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Model Output Discussion - Staying cold into the new year


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Posted
  • Location: Home: Chingford, London (NE). Work: London (Central)
  • Location: Home: Chingford, London (NE). Work: London (Central)
    1 minute ago, bluearmy said:

    Day 10

    Yes and no ..... there is only one model from top to bottom.  So it’s modelling the reversal and then goes on to model the remainder of the run.  That’s the no part. The yes part relates to the fact that models don’t deal with reversals too well as they don’t happen v often so as the run progresses, it’s likely to be even less reliable than usual. (Which isn’t great anyway) 

    But the reversal hasn’t actually happened yet as far as I’m aware? Wouldn’t we expect further changes in the model output on how this impacts the trop once the reversal has occurred? 

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    I’m still concentrating on trends with the NH profile after day 5 and all is still good. Even before the expected cold shot I was always convinced an SSW would occur despite some reservations from a n

    I have a bit of an update from the Central European team of forecasting experts. Their charts currently show a strong alignment to the UKMO at 144t.  Looking a head for period 144t -240 they expect a

    If you’ve got a point for a specific member then I suggest you use the PM function. No need to be snippy tonight, I’ve got gin to drink and I’d prefer to not have to referee playground antics in

    Posted Images

    Posted
  • Location: st albans
  • Location: st albans
    6 minutes ago, Kentspur said:

    Is that last image a long fetched Siberian flow from the NE? Beast?

    The model does show a push of low temps west between days 12 and 30 which make it as far as scandi and e Europe 

     

    2 minutes ago, danm said:

    But the reversal hasn’t actually happened yet as far as I’m aware? Wouldn’t we expect further changes in the model output on how this impacts the trop once the reversal has occurred? 

    we used to see an obvious change in the output once the starting data included the reversed flow but this was in a time when many models didn’t actually go as high as 1 hpa and had few modelling  layers in the upper strat.  The upgraded models we have now all go to the top of the strat and once the warming has actually begun up top (which it has now) then we should expect the model to do a good job. The actual reversal at 1 hpa is due to kick in tomorrow so if we see a discernible change in the output on Saturdays 00z runs then we’ll know why!  

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    37 minutes ago, bluearmy said:

    As shown above, too many clusters to get worked up over ...... just need patience until the output settles down .....we have a broad evolution but the envelope way too wide 

    the extended period continues to show a relaxation of the cold but I’m way off being convinced that the onset of a reversal is a time for putting much analysis into output two weeks away .......

    Quick question from a novice - is the icelandic shortwave @ECM216 nailed on to drop down, regardless of how far it goes n/s & e/w? Also, is it possible for the shortwave to drop favourably for us so that the eastern flow from Russia through Scandi can link up with Greenland heights? Tia

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    Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
    19 minutes ago, Weathizard said:

    Doesn’t downwelling start a while before the actual SSW event? There’s a few very good long posts on some other threads about it.

    I think the point most are making is, ensemble suites are fickle at the best of times, let alone when we have such an unusual NH pattern and stratospheric warming occurring.
     

    It does. But this year is so so different. We have the mid strat being put under so much pressure from both top and bottom. Lots of uncertainty in the trop output until how a subsequent possible split follows the displacement. 

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    Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
    1 minute ago, Cavehill Snow said:

    Quick question from a novice - is the icelandic shortwave @ECM216 nailed on to drop down, regardless of how far it goes n/s & e/w? Also, is it possible for the shortwave to drop favourably for us so that the eastern flow from Russia through Scandi can link up with Greenland heights? Tia

    Anything at +216 isn’t nailed to occur anyway so trends and ensembles are the key here.

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    Posted
  • Location: Home: Chingford, London (NE). Work: London (Central)
  • Location: Home: Chingford, London (NE). Work: London (Central)
    12 minutes ago, bluearmy said:

    The model does show a push of low temps west between days 12 and 30 which make it as far as scandi and e Europe 

     

    we used to see an obvious change in the output once the starting data included the reversed flow but this was in a time when many models didn’t actually go as high as 1 hpa and had few modelling  layers in the upper strat.  The upgraded models we have now all go to the top of the strat and once the warming has actually begun up top (which it has now) then we should expect the model to do a good job. The actual reversal at 1 hpa is due to kick in tomorrow so if we see a discernible change in the output on Saturdays 00z runs then we’ll know why!  

    Thank you!

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    Posted
  • Location: st albans
  • Location: st albans
    5 minutes ago, chionomaniac said:

    Anything at +216 isn’t nailed to occur anyway so trends and ensembles are the key here.

    Although we have seen two instances of troughs dropping from that area into nw Europe in December. Another one is surely the form horse .....the ens support the evolution but how far south and at which longitude is the issue now imo. 

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    Posted
  • Location: frogmore south devon
  • Location: frogmore south devon
    4 minutes ago, Steve Murr said:

    you dont need me anymore 😀😀

    oh yes we do still waiting for that Boom 

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    Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
    Just now, bluearmy said:

    Although we have seen two instances of troughs dropping from that area into nw Europe in December. Another one is surely the form horse .....the ens support the evolution but how far south and at which longitude is the issue now imo. 

    I agree, but at that timeframe the form house has to have negotiated two rounds of fences and still has another jump before finishing off in the home straight lol. 

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    Posted
  • Location: Hoyland,barnsley,south yorkshire(100m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(100m asl)

    Oooooh!,....the..

    s-l640.thumb.jpg.67625eadb91b56e3a4c64e4765a4dee3.jpg

    ...are playing havoc with the models😁

    look at the heights gaining south of Greenland.

    18z v's 12z

    iconnh-0-108.thumb.png.db0c59c50c7faa9df29904cb93e0285e.pngiconnh-0-114.thumb.png.6717a24b93feb21534e25ce02f7b7b73.png

     

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    Posted
  • Location: Coventry
  • Location: Coventry
    4 minutes ago, sheikhy said:

    Steve just look at the difference of the flow at 102 hours compared to the 12z!!!

    Hey 2 posts about icon before I could get there ! I think the 12z had a malfunction, 18z much better with the heights further north and better alignment like the other models. Shame it only goes to 120

    Edited by Battleground Snow
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    Posted
  • Location: Leicester
  • Location: Leicester
    1 minute ago, Battleground Snow said:

    Hey 2 posts about icon before I could get there ! I think the 12z had a malfunction, 18z much better with the heights further north and better alignment like the other models. Shame it only goes to 120

    Waiting for that kinky chart of yours from the gfs 66 hour chart in a while!!dont let me down😜

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    Posted
  • Location: East Ham, London
  • Location: East Ham, London

    Evening all 🙂

    First, a Happy New Year to everyone on the thread and across NW especially the long-suffering Mods with whom, as you can see, I am shamelessly trying to curry favour.

    Cold and still here in lowland East London with a maximum of 2c and a number of locations in the south-east had an ice day.

    Last evening, there was a lot of uncertainty in the output especially from T+144 to T+240 so let's see if any of this has been resolved.

    12Z GEM: T+120 tonight takes us to next Tuesday. Between a slack area of LP over Northern Italy and a ridge of HP from the Atlantic across northern Scotland to Scandinavia, an E''ly airflow covers much of the British Isles. As we are told these days, uppers mean nothing and we should be looking at dew points. Despite that, 850s are -4 to -8 generally. From there, a new LP develops to the north of Iceland and starts to move SSE toward the British isles as the HP splits with one lobe setting into the Atlantic. The new LP looks to be phasing with the residual trough over the Ukraine. Shortwaves over France but the Atlantic LP extends a ridge while the Atlantic LP is near the Canaries. Perhaps some slightly less cold air moving in from the north-west. Moving on and the LP moves south over western parts of Britain and Ireland and then more SE to be in the Channel by T+240. An E'ly flow re-asserts across northern parts as heights build back over Iceland and Greenland. Uppers remain -4 to -8 with some colder air still lurking in the North Sea to move across northern parts. I'm sure I'll be told it's all cold rain - I don't believe it (as Mr Meldrew would say).

    image.thumb.png.9c7f9ed8ec9972d0f734be537ab0d268.pngimage.thumb.png.69f9935f5738e6fee0417a0da1af4338.pngimage.thumb.png.a7a9a45cc461b99d1ed66864cb85b5cd.png

    12Z GFS OP - well, a cold or very cold evolution from GEM to start the evening. At T+120 no surprises from GFS OP. Uppers of -8 generally. From there, as you would expect, some differences emerge. The LP develops to the north and tracks south though well to the west of the British Isles. It phases with the continental trough which moves back over the south of England and across Ireland. The airmass over the British Isles remains cold at -4 to -8 850s with a SE'ly developing over northern Britain by T+180. Heights remain to the north west and north east. From there, the LP first shifts to the south of the British Isles and then moves ENE forming, by T+240, a complex trough over Central and Northern Europe. Heights in the Atlantic but a new LP forming to the west of Iceland. 850s remain at -4 to -8 at this time. After T+240, the LP over Iceland goes nowhere and the trough begins to fill and new heights build over Scandinavia extending a ridge SW across the British Isles which would suggest a drier evolution. The Atlantic airmass is trying to push in at T+312 but the Scandinavian block is holding firm and keeping the cold air over the British Isles. Further into FI, the HP moves SW to be over the British Isles as a deep LP and a cold lobe of air sink into eastern Scandinavia. There's a hint of ridging back toward Greenland by T+384. It's milder in the south but cold air is still over the north-east with some frigid air over Scandinavia.

    image.thumb.png.de65c6145f8af44b6e4da1f5c865bf85.pngimage.thumb.png.e264631a47a8a3e42f327841064d1fe1.pngimage.thumb.png.109affdc959a353fdb7c8a6ed1be8d42.pngimage.thumb.png.436d5e86ea08bbc2fc411ad1966c441b.pngimage.thumb.png.a4f6218991b4cb7dc0c93adc5a4a3e91.png

    12Z Parallel: another cold evolution from GFS but with that reversion to milder we've seen for the last few days albeit still at the far reaches of FI. Let's see what Parallel has to offer this evening - well, at T+120 no surprises. Uppers -4 to -8. The T+120 indicates instabilities to the north of Iceland and by T+180 a new trough has formed which is moving SE towards the North Sea. Heights remain to the west and a NW'ly airflow covers much of the British Isles. There's cold air to the east and moving down from the north and north west. The evolution to T=240 gets more complex - the trough effectively splits with one section moving quickly south into Europe and forming a new major LP in the Mediterranean which keeps an East or North-East flow across southern and eastern Britain. Part of the energy remains to the north west and forms a new LP to the west of Iceland but between them a small ridge of HP stretching from the Azores through central and northern Britain to Scandinavia keeps most settled and dry. Less cold is moving into Ireland but it remains cold or very cold over most of the British Isles. The milder air moves in from the west but with heights building across Scandinavia a battle ground develops and Atlantic LP disrupt against the cold block and shift SE across southern Britain into Europe. By T+312 the uppers are telling the story with -12 850s off the east coast and positive uppers over Ireland. As often happens with these battlegrounds, neither side wins - by T+384 there is a strong anticyclone over Scandinavia and a SE'ly flow over the British Isles with the Atlantic pressure systems driven back west. The 850s are turning much colder with -12 850s crossing into eastern Britain and -16 to -20 uppers in the flow over Europe so this could be dry and frigid air.

    image.thumb.png.202915c6dd1f6ad464e45275ea591177.pngimage.thumb.png.fcca16bcc77eafc8516c1ae126f31fa7.pngimage.thumb.png.8828c84ec245430f9cc27d419b99c2c9.pngimage.thumb.png.9b0fb6c8b99e8c7bd54e7451cf04a8d4.pngimage.thumb.png.380784f17ef5d52aff58fb1f81276335.png

    12Z ECM - I have to say the Parallel looks a real winter treat for some even if there's a temporary milder incursion. On then to ECM - the T+120 is as you would expect -the profile of the heights marginally different but -8 uppers widely across the British Isles. As with other models, new LP develop to the north of Iceland and start to move south but this phases early with the European trough and remains to the north and east so the airflow over the British Isles is a NW'ly but the uppers remain -8 so still cold. From there, the LP moves south r south west and phases with the Atlantic trough - with heights now rising to the south, the wind flow shifts round to a milder W'ly direction and I wonder if we're seeing a west-based negative NAO set up developing. Milder air coming into the south but still cold to the north.

    image.thumb.png.24fff5920767a467a43fae615d2ee12a.pngimage.thumb.png.636c67b617542bcf63424473f9101a9d.pngimage.thumb.png.8000e03b484f7ce56a76737b401b47be.png

    Looking elsewhere, the 12Z Control is mostly cold throughout with milder air encroaching at the very end of FI in quite an unsettled synoptic pattern.

    As for the 10 HPA charts, 12Z Control instigates an initial split at T+78 and while the PV regains some cohesion, it is split apart by a new warming in FI and by T+384 is in fragments. It's a similar evolution on the Parallel which begins the split at T+60 while the OP is much the same.

    Conclusion: with the notable exception of ECM (which could be an outlier), another very strong evening's output for cold fans. The Parallel offers a huge promise of some really frigid air for mid month if we can get the Scandinavian HP in place (always a better bet for longer term cold than a Greenland HP). There's a lot of uncertainty into FI as you would expect - the extent to which that is being driven by events in the strat I don't know but the split now looks on at 10 HPA and I leave those with greater expertise than me to determine the speed of downwelling and the impact. The west-based negative NAO remains a concern but the overall picture remains cold and we're seeing from GFS the possibility that might develop similar to other recent fast downwellings in terms of allowing frigid air to transfer west from Siberia towards Europe. The times they remain interesting.

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    Posted
  • Location: Hoyland,barnsley,south yorkshire(100m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(100m asl)

    The 18z ICON finishes in line with the other models at 120.

    iconnh-0-120.thumb.png.6ccc07865d8f3bef03bf92c2280d9947.png

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    Posted
  • Location: swansea craig cefn parc 160 m asl
  • Location: swansea craig cefn parc 160 m asl
    51 minutes ago, danm said:

    But the reversal hasn’t actually happened yet as far as I’m aware? Wouldn’t we expect further changes in the model output on how this impacts the trop once the reversal has occurred? 

    The reversal is under way by the end of of next week the models will settle down,By the 12th January a total split and a total demise the strat votex, exciting times ahead.!

    Edited by keithlucky
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    Posted
  • Location: Staffordshire moorlands 252m asl
  • Weather Preferences: Frosty and fresh
  • Location: Staffordshire moorlands 252m asl

    First off wishing all a happy, illness free and peacefull new year.

    None of us have a crystal ball nore a time machine to hand so take what ever this winter has to offer in the form of it was better than last year by a country mile and enjoy the up's any many downs of model watching. 

    I still have high hopes of a memorable winter ahead.

    Roy

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    Posted
  • Location: Hoyland,barnsley,south yorkshire(100m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(100m asl)

    I had to bring out  @Mark wheeler's pet the mighty NAVGEM😏...

    navgemnh-0-180.thumb.png.7ecfbe66b70dc60a475b810e99842eca.png

    it make less fuss of that trough coming down from the north so it should disrupt favorably if that where the outcome come tomorrow.

    18z gfs rolling out now for the final time in 2020

    and i would like to wish everyone here in this thread and across the board at NW a Happy New Year,..a toast🍷🍻☺️

                                                                                                 

                                                                                                         happy-new-year-2021-wishes-card-gif_6c94bc395.thumb.gif.3e864ac3ea354e1fbdb2ee93a208cd0a.gif

    Edited by Allseasons-si
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    Posted
  • Location: Home: Nr Malton, Howardian Hills 53m asl Work: North York Moors
  • Weather Preferences: Snow/Thunderstorms
  • Location: Home: Nr Malton, Howardian Hills 53m asl Work: North York Moors

    Anyone know if there is an 18z GFS this evening? A night off maybe?

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    Message added by Paul,

    Please stick to discussing the model output in this thread. For more general chat , please use the winter/cold weather/snow chat, banter, moans and ramps thread

    For local cold/snow and weather related chat, please head over to the Regional Area.

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