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Model output discussion - Jan 3rd onwards


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Posted
  • Location: South Croydon
  • Location: South Croydon
    24 minutes ago, sebastiaan1973 said:

    Sorry Trom.

    Sudden stratospheric warmings (SSWs) are significant source of enhanced subseasonal predictability, but whether this source is untapped in operational models remains an open question. Here we report on the prediction of the SSW on 12 February 2018, its dynamical precursors, and surface climate impacts by an ensemble of dynamical forecast models. The ensemble forecast from 1 February predicted 3 times increased odds of an SSW compared to climatology, although the lead time for SSW prediction varied among individual models. Errors in the forecast location of a Ural high and underestimated magnitude of upward wave activity flux reduced SSW forecast skill. Although the SSW's downward influence was not well forecasted, the observed northern Eurasia cold anomaly following SSW was predicted, albeit with a weaker magnitude, due to persistent tropospheric anomalies. The ensemble forecast from 8 February predicted the SSW, its subsequent downward influence, and a long-lasting cold anomaly at the surface.

    What I don't get from that is that it states "whether this source is untapped in operational models remains an open question" and then states "The ensemble forecast from 8 February predicted the SSW, its subsequent downward influence, and a long-lasting cold anomaly at the surface"  So to me that says the operational runs didn't show the impact of the SSW but it did show up in certain ensemble runs. If this is the case how do you know which ensemble member is correctly modelling it?

    I'm not trying to argue with you but simply trying to understand what they mean in this report and how it impacts on our ability to actually read the models.  It still seams that most of that paper is about the ability to forecast the SSW and not it's effects.  It also states "the SSW's downward influence was not well forecasted".  To me this says if you looked at the operational run it didn't correctly show the impacts but if you looked at the ensembles and knew which one's to choose you could see it.  So it all looks a bit hind cast to me.  But what I think what we are both alluding too is that this is an emerging area of modelling which will only get better with each event we witness. 

    I'd also like to say it's a pleasure when somebody who disagrees with you brings new information to the table.  I also hope you get to see some canals freeze over like you did in 2018.  It was the first time I'd seen some canals in Amsterdam with ice on the top and the first time my Dutch friends could remember since childhood.

    Edited by Trom
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    A seasonal absentee by-stander in all this - but a one-off offering from me. Its a pity that this post is getting taken apart in some quarters, because hypothetically it *could* promote some inte

    LOL, the only time I tend to interact with SL is to offer a different point of view, so I definitely would not report on his thoughts. Jeez he was still at school when I was monitoring the strat. 

    Been very busy but wasn’t a bad time to be away for a couple of days. Call a spade a spade - got next week wrong. Thought amplification would see off the impact of the displacing vortex given such wea

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    Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK

    Can’t be cold everywhere, even with an SSW thrown into the blender. I think a lot of people forget this and just equate SSw to bitter cold. Just have to wait and see folks, it’s got to fully happen and hopefully filter down to the surface yet! 

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    Posted
  • Location: Ventnor, Isle of Wight
  • Weather Preferences: Anything other than drizzle
  • Location: Ventnor, Isle of Wight
    5 minutes ago, chris55 said:

    Are you familiar with a Sudden Stratospheric Warming, and the reversal of the Stratospheric Vortex? 
     

    This is not an annual event, and can have dramatic affects on the lower atmosphere. The BFTE was a consequence of a SSW, though it was late in the season. We currently have an SSW happening relatively early in the winter, so be open to higher odds of ‘proper cold’ as we go through and beyond mid month.

    The ‘how many times’ comment is perhaps a little out of context in this particular period 🙂 
    Though, as ever, nothing is set in stone with such a fluid and complex
     atmosphere. 

    I am very familiar with SSW, Its not an annual but also it hasn't been uncommon in recent years. 

    The point I'm making is why is my view (which is actually being modelled) more provocative then members purely speculating on charts that really aren't being shown. It's tiring to be honest and boring because its like telling a story of hope! Those posts should be in the ramps and moans thread. 

    I get the NH is all over the place, but Id prefer to talk about what the models are showing. If not, we are just speculating and we could end up in fantasy land adding bits of story on. It really is that annoying. I could sit here and say, this time next month will be a snow fest, yes Id get likes and be very popular in here but it ruins it. People have called for people when the models have gone against cold for a positive post to get excited again. It really is a problem here, just my opinion and nothing personal but I read some posts and have to double check the runs in case I've missed something! its crazy sometimes!

    That said, yes it could change, but it hasn't so I wont waste my time it. 

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    Posted
  • Location: King’s Lynn, Norfolk.
  • Weather Preferences: Hot and Thundery, Cold and Snowy
  • Location: King’s Lynn, Norfolk.
    26 minutes ago, wolvesfan said:

    Evening all

    spent years watching the models,very seldom they are wrong,even more rarely they backtrack.nothing but cold rain in the output and tbh anyone who can see anything but,are kidding themselves. 

    I had to re read that about 3 times lol. You must have missed the ECM of 2012, the BFTE, Dec 2005 Easterly and even more so, summer heatwaves, plumes and their breakdowns. Infact, at 168+ hours out, they are seldom right from my experience of over 15 years watching them. 

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    Posted
  • Location: Windsor
  • Weather Preferences: Snow and cold
  • Location: Windsor

    No sign of anything favourable in lala land yet on the ensembles.

    Would be interesting to see if the MetO continue to hint on colder conditions towards the end of Jan next week.

    Would be good to see some hints in the models sooner.

    Until then ciao.

     

    8F55762F-DCDB-4B55-9517-14612DFEF5DF.png

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

    The means for the gefs, ecm and gem are very consistent with a flatter upstream and the UK influenced by a high, so maybe more settled in the south:

    gens-31-1-240.thumb.png.3a550060490bc660cd5698aa3056de52.pnggens-21-1-240.thumb.png.7e38c755f7cac2a4d5fe94bd7105ceb8.pngEDM1-240.thumb.gif.e5a2c2ea7a5a25e1c4ce9007822a0955.gif

    The gem and gfs mean both indicate the UK under a more zonal flow from d10-16. Looking at the individual gefs it is obviously more complicated, as some members do not follow the mean, though a big cluster does.

    We clearly need a couple of days for post-d7 to settle down as models tend to go OTT when there is a reset. So the transitory period is a miss for a blocky pattern as per the gfs 06z, and therefore the wait continues for many of us for a snowy period, this week looks more miss than hit and I am just expecting cold rain and higher heating bills!

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    Posted
  • Location: Tyrone
  • Location: Tyrone
    29 minutes ago, MATTWOLVES said:

    Mate you really must have had the blinkers on if you think the models are rarely wrong...or even a full blindfold on if you think they rarely backtrack..The forecast for the week ahead is remaining cold with wintry showers from the East.Nothing has changed in that respect.. what people are seeing,or weighing up,is how this SSW will affect the weather beyond the reliable time frames..No output is ever set in stone,and there are probably gonna be much ups and downs in the coming days...There is alot going on. Im still thinking the big output swings will start to appear towards later next week..

    Edit..something a little positive..The vortex appears to have weakened another 10mph in the last 12 hours...latest from Marco P..

    Eq0-gn9XMAMP5hW.jpeg

    Eq0-g-5XcAQt42w.jpeg

    Good post this is exactly why not to look much further than a few days out lots could change. 👍

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    Posted
  • Location: Rotherhithe, 5.8M ASL
  • Location: Rotherhithe, 5.8M ASL

    Terribly mild outlook with GEFS mean showing highs above 5C in London from 17th.

    56F710BB-9E89-4A64-BF54-7F93DB834199.thumb.gif.40717c5cc55f836ff918b93eef3b9c6d.gif

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    Posted
  • Location: Cornwall
  • Location: Cornwall

    Something of note is that the GFS seems to blow up that low in a matter of 12 hours quite quickly? Maybe over doing it ?

    Also a knick around the Isle Of Wright?

    gfs-0-114.png

    gfs-0-126.png

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    Posted
  • Location: Galashiels
  • Weather Preferences: Cold weather in winter
  • Location: Galashiels
    41 minutes ago, Tim Bland said:

    I first posted that the GEFS were starting to show some mild members at the very end a week or so ago and I was shot down in flames and told to pay no attention. Every day over the last week the milder members have increased and are now flattening out. Hopefully the warming up next week is just temporary, but it shows us the value of ensembles to spot trends 

    Yes you did Tim.9th to 11th January was the target dates.It was dropped but reappeared.Let’s see how things progress.

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    Posted
  • Location: Ward Green barnsley
  • Weather Preferences: Snow freezing fog heatwave thunderstorm
  • Location: Ward Green barnsley

    My personal opinion is the chances of it staying cold are still available. Too much scatter in the ensembles to change my mind just yet. I think 18z will be a cracker for cold going forward. For example If the ens were showing cold after the 10th Jan we still couldn't be confident. Still only a trend at minute. 

    Edited by weathermadbarnsleylad
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    Posted
  • Location: Poole, BH14
  • Location: Poole, BH14

    I'm sure if I remember right from 2018, i have no idea where I remember seeing it or reading it but from what i remember the models will not react to a SSW untill they see the downwelling. The downwelling hasn't happened yet from what I've just read on the latest update but it shouldn't be long.

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    3 minutes ago, Rapodo said:

    I'm sure if I remember right from 2018, i have no idea where I remember seeing it or reading it but from what i remember the models will not react to a SSW untill they see the downwelling. The downwelling hasn't happened yet from what I've just read on the latest update but it shouldn't be long.

    That is what I was trying to say yesterday, they need to see actual data at all levels of the atmosphere, not just the top!

    Edited by Mike Poole
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    Posted
  • Location: Leiston
  • Location: Leiston

    Anything that can go wrong and would go wrong for the UK usually does, seen many times.

    There also seems to be an overwhelming amount of assumptions that this SSW will send us into the freezer. What if it's the 1 in 3 that has no impact? See first paragraph.

    So surely we must wait until the event has had a chance to happen and filter down, then look to see if the models pick up a more favourable trend, as the onset looks disappointing bar a few days this week.

    We will either get lucky or we won't and I will take a few days away from this to account for the above.  I suggest anyone who can't control themselves do the same it works wonders.

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    Posted
  • Location: st albans
  • Location: st albans
    5 minutes ago, Rapodo said:

    I'm sure if I remember right from 2018, i have no idea where I remember seeing it or reading it but from what i remember the models will not react to a SSW untill they see the downwelling. The downwelling hasn't happened yet from what I've just read on the latest update but it shouldn't be long.

    How does that make any sense though?  The zonal winds chart for the ec op of yesterday showed the reversed zonal flow working down to the trop above 60.  That’s the ec op run from yesterday modelling a downwelling wave into the trop by day 10.  

    I just think that some are confusing the uncertainty of strat modelling an ongoing reversal (especially the early days) with the message that the models don’t know what they’re doing approaching and soon after the upper strat begins to reverse ....

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    1 minute ago, bluearmy said:

    How does that make any sense though?  The zonal winds chart for the ec op of yesterday showed the reversed zonal flow working down to the trop above 60.  That’s the ec op run from yesterday modelling a downwelling wave into the trop by day 10.  

    I just think that some are confusing the uncertainty of strat modelling an ongoing reversal (especially the early days) with the message that the models don’t know what they’re doing approaching and soon after the upper strat begins to reverse ....

    Yes, you were going on this one yesterday with me.  It’s not the modelling and the timing of the reversal at 10mb or anywhere else,  that will happen tomorrow at 10mb, it is that they struggle with resolving all layers of the atmosphere after this thing has happened until they have data at all levels afterwards.  Model volatility has been a feature of every SSW I’ve witnessed anyway.  

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    Posted
  • Location: Oxford
  • Location: Oxford
    4 minutes ago, bluearmy said:

    How does that make any sense though?  The zonal winds chart for the ec op of yesterday showed the reversed zonal flow working down to the trop above 60.  That’s the ec op run from yesterday modelling a downwelling wave into the trop by day 10.  

    I just think that some are confusing the uncertainty of strat modelling an ongoing reversal (especially the early days) with the message that the models don’t know what they’re doing approaching and soon after the upper strat begins to reverse ....

    High wind east 10 hpa later tomorrow.

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    Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)
    5 minutes ago, Mike Poole said:

    Yes, you were going on this one yesterday with me.  It’s not the modelling and the timing of the reversal at 10mb or anywhere else,  that will happen tomorrow at 10mb, it is that they struggle with resolving all layers of the atmosphere after this thing has happened until they have data at all levels afterwards.  Model volatility has been a feature of every SSW I’ve witnessed anyway.  

    So after it’s happened and the models have the data they will settle down a bit? So Tuesday we should start to see some effects modelled ?

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    Posted
  • Location: East Ham, London
  • Location: East Ham, London
    19 minutes ago, Mike Poole said:

    I wanted to post the clusters in full tonight because I think it explains something about the uncertainty and how it will be resolved.

    T72-96 5 clusters:

    A597E9F3-A53B-4F31-93A9-2AE2A8649A2E.thumb.png.a0fa2a8014784f710a0b087fefe754ac.png

    All look the same but subtle differences even at this time, most easily detected on the T96.

    T120-T168 5 clusters:

    7EB3A9FC-096B-4FAE-9AFD-29D04CB8C36E.thumb.png.6ebcd3d923e9fd24927225a23a989238.png

    All of them have similarly strong northern blocking it just affects us in different ways.

    T192-T240 6 clusters:

    00C103D9-A250-4AF9-968B-76144F6011EB.thumb.png.1d7eda0114164460b2e22a59fdacbc25.png

    All over the place, but a place that again has strong northern blocking, no Atlantic.  

    Finally, T264-T360:

    E1E14464-2311-495F-A9D3-D83C94998418.thumb.png.86c17ef225cd1301a862a6f2c040a983.png

    Uncertainty is resolved -a bit 2/3 Greenland block, 1/3 heading for Scandi block...what’s not to like...

     

    Absolutely - I thought there was more divergence at T+120 than I've seen at any time in the past 2-3 weeks. Normally I like to think the pattern is set at T+120 and the model output is broadly similar but tonight there are some notable cross-model differences so the evolution at the end of the week is far from resolved. The original notion of the Icelandic LP dropping south toward the British isles has been  abandoned tonight in favour of a more Atlantic-driven evolution but the message remains a sluggish Atlantic allowing for amplification - I think Scandinavia is where we should be looking and a more anticyclonic evolution generally - whether we end with a mid-latitude or a high-latitude block or move from the former to the latter I'm not sure.

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    1 minute ago, Tim Bland said:

    So after it’s happened and the models have the data they will settle down a bit? So Tuesday we should start to see some effects modelled ?

    Yes, I think so, because the modelling will be then based on observations at all layers after a very significant and quick evolution in the strat.  It’s not called a sudden stratospheric warming for nothing. I would still like to understand more about why it is always so sudden - I mean, we’ve been watching these precursors the last month or more, why does it suddenly go bang!?  Maybe one for @chionomaniac?  

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    Message added by Paul,

    Please stick to discussing the model output in this thread. For more general chat , please use the winter/cold weather/snow chat, banter, moans and ramps thread

    For local cold/snow and weather related chat, please head over to the Regional Area.

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