Tamara

.And very often there are finely balanced situations which call for saying so. This is a voluntary weather forum - not a derivatives section of the stock market. No-one gets paid or is compelled to say anything, but most especially something they don't believe and when they think there is not enough evidence to make any definitive prediction. The modelling evolution is playing out precisely as described in previous summaries. Indeed, the battleground convergence I talked about is going to become tighter and tighter pinned down focus around NW Europe around, and beyond, the 10-day focus. There remains exactly the fork in the road I described at least twice in posts as foreseen last week - attritional forcing of sub-tropical air to the south, meeting the cold dense arctic air to the north. As suggested almost a week back when this modelling was still outside any discernible range, 'high impact' weather events were muted. I don't think that was sitting on the fence - the various permutations are now coming into view on NWP. But the truth points to more than one potential high impact weather event - not soley snow potential for the UK The completion of the retrograde pattern will inevitably force a re-set and new momentum following from upstream. That much can be asserted. The periodicity of the -ve EAMT is a guideline for this. Starting a few days back, the retrograde sequence has the coming week still to play out. Then upstream momentum, of some measure should return. I continue to think that ultimately following attritional battleground forcing (and a very wet and muggy period of weather in my SW Europe locality) there will be something of a lifting of the cold air from the south for parts of NW Europe, including obviously the UK. Clearly the further south one is most likely to see this. A downstream ridge building from the sub tropics into Iberia (following the low-pressure sequence) could well then build northwards. Much a similar sequence as occurred from last weekend and early last week. As stated in the last post - it is a case of how any energy put back from the sub-tropical -ve NAO jet regime into the polar jet then interacts with this process and how much unstable-ve zonal wind inertia remains at higher latitudes. This sensitive balance of opposite forcing, meaning the difference between a European mid latitude ridge and Atlantic trough, or a re-connection of a northward building ridge to arctic high pressure and cold pooling. How far this cold pooling is dislodged through attrition is finely balanced.

And here it is. The retrogressing block signal that is now fully advertised by numerical models. Very robust -ve East Asian Mountain Torque (shaded blue above 30N and the red line on the torque graph) essentially creating an extra tropical wind-flow vacuum in the Pacific as the starting pistol to a powerful downstream retrograde signal. As suggested yesterday it's a biggie, and there are ramifications from this signal for quite some time to come which is the fascination for me. The question remains long term how far the retrograde evolves and how the -ve NAO behaves accordingly. The intuitive reasoning remains that attritional battle ground towards NW Europe culminates in an attempted breakdown - which tries to re-set to another Atlantic trough and amplifying downstream ridge. Does the Eurasian feedback reload this as another Scandinavian block, or, does the polar jet then prevail and create a more traditional zonal pattern with heights across mainland Europe? Finely balanced in my neutrally objective opinion as much more work will be required from the tropics next time round to assist, with angular momentum at a lower base level than it has been up to this -VE EAMT. Reasoning behind that has been given fully already this week. I don't personally, at this time, believe the Eurasian feedback signal on its own is enough. However, all of that is some way ahead. From my own point of view though, the evolution of the diagnostic remains the focal interest.

It is interesting that the NAO modelling 10 day and extended term towards middle month mirrors the underlying diagnostic, as explained yesterday, that creates a tanking -ve NAO. peaking and then reversing from that peak as the polar jet returns. Strong -ve NAO patterns, (as the video suggests that this one will be an example of), are the partner to the other couplet of the Northern Annular Mode where vigorous -ve zonal wind eddies at the border of the troposphere and stratosphere create robust retrograde of the -ve AO blocking structures, so much so, that the block gets so far west that the corresponding -ve NAO becomes ultimately becomes more and more west based and Atlantic lows are allowed to encroach increasingly north eastwards. Falling angular momentum during the first half of December will invite a fully retrograding pattern and that is why a peak intensity of cold potential (for NW Europe) *could* occur around the second week of December, peaking, and then leading to attempted breakdown towards/around mid-month with the -ve Annular Mode reversing polarity.

In response to your reply to me yesterday @Lord Baltimoreit could be that if I had equated the technical conversation to % of 'will it snow' then better understanding would have resulted. As it is you achieved a means to an end with reputation points. Addressing more generally, and very deliberately looking quite some long way ahead in synoptic context: For what little it is worth looking at one operational model from one suite in isolation, the GFS 06z follows the general evolution as per the (surplus to requirements diagnostic interest on the thread) for the whole period with, ultimately, an organised and potentially deep Atlantic trough set to start attempting to undercut established cold air across more northern/western and central Europe. This the start of a process of gradual attrition as Greenland blocking evolves an increasingly westward profile and -NAO more west based. But chances are that a tight frontal boundary battle edging NE'wards will eventually generate snow somewhere, at some time - if it has not happened already up to this time. Chances are it could be wet and windy also in others. . The latter chances of wet weather are clearly very high in SW Europe right from the much shorter term. Will it pan out precisely like the latest GFS run. No, of course not - but the overall synoptic medium to long term trend is supposed to be the takeaway from it. Let's see what actually happens for personal review purposes...

Boa tarde e todos. Excerto publicado da semana passada. There seems to be some belief, not sure what it is based on (beyond hope?) that the tropics are inextricably set to repeat a further active Pacific orbit later in December- both assumedly as means to keep (or reload) an anticipated cold pattern for NW Europe and as means to initiate a festive season SSW to set the path for winter 22/23 on an ice-age of yesteryear. Personally, at this time, I would very much question this based on empirical knowledge of tropical convection/MJO periodicity timelines. Active cycles, particularly seen during transitional ENSO phases (in this case a weakening Nina base state) follow an upwards of 60 to 90 days timeline recurrence for intraseasonal active progressions of the 'mini ENSO cycle'. The autumn has seen prolonged active cycling within the tropics focussed on West Pacific convergence, propagating +AAM anomalies to the extra tropics and carving out the very amplified downstream hemispheric patterns that are being seen. However, cycling of tropical forcing phasing, irrespective of long-term base state trends, both waxes...and wanes. A 'waning' of the sustained Nino-esque interference with the ENSO state is becoming increasingly overdue based on the periodicity cycle and suggests that the autumn of strongly a-typical high angular momentum decoupling of the atmosphere cannot continue indefinitely for yet further weeks to come. Ergo a fall /correction in angular momentum must be viewed within a lens of time ........................................................................................................................................................ Some further thoughts to this discussion through the lens of the GSDM (Global Synoptic Dynamical Model) : Tropical convection steadily fading in line with upper layer tropical waves. The convective impact on SST's will be to cool the surface - further underpinning the periodicity/timeline lag for future active tropical convection. Therefore, I would maintain any further significant convection less likely for a 6-8 week timespan allowing for a more coupled ocean/atmospheric signal than the highly destabilised regime of the past several weeks. Frictional torques lead mountain torques and with the former -ve c/o re-emerging trade wind inflection increasing across the tropics (as convection weakens) this implies that a tumble in mountain torque is signposted as means of the extra tropical wind-flow budget playing its part in the overall correction of relative and total angular momentum. Especially so given future lack of organisational MJO activity. NB: I do not deal in uncertainties of long term MJO forecasts but most especially given the inhibiting factors as revealed by the underlying diagnostic. The Global Wind Oscillation, a plot depiction of global wind-flow comprising both tropics and extra tropics, has trod a highly impressive quasi-stationary high angular momentum orbit for some time. Taking into consideration the weighting of -ve inertia to come, then a break in this +ve AAM (El Nino attractor phasing) has to be anticipated. Therefore, a breakaway GWO Phase 8.0,4 sequence sets up an intriguing passage for NWP to interpret synoptically- and certainly against so much amplified eddy inertia left within the global circulation at the same time as the polar jet attempts to return but potentially derailed by a tropospheric>stratospheric roadblock which, like any granite substance, takes time to splinter & fracture and without knowing where these fragments will disperse across the NH. An attempted musing sees me point to the remaining pockets of -ve zonal winds in the troposphere/stratosphere layer orchestrate with rarified retrogression of the substantial blocking structure to Greenland as inertia across the Pacific weakens (becomes more coupled to base state). Highly likely that this retrogression will eventually edge further east towards Canada (and try and evolve the pattern more -NAO west based) Before this however, a cyclonic envelope over my part of Iberia migrating northwards to bump up against the increasing CAA across more Northern and Western parts of Europe. This accords with a circa Phase 8/0 GWO signal as angular momentum retreats. Clearly a defined thermal boundary of very different airmasses setting up somewhere across these parts of Europe with large amounts of Atlantic moisture sourced from more southerly waters mixing with much drier, denser arctic sourced air. This clearly implies high impact weather event potential - no such detail can be given at this time as to where or when these will be. Further out, an attempt at reload is conceivable with the GWO en route back to Phase 4 and renewed rises in angular momentum tendency. However, heading back to the starting discussion of this post, there is great uncertainty about this - based on the said reasoning for tropical correction to re-assert a further active cycle. The chances are equal that this might not materialise/be delayed. So to reiterate, at least from my viewpoint, a lot of caution and restraint in over expectations of wholesale stratospheric destabilisation around the end of the year. At this stage, if it is to happen at all, closer to the mid-winter period seems more feasible. However, there are plenty of advanced pitfalls that can be foreseen, notwithstanding it is a ridiculous time period ahead to try to speculate. De nada. Os melhores cumprimentos. Ciao. Edit: For what it is worth, the ICON 12z shows a very 'clean' step up of returning polar jet energy. One of a myriad of solutions based on the tropopause zonal wind state which will not be modelled accurately from one output to the next and one computer model to the next. Yet another reason, as usual to not over analyse each and every roll-out (What is new about that)

Looking from some distance away from the UK and purely objectively about the seasonal pattern and not through the lens of a desired pattern: There seems to be some belief, not sure what it is based on (beyond hope?) that the tropics are inextricably set to repeat a further active Pacific orbit later in December- both assumedly as means to keep (or reload) an anticipated cold pattern for NW Europe and as means to initiate a festive season SSW to set the path for winter 22/23 on an ice-age of yesteryear. Personally, at this time, I would very much question this based on empirical knowledge of tropical convection/MJO periodicity timelines. Active cycles, particularly seen during transitional ENSO phases (in this case a weakening Nina base state) follow an upwards of 60 to 90 days timeline recurrence for intraseasonal active progressions of the 'mini ENSO cycle'. The autumn has seen prolonged active cycling within the tropics focussed on West Pacific convergence, propagating +AAM anomalies to the extra tropics and carving out the very amplified downstream hemispheric patterns that are being seen. However, cycling of tropical forcing phasing, irrespective of long-term base state trends, both waxes...and wanes. A 'waning' of the sustained Nino-esque interference with the ENSO state is becoming increasingly overdue based on the periodicity cycle and suggests that the autumn of strongly a-typical high angular momentum decoupling of the atmosphere cannot continue indefinitely for yet further weeks to come. Ergo a fall /correction in angular momentum must be viewed within a lens of time - which based on present long-term forcing may well further down the line spook NWP into something of an about-turn. Precise timing of this difficult to gauge at present, but becomes more and more likely heading further through December. The implication of this is some strength returning to the polar jet and pressure put on any mid-upper blocking pattern. With so much amplification inertia in the global atmospheric circulation, this may imply trough disruption rather than any wholesale downstream flatter zonal pattern, but clearly nothing should be taken for granted and a period of flatter Atlantic conditions is quite possible following the upcoming blocked pattern. If the tropics does witness a weaker cycle of tropical convection through later December into January, then this may imply that return to active cycling, (based on the 60 to 90 day periodicity timeline), results (possibly) in greater chance of renewed exertion on the tropospheric/stratospheric pathway being more likely around the mid-winter period - i.e mid to later January and even towards February. Such an SSW, not as automatic template to a classic arctic spell for the UK, but simply the means whereby a completely destabilised arctic profile might create the means for increased chance of cold air advection somewhere within the global mid latitudes Putting all this together, no-one should be making assumptions already than whatever develops over the coming 10 to 15 days for the UK (different implications for down here in Portugal with potential for some very wet conditions) is somehow going to set the way forward for an even bigger top up around the festive to New Year period. At some stage a collapse in AAM will be forthcoming, especially based on such an unstable disconnect, and if/when NWP latches onto this then modelling would undertake something of a volte face, Just something to bear in mind as caution to making any assumptions and some considerable potential uncertainty maybe to come as times moves forward.

NWP now following this suggested evolution. Sustained westerly wind propagation from the tropics to extra tropics now showing its accumulated lag effects of substantial blocking c/o robustly amplifying torque eddies within the extra tropics itself. The Gobal Wind Oscillation rooted in strong El Nino attractor phase orbit disconnect - reflective of a +ve windflow inertia disconnect to a weakening Nina base state. . How this blocked evolution further develops through into December will depend much on the stratospheric pathway and Brewer-Dobson circulation transport of ozone between the tropical and polar stratospheres. As suggested in the above post, there is no definitive one=track solution here. Notwithstanding that, the anomalously cold tropical stratosphere and active tropical convection very important in this development with potential implications which will no doubt be of very close watching for the majority audience of this thread. The Northern Annular Mode (AO and NAO) tends to form a more connected status (one way or the other) heading through December, and into January in particular. So as is typical at this time of year, stratospheric developments at this time forward are key, especially with so much anomalous momentum transport blocking so early on and at a time when the polar vortex traditionally would usually be organizing itself towards the pole. For me in Portugal this is setting up to be quite different pattern-wise to last autumn and winter. Clearly, for the UK the same applies - but with different implications and interests obviously. Boa noite e todos

There is no set-in stone x+y= formula. As stated, many times year on year. For a start, atmospheric circulation wind-flow inertia is acting 'very destructively' to the Nina base state which is showing some tangible signs of retreat. Both relative & total global angular momentum are some 2 standard deviations above average as anomalously strong westerly winds are energised c/o persistent and sustained active tropical convection propagating into the extra tropical circulation through torque eddy mechanisms and aided by direction of travel of the solar cycle. This, as far as I am concerned at least, sets up an interesting duel between the Ferrel & Polar cells. Likelihood of height rises into southern Europe around or just beyond the 10-day period and a strong thermal gradient persisting towards 50N and squeeze of the jet stream accelerating secondary features around the base of the Greenland segment of the polar vortex. Between the height rises across Iberia and central Mediterranean and the Russian heights. As things stand, a migration of downstream southern European heights is more likely to link with the east European/Russian heights across central mainland Europe as the core vortex edges subtly westwards. High pressure, eventually, the most likely solution (at the moment) also towards NW Europe but, beyond hope-casting, little (yet at least) to suggest this will inextricably evolve further still into a northern block. Irrespective of very long range modelled 46 day suites etc which I freely admit I largely ignore whatever the time or season. Other than solar considerations there are longer term superimposed effects of warming that are intensifying sub-tropical ridging responses year on year and in winter it is requiring ever stronger stratospheric instability to create deep cold air advection across larger hemispheric areas of mid latitudes. Modelled stratospheric forecasts are a tombola at distances of two weeks and more and too much can be read into them in my opinion. None of this is to preclude some cold weather patterns at some time in the future during winter in NW Europe. But from my point of view, wholly ambivalent (and detached) as I am about chasing cold weather and snow, the macro global set-up in respect of this tropics/polar duel is the fascination going forward. Attempting to fit tropical & extra tropical forcing diagnostics and resultant wind-flow patterns into a desired pattern (whatever the time of year) will more often than not result in error and human frustration. A myriad of longer-term outcomes in respect of surface conditions and vectors of milder/colder air is possible at this time- even if the ultimate direction of travel is eventually less unsettled and more blocked and anticyclonic. Com os melhores cumprimentos

Boa tarde e todos For many in the UK thinking about their energy and fuel bills, it will be seen as such. The reasoning for the extended sub-tropical amplification is quite easy to identify. It is not to be found in MJO tropical composites in isolation, it is found by looking at the global atmospheric circulation which also takes into account the extra=tropical circulation to mid and higher latitudes in respect of how wind-flows propagate between the tropics and extra tropics and interact together. If we look at frictional surface torques (largely a blueprint for setting the path and strength of the Jetstream) then westerly wind bursts are clearly identified propagating from the tropics along a convergence at 30N (shaded orange) where they are puncturing holes in the Nina trade winds (shaded blue) along the dateline. The amount of westerlies being added c/o tropical forcing and propagating into the extra-tropical circulation is far outweighing the underlying walker circulation c/o the ENSO circulation base state. The westerlies are propagating from the tropics into the mid latitudes' c/o strong East Asian Mountain torque (red line) and creating a downstream trough/ridge/trough/ridge pattern between the Pacific/US/Atlantic & Europe. The latter trough/ridge amplification being in the Atlantic and European sectors respectively. Accordingly, the Globa Wind Oscillation (GWO), a phase plot depiction of wind-flow inertia combined in the tropics AND extra tropics, reflects an El Nino-esque GWO Phase 5 to 7 orbit - representing surfeit westerly propagation through the global extra tropical circulation with total and relative angular momentum close to 2 STD (standard deviations) above average. A clear reversal, over all at present, of the walker circulation. Based on the underlying Nina base state, the present 'mini-ENSO' cycle wave therefore represents quite a remarkably sustained a-typical departure forcing from this - which has already created intra-seasonal lagged feedbacks that will be having a say in the weather patterns for the rest of 2022. This, even when the westerly inertia and corresponding WPAC/CPAC convergence fades and the walker circulation begins to re-assert naturally based on the cyclical nature of tropical>extra-tropical forcing. Putting this all together and based on a fairly neutral stratospheric>tropospheric backdrop for the time of year, there is continued likelihood of downstream ridging - perhaps edging a little north-west with time to be in the vicinity of NW Europe and the UK. So more settled conditions taking over as weather fronts are deflected further NW and anticyclonic late autumn conditions bed in. Before that furthest extended period, in my part of SW Europe, likely remaining quite warm and with out of season convection perhaps spiralling around from the Azores region c/o a weakly negative NAO at the lower base of meandering and 'stuck' Atlantic upper troughing. Recent sub-tropical Atlantic flow bought some very welcome rains to ease the drought a little along with a few embedded thunderstorms. The Iberian continent as a whole has broken some amazing heat records during both September & October. For UK/NW Europe, after some further unsettled weather to come into next week, southerly winds flanking around the downstream European ridge could well advect some of this autumnal warmth and provide some protection, for a while anyway, in respect of the backdrop of energy bills and heating difficulties - and keeping in mind that later on seasonal frost and fog becomes more and more likely as the end of autumn approaches with winds falling light as high pressure moves closer and becomes more and more dominant.

I have made a few posts about this subject - a latest one the other day back. A La Nina phase, in a "constructive" "waxing" tropical<extra tropical cycle (i,e the ocean and atmospheric feedbacks aligned close together) does align on a synoptic level to a Pacific wavelength to a dominant Pacific sub tropical ridge and downstream corresponding dominant Azores ridge . According to seasonal wavelengths and the time of year, this is subject to discontinuous retrogression processes which involve falling pressure slotting in place as the ridging retrogresses. However, (as is also the case with El Nino) the ENSO Nina cycle also has "waning" cycles where high frequency tropical signal, and interlinked QBO and polar feedbacks can "destructively" interfere with the dominant low frequency signal and/or act to shift tropical convection convergence zones in such a way as to subtly alter the mainstream synoptic feedback pattern.. Such a-typical forcing can happen at any time of year. A-typical forcing was present in both the winter of 2017/18 (which disrupted the polar vortex) and again in the summer of 2018 (as a slow and erratic switch to more neutral conditions became underway). A similar a-typical pattern, in some ways, has been present this summer with a subtly eastward adjustment of the upstream pattern that has led to the strong and dominant Azores/Atlantic ridging to have a much more influential effect on the European downstream pattern. Summer 2021 was a more traditional Nina-esque response in this respect. And then there is climate forcing which is throwing some of the researched analogue and composites out of the window. Much as posted and discussed last month. Following the present NW Europe heatwave ( is is not really heatwave territory down here at the moment and present conditions are being classed by the IPMA Portuguese authorities as "typical summer conditions") it will be interesting to see how the next La Nina kick to the cycle plays out as the feedbacks this summer are very powerful and this autumn could well feature a strong intra-seasonal CCKW (convectively coupled kelvin wave) to shake things up further.

Your posts are very "La Nina x+y= centric". Such selective confirmation bias processes are deeply flawed in reality. As stated so many times (on the few occasions I post on this thread), attempting to use tropical convection composites to fit a desired outcome is erroneous especially when it omits to consider the wider extra tropical impacts and atmospheric circulation. The two do not always "co-operate" and produce a harmonious wind-flow (jet stream strength and path) signal. Whilst something of a renewed La Nina kick is coming to the atmosphere, there is such a strong amplified eastward adjusted sub triopical (Azores High) and -ve polar field (+AO) imprint on the atmosphere that achieving the type of pattern that you crave (cool wet and unsettled) is not sustainable beyond a trough splitting the anticyclonic chain strung across from the Atlantic into Europe - before the ridge re-asserts. Wavelength changes heading into early autumn and as the intensely strong ferrel cell starts to relax and a stronger temperature gradient begins to show across the mid latitudes to energise the jet stream may start to generate a more mobile pattern - but a sustained breakdown of the dominant summer pattern is unlikely just yet. To put these comments about"extreme heat" into context. Values over 40C have become common place since mid July across the Iberian continent. Values this coming week across the UK are "very hot" certainly but are not likely to be close to repeating the unprecedented heat of July when 40C was broken for the first time. Mid 30's is indeed very hot - but it is far from unprecedented. The greater question is how this amplifies the drought issues, rather than the actual temperatures themselves. Extreme is a word that definitely applies in relative terms in these southern most parts of Europe- and where the wait for rain is likely to be longer still than it is for those that need it in southern UK. Perspective is everything. Just to add - aside from the environmental issues and heat impacts for those susceptible to heat - for many the coming week in the UK will be highly welcomed and enjoyed both for general outdoor activities and holidaymakers alike. These people should not be made to feel guilty for enjoying it and the benefits of Vitamin D which will be much needed with some of the bigger wider problems and hardships of the winter to come.

The showers and mid level convection should not be a surprise. The blazing heat last week here In Portugal, ahead of the same airmass heading north this weekend, was characterised by a lot of mid level cloud (mixed with wildfire smoke) and the amounts of sunshine locally were actually very low for much of the week. The days that the temperature hit the highest 40s values were Tuesday to Thursday.....and were cloudy for large parts of the day. There was even some convective sporadic splashes of rain on Weds amidst a quite thundery looking sky around mid morning. Temps at that time about 37C. The cloud broke for a couple of hours, a blazing hot wind from the SE kicked in and the peak of the heatwave happened early to mid afternoon around 45C This airmass has changed next to nothing on it way northwards. Cloud and a few showers is very much part of what was the Portuguese experience. Those relatively lower geopotential heights that have sat off the coast locally here and are now heading north east are a driving force in pumping the intense heat advection. This is one plume where every bit of surprise cloud cover which you are tempted to think leads to suppression of the heat - is actually an evolution to greater heat still afterwards. Its coming. Boa noite e boa sorte

The 12z GFS is utterly insane for the UK for Tuesday. The widespread 40/41/42C values modelled in the afternoon are, genuinely, barely a smidge lower than what the model was suggesting for my locality in Portugal last week ! And that heat, fanned about by a fiery desert type breeze is an experience never to forget and it is (was) necessary to seek protection out of both the sun and the wind. A brisk southerly breeze is also predicted to be blowing across the middle/eastern part of the UK to accompany those temperatures and would add a wind burn effect much the same principle of accentuated wind chill with extreme cold in winter, Hard to avoid hyperbole. It is perfectly feasible. If this does indeed happen then it is sensational for the UK in respect of meteorological history. As another perspective, it is one thing to experience this kind of heat in small semi urban/countryside type locations with UHI much less of a factor and (relatively) cleaner air, but major cities in the UK are really going to struggle to function if this is anywhere close to the reality on the day. Before than the record (various records) still very likely to go anyway tomorrow.

Thankfully the worst of the heat is now departing here - as it makes its way northwards towards France, and then on towards UK and low countries. But actual values here in Portugal have exceeded modelling during the last weeks heatwave. There have been sudden extra heat surges and in a a few places foehn effects that have produced some alarming figures ramping up over 46C before wind switches to the west off the Atlantic have dropped those figures by up to 10 degrees or more in very short time, before rising and falling yet again in a similar way I keep repeating, this is no ordinary summer heatwave. it might be brief at the UK latitude, but the thicknesses, razor dry dewpoints and very high upper temperatures are a rare combination for such a latitude, and which have already been producing extreme results very easily even for places more accustomed to hot weather and that will also be the case when it gets to the UK - even if mid 40s is off the table.. The key message is that this airmass is an unusual one to get as far north as it is now predicted to do so. On that basis debates over which model is closest etc is, at least somewhat muted. In my view they are more likely to underdo this particular airmass in the same way as they did here on the Iberian peninsula. ECM predicted 40/41C locally mid week - the reality was over 45C. GFS went a degree or so higher than ECM, but still didn't quite model the 45/46C readings. These actual recorded weather station temperatures c/o IPMA (Portuguese equiv of METO) for the same time midweek are littered with readings above the numerical model predictions Furthermore, the highest reading at the peak of the heatwave in Portugal was at Pinhao in the northern most part of the country at 47C and not in the more southern interior as is usually always the case. That is unusual in itself. I equally therefore think that a vey open mind will be needed for weather/model watchers in respect of mid-upper 30s predictions verifying actual recorded values into the lowest 40s over the coming few days

Yes indeed. Let me put it this way, here in my locality in Portugal the GFS was not modelling 37C at 9am in the morning! I think there is too much emphasis on the breakdown (as always) which everyone knows is coming and not enough on the sheer intensity of this heat while it is in place. Take it from me, this is the same airmass I have encountered this week and I can vouch for the insanity of it. Better than coming from me, the natives who have lived through plenty of southern European heatwaves have been astonished by it. The relative brevity of it risks undermining the unprecedent magnitude of the heat intensity of it.

These upper air temperature anomaly chart say it all. The very most intense heat just starting to shift away north eastwards from my location (though still hot) and arriving in the UK to start next week. So a welcome cool down on the way down here at the time that the UK goes into the fire. Have never experienced anything like this before. Mid level cloud/wildfire smoke laden skies and fitful torching winds that suddenly switch to the "nortada" (resident NW afternoon breeze from the Atlantic) and tumbling the temperature by over 10 degrees in 30 min periods each late afternoon. The airmass is indeed very dry and a large factor in exacerbating the fire risks, fanned by the variable winds. The modelled temperature profiles are highly realistic with the nature of this brutally hot & dry airmass. Fully expect the record both by day and night to be smashed in the UK on both Monday & Tuesday. Discussion over the timing of the breakdown over the UK is mute really in respect of the sheer severity of the heat early next week. This airmass has such forward momentum, having built up over the last week and more over SW Europe being fed by the lower geopotential heights off the Portuguese coast propagating cinder dry heat from NW Africa and truly desert type conditions. It will lose next to nothing of this on its journey north and some truly exceptional weather is on its way for much of NW Europe In terms of the macro pattern, a lot head scratching needs to be done in respect of what has been learnt diagnostically with regard to tropical.extra tropical forcing. I think that there is now so much superimposed forcing on Mother Nature's natural balance in respect of laws of conservation of angular momentum, that composite forecasting is heading out of the window and needs re-drawing. Personally I have become more and more detached from both MJO & GWO forecast compositing and taken proxy data very much on the basis that evolution of wind-flow pattern forcing within the atmospheric circulation has to be taken on individual merits at any given time. This does not debunk it by any means, but it does imply that there has to be recognition that there is so much additional forcing and added inertia as Mother Nature cannot abhor a vacuum, that has outdated some of the highly regarded conceptual frame-working that has been achieved over the last decade and more. Simply put, the global climate has already outrun the templates of such forecasting and it needs to be, somehow, re-drawn All that said, some things can still be reasonably rationalised & expected based on proxies. Solid wall of trade winds persist at the dateline But convergence of tropical forcing has subtly started to trickle from the Maritimes (classic Nina standing wave) into the Western Pacific c/o warming of SST's there since late Spring. The deterministic MJO plots do not depict what the velocity potential convection anomalies are reflecting via low frequency signals in the Pacific. Put together, this supports continued rebuild of the Azores High eastwards, potential for further heat-pump shallow lows to the wast of the Iberian continent and therefore, whilst not presently coherent in NWP, a potential further build back of heat from southern Europe has to be watched in days to come. On that basis the breakdown of the inferno next week should not be taken at face value as any longer term shift to cooler and more changeable conditions. Based on the periodicity re-cycling of thee momentum cycles, August may raise some more eyebrows....

Boa tarde e todos Here in Portugal, a lot of weather stations recorded over 45C yesterday and one or two not that far at all from my location. Utterly freaky conditions with a combination of mid upper cloud that looks convective in nature overlaid with sooty deposits from the terrible wildfires going on. The sun has taken on a hippy vibe colour through the spectrum of deposits in the atmosphere. The wind direction blowing one minute from the interior with noticeable extra surges in the heat level and the switching to the west and gusting strongly blowing in air from the Atlantic and fast drops in temperature by over 10 degrees in less than 30 minutes.. Today is similar, with an expected faster drop in temperature in the next couple of hours as the Atlantic breeze is more widespread and stronger. All of this is highly relevant to the modelled movement of this searing heat dome and what might be expected northwards through Europe and into the UK next week. It is very unlikely to be the 45C values, but in truth not too far behind. This airmass will likely be carrying the Saharan/wildfire mix - so atmospheric conditions could be equally as challenging and maybe more so bearing in mind these kind of conditions are much less common in NW Europe, and particularly the UK. Down here the actual recorded maximums have exceeded the modelled suggestions, including most of the high resolution models - so while as stated, 45C seems too much of a sensational leap in the UK - it might be wise to expected the unexpected and on that basis values of 40C /41C are certainly realistic. This is not a normal type of plume - it has sat and stagnated for several days with heat building on heat accruing a 'dirty sky' mix and it is genuinely quite a surreal experience. Plenty to look out for in the UK. At it starts to ease down here through this weekend - watch out, its coming your way..

The talk about cloud is interesting and how much it tempers heat. It is cloudy here since breakfast time with the sun obscured by a mass of dusty Saharan like mid-upper cloud.....and it is 40C. It is quite something to experience, with a breeze blowing from the Iberian continental interior and adding a searing fan oven effect. Thankful though, same as yesterday for the mercy of no sun which makes it surreal to look out the window at a beige light greyness but then feel strumming heat pressing on the glass. These are the ECM ensembles from this morning for my location, screenshotted towards the beginning of next week : Tomorrow is a day. frankly, to want to miss and wake up on Thursday. From Thursday there is a very gradual descent into the weekend. 35C max approx by Saturday, which seems to have reasonable consensus, will seem like a stroll in the park after this, and with night-time values also starting to drop below 20C. Then after that it becomes more like the summer I love to enjoy here with mean values hopefully back around the 30C to 33C mark by day into next week and warm but comfortable nights in the mid to high teens.. So you get some idea of the nature of the airmass that will be moving north into France and other parts of continental Europe later this week and then knocks on the door of the UK. As posted a few days back, the small area of lower geopotential heights just off the coast here in Portugal is quite a player in the movement of this intense heat dome and how it interacts with the very strong and extensive Azores anticyclone ridge which is trapping this inferno like North African airmass beneath it. The breakdown of this intense heatwave, as described already, will be very gradual here day by day with no real change in weather. And no rain, though there is a chance of a few thundery showers for some parts later next weekend into next week, depending how the heat low behaves. That scenario had been modelled at the weekend to happen later this week - but it shows how the movement of the low off the Atlantic coast here has been tricky - and how it interacts with the plume As for the UK it is much more uncertain (as always) but a reload of the Azores High extension is quite possible when a breakdown comes, sometime next week. It is always interesting to look at weather records and a fascinating discussion. In practical terms though these sorts of 40C and above values are not much fun and make doing anything very difficult both for human kind and beast. The cloud cover today has certainly spared the added intensity of the sun which would have made doing anything outdoors out of the shade completely impossible. Splashing water around required to get through this - though that is a commodity that is in short supply.

I am about an hour inland from the Atlantic coast and the breeze plays a very crucial role here. Today is a good example. There is heat that is taking some getting used out here since Thursday. Values yesterday close to 40C by mid late afternoon and then the breeze kicking in and bringing it down to about 34C by early evening. Still hot, but enough to get outside and do watering etc as the sun starts to lower in the sky. Today has gone a step further over 40C and its a case again of sitting it out till the breeze kicks in. Which it just has, again from the NW and earlier than yesterday. Computer predictions are for a slightly faster fall in temperatures this coming evening - and tomorrow faster still as some subtly lower geopotential heights encroach from the Atlantic. Monday looks quite blissful by comparison with 'only' 34/35C after a polar night right down to about 17C! This doesn't last as the 40C+ heat returns for Tuesday and at least Wednesday. That is where it gets interesting both locally and from the macro picture ahead for further north in Europe and of course for the UK. Yet another of these very shallow lower geopotential heights meanders off the Portuguese coast and at the same time engages much like the last plume event back in June and surges the Iberian heat northwards late next week the same way. This of course is much more intense than last time. A chance though , fingers crossed, that from Thursday and the end of the week it cools off a little down here (still quite hot) and with the odd thundery shower dotted about. For the UK its all about the modelling of how these Iberian shallow lows engage with the plume and create a defined thermal boundary that creates it own momentum with how far north the intense heat boundary heads. In terms of the diagnostic, the situation with July wavelengths and the intensity of the sub tropical ridging means that the heat will not be dislodged as quickly most likely as the previous plume. Much of this is tied into the tropical cycle propagation of westerly wind inertia from the tropics propagating into the extra tropics and bolstering the ridging much more. The westerly winds getting cut off implies greater ascendancy returning to the mid Atlantic ridging and a weakening of the eastwards extension of that ridging and a discernible pattern change back to something closer to average. But it is not that straightforward because the situation upstream has been subtly changing in recent weeks with a weakening of the Nina standing wave and some re-configuring of tropical convection convergence in the Pacific. That means that pattern re-sets are possible with re-assertion of the present situation. An especially tricky longer term outlook, but there is clearly a chance that some of this intense heat will also threaten at least southern UK by next weekend - pending how the subtly lower heights to 'my' west engage with the heat as it tries to edge further into Europe from the SW. I for one, who loves summer weather will be relieved to see the back of these 40 degree figures asap. Its far too much and the drought and fire situation is serious enough at it is.

If a diagnostic is not attempted to gauge the turning forces (angular momentum) exerting within the global atmospheric circulation (which is a key determiner of the where the jet stream ebbs and flows around the globe) then that is one vital key missing that inevitably guarantees error - however difficult and complex it still remains to predict weather patterns even for the most experienced. Such an approach though is anything but retrospective. Low angular momentum has indeed predominated this month and the signature Atlantic ridge has advertised that very accurately and clearly - and within keeping of stated expectations.. The effects of eastward propagating tropical convection within the MJO "mini ENSO cycle" can be seen on this chart in respect of the temporary rise in momentum during May - according to a convectively coupled kelvin wave passing through the tropical Pacific ocean and briefly interrupting the domination of of the La Nina standing wave throughout the bulk of the Spring season, This dominating Nina forcing continuing into the new season, and according to early summer wavelengths in tandem with a summer arctic profile which has not been exerting any particular sustained suppression at mid latitudes amidst a generally wavy and quite weak jet stream, and so has still allowed some ridge extension of the main height anomaly, fixed to the west, eastwards towards Europe with trough disruption dropping southwards towards Iberia around the perimeter of the main anticyclone. Quite typical for La Nina June/ early summer - and a pattern that often allows (usually fairly brief) warm air advection around the eastern flanks of such southward disruption The equation changes heading through July, with the switch to peak summer wavelengths. If the atmospheric circulation remains as it is now with easterly trade winds (shaded blue up to the dateline) perpetuating both Pacific and downstream responding Atlantic amplified sub tropical ridges... .....then there will become a tendency for cooler more unsettled conditions to be longer lasting and harder to move on as the Atlantic ridging becomes increasingly further retracted and suppressed and less inclination for trough disruption just west of Europe, but making greater inroads instead through NW Europe and Scandinavia. On the other hand, should eastward moving tropical convection re-configure the upstream pattern with westerly wind additions to the atmospheric circulation across the tropics (which would be red shading towards the dateline on the Hovmollers plot above) - then rising frictional and mountain torques will help de-amplify the upstream amplification and replace the Atlantic ridge with increased troughing and in turn the greater high pressure anomaly will be adjusted as downstream ridging cross Europe. This set-up increases the chance of more sustained heat build advected northwards from Africa and southern Europe adjusted further westwards towards NW Europe - rather than under a La Nina displaced Azores ridge regime in mid Atlantic where heat advection favours more central and eastern parts of Europe (and Russia) downstream of a NW European trough So there are some broad indicators to watch for heading into July as to which way the pattern may evolve. Nothing is black or white, and some kind of pattern half way house may develop depending on what extent rally in momentum may occur. NB: Tropical convection patterns need to be viewed within the context of how wind eddies propagate further to the extra tropics. Changing wavelengths within seasons and indeed from one month to another make subtle differences to how the macro pattern evolves according to tropical>extra tropical wind-flow signals. But that said, as is the case in winter, there tends to be a closer relationship at these peak opposite seasons of the Annular Mode (AO and NAO in this relevant part of the hemisphere) than during the transitional parts of the year. On that basis there is a decently observed correlation year on year that La Nina-esque July's to be less forgiving than in June. So with this in mind in it is important to return to Paragraph 1 and keep attempting these diagnostic inspections. That is clearly pro active and not reactive to events.

Posted on Sunday and copied for purposes of update : .............................................. The cue for the end of the heat heading into midweek down here is the cue for the heat plume at the same time to head northwards through France towards the UK as well as eastwards into central Europe. With a defined thermal boundary setting up between the heat ridge over mainland Europe and a cold front to the NW of the UK coming around the perimeter of a typical early summer Nina-esque Atlantic ridge, it sets up the prospect of quite a distinct boundary of error either side, as it tries to head SE. There is little likelihood that the Atlantic ridge will decline and help sustain any ridge further east into the medium and longer term with tropical convection now slumbering after an active period. On that basis, angular momentum has no upwards push from a suppressed level This favours sub tropical ridging holding to the west of UK and mainland Europe. So its a matter of time how long the heat ridge can hold into the weekend in NW Europe and more particularly the UK closest to the cold front and the energy coming around the perimeter of the Atlantic ridge. A cut off low forming along the cold front boundary and sinking south on the eastern flank of the Atlantic ridge is certainly quite possible. The further west such a development might happen implies this scenario slowing down/delaying the cool air advection at least for a day or maybe even two over next weekend itself. Ultimately the numerical modelling looks accurate in sharpening the Atlantic ridge and fully pushing the cooler air south eastwards into the next week, if it does get delayed a little during the weekend - more especially the further south and east one heads.. ................................................ It has been interesting watching the progress of the developments as discussed above, and so it has proved that the heat plume looks to be harder to dislodge than the numerical models had been suggesting up to the weekend. The first partial breakdown of the heat is underway here in the Western most part of the Iberian continent. A subtle boundary between the very hot air from Africa is the focus of some overlay by moist Atlantic air to the west and has resulted in something of a destabilisation of the atmosphere in the mid levels with elevated thunderstorms tracking from south to north from the Algarve coast through the Alentejo regions to central Portugal along this airmass boundary in a defined finger of mid level convection. So the first proper rain to dampen the ground here since probably April. More booms of thunder as I type. This very shallow ring of lower geopotential heights just off the Portuguese coast plays a subtle part over the coming days as the plume advects further north and north east towards NW and central Europe. It provides a prop for the anomalous Atlantic ridge as a further more expansive thermal low also develop across North West Spain & France along the same western boundary of the plume - and which blocks the cool air advection around the North Atlantic ridge from pushing more quickly south and keeps at least southern parts of the UK in the very warm upper airmass for longer. Meantime as the plume lifts north, larger amounts of Atlantic sourced air pushes into the Iberian continent. Relative to the 35C to 38C heat of the past 10 days, a much cooler spell of weather lies ahead. Though these ensemble values for the coming couple of days will still seem reasonably warm by UK perspectives, the values from Sunday are several degrees below average for this latitude. Comfortable for outdoor work though! As stated in the quoted post, there is no prospect of the mid Atlantic ridge declining, though the toppling ridge overlaying the thundery trough over France keeps warmer upper air much closer to southern and some eastern parts of the UK for considerably longer than modelling suggested a few days back. Mid term, upper troughing is clearly advertised to dig south with the Atlantic/Azores ridge displaced well to the west of Europe in general. So heading through next week the cooler North Atlantic air eventually makes inroads across larger parts of NW Europe. This is consistent with continued low angular momentum, renewed trade winds across the greater part of the tropics as MJO related convection activity is camped across the Indian Ocean with little amplitude and eastward progression suggested for the foreseeable future. This becomes of greater significance as July high summer wavelengths approach. Continued suppressed convection and trade wind activity preventing westerly wind bursts creating eddies in the jet downstream and therefore reconfiguring heights back into Europe is the likely eventuality in such circumstances. However, if there are signs that renewed convection starts to progress eastwards then this leads to the promise of further summery weather returning to many parts of Europe. Aproveite o tempo agradável durante o resto da semana.

Boa tarde para todos e todos?? Very hot down here since Friday with mid 20s through the first half of last week,heating up to mid/upper 30'sC this weekend by day. Overnight mins between 20 to 22C shortly before dawn.. The extra strength of the sun at this latitude is particularly powerful and requires respect. .Living in these conditions while they last is quite different to any holiday! Less than 100km to the west around the Portugal/Spain border, truly scorching heat is evident with values up to 43C. In this kind of scenario, breezes from the exposed Atlantic coast extend just far enough to here to prevent those values - and after about 4pm the highest values tend to start dropping back a little as the breeze kicks in. The cue for the end of the heat heading into midweek down here is the cue for the heat plume at the same time to head northwards through France towards the UK as well as eastwards into central Europe. With a defined thermal boundary setting up between the heat ridge over mainland Europe and a cold front to the NW of the UK coming around the perimeter of a typical early summer Nina-esque Atlantic ridge, it sets up the prospect of quite a distinct boundary of error either side, as it tries to head SE. There is little likelihood that the Atlantic ridge will decline and help sustain any ridge further east into the medium and longer term with tropical convection now slumbering after an active period. On that basis, angular momentum has no upwards push from a suppressed level This favours sub tropical ridging holding to the west of UK and mainland Europe. So its a matter of time how long the heat ridge can hold into the weekend in NW Europe and more particularly the UK closest to the cold front and the energy coming around the perimeter of the Atlantic ridge. A cut off low forming along the cold front boundary and sinking south on the eastern flank of the Atlantic ridge is certainly quite possible. The further west such a development might happen implies this scenario slowing down/delaying the cool air advection at least for a day or maybe even two over next weekend itself. Ultimately the numerical modelling looks accurate in sharpening the Atlantic ridge and fully pushing the cooler air south eastwards into the next week, if it does get delayed a little during the weekend - more especially the further south and east one heads.. Down here in my part of Portugal that suggests brisk N winds by day around the resident Azores High - moderating temperatures in the mid to upper 20sC and with pleasant nights in the mid to upper teens. So lovely summer conditions, albeit the drought remains a large issue. Small chance of cut off lows in the Azores region edging towards the Iberian continent may provide a few thundery showers. Such as happened occasionally last summer. For the UK, clearly less straightforward with upper westerlies across the North Atlantic and more likely changeable conditions and the predictable interplay between the ridge to the west and south west and fronts coming across the top of the high. Based on the nature of the summer easterly profile across the arctic, there is little sign of any substantive or sustaining heights over that region overly suppressing the jet stream - so any temporary rises in momentum should allow the Azores High to ridge a bit further north east from time to time. Um domingo feliz

Olá a todos A lot of momentum transfers in progress across the global atmospheric circulation at present - with a reversal in process of some strong momentum transport which had built strong downstream sub tropical ridging across large parts of Europe and also some very significant early heat at the end of last week and into the weekend to parts of Iberia extending into France and central parts of Europe. Reversal of frictional and then extra tropical torques ls set to lead to a retrogressive pull from upstream and hence the advertised NE Atlantic blocking c/o deceleration of zonal winds around 55 to 60N. This retrogression is then set to further adjust the pattern westwards as a precursor to yet another lunge upwards of momentum as significant tropical convection traverses the Pacific heading into June. The result being to presage the return of a European downstream ridge in the extended period. This, in tandem with seasonal wavelength changes heading into June, bodes a good chance that heat advection may cover larger parts of NW Europe, including the UK. This type of pattern potentially could lead to a rinse and repeating of thundery lows breaking off a main trough in the Atlantic down to the Azores region which move northwards, followed by re-set of hot sunshine. The inference of all this is for those in the UK and more NW parts of Europe not to read too much into programmed blocking south of Greenland as there is a reasoned chance that this is one of those times when it is in itself just part of a stepping stone process towards something much more summery. Should that happen, how long that in turn holds is clearly subject to time and further analysis, especially set against a stubbornly Nina background. But it is still well in keeping with many La Nina June/early summer patterns, particularly those with an active & unstable Maritime/ Western Pacific tropical convection convergence pattern with westerly wind bursts challenging the date line, booting angular momentum tendency and creating downstream eddies and amplification

Boa tarde The anomalous high pressure belt across the Azores as part of the strongly +AO/NAO pattern through the winter has made it extremely dry in my part of Europe (and across the Iberian continent in general). By contrast the UK has moved from the dryness of January into a very stormy pattern as the upper vortex and intense sub tropical ridging have sandwiched a persistent slow moving baroclinic zone where cold arctic air from Canada has engaged the warm sub tropical air to the south and deep low pressure areas spawning on the accelerated jet gradient. With globally averaged angular momentum supressed, which favours an accelerated polar jet, the predominant low arctic heights will await a seasonal wavelength stimulus to weaken them and start to change the macro scale pattern based on tropical convection, in tandem with this vortex weakening, moving eastward from the maritime continent back to the Pacific. With that in mind it makes sense that March is indicated to persist with the upper westerly pattern above 50N with the compensating easterly trade winds underpinning the low angular momentum conditions from the tropics into the extra tropics. However, with seasonal wavelength changes in mind, there will come a point sooner or later where something has to give and force a pattern change. On that basis it makes sense to watch through the coming weeks for signals of this - as persistent patters have a habit of suddenly tripping up and forcing a volte face in numerical modelling out of its rut. This doesn't necessarily imply warm dry March/wet cool remainder of Spring and then Summer as has happened in some years where March has seen this kind of springlike +AO/NAO pattern- it is simply a case of looking out for the nature of the break up of the seasonal vortex and whether it is a measured, steady warming at higher latitudes towards standard summer polar easterlies, or, is the type that is an abrupt final warming and forces a blocked higher latitude pattern and phasing of the jet stream southward. Its too early to say, but there is something of a hunch that this Spring is set to see rising momentum as La Nina dissipates leading to a phase of cool blocked and showery conditions by April but, assuming momentum stays buoyant, a gradual switch to warmer and drier conditions in NW Europe heading through the middle and more especially latter part of the Spring. This sort of evolution along the way, might help relieve the drought in my part of the world - which is wholly required to happen to help tone down a host of problems for the eco system come Summer if it doesn't happen. It also would exacerbate the intensity of usual seasonal heatwaves leading to even greater difficulties. For now, it continues with beautiful blue skies, wall to wall sunshine and quite surreal trying to keep remembering that it is still technically winter with a week of February remaining. The expected high today towards the mid 20s. As of 1.30pm it was at 22C.

Its self quoting as i sometimes do - but like to revisit these things as they evolve The red warning did come after all then- and that is very significant to me in respect certainly for my own old location, which traditionally is windier close to the coast and therefore takes a greater degree of impact in relative terms than further inland to merit a red warning. All my time living there, there wasn't (at least from memory) ever a red warning produced. Though that could admittedly be proved wrong going back to one of the stronger storms in the 00 decade which is a long time in the memory vaults of severe weather events. Notwithstanding that though, looking at the high resolution modelling - the SE coastal strip looks to now be seeing wind gusts perhaps in excess of 80mph and therefore maybe a tad stronger than the 2013/14 storm referenced in yesterdays post. My Portuguese friend, who has been back in the UK for a while, says that she lost both internet and power late morning and many people apparently are without power between Hastings and Bexhill and fallen trees are blocking roads around both towns. She is located quite close to the seafront, a street away from it - so little to protect from the exposure of the gusts coming off the channel. . Other than flickering lights and bits of roofing coming off the power stayed intact during the windstorms I lived in the locality. So am quite happy to be missing out on any of that for sure. I think wherever one might be in the UK, and whether in the path of the storm or not - the prevailing view should be that this has evolved into quite a noteworthy storm and one that is certainly matching the numerical modelling of it as predicted in the build up to it