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Model Output Discussion - The Start Of Winter


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Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire

    Deep depression gone on the 12z!! Fi probably at 120 hours right now!!

    The LW pattern at that time frame is pretty set. Whether the wave feature phases or not is the finer detail and won't change/reflect the overall hemispheric set up. Though obviously it will potentially impact the UK on a micro scale.

    Slightly more amplified at day 7, could see a semi decent NWly.

    Edited by CreweCold
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    A few of you have asked today about rationale for the (tail-end of) UKMO latest 30-day outlook. There is, of course, a dedicated thread elsewhere for this but I'll just confirm that GloSea5 output rem

    Thanks for this Barry   You are however wrong on both counts you suggest :   1) I have explained in extended detail, as much as I am able, the progress of the patterns thus far from autumn (see firs

    Hopefully a timely interjection, but UKMO caution (again) that medium range NWP may not be adequately reflecting ultimate broadscale outcome. First tentative signs emerging, they suggest, of *possible

    Posted Images

    Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

    Fascinating developments continuing as we head deeper into the working week and beyond, as suspected.

     

    First hints of the 5th December being the first date to watch came from around the timing of my post below. 

     

    https://forum.netweather.tv/topic/81842-model-output-discussion-1200-hrs-151114/?p=3077689

     

    Well at only t+51 hours we have the NH Jet in the following position according to the GFS P 12z, which to be fair isn't anything worthy of over-scrutiny at least at first glance.

     

    post-7183-0-79293400-1417535642_thumb.pn

     

    Resulting in the following snowfall risk, yes I did just utter that "S" word, hold your horses though.

     

    post-7183-0-67929200-1417535726_thumb.pn

     

    Some 15 hours on, the snow risk remains distributed over a few parts of the UK by then but invariably only a fleeting opportunity for a few flakes blowing in the wind, generally restricted to higher elevations.

     

    post-7183-0-98691600-1417535857_thumb.pn

     

    Oddly, these synoptics are brought about oddly, by the following NH Jet positioning and are within the reliable timeframe. Note the split flows (shown in both Jet profiles) were highlighted a few days back by Chionomaniac as a phenomena to expect as we head deeper into Winter.

     

    post-7183-0-03114500-1417535945_thumb.pn

     

    More specifically from NH viewpoint, there is a general trend in developing the Arctic Blocking High signal across all model suites into week 2 of December, most pleasing to the eye for coldies, I might add. This is something I've witnessed across a great many outputs of late and I am led to believe, as it works alongside other factors in the stratosphere it may aid us with moving any deep entrenched cold into our neck of the woods by mid December for example. All in deep la la land for now so let's get back to more immediate timescales.

     

    As alluded to, the blocking signal is holding firm by 1500hrs on Sunday 7th December, which is t+129 hours and is reflected in the NH Jet profile below.

     

    post-7183-0-39585500-1417536472_thumb.pn

     

    A NW air flow is affecting most parts of the UK by then and brings with it, further hope of snowfall for a lucky few.

     

    post-7183-0-78341300-1417536543_thumb.pn

     

    In fairness, Temperatures away from the various weather fronts will be nearer average if not slightly below by day and we should perhaps focus our attention on the heavier bursts of showery precipitation for any likely wintry bursts. Not forgetting these are simply ONLY risk charts, so please take them as intended by their description.

     

    I WILL END THIS APPRAISAL NOW OF THE GFS PARALLEL RUN AS YOU KNOW WHAT.  :rofl:  :wallbash: 

     

     

     

     

    epic_fail.jpg

     

     

     

     

     

    ITS ACTUALLY BASED ON THE 6Z, SORRY IT CANNOT BE ACCESSED YET ON NETWEATHER. NO MATTER THOUGH, SAME THOUGHTS WILL APPLY UNLESS SOMETHING DRASTICALLY ALTERS THE NORTHERN HEMISPHERIC PICTURE COME THE 12Z.

     

    Time for me to dive into an offline cesspit.  :fool: High Arctic Blocking signal largely remains throughout the middle to latter stages, which is a good sign for a Winter far removed from the likes of last year

    Edited by gottolovethisweather
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    Posted
  • Location: Newton in Bowland
  • Location: Newton in Bowland

    thanks for sharing that HP, well worth reading everyone and shows just how much goes into seasonal forecasting especially if you read the link given earlier to their winter forecast.

    Agree and it just shows how lucky we are to have a world renowned organisation being open to us mere mortals to ask specific questions and get such high quality honest answers.
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    Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

     

     

    I WILL END THIS APPRAISAL NOW OF THE GFS PARALLEL RUN AS YOU KNOW WHAT.  :rofl:  :wallbash: 

     

     

     

     

    epic_fail.jpg

     

     

     

     

     

    ITS ACTUALLY BASED ON THE 6Z, SORRY IT CANNOT BE ACCESSED YET ON NETWEATHER. NO MATTER THOUGH, SAME THOUGHTS WILL APPLY UNLESS SOMETHING DRASTICALLY ALTERS THE NORTHERN HEMISPHERIC PICTURE.

     

     

     

    I clearly wasn't paying attention to the boss, hence my confusion above.  :rofl:

     

    https://forum.netweather.tv/topic/81934-model-output-discussion-the-start-of-winter/?p=3079153

     

    GFS Parallel runs are delayed etc. 

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

    I clearly wasn't paying attention to the boss, hence my confusion above.  :rofl:

     

    https://forum.netweather.tv/topic/81934-model-output-discussion-the-start-of-winter/?p=3079153

     

    GFS Parallel runs are delayed etc. 

     

    so why repeat the whole blessed post?

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    Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

    Back to model output discussion I go.  :give_rose:

     

    Immediately beyond T+144 hours on the UKMO output if it went that far might be produce another reasonable attempt at something wintry for a few of us.

     

    post-7183-0-41131700-1417538907_thumb.gi

     

    Nonetheless, within the reliable, the 5th and early on during the 6th December remain watch periods for wintry synoptics over parts NW and maybe Northern England at elevation. Added to this, the period around the 8th and 9th December are likely to be others but would currently reside at the bounds of FI, hence we have no cross-model consistency in this aspect at this range. All in all, beyond the current HP ridging retrogression, in two to three days time we will witness colder surface Temperatures (5c - 7c maxes), rather than any milder ones. These conditions tending to rule the roost along with the return of some nuisance rain and gales for those regions away from higher ground. How long this particular pattern will last is anybody's guess however.

    Edited by gottolovethisweather
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    Posted
  • Location: Camborne
  • Location: Camborne

    GFS 12z FI looks a lot better with wave activity starting to pick up once again with the vortex being stretched. Easterly incoming last few frames with some WAA right into the Arctic. We need to see more of this over the next week or so!

     

    I believe there was WAA yesterday from the east coast of Greenland into the Arctic. The  warm air flow rode up over the East Coast of Greenland,  over the ocean-facing cliffs of the Zachariae Glacier. pushing temperatures to almost above freezing, which to say the least, is unusual.

    Edited by knocker
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    Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

    The GFS is cold throughout it's run, we also start to get a block to our NE again with the Azores moving SE of the UK. Some snow potential as well with -6's covering the whole of the UK and -8's for parts of Scotland at day 10. I'd take this run If I was offered it!

     

    gfsnh-1-228.png?12gfsnh-0-336.png?12gfsnh-0-384.png?12

    Edited by Barry95
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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    Some improvements so far on both GFS's caused by a better upstream pattern, we are likely to see some more volatile outputs upstream for a while. Rather than repeat the same post again for anyone interested I did a more in depth one at  Page 8, post 160 which explains a bit better why we might get perhaps a bit more interest.

     

    I should add these comments from the updated NCEP discussion are welcome:

     

    NRN AND SRN STREAM FLOWS OVER NORTH AMERICA
    SHOULD TEND TO AMPLIFY OVER TIME GIVEN THE SETTLED UPSTREAM NERN
    PACIFIC MID-UPPER LEVEL TROUGH POSITION. THIS PATTERN SHOULD
    PROVIDE SYSTEMS FOR A PROTRACTED WET PERIOD ACROSS THE NWRN US
    WITH SYSTEM APPROACH/PASSAGE AND AN EMERGING DOWNSTREAM WET
    PATTERN FROM THE E-CENTRAL TO ERN US. WHILE FLOW EVOLUTION DOES
    OFFER SOME POTENTIAL FOR SOME STREAM PHASING AND COASTAL LOWS
    FARTHER EAST...THE TIMING OF EMBEDDED SHORTWAVES IS TOO UNCERTAIN
    TO DETERMINISTICALLY DEPICT FEATURES WITH MUCH UMPH

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    Posted
  • Location: Camborne
  • Location: Camborne

    I believe there was WAA yesterday from the east coast of Greenland into the Arctic. The  warm air flow rode up over the East Coast of Greenland,  over the ocean-facing cliffs of the Zachariae Glacier. pushing temperatures to almost above freezing, which to say the least, is unusual.

     

    With reference to the above.

     

    01.png

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    Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire

    The GFS P offering something much more blocked post day 11 and it should feel very seasonal. The other thing I noticed about the run was the banal nature of the weather over in the States. I think many over there, especially in the north east

    may welcome this after the extreme cold of last winter, unless they are a coldie like me!

    Some consistency from GFS P, following on from it's post 11 day blocked 06z run. The GFS P 12z is however, much more amplified upstream than the 06z and gives a marked cold plunge down the heart of the United States.
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    Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

    With reference to the above.

     

    01.png

     

    The Arctic showed similar anomalies in October too, IIRC. Scary stuff and perhaps it does help promote the blocking scenario shown across the various NWP outputs in that part of the globe. I don't believe the PV will have a chance to act in its more usual guise this Winter, so far so good but all too complex for me to draw any further conclusions from it all. 

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    Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

    It's even colder on the GFS P, snow at low levels would certainly be possible at day 9-10

     

    gfs-1-228.png?12gfs-1-234.png?12gfs-1-240.png?12

    gfs-2-204.png?12gfs-2-216.png?12gfs-2-228.png?12

    Edited by Barry95
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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    Some consistency from GFS P, following on from it's post 11 day blocked 06z run. The GFS P 12z is however, much more amplified upstream than the 06z and gives a marked cold plunge down the heart of the United States.

    This is exactly what we want to see and good news for coldies in the UK, this isn't a PV setting up shop there as the cold will be transient in that part of the USA. In this instance because of the set up the more south the cold gets in the heart of the USA the better displacement of the Azores high downstream as this reacts to the more amplified low.

     

    The GFS P is very encouraging upto T240hrs especially as it also shows the Siberian high edging west and trough disruption near the UK.

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    Posted
  • Location: Catchgate, Durham,705ft asl
  • Location: Catchgate, Durham,705ft asl

    A few posters mentioning a possible storm event in about the 7 day time frame,and this  has been picked up by the 12z UKMO.

     

     

    Very rare for the ukmo to have such a deep low on its 144 hrs chart so certainly one to keep an eye on.

     

     

    Meanwhile the GEM completely obliterates the Polar Vortex on its 12z run.

     

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    Posted
  • Location: Peterborough
  • Weather Preferences: Snow and frost in the winter. Hot and sunny, thunderstorms in the summer.
  • Location: Peterborough

    Back to model output discussion I go.  :give_rose:

     

    Immediately beyond T+144 hours on the UKMO output if it went that far might be produce another reasonable attempt at something wintry for a few of us.

     

    attachicon.gifUKMO 12z 021214 SLP & HGT500 at t+144 - 1300hrs 081214.GIF

     

    Nonetheless, within the reliable, the 5th and early on during the 6th December remain watch periods for wintry synoptics over parts NW and maybe Northern England at elevation. Added to this, the period around the 8th and 9th December are likely to be others but would currently reside at the bounds of FI, hence we have no cross-model consistency in this aspect. All in all, beyond the current HP ridging retrogression, in two to three days time we will witness colder surface Temperatures (5c - 7c maxes), rather than any milder ones. These conditions tending to rule the roost along with the return of some nuisance rain and gales for those regions away from higher ground. How long this pattern will last is anybody's guess however.

    Well more Autumnal than wintry, that is a brewing storm with our name on it.

    All models pretty much have a deep low crossing just off the north coast of Scotland in 7/8 days time, with severe gales in the north. Accompanying this will likely be heavy rain and blizzards over higher ground.  

    Seems to fit in the general plan as we move through the MJO phases, a spell of unsettled weather developing as low pressure moves eastwards through northern Europe and developing a deep trough. The next stage we really need to see signs of seeing, a rise in pressure in the Atlantic as we move through phases 6,7 and 8. If the MJO goes back into centre (no driver force on the northern hemisphere pattern) then we could be leaving 2014 empty handed with respect to a significant cold outbreak.

    So it looks like we have two choices as we move through December, the first is we get enough amplitude from the MJO and hence develop a significant Atlantic ridge and the chain reaction with troposphere/Stratosphere occurs near the end of December, or we don't and stay stuck in a unsettled zonal pattern with only the potential for transient cooler spells on the western flank of any passing low pressure system.

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

    Some fantastic posts in here today, great reading.

    Certainly not time to panic and begin the WIO posts.

     

    ECM mean pressure ensemble anomalies were not as promising yesterday evenings concerning possible big picture developments past day 10 but they are still light years from this afternoons GFS op predicted anomalies for the same period which highlights the possibilities that it may be VERY WRONG.

    ECM/GFS

     

    EDH101-240.GIF?02-12gfsnh-12-228.png?12

     

     

    GEM is much closer to the sort of pattern we might expect if the ECM predicted anomalies were to come to fruition to though it may well be overdoing things, especially given this mornings ECM ensembles did not show such a smooth transition of low heights dropping away from Greenland/Canada and causing deep troughing into Europe with the expected height rises tot he East and strengthening of the Siberian/Russian high.

     

    GEM for the same period

     

    gemnh-0-228.png?12

     

    So I would say, don't panic!

    We know we have a period of cool zonal weather to get through which may provide some interest up North for snowfall and everywhere else for possible storminess and it will at least feel seasonal. 

    The big picture suggests that the trough (PV) associated with low heights we would usually expect to keep recharging around Western Greenland/Eastern Canada will drop south and create deep trough into Europe this could well lead to much more amplified pattern downstream than GFS is modelling which would stall low pressure likely somewhere just NW of the UK which could then disrupt SE and give us some undercut.

    Unfortunately that would not be enough on its own and this is why the prediction of the upstream pattern is so important in how things develop from around mid month and why today's reading on the possibilities and background forcing were so interesting for me.

    If we get a more amplified pattern later then we must hope that GFS idea of replenishing the Greenland PV is incorrect and that the signal within ECM ensembles for low heights to drain away from the region is correct.

    This mornings ECM was somewhere between with the deep trough and associated height rises through Russia but with too much residual energy around Greenland - this may actually be not that far off what we get which would still offer potential with WAA being forced into Arctic regions and a strengthening Siberian/Russian high but it would be a slow burner.

    That said the end result could well look like the OPI anomaly predictions with lower pressure through Northern Europe and with Arctic/Russian heights gradually extending West.

    Of course that would mean a greater chance of cold weather for the UK but it also suggest it could be relatively unsettled - all a long way out though so I will stop there.

     

    Look for ECM to show good troughing into Europe with much more significant blocking to East with hints of undercut and retrogression by day 10 but if not then check the ensemble mean anomaly charts to see if there is any movement there for better or worse.

    Edited by Mucka
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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    Looking at the GEFS theres a lot of underwhelming solutions mixed with some better ones. It's all down to low pressure amplifying over the eastern USA, the crud solutions make little of any low pressure which then means you have no trigger to retrogress the Azores high and sharpen the troughing over the UK.

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    Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

    Well more Autumnal than wintry, that is a brewing storm with our name on it.

    All models pretty much have a deep low crossing just off the north coast of Scotland in 7/8 days time, with severe gales in the north. Accompanying this will likely be heavy rain and blizzards over higher ground.  

     

     

    By autumnal, I take it you mean the storminess, which after what was one of the mildest Autumns in living memory, I'll take the blizzards and upcoming potential for snow as wintry signals, all far from anything distinctly Autumnal IMHO. It is all relative though I guess and the timeframes we are both referring to, aren't done deals with regard to actual surface conditions either just yet. They could equally produce rain or snow at that range. However my posting on the GFS P 12z (wrong run analysed) and Summer Sun's above clearly illustrate the opportunities for snowfall during the next five to seven days.  :good:

     

    As for the MJO signals, I can't pretend to understand the dynamics of such phenomena but that alone along with those other much-lauded NH pattern signals tell me that a grand ole December might be upcoming for coldies. Again all in my own humble opinion, but no complaints here at this very early juncture of the season.  :cold:

     

    The ECM 12z runs have kept the colder synoptics to the forefront in recent days, here's to them achieving this trend again tonight.  :drinks:

     

    Eyes down coldies.

    Edited by gottolovethisweather
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    Posted
  • Location: Catchgate, Durham,705ft asl
  • Location: Catchgate, Durham,705ft asl

    Huge LP from the ECM at 168 hrs,could this be a game changer,or has it just gone off one one?

     

     

     

    Looking at that chart from the closer UK view reveals a nasty looking secondary LP approaching Ireland.

     

    Edited by Cloud 10
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    Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

    ^^^ Yes the LP system further south on the ECM so we miss the colder uppers flow and/or more modified:

     

    D8 post-14819-0-78773600-1417546002_thumb.g  GFS post-14819-0-72736000-1417546014_thumb.p

     

    D9: post-14819-0-40252400-1417546189_thumb.p

     

    Not following GEM and rather flat with a TM injection of warmer uppers incoming: post-14819-0-59445300-1417546262_thumb.g

     

    Of course all likely to change tomorrow.

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