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Model Output Discussion - The Run In To Christmas


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Posted
  • Location: South Essex
  • Location: South Essex

    Looking through GEFS there is a little bit of support for height rises to our NE in the mid term, but nothing more than that. Overall they remain resolutely zonal in FI.

    That said, if the Opp runs are onto something it would take a while for the ensembles to catch on in that scenario. Its only a small chance, but its a tiny straw to clutch onto. If nothing comes of that, then it looks to me like attention moves towards mid Jan and beyond as a period of zonality looks strongly odds on IMHO.

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    Unfortunately, there needs to be a recognition that if we share at *this tentative juncture* the exact nature of what we have as Ops Centre guidance, certain individuals will inevitably extrapolate/wa

    If the UK can't get cold from an upstream pattern with a negatively tilted troughing setting up over the ne USA , indeed the best set up since two winters ago then I will seriously consider throwing m

    The good news just keeps on coming!   Upstream pattern is falling into place to deliver what many people in this thread want to see, NCEP give us the best update since winter 2012/2013,  indeed I'm

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    Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl

    Perhaps we should be looking NE in to the 10-15 day period....

     

    attachicon.gifscandihigh1.gifattachicon.gifscandihigh2.gif

     

    Split vortex and ridging tendency heading more and more towards Scandinavia over the last couple of runs

     

    SK

     

    Yes - the signal for a GH is receding. Not good news if you want a SSW in the heart of winter.... - at least a trop led one as has been suggested...

    Edited by Catacol_Highlander
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    Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

    Rather than snow I think the main concern next weekend will be the wind speeds

     

    These are the wind gusts from GFS P

     

    138-289PUK.GIF?21-6144-289PUK.GIF?21-6150-289PUK.GIF?21-6156-289PUK.GIF?21-6168-289PUK.GIF?21-6

     

    The best I can find on the snow depth charts is this

     

    156-780PUK.GIF?21-6

     

    The precipitation charts show a spell of transient snow mainly on higher levels but lower levels could see a period of snow before it turns back to rain

     

    150-574PUK.GIF?21-6150-580PUK.GIF?21-6

     

    As the year come to an end its only the higher parts of northern Scotland which have any meaningful snow

     

    240-780PUK.GIF?21-6

     

    So a spell of transient snow is possible next weekend mainly on higher ground but possibly to some lower levels for a time other than that the main concern looks to be the wind speeds which would no doubt cause some disruption

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    Posted
  • Location: Manchester
  • Location: Manchester

    It's been a long while since I can remember so many days of sustained model disagreement, and inability to get a hold on the hemispheric pattern. The last few days have seen all sorts of variations - not just on a theme, but on the theme or "pattern" itself. Note these differences this morning... GFSP at 192

     

    gfsnh-0-192.png?6

     

    and then ECM for the same timeframe

     

    ECH1-192.GIF?21-12

     

    It's like looking at 2 different worlds, bar the signal for high pressure close to the UK. European heights different, EPO ridge different, location of most vortex energy different.

     

    Frankly I dont trust anything I'm seeing at the moment. One thing is sure though - we have a pretty major wave 1 assault on the vortex underway now

     

    ecmwfzm_ha1_f192.gif

     

    But we also have strat remperatures at the pole running well below normal after a dramatic reverse earlier in December:

     

    pole30_nh.gif

     

    ... and as a result a vortex that is stronger at its core than we expected it would be, leading to an ensemble mean forecast for 3-4 weeks time from JMA that looks like this:

     

     

    Disappointing to see the stratosphere so cold again despite the recent optimism. I think the idea of a SSW in late Dec/early January has fizzled out based on what I read in the stratospheric thread in recent days. Some experts are now even pointing to the end of January for a SSW...

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    Posted
  • Location: Sowerby Bridge, West Yorkshire
  • Weather Preferences: Click on my name - sorry, it was too long to fit here......
  • Location: Sowerby Bridge, West Yorkshire

    Disappointing to see the stratosphere so cold again despite the recent optimism. I think the idea of a SSW in late Dec/early January has fizzled out based on what I read in the stratospheric thread in recent days. Some experts are now even pointing to the end of January for a SSW...

     

    It's only half of the story.

     

    http://i.imgur.com/20HOfLX.gif

     

    20HOfLX.gif

     

    Also, as per Matt Hugo in his most recent post in the strat thread "As per the up-coming warming, which is now short term, the GFS picked up on this at the beginning of the month and equally it is quite persistent now with regards to splitting the vortex essentially at the start of 2015..."

     

    It's tempting to find the most negative possible factor and keep focusing on that but a more balanced view is more helpful.

    Edited by ukpaul
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    Posted
  • Location: Sowerby Bridge, West Yorkshire
  • Weather Preferences: Click on my name - sorry, it was too long to fit here......
  • Location: Sowerby Bridge, West Yorkshire

    Also, with 10hpa potentially looking like this then, to me, the signs are there for something much more encouraging (the parallel is similar).

     

    gfsnh-10-384.png?6

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    Posted
  • Location: Sowerby Bridge, West Yorkshire
  • Weather Preferences: Click on my name - sorry, it was too long to fit here......
  • Location: Sowerby Bridge, West Yorkshire

    What do you mean?

     

    The charts are all here if you want a more comprehensive view, top to bottom and over time.

     

    http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2014122018&var=TMP&lev=30mb&hour=288

    Edited by ukpaul
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    Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl

    It's only half of the story.

     

    NH_TMP_30mb_288.gif

     

    Also, as per Matt Hugo in his most recent post in the strat thread "As per the up-coming warming, which is now short term, the GFS picked up on this at the beginning of the month and equally it is quite persistent now with regards to splitting the vortex essentially at the start of 2015..."

     

    It's tempting to find the most negative possible factor and keep focusing on that but a more balanced view is more helpful.

     

    Agreed. My post wasnt supposed to say that a SSW was now off the table.... though for the sake of the balance you ask for here I was merely pointing out that a GH is looking, on the face of it, harder to see with the output over the last few days.

     

    BUT equally the models are quite literally all over the place at the moment. This suggests a tipping point in the balance of teleconnective signals, and for me the warming that is just getting underway is the key player. Modelling of just what will happen to the vortex in the face of this assault is, I suspect, fairly key in explaining model volatility. If the attack shifts the vortex violently off its axis in such a shape/direction that it allows the EPO ridge to teleconnect properly to height rises over Greenland then we are in business. Even better if we can get a proper split - as some charts are hinting at. But the vortex is currently a bit stronger than we hoped it might be at present, and Cohen for one clearly feels that we are running a couple of weeks behind schedule in terms of pre winter guesses on the timing of a SSW.

     

    Chio is right of course - we dont need a full SSW to get good winter synoptics.... a decent vortex displacement and weakening of the westerlies can do that quit happily. But we need a more generous roll of the dice in that circumstance to secure removal of atlantic energy to allow blocking to take hold.

    Edited by Catacol_Highlander
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    Posted
  • Location: Sowerby Bridge, West Yorkshire
  • Weather Preferences: Click on my name - sorry, it was too long to fit here......
  • Location: Sowerby Bridge, West Yorkshire

    Agreed. My post wasnt supposed to say that a SSW was now off the table.... though for the sake of the balance you ask for here I was merely pointing out that a GH is looking, on the face of it, harder to see with the output over the last few days.

     

    BUT equally the models are quite literally all over the place at the moment. This suggests a tipping point in the balance of teleconnective signals, and for me the warming that is just getting underway is the key player. Modelling of just what will happen to the vortex in the face of this assault is, I suspect, fairly key in explaining model volatility. If the attack shifts the vortex violently off its axis in such a shape/direction that it allows the EPO ridge to teleconnect properly to height rises over Greenland then we are in business.But the vortex is currently a bit stronger than we hoped it might be at present, and Cohen for one clearly feels that we are running a couple of weeks behind schedule in terms of pre winter guesses on the timing of a SSW.

     

    Chio is right of course - we dont need a full SSW to get good winter synoptics.... a decent vortex displacement and weakening of the westerlies can do that quit happily. But we need a more generous roll of the dice in that circumstance to secure removal of atlantic energy to allow blocking to take hold.

     

    The GH is the conundrum at the moment for me, connected to the persistence of the Canadaian lobe of the PV, I'm not convinced by the later stages of GFS output as a result. If they are right then I can only presume that the odds of Scandi height rises are greater and, if we think that the models are all over the place now, experience tells us that it's nothing compared to them trying to work out any height rises there!

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    Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl

     

     

    Says to me the vortex is Potentially going to split all the way to the top.  This to me means that the models are certainly going to be interesting viewing especially IF this split continues to be modeled.  

     

    Agreed... but we could still do with heights over greenland in order to land the killer blow via a trop led wave 2 assault thereafter. If we dont get that - if the vortex "split" dumps one segment of the vortex over Greenland - then it is a faster route to vortex recovery.

     

    Dont get me wrong - the current pattern is the best we have seen for sustained winter synoptics for a while, but I think I speak accurately when suggesting that 95% of the posters on this thread are looking for exactly that = sustained, winter nirvana. Hence the concern at the moment. I'm still sure we will get shots of winter activity because the pattern is generally fairly amplified this year.... but maybe the long term cold from north or east may be harder to come by than was suggested a few weeks ago.

     

    Question for Roger (RJS) - you have a habit of being remarkably accurate over the years in your winter forecasts. Initially you went for a volatile on/off pattern of mild/cold throughout most of winter but then seemed to change to a much colder outlook. The retrograde prediction in December went awol.... but you seem to be sticking to a cold outlook in January. What caused the shift in the tenor of your forecast? Genuinely interested.

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    Posted
  • Location: portsmouth uk
  • Weather Preferences: extremes
  • Location: portsmouth uk

    It's been a long while since I can remember so many days of sustained model disagreement, and inability to get a hold on the hemispheric pattern. The last few days have seen all sorts of variations - not just on a theme, but on the theme or "pattern" itself. Note these differences this morning... GFSP at 192

     

    gfsnh-0-192.png?6

     

    and then ECM for the same timeframe

     

    ECH1-192.GIF?21-12

     

    It's like looking at 2 different worlds, bar the signal for high pressure close to the UK. European heights different, EPO ridge different, location of most vortex energy different.

     

    Frankly I dont trust anything I'm seeing at the moment. One thing is sure though - we have a pretty major wave 1 assault on the vortex underway now

     

    ecmwfzm_ha1_f192.gif

     

    But we also have strat remperatures at the pole running well below normal after a dramatic reverse earlier in December:

     

    pole30_nh.gif

     

    ... and as a result a vortex that is stronger at its core than we expected it would be, leading to an ensemble mean forecast for 3-4 weeks time from JMA that looks like this:

     

    Y201412.D1712.png

     

    I know that Chio is still pretty bullish on twitter about the strat forecasts, but from my more inexperienced angle we seem to be placing a lot of faith in the current wave 1 attack displacing the vortex in such a manner that it will allow heights to rise over Greenland and a consequent wave 2 attack shortly thereafter. Trouble is - the images I'm seeing this morning are not showing a consistent signal for proper height rises over Greenland, and NCEP forecast for the lower strat like this one suggest that low pressure in the atlantic will remain with us, with heights if anything sitting more over the UK in a dull omega block.

     

    gfs_z100_nh_f192.gif

     

     

    So - conclusion? The models are all over the place and nothing should be taken as gospel at the moment, but I'm less convinced than I was a week or so ago that we will get a proper GH... and this would be a fairly major blow to the idea of a trop lead wave 2 assault on the vortex with resultant wintry synoptics for Europe through January. 

    excellent post and my thoughts also i think we really are just unlucky perhaps feb will be a better month.

    vortex looks like the winner once again but if wave activity resumes possible of a knock on effect i think the polar vortex has been a little note worth than expected but still weaker than last year,

    but its regeneration during this month has been very clear to see.

     

    close but no cigar but honestly not bad futher north and perhaps with continued pm flow as depressions pass over the uk so the north looks a good place to go for wintry conditions.

    there will be some decent snowfall amounts into scotland this could well continue into jan but futher south nothing really perhaps clear frosty into jan which is a far cry from last year.....

    but ive for one have thrown in the towel for down here wintry conditions and hoping through jan were see a better set up for feb but i wont hold my breath.

     

    this year model watching has been the most edge of seat stuff.

    but its looking not as good as afew days ago and unlikely to head anywhere great for the southern half of the uk.

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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

    Don't know if I'm late to the part this morning, but the ECM long-term ensembles continue to have cold clustering after 29th for several days. I can't see more than this e.g. whether this is from a cold high, an easterly or something else, but the idea of a return to zonality looks an outsider on these, and a northerly or easterly wind direction must be preferred by most ensemble members.

    www.weathercast.co.uk/services/ensemble-forecast.html

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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    The possible elongation of the PV does open up an avenue to cold if this sets up in a favourable manner, stretched from ne USA ne'wards.

     

    That would correlate with high pressure near the UK extending towards Scandi, I think at the moment that seems the best chance for more extended cold.

     

    If the PV then splits you might retrogression towards Greenland, of course this is well into the future and best to not get our hopes up too much!

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    Posted
  • Location: st albans
  • Location: st albans

    Don't know if I'm late to the part this morning, but the ECM long-term ensembles continue to have cold clustering after 29th for several days. I can't see more than this e.g. whether this is from a cold high, an easterly or something else, but the idea of a return to zonality looks an outsider on these, and a northerly or easterly wind direction must be preferred by most ensemble members.

    www.weathercast.co.uk/services/ensemble-forecast.html

    Clearly there are clusters reflecting a cyclonic sceuro trough and also a cold high. However, as week 2 comes to a close, the more mobile runs begin to increase and the slow uptick in the mean reflects that. The direction of travel in the extended ecm 00 suite is away from blocked or amplified but that's not to say it can't swing back again although the direction of travel is away from a swing back very far.

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    Posted
  • Location: Broxbourne, Herts
  • Weather Preferences: Snow snow and snow
  • Location: Broxbourne, Herts

    For all I love coming in here to experience all the highs and lows of what the models are showing, especially when as volatile as they seem to be right now.. I have a growing sense that the real way of seeing into the FI future is through Ian Ferguson's contributions. in such a period of volatility I haven't seen him put a foot wrong so far (and I know his views are generally presented as being representative of the Meto). the post Christmas storm is not something I saw first on the models, but heard about first from something he said the Meto were keeping a close eye on at a distance from which GFS would be dismissed as way out in FI

    If they had said the PV was likely to strengthen, I'd be inclined to believe them. But of course, that's not what they've said at all!

    Edited by Timmytour
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    Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

    Unless I'm mistaken, after next weekend's wild wet spell it looks like the north and east will become cold with snow showers and frosty nights with lower heights to the NE whereas the western side of the UK should fine up as Atlantic high pressure edges closer but even the west will be cold with widespread frosts, so maybe some of us will get that rare white fluffy stuff we call snow.

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

    You're being a bit of a wind-up merchant tbh Mucka. I'm not sure of your definition of cold spell, but these two screenshots are not exactly mild now, are they? Have you checked the 850hPa temps? On the GFSP, for instance, there is a sustained cold 'spell' that lasts over a week.

     

    We're starting to see good agreement for 27/12 across GFS, GFSP, UKMO and GEM. UKMO is particularly tasty and that inspires great hope in me. I await the ECM prodigal with bemusement.

     

     

    No wind up. 

    There is no cold spell currently being modelled before end of Dec. A couple of chilly days among a few cooler days but no cold spell.

    If you and others see what is being modelled as a cold spell then your criteria are obviously different to mine which would be for much of England to have at least 4 consecutive days of temps 2 or 3c below average.

     

    Here are GFS ensembles, they do not show a "Cold spell"

     

    graphe6_1000_252_93___.gif

     

    Just the odd chilly day among some average/cool days. 

    If I was calling mild then it might be reasonable to say I was on the wind up.

     

    This forum is an odd place at times, an alternate reality.

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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 .

    As stated I am not a great fan of GFS.

     

    However, they (GFSP) did show a switch to a potentially stormy spell around Xmas the first of all the models.

     

    It was on the old thread about 14Dec, when it was t+360. It remained consistent for a couple of days, when it ejected a small low on the south east side (it wa over Belgium, I think) down towards Italy. At that point I sw the possibility of an easterly down the line.

     

    As everybody knows the GFS then dropped the bomb (as it always does!) , and it has not really been shown again until the last 18 hours.

     

    The latest GFSP 6z also shows this ejection (right word?)  down towards the Med. It is this process that makes me think we could be in for an easterly. It will break thru' the heights to our south and push the Az high up into the Atlantic to form a block to the west.

     

    I think this is the process particularly if it starts to move into the middle of the North Atlantic which will cause the signal change to our weather to a very much colder type.

     

    Now,  I am a fan of the ECM, but it has not picked up on this bomb at all yet, and only now is it beginning to think about a rapidly deepening low.It may be correct with its much slower evolution, we will probably know in the next 2 days but it will move its  version of the  low over the UK at a different angle and seems unlikely to move south as the GFSP does. But a lot can/will change between now and then. Note if it moves it to the south of the Uk via Ireland it will be VERY good for coldies. 

     

    The ECM at the moment has not even got near this evolution and so is missing this potential change.  

     

    The MO has not really concentrated its efforts on this evolution until the last 48hrs.

    It would be interesting to see what there DECIDER charts have shown during the last 3 days..

     

    They are now getting rightly concerned.

     

    MIA

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    Posted
  • Location: Redhill, Surrey
  • Weather Preferences: Southerly tracking LPs, heavy snow. Also 25c and calm
  • Location: Redhill, Surrey

    I have to say I think the GFS toying with a potential easterly down the line is a plausible way forward.  I think the idea of building heights to our NE is the place to look but whether it will have enough umph to hold and influence or get forced away I'm unsure of.  I think looking NW for strong heights to build and hold was a false/over amplification reading from the models  For me its put away for now.  In the shorter term I think this deep LP is a goer, exact timing to be confirmed but I think a stormy for most and snowy in parts period is coming and we should be prepared for that. 

    Nice to have it after then before for travelling purposes?

     

    BFTP

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    Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

    The experts are now mentioning the word stormy with increasing frequency now so it does look like we will get a battering next weekend, a stormy mix of heavy rain, severe gales and don't rule out leading edge snow as fronts bump into the newly formed cold pool covering the UK and depending on the track, all points north of the low centre could have snow since they would stay in cold air which would then be sweeping south as the low tracks away eastwards.

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    Posted
  • Location: Otley(Leeds)
  • Location: Otley(Leeds)

    No wind up. 

    There is no cold spell currently being modelled before end of Dec. A couple of chilly days among a few cooler days but no cold spell.

    If you and others see what is being modelled as a cold spell then your criteria are obviously different to mine which would be for much of England to have at least 4 consecutive days of temps 2 or 3c below average.

     

    Here are GFS ensembles, they do not show a "Cold spell"

     

    graphe6_1000_252_93___.gif

     

    Just the odd chilly day among some average/cool days. 

    If I was calling mild then it might be reasonable to say I was on the wind up.

     

    This forum is an odd place at times, an alternate reality.

     

     

     

    I would have agreed with you a couple of days ago as there was no real signs of a good block developing or weakening of the jet stream, from pretty much all the models.

     

    But now today a fair few models are hinting at more settled/blocked weather albeit not overly cold/snowy.

     

     

    Look at the GFS for example:

     

    Rtavn2041.gif

    Rtavn2042.gif

     

    Rtavn3121.gif

    Rtavn31217.gif

    Rtavn3721.gif

    Rtavn37217.gif

     

    After next weekends possible storm, blocked with cold nights, by the end of the timeframe max temps likely of 1-3C quite widely!

     

    ECM quite similar in this type of cold blocked set-up

     

    Recm1921.gif

    Recm2401.gif

     

     

    Not saying this is the specific outcome that will materialise but is certainly on the table :) So I find your last line a bit strange and harsh..

    Edited by Harsh Climate
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