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Paul

Model Output Discussion - 8th December Onwards

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Ok, a fresh thread, a fresh start maybe?!

I think it's probably reasonable to set some expectations at this point - the model thread in winter is often a 'hunt for cold', it's popular, many enjoy it and that's great - it's a community and it's entirely reasonable that the threads are used by the community in the way they enjoy.

That said some are frustrated by it which is also entirely reasonable - each to their own, and this is why we offer alternatives - I'd strongly encourage those who find themselves stressed out by the model thread to use them rather than coming in here, getting annoyed and feeling alienated from the community. Like minded people will quickly gravitate toward the other threads as more and more people use them.

In terms of model discussion we currently have (but are always open to suggestion in terms of other options):

The main discussion thread (this one) - fast moving, sometimes a bit of a rollercoaster, with a slant toward cold in winter, and views from a wide range of people with differing interests, biases and levels of knowledge.

Model thoughts and summaries - slower moving, more straight down the line type model assessments and information:

http://forum.netweat...7th-nov-onward/

Technical discussion - for the more high end technical discussion surrounding the models and the various other factors around the output.

http://forum.netweat...del-discussion/

Model mayhem - all the emotion from looking at the models, rants, ramps etc

http://forum.netweat...n-ramp-go-nuts/

As a team all we can do is try to keep the threads on topic, and friendly. As members of the community though, we all have a responsibility for our own posts - ie to make sure they're polite, respectful and reasonable, and also to make sure they're in the right topic. Please don't just post whatever you like, wherever you like and expect the team to clean up after you.

Anyway, enough from me - please continue the discussion here, and just remember the community is what we all make of it smile.png

Paul

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Against the background signals and expected upper air patterns, that ecm fi makes much more sense. We've seen trough disruption in some low res gfs runs aswell so i supect it will be full steam ahead for round 3 of the winter 12/13 ramp in a few days!! Starting to see signs of model stress syndrome and a few of you seem to have lost faith. Its only dec 7th!!

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I think the ECM is more in line with what I would expect to see tonight - MJO phase 2 for December.

post-4523-0-09512100-1354996345_thumb.gi

As I have suggested in the strat thread, I am expecting heights to rise to our NW after the polar vortex has relocated to Siberia.

In the meantime, once the cold air retreats we will have a stubborn trough residing over the UK with all the attendent flood risks. Note that yet again, even with the pattern change, the heights over Greenland could still be described as above average - a slight positive anomaly that will materialise as a reduced vortex.

post-4523-0-70699900-1354996606_thumb.gi

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I couldnt resist it - I'm pouring back over today's posts.

I'm not sure about this one. I dont subscribe to the idea that a shortwave prevented the high from extending further west and therefore has let the atlantic in. To my eye (and I keep saying "assuming it happens") we have a great deal of energy that has almost appeared from nowhere, and the longwave pattern has adjusted to place the high much further to our east. Remember that the teleconnections were pointing to a retrogression of the pattern... but instead at the moment this does not appear to be what is modelled.

Short waves cause short range disruption... I dont think they drive the hemispheric pattern.

CH

As I said to John earlier (though in a slightly different context) you can look at this either way. I would put it to you from the point of view that the shortwave prevents the HP's from linking to our north (at least on current modelling) - without this link up, the Scandi/Siberian HP isn't pulled further west, and so is (potentially) blasted away by an atlantic LP

It is equally true that you could say that the HP's themselves were the determining factor...but I tend to look at it from the point of view of the longwave pattern dominates, and shortwave interferences alter this pattern.

I think either point of view is equally correct - they are not mutually exclusive

SK

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The 00z's were generally a big disappointment from a longer term wintry perspective but there are some signs emerging that the transition to milder later next week could become more complex with hints of undercut meaning winds more SEly ahead of the low moving in, so a spell of snow is more likely further north, maybe disruptive snow for scotland after midweek but mainly rain further south apart from the hills of wales, the midlands and northern england, the cold uppers may be reluctant to leave more northern parts of britain during the complex second half of the week, the first half looks more straightforward with a few wintry showers to n/e coasts but mainly sunny and cold inland with light winds but frosty nights. The further outlook, on balance, looks like becoming milder and more unsettled/windy at times, mainly swly to wly.

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Good evening. Here is the latest review from my perspective of the 12z output from GFS, UKMO and ECM.

All models agree on the longevity of the upcoming short cold snap with similar synoptics from all models up to next Thursday. A light West to NW flow with some clear spells over the South at first tonight will give way to cloud cover later in the night to join all other areas in a breezy and slightly milder WNW flow tonight and tomorrow. Through the day though tomorrow as a Low pressure area slips SE over Europe winds turn towards the North and brings colder and clearer conditions slowly South to all areas later tomorrow. pressure is then shown to build strongly over the UK for the first half of the week with temperatures below normal with sunny crisp days but very cold nights with extensive frost and the odd wintry shower towards the extreme early in the week.

GFS then shows Low pressure sweeping in from the Atlantic pushing the cold air quickly away. In the process a short spell of snow could occur in the North before rain and strong winds push North and East to all areas to end the week. The weekend would be quite stormy in places with heavy rain in the form of bands or showers falling into areas that least need it. Through FI the pattern remains unstable and relatively mild though with some quieter frosty interludes particularly towards the end of the run when the European High pressure which lurks too far to the East throughout the run makes an attempt to push back.

The GFS Ensembles show a cold snap early this coming week before temperatures retun to near the long term mean for the rest of the run with very few members supporting the colder evolution at the end of the run that the operational run above shows. The period will be low pressure dominated especially in the North and West with rain at times.

The Jet Stream shows the flow currently moving South or SE over the UK before a weakening of the flow occurs briefly before a renewed surge comes storming across the Atlantic towards the UK in a week or so.

UKMO for midday on Saturday shows a squally and showery Westerly flow over Southern Britain while Northern Britain are likely to see further persistent rain following on from that of the previous days. Temperatures would be near normal but it will feel cold in the strength of the wind.

ECM tonight shows a broadly similar setup to UKMO at 144hrs with Low pressure out to the NW feeding the UK with showers or longer spells of rain for all. It would feel cold in the wind with some snow likely on Northern hills at times. Late in the run Low pressure remains close to or over the UK with the Continental High tantalisingly close with the threat of rather colder conditions developing soon after 240hrs as the Atlantic winds down and Northern blocking slowly develops once more.

In Summary a wet spell is to come later in the week. After the first few days of the week being cold with widespread frost only a transitory snowfall looks likely for the North and East over the hills while in the SW the charts from all models show some worrying conditions for areas in the SW once more that have not yet recovered from the last bout of flooding. Heavy rain looks to be widespread and heaviest in the SW with strong winds to boot. There are some glimmers of hope for coldies in the late stages of the ECM run I feel and the consolation of losing the Easterly is that the large Continental High remains tantalisingly close through the entire output of all models. However, any true wintry weather is looking increasingly unlikely anywhere this side of Christmas if tonight's output verifies.

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Have moved a handful of posts from here to the mayhem / emotions thread - if your post isn't actually some sort of discussion on the model output please use an alternative thread. For example - 'I hope the block wins', 'I hope the ECM is better' etc - are all fine for the mayhem thread but don't really constitute model discussion :)

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Would slight westward shifts of the high over the next few runs make a big impact at the end of the week? Sorry, still learning!

To help answer your question - which high do you mean?

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Will be interesting tonight where the ECM mean goes at day 8/9/10 . Tonight's Det, compared to this mornings mean, brings the Scandi/Russian high's influence much further west than the 00z mean.

Det

Recm2161.gif

00Z Mean

Reem2161.gif

Background signals, as others have pointed out, don't support such a quick breakdown of blocking patterns and the Atlantic just storming in and setting up a zonal flow is still very much an uncertain prognosis.

I spot falling heights to the east of the Russian high on the ECM, one to watch.

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On the 12z GFS Ensembles, what is it that occurs on the operational run that doesn't happen on the half a dozen runs that keep the UK under a polar continental influence for an additional 2 days?

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i just had a look back at the ecm runs from the middle of last week to see where they went wrong as i just dont buy the scandi shortwave for causing the complete failure. and surprise surprise, it didnt. its a combo of the scandi shortwave preventing the russian ridge from supporting our fledgling block plus there should have been a ridge coming off the eastern seaboard tomorrow/monday which would deflect the second shortwave on a more ne interior track and enable this east coast ridge to add support to our block from the west. the lack of this east coast ridge is a double whammy. firstly, it means there is absolutely no support for our ridge due to the shortwave drama to our northeast and secondly, (more importantly) the second shortwave now flows straight into the west atlantic depression and gives it the energy to rush straight across the atlantic. our ridge stands no chance and to make matters worse, the shortwave to our northeast is sufficiently far enough north as it tumbles the energy southwest to draw the low heights of atlantic attack at that lattitude towards it. take the scandi shortwave away and we would probably have the cold air far enough west to repel the initial atlantic attack to our south giving a dramatic battleground scenario. keep the east coast ridge and the atlantic isnt strong enough to smash through our ridge and the cold would tumble in from the northeast. i dont think the combination of these two things happening at less than day 6 could reasonably have been factored into any forecast. thats why the cold period upcoming will be so shortlived.

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Sorry, the Russian high

I don't think that it is the high moving west - more a case of the Atlantic troughs moving west. The suggestion is that they will eventual move to cover the UK and then stall against the block. Obviously the less inroads that the Atlantic makes, the longer the cold air survives, and a battleground scenario arises.

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All aboard the next rollercoaster!

I just can't help myself! So now that we've printed yet another t-shirt with words Failed Easterly on it we move on, pick up the pieces and place the sledge back into storage!

The ECM is a vast improvement on this mornings 00hrs run but we need to put the Russian high in context, we see many highs there just teasing and thats where they stay.

So we've seen the Atlantic gear up, the question is really how far low pressure gets into Europe, will we hold onto decent heights to the north and east and will another ridge appear to the west as per the ECM 240hrs.

The important thing with the set up is maintaining the Russian high sufficiently north and low pressure track at least ese, as the low weakens you might get the high ridging over the top.

Historically its not a set up that has a great success rate, whats new I hear you say!

Now that we have the Atlantic moving in the best I think we can hope for is that the models have over reacted to that signal and will pull back a little and at least keep the jet a little further south.

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the russian high is currently a 'warm' upper ridge. i wouldnt expect that to move west. at higher latitude where it was created from the remnants of the arctic high, it does manage to influence westwards into greenland and beyond. if cold uppers are drawn around the eastern side of that russian ridge and advected westwards into eastern europe then the warm upper ridge can become 'cut off' over ne scandi/nw russia. in that case, the dense cold air can push west more easily.

the ecm mean in its latter stages is, dare i say it, very promising as the low heights begin to fill out!

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Against the background signals and expected upper air patterns, that ecm fi makes much more sense. We've seen trough disruption in some low res gfs runs aswell so i supect it will be full steam ahead for round 3 of the winter 12/13 ramp in a few days!! Starting to see signs of model stress syndrome and a few of you seem to have lost faith. Its only dec 7th!!

Cough... 8th... :-)

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CH

As I said to John earlier (though in a slightly different context) you can look at this either way. I would put it to you from the point of view that the shortwave prevents the HP's from linking to our north (at least on current modelling) - without this link up, the Scandi/Siberian HP isn't pulled further west, and so is (potentially) blasted away by an atlantic LP

It is equally true that you could say that the HP's themselves were the determining factor...but I tend to look at it from the point of view of the longwave pattern dominates, and shortwave interferences alter this pattern.

I think either point of view is equally correct - they are not mutually exclusive

SK

Yep - fair enough: it'd the old chicken and egg scenario. No definitive answer I expect.

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All aboard the next rollercoaster!

I just can't help myself! So now that we've printed yet another t-shirt with words Failed Easterly on it we move on, pick up the pieces and place the sledge back into storage!

The ECM is a vast improvement on this mornings 00hrs run but we need to put the Russian high in context, we see many highs there just teasing and thats where they stay.

So we've seen the Atlantic gear up, the question is really how far low pressure gets into Europe, will we hold onto decent heights to the north and east and will another ridge appear to the west as per the ECM 240hrs.

The important thing with the set up is maintaining the Russian high sufficiently north and low pressure track at least ese, as the low weakens you might get the high ridging over the top.

Historically its not a set up that has a great success rate, whats new I hear you say!

Now that we have the Atlantic moving in the best I think we can hope for is that the models have over reacted to that signal and will pull back a little and at least keep the jet a little further south.

Regardless, what happens, nobody summarises the models as well and with the necessary injection of humour as you do!

Karyo

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Could some one please tell me what time this model updates?

15DAAGSE_06260_NWT.png?6767676767

This one already has:

eps_pluim_tt_06260.png

Pretty much the same split as this morning but pretty ominous still.

Right towards the end of the period the trend is slightly downwards - thats about the best I could say for these tonight

SK

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Thank you. Sorry if it was a stupid question, it's all a learning curve for me and I appreciate the response :-)

It wasn't a stupid question. The only stupid question is the one not asked when it could have been...

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Maybe the 00z's will throw coldies a lifeline since the 12z's are hinting at some form of undercut as the unsettled weather spreads towards the uk from midweek onwards. Northern britain could have a period of heavy snow after midweek which may persist for a fair while before clearing northeast with less cold uppers following it from the south, maybe a few more twists and turns to come but on balance, not what most of us were anticipating, so lessons learned hopefully..until the next time that is.smile.png

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As Nick S, once the models have got hold off the Atlantic winning they can over-egg the Eastward advance of the jet. So we need to be looking at subsequent runs to see how much blocking can maintain at High latitude. What we don't want to see is pressure rising over mainland Europe, as long as he core of heights is the Russian High and we don't see those deep purples over Greenland, then we are never far from potentially interestingly developments.

At least the saga that has occurred has taken place at he beginning of the winter period, rather than much later on as has been the case in the past. Ok, we have managed to put a penalty over the crossbar but a long way to go.

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