Singularity

Glad to see ECM firmly in the 'extended then reloading ridge from the Azores' camp, illustrating a classic fine summer pattern that we could all very much do with after such a wretched week of weather - which has a few more unpleasant days still to bare the brunt of for those up north (unless of course you enjoy the rain!). Good thing that at this time of year even sodden ground can dry out nicely after 3 or 4 dry and at least partially sunny days.

GFS on the left still giving us a hard time as it breaks a low away east from the main Atlantic trough and so keeps the jet flatter and in fact travelling right across central UK. A shallow low is also generated over France which moves NE to Scandi where it encourages the ridge to take on not the greatest of orientations for warmth as it finally manages to build through the UK over the following few days. UKMO keeps things simpler with no breakaway Atlantic low and nothing consolidating over Europe anywhere near the UK, but we do see the ridge showing more sign compared to previous runs of the extended ridge breaking in two. Any split-off would be likely to stall somewhere close to our east and gain some strength as the Atlantic trough drives warm air over it aloft (which then sinks and reinforces the ridge). We'd warm up a fair bit but be at risk of a thundery breakdown occurring before long. It's probable, though, that the trough out west would align similar to what the ECM 00z showed at +168, in which case the Azores High will extend a new ridge to the NE to join with our current run and something similar to that ECM run would follow. - that being a run that showed an outcome that was a bit flatter than the UKMO 12z but without the breakaway low of the GFS 12z, which is optimal for a fast-track to warmth without sacrificing stability. Hopefully the 12z ECM won't follow the GFS 12z with it's irritating complications. I know the 00z yesterday was along similar lines so the outcome likely remains among the EC Ens. somewhere. Seems like we often struggle to achieve those nice neat transitions to a fine spell, but there's still plenty of hope at the moment. Oh and GEM's nice again, for anyone wondering; +144 is close to the UKMO 12z but slightly to the NW with the ridge position, which suggests to me that the reinforcement from the SW remains more likely than the split-off scenario

This chart could also be interpreted as a typical frequency and strength of high pressure across the UK and NW Europe (decent enough) and less low pressure than usual trying to get in from the west. The poleward bulge in the contour lines over Europe further supports this deduction. This is not bad going for a multi-ensemble-run-mean. The anomalously high heights over Greenland could be an issue though, as lows may tend to become low moving N of the UK at times resulting in a changeable W to NW flow. So perhaps quite a variable month overall but with at least an average amount of fine weather to be had. Actually quite similar to your deduction after all - it's only the mid-Atlantic ridge part I'm not so sure about Just one model of course and it will be interesting to see what GloSea5 has been getting up to with the next update from the Met Office that should be online within the next 5 days.

ECM 00z is exactly what I expected to see in the model output given the background signals, with GEM similar but perhaps slightly too amplified still, UKMO a day quicker than those two models but otherwise the same overall idea, and GFS not far off either; a flatter jet delays north-eastward extension of the ridge (also worth noting that post-day 10 should be paid little attention given GLAAM bias - not that it should ever be taken too seriously anyway, but on this occasion even the GEFS mean is likely to be adversely affected to at least some extent). So it's looking good this morning with respect to mid-late next week Something that struck me when reviewing the Jul-Aug 1995 sequence yesterday was how there were still a number of interruptions to the fine conditions, mostly hitting the NE hardest as lows scraped past on their way into Scandinavia. This typically occurs during a 'reloading ridge' pattern in summer as it's rare to have the jet stay far north enough to keep all of the UK in the clear during those intermediate moments as one ridge leaves and another makes its move toward us. The temporary restriction of higher pressure toward southern areas typically results in an escalation of humidity and sometimes temperatures before a sharp freshening up. Sometimes thunderstorms feature as cooler air moves in at upper levels ahead of surface levels. 2006 had some very fine examples of this - but let's not get ahead of ourselves; we're far from guaranteed such an appealing run of events this summer. We just have a better shot than has been the case for many years now. Here's hoping!

Okay so ECM is notably slower to move the warm sector away on Sunday, enough so that the mid-20s look feasible in the SE corner. It then turns into a very progressive run, so quite the contrast to GFS and GEM. As tropical maritime air is thrown east across a wide swathe of anomalously warm waters that lies adjacent to the western coastlines of northern Africa and western Europe, the usual heat build is accelerated and some impressive temps result after just a few days. It's because of this manner of logic that I can see why some long range outlooks highlight an increased chance of extreme temperatures across NW Europe this year. Having that include the UK is another matter - and one that may divide opinion on here given that record-challenging temps = dangerous temps for human health. The heat build potential is similar to that of 2015, but that year we had cooler waters in the vicinity of the UK plus interference from a developing El Nino, which both played their part in driving a strong jet stream along the major temperature boundary between the hot continent and cool seas. It only really broke once, and boy did we know about it (30th June to 4th July, peaking 1st July). I do feel ECM is being a bit overly mobile with those lows this evening though - a slower build-up of heat seems more likely. I also wonder how easily we can achieve the level of stability required to avoid quick thundery breakdowns. Hopefully the similarities of the Atlantic-Europe sector patterns with those of 1995 will bear fruit in that respect.

Still an unusually large range of minimum pressure values being produced for the low affecting the UK noon Sunday; GFS is near 992 mb whereas UKMO is around 998 mb and GEM 999 mb. So GFS is responsible for most of that range at the moment - I wonder which end of the spectrum will ECM align with? Probably neither; slap bang in the middle for ultimate lack of clarity It's an important detail as it determines just how strong the breeze is during the weekend as well as how quickly the warm sector moves away east. So a big impact on how warm or not it feels across the UK. Of course the SE will be warmest of all and could see temps several into the 20s on Sunday if the warm sector hangs around long enough. It should be cleared by Monday though; GEM has backed down on the lingering plume-like outcome. Question now is whether the models are still taking the mid-Atlantic poleward amplification too far. GFS has reduced it for mid-week but increases it for the rest of the week. GEM is just more amplified overall (model bias?).

As much as the trend from the ECM, GFS and UKMO models has slowed the weekend low and kept it further northwest, GEM remains distanced from them with a much quicker weakening of the Atlantic low with the plume hanging on across much of the far-S right through until late Monday. A slower ridge arrival next week is the price paid, but it's still on a par with ECM even though in that case it's due to how that model keeps the jet so flat across the Atlantic until Thursday with a very shallow disturbance finding its way across to interfere with proceedings. Anyway - I'd be amazed if GEM was victorious at such short range, but I am inclined to see some further slowing down of the warm air removal as a probable trend in the other models, in which case GFS and UKMO may also slow the ridge arrival next week but frankly I'd be very happy if it arrived by mid-month and then tended to stick around or keep on reloading for the following 10 weeks or so... is that too much to ask for?

Thanks for the detailed round-up @Tamara , I keep losing track of the GWO/GLAAM developments as - ironically - I spend so much time working on other areas of research and development . So while on the face of it the model trend this evening resembles a backing-down from having shown too much of an MJO phase 6 response, this is really more of an overdone IO forcing by GEFS (in particular) that happens to bear close resemblance. The usual horrendously large negative GLAAM bias beyond about a week's range. At least knowing of that I was expecting an improvement in that model's output anyway . So now we have two models (UKMO and ECM) moving the weekend low very slowly through to Sun with the SE tasting the fringes of a continental plume - at the risk of some destabilisation impacts perhaps, depending on the interplay with the base of the trough (i.e. with associated upper convergence and divergence regions). GFS remains more progressive but has trended slower over the past four runs. As if for a laugh we then have ECM flirting with a Scandi trough more than the other two, but this looks to be driven not by a GFS-like overcooking of IO forcing but instead a more meridional jet ahead of the large-scale deceleration. This could just be the model showing it's amplification bias - though the range is a bit short for it to be a major factor. For 8 days from now, the evening runs feature one very pleasant outcome, one rather cool but drying up and trending warmer afterward as the ridge drifts east, and one with an impressive blocking high sat right overhead (thanks to split jet setup as explained by CreweCold earlier). Not bad going at all Interesting that it appears GEM may well have some of the negative GLAAM bias that GFS does, though it's also known to over-amplify so the true balance of play is somewhat mysterious.

GFS 06z is kind enough to find a path to the mid-Atlantic trough and NW-Europe ridge with the Scandi trough only a transitional feature. Takes until Tue for the breeze to properly die down though. I wonder if this will be one of the windiest 7- or 8-day periods on record for June?

I have seen enough visuals to know the Arctic truly is in peril. Greenland on the other hand has for many weeks been benefiting from the same weather patterns that have kept Barents-Kara colder than average for a long time with the sea ice holding on for longer than in many recent years in that region. It's the main reason why the sea ice extent has not been all that low relative to the volume (note 'relative'; still very low overall compared to pre-2006). Another factor is the record winter-spring snow cover build-up over Greenland - this being thanks in large part to greater moisture availability in the warmer world. If blocking can stay away from locations NW of the UK this coming summer and early-mid autumn, Greenland may even see net gains. There is a possibility that in the near future (next decade or even few years) we could see Greenland/Arctic Canada become the primary focal point of cold through the entire N. Hem winter-spring season, though in some cases like the last one, it may have competition from central parts of the Asian continent. On the other hand, deeper snow cover insulates the ice from the cold air, so any warm air pulses that do remove the surface snow layers will then be able to attack ice structures that are more fragile than they used to be. My personal suspicion is that Greenland will undergo a stuttering deterioration as gains via large snow deposits are more than offset by relatively short-timescale collapses of glacier feet or ice shelves. How much of a deterioration depends on to what extent a much warmer Arctic Ocean can impact it, and of course that is presuming the Arctic sea ice will in some year soon melt away soon enough to leave most of the Arctic Ocean open to significant solar input; by mid-late August is already too late in the season for that. I'd be astounded if such melt-out was achieved by that time this year... but I can't rule it out, as alarmist as that sounds

From best to worst - quite the spread of outcomes still for the weekend low's strength and track. Amazing that UKMO has it so much weaker than ECM and GFS. Anyone's guess going into next week. There seems to be no dominant signal whatsoever. UKMO seems to be the only one even trying to restore an Atlantic trough/NW Europe ridge pattern as would be expected when just considering seasonal wavelength changes against a neutral ENSO background... this stalled Scandi trough idea from GFS and GEM is a surprising one to be seeing for mid-June this year. It may be because by some measures the MJO has just about made it into phase 6 with significant amplitude at the moment, which may be enough to produce a lagged response on the Scandi heights tendency; So it could be a case of hard luck there - but only if GFS and GEM are not propagating the response too cleanly. ECM introduces a major complication in the form of a broad mid-Atlantic trough days 8-10, with the combined picture favouring a changeable regime, most settled in the south and least so in the north. Just one of a myriad of possibilities as we struggle to find a more enjoyable weather pattern as there has been so much hope for by the final third or week or the month.

- and of course most of that wet signal for June could be from this coming week alone, in fact the distribution of anomalies matches the event today-tomorrow really quite closely. I do still see a general settling down trend after this week although the ongoing Arctic mayhem means nerves are wrung tighter than usual for those seeing to anticipate the season ahead with at least some degree of effectiveness.

This year is starting to feel downright malicious; having a May that favours spreading out of increasingly thin ice when it was already thin to start with, and then following up with an early-mid June dominated by 'warm blocking' and a Pacific dipole pattern is like a super-villain's master plan to destroy the Arctic atmosphere and ecosystem. Even the smaller details leading up to the June misdemeanors are just right for maximising the level of impact; Day 4 and a ridge centred over the Pacific side joins forces with an elongated trough to send some exceptionally warm (in fact quite hot) air (850s are a reasonable guide here) through Alaska and right over to the Aleutians.Meanwhile blocking over Barents/Kara works in conjunction with a shallow low moving a little west of north toward Greenland to send a wide wedge of unusually warm air through Scandinavia. This one sees more in the way of modification from residual snow cover but not by a lot so it'll still pack a serious punch at the surface as it moves over the 'easy ice' on the Atlantic side of the Arctic. Substantial losses may occur in the space of just a week. Day 5 and troughs simultaneously moving into place over N. Canada and the Siberian coastal Arctic act in combination with the blocking to form a bridge of both high pressure and exceptionally warm air. Even allowing for extensive surface modification I can see a large proportion of the CAB experiencing above-freezing temps at least intermittently. Day 6 and the lows have not merged across the N. Pole which would be a good way to cut-off the warm air influx. Now I do still see this as something that could yet manifest after all, but with GFS having moved away from it after considering it on previous days, the chances of that have unfortunately become much lower over the past 24 hours. Only right out at day 9 do we finally see a low moving across the CAB to interrupt the anomalously warm spell... well, mitigate it at least. - but look at that fat finger of exceptional warmth through the ESS... this has been a feature of many recent GFS runs (see 06s and 12z on right), and a source of much disbelief among followers of the Arctic sea ice progression, yet now we have ECM showing something just about as dramatic! This being as the strong blocking behind the Pacific dipole chooses eastern Asia as a vacation spot, while the seemingly eternal central-Asian/Siberian trough activity continues to throw warm air across to that region from SW/S parts of Asia. Back when I was doing studies in Reading, I can recall seeing a reconstruction of sea ice in the 1950s in which one of the early years had a sharp dip in ice extent. I have since found that 1953 saw a similarly persistent central-Asian/Siberian trough well into the year. If my memory is accurate and this isn't just a coincidence... well, it doesn't bode well at all for the Arctic sea ice this summer

There is some wiggle room considering the spread in ensembles, plus some admittedly subtle hints of an overall sharpening of the mid-Atlantic trough and perhaps even a west-based negative NAO by day 10 which would be interesting but not the most sustainable of patterns for fine weather. Really though, I can see some chance that GFS and ECM have even the broader details wrong enough in 5-6 days time that it could render the current 500 mb anomaly guidance invalid. I I know that's not a common occurrence at all, indeed it's not something I would actually bet on at this time, but worth considering IMO. We are in the midst of some particularly volatile times in terms of the atmospheric setup. Adding to the uncertainties is the apparent impetus for blocking highs to try and persist over the Arctic (according to ECM mostly but GFS is having a think about it too) even where the stratospheric profile leans toward the opposite. Could regional sea ice based forcing be causing some mischief I wonder? I hope it does not come to pass, not just for our sake but for that of the Arctic sea ice which is in the most fragile state ever observed at this time of year. Slack, cloudy lows are what it needs this summer, not clear highs with 24-hour irradiation.

Wise words from you as always It's interesting how we've tended to had UKMO and GEM banding together lately, though GEM has fallen a bit short with the ridge influence this morning days 5-6 (but is still less disturbed than ECM and to some extent GFS). GEM does however have the sharper trough in the mid-Atlantic on day 6 with the potential deep low digging further south and maintaining less forward momentum as a result. I will be keeping on eye on this. My draft forecasts for next weekend currently cast a very wide net! GEM has too little ridging to maintain a finer, warmer spell for long, but UKMO looks well primed to do a better job of things. Fingers crossed that the tendency of recent weeks is still going to be at hand.

Following my post just how - this is encouraging from UKMO as the big trough off the U.S. is clearly slower with a more amplified jet stream ahead of it. UKMO was second only to GEM in spotting the more settled outcome for last week. GEM is now rather explosive-looking for Thu though, and barely gets the next Euro ridge set up before breaking it down: ...but again, this is all far enough out in time for much adjustment to potentially occur

Hello I was deliberately unspecific there; extreme heat, thunderstorms/excessive rainfall and strong winds are all possible outcomes with such a setup. Drought would however require the pattern to adjust further west than looks likely at this time and even then it would take many weeks of persistently dry, often hot weather to produce one. This morning I am shocked at the sheer strength of the low being modelled to cross the Atlantic days 8-10. This currently looks to be an over 2-sigma event i.e. more than two standard deviations outside of the 'norm' i.e. very unusual indeed. Such large and powerful storms have the ability to shift the longwave pattern against the backgroud signals which is worrying as that typically means eastward of what would otherwise occur. The remnants of the B-name Atlantic tropical cyclone in Aug 2014 had this effect and led to a cool showery month instead of a warm, sometimes thundery one as was looking likely to be the case otherwise. I sincerely hope the packet of energy that fuels this major storm does not manage to journey across so smoothly and instead gets involved with some developments along the way that lower the remaining potential energy for LP development. Ireland's tree population would not fare too well if this came to pass - good thing it's still over a week away with plenty of time for changes!

As far as I see it, ECM and GFS are in the process one again of correcting downward a kick in the jet stream and so adjusting the mean ridge position west toward the UK and W. Europe having initially placed it almost in W. Asia. For some reason whatever causes these errors in those two models seems to affect GEM less. Things when get very interesting as an MJO pulse combines with an unusually 'wiggly jet' as part of a wavenumber-5 pattern that typically produces extremes of weather toward the western extent of ridges - which is where we might well be.

15.5*C please, because, well, it... feels right? Yes, that'll serve me well

Actually scratch that - just run through a smoother radar sequence on the laptop and it's some leftward propagation of the most intense returns relative to the NE'ward storm motion. I have to say, based on Met Office warnings I expected a more sporadic nature to the rain away from that big storm, as opposed to a mass of the dreaded 'thundery rain'. A load of rain but minimal lightning was the worst case scenario for me as I'd rather keep the ground dry for hiking tomorrow. At least some electrical fun would soften the blow

You know it really does look as of the big storm has turned a corner. There is a shallow low centred to its west lifting north so I suppose it could be related to that?

Rapid development NW of Cherbourg over the past 15 min and with a slight bow structure to the peak intensities - could be an outflow boundary?

As far as I'm concerned that's entirely typical of that area and as a result my area a little way inland Seriously though - I have watched a staggering proportion of downpours and thunderstorms go wandering merrily by, most of them either 15-30 miles to my west or 20-40 miles to my east. Then in a westerly you get all those ones hugging Salisbury Plain while the sea breeze moves inland to keep this region clear. It should be separated from Hants/Dorset and named 'NoWeather'

The early Saturday storms produced a peak rain rate of 120 mm/hr here, but their fairly quick motion limited the impact greatly, with an observed total of just 5.5 mm. This time we have both slower movement and more potential for the cells to grow in a sprawling manner, while there is about as much or perhaps even more moisture available. So it could well be pretty nasty for some places tonight. If the above verified my May total would go from 5 mm short of the LTA to 30 or so above, which would make it look a wet month when considering summary statistics alone. It's actually had 17 dry days and if the big event last Wed hadn't occurred I'd be on 19.2 mm and looking to dodge tonight's rain in a bid to stay on course for the driest recorded May here in the period 2000-2017. I've had an unusually large number of months since 2010 in which over half the monthly total rainfall (and on a number of occasions well over half) fell on just one or two days. Climate change showing it's hand perhaps?

Standard for long range models e.g. still an experimental science, sometimes well wide of the mark, not to be taken too seriously therefore. CFSv2 has historically been particularly unreliable, but it seems to have improved since the turn of the year.