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Model Output Discussion - Snow for some, but what else is in store?


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Ok, I have a bit of an update. Looks like the correction westward for today got the predicted snowfall about right . Nowcasting really comes into its own for this weekend. The team think another corre

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Posted
  • Location: chellaston, derby
  • Weather Preferences: The Actual Weather ..... not fantasy.
  • Location: chellaston, derby
    1 hour ago, Nick F said:

    So my advice, if you are going to looks beyond 6 days, look for consistency / trends and match this with spread charts like above. The NE Europe trough looks stable bet, but Atlantic, W and S Europe there's more uncertainty.

    ............ Which is why some of us use the NOAA anomaly charts 😉

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    Posted
  • Location: Netherlands
  • Location: Netherlands
    16 minutes ago, Bricriu said:

    Despite people saying you can't trust models past day six, and hope casting if this feature does this or that we'll be in the freezer, the consistent signal now is for deep cold to be outside the reach of most, if not all of us. The best we can hope  for is that sometimes we are on the right side of the boundary of the colder airmass, although it looks  far more likely to be over parts of northern  England  and Scotland than the rest of us.  From an imby perspective i could get snow later next week, but its looks to be brief. The best case scenario now looks to be brief colder interludes before milder weather returns.

    I think this (not looking beyond day 6) is more based on hope, than reality. As you say, there is nothing pointing at deep cold. Even not in the EC ENS with it's 50 members. The extreme cold is far away. Low pressure is dominating the weather pattern for . You can see this below GFS6h 240h average. Of course parts of the UK can can't a short cold intermezzo. We have to wait for the final days of January for perhaps the first chance for some proper cold.

    I think the models are good enough to deal with the effects of the SSW. No winter till February. So (in my opinion) all the stories to watch for the third part of January as a period of (extreme) cold were premature.

    GFSAVGEU06_240_2.png

    Edited by sebastiaan1973
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    Posted
  • Location: Preston, 19m ASL when tide out :(
  • Location: Preston, 19m ASL when tide out :(

    Ecm's takes on tomorrow looks realistic, bit a cold wet mess for most 😐

    socialshare3.jpg
    WWW.WINDY.COM

    Wind map and weather forecast

     

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

     Low pressure is dominating the weather pattern for . You can see this below GFS6h 240h average

    I think thats probably fair but there is a vast difference between a LP based set-up like this:

    GFSP10EU06_222_1.thumb.png.88bef981673d0d6d3d5f7d03ba8d911b.png

    And this:

    GFSP11EU06_222_1.thumb.png.adc6ec6af110d65272477907d385811e.png

    Both are clearly LP driven but both have very different looking weather for the UK due to a very different looking upper high over Greenland.

     

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    Some of you might like to copy and save this link?

    It is a link to ECMWF 850 mb charts out to T+240, showing wind barbs for that height and the temperature, (done by colours with the values down the right hand side

    http://meteocentre.com/numerical-weather-prediction/map-explorer.php?lang=en&map=eur&run=00&mod=ecmwf&stn=TT850&comp=1&run2=00&mod2=ecmwf&stn2=TT850&hh2=000&fixhh=1&stn2_type=prog&mode=latest&yyyy=latest&mm=latest&dd=latest&hh=024

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    Posted
  • Location: Horley, near Gatwick
  • Location: Horley, near Gatwick
    20 minutes ago, pureasthedriven said:

    Liking the lower heights over N.Italy, too. 

    That chart has changed since I posted the above! 

    Edited by pureasthedriven
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    Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill
    2 minutes ago, Catacol said:

    Will challenge this gently. The forecasts of a potentially severe end of January were/are built on impacts of the SSW. These were not premature. This has happened, and the stratosphere is significantly disrupted. However - as is said time and again with forecasting based on SSW impacts: specifics are a nightmare to pin down. All other drivers effectively go out the window when a downwelling response to a strong SSW are occurring and so all we can do is sit and wait to see where the vortex ends up. What I think you are referring to is disappointment that we ended up with a displacement, and disappointment too that (perhaps) the shape, position and temporary splits that have occurred have enabled some atlantic energy to reappear. 

    Great stuff! I think the disappointment will be that if the winter is rather stuttering like what we have so far, even with a great trop pattern early and a big SSWE, then we look to this and wonder if Winters will ever be cold and snowy again? This may be the best winter synoptic-wise and if all we get are brief cooling downs with transient snow, then it is a death knell for future winters as global warming eats away that potential further?

    Of course, still all to play for!

    Looking at the 06z gefs and the trend is for milder to win out; London:

    graphe6_10000_308.30360412597656_153.41299438476562___.thumb.png.299ced983470857d53e38ef10646a29a.png

    Fewer and fewer colder runs and the mean dragged up.

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    Posted
  • Location: Burwell, Cambridgeshire
  • Location: Burwell, Cambridgeshire
    10 minutes ago, Catacol said:

    Will challenge this gently. The forecasts of a potentially severe end of January were/are built on impacts of the SSW. These were not premature. This has happened, and the stratosphere is significantly disrupted. However - as is said time and again with forecasting based on SSW impacts: specifics are a nightmare to pin down. All other drivers effectively go out the window when a downwelling response to a strong SSW are occurring and so all we can do is sit and wait to see where the vortex ends up. What I think you are referring to is disappointment that we ended up with a displacement, and disappointment too that (perhaps) the shape, position and temporary splits that have occurred have enabled some atlantic energy to reappear. 

    It is far from certain what the last week of January will look like yet, but if "real" winter is delayed until February - or God forbid doesnt arrive at all - then I still dont think the forecast was premature. Those of us interested in the longer term forecasting game rather than the next 72h know that all we can do is try and get the broad brush mapped out. The broad brush has been mapped out here as many began to tout as far back as December....and in fact there were some suggesting that tropospheric precursors to strat disruption were very much in play before that despite the seasonal models sticking to a +NAO setup. I think amateur forecasting hacks looking at seasonal shape have not come off too badly this season so far. All we are really missing is the detail now - the fine elements coming together to give us a surge of deep cold. What did @chionomaniac say? Synoptic heaven, weather hell? Something like that. Spot on. We are still trying to find a bit of luck to get the vortex to align in the right way to allow cold to advect west properly. 

    Time will tell. My calendar says 15 January - somewhere around the half way mark of winter (though I'd actually place half way at Jan 22 but that's just me....) What a lot has happened! Wow - a season of real interest and with so much still to go! And there are signs up top in the strat again that February could feature more stressed vortex behaviour and very uncertain weather. Some folk have been lucky already. I hope all of us can get into the action by winter's end - and ideally more than just 2-5cm of action. Gotta be 10cms+ to hit the proper snow index I reckon.........

    this is such a fantastic explanation of the bigger picture and a nice counterweight to a few 'broken records' in the forums. Thank you for explaining everything so clearly to amateurs like myself.

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    Posted
  • Location: East Ham, London
  • Location: East Ham, London
    3 minutes ago, Catacol said:

    Last post for now - its way out in la la land - but GFS at 9 days is potential snow heaven for some. There seems to be some downbeat feelings in here today so far: I'm not sure why. There is so much going on, and so much potential for winter weather over the next few weeks. Is this not what we come on here for? If it snowed 6ft every year it'd get hellishly boring!

    image.thumb.png.c1849d0501ff6c2b61d5bcd37add96d1.png

    Yes, lots of miserable downbeat so-and-sos this morning.

    GFS 06Z Control is a thing of beauty for fans of cold and while I think southern Britain is looking marginal, plenty of opportunities for snow for those further north on the morning output.

    @chionomaniacis right about the synoptics - the most interesting for a long time and a lot still to be resolved starting with tomorrow.

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    Posted
  • Location: Netherlands
  • Location: Netherlands

    I think everybody here at the forum is able to tell a SSW can deliver cold weather. My point is to be careful at writing about the repercussions. I would describe it only in terms of more chance for cold weather than normal 🙂 you talked about a historical January. If I remember it correctly.

    18 minutes ago, Catacol said:

    The forecasts of a potentially severe end of January were/are built on impacts of the SSW. These were not premature. This has happened, and the stratosphere is significantly disrupted. However - as is said time and again with forecasting based on SSW impacts: specifics are a nightmare to pin down. All other drivers effectively go out the window when a downwelling response to a strong SSW are occurring and so all we can do is sit and wait to see where the vortex ends up. What I think you are referring to is disappointment that we ended up with a displacement, and disappointment too that (perhaps) the shape, position and temporary splits that have occurred have enabled some atlantic energy to reappear.

     

    And I disagree with Chio. There is no Synoptic Heaven. The distribution of area's of high/low pressure has been okay for some of us (still waiting for the first snowflake) but they weren't good enough for all of us. Mostly polar maritime air.

    The end of February 2018 was Synoptic Heaven.

     

    GFSAVGEU06_240_2.png

    CFSR_1_2018022618_2.png

    Edited by sebastiaan1973
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    Posted
  • Location: Liphook
  • Location: Liphook
    23 minutes ago, Catacol said:

    Synoptic heaven, weather hell? Something like that. Spot on. We are still trying to find a bit of luck to get the vortex to align in the right way to allow cold to advect west properly. 

    The truth is we've been a little unlucky (or is it a sign of a warming climate?)  but several set-ups that came along could very easily have been decent sdnow events had we just been a small amount colder, or had just a little bit stronger flow from the Arctic.

    I think many aren't realizing just how close we actually were to a really quite noteable snow spell in the first 10 days of Jan. for example had the North Sea been that bit colder (as it might have been in the 80s for example) the rainy set-up seen from the easterly would have led to quite a considerable fall of snow for the SE. As it was it cold enough at altitude locally.

    Very fine margins between an ok cooler spell, and a legitimate cold and snowy spell. Thats the line we tread in this country, and unfortunately as the world warms, that line swings more towards wet and cool, rather than snowy and cold.

    Edited by kold weather
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    Posted
  • Location: Netherlands
  • Location: Netherlands
    2 minutes ago, kold weather said:

    The truth is we've been a little unlucky (or is it a sign of a warming climate?)  but several set-ups that came along could very easily have been decent sdnow events had we just been a small amount colder, or had just a little bit stronger flow from the Arctic.

    I think many aren't realizing just how close we actually were to a really quite noteable snow spell in the first 10 days of Jan. for example had the North Sea been that bit colder (as it might have been in the 80s for example) the rainy set-up seen from the easterly would have led to quite a considerable fall of snow for the SE. As it was it cold enough at altitude locally.

    Very fine margins between an ok cooler spell, and a legitimate cold and snowy spell. Thats the line we tread in this country, and unfortunately as the world warms, that line swings more towards wet and cool, rather than snowy and cold.

    With a synoptical heaven you don't need luck 😀

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    Posted
  • Location: NR Worthing SE Coast
  • Location: NR Worthing SE Coast
    18 minutes ago, sebastiaan1973 said:

    I think everybody here at the forum is able to tell a SSW can deliver cold weather. My point is to be careful at writing about the repercussions. I would describe it only in terms of more chance for cold weather than normal 🙂 you talked about a historical January. If I remember it correctly.

    And I disagree with Chio. There is no Synoptic Heaven. The distribution of area's of high/low pressure has been okay for some of us (still waiting for the first snowflake) but they weren't good enough for all of us. Mostly polar maritime air.

    The end of February 2018 was Synoptic Heaven.

     

    GFSAVGEU06_240_2.png

    CFSR_1_2018022618_2.png

    Historic January would be CET below zero with ice days and wdespread snowcover,but despite the signs and some people thinking that would happen,we have just had transient snowcover mainly  on Northern Hills ,so noting historic at all.

    Need everything shown in the models to move further South for everyone to get into the action,too much atlantic sourced air at the moment,hence only higher ground really effected ,need more N/NE air-flow less sea-track.

    Edited by SLEETY
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    Posted
  • Location: Banbury
  • Weather Preferences: Deep Deep Snow causing chaos
  • Location: Banbury
    24 minutes ago, IDO said:

    Great stuff! I think the disappointment will be that if the winter is rather stuttering like what we have so far, even with a great trop pattern early and a big SSWE, then we look to this and wonder if Winters will ever be cold and snowy again? This may be the best winter synoptic-wise and if all we get are brief cooling downs with transient snow, then it is a death knell for future winters as global warming eats away that potential further?

    Of course, still all to play for!

    Looking at the 06z gefs and the trend is for milder to win out; London:

    graphe6_10000_308.30360412597656_153.41299438476562___.thumb.png.299ced983470857d53e38ef10646a29a.png

    Fewer and fewer colder runs and the mean dragged up.

    Wouldn't the milder weather be because of the Southerly tracking LP's 

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

    Right this is a pure speculation post, based on something I've noticed on the GFS parallel in FI:

    image.thumb.png.91ede030752400cc15e0d971b48920df.png

    Notice that little area of surface high pressure poking from Russia back to the North Sea? Back-door cold very nearby? Combined with low pressures running regularly into Southern Britain?

    Will probably come to nothing but I will be looking out to see if this pops up again!

    Please don't take this too seriously as this is purely for enjoyment (the European part of the chart, not the Greenland part!), but...

    image.thumb.png.d24e70a2b4545a5e5d5d85532c59ee6e.png

     

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    Posted
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
  • Weather Preferences: continental climate
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
    2 minutes ago, sebastiaan1973 said:

    With a synoptical heaven you don't need luck 😀

    If someone showed me this NAO chart back in autumn I would bite their hand of. Yet so far it produced about 2C above average winter here in Central Europe - Ural Blocking in December ultimate winter killer here. We were going to bite the bullet then for SSW induced cold down the line, that down the line goal  post has been moved now to February as ensemble modeling suggest nothing but cyclonic cold at best. It shows to me how sometimes large scale dynamics may not have surface impacts on micro scales. The question I cant answer is how come only northern Spain is below average with all that blocking,surely the Arctic being so warm plays a huge role how much less cold air is available these days.

    compday.q2Q3k0AS0A.gif

    nao.sprd2.gif

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    Posted
  • Location: Stroud, Gloucestershire
  • Weather Preferences: Extreme!
  • Location: Stroud, Gloucestershire
    1 hour ago, Nick F said:

    Morning, trends still good from the 06z.

    Agree with not taking operational charts beyond day 6 too literally, particularly with added uncertainty with how the models deal with the imprint of the recent SSW and its displacement and, today, the brief split of the SPV. Though the ramifications of the split and further weakening of the already weakened SPV may not be seen until later this month.

    ecmwf10f48.thumb.png.bfd99e0b6a5a2446f93b97bb2894c901.png

    The 06z op's positive signal for coldies is it delays phasing of Atlantic troughing with the NE Europe trough, which gives chance to get the arctic cold in. Get the arctic cold air in and, should the southern arm of the jet undercutting the Greenland block be weak enough, then weaker lows moving over the Atlantic under the block will have do a 'slider' as they encounter cold air over NW Europe. If the jet under the block get too strong, then we end up more like 00z EC and the Atlantic troughing gradually phases with the NE Europe trough.

    We see 00z/06Z GFS op diverge from the 00z EC det past day 6 with troughing over Europe, GFS digs a deep trough, while EC is much flatter. We need the deeper trough, as this diffluent nature of such a deep trough, i.e. strong jet on the western side of the trough, will better advect arctic cold south across the UK than the EC's flatter trough.

    Day 8 - Sat 23 Jan 00z

    GFS 00z + 06z

    GFSOPEU00_192_1.thumb.png.5a5e514366e611aaeed85419259d4cfd.pngGFSOPEU06_186_1.thumb.png.2586e6bb51b971f124a3436da97d0892.png

    EC 00z

    ECMOPEU00_192_1.thumb.png.a5303b278de759f8d486eefaa02a6261.png

    We can see from the EC spreads the uncertainty of 500 hPa heights over the Atlantic but also with the heights over Europe, which suggests there could be improvements with regards to higher heights between NE European trough and troughing over NW Atlantic plus deeper troughing over Europe as per GFS. Also note spread over western Greenland, maybe EC det retrograding the block too much?

    EEM1-192.thumb.gif.72d5a5439119486dde4c5f8fef218653.gifEEM1-216.thumb.gif.8ac85682a309d20390cfb866bceb77ae.gif

    So my advice, if you are going to looks beyond 6 days, look for consistency / trends and match this with spread charts like above. The NE Europe trough looks stable bet, but Atlantic, W and S Europe there's more uncertainty.

    The EC spreads are interesting, we really need to see the lows sliding in from the Atlantic into Europe! The uncertainty with this option is highlighted. We don't want them phasing with the Scandi trough, leaving us on the mild side, get them into Europe and we should stay on the cold side further south with lots of boundary snowfall.

    spacer.png

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    Posted
  • Location: Cambridge
  • Weather Preferences: Heavy snow & long hot summers
  • Location: Cambridge

    Awful runs if cold and snow is what you are after. Lots of rain and flooding backend January into Feb.

    Nothing suggests otherwise.

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    Posted
  • Location: Banbury
  • Weather Preferences: Deep Deep Snow causing chaos
  • Location: Banbury
    3 minutes ago, DCee said:

    Awful runs if cold and snow is what you are after. Lots of rain and flooding backend January into Feb.

    Nothing suggests otherwise.

    This side of 120 hours I would agree with you , from the 20th through to the 26th there are many many snow options 

    image.thumb.png.23e8bec0de9c06022820c1dfefe5737d.png

    Edited by MJB
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