way out, I feel that the probabilities re. likely weather around and just before Christmas are strongly weighted in favour of cold bright weather, especially the further north you are.

The NOAA's 8-14 day outlook for 13-19 December clearly shows the tendency for high pressure over Scandinavia to become more focused on the Greenland/Iceland area.

Edited December 6, 2012 by Thundery wintry showers

[Methuselah]

And we are always under attack from warmer air anyway...It just depends on the unknowable: precisely when and from where said attack will come...

With that said, a succession of Channel lows would be nice!

[Timmytour]

If we do end up getting the milder stuff the GFS seems intent on introducing, it could be a nightmare for those areas in the south and west prone to flooding, as heavy rain and quickly melting snow compound the problems they have already been experiencing

Edited December 6, 2012 by Timmytour

[kold weather]

I think the idea of an attack from the SW does have some merit, but consider (especially the GFS) what the models tend to do later in the run is overplay the hand of low pressure cells. I suspect in truth we'll drag in SE airflow but the LP will NOT be strong enough to totally rid us of the surface cold, especially the further north you are and we'll see that rattle off to the east, as we saw in late December 2009 and usher in another cold shot around 240-288hrs time. That'll be my call for now.

[Walkinglad2013]

Where is the snow that was forecast for today

[bradymk]

I have noticed an uptick of ECM ensembles this morning- with the operational & control both signalling a quick return to milder weather from the SW.

http://www.knmi.nl/e...agse/index.html

In this evolution the UK could possibly stay colder for longer, however its not welcome news today, although by far from any certainties.

http://www.meteo24.fr/fr/home/meteo-france-et-europe/passion-meteo/ensemble-de-previsions.html?eps=london

Yes noticed that but London ECM ensembles show the control is colder for London than it was for De Bilt and the mean around the same as it has been the last few days. Like y ou said, the UK could possibly stay colder for longer and I think this is what we might see in this situation. London ensembles may become a better guide than de bilt.

Matthew

[legritter]

It took me TWO CUPS OF COFFEE and 3 fags too look at last nights modell runs so CHICKENS do have teeth .a brilliant set up today going by most modells and data .i give the easterly an 80%chance of materialising at the moment .but as is the complexity of these set ups i feel we will have to wait till sunday to get a real feel of what comes at us from the east and indeed the south ,but certainly very very interesting possibilitys .posters must including myself be prepared for some let downs with others getting the cream on what could be on offer .we still have relative warm seas so if the synoptics set up as some of the modells suggest it cold turn into [could ]a snowy affair .i shall be using GFS for trends ,ecm out to about 168 and met office fax ,and of course the technical guys on NET WEATHER . And reading between the lines on Met office info because they can easily in this game science i should say, get egg on their face as us posters arent realy scrutinised .so enjoy present output ,catch up after Tonights output .cheers

[stainesbloke]

I'm getting quite excited by the charts now It's pointless worrying about where will get snow or rain, the main thing is the trend to keep high pressure to our N-NE for the foreseeable future allowing ever colder uppers to move over the UK. The SW will always be at most risk from the Atlantic but that can (and has many times in the past) result in some great battle-ground scenarios. These situations are probably the hardest to predict in our country. Encouraging signs are that high pressure stays strong to our N right through to the end of the model runs, which to me indicates any possible Atlantic incursions will be short-lived. Only time will tell I guess!

[Rocheydub]

I love my dogs!

What?? It's about as 'on topic' as some of the stuff in here!?!?!?

[AWD]

GFS 06z Ensembles;

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres

Some very cold members in there along with some less cold members.

Control & Operational close to the mean throughout the most part however.

[Frosty.]

The latest GEFS 06z mean and Ecm 00z ens mean makes awesome viewing for coldies and with a trend towards low pressure coming into the cold mix with some potentially large snowfalls should low pressure engage with deep cold over the uk which becomes established throughout next week, max temps eventually staying sub zero with penetrating night frosts. Next week shows an Easterly flow digging in with snow showers forming over the north sea and then being driven inland on strengthening ENEly winds, the mean shows winds eventually backing more SEly but the airmass will remain very cold with more snow, sw england may have snow as fronts approach from the atlantic into the cold block. it's best for now if we concentrate on next week rather than worrying about the week after because the models are currently suggesting a slow breakdown beyond T+300 hours but I feel that once the cold pattern becomes entrenched next week, it will become very difficult to shift and any attempt could result in widespread disruptive snowfalls depending on the angle of any subsequent atlantic attack.

[Rob K]

GFS 06z Ensembles;

http://www.meteociel...1&ville=Londres

Some very cold members in there along with some less cold members.

Control & Operational close to the mean throughout the most part however.

Certainly more signs of milder stuff after midmonth than on the last run, but I suspect it would only be fairly temporary, The Aberdeen ensemble shows the cold air is not far to the north: http://www.wetterzentrale.de/pics/MT8_Aberdeen_ens.png

My feeling is still erring to an attack (possibly snowy) from the SW, a brief warm up and then retrogession to Greenland and the possibility of some properly cold air coming down from the NE rather than the modest cold from the east that we are likely to see next week.

[jessandjon]

Bbc weather just said temps next week are proberly going to take a plunge