Uncertainty

Well we finally a new GFS para to digest and whilst no BFTE it’s very wedgey and ECM like and snowy again (especially for central and southern areas) from next weekend onwards These battlegrounds kick off from day 7 so it will be very interesting to see if the colder earlier trends on the para/ECM have some validity.

The blocking signal is still there, the location remains a mystery other than ‘probably to our North’ Uncanny resemblance? @IDOI appreciate your objectivity and your methodology, these charts will be moving into your interest range over the coming days but what’s your take on the extended situation? the GEFS have been reasonably consistent towards the back end and are beginning to look a bit like the 46 weeks 2 and 3. Latest EPS probably have that high anomaly further East but there’s still way too many with a weak irksome trough to the west to send the de bilt graph tumbling. The GEPS are getting more blocked from a low base last few days but the mean trough is still in the wrong place (to our SW). Ec op gets cold much quicker like last night but given it’s tendencies we can only acknowledge it rather than believe it. 0z 12z However 3 EC ops in a row with the same pattern always gets my attention so let’s see where it’s at tonight. Nothing this morning to alter my thoughts from last night e.g. more blocking, less west based -NAO but still no clearer on beast / no beast. If, model watching wise, it were to be clear and obvious like Feb 18 then we need those means to firm up on an easterly very soon indeed. Sadly it doesn’t quite look like that’ll be the case so it’s going to be another nail biter I’m afraid!

Next items in the countdown list: - - full day of GEFS runs progging this anomaly, perhaps up to 1025mb to our N/NE - - An ECM Day 10 stonker - - Strengthen and Transfer the high anoms on the NOAA chart Eastwards and firm up on the euro trough - - More specific mention of E / NE winds and swooping of ‘wintry hazards’ to snow on the MO 16-30 dayer 3/4 required at least to move onto the next level. If We get these by Monday morning and the 46 is still keen then we might move back to three - four new threads a week! And I can reveal the next 4 elements of the countdown checklist!

Haha there she is lol. feb am I right in saying this is our first mean Easterly from a +BL this winter, we’ve had some cracking means but generally all from the north. Definitely one of the collectors items I’ve been looking for as we start counting this down Grim to think it’s still even 5-6 days from even coming into view on the UKMO. So many twists and turns to come and hurdles to cross, even after that point. Still , The good Mr Hammond was clearly seeing this continental feed and right now it’s becoming more and more likely.

This evenings perturbation prizewinner: Marginal uppers... In Guernsey!

As I said before, day 12: Blocking = likely Amplitude: Big time Location: More runs needed! Though worth noting the trend today is more Greenland than Scandi...

Absolutely but I imagine the vast majority of those winters didn’t have two technical strat reversals within a month. This is an almost unprecedented event (Judah Cs words, not mine) and given the tropical forcing working concurrently: Forecast Nina composite for Jan, Feb GEFS day 15 forecast Then this next ten days of model watching will show the charts you describe, and some will show the cold progressing far further W than the Norwegian coast. But, of course, like in Jan 19, or countless other times, it can all seem perfect, tick down to 120, and then all fall apart in two sets of runs 6 hours apart. Let’s face it, that happens 9/10. Divide the amount of times you’ve seen screaming snow by the amount of times you’ve seen screaming snow charts and you get a sad, sorry little number. I can moan as well as ramp by the way Nevertheless. all i’m saying is given the teleconnections and, increasingly, the medium term modelling, we have to pay attention to the output over the next few days and put aside the (many) disappointments of the past and view it objectively. For me, right now, it’s 50/50 we get a memorable cold spell early Feb. We could equally get a weakly -NAO and a weak trough to the west, the big 3 ensemble sets all have that possibility.

Wow back end of the EPS big time blocking. More of on East based element to the -NAO. Will be some very cold members: U.K. high, Scandi and Greenland all in there. Mirrors extended GEFS signal, perhaps stronger. Best set of the winter for nationwide cold Synoptics, though no clarity yet on the location of the block, but it’s coming...

Yes, I mentioned this in my earlier post. I imagine the dynamics of how well it’s able to cut off tropical convection whilst it is weakening are extremely complicated and I can’t profess to have more than a rudimentary understanding of the matter. What I can do though is see a trend and this 18z GEFS is the first with real mean ridge visible on the pressure charts, building just west of the UK here not just the phantom reds to the north in the anomalies...

This perturbation has it nailed! You just know what’s going to happen on the 0z though don’t you! TBF there are lots of good ones in there maybe 50% look like they would go blocked, northerly U.K. high or snowy battleground. That’s a signal and we can’t ignore it...

I think the amplitude matters too Don, the Nina imprint might weaken it so it’s not strong enough to really shake things up in the NA sector, 2018 had a record breaking phase 6/7 push that IMHO was as big a driver for the blocking as the split in the strat was. As I say if the reversal + a >1 amplitude MjO 6/7 wave verifies then the 18z is a good manifestation of the probability space. Big if mind, especially as you say the Nina factor which Marco himself is still referencing...

The big hitters I look out for are a weak vortex which we have and a good amplitude mjo wave into 6-7-8 which way might soon have (and we have not had this all winter) The latter gives you the momentum boost to wedge heights north to meet the Arctic blocking seeded by the weak vortex. Many legendary midwinter spells have started this way (think Feb18, Jan 47, Dec62 etc) not saying for a second this could be comparable I’m simply saying look out for a wedge of heights launching (or as Gav P aptly puts it, getting ‘sucked up’) through / near the UK towards an Arctic area of high pressure. You can see this on the 18z Actually this is v similar to the 12z and a small but growing cohort of eps / GEFS members. Cold fans need this signal to grow now, flourish even, with few slip ups, for at least 5-6 days now until we see a mean easterly on the charts. Then we can start popping the corks (obviously not lol I haven’t forgotten Jan 19) but we can then start to look to get the UKMO etc on board and really get excited. This is all a very tall order yes but if it’s what’s actually going to happen the models will see it pretty soon they won’t miss such a hemisphere defining event. Next thing on the checklist is for an ECM op to go for it, the GEM has toyed with it but we need the former to start sniffing it out in the coming days. Then the nail biting can truly begin!

Thinking of throwing in the cold towel for this winter? - Clear signs of convection moving into the western pacific - Weakening La Niña signal - The best set of ensembles for favourable Northern blocking in the day 10+ range for quite some time, building upon a very blocked week 3 EC46 - This 18z might not get there, but It looks like it’s toying with the idea of Scandi heights. I have a feeling quite a few runs will get there in the near future. The continued weak vortex state leaves blocking patterns open to development, we just need a trigger. Hopefully this mjo wave upgrades higher towards the 6/7 phase space over the coming days. If it does, combined with what looks like another technical reversal, then that’s a very good position to be entering February with, regardless of the disappointment this fascinating, generally blocked winter has brought to many so far. Lets be honest, if we had that mjo forecast combined with an upcoming strat reversal in a winter that had seen little blocking up to this point then this forum would be a lot busier. Unfortunately, the mode bias of this winter thus far has been to downgrade great charts for U.K. cold at day 8-9 so it’s understandable that things are quite tonight (present company excluding the excellent @Griff). For me, the background signals are better now than they have ever been. I’ve been stung so may times even just this year by blocking fails that I’m not going to get excited by this but objectively, Scandi heights at day 10-12 seems a logical progression. Its a real shame the parallel’s gone all inconsistent with its data release as it was quite consistently showing heights over Scandi. Let’s see where we are by the end of the weekend... snow chances for some, North and South in the meantime.

Yes Roger I had a look through the EPS members for Thursday night, a significant number have some huge snowfall totals by Thursday in and around the arc you mentioned. This is a fairly representative example. Some are weaker but there are quite a few even more extreme examples than the above. A small but noticeable cluster have a more diffuse area extending much further south, around central England. I am not foolhardy enough, and nor are most of you, to take these depths seriously. But the sheer number of members - id say nearly 50%, including the Op that are showing this event ( the scenario Roger has described) would translate, if it were to persist into Monday morning say, into the introduction of a dual rain / snow warning to account for the risk of a disruptive rain / snow and perhaps even wind event midweek. Into the far reaches of the EPS, Northern blocking remains the major player, but most members feature a low somewhere near S U.K. and therefore the opportunities for further high impact rain, snow and wind will persist. Very little appetite for last February’s hideous Euro high / Atlantic storms scenario in the EPS. And finally you simply can’t categorically say this SSW is in the 30% which don’t bring us cold as it hasn’t even finished reversing yet. If @sebastiaan1973is right with his slow -NAM drip theory (due to Euro blocking at 5 days before SSW onset, which I personally feel it was as we had a Scandi / U.K. high around that time...) then we need to wait until mid Feb at least before calling time on this event. Indeed it is already having a fundamental effect on NH patterns presently, the flow from Siberia to Florida attests to that. Alas, as some would say, it has handed us southwesterlies, but the persistence of its influence over NH dynamics is still very much open to debate and, if the EC46 is to be believed, then that persistence will last well into February.

A step forward for cold fans this eve after some significant leaps backward in recent days. Anecdotally I’ve been reasonably impressed with the para... it’s still not a patch on the ECM but it *seems* a tad more consistent and less prone to volatile swings. The UKMO has a stronger and slightly Closer high to the NW and has trended the nasty midweek low to a more southerly track. This makes things les clear cut vis precipitation types... In fact, is snow on the northern edge of the midweek system (or on the returning occlusion as it pivots across N England alla ECM) out of the question? Para Op GEM Some interest for C/S England there perhaps... Shorter range models coming into view now too... Arpege ECM, never to be trusted with precip types, was even more outlandish with heavy snow as the low pivots through Scotland Icon does something similar I realise models can overdo snowfall in these scenarios but as you can see it’s well supported... if the southerly trend continues there could be a very significant rain —>snow transition for some. The para shows all is not lost in FI as well so keep those toys under the pram cover for a bit longer yet folks!

Mean is more amplified and closer to the ECM. Wonder if this set will sustain some of the amplification... Still a few days to go till UKMO range but good trends this eve...

Of the Glosea run no, was just asking for your prediction as to whether it might flip From it’s Dec +NAM forecast, given the rest of the seasonals appear to have...

Glad to hear this Steve, the wedge was a beautiful but unlikely option but the day 8-9 trend was a day 14/15 day trend 6 days ago so it’s still counting down... Also, that ECM op has 1030mb surface high over Scandi and it wouldn’t take much for that link up with the AR and the crazy 850s to advert westwards: that’s the key to the puzzle we’ve been missing so far this winter... Your thoughts on the GLOSEA 3monthly run on Monday? The others have flipped, will the UKMO make it a full house?

Yes you’re right both GEFS/GEPS go stormy towards the end but neither of them picked the amplitude at day 9( if it happens). People have their preferences but for trends recently I look at the EPS, the extended para and strat dynamics which indicate that the reversion to wet and windy is possible as is an extended cold spell with big time N blocking as do Exeter fwiw. Not seeing a BFTE with a giant Scandi high yet despite the papers and It’s been covered in this forum that the 2018 event was seen 15days away by the ensembles so we haven’t got nearly that much confidence yet.

Moving away from the medium range shenanigans for a moment... The narrative I have been pushing all winter, e.g. the December seasonal models on trial... has its next chapter today: Our next suspect, the CMCC... Here’s the latest, if you’re feeling a tad blue, this ones for you! The Dec update was practically the same, except, er, the colours in the Atlantic and Arctic were swapped Thats CMCC, ECM, Meteo-France, CFS (For Jan), DWD and CANSIPS, all flipped from a moderate +NAM to a hardcore -NAM. Conclusion: They’ve seen the SSW and they see a major downwelling -NAM . Caveat: A similar phenomena happened in Jan 2019 and the Azores ridge completely blunted the signal - so the above is of course not a given. After all, although they *might* have been wrong in December, who knows, they might be wrong about being wrong! Still, the first 10 days of Jan have gone to the new plan quite well so far, how about the latest day 10 anomalies? A pretty good match! It was only really the UKMO that bought us an unlikely quick ticket to cold, yes the uppers were ‘oven ready’ in the continent but it was always a punt for anything before the 19th. The scenario we’ve been tracking remains the ridge heading north day 9 and this hasn’t changed, as I pointed out yesterday, this has been hinted at on the GFS and particularly the para for nearly a week now. They nailed the Bella / ridge scenario and that got us two weeks of cold weather. Given the seasonals and the SSW, there is every reason to think that they’ve got this one too.

Good evening all Around a week ago I posited that we were in for a short mild spell which would be but a prelude to the next exciting phase of what really has been a fascinating winter of NWP analysis. The following GFS 384 chart was used for illustrative purposes as to how we might get there... The recurring pattern of the winter, heights scrambling towards Greendland and a trough angling down through the U.K. into Europe. This solution still very much in evidence on the models, the day 9 ECM for example This could lead to a cut off Greenland high. With the jet undercutting and a high risk, high reward scenario following, GFSP goes along these lines Pleasingly, the flatter mid term solutions such as the ECM op from 2 days ago are less prevelant. It’s hard to separate happenings in the stratosphere from this shift in trop output. Would we be seeing GHs and charts filled with anomalous wedges with a raging coupled vortex? Of course not. Are we seeing them due to a downwelling wave? I’m not sure... Inconclusive, but that’s one for the experts to dissect. We’re Interested in the very bottom right of that chart, and the trend at present is that of a lightening of blues. But there is a 3rd solution. That is, the wedge of heights from the N around Tuesday that has been predictably poorly modelled could establish to the NE and send the Atlantic energy underneath as early as a weeks time. The UKMO and JMA manifest this evolution, but it’ll need to be there in lights across the board come tomorrow evening to have any chances of verifying. But 2013 tells us it’s possible, so one to keep an eye on. A quick look upstairs tells us this is no ordinary winter A mean reversal for the duration. Potentially 20 days easterly and possibly beyond, with a really strong signal for another full on SSW in the extended. The net effect of this extended reversal will be felt across the hemisphere for many months. And what then of the mighty seasonal models, the motley crew of humbugs who wrote of winter before it had begun? Well it doesn’t look good, the votes are still being counted, but the early polling is heralding a landslide defeat. ECM FMA from Dec run Latest run A caveat here that some members of the Dec EC run did see the SSW, hence perhaps the no signal over Greenland and slight encroachment of lower heights near S England. Always a model to into account, whatever the lead time. Meteo-France JFM from Dec run Latest Oops Now, DWD, only temps and precip anomalies are available on their site, but a glance at the latter tells you all you need to know... Dec run for FMA Dry anomalies over iberia, not great. Latest run Dry to the N, wet to the S. Jet equatorward and cold/snowy possibilities you would imagine. Even the grinch fancies a bit of the January blocking action, reverting to type in Feb Cansips has similarly flipped. I will reserve the final sentence for the December seasonals until the vanguard GLOSEA run shows its final hand, but it looks like curtains to a strongly westerly winter to me. Looking forward to this place getting busier in the coming days and weeks!

Is this what you envisaged in your prophesy BA? Surely there’s no way that ridge would gain that kind of northward traction with the MJO in phase 3 without some semblance of downwelling? Then again, the Jan phase 3 Nina composite does perhaps allow for a trough stalling to the west... Combine this with aforementioned downwelling and the hints of that ridge on other models... perhaps we can give this day 10 EC slightly more credence than usual???

You won’t be the only one interested in this my friend! Excited for the 240!

Near vertical tilt to the jet... We are trending towards another ridge building North day 9-11. Current launch site looks just west of the UK. Strengthen this signal a bit more and we can start thinking about where this ridge is going...

The diving low ship long ago but the trend for heights building through or just to the west of the U.K. towards day 10 continues to build on the GEFS 12z 6z 0z was flatter still. GFSP demonstrates this neatly with a big rise in heights NE through NW of the UK This is not a ramp, I have for for many days been resigned to the brief flattening of the pattern in the mid term and, discounting GFS nonsense, the models have been too. I believe we are looking at a well forecast delay, not a cancellation of the cold. Remember the Feb 2018 SSW was around the 8th and the snow didn’t really kick in on the East coast until the 25th so that’s 17 days in what was accepted to be a QTR. We have to be patient here guys. Wh have what looks to be a double dip reversal that has only just began... We also have the MJO heading towards the +NAO phases So we really shouldn’t bemoan the models if we get a short mild spell, it’s been very well advertised and like it or lump it we now need to turn our attention towards the lo res range. If that tropical signal can propagate through the maritimes as some commentators on Twitter have suggested then combined with the above reversal some serious charts must be awaiting us in the near future... Studying the models after day 10 is relevant and is very much within the remit of this thread... As we peer through the looking glass towards a mid-late January period that holds so much promise...