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Model output discussion - here comes the beast!


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Posted
  • Location: Broxbourne, Herts
  • Weather Preferences: Snow snow and snow
  • Location: Broxbourne, Herts
    2 minutes ago, Robbie Garrett said:

    It's been a very long time since I model watched.  But does the GFS still have a westerly bias?  It's always defaulting to Zonal in fantasy island.

    I'd argue not judging by the amount of runs it has had over the years that have showed easterlies that never materialised. 

    This looks like being a superb exception.  But the 'failures' I've seen lead me to believe that any bias it may have is not westerly based....

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    Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and majo

    Come on those looking for the breadown before the major cold and snow has begun You will be very lucky if that is the correct word to see this in ANY winter in the rest of your lives I would sugg

    Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of nex

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    Posted
  • Location: Sedgley Black country 731ft 222 metres
  • Location: Sedgley Black country 731ft 222 metres

    Short ensembles. A couple of mild outliers that are distorting the mean. Some very cold runs in there 

    IMG_1251.GIF

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    Posted
  • Location: Dundee - 140m ASL
  • Location: Dundee - 140m ASL
    3 minutes ago, kold weather said:

    Yep the GFS ensembles agreeing with it. I suppose it is a possibility though I'd rank it low on the table of likely outcomes, especially given the GFS is pretty bad at lowering heights too rapidly in blocking setup. The idea of a low coming SW nearby our region however does have good support from other models. It's just because the GFS weakens the upper high too fast it's all placed further north than other models. I strongly suspect the GFS will shift some way tomorrow. The others may also move a little further north, esp UKMO.

    A shift south on the GFS and a nudge North on the others would be ideal for everyone! If the GFS flips tomorrow around the 132hrs mark where the difference begins then it will be a bit of a humiliation as it is backed by its ensemble suite.

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    Posted
  • Location: Erith. SE London/kent 40m asl
  • Weather Preferences: Winter Snow, extreme weather, mainly sunny mild summers though.
  • Location: Erith. SE London/kent 40m asl

    18z short ens for central England, quite a few there going even colder.:D

    graphe_ens3.gif

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    Posted
  • Location: Remote North Yorkshire 474ft ASL
  • Weather Preferences: All seasons veteran of the 1981 winter
  • Location: Remote North Yorkshire 474ft ASL

    I'd like to share these models one at T+144 hrs and the other at T+168 hrs. 

    I think GFS is displacing the 1055mb high pressure to quickly. Northwards. 

    Easterlies of this magnitude last longer than is suggested by some models .

    Only based on experience. 

    What ever happens at this point it looks very cold and snowy from Sunday night onwards.

    I was wondering at what point the met office warnings will appear. 

    There's lots going on in the models it' certainly keeping me on my toes.

    I aren't sure if this post will be removed I'm unclear what's  relevant to make an accurate post to this thread. 

     

     

    18022818_2118.gif

    18022718_2118.gif

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    Posted
  • Location: Chichester West Sussex
  • Weather Preferences: Cold and snow
  • Location: Chichester West Sussex
    3 minutes ago, weirpig said:

    Short ensembles. A couple of mild outliers that are distorting the mean. Some very cold runs in there 

    IMG_1251.GIF

    I'd say those milder runs are the ones where the high pressure is to close to the uk and therefore the coldest air is dragged into mainland Europe. 

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    Posted
  • Location: Barrhead, East Renfrewshire
  • Weather Preferences: Severe gales, thunderstorms, snow
  • Location: Barrhead, East Renfrewshire
    1 hour ago, Ayrshire weather said:

    Hmm not liking this so far....

    h850t850eu.png

    Awrite Stevie Wonder!

    I stay not far from you and that chart is great with lots of snow potential for the whole of the UK and Ireland. 

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    Posted
  • Location: Wombwell, South Yorkshire (75m / 246ft ASL)
  • Weather Preferences: Summer Sunshine / Winter Snow
  • Location: Wombwell, South Yorkshire (75m / 246ft ASL)
    1 minute ago, snowray said:

    18z short ens for central England, quite a few there going even colder.:D

    graphe_ens3.gif

    Tasty!  Those 500hPa temps are darn cold.  Polar low territory for sure.  I have a feeling that come this time next week some areas of the UK could be buried!  :cold:

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    Posted
  • Location: Grays, Thurrock
  • Location: Grays, Thurrock
    43 minutes ago, nick sussex said:

    The GFS goes a bit crazy with the shortwaves but put that aside , even with it on LSD it still manages to improve in terms of overall pattern with the low to the sw now splitting eastwards.  

    The block over Greenland is also better placed at day 8.

    I am starting to think we might actually get direct hit with the coldest uppers and those spectacular runs from earlier this week will start to reappear nearer the time.

     ECM wants to take vortex north then south east and drop shortwave through Svalbard which then splits the block by 192.

    ECH1-192.GIF?21-0

    GFS handles the vortex very differently with the vortex staying intact with it riding around the outside of the block.

     gfsnh-0-162.png?18

    now imagine if the GFS is handling the vortex movement correct but is handling the Norwegian shortwave incorrectly.

    we could keep the easterly feed longer as the vortex doesn't drop energy through the block but just squeezes the eastern end south a bit. 

    The South West part of our block would be stronger if the shortwave is weaker and consequently more energy would go under the block pushing the really cold uppers over us.

    ensemble number 2 is example of what I am thinking

    gensnh-2-1-180.png

     

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    Posted
  • Location: Shirley, Croydon, Greater London
  • Location: Shirley, Croydon, Greater London

    Confirmed.....Today's GFS 12z & 18z are outliers......With my trained eye I knew there was something wrong with both outputs....ECM Ensembles go for rigid cold & have ignored GFS on their graph :cold::D:yahoo:

    Edited by yamkin
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    Posted
  • Location: Erith. SE London/kent 40m asl
  • Weather Preferences: Winter Snow, extreme weather, mainly sunny mild summers though.
  • Location: Erith. SE London/kent 40m asl
    7 minutes ago, Smiler1709 said:

    I'd say those milder runs are the ones where the high pressure is to close to the uk and therefore the coldest air is dragged into mainland Europe. 

    Yes I make you right there, tomorrows runs will make everything a lot clearer I'd say.....

    Well maybe?:laugh:

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    Posted
  • Location: Marlborough, North East Wiltshire 143M/469ft ASL
  • Weather Preferences: Cold and snow in the winter, warm and dry in the summer !
  • Location: Marlborough, North East Wiltshire 143M/469ft ASL

    One piece of advice I often heard on here was to compare the same run from day to day to see where trends are actually heading.

    Not sure why, but in NW Extra there's a handy tool for doing just this.

    In the images below I've compared the SLP and 850T maps for 1200 on Tuesday 27th Feb from the GFS and ECM 12Z runs from the past three days.

    Interesting that the GFS seems to be chopping and changing quite a bit whereas the ECM is remarkably similar in its forecast.

    Of course it doesn't mean either of them is right but would seem to suggest the ECM has not been wobbling as much as we think. The changes maybe are in fact between it's 0Z and 12Z runs. 

    Maybe there is something in the idea that it's best to compare like for like runs to get an idea of the trend rather than analysing each and every one?

    image.thumb.png.2c28400d52564b2f43c8fc1540f8c392.png

    image.thumb.png.236a16abea003f2d726d9be6ccbbdd2d.png

      

    Edited by wiltshire weather
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    Posted
  • Location: Sheffield
  • Weather Preferences: thunderstorms, heatwaves, extreme weather
  • Location: Sheffield
    1 minute ago, yamkin said:

    Confirmed.....Today's GFS 12z & 18z are outliers......With my trained eye I knew there was something wrong with both outputs....ECM Ensembles go for rigid cold & have ignored GFS on their graph :cold::D:yahoo:

    12z was only an outlier in deepest FI and was 'rigid' cold before that. 18z is also cold. What exactly is wrong?

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    Posted
  • Location: uxbridge middlesex(south east england)
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(south east england)
    6 minutes ago, Steel City Skies said:

    12z was only an outlier in deepest FI and was 'rigid' cold before that. 18z is also cold. What exactly is wrong?

    Yes i agree i find @yamkin post a little odd as there is quite stern support for both suites 12/18z....

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    Posted
  • Location: Shirley, Croydon, Greater London
  • Location: Shirley, Croydon, Greater London
    11 minutes ago, Steel City Skies said:

    12z was only an outlier in deepest FI and was 'rigid' cold before that. 18z is also cold. What exactly is wrong?

    GFS op on pressure graph is an outlier from the 28th Feb

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    Posted
  • Location: uxbridge middlesex(south east england)
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(south east england)

    Current temps nw/europe.

    Our air source for next week cooling considerably...

     

    Reurmett (2).gif

    Screenshot_2018-02-21-23-52-20.png

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    Posted
  • Location: Shirley, Croydon, Greater London
  • Location: Shirley, Croydon, Greater London
    8 minutes ago, tight isobar said:

    Yes i agree i find @yamkin post a little odd as there is quite stern support for both suites 12/18z....

    GFS op on pressure graph is an outlier from the 28th Feb

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    Posted
  • Location: Cottingham
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Cottingham

    Right last one from me today, 18z GFS ens, Scandi cold pool and its path over the UK (12z in brackets):

    North UK - 4% (28%)
    Direct - 79% (61%)
    South  - 7% (7%)
    Fail - 11% (4%)

    - Many of the runs have a very unstable atmosphere developing on Tuesday.
    - This is because of the cold pool over Scandi
    - Part of the cold pool charges at us on Monday
    - Another part waiting behind in Scandi causes instability in the North Sea
    - Compared to the 12z, a slight increase in solutions favouring a direct hit
    - 3 members fail to get the cold pool over us, these ones are weird though, the high remains rooted over NE Russia and fails to retrogress to Greenland which would go against every background signal.
    - Op and control given a bit of extra weighting hence big drop in northward path on the 18z.

    If the UKMO has a direct hit tomorrow then I can't see any reverting to something else from there.

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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE
    11 minutes ago, wiltshire weather said:

    One piece of advice I often heard on here was to compare the same run from day to day to see where trends are actually heading.

    Not sure why, but in NW Extra there's a handy tool for doing just this.

    In the images below I've compared the SLP and 850T maps for 1200 on Tuesday 27th Feb from the GFS and ECM 12Z runs from the past three days.

    Interesting that the GFS seems to be chopping and changing quite a bit whereas the ECM is remarkably similar in its forecast.

    Of course it doesn't mean either of them is right but would seem to suggest the ECM has not been wobbling as much as we think. The changes maybe are in fact between it's 0Z and 12Z runs. 

    Maybe there is something in the idea that it's best to compare like for like runs to get an idea of the trend rather than analysing each and every one?

    image.thumb.png.2c28400d52564b2f43c8fc1540f8c392.png

    image.thumb.png.236a16abea003f2d726d9be6ccbbdd2d.png

      

    I think it depends on the timeframes .

    Closer in there should be less variation between the different runs. It could be that certain synoptic patterns are more sensitive to slightly different amounts of initiaiization data say from sat and aircraft obs etc at the longer range.

    In this instance because of the changes in the strat and the second warming this might be causing a bit more variation with the high set up to the north and north east.

     

     

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    Posted
  • Location: Chichester West Sussex
  • Weather Preferences: Cold and snow
  • Location: Chichester West Sussex
    22 minutes ago, snowray said:

    Yes I make you right there, tomorrows runs will make everything a lot clearer I'd say.....

    Well maybe?:laugh:

    Hope so, ideally I'd like the high pressure over Scandinavia so we can squeeze that easterly for longer ?

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    WHY I BELIEVE THAT THE GFS OUTPUT FOR WEEK 2 WAS COMPLETELY WRONG

    My post yesterday (now buried on page 2 of this thread) compared the run into to the predicted upcoming cold spell to some earlier severe spells dating back to 1947 and up to 2013. I will make further reference to the March 2013 spell towards the end of this post when I compare it to the current and predicted set up. I intend to demonstrate with plenty of evidence why I feel that the GFS is being far too progressive in bringing back the Atlantic after the turn of the month. In fact, I do not necessarily see this happening until well after mid-March, although one or two very brief less cold interludes can never be completely ruled out. This was based on the previous few runs up to today's 12z. I see that the 18z (which rolled out while I was writing up this post) has a slightly colder solution again but still ends with less cold uppers over the UK and is a long way from the 12z ECM and UKMO solutions.. 

    CURRENT PATTERN AND CONDITIONS

    In summary, the record strength sudden stratospheric warming (SSW) has fully impacted and reversed the winds with the Arctic cold being displaced towards the middle latitudes. The jet stream has weakened and split and the Atlantic LP train has ground to a halt. The persistent and very strong Canadian PV is coming under attack and all models show it breaking up over the next few days with the main lobe transferring across the Arctic to Siberia during the next week of so. The blocking patterns are becoming established. During the next few days, the HP close to the UK is set to link up with a vast expanse of HP extending from northern Siberia through Russia and pushing westwards to Scandinavia and beyond. Once established, this is likely to dominate the pattern for many days if not weeks. The deep cold over north Asian and Siberia is surging westwards. I show the "current" charts below from the 12z run. I used the GEFS simply because it starts with T+0 (GFS operational run starts with T+6):

                           Jet Stream                                               Surface Pressure                                              850 Temps                                            2m Surface Temps

     5a8dc89a3fe7a_gensnh-0-3-0(2).thumb.png.6b22ea42f84717b0092fd21b590696d7.png      5a8dc88a9559e_gensnh-0-1-0(1).thumb.png.cedced8935af96bd1b80c61af522221f.png      gensnh-0-0-0.thumb.png.3fbedce9a45841ee8050d43a5555b9cc.png      gensnh-0-4-0.thumb.png.f5b3927d121311e273d38151857f2cd5.png

    Now, I'll go through this in a little more detail. I had a glance through the strat thread to get the latest on the SSW and I must thank @Blessed Weather for directing me to @chionomaniac's analysis of the significant second warming which has effectively to quote "knocked out the sister vortex over the Hudson Bay and will cause the NAO to go strongly negative". In simple terms this means that the Canadian lobe of the vortex will be more or less destroyed (as will be seen in the later charts below) and the remaining fragments are being pushed away across the Arctic. I have also seen the comments from a number of the strat specialists that the record strength SSW and the further warming will extend into the "final warming" which normally occurs as we move into Spring (in March/April but can be a few weeks earlier or later). This means that the PV will not reform until towards next winter. Assuming that this is correct (and I have absolutely no reason to doubt it) then the wind reversal will continue for an extended period and HLB patterns will be maintained for many weeks as reflected in a strongly negative AO (Arctic Oscillation) from later this week and the Atlantic will be blocked with LPs making little of no progress against the HP block and being forced much further south as reflected in the NAO (North Atlantic Oscillation) about to go strongly negative too.

    The current pressure chart shows that strong Canadian lobe right now. The jet stream is already starting to buckle, looping around the north of the building Atlantic HP. The stronger streak pushing out of North America is already bending southeastwards. There is a fairly strong southern arm pushing though North Africa and well south of the Mediterranean. This is already a classic set up with the jet pushing LPs well to the south and on a nice clean and direct route. This should prevent any chance of an LP stalling and moving up through France and introducing winds from a more southerly quarter. Meanwhile the Atlantic HP is ridging strongly right up into the high Arctic. This in turn links up to the belt of HP already established over north-east Russia and Siberia. This pattern is now primed to evolve into a much greater area of HP which will become dominant and control the weather patterns in northern Asia, Russia, Europe, the UK and well beyond (as described in the next section). I included the temperature charts for general reference but I will not comment on them. I will be producing one of my Eurasian temperature and snow cover reports tomorrow with current sea surface temps and dew points too.   

    A WEEK FROM NOW:  

    Now let's have a look at what the 12z model output is telling us for the end of week 1. To keep this as brief as possible, I'll only compare GFS and ECM output. I know that there has been some very good output (for coldies) from the very consistent UKMO (but that only goes to day 6) and GEM falls into the same bracket. These are the 12z T+168 charts:

      GFS:              Jet Stream                                            Surface Pressure                                               850 Temps                                              2m Surface Temps

      gfsnh-5-168.thumb.png.8d001371aa0b5eb0e51baf4201312c32.png      gfsnh-0-168.thumb.png.6383f9a602f19223c55952971782847f.png      gfsnh-1-168.thumb.png.5a18ce228d19019fbf68b0a431d4043a.png      gfsnh-9-168.thumb.png.a4bf38f1e7b151b074230cb6fee7383e.png           

     ECM      Surface Pressure                                               850 Temps           

      ECH1-168.thumb.GIF.1b88c63b7809fed407e8ece52df15b64.GIF       ECH0-168.thumb.GIF.bfe18e2192c082886840a6f075193ea6.GIF  

    Note how the jet stream profile has already changed completely. It has generally weakened and the northern arm is almost non existent. There is a small streak pushing south-westwards out of Scandinavian (part of the pattern reversal). All the energy is now in the southern arm which powers even further south through North Africa. There is a minor loop through France which is not entirely logical and may be part of the later GFS divergence later on (I'll return to this in a minute). GFS has completely smashed the Canadian PV lobe and it has been replaced by strong HP. The remains of the vortex are shifting across the North Pole on the way towards Siberia. The HP has built powerfully across form Siberia, through northern Scandinavia, onwards through Iceland and extending all the way into Greenland. The strong easterly has been established. Meanwhile, there is LP east of the Azores. There is also a small LP running south-westwards out of Scandinavia in the easterly flow (this type of minor feature as well as troughs and other disturbances cannot be accurately forecast a week in advance). It is dragging in some very low uppers and deeper surface cold behind it but this cold pool is moving our way anyway. Plenty of snow on that chart! 

    The ECM output for the same time is pretty similar but with subtle differences which will be important going forward. The Iceland part of the HP block is about 150 miles further south. The LP is in a similar position east of the Azores but there is a much cleaner and rather stronger easterly flow with no LPs embedded in the flow (at this stage). This stronger more direct flow is pushing the lower 850s right across the country. On this chart I would say that there may be snow showers in the south and south-east. With the flow marginally south of east, there could even be a rare Channel streamer which would produce a line of snow showers near the south coasts of Dorset, Devon and Cornwall. I moved down to Exmouth 3 years ago from Hertfordshire and other than seeing a few flakes on several occasions, we've been completely snowless.  

    INTO WEEK 2:

    Here, Ill produce the same charts for day 10, the furthest out that ECM goes:

     GFS:              Jet Stream                                             Surface Pressure                                               850 Temps                                             2m Surface Temps

     5a8de8e2f0f75_gfsnh-5-240(1).thumb.png.80527ef886d095c0223094ac89a83c48.png      5a8de8ed2d729_gfsnh-0-240(2).thumb.png.4f7808953e8c5b9a7f733846eaec9d47.png     5a8de8ea3b3c5_gfsnh-1-240(1).thumb.png.0e72907d0bb1b6cf27ffa3c474354886.png     5a8de8e68631d_gfsnh-9-240(1).thumb.png.57a45cf0174edf642a6c23ecff536c1e.png 

     ECM      Surface Pressure                                               850 Temps   

     5a8de86e3baf7_ECH1-240(1).thumb.GIF.36270b6d1f3b7eb4707770beb3cd7257.GIF      ECH0-240.thumb.GIF.389cbbeb8cbc9c1f81947aff206e8fbb.GIF 

    The GFS shows a slightly changed jet stream profile. Most of the energy continues in the southern arm but there is a strange breakaway branch pushing into the UK. What on earth is the GFS reading here? They are trying to push the pattern northwards. They have mixed out the very cold uppers over western and central Europe and pushed the lowest values in northern Europe and Scandinavia. I have a theory for this. We know that the models find it difficult to cope with the impacts and pattern changes associated with an SSW and full wind reversal. GFS is trying to bring the Atlantic back in as if this was a temporary blocked pattern. This is definitely not the case. The Arctic pattern is still in full reverse flow mode and is unlikely to change back any time soon (perhaps not at all if the strat SSW and second warming merge into the final warming). This will maintain the blocked pattern. Yes the block will shift around slightly and the flow might back to northerly at times but the dominant pattern will continue to be from an easterly quarter. There is nothing to push the jet through the UK and the Atlantic will also remain relatively blocked. One cannot rule out a more south-easterly and less cold flow at times but the main cold block is much more likely to reload after each weakening, unless or until the Arctic reversal ceases. The SSW was so strong that it is likely to maintain powerful HLB for a prolonged period. . 

    The ECM solution makes so much more sense. They do slacken off the easterly but the direction of the main flow is still north-east to south-west. The LPs around the UK are all cold ones originating from the north-east. Yes, it's possible that one of them might bring in "temporarily" less cold air from the south, more especially down here in the south-west. The 850s are still -8s to -12s and that looks like a particularly snowy period if that chart verified.

    DEEP FI - DAY 16:

    Just a brief look at how the GFS continue with the 12z run.

     GFS:               Jet Stream                                              Surface Pressure                                              850 Temps                                             2m Surface Temps

     

      5a8de8627d16c_gfsnh-5-384(2).thumb.png.beb304bfd37fe311789e5db460eb3502.png      gfsnh-0-384.thumb.png.230736f8057614c16b3f27d0d92b6c09.png      5a8de85ea8bed_gfsnh-1-384(3).thumb.png.8429aead59bddd95c265dd652990dde7.png      5a8de858de0e5_gfsnh-9-384(3).thumb.png.7460eecaf1a8f9e0071432477891acf6.png

    They have brought the Atlantic to life again with a moderate westerly flow and uppers going into positive territory. The jet stream hardly supports this pattern accept that there is a kink in the southerly track which brings a loop into the UK. It might even be that GFS shifts the pattern back southwards again later on but that doesn't explain their very progressive or completely wrong attempt to bring the Atlantic back to life. The last strong SSW impact was in March 2013. Quite a different build up with it being triggered in January and no two events will have exactly the same impacts and timings. The pattern went into full reversal back then too and that lasted for 6 weeks despite the deeper cold starting some two weeks later (around March 10th). let's now see how GFS handled that one with actual archived charts and GFS archived predictions:

    GFS Archive Charts T+ 240 Forecasts, 10 days out: 

                   For March 10th 2013                                   For March 10th  2013                                      For March 20th 2013                                  For March 20th 2013

     gfsnh-2013022812-0-240.thumb.png.36f3107bafbe95175258beae46f88876.png      gfsnh-2013022812-1-240.thumb.png.86ffcf27dda722bf4642eb25b460b8b0.png       gfsnh-2013031012-0-240.thumb.png.573bfdb2f8a634aceeed1f5f60a5b993.png       gfsnh-2013031012-1-240.thumb.png.84be20bb4658de9bc25fa0b24c1bcca2.png

                  For March 30th 2013                                   For March 30th  2013                                      For April 9th 2013                                       For April 9th 2013

     gfsnh-2013032012-0-240.thumb.png.13c947fe2799ed7d0be9a1c810c5549c.png      gfsnh-2013032012-1-240.thumb.png.c9f19e16886d0796dbe4657434ebebee.png       gfsnh-2013033012-0-240.thumb.png.9e4cf5072ed88e57f4e6301da504db18.png       gfsnh-2013033012-1-240.thumb.png.1dbfa629932f756b3216b8492e6136f5.png

    NCEP Re-Analysis Actual Archived Charts:

               Actual March 10th 2013                               Actual March 10th  2013                                Actual March 20th 2013                                Actual March 20th 2013

     archivesnh-2013-3-10-12-0.png      archivesnh-2013-3-10-12-1.png       archivesnh-2013-3-20-0-0.png       archivesnh-2013-3-20-12-1.png

               Actual March 30th 2013                                 Actual March 30th  2013                                Actual April 9th 2013                                  Actual April 9th 2013

     archivesnh-2013-3-30-0-0.png       archivesnh-2013-3-30-12-1.png      archivesnh-2013-4-9-0-0.png       archivesnh-2013-4-9-0-1.png

    Gosh, this was a trickier exercise than I imagined it would be. I'm afraid that you'll need to scroll back and forth to make the comparisons but I'll summarise the differences now. The GFS archive charts with their forecasts 10 days in advance are shown in the top two rows and then the actual charts for those same dates are shown in the bottom two rows. As you can see, there are considerable differences. The actual chart for March 10th 2013 has the easterly flow well established with -12c 850s flooding in. The forecast was for southerlies and +4c 850s. By March 20th the actual and forecast charts are a little closer with easterlies over the UK but the forecast had a stronger vortex remaining whereas the actual chart shows it broken up. The forecast had lower 850s for the UK than actually transpired. By March 30th GFS forecast had started to bring the Atlantic back in but that never happened - doesn'tthis problem seems very familiar!  The forecast 850s were over +4c but the actual values were sub -8s! By April 9th, the forecast was for LP just starting to bring in milder south-westerlies but the actual charts shows east-south-easterlies! The forecast was for 0c to -2c 850s but the actual was -4c to -6c (a little closer).

    Overall, this exercise was highly worthwhile. It shows that the GFS constantly wanted to warm things up and bring the Atlantic back in but that never materialsed during the entire 6 weeks. Despite their model being updated, I feel that they sinply have not learnt any lessons and still do not factor in flow reversals. Now with all this evidence I hope that many of those who are worried about the longevity of the cold spell being cut short should not look at the GFS in the extended period. So far, most of the other models seem to be doing a rather better job but in fairness to the GFS, the others do not go up to day 16. So, let's just use the day 10 charts as the evidence. 

    That's more than enough from me for now. I'll do one of my Eurasia temperature and snow cover profiles tomorrow (or Friday). 

    EDIT:  I'm afraid that the white "run through" arrows for the charts are not appearing. Not enough editing time to change these now. I apologise for the inconvenience and will copy charts in a different way next time.

    Edited by Guest
    Correct typos and check charts
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  • Location: Napton on the Hill Warwickshire 500ft
  • Weather Preferences: Snow and heatwave
  • Location: Napton on the Hill Warwickshire 500ft
    50 minutes ago, Robbie Garrett said:

    It's been a very long time since I model watched.  But does the GFS still have a westerly bias?  It's always defaulting to Zonal in fantasy island.

    Defaulting to a westerly ?? long live the westerly bias

    T168 FI

    Netweather GFS Image

    T240 GFS FI

    Netweather GFS Image

     

     

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    Message added by Paul

    Please only post model discussion in this thread 

    For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
    https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

    For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
    https://www.netweather.tv/forum/forum/142-regional-discussions/

    We also have a special post SSW cold spell discussion open here:
    https://www.netweather.tv/forum/topic/89358-ssw-related-cold-spell-will-it-wont-it/

    Thank you!

    Guest
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