Uncertainty

The main thing is we are now seeing a massive, extensive Ural block being progged. This will, if it persists, cause an ssw in January. The mjo also looks really good for a blast towards phase 7/8 as @Dennis and @Met4Cast and others have been flagging. Good to see the ec46 have a go at this as it’s struggled with mjo amp recently. There are lots and lots of really interesting eps members but still no clear signal or direction for our weather at the surface in the extended. We need a lot more momentum to push the big Siberian high westwards though. We haven’t had many true winter (eg DJF) scandi highs with lows going under drawing in snowy easterlies in the last decade now have we?? Have we even had one? Thousands have been modelled and I’m trying to think of one save late Feb 2018? Jan 18 had one that was a precursor to feb but not really snowy. Finally Cansips is out tomorrow anyone else nervous lol

A surprising amount of GEFS members do just that Nick. At least 11 look to block off the Atlantic quite strongly at 150. My experience tells me @IDOis on the money but while there’s a chance… there’s a chance…

I think Arpege would send disrupt the first low SE and then ridge to the remnant scandi heights… We’ll never know but it’ll be interesting to see how many of the rest of the 12z go down the icon route…

Let’s hope the 46 has gone this wrong… it shows zonal oblivion right out into Jan! Tbf, it completely missed the current spell so not going to give it too much credence but as you say it stresses the importance of getting the next wave at decent amp…

Ec mean at 240. They’ll be quite a few members supporting the op. Euro low clearly present. The op, meanwhile, is a run of the year contender.

The GEPS very much sticking with the blocking being prevalent out to the 8th of December. As @Ali1977 rightly posits, the eps have edged colder and more blocked. There is no +nao cluster at days 8-10 (and even for a few days beyond) with a euro trough still in play snow would be plausible for all areas according to the eps. Going off the extended eps, the end of the weekend of the 8-10th is when the signal for a +nao really develops. With the next tropical surge in sight, this may only be a temporary shift. There’s also no rampant SPV to drive an instant end to the blocking, I agree a scenario like the ecm op would be somewhat fortunate but on the other hand it could simply be reflecting that the cards are stacked towards the blocking deck this winter - just like the seasonals have been insisting - and that we should not dismiss output like the geps above which stretch this cold spell from a sharp snap to a considerable and memorable spell…

13 members go for a reversal by early Jan. The 8-10 period is a long way off in modelling terms and the ecm hasn’t exactly been prophetic with this spell. If the block does break down days 8-15, which today’s trends have edged towards slightly, we would only be returning to the forecast we thought we were getting for December. The big differences now being: a) The SPV is far weaker b) We have seen already the jet is behaving strangely The next pacific wave should be coming through in mid December, combined with the weak vortex, that’s a thrilling place to be before winter even actually starts! FWIW, the NAEFS still look interesting out to the 9th of December The eps have 3 clusters in the extended: - Continued southerly tracking jet under the Greenland wedge - flat - Strong high pressure over the top of the country As a few have said, the rather profound momentum drop / unfavourable cycle of the mjo probably make option 2 increasingly likely with time. But how long the transition takes and, crucially, how long it lasts, are still completely up for grabs. I think the regimes demonstrate this quite neatly! By early Jan, only around 20% are +nao. I think we’re here for the long haul. Next week is just the beginning! Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4959287

Yes I was thinking that. I remember it did well with the halfway house of the initial blocking between the absence of the ecm and the overzealous extremes of the gfs and gem. Shame it doesn’t go to 240.

13 members go for a reversal by early Jan. The 8-10 period is a long way off in modelling terms and the ecm hasn’t exactly been prophetic with this spell. If the block does break down days 8-15, which today’s trends have edged towards slightly, we would only be returning to the forecast we thought we were getting for December. The big differences now being: a) The SPV is far weaker b) We have seen already the jet is behaving strangely The next pacific wave should be coming through in mid December, combined with the weak vortex, that’s a thrilling place to be before winter even actually starts! FWIW, the NAEFS still look interesting out to the 9th of December The eps have 3 clusters in the extended: - Continued southerly tracking jet under the Greenland wedge - flat - Strong high pressure over the top of the country As a few have said, the rather profound momentum drop / unfavourable cycle of the mjo probably make option 2 increasingly likely with time. But how long the transition takes and, crucially, how long it lasts, are still completely up for grabs. I think the regimes demonstrate this quite neatly! By early Jan, only around 20% are +nao. I think we’re here for the long haul. Next week is just the beginning!

What an ending!

What a morning! The low is heading… South! Gem UKMO Icon Gfs - showing we don’t want the low too far to the S, if you want a snowstorm that is! After that, the mean high seems to be rooted in the urals, with more of a wedge extension to Greenland. If we want to zap the strat too (and we do ) then we want a sustained Ural high / Aleutian low combo for as long as possible. The gem ens show this rather nicely The GEFS has more emphasis on the Greenland high, though I couldn’t complain were this to verify either! So in short, if you’re just waking up, a fantastic morning for short and perhaps longer term cold prospects!

Oof. Still there from last night and now stronger. We’ve talked about the fabled Canadian warming for ever, so it will be awesome to see one actually verify and what we get after!

@Tamara thank you for your optimistic post it’s more exciting to me than any model run! @feb1991blizzard I was wondering when you’d return. I see eps twisted your arm… Now that the blocking looks highly likely we do need to turn our attention to the synoptic we’re actually going to get… without being too negative there is always the risk of: west based -nao trough gets stuck over us = cold rain Too much snow that netweather sever crashes Last year we were had the cold but no precip, this year the mean high looks less west based. There are still a few days to go to see if we’re going to get a snowy (or multiple???) scenario/s. But that’s the fun bit!

I wonder what it said a few days ago??? Hmmm??? Oh wait… that’s YESTERDAY!!

Also: Tripole Fading +IOD Probable moderate Nino, developing modoki Aleutian low EQBO Mjo coming out of 8-7-1 and forecast to return later in Dec Phenomenal, consistent, persistent seasonal modelling support for anomalous blocking Blocking appearing Even a ruddy Canadian warming in the pipes! Have I made my case yet??

I’ve been saying since summer that the seasonal modelling vis this winter has been different. I know we’ve been accustomed to mild winters, a rampant jet, disappointing and despairing 0z runs and over amplification from (let’s face it) all the models since 2013… but… the question we really need to ask is: what if the seasonals were right? Has the touch paper been lit?

Now we’re talking, a rather anomalous 1025mb high with an easterly flow on the mean… Turns into this at 300! Further ahead, the possible return of Ural heights Is perhaps even more exciting.

It’s hardly Dec 21 or 22 or Jan 19 when the toys really came out… Anyway I really enjoy Jam’s posts on Twitter I think it’s a bit of good natured banter I think we only really get disappointed when there’s x model agreement and it falls apart 3-6 days out. This time there’s never been any agreement and we’re collectively trying to figure it all out. I actually think the analysis - especially on the winter thread - has been really good. We have most of the big guns: Nick, Tamara, Matt, BA, Alistair, Aaron and the rising stars such as my good pal @Kirkcaldy Weather on point and we have lots of new faces adding positively to the conversation. I’ve said it before: we can take quite a bit of stick online - the only way to alter that is to increase the quality of our analysis and act with decorum and good humour. (Eg not seriously declaring winter’s over / getting all ‘told you so’ if the 18z is flatter…) We also have to remember that the ecm, while doubtless the strongest model, is wrong a lot. Tbh I think we’re doing better as a collective this year and we’re all looking forward to see how this potentially exciting winter, and indeed this particular spell, might turn out. In terms of where we are at, the signal for an Atlantic ridge at day 10 on the eps has increased since yesterday, my guess is it will improve further this evening The GEFS have been really keen on this day 8-10 blocking, regardless of what happens in between… tonight’s big 3 are in more agreement about that than they are about days 5-7! GFS GEM ECM And as for the ever reliable ecm, I wonder what it showed yesterday?? I’ll get my ski coat!

I’m a big fan of telecons generally - but how many times have they been massively favourable for cold and the Atlantic has won out? Occasionally the reverse must happen. Equally, there are variables that we understand very little on this forum but in reality are big drivers (big orb in the sky?!?) Then again, maybe the gfs suite is just very wrong. The gem has backed off completely, along with the JMA and the ecm. So it’s still just a fantasy, but you have to admire the persistence of the gfs. It has trumped the ecm more times in recent years than many of you give it credit for and it will again. The hard question as ever is: is it correct with this one? I personally think it is seeing something and the more UKMO ish solution with an AR but not a full blown greenie is probably the call. But wet and windy and very cold take 20% too. Glad I’m not writing the 8-15 dayer tonight…

One step further than the gfs might lead to something like this… Overall the 18z GEFS does look a bit more amplified still than the 12z. However… Plenty of members have that pesky shortwave spoiler though so it’ll be a nervous watch in the morning….

I think that’s close to a tripole. Could be a cold factor going forward. Plenty of eps members look really interesting at day 8-9 but few go on to produce anything noteworthy. Then again, the eps have actually been behind the eight ball on this one. Worth looking through the 18z GEFS to see how many members take the jet even further n than the op and thus produce a more stable high. The thing that concerns me about the gfs type solution is it relies upon a drifting Arctic high to connect with the Atlantic heights the former of which has let us down so so so so many times and in my experience they usually fall away towards Tibet. Still, need to a keep a close watch as mr @ICE COLDrightly points out. We don’t want to sleepwalk our way into a cold spell now do we?!? They’re usually good for the eastern seaboard not us…

Interesting Pub run…

The 12z GEFS is more amplified upstream than the 6z I imagine a significant number will follow the GEM route. Im still extremely cautious about this amplification. The UKMO is not remotely interested and ec has backed off. If the latter returns to the fray tonight then the eyebrows will raise like the prognosticated Atlantic amplification!!

One for the archives that!

This run has more upstream amplification… the polar profile is going bonkers too! The shortwave near S Greenland might scupper it this time, but scene to the NW is remarkable! GEM about to go full Monty