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Model Output Discussion - The Start Of Winter


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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

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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

    I see no downgrades and it looks like more of same with plenty of pm shots at least for the north but with mild days, mainly across southern UK. Very snowy in far north today and I think Xmas week will bring wintry days to the south too..patience will be rewarded in the long run.. the background signals are far superior to last winter.

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    Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

    You can see from the D8-10 ECM & GFS mean comparison how they handle differently the split flow of the jet as it exits the eastern seaboard:

     

    post-14819-0-71388100-1418635896_thumb.g

     

    No difference to the UK in that time period; pure zonal. But the GEFS indicate that a wedge of higher heights can edge towards Greenland. The ECM mean is convinced this is wrong. So the GEFS hint at a slightly more amplified Greenland/Atlantic after D10. If ECM is right then the flat upstream pattern will continue towards D15+ as the D10 mean suggests:

     

    post-14819-0-13458100-1418636180_thumb.g

     

    Nice to see the ECM mean (now in that range) also trend (like the GFS) towards the Alaskan Ridge and the Polar Heights migrating to that area.

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    Posted
  • Location: chellaston, derby
  • Weather Preferences: The Actual Weather ..... not fantasy.
  • Location: chellaston, derby

    to me, 'mild' is most likely to occur when we have the 0c+ upper isotherm over us... and its 'cold' (as in below the seasonan norm) when we have the -5c isotherm over us. in between the 0c and the -5c is what i take to be average/normal. just as a guide of course its not a golden rule.

    heres the gfs 00z, and the ecm out to t240 is broadly the same.

    post-2797-0-44360800-1418636426_thumb.gi note the azores high sat right over the azores, and the uk in a chilly northwesterly. and the approaching mild spell

     

    post-2797-0-71941400-1418636601_thumb.gi the mild exits later on thursday, the azores high starts to flatten out by friday

     

    post-2797-0-82197100-1418636712_thumb.gi post-2797-0-12570600-1418636736_thumb.gi

    another pulse of milder air follows the cooler pm air. high pressure to our south shifts eastwards slowly.

     

    post-2797-0-76817800-1418636823_thumb.gi post-2797-0-13052400-1418636838_thumb.gi

    the high continues drifting east, and the pattern of mild/cool continues but what is telling is the appearance of that large vortex just west of baffin.

    unless theres a major shift in these outputs there appears to be no pattern change this side of the new year, assuming of course that charts like this verify. to me its looking like a pretty average winter. (within the forseeable, im not suggesting any form of prediction/expectation for jan/feb).

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

    Just looked at the cycle 24 page at solar activity prior to November it was rather low !

    But now it's really ramped up and although not directly linked to our weather patterns there's plenty to suggest this helps specific drivers.

    And I'm now starting to see that the models do seem to be moving away from the idea of hlb !.

    Since the Azores heights has established its home to our sw in higher solar years the Azores was a very strong feature.

    Although there are no actual findings on this theory it's something I've been keen on keeping a close eye on since the spotless start of cycle 24.

    And I strongly believe that this may hold some of the answers to the hard to get hlb.

    So it's possible this could be over riding the conflicting signs that may produce hope in January.

    I hope I'm wrong and at the end of winter id be glad to see this not be a factor.

    The models today do seem to be declining there ideas of hlb ,

    with the Azores moving east to our South any further movement East and we could be seeing the dreaded bartlet .

    as john has suggest after new year if there is to be a change.

    I'm starting to fear the worst but it's certainly different to last year.

    and another point john made was heights over the uk although it still can be cold this will only generate high heating bills but without the excitement.

    and I must confess although not 100% ,

    there's most certainly a high possibility.

    Disappointed but still interested.

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    Posted
  • Location: winscombe north somerset
  • Weather Preferences: action weather
  • Location: winscombe north somerset

    A very painfull Analysis from Gibby this morning ,If its cold and snow you crave for .A big thank you Gibby for your loyalty and giving us your time everyday ,the good thing with regards our daily Models is the fact that Gibby updates everyday ,which in a nut shell tells you that things can change so lets all remember that in our everchanging Meteorological pastime ,there will be more bad times as regards what we want but gains every now and again .todays later frames of ECM with a bit of adjustment could bring us a good n westerly feed with some seasonal fun for some .Dont write off talk several days ago of a pattern change with cooler temperatures as quite often things get changed only to come back a little later .The professionals must have seen some data to suggest this and being at a far range would have only mentioned this with a fair certainty .looking at current charts and all other data available to me this morning i think that in about 10/12 days we will see a very active trough over us or to our east and n/east with the azores high relaxed somewhat but relatively high pressure over western med .IM still finding it a problem posting charts as computer i think needs replacing [christmas fingers crossed]  :cold:  :drinks:

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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

    I see another cold shot pushing SE by Friday into the weekend and more cold weather next week. : > )

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    Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)

    Looks like the Forum crashed for a while?!  06Z GFS ensembles still show 850s sliding down Post Xmas with the Op very much on the warm side.  Sorry I can't post a link (at work). 

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    Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

    The GFS 06z op continues the theme to downgrade the Greenland high after Christmas and maintain the Alaskan Ridge/Polar Heights leading to some extraordinary cold…

     

    post-14819-0-90721700-1418648062_thumb.p

     

    …to the US. Stunning if that came off. The UK remains in a warm sector:

     

    post-14819-0-13920500-1418648081_thumb.p

     

    The US also has this cold spell start around D8-10 and recycle for over a week.  I don’t know but this is a pattern that keeps recurring; trop led US cold and UK non-cold!  When the US get cold is seems more likely the UK misses the wave response cold flow. ECM similar:

     

     

    WSI_Energy
    Deep magenta's representing cold air looks to surge down across N. America during the 11-15 day period forecast http://t.co/YfoOQfiHtm
    15/12/2014 12:07

     

     

    D11 US anomalous uppers (Parallel): post-14819-0-16238300-1418648102_thumb.p

     

    The P also keeps the Alaskan Ridge and some significant cold to the US and builds a cold MLB over the UK:

     

    post-14819-0-40812200-1418648122_thumb.p

     

    The control is awful; the worse case scenario, the PV lobe setting up residence to our north as the NH becomes more meridional:

     

    post-14819-0-65526900-1418648181_thumb.p

     

    Again about 60% have the Alaskan Ridge at D16 on the GEFS. The GEM Mean at D16 also showing the development of the Alaskan Ridge:

     

    post-14819-0-15669000-1418648198_thumb.p

     

    So a mild ten days as a whole for the south then a trend for temps to slowly slide to below average for the New Year and then we see how the Alaskan Ridge changes the pattern?

     

    post-14819-0-25229400-1418648213_thumb.g

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    Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL

    Pretty universal agreement on the NAO to return to neutral or negative by month end...

     

    http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/new.nao_index_ensm.html

     

    Whether that is enough to show a cold spell is unlikely but at least any Euro slug should be temporary. In the meantime, pretty mundane weather with the odd colder day in the North and West.

     

    As ever, patience, patience patience.

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

    Afternoon all :)

     

    As we seem to have had a little break in transmission, I've quickly perused the 06Z which is not without interest in the deepest recesses of FI but in the medium term here's the Christmas Day chart:

     

    http://modeles.meteociel.fr/modeles/gfs/runs/2014121506/gfs-0-240.png?6

     

    Nothing too exciting there to be honest.

     

    http://modeles.meteociel.fr/modeles/gfs/runs/2014121506/gfs-0-336.png?6

     

    Four days later and that looks like a west-based negative NAO with a southerly tracking jet.

     

    http://modeles.meteociel.fr/modeles/gfs/runs/2014121506/gfsnh-0-384.png?6

     

    Well now....where would we go from there ?

     

    http://modeles.meteociel.fr/modeles/gfsp/runs/2014121506/gfs-0-240.png?6

     

    Christmas Day on the Parallel - very similar to the main Op to be honest.

     

    http://modeles.meteociel.fr/modeles/gfsp/runs/2014121506/gfs-0-372.png?6

     

    Classic MLB but at this time of year plenty of fog and frost would be on offer.

     

    http://modeles.meteociel.fr/modeles/gfsp/runs/2014121506/gfsnh-0-372.png?6

     

    The equivalent NH chart - interesting to note the PV over Canada trying to head west

     

    Far from certain where this will go - the two runners look to be MLB (possibly becoming HLB with time and good fortune) and a West-based NAO hopefully shifting more in our favour with time and good fortune.

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    Posted
  • Location: Ponteland
  • Location: Ponteland

    A very painfull Analysis from Gibby this morning ,If its cold and snow you crave for .A big thank you Gibby for your loyalty and giving us your time everyday ,the good thing with regards our daily Models is the fact that Gibby updates everyday ,which in a nut shell tells you that things can change so lets all remember that in our everchanging Meteorological pastime ,there will be more bad times as regards what we want but gains every now and again .todays later frames of ECM with a bit of adjustment could bring us a good n westerly feed with some seasonal fun for some .Dont write off talk several days ago of a pattern change with cooler temperatures as quite often things get changed only to come back a little later .The professionals must have seen some data to suggest this and being at a far range would have only mentioned this with a fair certainty .looking at current charts and all other data available to me this morning i think that in about 10/12 days we will see a very active trough over us or to our east and n/east with the azores high relaxed somewhat but relatively high pressure over western med .IM still finding it a problem posting charts as computer i think needs replacing [christmas fingers crossed]  :cold:  :drinks:

    Regretfully I think Gibby is right,at present we are clutching at straws. Best to wait until early January and perhaps see more favourable charts.

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    Posted
  • Location: Currently Southminster, Essex (but original home town Northampton)
  • Weather Preferences: Heavy snow/Blizzards in Winter, Cool Summers. (I'm allergic to heat)!
  • Location: Currently Southminster, Essex (but original home town Northampton)

    Fantastic post as always Tamara  :good:

     

    Looking at today's updated AO forecast, many members taking a nose dive into negative territory as we head towards the New Year.

     

    ao.sprd2.gif

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    Posted
  • Location: Newton in Bowland
  • Location: Newton in Bowland

    to me, 'mild' is most likely to occur when we have the 0c+ upper isotherm over us... and its 'cold' (as in below the seasonan norm) when we have the -5c isotherm over us. in between the 0c and the -5c is what i take to be average/normal. just as a guide of course its not a golden rule.

    heres the gfs 00z, and the ecm out to t240 is broadly the same.

    attachicon.gif1.gif note the azores high sat right over the azores, and the uk in a chilly northwesterly. and the approaching mild spell

     

    attachicon.gif2.gif the mild exits later on thursday, the azores high starts to flatten out by friday

     

    attachicon.gif3.gif attachicon.gif4.gif

    another pulse of milder air follows the cooler pm air. high pressure to our south shifts eastwards slowly.

     

    attachicon.gif5.gif attachicon.gif6.gif

    the high continues drifting east, and the pattern of mild/cool continues but what is telling is the appearance of that large vortex just west of baffin.

    unless theres a major shift in these outputs there appears to be no pattern change this side of the new year, assuming of course that charts like this verify. to me its looking like a pretty average winter. (within the forseeable, im not suggesting any form of prediction/expectation for jan/feb).

    That's the way I see it really alternating TM and PM air with temps coming in around average overall. To me the pattern looks flat for the foreseeable and unless we see a more favourable upstream pattern then all I can see is this waxing and waning continuing well into the New Year.

    ZoomButt.gif
     
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    ZoomButt.gif
     
    Edited by Hocus Pocus
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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

    Regretfully I think Gibby is right,at present we are clutching at straws. Best to wait until early January and perhaps see more favourable charts.

    At least there is some wintry weather in the UK but you have to head north to find it, for now. It looks generally milder through the midweek period with Tm air sweeping across the UK but again, northern UK soon back into colder, showery weather with snow on hills and colder air will then sweep SE by Friday with overnight frosts returning..then Xmas week brings more Atlantic lows but with cold incursions in their wake. If we are lucky with timings, some of us may wake up to a covering of snow on the big day but I'm now looking further ahead to January when we could enter a colder phase of winter, hoping the MO will put some meat on the bone as to what shape this colder spell will take..i.e. Will it be settled and cold or something snowy from the east or north.

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

    You can see from the D8-10 ECM & GFS mean comparison how they handle differently the split flow of the jet as it exits the eastern seaboard:

     

    attachicon.giftest8 (1).gif

     

    No difference to the UK in that time period; pure zonal. But the GEFS indicate that a wedge of higher heights can edge towards Greenland. The ECM mean is convinced this is wrong. So the GEFS hint at a slightly more amplified Greenland/Atlantic after D10. If ECM is right then the flat upstream pattern will continue towards D15+ as the D10 mean suggests:

     

    attachicon.gifEDH1-240 (1).gif

     

    Nice to see the ECM mean (now in that range) also trend (like the GFS) towards the Alaskan Ridge and the Polar Heights migrating to that area.

     

    Well iluustrated comment there re the flow difference on the EC-GFS anomaly charts and the additional comment that it makes little difference to the UK in that time frame. Likewise my comment last evening using the NOAA 6-10 and 8-14 to show that there is no change in the wavelength pattern likely in the 15 day time scale either.

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    Posted
  • Location: Camborne
  • Location: Camborne

    The low that needs to kept an eye on. First it was there and then it was there.

    Charts courtesy weatherbell

     

    post-12275-0-35133400-1418654322_thumb.p

    post-12275-0-90904500-1418654335_thumb.p

    post-12275-0-81408600-1418655047_thumb.p

    Edited by knocker
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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

    I have this intriguing long term fantasy that January and February might be wintry but I just want to know what the trigger will be which brings about this change. In the meantime, the broad scale pattern remains similar with some ebb and flow of the Azores high and also of depressions pushing east from Iceland into scandinavia which basically means a continuation of milder swly and colder nwly winds for the next few weeks or so.:-)

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

    I still think its too early to write off some colder weather at Christmas.

     

    Just taking the GEFS mean at T240hrs:

     

    post-1206-0-74461300-1418654804_thumb.pn

     

    You can see the PV is located further east with some weak pressure rises over Greenland and troughing in the eastern USA, the Azores high is still a little too close for comfort but the mean will cover a wide breadth of solutions some flatter and some more amplified at that stage.

     

    This far out come the day itself the pattern might be more or less amplified so you can make a case for different outcomes, bearing in mind that the pattern upstream will be undergoing some change with more amplitude during that timeframe, at this stage that amplification doesn't look like being sustained but its really a case of whether the UK can benefit during that more favourable window.

     

    Of course the anti is raised because that window of opportunity falls around the Christmas period so is getting a lot more attention than normal.

     

    I'd keep an open mind whilst the models decide on the downstream impacts of the troughing in the central USA, you never know some might have a nice surprise come Christmas morning.

     

     

     

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

    certainly no white christmas anywhere with this type of chart.

    pretty mild.

     

    gfs-1-192.png?6

    this is well into the met office range of forecasting and they certainly dont call any colder conditions over the christmas period so id be happy to call against anything other than average maybe a little above possibly white in a frost sense but nothing exciting showing.

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

    Nice post from Tamara and again restating the background factors and underlining that a notable cold outbreak in December was never likely .

    I think many now appreciate that and a lot of the disappointment recently is the flattening out somewhat of the expected pattern in the next 10 days or so.

    The approach of the Azores high will likely minimise the chance of any real cold getting established this side of Christmas with the flow looking to back more into the west or south west.

    I think however we are just starting to see hints of something different towards month end.

    As Tamara and others have already said there are increasing signs of the return of the Alaskan ridge and downstream Canadian trough around that time.

    A look at the Naefs ht  anomaly forecasts for days 5/10/15 from the 00z run

    post-2026-0-85032500-1418653527_thumb.pnpost-2026-0-56941800-1418653537_thumb.pnpost-2026-0-93849700-1418653545_thumb.pn

     

    and the 06z GFS mean run

    post-2026-0-66420300-1418654114_thumb.pn

     

     

    and gefs at the end link

    http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

     

    around 50% with the idea of an Alaskan ridge.

     

    so if we get the Alaskan ridge this should help create a Canadian trough and hopefully downstream Atlantic ridging.

     

    We have good signs of the first stage wrt Alaskan ridge but then we need to see some support for Atlantic height rises and the shift away of the Greenland vortex.

    This is probably just beyond the range of current daily modelling but something to look out for in the next week or so if this pattern is to evolve.

    i am not yet convinced it will be a smooth transition to cold-it never is in the UK i guess-but there are enough hints to show maybe something maybe is afoot after the holiday period.

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    Posted
  • Location: Camborne
  • Location: Camborne

    Nice post from Tamara and again restating the background factors and underlining that a notable cold outbreak in December was never likely .

    I think many now appreciate that and a lot of the disappointment recently is the flattening out somewhat of the expected pattern in the next 10 days or so.

    The approach of the Azores high will likely minimise the chance of any real cold getting established this side of Christmas with the flow looking to back more into the west or south west.

    I think however we are just starting to see hints of something different towards month end.

    As Tamara and others have already said there are increasing signs of the return of the Alaskan ridge and downstream Canadian trough around that time.

    A look at the Naefs ht  anomaly forecasts for days 5/10/15 from the 00z run

    attachicon.gifnaefsnh-0-0-120.pngattachicon.gifnaefsnh-0-0-240.pngattachicon.gifnaefsnh-0-0-384.png

     

    and the 06z GFS mean run

    attachicon.gifgensnh-21-1-384.png

     

     

    and gefs at the end link

    http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

     

    around 50% with the idea of an Alaskan ridge.

     

    so if we get the Alaskan ridge this should help create a Canadian trough and hopefully downstream Atlantic ridging.

     

    We have good signs of the first stage wrt Alaskan ridge but then we need to see some support for Atlantic height rises and the shift away of the Greenland vortex.

    This is probably just beyond the range of current daily modelling but something to look out for in the next week or so if this pattern is to evolve.

    i am not yet convinced it will be a smooth transition to cold-it never is in the UK i guess-but there are enough hints to show maybe something maybe is afoot after the holiday period.

     

    Well possible signs of this on the 06z GEFS but it still seems to me to leave a westerly flow and no transition to cold.

    post-12275-0-13061600-1418657548_thumb.p

    post-12275-0-29617300-1418657555_thumb.p

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

    Well possible signs of this on the 06z GEFS but it still seems to me to leave a westerly flow and no transition to cold.

    No surprise really Knocker.

    If we are to see any changes it will be beyond that as i suggested.Those +ve height anomalies in the Atlantic on that second 384hrs mean towards Greenland are what we would need to develop and strengthen.

     

     

    Edited by phil nw.
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