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Model Output Discussion - The final stretch to Christmas


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Mean while in the real world away from the MOD... A tragic accident has cost 6 lives in Glasgow. yes this is off topic but a timely reminder of just how unimportant the weather really is in our lives.

There is an enormous lack of respect for other people in this thread at the moment. I suggest that if one doesn't have something to add to the model discussion with a salient chart or pertinent inf

Model uncertainty throwing both operational and ensemble data into discontinuity has proved as rife as was expected a week ago - when AAM flipped to negative tendency along with GWO phasing that was i

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

    Does anyone know where Knocker is, I've not seen him post in a while...

     

    For months, the Azores High was a nuisance, but like it has in the past great winters, it has actually caused all the interest now!

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    Posted
  • Location: Live Thame (Oxfordshire), Work Heathrow Airport
  • Location: Live Thame (Oxfordshire), Work Heathrow Airport

    Look at some of the below ensembles taken from an identical timeframe - something brewing?

     

     

    gensnh-18-1-216.png

     

     

     

    gensnh-9-1-216.png

     

     

     

    gensnh-7-1-216.png

     

     

     

    gensnh-5-1-216.png

     

     

     

    gensnh-8-1-216.png

     

     

     

    gensnh-19-1-216.png

     

     

    gensnh-20-1-216.png

     

    I've been in this game long enough to know that things will chop and change and quickly what seems like a trend will reverse to become obsolete within a matter of hours, but coupled with changes in the stratosphere (take a look at the Op forecast), the longstanding Meto suggestion of something colder in January and the rather sudden shift into potential Easterlies in High-Res, the options are clearly there. More interesting times afoot on this thread...

     

    To be honest, it is this chart more than anything else which has me interested:

     

    gensnh-22-1-384.png

     

     

    Basically the entire polar region has a positive height anomaly, stretching all the way across from our Mid-Lat region on one side all the way across to Alaska on the other. The options this presents us with are enormous, though still in the possibility scale rather than probability at this range. Taken together with warming up high in the strat, and this chart is the most positive from a winter weather perspective all season so far in my view. Stand to be corrected though.

    Please somebody do correct me if I am wrong but the GEFS spread you posted is not a height anomoly chart. It is for an indication in the confidence of possible outcomes. I.e the lighter the shade the less confidence (or the greater spread) in the outcome of the possibilities being shown by the ensembles in that particular area on the chart.

    Someone will be able to explain it clearer than i have though.

    Edited by No Balls Like Snow Balls
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    Posted
  • Location: Cork, Ireland.
  • Weather Preferences: Storms frost snow heatwaves
  • Location: Cork, Ireland.

    According to the pros here.. The weather for next Sunday and early next week is still in the balance. It is likely to start off cold, dry and frosty, but the Atlantic weather fronts, with a milder, windier and wetter regime, may yet return early next week. 

     

    Quite different to the stance they adopted as recently as last evening when they were quite bullish about the weather being "settled and cold" in the run up to the New Year.

     

     

    post-17830-0-47039200-1419423811_thumb.j

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    Posted
  • Location: Strood, Kent, 19 feet above sea level
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Strood, Kent, 19 feet above sea level

    Please somebody do correct me if I am wrong but the GEFS spread you posted is not a height anomoly chart. It is for an indication in the confidence of possible outcomes. I.e the lighter the shade the less confidence (or the greater spread) in the outcome of the possibilities being shown by the ensembles in that particular area on the chart.Someone will be able to explain it clearer than i have though.

    Spot on - The lighter/brighter the colours, the more solutions there are within the ensemble suite for that particular area and therefore the lower the confidence in the forecast

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    Posted
  • Location: Manchester
  • Location: Manchester

    According to the pros here.. The weather for next Sunday and early next week is still in the balance. It is likely to start off cold, dry and frosty, but the Atlantic weather fronts, with a milder, windier and wetter regime, may yet return early next week. 

     

    Quite different to the stance they adopted as recently as last evening when they were quite bullish about the weather being "settled and cold" in the run up to the New Year.

     

     

    That's indeed quite a change but I guess it is realistic as Ireland always benefits the least when there is a block to the east. One such example was February 2012 when eastern England was frozen for two weeks while Ireland was barely chilly.

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  • Location: Strood, Kent, 19 feet above sea level
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Strood, Kent, 19 feet above sea level

    PT 5 shows us exactly what needs to happen for us to get a decent cold spell out of this, and it begins as early as T84 in some respects.

     

    post-7073-0-48561500-1419424254_thumb.pn

     

    We see the high in the mid-atlantic becoming very amplified pushing up into Greenland, this is key. The more amplification we have at this early juncture the further North the high will be across the UK when it sinks South-Eastwards behind the low pressure system and then builds towards Scandi.

     

    At T156 we see low heights across Europe and a slightly elongated high sitting across the Northern UK extending up towards Iceland and Scandinavia. Look at the orientation out in the Atlantic, as a low pressure comes up against this high it's going to slide Southwards as it becomes negatively tilted and phases with the low heights over Europe.

     

    post-7073-0-69696800-1419424438_thumb.pn

     

    post-7073-0-55454100-1419424434_thumb.pn

     

    The low then slides underneath the high dragging colder air Westwards over the UK.

     

    PT 5 shows this happening perfectly. So things to watch out for in the 12z suites

     

    1. More amplification

    2. Negative tilting in the Atlantic

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    Posted
  • Location: Cambridge
  • Location: Cambridge

    Spot on - The lighter/brighter the colours, the more solutions there are within the ensemble suite for that particular area and therefore the lower the confidence in the forecast

    Apologies, I should have been clearer and said higher than usual heights - which is precisely why we have such little confidence in forecasting, and why we have so many options (some good, some bad) ahead of us. You are right the chart is not an anomaly spread, but by virtue of what that chart shows (which is low confidence on the entire polar region because so many options are countering the usual pattern of low pressure over the area), the chances of seeing a higher than average anomaly spread over the arctic is increasing. Sorry I wasn't clear before, i should have said by implication of the above chart not what the above chart shows...

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

    Looking at the ECM postage stamps still quite a lot of variation in the position of the high at T120hrs, theres only minority support there for the UKMO solution:

     

    post-1206-0-86650000-1419424651_thumb.gi

     

    Still uncertainty in terms of snowfall, some of those ensembles look more showery for the east and se, others drier for the whole of the UK.

     

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    Posted
  • Location: Live Thame (Oxfordshire), Work Heathrow Airport
  • Location: Live Thame (Oxfordshire), Work Heathrow Airport

    Apologies, I should have been clearer and said higher than usual heights - which is precisely why we have such little confidence in forecasting, and why we have so many options (some good, some bad) ahead of us. You are right the chart is not an anomaly spread, but by virtue of what that chart shows (which is low confidence on the entire polar region because so many options are countering the usual pattern of low pressure over the area), the chances of seeing a higher than average anomaly spread over the arctic is increasing. Sorry I wasn't clear before, i should have said by implication of the above chart not what the above chart shows...

    Ah now I understand. Thanks

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

    Not snowy but cold via the persistent block to our east. By the very end, we see the Atlantic trough attempting to push into nw Europe from the sw. Would imagine that will be interesting but at two weeks it won't pan out that way.

    That's very much the extended ens mean and anomoly view aswell

    edit: just checked the control uppers and they are above freezing heading through week 2 so no chance of anything white from the trough pushing in. The block centred too far south to pull in anything cold upper wise though surface cold likely

    To be fair ba it's week2 and this situation is a good possibility for block to set up East North East so couple this with the strat and pv developments this could go either way.

    Be nice just to be excited about what's coming between tomorrow and the weekend.

    Merry Christmas everyone

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

    That's indeed quite a change but I guess it is realistic as Ireland always benefits the least when there is a block to the east. One such example was February 2012 when eastern England was frozen for two weeks while Ireland was barely chilly.

    Yeah and of coarse this could well go the opposite way as I am confident it will

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    Posted
  • Location: Banbury
  • Location: Banbury

    According to the pros here.. The weather for next Sunday and early next week is still in the balance. It is likely to start off cold, dry and frosty, but the Atlantic weather fronts, with a milder, windier and wetter regime, may yet return early next week. 

     

    Quite different to the stance they adopted as recently as last evening when they were quite bullish about the weather being "settled and cold" in the run up to the New Year.

     

     

    But you are in Ireland , I think that reflects the models as they stand at the minute, but for us here in England I would say we are very much under the influence of the HP, into the N Year at least

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    Posted
  • Location: North East London (E4) 147ft
  • Location: North East London (E4) 147ft

    Merry Christmas to  all. Including the GFSo – which has finally found the Christmas spirit!

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    Posted
  • Location: Mile Oak, 3 miles West of Brighton UK, 130 Meters above sea level
  • Weather Preferences: Anything Extreme
  • Location: Mile Oak, 3 miles West of Brighton UK, 130 Meters above sea level

    Well probably the coldest XMas day forecast IMBY for many a year, and not all that cold, which just goes to show how rare a cold XMas day is down this way anyway. 

     

    I'm reluctant to believe anything the GFS shows now past +96 given that it was so bullish about sending the weekends Low East and barely modelling it to drop South, until the 11th hour (in forecasting terms). 

     

    That being said it does fall in line with what all the models are suggesting past this weekend, it would appear that we'll see more in the way of drier weather as high pressure becomes to dominant force at least for a while. 

     

    It would be nice to get a HLB over Scandinavia or better still an ''Omega Block'' , time will tell, if were still talking about the possibility of an Easterly draw on Boxing day then I'll be happy, but I expect we'll see a firming up of the High sinking, and then a period of stormy weather before our next opportunity for cold weather comes later in January. 

     

    I like how this Winter has started and I'm slowly beginning to believe that the back end of Jan and Feb in particular could deliver some noteworthy cold and snow. 

     

    Happy XMas everyone.

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    Posted
  • Location: Barling, Essex
  • Weather Preferences: Snow and Storms
  • Location: Barling, Essex

    While I get the chance I would also I would like to thank everyone on here for the there weather knowledge, reports and banter throughout the year and wish you all a very Happy Christmas and a wonderful New Year  :)  now bring on the snow please  :) :) :) 

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    Posted
  • Location: Coney Hall Village 260ft asl, North West Kent
  • Location: Coney Hall Village 260ft asl, North West Kent

    Haven't much time to analyse the charts this morning, but to be frank, without even looking at the precipitation charts if this chart can't produce heavy snow in the south east, considering the time of year, I don't know what will!

    www.meteociel.fr/modeles/gfse_cartes.php?&ech=96&mode=0&runpara=1

    if it was the height of summer, you'd know without a doubt there'd be a washout in London from that, so surely there's going to be a lot of precipitation around, if it verifies - which is a fair chance considering the timescale?

    The Easterly would perhaps bring in a Thames Streamer ??

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    Posted
  • Location: Home near Sellindge, 80m/250feet, 5miles from Coast
  • Weather Preferences: Severe Storms and Snow
  • Location: Home near Sellindge, 80m/250feet, 5miles from Coast

     

    New video from Gavin, although he does sound like he has a cold :(

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