Singularity

There I was expecting a stubborn GFS and it went and junped even further than ECM! A blend of the last two GFS runs and the ECM 00z presents a fairly decent picture away from the Northwest. Ideally of course we'd see the GFS 06z serve as a foundation for the actual outcome but this still seems a bit overly hopeful at this stage. Some good signs emerging though

Great most MWB To me it feels like we have some changes in the forcing from the tropics - namely the reduced negative forcing on GLAAM - compared to original model projections which are filtering through but until the ECM 00z this had not proved marked enough to produce a robust change in the direction of events. As GEFS/GFS has more negative GLAAM bias longer-term, I expect it to be more resistant to a change of tune away from a rather flat jet periodically bringing troughs uncomfortably close to the UK. Still, I've not seen enough yet to make a call for widespread settled conditions to establish next week, with 'gently changeable' feeling like an apt summary for the time being.

We have the section along the western U.S. coast in line with a negative PDO - notice that the negative anomalies are typically weak - but the stretch going west from there to the eastern coasts of Asia is more akin to a positive PDO setup. This is the more significant contributor to the index and as a result it continues to measure positive, albeit not very strongly. What's really interesting is that those cold anomalies along that belt are in (perhaps large) part a consequence of the anomalous snow cover across Siberia that built-up over the winter and lasted longer than usual through the spring, which is being linked by an increasing number of studies to the reducing Arctic sea ice and resulting increased moisture availability across the high latitudes of the Asian continent. So we may be witnessing an early example of a feedback mechanism that threatens to push the PDO toward positive more often than would otherwise be the case. This could be why there is a loose consensus among climate models for El Nino events to become more frequent/longer lasting with climate change - it depends on how well those models are capturing the Arctic sea ice loss and it's impacts on atmospheric moisture levels.

You know, I'm making so much of this rather wobbly trend because of my knowledge of background drivers etc. - I am playing the 'spot the trend spotter' game that to be honest is the main reason why I follow the models with such enthusiasm. GFS 12z is mighty close to a settled outcome next week but a particularly deep Atlantic trough (for the time of year) to the northwest keeps it changeable in the end, though with plenty of dry spells to be made the most of so... half-decent might be the summary unless of course you're looking for some proper warmth to return. Speaking of which, the ensembles do now contain a few runs that develop a breakaway ridge into Europe, reminiscent of how the last fine and very warm/hot spell (for much of England and Wales) began but without such extreme heat lurking to the south, and funnily enough GEM has gone all slack and ponderous-looking for early-mid-next week which is also similar to before the aforementioned spell of weather. Now I'm not saying that much should be made of this at this stage, but it is along the lines of what GP put across the idea of about a week ago, and something I've also been considering given the behaviour of certain teleconnections (on which I can't give away the details, sorry). So it seems a lot of options are now on the table, albeit some of them just barely, with the ensemble mean starting to be more a reflection of wide spread among the ensembles leading to a mean signal that resembles climatology quite well, but with distortion due to numerous ensemble members producing particularly deep lows in the N. Atlantic - these being features that may help us or hinder us depending on the orientation of the jet stream, a detail that remains very unclear indeed but with a slight overall shift in the emphasis away from flat west-east (or even WNW to ESE), which offers some encouragement .

That's where the required consistency needs to come from, but we have to start somewhere and at such range ensemble means will inevitably trail operational runs. What I've done is essentially point out that an option has emerged against the 'flow' of recent model (including ensemble) guidance - from two major models at once - and this represents a significant possibility of a new path emerging. I know some won't believe in such a method of interpretation but I have found it to serve me well enough over the years

Another step forward with Azores High ridging across days 8-10 from both GFS (by day 8 ) and ECM (day 9 ). As far out as this is, such a trend is significant given the insistence the models had been displaying with respect to maintaining a west-retracted Azores High. Of course consistency in this trend or at least with something that fits as settled as the GFS 00z is needed before we can really start to breathe sighs of relief and raise the bar of hope.

Not heard of such a version of La Nina but looking through historical cases I can see that La Nina events do have a tendency to feature the peak anomalies further west than a classic El Nino is known to. What we seem to be witnessing is a regional response to the anomalous easterlies which may in turn be reinforcing itself, but only within that area due to a lack of the other supportive mechanisms that are needed to generate a full-scale La Nina event (this being why the models are so hesitant to kick one off even after the recent negative trend). This regional development is causing a lot of trouble when trying to figure out how the downstream patterns will respond, in particular for us the Atlantic-Euro pattern. Just how coherently can a La Nina-like state be forced when the forcing is coming from a narrower region than seen with La Nina events? If it's very coherently then we're going to struggle to get much of a summer back this side of late July (that being when the wave-guide tends to shift again), but if not then we should tend to see some interludes of, say, a week or two during which the Azores High builds northeast across the UK and Europe with greater strength again, before a week or two the other way again, making for a notably two-faced summer that lurches between fine, dry and very warm/hot and changeable/unsettled with near average/cool temperatures. Currently we're sliding unpleasantly into the latter and it looks to make my planned hiking holiday in Wales from Friday onward rather precarious at times. The loss of the positive-neutral (as in, neutral but tending a little positive i.e. Nino at times) oceanic state was a tragic turn in the year of 2017 for those seeking a predominantly fine summer in which a break in the UK stood a great chance of being at least half-fine (as in half of the time). Oh - and I was referring to the chart I posted which is from Mike Ventrice's site and shows the GFS operational in isolation.

There's a little bit of difference between ECM and GFS with respect to those equatorial zonal winds with the latter more varied/less coherent with the easterlies, although admittedly the latter is only an operational run rather than full ensemble - not sure why Ventrice chooses the operational for such a projection but oh well. The disagreement is small, but enough that I can see why GFS has given the Azores High a little more say across Europe than ECM over the past couple of runs. That ECM has at least trended toward increased AH influence does give me a little hope but there's still a long way to climb out of the pit of concern.

It's all about that slight signal as this is an emerged feature and it becomes a question as to whether this will continue to develop as more ensembles come around and/or ridges are made stronger/more expansive, or go no further than what we've been presented with this morning. Also worth bearing in mind that 'average' 500 mb heights are typically associated with conditions being more settled than not at this time of year (as in, 2 days fine, 1 day not - that sort of thing).

We have seen a little backing off by the models with respect to the retraction of the Azores High west - much as was to be expected given atmospheric response to attempts to force a La Nina-like state proving less than enthusiastic in recent days. So far though, this is only enough to significantly improve prospects for the far S/SE and even here it remains changeable. So more movement away from suppressing the Azores High's attempts to ridge into the UK is needed. With a bit of luck we might get there pretty soon into July but unfortunately up to 10 days in also remains within the range of possibilities.

Some weakening of the jet stream and return toward Atlantic trough/UK-Euro ridge pattern on the GFS 06z but only short-lived and a whole 10-11 days away. I continue to believe that the pattern should not, given the base state, become as 'stuck' in a poor configuration for us as some runs have lately been suggesting, but that belief has taken some hits over the past few days and is finding it harder to get back on its feet after each new blow. That's the best I can do for an alternative take this morning

With GFS projecting a powerful jet stream across the N. Atlantic (nearly 200 mph at one point, unusual for summer) but ECM shutting it off entirely, you'd think it was winter! Something is clearly afoot over the US early next week, something that ECM handles very differently to GFS... But I'm away from the PC this evening and can't devote enough time to examine things sufficiently at this time.

The question these days is not whether it will turn notably unsettled, but for how long. That the GLAAM state is already trying to move away from the La Nina-like state - right in the face of what GEFS was projecting - suggests it shouldn't be for too long but we'll see. The 18z GFS yesterday looked like a nice straightforward response to this change after a typical lag time, but the 00z this morning has delayed it again and the 00z ECM presents a lengthy road to recovery as of day 10, though it is one of the more extreme possible outcomes with the longwave pattern given the amount of amplification it produces so some caution has to be applied there. Difficult times ahead and goes to show that an ENSO-neutral background has little power to prevent the atmospheric state wandering away from it from time to time. Judging by what many longer-range models are predicting for July as a whole (strong NE'ward extensions of the Azores High by a week or two in) it seems a wander back toward neutral or even slightly El Nino-like may be expected to feature. Hopefully our patience will not be tested too much.

Temps will remain slightly above average in the far south and the Southeast through Saturday by the looks of things but elsewhere it does look average at best and generally below in the west. Anyway looking ahead to the start of next week, I'm not sure how it is that UKMO continues to see that shallow low crossing the Atlantic being not just weaker but so much slower-moving than all of the other models, but it sure does keep the uncertainty nice and high (sarcasm alert). If for now we assume the big coming together of lows over the UK will actually feature next week, then at least a glimmer of hope has emerged in the charts for next weekend, albeit only just in the case of the slower GFS; This may seem like a major case of clutching at straws but I've been watching the atmospheric angular momentum projections adjust over the past couple of days in ways that may result in an opportunity to at least interrupt the cooler and more unsettled period of weather, so it makes sense to see the models bringing the Azores High back toward the UK again. Too early to say if this could be a full move away from the La Nina-like tendency that brings the troubles next week; GFS does not look at all keen on that idea but ECM looks a little more hopeful. Regardless, if one is hoping for the complex low next week to have as little impact as possible, best hope it scoots through as fast as possible, as stalling it west of the UK looks a major long-shot as of this evening (but Man With Beard's line of thought does remain alive).

With the models remaining so stubbornly against it, it's seeming like a tall order, but for some reason when a change in the pattern is forced by tropical developments for example, they do have a habit of making it both too pronounced and too resistant to further change, so some hope remains, albeit rather tenuous. ... but given I'm away hiking in Wales for the period 30th June to 7th July, I'd not be surprised to see GP's predictions prove accurate but at the longest end of the timescales given, so leaving me with at best two better days after six unreliable/dire ones

You've done a great job summarising my own suspicions given comments by the likes of GP a couple of days ago plus known model tendencies during times of increasing jet stream strength (i.e. going too far). We see ECM making the trough sharper (more of a southward elongation) on day 8 compared to GFS' (typical of that model) bowling-ball low. Then that possibility of the trough not making the journey in the first place, though it's 3 against 1 with the best performing models (ECM, GFS and GEM v. UKMO with JMA a curious and unfortunately still changeable hybrid of both ways forward) so not one to hang your hat on - hopefully the trend tomorrow will at least be to have the crossing trough putting on the brakes while further west - which would naturally be encouraged if the jet stream was toned down - or better still to keep it away altogether and let the Azores High continue to be our friend. Not sure though that I can quite believe that we could keep it with us right through the week or so of time that looks to be influenced by the La Nina-like swing in the atmospheric base state. It'd seem a minor miracle but that doesn't rule it out now does it?

In my experience there nearly always ends up being something or other complicating matters; smaller disturbances in the flow, that sort of thing - although exceptions can and do occur. I am skeptical of the likelihood - but not the possibility. Maybe a deep trough will indeed march its way across from the western N. Atlantic, which would be another notable event to add to June 2017's list. From unusually wet (up north) and windy to exceptionally hot and then back - at least briefly - to unusually wet and windy? Personally I'd enjoy the variation of weather, but I'm a bit odd when all's said and done

I guess you can't stop GFS being GFS Whenever I see the jet stream modelled to become that flat over such a great distance outside of the winter season, I become very skeptical indeed.

12z has the jet stream dipping south in the mid-Atlantic much more sharply as of Sunday afternoon than was the case on the previous few (or probably more) runs. This could have interesting results over the following few days given the setup over Europe; At least there's something of interest to keep an eye on while my brain slowly stews

I found myself going all jittery looking at what ARPEGE gets up to... interesting how the hottest spot starts a little way down the coast from Bristol and then migrates north, like some kin dof freakish 'pressure cooker' zone where local convergence is occurring while somehow avoiding the creation of cloud cover. Not sure I can see the CAP being so strong and the airmass so dry as to permit that... right? Even so, given that the slightly faster progression of events now brings the 20*C 850 hPa isotherm up to the far-SW by Wednesday evening and that this is following four days of increasingly high temps for a large part of the southwest region, I'd not be that surprised to see the mid-30s crop up somewhere in said region. It'll then be one more uncomfortable night before the freshening up occurs at some point on Thursday. Interesting that while GFS performs this early on, ARPEGE takes until mid-morning for CS England and late morning for the SE. The former then manages to get into the mid-20s anyway thanks to the warm start (the boundary does not look all that strong in temps of temp changes at the surface on this model run) while the SE sneaks in the high-20s in the late morning and then, after a dip due to some showery rain, rebounds toward that again by late afternoon. This could be a bit optimistic but it goes to show that Thursday is not looking like a straight forward changeover to fresh Atlantic weather. Allowing again for over-optimism from the model, the weakness of that boundary may even allow Friday to bring further respectably high temps; ECM appears similar enough that this option is at least on the table rather than the chair, but GFS and UKMO both make more of Thursday's boundary and so restrict temps to the mid-20s at best. So it remains unclear just how much we'll be cooling down Thu-Fri. Briefly on the weekend onward, well there's so little consistency between models that it all seems very much up in the air (thankfully, given GFS' nightmarish ideas for several runs now). It has not escaped my attention though how the abrupt forcing toward a broad trough dropping in from the NW has in the case of ECM been put back to day 10 on three runs in a row now. The change to a run of easterlies in the tropical Pacific are enough for me to see highly changeable conditions as very plausible for next week as a whole, but I've seen ECM overestimate those easterlies before so I'm not yet convinced that a trough will completely take over... though I'd not rule out a brief romp across our lands. Either way, the critical question going forward will be how long do the easterlies last before the pendulum swings back the other way? Typical duration is what, a week? Edit: The uppers are one thing but perhaps the belt of extreme theta-e values predicted by ARPEGE is the reason for it showing such incredible temperatures; this belt moves NE during the evening and so do the most extreme temps.

Going by ECM the 20*C isotherm moves over all of far-S England at some point on Thursday so it's a bit more enthusiastic than GFS. Interestingly the westerly flow is not steady enough to entirely drive the plume away even by noon Friday; still a chance of high-20s in at least the far SE from that chart. Then oh look - the low is no longer predicted to dive right across the UK this weekend. This is closer to GFS' recent runs but still with the jet aligned differently on Sat (NW-SE as opposed to W-E). The model still finds a way to drop a trough in eventually i.e. by day 10 - something GFS has also been going along with generally - but honestly, given recent trends and how well they support the notion that the GLAAM changes during the ongoing downward trend period are being overdone, causing the models to display too much impetus to retract the Azores High west and as a result to overlook some relatively weak but still significant ridges managing to continue making it across Europe on a frequent basis. These work to keep that intense plume in place too... so those in Iberia and France may detest my conclusions here but I'm afraid the weather will do what it will do regardless of what we hope to see. Broadly it appears that the final week of June will probably be a more changeable period but one which with a bit of luck should avoid going full-on unsettled. By early July things will hopefully be on the turn again - that would after all be very fitting for an ENSO-neutral summer .

ECM still stubbornly making more of the ability of the LP systems to find their way close to or even over the UK beyond Thursday. Puzzling times with that model - what's making it act so differently to the others? Will just have to let it lie until tomorrow and hope it falls into line then (as opposed to turning out to be the only one on the right path!). Anyway, ARPEGE makes for a nice illustration of daytime max temperatures over the coming days - though locally 1-2*C can probably be added for the hottest spots; Essentially we're still cooking with the formerly Azores High tomorrow and as such the heat should again generally be greatest the furthest you are from land within England and Wales. Monday sees the Spanish Plume start to make itself known across the far south while remaining areas are still stewing in the airmass from the weekend. So peak temps occurring not just well inland but down to within some 30-40 miles from the South Coast. Tuesday sees the cold front produce a band of suppressed temps for some central parts (but note that it's more fragmented and so limited in effect than what GFS has been producing), while the far-south is fully enveloped within the plume, resulting in some fairly impressive peak temps (locally up to 33*C perhaps?). Worth noting though that GFS has adjusted the plume influence downward slightly on the 12z compared to previous runs so it doesn't get above 27*C although this could still allow for 30*C in places given typical model error. By Wednesday we have the interesting situation in which the plume is angled SE-NW through the SW'rn third of the UK, resulting in the highest temps occurring in the vicinity of Bristol. Tomorrow evening we'll have ARPEGE's take on Thursday to examine. Could well be some entertaining numbers with that .

Liking the idea of only a shallow low during the final days of this particular fine spell; room for thunderstorms without the cool blustery winds afterward. Starting to wonder if we're seeing a version of events emerging that's less dramatic but better for keeping a more settled regime going thereafter, at least for southern parts - but now I'm getting toward the longer-term that I pledged to avoid so... post terminated!

So that's the second 06z in a row going for a faster breakdown than the other GFS runs. Funny that. Overall GFS continues to strongly display low-GLAAM forcing on the pattern by day 9 or 10 onward. Meanwhile ECM has moved away from this with more of a classic 'sweeping past into Scandi' period of low pressure influence and the upstream pattern looking better for bringing about a new push NE of the Azores High to the UK. So I'd say it's best not to pay too much attention to what the models show beyond next Friday; there are conflicting signals to sort out and in any case it puts you at risk of tainting your enjoyment of the fine weekend with worries about the following one and beyond. Trust me, I know from personal experience With that in mind, I will aim to avoid discussing the longer-term again until Monday at the earliest (unless I manage to forget this pledge... no guarantees I'm afraid!) In the nearer term there are still considerable uncertainties beyond the weekend; no two runs agree on the position of the very mild/fairly cool boundary Mon-Wed, with the 06z shifting it north by a hundred miles or so. It serves as the focus for scattered thunderstorms on Mon and then a lot of cloudiness and suppressed temps (high teens at best) Tue-Wed.

Starting to see some vigorous cyclones projected by various models during the next 10 days. I've not got time to do a detailed post yet but I just wanted to post this insane GEM chart depicting a 950 (or even 945) hPa cyclone for next Saturday; Just imagine of that was to actually take place