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Model Output Discussion - The final stretch to Christmas


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Posted
  • Location: Eshaness, Shetland Islands
  • Weather Preferences: Cool and Stormy
  • Location: Eshaness, Shetland Islands

    Re tomorrow's event, local North Midlands forecast said that the risk of widespread snow was unlikely and Metoffice warning was an *advisory* as it is marginal regarding rain/snow. Although it might come down to a nowcast event.

    They said that above 250m - southern Derbyshire there is a greater risk of settling snow, but it doesn't expect any real problems I.e travel disruption. Rain/sleet at low levels across the whole region and a rain event south of Nottingham.

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    Mean while in the real world away from the MOD... A tragic accident has cost 6 lives in Glasgow. yes this is off topic but a timely reminder of just how unimportant the weather really is in our lives.

    There is an enormous lack of respect for other people in this thread at the moment. I suggest that if one doesn't have something to add to the model discussion with a salient chart or pertinent inf

    Model uncertainty throwing both operational and ensemble data into discontinuity has proved as rife as was expected a week ago - when AAM flipped to negative tendency along with GWO phasing that was i

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    Posted
  • Location: Cardiff, Wales
  • Weather Preferences: Snow, Thunder & Lightning, Thundersnow, Storms, Heatwave
  • Location: Cardiff, Wales

    GFS parallel keeping it settled and cold with surface cold past the new year with a new ridge building in. Wonder if we can hold onto the high into Jan until we see further possibilities due to the start further into Jan? Personally much rather the MLB over us than a cool cyclonic pattern. Not sure the high will shift as quickly as the models shows as it comes closer to the timeframe but we'll see.

    post-16336-0-60876100-1419547629_thumb.j

    ECM mean for days 11-15 isn't great though.

    Edited by bradythemole
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    Posted
  • Location: Morecambe
  • Location: Morecambe

    Here's tomorrow's (Boxing Day) chart modelled by GFS at T+72 (i.e. only two days ago - Tuesday 12Z)

     

    attachicon.gifT+72 Tuesday 12Z.jpg

     

    How things change.  Look at the mid Atlantic compared to how it's modelled now.  For those worrying over T+168 - I'd say chill with a wee sherry and a mince pie  :smiliz19:

     

    Looks fairly similar too me Shuggee, obviously details will change but it still shows an ridge and a shallow low pressure system heading through the UK on boxing day?

     

    Of course, the trend in the medium to longer term can quickly change, especially if conditions in the stratosphere are favorable to potentially disrupt the weather patterns but the trend for Next week looks to be one of things to slowly getting milder from the West, just how quick that transition is to happen will be uncertain at this stage mind, the high could be more stubborn or the Atlantic could come in quicker than it is model now. 

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    Posted
  • Location: Northampton
  • Location: Northampton

    Hello, what does it give us to hold onto?

    The pattern has not been flattened so much with HP still close by

    post-9179-0-92943100-1419547484_thumb.pn

     

     

    Leading to some cold frosty weather (at least in England and Wales)

    post-9179-0-24237800-1419547517_thumb.pn

     

    And therefore the potential that it could develop into something more interesting later.

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    If there is missing data? how could you filter it?

     

    Sorry badly worded, best you visit any of the main weather centre sites, NOAA, Met, ECMWF, but perhaps the word should have been monitored. Before any model run data is checked and tested for validity against amongst other things the last set of data, the averages for even a particular station over any time interval. Hugely time consuming but not for models set up to do this sort of thing.

    Not a very good answer but like I suggested e mail them or search for example the Met O web site with lots of information on how their different models are run and monitored.

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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

    The extended ens picks this cold spell 14/12 when there was title apparently to look forward to on the modelling mucka. Of course they could be wrong but they don't often 'flip' with the long wave pattern.

     

    But I picked it before they went cold.  :p

     

    No, of course you are right they don't often flip back again but the longwave pattern prediction in this case is only as good as the jet prediction and though we know the jet will fire up I'm not at all sure it is not going to take a more southerly track or that it wont meet a stronger and better orientated block than currently being modelled and that all the energy will ride over the top.

     

    At the every least I see the MLB being more stubborn and offering some chances of a more amplified pattern than currently being shown from say 120/144 even if that is not a classic Easterly set up.

    If zonal is the new trend we will see that continued right through the 26th and 27th.

    I just see us as having a good 48h to turn the output away from this relatively quick descent to zonal which I really don't trust at all.

    Edited by Mucka
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    Posted
  • Location: Midlothian
  • Location: Midlothian

    Better undercut holds onto a slight ridge further north towards Scandinavia hence keeping colder uppers for longer ...high doesn't sink South ...not fantastic but better than the 12zs

    ok thanks :)

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    Posted
  • Location: st albans
  • Location: st albans

    Regarding the missing flight data, clearly there are fewer readings above 60N, especially Greenland and n Canada. If we were seeing a big change in the 12z and 18z related to developments in that region compared to the 00z runs then I guess we could raise the issue but it looks pretty consistent to me.

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    Looking at the anomaly charts, really answering someone else questioning whether means give a reliable idea of what is to come.

    Certainly in terms of using the anomaly charts then I find them rarely wrong provided I interpret them correctly. To me they indicated the probability of colder weather prior to the end of our longish summery type weather into November. Then the spell of weather we then had, then the prediction of it turning less mild, even colder with mainly Pm type air. Obviously they do not indicate major storms in any detail but they do indicate when the upper air is in the correct pattern to allow storms to develop and I believe I indicated that about 2 weeks ago that at least one substantial storm was likely. Even the, to me misused phrase, 'short wave' can be suggested in certain wave patterns. The 'short wave' is actually something in the upper air, quite often at 700mb or 500mb, much as Nick F indicated 24 hours or so ago.

    Their present guidance suggests a spell of mainly anticyclonic weather 6 days plus especially for the south then a more south of west upper pattern with the main trough yet again being from N Canada south and a pretty strong Atlantic flow, this especially north of 50N or so, so northern areas more affected than the far south.

    But yey ho, forecasting is a science but it is not perfect by any means and the weather may well make a monkey out of this prediction.


    But I picked it before they went cold.  :p

     

    No, of course you are right they don't often flip back again but the longwave pattern prediction in this case is only as good as the jet prediction and though we know the jet will fire up I'm not at all sure it is not going to take a more southerly track or that it wont meet a stronger and better orientated block than currently being modelled and that all the energy will ride over the top.

     

    At the every least I see the MLB being more stubborn and offering some chances of a more amplified pattern than currently being shown from say 120/144 even if that is not a classic Easterly set up.

    If zonal is the new trend we will see that continued right through the 26th and 27th.

    I just see us as having a good 48h to turn the output away from this relatively quick descent to zonal which I really don't trust at all.

     

    You cannot separate the long wave pattern from the jet pattern, the two are really the same and one without the other is not really possible. Chicken and the egg as so often in meteorology. The trick, or rather the training, is to be able to see where the wave pattern may cause the jet to behave in a particular manner.

    Edited by johnholmes
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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

    Looking at the anomaly charts, really answering someone else questioning whether means give a reliable idea of what is to come.

    Certainly in terms of using the anomaly charts then I find them rarely wrong provided I interpret them correctly. To me they indicated the probability of colder weather prior to the end of our longish summery type weather into November. Then the spell of weather we then had, then the prediction of it turning less mild, even colder with mainly Pm type air. Obviously they do not indicate major storms in any detail but they do indicate when the upper air is in the correct pattern to allow storms to develop and I believe I indicated that about 2 weeks ago that at least one substantial storm was likely. Even the, to me misused phrase, 'short wave' can be suggested in certain wave patterns. The 'short wave' is actually something in the upper air, quite often at 700mb or 500mb, much as Nick F indicated 24 hours or so ago.

    Their present guidance suggests a spell of mainly anticyclonic weather 6 days plus especially for the south then a more south of west upper pattern with the main trough yet again being from N Canada south and a pretty strong Atlantic flow, this especially north of 50N or so, so northern areas more affected than the far south.

    But yey ho, forecasting is a science but it is not perfect by any means and the weather may well make a monkey out of this prediction.

     

    You cannot separate the long wave pattern from the jet pattern, the two are really the same and one without the other is not really possible. Chicken and the egg as so often in meteorology. The trick, or rather the training, is to be able to see where the wave pattern may cause the jet to behave in a particular manner.

     

    I'm referring to the jet buckling and splitting.

    Did you misread the anomaly charts when you were saying there was no sign of cold for 14 days or were the anomaly charts wrong at that time?

    Edited by Mucka
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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    I'm referring to the jet buckling and splitting.

    Did you misread the anomaly charts when you were saying there was no sign of cold for 14 days or were the anomaly charts wrong at that time?

     

    Bit late M but I will have to search out the day you quote to say which, unless you can tell me then I can look at my file on anomaly charts for that date please?

    And the jet only buckles and splits when the upper air conditions are 'right'. Again something that can be missed unless you are really careful in watching them over several days. The old maxim of never ever take one output from any model is just as valid with anomaly charts as I am sure you and other have heard me say often enough?

    You are of course welcome to all 28 pages of my December anomaly file if you would like that. Again that is IF I can remember how to create a pdf file to put it in!

    Edited by johnholmes
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    Posted
  • Location: st albans
  • Location: st albans

    Surely any long wave pattern is driven by strength of the jet which in turn is fuelled by positioning and energy coming out of our old friend the Polar vortex....anomaly forecasts are only as good as what's predicted but cannot factor in what's going on in the strat...hence possible dramatic change in model factoring sometimes John?

    But each model is one large atmospheric dynamic , trop and strat together. admittedly, gefs top out at 10 hpa ( recretos is best to verify that) but ECM ens go right to the very top of the strat and actually a bit beyond.

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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

    Bit late M but I will have to search out the day you quote to say which, unless you can tell me then I can look at my file on anomaly charts for that date please?

     

    I remember we had a discussion on it a while back before the now failing Scandi high was being modelled.

    You were saying the anomaly charts showed no sign of either blocking or cold within 14 days and I said I agreed within 10 days but the trend was toward possible blocking within the 14 day timeframe due to trends within the ensembles and operational output at that time.

    I agree with you in general on the usefulness of anomaly charts but I would always suggest taking account of any trends within other output including ensembles before making a judgement on a snapshot anomaly chart.

     

    I think likely the anomaly charts were not accurate at that time because they were simply portraying the old signal and ignoring the new trend emerging because the weaker signal gets washed out in the mean.

     

    I am up for a while yet so I will see if I can find it  and PM you.

     

    "And the jet only buckles and splits when the upper air conditions are 'right'. Again something that can be missed unless you are really careful in watching them over several days. The old maxim of never ever take one output from any model is just as valid with anomaly charts as I am sure you and other have heard me say often enough?"

     

    I'm not sure what you are getting at to be honest.

    If the jet profile is modelled differently then the longwave pattern is modelled differently and yes you can turn it around, chicken and egg.

    If the block is at a higher latitiude and stronger than currently modelled around day 5/6 then the jet will behave differently when it meets it. If it is modelled to buckle or more especially undercut then the longwave pattern will look different than if it is modelled to ride over the top.

    Edited by Mucka
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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    Surely any long wave pattern is driven by strength of the jet which in turn is fuelled by positioning and energy coming out of our old friend the Polar vortex....anomaly forecasts are only as good as what's predicted but cannot factor in what's going on in the strat...hence possible dramatic change in model factoring sometimes John?

     

    Indeed so, but you may note that I rarely if ever attempt to give a suggested upper air pattern beyond the 14-16 day time scale. On occasion I may use the MJO to suggest what the 500mb anomaly pattern may be beyond that but I don't pretend to be an expert on the Stratosphere, too complicated for me.

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    re mucka

     

    I agree with you in general on the usefulness of anomaly charts but I would always suggest taking account of any trends within other output including ensembles before making a judgement on a snapshot anomaly chart.

     

    I think likely the anomaly charts were not accurate at that time because they were simply portraying the old signal and ignoring the new trend emerging because the weaker signal gets washed out in the mean.

    I never post in here without having looked at every chart I can find although my post rarely refers to anything other than the anomaly charts (the 3 I use), now and then the MJO will get a mention, as will AO, NAO etc, and the synoptic charts. Obviously I cannot look at every chart that is wrong to suggest so but I do attempt to have a quick reference across all types before posting.

    We all have our favourite ways of trying to predict what might happen and none of us are infallible, that is the fun of it. Just sad that sometimes some, not you, descend to personal digs.

    If you can give me a rough idea of the date(s) you are talking of I will have a look tom orrow am, too late now, too much alcohol and past my bed time!

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    Posted
  • Location: st albans
  • Location: st albans

    Thanks wasn't sure if anomaly charts factored in possible strat events.

    The NOAA anomaly charts are gefs though aren't they?

    Naefs when automated (which is gefs and Canadian). I think that the Canadian ens may go higher than 10hpa. Anyway, your point is valid in that respect but when made by forecasters, they include ECM charts as and when the forecast deems appropriate.

    Given that the current warmings are well established below 10 hpa, I'm not sure that there will be that much of a surprise in the output going forward. Where there is a warming predicted to begin above 10hpa then there is an argument that models which don't top out high enough could miss it in their output due to initialisation data not seeing this.

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    Posted
  • Location: South Essex
  • Location: South Essex

    Okay, very very small straw to clutch from GEFS.

     

    Ptrb 14 takes us from here

     

    http://www.meteociel.fr/modeles/gefs_cartes.php?code=14&ech=72&mode=0&carte=0

     

    to this at 180

     

    http://www.meteociel.fr/modeles/gefs_cartes.php?code=14&ech=180&mode=0&carte=0

     

    I suppose it does illustrate that a small tweak might make a big difference. In terms of the other runs all roads lead to Rome sadly (quite literally as far as the cold air goes).

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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

    re mucka

     

    I agree with you in general on the usefulness of anomaly charts but I would always suggest taking account of any trends within other output including ensembles before making a judgement on a snapshot anomaly chart.

     

    I think likely the anomaly charts were not accurate at that time because they were simply portraying the old signal and ignoring the new trend emerging because the weaker signal gets washed out in the mean.

    I never post in here without having looked at every chart I can find although my post rarely refers to anything other than the anomaly charts (the 3 I use), now and then the MJO will get a mention, as will AO, NAO etc, and the synoptic charts. Obviously I cannot look at every chart that is wrong to suggest so but I do attempt to have a quick reference across all types before posting.

    We all have our favourite ways of trying to predict what might happen and none of us are infallible, that is the fun of it. Just sad that sometimes some, not you, descend to personal digs.

    If you can give me a rough idea of the date(s) you are talking of I will have a look tom orrow am, too late now, too much alcohol and past my bed time!

     

    Well if memory serves you stated at the time you didn't bother looking through the ensembles for trends which was part of the discussion though you certainly didn't dismiss the usefulness of doing so but all that is off memory. I will have a look through my posting history later and PM you.

     

    Yes of course we all get things wrong all the time and that is part of the fun and nobody should worry about being wrong about the weather - much better than I get it wrong so there is no shame.

    I still find I learn all the time on this forum.

     

    Sorry, I was a little abrupt but certainly no personal dig intended. Still time to wish you a merry Christmas.  :smiliz19:

     

     

    Latest Euro4 prediction

     

    14122700_2518.gif

    Edited by Mucka
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    Naefs when automated (which is gefs and Canadian). I think that the Canadian ens may go higher than 10hpa. Anyway, your point is valid in that respect but when made by forecasters, they include ECM charts as and when the forecast deems appropriate.

    Given that the current warmings are well established below 10 hpa, I'm not sure that there will be that much of a surprise in the output going forward. Where there is a warming predicted to begin above 10hpa then there is an argument that models which don't top out high enough could miss it in their output due to initialisation data not seeing this.

     

    FYI, GEFS goes up to 2hPa.

    http://www.wmo.int/pages/prog/arep/wwrp/new/documents/GEFS_status_plan.pdf

     

    Will soon be 0.2hPa in the next update planned in 2015 !

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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

    ECM London ensembles pretty much solid on a warm up from around day 5 though interestingly there is no real mild coming in from the Atlantic.

     

    ensemble-tt6-london.gif

     

    John I PMd you - re discussion 12 Dec.

    Edited by Mucka
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    Posted
  • Location: Northampton
  • Location: Northampton

    FYI, GEFS goes up to 2hPa.

    http://www.wmo.int/pages/prog/arep/wwrp/new/documents/GEFS_status_plan.pdf

     

    Will soon be 0.2hPa in the next update planned in 2015 !

    Thanks Sylvain,

     

    Some significant improvements planned or early next year - especially the horizontal resolution. Not sure taking it out to 720 hrs as planned 2018 is a good idea - we will be discussing forever on here.

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