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Model Output Discussions 12z 01/06/2017


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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

    Nice end to July under high pressure and an increasingly hot early August on the Gfs 00z..Bank!:D

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    Edited by Frosty.
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    An unseasonally wet, cool and windy day amidst an underwhelming week of weather does not a summer make. Much as anticipated through the second half of Spring, the hand-over to Summer sees the atm

    There have been some strange observations made today, as too often occurs in this thread whatever the time of year, and largely based on the usual knee-jerk response to longer term suggested NWP.

    You always seem to jump in on my posts, along with a few others. Why don't you try giving your assessment of the models instead of picking holes in others efforts!

    Posted Images

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

    The ECM is struggling in particular at the moment. Its op run has reverted back to the standard UK low scenario (albeit slightly more north-based) for T96/T120. However, one wouldn't expect the ensemble mean to be so volatile at just T96 and T120. Here is its last three runs for the coming Friday:

    EDM1-120.GIF?00  EDM1-120.GIF?12  EDM1-96.GIF?17-12

    Last night's is clearly out of sync, being much flatter. But even comparing the first and last charts, big differences for D4/D5 charts with respect to Atlantic ridging and the size/shape of the trough.

    The one idea from last night's ECM that seems to have "stuck" this morning, however, is a link-up between the UK trough and the upper trough towards Finland/Russia. This prevents the "lock-in" of heights sweeping round from Scandinavia, and allows a swift exit for the UK low after Saturday:

    ECM1-96.GIF?17-12  ECM1-120.GIF?17-12  

    and by Monday it has gone

    ECM1-168.GIF?17-12  

    compared with GFS, which does not have the UK/Scandi trough link up, and keeps the trough slow moving - the GFS has also seen the small ridge, and has pushed the trough further north now, though:

    gfs-0-120.png  gfs-0-168.png

    The UKMO and GEM return to a more stable UK low

    UW144-21.GIF?17-07  gem-0-144.png?00

    So still major modelling issues for next weekend.

    Beyond that, another climbdown is starting to appear on some models. I would guess that, in the last 5 years, the failure rate of ridging to Greenland modelled at T168 must be about 90%. So I can't help thinking that this

    EDM1-216.GIF?17-12 

    rather than this

     gens-21-1-216.png

    will be the way forward for next week.

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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

    In a nutshell, the first half of this week looks very summery with long spells of sunshine, unbroken sun for some during today and tomorrow and becoming warmer, hotter and more humid. Tues night and weds bring an increasing chance of thunderstorms across southern uk which will gradually spread north through wednesday..enjoy the warmth.:) 

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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
    48 minutes ago, geoffw said:

    what are your opinions of august for weather ?

    Bit of a guess, but maybe Scandi trough / Azores High displaced N, with a reasonably balance between settled/unsettled spells and best conditions in the south and west.

    But hey, look at the trouble we're having with Thursday this week, let alone next month!!

    The GFS 06Z is keen on getting more of a ridge underneath the main trough and as a result both Saturday and Sunday are back into play as warmer days in the SE. Also note the continuing trend to diminish the N Atlantic ridge:

    gfs-0-132.png?6

     

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    Posted
  • Location: County end Oldham 202 m Above sea level
  • Location: County end Oldham 202 m Above sea level

    6z better for the SE as the trough is ever so slightly shifted north, still dreadful IMBY and further north though..

    Is the azores high going to make it???

    Edit probably not its getting squashed at228h by ANOTHER Atlantic low...

    Edited by northwestsnow
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    Posted
  • Location: Solihull, WestMidlands, 121m asl -20 would be nice :-)
  • Weather Preferences: Cold and Snow -20 would be nice :)
  • Location: Solihull, WestMidlands, 121m asl -20 would be nice :-)

    GFS 06Z :D It's only one run but definitely in the right direction.

    gfs-0-180_wyf1.png 06 Z gfs-0-186_rmx1.png 00 Z

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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

    Again the Gfs 6z shows an improving low res, especially further south as high pressure builds in with plenty of dry, sunny and increasingly warm weather.:)

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    Edited by Frosty.
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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

    Ensembles now trending this low even further N and W - about 50% have the continental air even further into England/Wales by Sunday, when compared with the op. A couple of members:

    gens-5-1-126.png  gens-12-1-126.png

    17 out of 22 now do not have the centre of the trough over any part of the UK by T144. A massive turnaround from this time yesterday.

    Not a single ensemble member follows the ECM op idea of merging the trough with a Swedish/Finnish trough.

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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

    It increasingly looks like a north / south split in the weather will take place with a broadly westerly pattern becoming established, for a time more north of west and then trending south of west. The most changeable / unsettled and coolest atlantic conditions across northern uk with the south rather better with longer fine and pleasantly warm spells and short-lived changeable blips but rather breezy at times everywhere. Looking at the GEFS 6z mean shows a gradual improvement further south as time goes on with Azores ridge influence increasing. In the meantime, enjoy the summery next few days.:)

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    Edited by Frosty.
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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
    6 minutes ago, Man With Beard said:

    Ensembles now trending this low even further N and W - about 50% have the continental air even further into England/Wales by Sunday, when compared with the op. A couple of members:

    gens-5-1-126.png  gens-12-1-126.png

    17 out of 22 now do not have the centre of the trough over any part of the UK by T144. A massive turnaround from this time yesterday.

    Not a single ensemble member follows the ECM op idea of merging the trough with a Swedish/Finnish trough.

    Quite something watching these ideas bounce between the models. GEM was keen on the merger with S/F trough yesterday leading to a fast exit but a cool and showery NW-N flow behind (this model does tend to over-amplify in a big way though), but handed that over to each of UKMOECM and the EC Ens. this morning. Meanwhile GFS/GEFS have been trending toward yesterday's 12z ECM and in doing so has now gone beyond the shift that the ECM Ens. underwent yesterday evening. 

    I am starting to suspect that a factor behind this extreme variability in LP position and movement is a struggle to resolve finer detail regarding a fairly dramatic N. Atlantic SST anomaly pattern and how that affects the strength of thermal winds (i.e. the jet stream) on a relatively small scale; we have a vast area of anomalously cold waters to the west interacting with a swathe of notably above average SSTs extending from the eastern subtropical Atlantic to the North Sea (and increasingly Barents/Kara so far this month).

    This being superimposed onto the issues handling AAM changes. Orbits in the GSDM plot are not that often as fast - with large dM/dt (difference over unit time) threatening to rapidly amplify any errors in modelling - as we're currently seeing.

    A word of caution is however due regarding the emerging Euro-Scandi idea from GFS/GEFS, as this model is the most enthusiastic by far with propagating tropical convective signals east - something that's hit the wall a number of times lately. While the convective signal looks weak, such can still tip the balance in such delicate situations. I wish I could see what the EC ens. are doing with the MJO for example but the plots from this model have gone AWOL as they are known to do from time to time.

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

    Still very embarrassing differences between models at T96. UKMO still going for a low centred over central England - GFS never lets the low make landfall on the UK mainland, and by Saturday summer is pushing back in from the south. Why can't they just get on??

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    Posted
  • Location: Cambridge, UK
  • Weather Preferences: Anything out of the ordinary!
  • Location: Cambridge, UK
    5 minutes ago, Man With Beard said:

    Still very embarrassing differences between models at T96. UKMO still going for a low centred over central England - GFS never lets the low make landfall on the UK mainland, and by Saturday summer is pushing back in from the south. Why can't they just get on??

    Indeed. UKMO 12z run tonight - horrendous, low pressure, trough over the UK. GFS keeps the muck at arms length with a westerly regime. Stark differences.

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    Posted
  • Location: Worcestershire
  • Weather Preferences: Forecaster Centaurea Weather
  • Location: Worcestershire

    Such a crucial next week for so many being the start of the school holidays. If you're looking at the GFS and parallel GFS ops, looking good for the south and SW, probably a slower start with the UKMO. GEM, hmm, that might take a little longer but the GFS banging the drum for a quicker return to summer.

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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

    Spot the difference:D today's Gfs 12z looks a lot better than yesterday's regarding the weekend and next week.

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    Edited by Frosty.
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    Posted
  • Location: Cambridge, UK
  • Weather Preferences: Anything out of the ordinary!
  • Location: Cambridge, UK

    Sadly, the UKMO run matches the anomaly charts more closely than the GFS....add to the fact that it shows diabolical weather, and you know all too well that it will end up being right!

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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

    Much much better looking Gfs 12z compared to the last few days with high pressure returning from early next week and becoming warmer and warmer..looking great..wow

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    Edited by Frosty.
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    Posted
  • Location: Sheffield
  • Weather Preferences: thunderstorms, heatwaves, extreme weather
  • Location: Sheffield

    Bugger, typical GFS raising my hopes, dreams and expectations with a good 12z run. 

    Will we see a positive ECM later?

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

    indeed the gfs is another run supporting yesterdays ecm that had the nasty little low exit northwards quite quickly and not getting trapped in. ok this gfs run like yesterdays ecm is still unlikely to happen... but....

    yes please mr god!

    yes please.png

    Edited by mushymanrob
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    Posted
  • Location: Sheffield
  • Weather Preferences: thunderstorms, heatwaves, extreme weather
  • Location: Sheffield
    Just now, mushymanrob said:

    indeed the gfs is another run supporting yesterdays ecm that had the nasty little low exit northwards quite quickly and not getting trapped in. ok this gfs run like yesterdays ecm is still unlikely to happen... but....

    Well quite! Given the summer so far we can't discount another shot of heat later next week. After all we've had a few plumes already :) Rinse and repeat?....

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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

    Awesome..what a transformation, much nicer to look at anyway!:D

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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
    37 minutes ago, Man With Beard said:

    Still very embarrassing differences between models at T96. UKMO still going for a low centred over central England - GFS never lets the low make landfall on the UK mainland, and by Saturday summer is pushing back in from the south. Why can't they just get on??

    Actually, make that T48. I've just looked at 5 models for that timeframe (someone's got to do it eh) and there is absolutely no agreement over the shape, size and position of the low(s) beneath Iceland in just 2 days time. The highest Shannon Entropy event ever??

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    Posted
  • Location: chellaston, derby
  • Weather Preferences: The Actual Weather ..... not fantasy.
  • Location: chellaston, derby
    1 minute ago, Steel City Skies said:

    Well quite! Given the summer so far we can't discount another shot of heat later next week. After all we've had a few plumes already :) Rinse and repeat?....

    i dunno... tbh i still think we have a good chance of a superb hot august. ive been looking at some charts from july prior to a august heatwave... just look at this from 1995, who would have thought what would follow?..

    1995.gif

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