Uncertainty

Does that infer BA that the split is between those two vortices e.g through the NA/NW Europe? More GEFS members going for the a reverse too, almost half and a cluster goes really deep!

Well TI its seasonal iteration gave us the most blocked pattern in its November run before it got cold (warm?) feet in December. If the general output for the next 3-4 weeks comes off as the anomalies suggest and Feb doesn’t go all 2020 on us then that run might well have been spot on.

The extended JMA builds HP through the UK from the SW Meto/BBC extended into New Year suggests this possibility. Main alternative at day 10 - 11 seems to be another diving trough ala ECM/GFS Either way there does look to be a second surge of amplification after our Dec 27th event. The location of this amplification may well be our next medium term ‘topic’ in the coming days...

Only 25% +NAO through late Jan tho BA. V low for Jan vs climo One day in Early Feb goes down to 15%! The week 6 mean is a bit meh but looking at the regimes are some really zonal members watering down the mean? Or is there such a huge spread of permutations that the anomalies are weak?

Yes what a change from the usual furnace fodder late Dec/Early Jan has thrown at us recently. This unremarkable chart, is the coldest Christmas Day for 10 years! Our bar is rather low folks!

V true Scott but it’s the trend vs last week that’s excellent. This first ‘bite’ isn’t nailed on. We don’t have a majority of GEFS reversing yet either. This was the 0z I doubt the 12z has more. Buuut, that second +EAMT should sink the ship, or at least keep it weak. Anthony Masiello on Twitter who is almost prophetic at times has been touting the MJO to head through the Western Pacific by Mid Jan. It really is a great position to be in Stratosphere wise. Personally as I’ve said I’d rather have the backing of a cluster of Stratospheric experts than a cluster of EPS members. We have the impacts of the past e.g preconditioning through the Russian high, now these wave breaking events and in the future we’re looking at another big +EAMT and a renewed push from the MJO. Its not a golden ticket tho, Jan 2015’s split looked perfect for us but where’s the historic vids for that winter? But given the receptivity of the trop to blocking this winter thus far I’d absolutely, categorically rather have it than not.

Yes Tim but that’s week 3! I was referring to week 6 and so was the precip anomaly. I was hypothesising about the models first take on the post SSW downwelling and it’s effect upon the trop.The pressure anomaly was weak but i thought it was interesting there was a slight signal for drier weather to the NW persisting even at such a long lead time. Regardless, that week 3 chart is a corker!

The Week 5 and 6 patterns don’t look like a QTR to the poss SSW but but they don’t look full on zonal either, I’m guessing there’s massive spread. NW of the UK still looks drier than average at week 6, even though the 500mb anomaly is non-descript.

Down she goes! Mean below 5 m/s!

ECM mean at day 10 looks a sight upgrade to me, higher heights into Greenland and a tad sharper with the mean ridge, 12z: 0z The Euro trough also slightly further SE. GEPS have been the flattest of the big 3 in recent weeks, not today. A simply incredible anomaly here. Not gonna get flustered by ECM ops at day 9 / 10 in a pattern it struggles with. PS first glance at EC46 looks really, really good till mid Jan!

No Feb neither do I but I think the will it / won’t it split aspect of this warming remains to be seen. The ensembles (which unlike last year share the FV3 core’s extra stratospheric revolution) are still toying between whether or not to initiate that secondary warming. Many don’t, but this is still an evolving situation beyond the expected Siberian warming in the days leading up to New Year. The good news is that the ones that have the 2nd warming over the last few days have the split in what would hopefully be a great position: over the N Atlantic. This is the trend I would love to see develop over the next few days. Onto the trop and I think the GFS needs some credit here. The EPS and GEPS have been 2-3 days behind in firmly spotting this enhanced Atlantic amplification. Though in defence of the EPS this signal has been there throughout including on the 46, there’s just been a few more wobbles than the GFS suite. Overall I think this pattern has been quite well signposted, here’s the EC46 anomaly from the 3rd of December: Tonight’s run will be very informative, not only for the short term pressure distribution but for the ECM’s take on stratospheric developments. If a)it is seeing an SSW and b)it downwells the -NAM to the trop then this should be evident in the latter stages of its output. Even if, as I still suspect, the split is delayed vs recent GFS predictions the continued presence of the Siberian cold/high heights will continue to pile pressure on the SPV.

Glosea didn’t get the memo! Outstanding seasonal model... please be wrong this time! I‘d be so chuffed if the great minds on this forum can outthink the supercomps. The signs have been there since August at least. You said it yourself CC many times. tbf to the CFS many individual runs have gone with it but the mean can’t help but revert to climo. @Scott Ingham that’s beyond my paygrade but the persistent heights in that region are doubtless the big NH story this year. I’m sure there’s a link back to that crazy warm period they had In the summer (they even had a level 3 estofex for supercells near southern Siberia at one point) and our current stratospheric position. Their persistence through November was surely the critical factor. Siberia is now truly bitter - as Japan has recently discovered!!!

Beautiful indeed! It’s such a contrast from last years well oiled machine. This +EAMT is quite something, here at day 11! How stunning to have a gigantic Siberian high AND a huge -NAO concurrently.

Good evening all. That’s the GEPS at 300hrs. WAT. Those euro heights are in a great spot. Loving the upgrade on the EPS tonight... On the latest GEFS we have a mean northerly at day 9: looks neither too Far East nor west to me. Great angle. Here in NE Cumbria the Solway negates the snowy potency of most NWerlies but a true Northerly with embedded troughs and low thicknesses might be a different matter... Weird to see ECM following GFS but it isn’t the first time over the last year or so... The extraordinary persistence of the GFS In predicting this pattern is a real coup for the FV3. I can’t remember a non zonal pattern being this consistently modelled from day 13-7. Lets hope it’s right about the SSW in the strat too! However, The 12z, whilst spectacular for reversal speed, left a daughter vortex in the Atlantic. These have been sour for us in the past, especially two winters ago. I would rather have a 1984/1985 situation where the secondary warming is in the Atlantic, we might see this on this run... Looks ideal! The 46 tomorrow will be vital, hopefully a lot more members back the GFS and go full reversal. I still think the GFS is jumping the gun a tad but it looks genuinely likely we’ll see a major midwinter SSW come the middle of Jan. Ive mentioned frequently that may faith in the SSW/subsequent downwelling effects etc have been dampened by strong positive NAO touted by the seasonal models. This time they have seen most of the developments we have over the last month. Hopefully they flip big time and we can begin to contemplate the first cold winter for 8 years. PS I noted today that the meto 30 Dayer backed off the return of Atlantic mobility completely. No reason to disagree with that based on this evenings output

Coming into view on the JMA now. Some level of warming is now highly likely as the precursor patterns have already occurred. Answers to a)how strong b)what type of SSW c)long term permutations in the troposphere... are presently unknown...

That 1st sentence says it all. “The last time we had a Greenland high” A decade! Only exceptions in Winter I can think of are March 13 and 18 (except neither were in Winter lol). No wonder the models are bickering over it, it hardly ever happens! JMA looks a bit further west at 192 but has the big Atlantic ridge into Greenland. The Vortex segment then heads Merrily SE Producing this at day 11 Onto the 18z GEFS the mean heights are stronger to our WNW but slightly less amplified overall. Suggests to me that more members going with the amplification in general but less to the extreme extent of the 12z. 18z first: This does mean the mean trough is back a bit further East which brings more areas into play for the initial plunge. I really would love to see this evolution come off in deep mid winter. Even though the uppers aren’t sensational the low thicknesses and heights should deliver plenty of snowy forecasting headaches.

Yes and I’m also liking the Atlantic warming meeting up with it, looks like a good location for the split if there is to be one. Let’s hope it continues over the next few days. My point was more of an observation of a trend to reduce the peak warming temps, we wouldn’t want this to continue as there wouldn’t be enough heat to trigger a major SSW. But I agree it’s great to see the FV3 core going for a reversal at a relatively short time frame. This was always touted as one of the advantages of the new GFS and hopefully we’ll see it shine here. It Just feels a little too early to be sure on this yet. Would need to see a majority of GEFS / EPS members going for it to to call it and that’s just not the case at present. Would be delighted to be wrong!

That’s right BA. Even yesterday there was still some support for genuinely flat solutions with no trough dropping down through into Europe at all. As @Daniel*has posted the EPS post 240 actually drive the ridge northwards back towards Greenland. 7 or 8 members produce a stonking Greenland or Griceland high and downstream trough over Europe. Perhaps 20 have mid Atlantic highs of various latitudes; most producing chilly but not stellar Northwesterlies. Some remaining members have a UK high with the jet over the top. Again, as earlier in the month, barely any are full on flat zonal. Cluster wise, there isn’t one cluster I wouldn’t snap your hand off for in a normal year, but seen as we’re in with a chance this year, it would be a shame to see this month’s Synoptics fail to deliver a decent snow event. Cluster 1 look good early and late. Cluster 4 late on looks tasty too. The GEFS mean looks great but there are quite a few members that follow the op and drop the trough down west of the UK leading to a frustrating pattern with a west based -NAO and rain for most. On the other hand, there are far fewer flatter runs hence the more amplified look to the mean. The EPS for me are similar just delayed by a day or two. As for the Strat I get the feeling this wave 1 attack, whilst potent, may not provide the killer blow quite yet. There was little concrete suggestion of it on the 46 and there’s nothing at the end of the Meto 30 dayer that you might expect if they were convinced an SSW was imminent. The peak temperature of the warming on the GFS has also trended down on the last few runs. From the 0z no reversals but lots of weak, stretched vortices which should allow the present phase of trop amplification to continue. Not sure it will last much longer than mid Jan though, I’m still seeing Ural blocking through early Jan so hopefully it’s on borrowed time. In summary loads to be excited / fascinated by at present, couldn’t be more different to many previous Xmas periods. At least, weather wise, we might have something to look forward to over the coming weeks.

Not sure Mike, but the wave 1 attack is going to weaken the vortex from 21st onwards then lo and behold trop amplification flourishes. Not sure we can call it a QTR but it’s not a coincidence. None of this would be happening if the canonical late December vortex intensification was occurring. That’s for sure. Just putting it out there but this iteration of the GFS (and now it’s ens set) using the FV3 core was never, ever this solid about last winters botched warming. It has been on this for days now in the sub 2 week range, if it’s still there in what, 2 days time, is it happening? Will the bigwig boys and girls in Stratospheric Wx twitter land call it? Could we know by Christmas Eve that we’re getting an SSW for V early Jan? Its literally the only thing on my Christmas list! Apart from socks of course, The joys of being a dad lol.

Great stuff pal. I remember in November you were praising the Urals blocking for its future gifts, not for the monotony it provided at the time. Our last few Novembers were cold and where did that get us? I think November is the key month for Eurasian snow cover advance. This year October was unremarkable but it really kicked off in November in tandem with the quasi stationary block. Siberia finally cooled off the back of record warmth of this year and this very much didn’t happen last year. This in turn has provided a key part of the feedback mechanism to induce the big heat flux into the strat which we are now seeing. The question is, *if* this does happen, why didn’t the December seasonals see it? They must have had the Russian high in their starting data yet they’re only slightly better than last year’s garbage. Or did they see a weak displacement / reflection event combined with a strong Nina which flattens everything off? Those seasonals are the only nagging voice in my head now. I’d love for them to be proved wrong. Not only would it be a victory for human forecasting ingenuity but it would free up the future to intrigue, wonder and debate. Knowing the future for certain would completely spoil our fun!

Yes the mean is sharper with the amplification and edging closer to N than W with the flow. I’ll report on the indv members soon, it’ll be interesting to see how many evolve like the op at day 9/10. Not too many, given the spreads. But evidently many of them go cold and stay cold. Latter stages of the GEFS show no let up in the inverted climatology pressure pattern. Ural blocking, high to the NW and the jet into the Med. GEPS is broadly similar but not as strong anomalies. Looks like an April chart

You did say that might be the next stop for the UK high Scott, do you think the big EA mountain torque event is driving this allied with the vortex trending weaker? Looking at the output it seems like the Arctic high has a role too, it seems to ensure the low to the NW has to go South / SE The lack of a strong PV over Greenland then allows heights to fill the gap to the North leading to a cold lock in for NW Europe. It actually makes sense with the background signals! It’s actually been signposted by medium/long range modelling for weeks! Now all we need is for it to actually happen!

The big wins tonight are: - The Xmas day Northerly has been sharpened up and will bring 60million people in this country not to mention NW Europe some frosty and *possibly* snowy cheer on a year in which they’ve been battered to oblivion - The major models have not gone flat with the post Boxing Day Atlantic amplification, they have all gone for variations on the today’s broad GFS theme, the details of which are unknowable yet. On the negative side - They have still not decided upon the fate of Wednesdays low (or not to low). Fair play @nick sussexyou said it wasn’t relevant to the overall pattern and you’re right but it’s still Important in forecasting terms for the sodden south west. However should that Wednesday low come to pass, some back edge snow for Northern England looks possible: I reckon the ECM would show something similar, hopefully someone can rustle up the charts! Oh... I just saw the ECM day 10 WAT GIVE IT TO ME. I don’t care that it’s an outlier (it will be). I just want it to happen

My thoughts all along mate. We now have: - Weak vortex - Weak Nina - Weak solar December cold punt then split SSW for the win. It’s always been the jackpot scenario.

Georgina - It (The 12z GFS) is most Definitely a stonker. It has a cold polar northerly with sporadic snow to low levels, it then has a snowy low coming in from the east into cold air later in the run followed by a cold high to the North of the UK allowing for good longevity in the pattern. It also shows a significant warming in the stratosphere which *may alter the course of the rest of the winter towards a colder outcome. The terrible aspect is because the lead time is out of the range of reliable prediction it’s a fantasy at this stage hence many members are nervous due to countless disappointments in here past. Right now though, taking the models at face value, it’s a very plausible outcome. Hope that helps.