Model Output Discussion - 26Th Dec 21:25-->

[abruzzi spur]

At the risk of this being another of my "what the 'eck is going on" posts, and taking account of the likelihood that this thread may at this time of year be fuelled by a little more of the old firewater than usual, I can only ask, what the 'eck is going on? Apart from all the regular experienced posters on here tonight we have also had a professional forecaster essentially suggesting (in my humble interpretation) that lots of contributors need, putting it as neutrally as possible, to calm down. Combined with that we have our mods having to issue warnings of suspensions until the new year for those more inflammatory posters. As someone who is trying to learn from this thread I can only endorse both these points of view.

So far, as the 18z rolls out, I have read numerous posts saying entirely contradictory things (the low is moving north, south, east, west and all points in between, the south will miss out, the north will be pasted, the midlands will miss out or be pasted et cetera and so on etc). May I make a suggestion to the mods - how about blocking any posts at all until the model has finished its run, so that the posted views of members might then be considered, analytical, informative and based on the full model run rather than a running commentary as the computers churn out their predictions?

If Rembrandt was being analysed on every brush stroke as he put together a picture, or Stevie Wonder every time he put a note in front (or behind or on top) of another, they might have become just a little fed up - "black strokes look a bit lighter on this draft, maybe the guards' hats will be more prominent?" and "I don't like the way that guitar riff is buidling on this version, might mean that it's just paranoia rather than superstition, which we had previouly assumed was nailed")

Anyway, happy Christmas (BTW it looks like the star of Bethlehem is further south on this run which might mean the wise men miss us altogether and end up somewhere near the Maldives)

AS

Edited December 26, 2009 by abruzzi spur

[Barb]

For the record... the GEM and ECM have the snow boundary further South.

[kev238]

I dont have a clue what it is going to happen next week. I am in Nottingham and so might be far enough North but then again possibly too far East to get snowfall with warmer temperatures etc spilling in from the North Sea. Then again, precipitation may not reach this far. Who knows. On the face of it, temperatures look to high on gfs tonight to support snow without altitude anyhow!

[swfc]

LOL. Nice post. Everything past 72hrs is FI at mo.

To be fair thats a good point.Also the last couple of runs have come very close to a great easterley.Huge block dropping into the north of europe.

[abruzzi spur]

How in the heavens is anyone reading this thread meant to make head or tail of this. I would advise to wait a little longer until where the low is actually situated becomes clearer!

I've just posted a general reply which I hope entirely supports this point of view!

Thanks for getting there earlier and in a more compact fashion than I have managed.

AS

[pottyprof]

How in the heavens is anyone reading this thread meant to make head or tail of this. I would advise to wait a little longer until where the low is actually situated becomes clearer!

Total agreement... That's something you don't see often on here..

Case of wait and see peeps.. Looks to me like a cliff hanger.. The details are far enough away to put a "wait and see" tag on it..

[swfc]

I don't know about anyone else but im literally willing that SW NE of Scotland at +126 to back S around our LP. Simple reason is an incredible E,ly beckons if it does!

Very close teits but just does not make it.the ridge from the south kind of breaks its balls.

[Lewis]

Valid point. Looking at the general trend of where it is going should be discussed, but analysing every single movement on every single run is going to lead to some members going into stress overload!

HaHa yep the second models back track or jump on board with a different trend it's rope and neck time.

I'm use to the models chopping and changing, for example the cold snap we just had it was chop and change all the way through, and we was still looking at T24-T48 etc as they was so much uncertainty, well not just that the models had some kind of an agreement in a reliable time frame, but one over did it or under cooked it at one stage with certain features, shortwaves etc.

We are still a good 4 days away, and the models are constantly showing a different evolution, some good some bad. But i cannot remember the last time we had such a cold snap, and within 24 hours of the current snap moving away we are looking at another period of cold possibly very cold weather, with snow. This is model watching at it's best!

A lot of member's just expect one model to show snow, and then they some how get it into their head it's going to happen, then the second it changes/downgrades they just flip, imho them sort of people should stick to the weather reports and ramping threads.

Rule number 1 when regards to model watching;

If it's an upgrade it must be too good to be true, if it's a downgrade it can only get better, that's the way i look it, stops my disappointment

Anyhow, 18z is another possible scenario, and this occurrence will continue until we hit reliable time frame.

Hope everyone had a good xmas

Lewis

[Barb]

The blocking is putting a valiant fight against the Atlantic on this run, looks like it might win too.

[TEITS]

I know GP disagreed with me last night suggesting the GH would be the dominant player rather than E,lys via a GH & SH link up. However I am 90% confident the chance of N/NE,lys via a GH isn't on the menu anymore. If we are to see a prolonged cold spell then its most likely to come from a monster E,ly. The only ptoblem at the moment is the block is too far N!

If we end up with S,lys instead of bitter E,lys then it will be the biggest kick in the teeth I have ever known since I started following the models. Thankfully at this timeframe there is room for improvment.

[Geordiesnow]

I think this run demonstrates why you want that low as far South as possible, if it further south, it will make any pressure rises into Europe and the med much more difficult.

Decent enough run IMO, at least it has not trended with the UKMO thankfully.

[swfc]

I know GP disagreed with me last night suggesting the GH would be the dominant player rather than E,lys via a GH & SH link up. However I am 90% confident the chance of N/NE,lys via a GH isn't on the menu anymore. If we are to see a prolonged cold spell then its most likely to come from a monster E,ly. The only ptoblem at the moment is the block is too far N!

If we end up with S,lys instead of bitter E,lys then it will be the biggest kick in the teeth I have ever known since I started following the models. Thankfully at this timeframe there is room for improvment.

It is getting closer run by run and looks to be the form horse.

[rbw]

Someone posted a comment on why the Met Office are suggesting snow from the M4 Northwards but it has disappeared. This is a very interesting point but could as far I can see just be hinted out by this run. The area north of the M4 will be subject to the easterly in the 18zn but it will be air from the near continent which I wouldn't have thought would now be cold enough any longer.

R

[Barb]

The Beast from the East returns with vengeance in FI after a hard fought battle with the Altantic.

[East Herts Snow]

I know GP disagreed with me last night suggesting the GH would be the dominant player rather than E,lys via a GH & SH link up. However I am 90% confident the chance of N/NE,lys via a GH isn't on the menu anymore. If we are to see a prolonged cold spell then its most likely to come from a monster E,ly. The only ptoblem at the moment is the block is too far N!

If we end up with S,lys instead of bitter E,lys then it will be the biggest kick in the teeth I have ever known since I started following the models. Thankfully at this timeframe there is room for improvment.

LOL, the monster easterly appears between +252 and +264!

Massive Scandi High...

Shame its deepest FI, oh well maybe a trend to watch for.

Edited December 26, 2009 by North Londoner

[Guest North Sea Snow Convection]

Watching the 18z, it just underlines once again that this is far from sorted out yet. The blocking is being underestimated and the mild push is being overstated. Tonights output. overall and beyond , has helped in regard in terms of deciphering the uncertanties. Tomorrow is another day - but we have another very big -AO pulse on the way and that means imo there is only one direction the modelling can go. Especially in terms of the latest info regarding the likely movements of the vortex. Prior to the initial vortex split before xmas the models initially put more energy into the Canadian sector then it was moved into the Siberian sector, once again this is being shown and once again there are good signs that the same shift is occuring. Bearing in mind Steve M's post of early today I think we can expect to see that start being reflected in the modelling

So I would expect to see the models upgrade the easterly push and make less of the spoiling Scandinavian/UK trough

Edited December 26, 2009 by North Sea Snow Convection

[swfc]

Amazing .We lose the greenland high which drops into scandinavia but know easterly.It then slips into central europe at 1050 mb.Oh well.

[john w]

Agree TEITS

I thought id ponder work updates and the meto are sticking well and truly to their guns. I note precip amounts and it is actually a concern and share throughts of kold a few posts back. Many rivers are high and some are actually out of banks at the moment due to snow melt...though hopefully will decline a little in the next couple of days before this rain arrives....if it does arrive as rain.

Really need a decent GH now to block the atlantic models showing similar heights.

All in all the x-mas gift models have been reduced on downgrades for 6 runs now. I dont beleive there is a data issue, but if this is seriously a problem tomorrow will be key on the 00z and Monday 06z output.

Regarding my post earlier on data I looked further in to this and it is actually reasonably interesting.

As the jet is so far south NAT tracks have been also disproportionately south. Westbound planes avoid the jet while eastbound planes seek it. Sometimes in time turns they will fly a longer route west (distance wise) to avoid a more northerly NAT track flying in to the jet...gojg slower and less economical.

With aviation tracking further south on NAT tracks it would be interesting to see whether this has affected reliability of any pressure reporting aloft over iceland and greenland.

[TEITS]

Unfortunately both ECM and GFS are now banging out a pretty similar tune at T+168hrs, so in the absence of reduced data due to the holiday period it's hard to put up a viable arguement at this stage why both should be so badly wrong.

I can think of two reasons.

1. The timeframe as +168 should never be assumed as being correct.

2. ECM ensembles do not really support the ECM operational as the OP is much milder than the mean.

[cold snap]

That dam Low to the South on the 18Z is a trouble maker.

It whats causing all the problems it even trys to get in a Southerly at one point

However this could still produce snow for some

Its the good.bad and ugly low.

[nick sussex]

All todays runs considered keith and in the absence of some different looking runs overnight I'll be very surprised if they do not downgrade their forecasts tomorrow, perhaps quite considerably so.

Unfortunately both ECM and GFS are now banging out a pretty similar tune at T+168hrs, so in the absence of reduced data due to the holiday period it's hard to put up a viable arguement at this stage why both should be so badly wrong.

Probably wise to wait until the morning before jumping to to many conclusions, but I'm not overly confident that this next cold spell won't be something of "blink and you'll miss it" event, at least for southern areas.

I think the pitfall of following the operational runs is assuming that they are both correct at 168hrs when the early differences with how they handle the shortwaves and main low mean that all output past 96hrs is unreliable. We cannot draw any conclusions from output other than the general pattern, modelling how far north the jet is going to be at 168hrs is difficult at the best of times, globally 100-200 miles is nothing but in the current pattern would make a huge difference.

The ecm ensembles together with the gefs ensembles do not paint anything than lots of uncertainty, i will stick to my previous thoughts we need to keep an eye on the detail much early in the timeframe, once we have model agreement upto 96hrs then we can move onto next seeing what the outputs might do.

[Guest North Sea Snow Convection]

I know GP disagreed with me last night suggesting the GH would be the dominant player rather than E,lys via a GH & SH link up. However I am 90% confident the chance of N/NE,lys via a GH isn't on the menu anymore. If we are to see a prolonged cold spell then its most likely to come from a monster E,ly. The only ptoblem at the moment is the block is too far N!

If we end up with S,lys instead of bitter E,lys then it will be the biggest kick in the teeth I have ever known since I started following the models. Thankfully at this timeframe there is room for improvment.

Nick S's psychic linking strikes again! In a different way, you have said exactly the same as me!

[Troubleatmill]

The Beast from the East north africa? returns with vengeance in FI after a hard fought battle with the Altantic.

[MP-R]

How in the heavens is anyone reading this thread meant to make head or tail of this. I would advise to wait a little longer until where the low is actually situated becomes clearer!

I am saying this as a newbie as half the time I completely misread models to find what I want out of them :lol:. However, someone not too long ago and I can't remember who it was said the key is to look for trends, not bicker over the exact or changing position of the low. We won't know until much nearer the time and even then surprises can be had.

Hope that backs your post enough chionomaniac.

Edited December 26, 2009 by Michael Prys-Roberts

[TEITS]

Watching the 18z, it just underlines once again that this is far from sorted out yet. The blocking is being underestimated and the mild push is being overstated.

Very much agree Tamara.

For me personally I just think the models are doing their usual thing. At first it was going to be N,lys via the GH and now we have a near miss E,ly. I bet in a few days something else might be on the menu and this could be the E,ly actually reaching us for the reasons you gave.

Im just going to keep an open mind and see what happens. However the overall trend is towards cold especially due to the strongly negative NAO/AO.