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Model thread discussion - cold spell looming


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Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl
    1 hour ago, Cavehill Snow said:

    Blue mentioned the jet stream charts earlier so. Normally when it is posted there is either one or two main arms around the globe. How rare (or not) is the current pattern and what has caused it? TIA

    That meteoceil  chart i posted earlier does look complicated for sure.I think it shows every piece of the split northern arm.

    If we look at the NW view at t 144 on the GFS it looks more like we are used to.We can see there is enough energy over the top of the ridge to keep a lid on it getting too far north. 

    761866408_viewimage(7).thumb.png.2da96bcbde9e9cfd7146cdbaae8cfb52.png

    The main thrust of the jet is across to the south but frustratingly we see that cut off energy to the north just where it stops further amplification.

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    Whilst some are looking W at the low pressure for a possible snowy breakdown. Im looking in the other direction. Could it be that no fronts will get anywhere near at the end of the week (except S

    Wow, it only took GFS one suite to catch up! Wasn't expecting that. This has to be the best period of model watching in the 15 years I've been doing it.

    This is the moment for me when the action really begins. The cold pattern was secured days ago, but only now are we close enough to start forecasting the snow with any confidence. 5 or 6 days with pot

    Posted Images

    2 minutes ago, phil nw. said:

    That meteoceil  chart i posted earlier does look complicated for sure.I think it shows every piece of the split northern arm.

    If we look at the NW view at t 144 on the GFS it looks more like we are used to.We can see there is enough energy over the top of the ridge to keep a lid on it getting too far north. 

    761866408_viewimage(7).thumb.png.2da96bcbde9e9cfd7146cdbaae8cfb52.png

    The main thrust of the jet is across to the south but frustratingly we see that cut off energy to the north just where it stops further amplification.

    Thats for the alternative chart and the explanation - i can now make sense of why the ridge doesn't build. Thanks

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    Posted
  • Location: Tweeddale 145m
  • Location: Tweeddale 145m
    20 minutes ago, PolarWarsaw said:

    Bone dry and uncomfortably cold in an environment that screams 'snow event' - but couldn't be any less from delivering such at the surface.

    A gigantic dig in the ribs as far as we should all be concerned.

    The coldest uppers of the winter over our heads for 4/5 days and nothing....

    Nothing? LOL.

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    Posted
  • Location: South Staffordshire
  • Weather Preferences: Snow
  • Location: South Staffordshire
    1 minute ago, Gadje said:

    Nothing? LOL.

    From tomorrow yeah - it looks dry and cold for 90% of the country, even more so than what we have seen up to now. 

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

    Evening all 🙂

    Another bitter day here in lowland East London but I'm not sure if it was an ice day - certainly if we made it to zero we weren't there for long. Occasional mainly light snow but the increasing wind and evaporation has already got to work on the lying snow though with some frigid air due in the next 48 hours I suspect it will be an icy mass that takes us into the weekend.

    Plenty of signs last evening, after a stellar set of charts on Sunday evening, of the writing on the wall for the current cold spell by next Sunday but that will be 7-8 days of significant cold so nothing to sniff at in any sense. Are there any signs of a flip back to cold this evening? I suspect not given the number of pages on this thread but we'll see.

    T+120 takes us to Sunday 14th 😍, T+240 to the 19th, T+312 to the 22nd and T+384 to the 25th February.

    12Z GEM: by T=120 pressure remains high to the east but is now oriented north-south with a ridge into Scandinavia allowing a SW'ly air flow to edge across the British Isles though the main Atlantic LP is centred far to the west and north west near to south west Iceland. Milder air with positive uppers has reached much of the British Isles but colder air with 850s negative to -4 persists over northern Scotland. From there, the Scandinavian HP declines south to eastern Europe but the first trough fills to the north of the British isles and a new pulse of PV energy comes out of North America and is passing the south of Greenland by T+180. Weak heights to the south lead to a broad WSW'ly air flow. Behind the cold front, PM air has brought some lower 850s which are just negative over the whole of the British Isles by T+180. Moving on and the new Atlantic LP slows and re-orients in mid-ocean trying to dip south and encouraging heights to rise over mainland Europe with a large HP centred over Romania and the Black Sea by T+240. With a secondary LP zipping close to north west Scotland by this time there's a mild or very mild SW'ly air flow over the British Isles. 850s either aide of zero but with +4 uppers over southern England. 

    image.thumb.png.8df0e2d17f33d8f552cab7bbf69a4bcb.pngimage.thumb.png.51f008c025d1ae255ecb69e9ffd8615d.pngimage.thumb.png.6542baa7224b82ee8fb8bc3713f90005.png

    GEM quickly goes mild and stays mild - it's been the least enthusiastic of the models over this cold spell but to be fair it was the first to call the end so some kudos.

    12Z GFS OP - by T+120, the milder air is still battling to get across the British Isles with a large HP still to the east and the Atlantic LP oriented negatively on GFS OP rather than positively on GEM. Winds over the British Isles are still SE in the east and have turned south west in the west. 850s remain negative over all but the far west - generally below -4 over eastern areas so one more cold day it would seem. From there, the HP to the east is stubbornly persistent and by T+180 is still in situ having edged only fractionally east and it is the original Atlantic trough which has disrupted to the west but a new storm is moving off North America at T+180 as a ridge develops to the west of the British Isles. Positive uppers cover most of the British Isles by this time. From there, the Scandinavian HP declines south but maintains a ridge back into Scandinavia and the Atlantic remains held well to the west at T+240. 850s remain positive over most parts by T+240.

    image.thumb.png.47964c752470d6860a8b324c38cd0a43.pngimage.thumb.png.121721f69758bd13f1de9d23f35d3cae.pngimage.thumb.png.670995dbc4315ad825067019003e8db7.png

    No sign of an Atlantic onslaught on the GFS OP - indeed, the HP remains close by and it's actually quite a benign evolution to something more settled. 

    12Z Control: T+120 is similar to OP though I note the more defined heights over Iberia. There's not a huge amount of difference at T+180 either with the Atlantic trough trying to send energy North east through Iceland as the HP starts to decline south. One main difference is the shallow LP in the south western approaches which is more defined than on OP. By T+240 the HP is centred over the central Mediterranean but the Atlantic remains sluggish. Mild with positive uppers over the whole of the British Isles by this time. 

    image.thumb.png.96927cec5384f63dbe62d0985c6d8eb1.pngimage.thumb.png.666eceabfa411328124bfc505c128ead.pngimage.thumb.png.012573152e6f3b1626e6c80c11edd7ad.png

    12Z ECM: the most interesting of the evolutions on offer last night but let's see if it's a trendsetter or back following the herd. By T+120 it looks more progressive than GFS OP and Control in breaking down the block and positive uppers have reached all parts except north-east Scotland. From there, a major storm is spawned in the circulation of the trough and that runs NNE in mid ocean deepening considerably. Downstream, heights are rising over Iberia and the HP is over Belarus rather than sinking south as on other models. Slightly surprisingly, the 850s over the British isles are just negative with another push of milder air approaching from the south west. From there, the HP is over Belarus and the Ukraine by T+240 with a ridge into Scandinavia and the Atlantic LP systems remain held well to the west . Positive uppers over most of the British Isles by this time with any colder air well to the east and south east.

    image.thumb.png.d7e85d96ffe9e3f29a133f939da2be06.pngimage.thumb.png.e75360c7ce0fea7bc7b0c2686b780f62.pngimage.thumb.png.9946f22883d1048ff147d6a89c69663a.png

    All a bit meh from ECM - it's a different evolution but the net effect is much the same - HP somewhere over Europe and LP out in the Atlantic which equals SW'ly winds for the British Isles and mild air.

    Looking further ahead, GFS OP and Control from T+312 and T+384 respectively:

    image.thumb.png.9e352376319e42aa8e670fca911ca40d.pngimage.thumb.png.e6902396792cc43b4ca5a0ac047fa9c8.png

    image.thumb.png.2468c8badb4f40db6dcecbe84aac4a28.pngimage.thumb.png.e77b5a3909b4f4bfcf67c9c7ac753ae4.png

    Control is Atlantic-driven and boring but OP teases with a new push of heights from the NE down into Scandinavia - the cold air gets close to the British Isles but not close enough this time but it's one to watch for the next amplification. 

    Conclusion: it's clearly game over for the current cold spell despite the promise of just 48 hours ago. If GFS is right, we might squeeze out one more cold day on Sunday but otherwise the milder air marches in and that's that. No sign of an immediate return to cold on any of the models and the more likely evolution looks to be mild and benign with HP not too far by but in the wrong position to send over any colder air. The Atlantic isn't exactly raging either so it may be another waiting game until the next opportunity for amplification. The PV is looking formidable now and unlikely to be of any help so it's a 10-14 day milder spell starting on Sunday at the moment. As always, the models can pick up new signals so it's not a certainty but tonight the prospects for further cold this month after this week don't look bright.    

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    Posted
  • Location: Solihull, West Midlands. - 131 m asl .
  • Weather Preferences: Sun, Snow and Storms
  • Location: Solihull, West Midlands. - 131 m asl .

    The newly formed low (short wave?) in the North Sea is I believe the reason that the mild gets back in so quickly.

    It will stop  (Block?) the High currently building into the North Sea from exerting any pressure of the incoming Atlantic low pressure down across England. With little resistance the low just piles in.

    Without the low we will be very much still in a 50:50 situation.


    MIA

    Edited by Midlands Ice Age
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    Posted
  • Location: Leicester
  • Location: Leicester
    2 minutes ago, Midlands Ice Age said:

    The newly formed low (short wave?) in the North Sea is I believe the reason that the mild gets back in so quickly.

    It will stop  (Block?) the High currently building into the North Sea from exerting any pressure of the incoming Atlantic low pressure down across England. With little resistance the low just piles in.

    Without the low we will be very much still in a 50:50 situation.


    MIA

    Bang on mate!!!!!also the high was tipping more towards scandi and the low underneath was being thrown towards uk!!!now that same low just stays where it is and high pressure sinks south!!

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    Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl

    ECM does bring the Atlantic through without much of a fuss really.Some warm up looks inevitable by day 7 on this run as the winds swing to the sw.

    627415989_ECH1-168(1).thumb.gif.ce4fc0cb2433e6e1362f16f13849fa49.gif

    Usually by that stage it would be game over but it keeps trying to re-amplify the block further on.Something for coldies to cling on to but it looks increasingly likely we will see at least a temporary break in the cold.

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    Posted
  • Location: CARDIFF
  • Location: CARDIFF

    For me its not the low thats the problem, the Azores high ridges to try to join up with the Scandi high. That blocks the jet Stream.

    Without that we may have had a corridor allowing slider lows. So close but no cigar for Far South and West UK.

    Little bit envious of those on the East UK

     

    Then we have possibility that the Scandi high moves South East. I am guilty of relying on the MJO phase to hold the high in position, and eventually travel westwards, but other drivers overcome the lagged effect of MJO, but for how long?

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    Posted
  • Location: Suffolk
  • Weather Preferences: Snow,snow,snow and if not erm....SNOW
  • Location: Suffolk

    Well can't complain here on the Norfolk Suffolk border, decent spell and snowing again as I type! Looking ahead :-

     

    image.thumb.png.af815e257b322f208b2a5d552eb004eb.png  = Long johns 🥶

    image.thumb.png.35e55d69e5bd558ee64b24c7ca0b9bcf.png = Budgie smugglers 😎......Maybe not just yet!

     

     

     

     

    image.png < Random, can't get rid of the bugger!

    Edited by Snowmut
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    Posted
  • Location: Silver Hill, Salehurst, East Sussex. 110m asl
  • Location: Silver Hill, Salehurst, East Sussex. 110m asl

    Met O moving towards mild. Petagna on twitter.

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    Posted
  • Location: Raynes Park, London SW20
  • Location: Raynes Park, London SW20

    Mean ext EPS paints a benign and rather mild picture with high pressure dominant.

    Edited by mulzy
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    Posted
  • Location: bingley,west yorks.81 absl
  • Location: bingley,west yorks.81 absl
    Just now, Ackkers said:

    Met O moving towards mild. Petagna on twitter.

    Took their time lol.

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    Posted
  • Location: Exeter, Devon, UK. alt 10m asl
  • Location: Exeter, Devon, UK. alt 10m asl
    2 hours ago, StingJet said:

    Just an observation on the Fax charts .. a little bizarre , and I cannot recall ever seeing LP @ 1026MB ... thoughts?

    image.thumb.png.f4d25dd417b62a8ab132dfc01bdbed78.png

     

    1 hour ago, knocker said:

    It is technically a low if the pressure immediately around it is higher. ...i.e. 1028mb

    Hi Knocker - can this be a very shallow/surface feature and not even involve any circulation, or rising of the air mass through the whole troposphere?  

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    Posted
  • Location: Coney Hall Village 260ft asl, North West Kent
  • Location: Coney Hall Village 260ft asl, North West Kent
    1 hour ago, chris55 said:

    No one needs to explain sublimation or city warming to the ECM raw data.... that is what the MET office/pros/us lot do.....interpret the raw data!

     

     Looks like some snow for the Cotswolds once I know where Cardiff is....🤣😜

    Southampton in North London ??  I blame Storm Darcy

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    Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)
    19 minutes ago, Ackkers said:

    Met O moving towards mild. Petagna on twitter.

    And 24hrs ago he was saying the models are too progressive with pushing the block away..as were many other eminent meteorologists. They change their mind each day with the models. Could be saying something opposite again tomorrow if the models were to flip in favour of cold again...

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    Posted
  • Location: Croydon. South London. 286 ft asl
  • Weather Preferences: Thunderstorms, snow, Ice days, warm sunny days.
  • Location: Croydon. South London. 286 ft asl
    Just now, Tim Bland said:

    And 24hrs ago he was saying the models are too progressive with pushing the block away..as were many other eminent meteorologists. They change their mind each day with the models. Could be saying something opposite again tomorrow if the models were to flip in favour of cold again...

    Just as erratic as the ext EPS, then 😄

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    Posted
  • Location: Kilburn, NW London
  • Location: Kilburn, NW London

    This situation reminds me of many during the 1980s.  Day after day being told by the BBC cold will be pushed aside by the atlantic, and them a day or 2 before, it switches.

     

    The situation now from todays models could still easily switch and go full on cold.

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    Posted
  • Location: Camborne
  • Location: Camborne
    22 minutes ago, swebby said:

     

    Hi Knocker - can this be a very shallow/surface feature and not even involve any circulation, or rising of the air mass through the whole troposphere?  

    You can see it on the ecm chart and it does have a little significance at 500mb but not, I doubt, through the whole tropospere

    ecmwf-deterministic-eur-t850_mslp_prcp6hr-3037600.thumb.png.668a38a5336dc3f182a72d5e4b5dc7ab.pngecmwf-deterministic-eur-vort500_z500-3034000.thumb.png.70093384d4ff478e846ce693e3a4fb75.png

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    Posted
  • Location: Somerset
  • Location: Somerset
    14 minutes ago, Nath said:

    This situation reminds me of many during the 1980s.  Day after day being told by the BBC cold will be pushed aside by the atlantic, and them a day or 2 before, it switches.

     

    The situation now from todays models could still easily switch and go full on cold.

    Nope. 

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    Posted
  • Location: Essex, UK
  • Location: Essex, UK
    11 minutes ago, JimBob said:

    Nope. 

    Nope? I mean he isn’t wrong really.. maybe it may get less cold.. but for how long is the question? 
     

    it isn’t over until it’s happening.

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    Message added by Paul,

    It's busy right now, so please ensure you only post about the model output in this thread. 
    For local snow discussion and will it snow posts, please use the regional threads
    And for more general chat please use the chat, moans and ramps thread.
    There's now also a cold spell chat and discusison thread.

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