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Model output discussion - deep cold inbound?


Message added by Paul,

It's a busy time right now, so please ensure you only post about the model output in this thread. 

For local snow discussion and will it snow posts, please use the regional threads
And for more general chat please use the chat, moans and ramps thread.

There's now also a cold spell chat and discusison thread.

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Posted
  • Location: Leicester
  • Location: Leicester
    2 minutes ago, sheikhy said:

    Dont think we looking at the upstream low mate!!its what happens over us and to the south east much more important i think?!

    I see, well the ECM is still a few hundred miles further SE with the low I think

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    Posted
  • Location: Derbyshire
  • Weather Preferences: Winter
  • Location: Derbyshire
    9 minutes ago, weirpig said:

    Not an out and out outlier   but very much right at the mild end  in regards  to the timeframe for an easterly 

    image.thumb.png.820285ade26fd171b126145b2ef70b11.png

    So we’re waiting to see if it flips back on the 12z or if the ecm and ukmo step towards it for a middle ground scenario ? 

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    Posted
  • Location: Pontypridd, Wales 240m asl
  • Location: Pontypridd, Wales 240m asl

    tug of war is this then - ECM, GFSp, UKMO, ICON, GEM, the BEEB (BBC), UKMET - against the old and tired GFS - I don't gamble - but if i did i know where my money would be on

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    Posted
  • Location: Newport South East Wales
  • Weather Preferences: Blizzards in winter Hot and sunny in summer...other is simply boring!!
  • Location: Newport South East Wales
    2 minutes ago, andymusic said:

    tug of war is this then - ECM, GFSp, UKMO, ICON, GEM, the BEEB (BBC), UKMET - against the old and tired GFS - I don't gamble - but if i did i know where my money would be on

    sounds like David against Goliath ...we know how that turned out 🙈

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    Posted
  • Location: Liphook
  • Location: Liphook
    14 minutes ago, sheikhy said:

    Dont think we looking at the upstream low mate!!its what happens over us and to the south east much more important i think?!

    Its all ultimately going to get connected up.

    The key thing is how early that happens and where?

    There are three main areas to watch, all tjhree will have an impact ultimately on whether the cold makes it further south or not:

    1: the LP over the UK

    2: The Iberian low

    3: The Atlantic low

    Some large differences on how the GFS handles all three elements compared to the other models. The 06z GFS did fall in line somewhat with no.2 but not enough to cancel out the differences on how it handles 1 and 3.

    We may end up getting a middle ground where the easterly remains fo the north, the south gets some of the recycled cold air from the western flank of the LP as it moves in/away over the low countries. Snow for south would then depend on exactly how the fronts line up, etc and the  possibly how much of a push from the south-west we end up seeing from low No.3.

    Edited by kold weather
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    Posted
  • Location: Louth, Lincs
  • Weather Preferences: Snow, frost, thunderstorms and sunny summer days.
  • Location: Louth, Lincs
    4 minutes ago, Cold Winter Night said:

    It seems so, but not quite.

    When we attempt to evaluate how reliable the output really is, it's best to look at a number of things (not exhaustive):

    - Is an operational (high resolution) run more or less in line with its own ensemble mean or ensemble clusters?
    - Is it in line with other models' operational and/or ensembles?
    - Is it consistent with previous runs, or does it jump from one solution to another?
    - Is it in line with background signals?
    - At what timeframe does a specific model usually perform best?
    - Are we talking about more reliable short term forecasts or is it the more fickle FI?
    - Does the model have known biases that might be an issue?

    ECM had many issues at the end of last week and early weekend, it jumped around quite a bit, was not in line with its ensembles, not in line with the other models and it was mostly FI.
    That's why ECM was dismissed. GFS was more steady and in line with other output.

    Now the situation is different. ECM is steady and in line with its ensemble and in line with UKMO and others. Those are usually very good at short range (up to day 5,6). GFS is suddenly jumping around, its ensemble is messy and it blows up lows, which is a known bias.
    That's why this time GFS is, still cautiously, dismissed by many.

    It would not be different if GFS/GEFS were the only ones forecasting cold, with EC/UKMO forecasting mild, so it's not about what we want to see.

    Yes I take all that on board and mainly agree with you. I was kinda being facetious as to how people dump models in favour or others when they don’t like what they see. ECM is usually the safer and more steady model out of the bunch in normal times. 

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    Posted
  • Location: Netherlands
  • Location: Netherlands
    Just now, kold weather said:

    Its all ultimately going to get connected up.

    The key thing is how early that happens and where?

    There are three main areas to watch, all tjhree will have an impact ultimately on whether the cold makes it further south or not:

    1: the LP over the UK

    2: The Iberian low

    3: The Atlantic low

    Some large differences on how the GFS handles all three elements compared to the other models. The 06z GFS did fall in line somewhat with no.2 but not enough to cancel out the differences on how it handles 1 and 3.

    We may end up getting a middle ground where the easterly remains fo the north, the south gets some of the recycled cold air from the eastern flank of the LP as it moves in/away over the low countries. Snow for south would then depend on exactly how the fronts line up, etc and the  possibly how much of a push from the south-west we end up seeing from low No.3.

    What's your opinion about EC6h in this aspect (the three points) as showed by Bluearmy ? Which version is better in your eyes? 6h or 0h thanks!

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    Posted
  • Location: Liphook
  • Location: Liphook
    2 minutes ago, sebastiaan1973 said:

    What's your opinion about EC6h in this aspect (the three points) as showed by Bluearmy ? Which version is better in your eyes? 6h or 0h thanks!

    Broadly the same as the 00z ECM.

    The one difference I do note is the angle of the high pressure on the 06z ECM to the north of us is much closer to the GFS 06z in terms of orientation compared to the 00z run, but thats probably more a variation on a theme than anything to be overly concerned about, especially as the other features all look broadly the same again.

    ICON will be a big test btw, as its 06z run did make some nods towards the 06z GFS solution, especially with how it handles the Atlantic low. May be a more iffy run this time, whether it makes it or not.

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    Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

    Worth saying that for Fri 5th-Tues 9th period the NOAA are going with a blend of the Euro and GFS Ensemble means rather than operationals.

    How do the means look on Tuesday, backing their ops or not for us.

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    Posted
  • Location: North Hampshire/Surrey
  • Weather Preferences: Cold, Snow, Fog, Frost, Storms and Rain if it rains like it means it.
  • Location: North Hampshire/Surrey
    14 minutes ago, Cold Winter Night said:

    It seems so, but not quite.

    When we attempt to evaluate how reliable the output really is, it's best to look at a number of things (not exhaustive):

    - Is an operational (high resolution) run more or less in line with its own ensemble mean or ensemble clusters?
    - Is it in line with other models' operational and/or ensembles?
    - Is it consistent with previous runs, or does it jump from one solution to another?
    - Is it in line with background signals?
    - At what timeframe does a specific model usually perform best?
    - Are we talking about more reliable short term forecasts or is it the more fickle FI?
    - Does the model have known biases that might be an issue?

    ECM had many issues at the end of last week and early weekend, it jumped around quite a bit, was not in line with its ensembles, not in line with the other models and it was mostly FI.
    That's why ECM was dismissed. GFS was more steady and in line with other output.

    Now the situation is different. ECM is steady and in line with its ensemble and in line with UKMO and others. Those are usually very good at short range (up to day 5,6). GFS is suddenly jumping around, its ensemble is messy and it blows up lows, which is a known bias.
    That's why this time GFS is, still cautiously, dismissed by many.

    It would not be different if GFS/GEFS were the only ones forecasting cold, with EC/UKMO forecasting mild, so it's not about what we want to see.

    Thanks for this great explainer, really useful. Can anyone point me to some learning material about 'ops', 'dets', 'means' and 'ensembles'? I just can't seem to grasp the differences. Thank you. 😊

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    Posted
  • Location: Essex, UK
  • Location: Essex, UK
    4 minutes ago, summer blizzard said:

    Worth saying that for Fri 5th-Tues 9th period the NOAA are going with a blend of the Euro and GFS Ensemble means rather than operationals.

    How do the means look on Tuesday, backing their ops or not for us.

    Pretty sure that’s not necessarily a bad thing👀

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    Posted
  • Location: Folkestone
  • Location: Folkestone

    Hi all,

    Would someone be able to list the different models and their roll out times please.

    Thanks 

    Edited by snowfall09
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    Posted
  • Location: Weston-S-Mare North Somerset
  • Weather Preferences: Hot sunny , cold and snowy, thunderstorms
  • Location: Weston-S-Mare North Somerset
    3 minutes ago, sheikhy said:

    I think we should all forget about the icon and just skip straight to the gfs?!!😜

    What happens if ICON is a snowy nirvana  from Friday onwards!!!

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    Posted
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
    47 minutes ago, MATTWOLVES said:

    Surely anyone with any forecasting sense will use a blend of all the model output options here! If we have ECM UKMO GEM ICON all going cold but the GFS not so,then surely the appropriate option is to discard the GFS,especially at this critical 4 day timescale.

    Not sure that logic is as flawless as you think it is...

    47 minutes ago, Djdazzle said:

    I've underlined the key part of your post!

    It is annoying though - they have access to loads of data!

    Why is it annoying if you are so confident you are right? What's the difference?

    I'm sure these have been posted and analysed (I've been busy), but NOAA charts are somewhat suggestive of a flow reversal and potentially therefore a colder spell. Looks a little far north however, and given the margins are fine, it doesn't necessarily help us determine the key detail. 8-14 day chart does not necessarily indicate anything overly dramatic or lasting.

    EC/GFS also mixed. Will be interesting to watch these evolve.

     

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    Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea
    33 minutes ago, sheikhy said:

    Dont think we looking at the upstream low mate!!its what happens over us and to the south east much more important i think?!

    The Atlantic low on the GFS is stronger south with a less prominent feature over greenland, because of this the phase happens further west as the southern low drags the nothern low.

    image.thumb.png.1a225270eaed4378b12f44328ab95323.png

    The ECM has already begun to phase the low keeping further NW, this allows the ridge ahead to build better heights to our north.

    image.thumb.png.bee60a1423181d3805929b3128a8d23f.png

    Notice on the ECM that the low further west in the Atlantic around Greenlands tip.

    image.thumb.png.481d20903e4933ef430adefc1a61281a.png

    GFS has it further east and the ridge between the two lows is smaller meaning the block north has less forcing due to not getting the same level of pumping that the ECM's did. Meaning it can travel further north.

    image.thumb.png.2347a8180602456a5603ce1909f4996b.png

    The delay is important as it allows the low to develop in a more favourable position before they phase and the stronger block keeps it south. But they're both important to the puzzle. It's a race against time. 

    UKMO also handles it differently with a less deep low by greenland but keeps the entire system further west anyway. UKMO probably looks to be a middle ground so I will continue to follow it into battle.

     

    Edited by Snowman.
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    Posted
  • Location: Broxbourne, Herts
  • Weather Preferences: Snow snow and snow
  • Location: Broxbourne, Herts

    T120 on 28 Jan   GFS v ECM   0z runs
    1152519227_ECM0Z28JanT120.thumb.jpg.109cc675ef56132f8c7dbfcf7dae81f6.jpg2066742677_ECM0Z02FebT0.thumb.jpg.97a22eb99f8a80970f23ff0ba49583c8.jpg
    Both pretty impressive I'd have to say....would have to give it to ECM if anything.

    1041152330_GFS0Z28JanT120.thumb.jpg.a001948d3a47fc10455b0bd282425a13.jpg

     

    Hoping ECM remains the in form horse......

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    Posted
  • Location: Near Gouda, Holland 6m Below sea level
  • Weather Preferences: Sun, snow, ice. Very hot or very cold.
  • Location: Near Gouda, Holland 6m Below sea level
    17 minutes ago, Mizzle said:

    Thanks for this great explainer, really useful. Can anyone point me to some learning material about 'ops', 'dets', 'means' and 'ensembles'? I just can't seem to grasp the differences. Thank you. 😊

    Well, you might find learning material in the "Learning & research" section here on Netweather.

    About the terms you mention, in short:

    - An Op = Det = Operational: This is the main run of a model. It is run at the highest resolution, so the atmosphere is divided up in smaller blocks. This gives these runs finer detail, they are less likely to miss nuances that might be important later on.

    - The mean is the mean of the ensemble runs. These are a number of extra runs, apart from the Operational runs. These are at a lower resolution, so the supercomputers can handle more of them in a short term.
    It includes the control run which has the same starting data input as the operational (but run on that lower resolution) and a number of perturbations (P1, P2, P3 etc) or members that have slightly altered input at the start, so we can see if the starting data has much influence on the outcome or not.

    - The EC or ECM is the model that is run by the ECMWF (European Centre for Medium-Range Weather Forecasts).
    - The UKMO is run by the UK Met Office
    - GFS (Global Forecast System) is run by the American NOAA-NCEP
    - GFS parallel (GFS //) is the newest update for GFS, that is being tested alongside the old one.
    - The GEM is Canadian.

    Edited by Cold Winter Night
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    Posted
  • Location: Wellseborne, Warwickshire
  • Weather Preferences: Southerly tracking low pressure in winter. Hot and thundery in the summer
  • Location: Wellseborne, Warwickshire

    When did the ecm start using an 06?

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

    LOL read posts about 06z backtracking and then looked at the run and ensembles for myself.

    graphe3_10000_264_99___.gif

    Doh!

    It is actually worse through the important period through to 96h with the low pushing even further NE than 00z and the ensemble suite is more solidly behind it with the cold spell all but wiped out.

    Granted from  96h it is marginally improved with the low moving further S and E but by then the damage is done.

    Upper air was only a little colder because the low moved further E initially brining some wraparound cold air.

    GFS 00z V GFS 06z 72/96h

    gfs-0-78.pnggfs-0-72.png?6

    gfs-0-102.pnggfs-0-96.png?6

     

    The low moving so far N not only prevents a quicker and more direct E flow but weakens the blocking to our N which of course has a negative knock on effect in the longer term but another issue is the phasing of the Iberian trough.

    This happens earlier with GFS while the low is over the UK which prevents it moving more effectively E and clearing while it happens a little later with ECM and UKMO when the low is just about cleared SE.

    Look at the comparison with ECM at 120 and the alignment of the trough, it is more vertical with GFS due to this early phasing which builds heights a little to the SE and stalls the exit of the low which in turn allows high pressure to the N to sink SE instead of retrogress W

    ECM/GFS (trough alignment to S more vertical, heights to SE increased, high to NW dropping SE)

    ECM1-120.GIF?02-12gfs-0-114.png

    All of this means that by 144 it is game over because the low on GFS is stalled to our SE on the 00z and 06z with high pressure splitting and sinking SE rather than retrogressing as a whole W.

    GFS 06z is an improvement here tot he 00z but it is still too late as the gate is closing on the low preventing its exit.

    ECM 144 V GFS clearly shows how the high on GFS has collapsed SE while retrogressed W on ECM

    ECM1-144.GIF?02-12gfs-0-144.png

    If you want to have the fun of second guessing the output as it rolls out then those areas are what you need to be looking at and you should be able to accurately predict which way the run is moving by 96h in terms of deep cold spell of at least several days or brief cold snap.

     

     

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