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ZK099

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    Model output discussion - 7th January onwards

    in Forecast Model Discussion

    Posted

    Just now, khodds said:

    Don’t get me wrong, I’m loving the charts and high spirits right now but I’m erring on the side of caution, we have been here before... it’s still a long way out in weather terms. Until we are at T+24 im going to be sitting here with my hands in front of my face in case it all goes wrong 

    Oh absolutely, we've seen it collapse regularly very close to the reliable. But if that low off the US behaves as we want it to, the pattern should begin in its wake. This is the key part. After that everything else should fall into place. That happens around Tuesday/Wednesday. If we can get within 72hrs of that and have a full house, I'm very confident. 

    • Like 1

    Model output discussion - 7th January onwards

    in Forecast Model Discussion

    Posted

    7 minutes ago, snowfish1 said:

    Looks good doesnt it. The easterly is around a week long on gfs! Haven't seen anything like it se would be buried?  Ecm very similar

    I wouldn't worry about length too much yet. If that storm out of the US behaves the way we want it to, to perfection, then we could be locked in for some while, which is what the EC46 is suggesting if I'm not mistaken. Tbh it's shown a pretty constant theme of HL Blocking and Euro Troughing throughout January, February and even March. By no means nailed on yet. Let's see what the UKMO says... 

    • Thanks 1

    Model output discussion - 7th January onwards

    in Forecast Model Discussion

    Posted

    Well this is what makes model watching so good. Honestly like watching a thriller football match at times, flipping one way, then another. Fascinating viewing. 

    The intense cold is essentially dependent on the behaviour of that storm coming out of the US. Which model handles those most accurately? As the experts have said, ECM. The ECM shows that low heading south down the UK which results in a much better synoptic set up for us. Looks like the GFS has finally gotten with the programme and fallen in line with the ECM. 

    The UKMO is still the odd one out. However, we have an SSW, favourable teleconnections, low solar activity. It seems as though everything points towards a cold spell and because the ECM handles those storms better, and the cold spell is dependent on the storm, I think the logical step is to back the ECM on this one. Expect the UKMO to come on board soon. Nothing is ever guaranteed in this business but my eggs are in the ECM basket. 

    • Like 1

    Hunt For Cold: Model Discussion - Heading Into Christmas

    in Spring Weather Discussion

    Posted · Edited by ZK099

    Interesting GFS 18z op. Deep, deep cold out in Europe, first time I've seen it that deep, that close to our shores. Any easterlies thereafter would be extremely potent. 

    Obviously we're not looking at individual op runs at this point, but let's hope it's a trend. Definitely not a bad thing to cool down Europe before we get any easterly winds developing. 

    Hunt For Cold: Model Discussion - Heading Into Christmas

    in Spring Weather Discussion

    Posted

    24 minutes ago, The Eagle said:

    gens-21-1-204.png

     

    The upper ridge to our south going absolutely nowhere. It is catastrophic for coldies and I fully expect at least 4 - 6 weeks from now to be knocked out of the winter in terms of any meaningful cold. 

    Unfortunate but we are stuck in a rut that is hugely difficult to see getting out of.

    I'd wait for NWP to get to grips with the SSW first as the idea is that the Azores ridge drifts northwards into Scandi and across to Greenland. So many notable UK cold spells began with a massive UK high. Patience needed yet. 

    • Like 1
    • Thanks 1

    Hunt For Cold: Model Discussion - Heading Into Christmas

    in Spring Weather Discussion

    Posted

    30 minutes ago, edinburgh_1992 said:

    And gradually we'll see the cold weather moved to mid January, then early February, then march and then winter will be over. 

    At least we had a bit of snow up here in Scotland last Saturday, better than nothing. Now time for the HP, better than rain and wind. Unfortunately in the long term it does seem like the Atlantic could return though, bringing a spell of mild and wet weather at the beginning of January with the AO gradually turning positive. 

    I really hope I'm wrong

    What exactly are you basing the Atlantic returning with a positive AO on?? Complete conjecture based upon background signals as the experts here have been explaining all evening. The pieces of the jigsaw may not fall in our favour, but there is absolutely no way of knowing that yet, until the SSW actually happens. Your saying that is almost as unfounded as someone telling us we're guaranteed the coldest winter spell we've ever had in January. Bottom line is be patient and wait to see how the pieces fall into place. 

    • Like 2

    Hunt For Cold: Model Discussion - Heading Into Christmas

    in Spring Weather Discussion

    Posted · Edited by ZK099

    17 minutes ago, Stuie W said:

    Still looks easterly to me, perhaps slightly NE. 

    Edit: as final evolution

    I'm unsure although SSWs usually do favour an easterly for us as far as I'm aware. GP an expert on this sort of thing though so definitely worth paying attention to. To be honest, I'd rather a Greenie bringing a North Easterly, been far too long since we had a potent one of those. Last prolonged one has to be 2010

    Hunt For Cold: Model Discussion - Heading Into Christmas

    in Spring Weather Discussion

    Posted

    5 minutes ago, Glacier Point said:

    Tropical modelling suggests a coherent MJO wave to enter the Maritime Continent during the coming week.

    twc_globe_mjo_vp200.thumb.png.4e1d9d33953a58b67bb679412aadfa04.png988072242_ECMF_phase_51m_full(1).thumb.gif.d527c4742cef7e768a50559fe0bb57e9.gif

    Week 2 forecasts indicate a widespread -ve velocity potential across the central and eastern Pacific, where SSTAs are well above normal and likely to favour enhanced westerlies (weaker Trades). There have been several westerly wind bursts this autumn and early part of the winter and I would expect this to be another one in evolution.

    time_lon_EQ_hf_sst_uwnd_anom_anom_201807_201812_2018121910.thumb.png.648006fead4695fde0b194a3b1780786.png

    So although the MJO signal is relatively weak, this will transpose onto a an El Nino low frequency base state. Total and relative angular momentum will as a result increase. There's no indication of deposition of westerlies via mountain torques over Asia, so a steady laddering up of angular momentum looks most likely. 

    That's a signal for phase 6 evolution in the first week of January.

    1599721510_janphase6.thumb.gif.a3eb9cfe4b8840117782c97693fe4b66.gif

    We should then begin to see westerlies scrubbed from the atmosphere over time returning the GWO towards phases 7 and 8 during week 3 (2nd week January, possibly with the MJO in phase 8).

    1236484031_janphase7.thumb.gif.01d72000f28ad035e18a2348845cbd86.gif696002106_gwophase8jan.thumb.gif.f295f4e49799f927c9b1bab4707fc59d.gif

    That could well coincide with the first lagged impacts of the stratospheric warming. With the net ENSO, GWO and MJO signals, I'd suggest mean trough solution across Scandinavia and into Europe with a Greenland type high is the most likely evolution. What do you say CFS ?

    wk3.wk4_20181218_z500.thumb.gif.93de0ae3512bb186bf277ef0f6fbb9b1.gif

    So you're thinking a Greenland High more likely than a Scandinavian High, bringing a northerly rather than an easterly? 

    Hunt For Cold: Model Discussion - Heading Into Christmas

    in Spring Weather Discussion

    Posted

    If I remember correctly, modelling was all over the place in February as well, just before the SSW. With so much going on in the atmosphere, NWP is trying to get to grips with what's going on. Expect a lot of fluctuation in model output. Probably more pertinent to watch the strat forecast over the next few days, then take it from there. 

    Another point- as someone else mentioned, we definitely don't want to see that cold go into Greece. As I've said, the model output is so volatile at the moment there's absolutely no point paying attention to it. However, when the block does set up, we really don't want the cold heading into Greece and this has been a common theme in recent years unfortunately. I'm not actually suggesting that will happen on this occasion, just something to look out for over the next few weeks because an SSW-related block can of course set up unfavourably. 

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    Hunt For Cold: Model Discussion - Heading Into Christmas

    in Spring Weather Discussion

    Posted

    1 minute ago, Stuie W said:

    Probably due to me not completely understanding the potential but I`m getting pretty tired of hearing about SSW/charts of SSW in this thread. There is a thread for that.

    Sorry not being grumpy but if we are talking about the models then unless someone shows the effect combined with a model chart then it`s a hard watch in here.

    Feel free to ask about the effects, or even look them up if need be. Fact of the matter is, is that the SSW will hopefully at some point have a profound effect on model output. SSW forecasts are also part of model output to be honest. 

    In a nutshell, an SSW either displaces or splits the Polar Vortex, while also causing a reversal in westerly winds to easterly, high up in the atmosphere. This opens the door to northern blocking, and can cause easterly winds to become established at our level. Northern blocking can result in cold weather somewhere at our latitude- we just have to hope it sets up favourably for the UK. We want to see this reflected in model output soon. 

     

    Bottom line, the SSW is so closely linked to cold hunting and model output that it has to be mentioned and brought into the discussion regularly. 

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