Model Output Discussion - 8th December Onwards

[SMU]

http://www.meteociel.fr/ukmo/runs/2012120912/UN144-21.GIF?09-17

Not so bad broadly speaking with that epic russian high!

S

[OldMetMan]

Very informative post as per usual. Thanks. Here's how the senario above was looking some 6 days or so prior:

Thank you Snowmad. Yes, exactly, it is such a good example of how this battle can happen. It's been a while since anything similar happened.

[Captain Shortwave]

Am i the only that cant see a cold potential from the 12z run? I see a deep area of low pressure that will be bringing in wet and windy weather and a serious issue for flooded areas? Im talking about a reliable and semi reliable time frame here.

It's the trend of where that low is positioned which is key. It has moved progressively south with each run, unfortunately we are still in a south west airstream with the airflow coming from further south hence why we have higher upper temperatures. The thing is it would not take too much for us to have south easterly winds which would be much colder.

The positivity is still there but it's still very tentative.

[Snowman.]

Indeed, to see this at T+144 is pretty unusual

Only minor tweaks here or there would send our temperatures plummeting. This run, as per at the moment, could go either way. Either mild or v cold. take your pick, mine is with the cold scenario, as heights look to gather momentum to the East of Greenland, the easterlies spread back in across northern europe and the low is a bit further south.

EDIT: Very close to where we want to be at 156.

Looks like their is some very weak ridging into Greenland from Scandy/Norway it might be too weak yet.

[karyo]

Yup unfortunately the shape of the low pressure is not good. Still we all know what the gfs is like at showing huge lows that they then shy away from. Hopefully itl be better shaped and not as strong over coming runs.

Yes and unfortunately the UKMO has also taken a turn for the worse in it's 12z output. Breakdown snow is now looking unlikely apart from the north and the Atlantic low has too much energy to be stopped.

Karyo

[SnowBorder]

UKMO is not a great chart if you are looking for cold. However, I used to think the UKMO was consistent in its delivery, now i think it can be a little slow on the uptake / stubborn with its performance. As we know, the GfS is great for picking up trends before dropping them, and then presenting a diluted version of its original trend later down the line. I feel the ECM will back the GFS more than the UKMO today, and expect the UKMO to come on board by Tuesday.

[ITSY]

LP developing over Southern Europe.

I won't post anymore charts, I think they annoy the MODs, but the idea is to show that it is not all doom and gloom. We are very close in the above set-up to the Beasterly scenario

[swfc]

Just for a laugh look at the shortwave developing at 168hrs just to southern tip of scan,hahaha

[Dampdorset82]

It's the trend of where that low is positioned which is key, it has move prgressively south with each run, unfortunately we are still in a south west airstream with the airflow coming from further south hence why we have higher upper temperatures. The thing is it would not take too much for us to have south easterly winds which would be much colder.

The positivity is still there but it's still very tentative.

I agree it wouldnt take much, but there is alot of talk of potential but potential doesnt mean anything at the moment. Im not excited by this specific run in the reliable time frame 0hrs - 144hrs. I can see heights building round us again but they can POTENTIALY back off again and disapoint many. Im interested in the evolution alot.

[BARRY]

Don't think this run is anywhere near the potential out come it's just to progressive.

[Frosty.]

UKM final nail on coffin. We had a slight bit of hope this morning. It is now gone.

L O L

why not wait for the ecm, and your location is the final outpost of the frontier for cold anyway isn't it?

[Ian Brown]

12z clearly much more progressive and in line with the MetO updates - turning milder and SWerly from Friday. Whilst there are small corrections early on that go the way they need to if cold were to prolong, the overall pattern is much less cold on this compared to previous runs - especially the 6z where cold air was not far away. Here the above 0 uppers are chunky and dominant. It will be hard for a cold spell to develop if that fat Atlantic low doesnt do something different.

The Atlantic Lows can surely only decline in situ, the overall picture is interesting at T168 with the block out East.

[Iceberg]

Uk met 144 would be a bad chart if you had the nose of high pressure into western Norway that gfs has, the low would then head se. Gfs looks to be sending energy under the book again at t168 so all in all not too long before the cold can get back.

Again gfs keeps the cold uppers just over the North Sea.

[Snowly does it]

The Atlantic Lows can surely only decline in situ, the overall picture is interesting at T168 with the block out East.

Yeah it is looking interesting at 168, I think the Atlantic attack will certainly push through the UK initially. Heights at 168 are condusive to a cold spell but it will need a friendly catalyst. The pattern that is developing doesnt scream mild zonal at the moment, but its one of those where it could go that way. meh, tricky

[Panayiotis]

http://cdn.nwstatic....189/h500slp.png Low to the east of the USA is showing up again as it was on the 06z, can it do a better job and ridge the high into Greenland?

Edit: At 216hrs it seems so!

[swfc]

Fi one for me is at 120- hrs.The rest is up in the air.And right on cue at 240hrs here comes the easterly

[Frosty.]

maybe we will have residual surface cold even when the uppers (T850's rise)

[ITSY]

you know what, scrap my earlier comment, cos this either vindicates what I said or simply insults our intelligence!

[LomondSnowstorm]

People have spoken of this being a zonal pattern setting up, but in reality we merely have a stationary trough in the wrong position, at least on current runs:

There's no sign of the polar vortex returning to Greenland, so this is very likely to weaken and bring in a more favourable pattern for us at some point. There's certainly nothing zonal about this:

It looks to me like only a matter of time before we get another shot at a cold spell, though the details of the breakdown itself and exactly how this will play out is very much up in the air.

[Panayiotis]

Easterly anyone? Fi though!

http://cdn.nwstatic....276/h500slp.png

Edit:Argghh This time we have high pressure coming in from the west and all cold is diverted south and completely misses us! No worries as said its FI.

[Frosty.]

you know what, scrap my earlier comment, cos this either vindicates what I said or simply insults our intelligence!

ooooooo nice, round 2

[Snowly does it]

well it gets there by day 11 after a week of Atlantic attack. Lots of cherry bites required it seems.

4 days of cold weather, a week of average westerlies occasionally milder than average then Siberian HP to the rescue for Christmas? We'll see

[Snowman.]

The run was starting to look good then it loses it at the end a bit as it topples at least the signals are their.

ECM ensembles & GFS one's too up next.

[Gavin Hannah]

Fi one for me is at 120- hrs.The rest is up in the air.And right on cue at 240hrs here comes the easterly

Quite so, the key is whether or not the LP spits out a Channel dartboard which undercuts, or whether it stalls and flattens out. Sooooooo tense!!!

[ITSY]

FI land is cuckoo as we all (should) know, and the GFS delivers a signature hurricane again to blow the HP into oblivion (which won't happen given it's size and strength), but the pattern remains conducive to a reload down the line and before crimbo. We will have to wait another week to see how it develops but the potential remains. The search for trends like this should turn our attention to the ENS.