[Model Output Discussions 06z 04/11/16]

We're especially interested to see what cohesion in broader signal appears 2nd half Dec in EC Monthly at 10pm, versus latest GloSea5.

[Model Output Discussions 06z 04/11/16]

12z ECMWF ENS set against model climatology lean pretty firmly in median 2m temps towards below avg (at times quite markedly) out to at least 9 Dec. 

[Model Output Discussions 06z 04/11/16]

14 minutes ago, blizzard81 said:

One thing I have noticed on the gfs 12z and 18z ensembles is a nose dive in temps on many members at the end of the runs - 11th/12th Dec. Pretty much ties in with what ecm seasonal and glosea are pointing towards.

...albeit the E'ly set-up later Dec showing in both latest GloSea and ECMWF has inevitably low confidence given lead time, so (especially given weak signals prior to then into mid-month), these outcomes signposted later should be treated with due caution, at present.

[Model Output Discussions 06z 04/11/16]

2 minutes ago, CreweCold said:

We've been hearing that the long range ECM modelling has been suggesting heights to the N and NW of the UK for about 3 weeks now. It has translated to absolutely zilch of note up to this point and medium range modelling & ensemble products take us through the first week of December with seemingly zilch on the table (from a deep cold POV). I'm certainly reigning in my enthusiasm for now . 

...except GloSea5 has been signalling it even longer :-). The new EC Monthly is especially interesting, because we know pulling -ve temp anomalies (across S'rn UK in this case) out of a hat in longer range models by week 4 (it finishes 25th Dec) is quite uncommon. But it fits our current broad expectations mid-end Dec.

[Model Output Discussions 06z 04/11/16]

40 minutes ago, terrier said:

I would be very sceptical of what the gfs output is showing at the moment. We all know that the ecm is the top performance model in the verification stats. Until we get some cross model support than I would take the gfs with a massive bucket load of salt. 

Given that EC's 00z ENS median T2 for central-southern England sits anywhere from 0 to barely +6C from 28/11 to 4/12, there's really not much disagreement on broad bias towards somewhat below avg temperatures in either that model or GFS (EC showing a few markedly colder members too). However, spread in EPS fields for MSLP remains very marked by early Dec, hence caution required re just how we sit re extremes of temperature/ppn/wind into that period. I know  it's stating the obvious, but at that range the deterministic runs are not to be read in isolation (for any model) without examination of their respective ensembles/postage stamps/clusters. 

[Model Output Discussions 06z 04/11/16]

12 minutes ago, Geordiesnow said:

Also why BBC weather feel it was right to even mention the AO at this range when there is no snowy set ups along the way, they just basically chucked themselves in the media spotlight which will no doubt get picked up by the media and taken out of context. They could be right but I would'nt bet on it,

 

Because whilst we remain in contract with UKMO, our obligation remains to reflect the very latest thoughts and briefing we have from Exeter (ie UKMO Seasonal Team/Medium Range desk)

[Model Output Discussions 06z 04/11/16]

Marked ENS spread again in ECMWF post-29th, in keeping with 00z suite. Magical mystery tour.... 

[Model Output Discussions 06z 04/11/16]

1 hour ago, bluearmy said:

I think the high to the north east was glosea for mid Dec rather than early dec

the extended eps have consistently failed to support such a feature 

Correct. GloSea5 has repeatedly signalled this outcome. ECMWF prefers (weakly) +ve GPH/MSLP build to NW-N, but postage stamps show varied support towards GloSea5. Given the latter's performance strat-wise (=why Exeter were unconvinced re GEFS SSW debacle a few days ago), there's tentative support for it's evolution but we shall see where EC Monthly heads in update tomorrow.

[Model Output Discussions 06z 04/11/16]

Reason UKMO won't talk about shortwave features at T+168 is because that sort of nuance is utterly unreliable at that range. We have enough trouble accurately forecasting shortwave troughs at T+12, let alone at a range where we're much more focused on ensemble forecasting, not small-scale vagaries of deterministic output run-to-run. 

[Model Output Discussions 06z 04/11/16]

1 hour ago, northwestsnow said:

Aye sounds reflective of yesterdays meto update, sounds like Atlantic in the box seat come early Dec  not what we wanted to see, hopefully it will be shortlived, the trouble is once zonality sets in, it can last a long time.Yes it might be a cooler zonality but it will be little use i would guess unless your high up, up north...

But it's not really zonality in sense of 2015: the majority signals for early Dec look cyclonic, yes (deeply so in various members), but the pattern in NOT very progressive and very distinct from this time last year. Glosea continues to resurrect blocked set-ups mid-Dec on for rest of month, with generally below average temperatures; it favours high pressure to NE whereas the (broadly not dissimilar) ECMWF shows similar evolution albeit HP weakly signalled to NW. The general look of things is very adequately summarised thus by UKMO this morning: "The main theme (from this evolution) is that December could well be very different from last year, with -ve anomalies for both ppn and temperature for much of the country".

[Model Output Discussions 06z 04/11/16]

51 minutes ago, damianslaw said:

I suspect if the ECM went out to 268 hrs it would be showing sub 528 dam air invading across the country on a potent northerly flow.

There's marked ensemble spread in 500hPa GPH plumes post-29th Nov, with no *firm* evidence - yet - for pronounced cold weather in the 12z extended clusters (= just as many less cold members). 

[Model Output Discussions 06z 04/11/16]

53 minutes ago, feb1991blizzard said:

possibly, lets hope that a) the general prognosis for the next month hasn't changed too much plus b) that is re-affirmed by tonight's dose of the 46.  Ive got my doubts now though I have to  admit.

To skimp on the frame-by-frame detail and varied complexities anticipated into early Dec, tonight's EC Monthly ultimately heads in much the same direction as it's predecessor, with +ve GPH anomalies to north and +ve MSLP anomaly to our NW (Iceland) by mid-Dec (run ends 18th). Steady as she goes... etc.

[Model Output Discussions 06z 04/11/16]

36 minutes ago, Connor Bailey Degnan said:

Don't know what all the upset is about. 

We were always gonna see disagreements between each run.

With a negative NAO, lots of snow cover, Weak PV, Heights probable to our NW, and strat warming, I still feel very confident of a cold and at times, snowy December . 

Keep up the good faith

Not wanting to sound like a stuck record.... but to reiterate, not *all* models have gone hammer and tongs re potential SSW. Where there is better agreement is a -ve NAO/AO signal into Dec, but with potential for an unsettled spell to start the month. Whilst longer range suites still favour broad idea of high pressure to NW, low to east, there still remains considerable fluidity on the exact high-low positions and equal uncertainty on resultant temperature and ppn outcomes. Anyway that's all a way off... whereas a sting jet is here and now.

[Model Output Discussions 06z 04/11/16]

19 minutes ago, bluearmy said:

Mogreps - is that model seeing things develop broadly in line with the eps ian? 

Not had much of a mention recently and always important to have it on the same page.

It offers a broad swathe of possible tracks into Monday and this spread is likely one reason for the lack of strong signal re snow probabilities. 

[Model Output Discussions 06z 04/11/16]

The issues Sun into Mon are especially tricky. UKV generated a plastering of snow even at lower elevations across W'rn parts of the W Country (incl adjacent Bristol Channel/M5 corridor up into Wales and SW Midlands) but considered overdone. However 00z EC gives quite a few cm in pretty much same areas, but that model automatically settles all solid phase ppn. MOGREPS currently disinterested. Jury out....

[Model Output Discussions 06z 04/11/16]

8 minutes ago, northwestsnow said:

The last sentence sounds very interesting Ian! The first part does not suprise me , we are for sure going to see a settled spell medium term but im becoming a bit concerned that despite all the positive comments about the strat/ zonal winds etc we dont appear to be any sort of retrograde signal, in fact theNWP seems to be going on the opposite direction this morning! 

Disagree. If anything, the clustering for HP to NW and cyclonicity to our E with colder outcomes has strengthened in 00z EPS by early Dec, but not yet as a majority. The bimodal direction from about end of next week remains in ensembles.

[Model Output Discussions 06z 04/11/16]

18 minutes ago, Ed Stone said:

But, it's only November 19? The models will flip and flop - as is their wont (even more so when northern blocks look likely) - but, come on peeps, A wee bit of optimism?

Given that we have TMin ENS spread by morning of Dec 2nd ranging from +10C to -11C in the op (!!) & +10 to -6C in the new cycle, I think we can reasonably emphasise the uncertainty....!  Indeed even early next week, there's a raft of issues to resolve including threat (yet tbc) of significant snow in the W Country and Wales >ca 200m. 

NB A more coherent drop in T850 now signalled in the new cycle by end of next week... much less pronounced in the operational

[Model Output Discussions 06z 04/11/16]

5 minutes ago, karlos1983 said:

Understand that, but it's probably fair to say, a mobile pattern akin to last winter is hard to see through December. Trop and strat PV in far than impressive state, with little sign of forming in normal winter fashion, certainly with any of the modelling we have available. Anything after that is surely with low to medium confidence at best. 

 

Yes, of course low confidence which is why we need caution on extrapolating the here-and-now, but the tipping point will presumably be whatever unfolds with the stratospheric PV in next (circa) fortnight, as that will feed into whether the stronger PV signals emerging post-Dec - as previously signalled - are rapidly then rendered null and void, or were actually on the money. Either way, that's all some time off being resolved and it's a fascinating watch....

[Model Output Discussions 06z 04/11/16]

10 minutes ago, nick sussex said:

Ian I see you mention a new version of the ECM, do you know when this will be officially replacing the current one?. And just one more question you mention the new one shows a large drop in 850s on both that new det/control towards the end of the month. Do you have the synoptics for that? does that develop a Scandi trough and block to the nw? Thanks.

What is emerging by around 27-28th is the fine balance between an anticyclonic bias across the UK (with varying degrees of continental influence versus a more W'ly one); or conversely a +ve MSLP to NW and troughing to E, with resultant directly colder N'ly influence. This sort of umm-ahh bimodality has characterised recent extended range and doubtless will for a while. Hence unclear temp signal for us further ahead.

[Model Output Discussions 06z 04/11/16]

4 minutes ago, karlos1983 said:

Wow thanks Ian.

its hard to to take any negatives from that update. When where how blocks manifest.im happy to see that evolve.

presuming little sign of a mobile Atlantic pattern?

Cyclonicity yes (with W'rly flow bias) in ensembles, but true mobility as per last year's choo-choo train, no. But as per a previous post I made, at the present time we need caution re assuming *all* winter will see a similar paucity of that signal. 

[Model Output Discussions 06z 04/11/16]

27 minutes ago, bluearmy said:

The eps aren't as impressive as the 00z run with the sceuro troughing not as deep as earlier. Be interesting to see if the London ens reflect with less cold clustering later. 

 

...but a marked disjunction between the operational model versus new version, which nose-dives T850 det/CTRL into end of month. Net result, as before with both parallel models, remains a leaning towards below avg temps overall (albeit growing spread continues to afford low confidence on temperature by early Dec, which has been a recurrent theme). The favoured outcome, broadly, remains a more changeable phase early Dec, followed by signs of heights retrogressing to our NW (as keenly signalled towards/into mid-Dec in latest ECMWF monthly and prior to that period, in far reaches of EC 12z ENS) and blocked leanings then characterising that period. The issue remains exactly how/when/where respective block(s) manifest and resultant outcome for the UK. Despite some similar themes in GloSea and EC suites (including their seasonal output too), it's just too early to offer any confidence whatsoever, not least as stratospheric matters have yet to show *complete and unequivocal* outcome across the main models... quite yet.

[Model Output Discussions 06z 04/11/16]

7 minutes ago, Frosty. said:

Tonight's Ecm 12z ensemble mean becomes quite benign as time goes on with pressure rising across the uk with an increasing risk of fog and frost.

 

Yup, don't understand the gloomier posts this evening. ECMWF 12z ENS continue to favour slightly -ve temps versus avg by day, albeit spread in overnight minima is (at least in part) reflective of cloud cover uncertainty. Either way, 850hPa trend has become more aligned to the chillier members rather than the milder ones; I don't see anything to change the broad prognosis of temperatures overall finishing the month a tad below normal, despite some slightly milder phases. It's hardly 2015 revisited....

[Model Output Discussions 06z 04/11/16]

19 minutes ago, Frosty. said:

A huge sigh of relief 

The models show a much more even playing field between cold, average and mild, something I'm grateful for.

Yes, all pretty average-looking fare in latest 15d ensembles. No signs of any exceptional mildness (as per 2015) nor pronounced cold (as per 2010). ENS median currently trends generally a touch below average out to 1 Dec.

[Model Output Discussions 06z 04/11/16]

11 minutes ago, Frosty. said:

I don't think it will be as awful as last December though, the models have a more seasonal flavour with at least some cold indicated both in the short, medium and GloSea5 longer range.

Yes, there's no signal of anything replicating last December...!!

[Model Output Discussions 06z 04/11/16]

48 minutes ago, January Snowstorm said:

Which begs the question why we bother to look beyond 10 days? I mean if everything is for cold 24hours ago and then gets watered down a day later (despite all signals pointing cold).

Longer range suites aren't deterministic runs! They merely give broad guidance on trends. Despite mixed signals, temperatures are still more likely to end-up below average overall, based on latest output. There's a long way to go before we can express any real confidence in the synoptics/circulation by later Nov and early Dec.