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Tamara

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Everything posted by Tamara

  1. Fast approaching the last week of May, it looks increasingly likely that summer won't be arriving with global atmospheric angular momentum in below average territory. This means that the direction of travel continues to be quite different to other e/QBO & ENSO cooling summers like 2007 which saw very strong coupling of atmosphere and ocean right at the time spring moved into summer. Angular momentum crashing spectacularly on that occasion. Based especially on seasonal wavelength changes to summer - stable AAM is very counter intuitive to any sustained Atlantic retrogressed ridging and downstream trough. What a slight weakening of the eastern flank of the downstream ridging, and some attempted inroads of the trough to the NW might indicate is the completion of the robust intra-seasonal convectively coupled kelvin wave (CCKW) at present propagating eastwards across the tropics and due to pass through the Pacific in the remainder of this month. It is at this completion point in the "mini ENSO cycle" that angular momentum edges back somewhat. Suppression of convection occurs across the Pacific as the convective element moves on towards the African continent and Western Hemisphere. As atmospheric stability returns to the ENSO region in the wake of the CCKW, then this leads to trade wind inertia increase and a rise in pressure which in turn retrogrades the downstream wavelength and the sub tropical highs in the Atlantic (Bermuda and Azores) NWP will be anticipating the wind-flow inertia switch at this time, but as previously, they may over-egg the fall in momentum budget tendency based on global overall parity of momentum. This means they may either overdo the degree of retrogression/ fall of pressure close to the UK and/or the time period any such indicated switch of pattern lasts. As long as heat content across the tropics as a whole, and irrespective of the cooling in the Pacific, remains anomalously warm, this is conducive to further downstream summertime sub tropical ridging and the upstream pattern allowing the ridging to adjust back towards Western Europe. The reason being that angular momentum tendency is buoyed by such an SST basin arrangement & supports further MJO related activity and westerly wind inertia continuing to be propagated from the tropics to the extra tropics and the Global Wind Oscillation kept away from the La Nina attractor phases 1,2 and 3. The GWO is this week edging through the opposite spectrum of the El Nino attractor phases - so no atmospheric co-operation at all to follow the cooling Pacific ENSO profile The GWO in the high(er) angular momentum phases is therefore good argument to support further warm/very warm weather to return - with any less settled & cooler conditions trying to edge down from the NW leading back to further rinse and repeat ridging as suggested in the previous post last week
  2. Following very similar April's in both 2007 and 2020 in terms of degree of anomalous warmth and the distribution across Western/Central Europe of that warmth - the script heading towards early summer 2020 is proving quite different to the former. There is no sign, at this stage, of a strong e/QBO stratospheric lead on the Northern hemisphere pattern - leading ultimately towards an unstable polar pressure field and mid latitude troughs across Europe. Such a development coming about through a collapse in global atmospheric angular momentum and enabling coupling of that to the cooling trend within the Pacific and a rapidly strengthening La Nina. Such as happened in late Spring/early Summer 2007. At least not yet. Despite the cooling within regions of the ENSO zones of Pacific , more importantly the tropics as a whole continue to reflect above average heat content across the I/O, the Maritime Continent, the Western Pacific and also the Equatorial Atlantic. A strong convectively coupled kelvin wave (CCKW) is at present passing the I/O and generating powerful westerly wind bursts in association with the deep thunderstorm development created by atmospheric engagement with such a large oceanic heat and moisture environment. These westerly wind bursts tend to forge and migrate rossby waves poleward to the extra tropics with time and reinforce on-going amplification of sub tropical ridge development at mid latitudes - in the absence of any unstable -AO forcing on the polar field. The WWB'S are depicted by the strong red/flame colours on the wind-anomaly Hovmollers plot. A swathe of countervailing easterly winds (in blue) at present lie ahead of the CCKW and indicate stable tropical convective suppression. NB: GFS forecasts tend to have a -ve bias to trade wind forecasts These types of vigorous intra-seasonal kelvin wave tropical convection events are often progressive with eastward propagation and the negotiating of trade wind suppression barriers ahead of them and their associated wind shear. Deterministic MJO modelling tends to unreliably depict eastward propagation beyond about 5 days, with the terrain of the Maritime continent region adding to this difficulty with propagation forecasting - but nonetheless, they are starting to track the event eastward right across the tropics. The result of this tropical forcing is to sustain angular momentum budgets within the global atmospheric circulation. Global AAM levels remain on the whole rather above average - depicting an atypical warm/neutral aspect to any attempted Nina-esque ocean lead in the Pacific..... …..precisely what is required to prevent/delay any collapse towards -ve inertia within the atmosphere and force La Nina switch, drive unstable e/QBO stratospheric influence within the polar field, and a much cooler/wetter tropospheric pattern change at mid latitudes heading into summer. With tropical>extra tropical developments in mind as described, CFS AAM forecasts have been persistently correcting forecasts upwards in the medium to longer term - and now reflect a sustained momentum budget through to end of May. Trends thereafter are advisedly treated with caution and subject to change - but no signal for collapse evident. The tropical activity stateside and its expected track and phasing with the macro scale Atlantic pattern over the coming week is creating uncertainty to modelling in terms of the medium term impacts to sensible weather and surface details for the end of the week and the weekend for NW'ern peripheral parts of Europe such as the UK. But overall, based on the Atlantic trough and downstream ridge arrangement dominating the European sector of the hemisphere, it should be viewed as a helpful aid to perpetuating a virtuous early summer season pattern of trough to the west and ridge to our east (and an ongoing SST arrangement across the mid Atlantic that helps perpetuate the pattern). As long as angular momentum trends remain stable, and no sustained fall is induced through the mechanisms described, then this trough/ridge pattern bodes very well for cyclical northward propagation of building heat into the first part of the summer. Therefore, whilst the UK will tend to inevitably see breakdowns arriving from the west in a default pattern such as this, any suggested breakdown that the modelling overall is showing to follow the present warming trend and fine weather, should be viewed not as one individual fine increasingly warm event with an ending to follow late week - but within a rinse and repeat perspective
  3. An extract taken from a post last week, as means for continuity analysis Much of the discussion in that wider post detailed the "pull and push" effects on the synoptic pattern of the decelerating and accelerating wind-flow inertias, respectively, within the atmospheric circulation. With the comparisons of that last post in mind, and following the downturn of a week back that led to the latest cool and wet weather conditions - we are now in the new uptick phase in momentum and the re-setting of the downstream ridge and Atlantic trough over the coming days - a very close match to what was seen in the first week of April and to what was hinted at may evolve in the first week of May in the previous post. One key difference this time is, as observed already by others in this thread, the final warming of the stratosphere has occurred and this will play a part in determining how the mid latitudes and and polar field interact over the coming month - much less of a factor obviously during April. I think its important to put this in perspective however - it is not inevitable that any tropospheric blocking response at higher latitude extrapolates outwards for weeks and weeks on end, and somehow is an omen for the rest of spring and then summer as a whole. Clearly, with that said - various factors come into play here and it is true that these factors do have to be watched over coming weeks - more on that later. The Global Wind Oscillation, which is a phase plot depiction of wind -flow inertia and its effects on angular momentum tendency within the atmosphere, show a lovely symmetry with the previous tropical and extra tropical cycle in April. The GWO has orbited through the falling momentum phases 8/0, much as it did in late March, and is progressing into increasing tendency Phase 4 - the signal, synoptically, for the start of re-set back to the downstream anticyclonic pattern. At least for a time. This GWO symmetry was discussed previously and it was anticipated that the present cool and unsettled spell would respond once the ENSO "mini cycle" embarked on its next eastward cycle and started adding some westerly inertia back into the atmospheric circulation. Such westerly inertia now creating the latest increase back in angular momentum tendency. In the short term, this uptick in momentum re-sets a more +NAO profile in the Atlantic and adjusts ridging back to our nearby mid latitudes - this ensures that much of next week looks quite pleasant once more, and though no heatwave looks likely, it will feel very nice by day with more sunshine to enjoy once more. That is, once the trough to the SW edges away early in the week. Thereafter NWP is advertising the next fall back in momentum in tandem with the tropospheric effects of that final warming - the falling momentum augmenting the more -AO/-NAO profile returning suggested around the days 8 to 10 period and beyond for a time. As alluded to above, some caution is best interpreted with this signal and wise not to over extrapolate its duration and extent this far out in time - suffice to say a further cool and unsettled phase may well follow which would take the time out to the mid month period. Long term some of the uncertainties remain surrounding speed of continued downwelling of e/QBO regime - still a very weak signal to recently, and also how quickly the ocean/atmosphere relationship might lean towards a growing La Nina signal. There is evidence for the latter from various proxy data (not included in this post to prevent it becoming too long). Both of these signals taken together (at face value) are often not the best of portends for a very good summer at this latitude. This does not though, via late Spring and early summer at least, preclude the chances of further warm settled weather to come
  4. Hi all - the lovely sun with its Vitamin D goodness, shining down from clear blue skies onto quiet streets has been a surreal yet comforting sight during a very difficult time. I am sure many will be hoping to see plenty more sunshine make things a little more bearable in weeks to come. This, above, is a very good observation from @Singularity which I wholly agree with and one I have made previously in past summaries. To take this theme even further: Its interesting to choreograph the weather patterns over the past month with the ocean>atmospheric angular momentum wind-flow pattern. Taking a look at the last week of March to the coming last week of April period, there is a discernible correlation to be made:. AAM cycle : Wind-flow pattern inertia related to tropical MJO forcing: It can be seen that the two falling momentum phases, the first one in late March and the second one upcoming in this last week of April, choregraph nicely with the tropical "mini ENSO cycle" periods where increased trade winds (blue) produced a deceleration in global momentum and where westerly wind bursts (red) during the first half of April quickly scrubbed out that easterly trade wind inertia and momentum strongly recovered. Now, to follow, we are seeing a reprise of the falling momentum sequence as seen four weeks back. The effect of reducing momentum is to have a retrogressive "pull" on the hemispheric synoptic pattern. This means, related to our own part of the NH, that the mid latitude downstream trough/ridge response that @Singularitymentions under more buoyant momentum phasing starts to retrogress back to the Atlantic and allows a drop in pressure in its wake and cooler northerly influences developing on the eastern flank of the ridging. We can put this process into practice by taking a look at the synoptic sequence that started the 30 day period. Preliminary of momentum fall 22 March: Pressure high close to UK with Azores/Atlantic ridge strengthening Falling momentum: 27 March: Atlantic ridge becoming more dominant as pattern amplifies upstream due to deceleration of zonal winds (blue anomaly in top plot ) across the Pacific 28 March: Retrogression of ridge complete Now take a look at how the rise in AAM subsequent to this low point in momentum during early April re-instated the eastward displaced ridge and troughing replacing retrogressed ridge across the Atlantic flipping the pattern back around to warm southerly/south easterly flow. See how this correlates with the westerly wind burst (shaded red circled red) on the Pacific wind-flow anomaly chart at the top of the post for the same time - and which creates an upstream Pacific jet extension and provides downstream "push" momentum to the longwave pattern With all this in mind, we can take a look at the tropical cycle for the past 30 days. Viewing the late March progression of the tropical cycle shows the MJO moving through the Indian Ocean towards the Maritimes (shaded green) This represents the suppressed (lower momentum) part of the tropical cycle in the Pacific Similar to what is about to happen at this stage of April. Notice also the eastward progression of the MJO right through the Pacific that coincided with the subsequent rapid recovery of momentum earlier in April (shaded light blue in above plot) Moving forward through April to this particular point in time we can see the suppression phase of tropical convection across the Pacific as shaded deep red/white in the following velocity potential anomalies. This correlates to the latest forecasted increased trade winds across the Pacific to the dateline (shaded blue) and re-posted as per the top of the page (minus my scribblings!) Which in turn is represented by steeply falling angular momentum tendency, from the peak in early to mid April. The drop closely mirroring the late March low-point, as per the following plot : So synoptically we repeat a similar sequence to March with this: Leading to this today: Leading to retrogressed pattern and fall of pressure across UK One remaining illustration of the jigsaw pieces is how the Global Wind Oscillation has interpreted this fascinating previous 30 days. Notice how the large swings in angular momentum, as depicted on the pull and push on the synoptic pattern in this time are depicted by the strong transitional orbits between high amplitude Phase 8 (rapidly falling momentum shaded blue) to high amplitude Phase 4 (rapidly rising momentum shaded red) on through the Nino attractor phases 5,6,7 (high momentum) and now back to Phase 8 and momentum rapidly falling back once again as it did late March Its worth adding to all this analysis that the late March cooler retrogressive spell coincided in a preliminary drop in zonal winds across the polar field c/o initial weakening of the 19/20 seasonal polar vortex prior to brief uptick once more during the first half of April. The upcoming cooler and less settled period from the start of next week coincides with a final splitting and demise of the remaining vortex that ends its long and formidable season of influence. Looking to the late Spring and towards early Summer, much is going to hinge on how the tropical>extra tropical handles a potential switch to La Nina conditions later in the year. In this respect it depends whether a further westerly wind burst can occur during May to return fine conditions once more as tied into the tropical cycle heading back to the Pacific and rallying angular momentum as happened in the early to mid part of this month. Wavelength changes tied into the approach of summer are going to accentuate trend patterns either way (rising or falling momentum) so as often is the case at bridging periods of the year (much as November prior to winter) something of a crossroads is likely during the coming 3 to 5 weeks. Another uncertain factor is the QBO transition to easterly. This process has been rather stalled since January and the evolution of this in coming weeks will play a part in how the weather patterns play out. Unlike last late Spring, it seems that absence of an abrupt final warming of the stratosphere, *should* an eQBO progression be further delayed, aid any further recovery of momentum during the first half of May into producing another fine spell. If that happens. In that respect the AAM forecasts from the CFS and GFS provide signals for that rally. The latter model profile looking rather out of synch with actual proxy data however. Should eQBO progression resume, this increases likelihood of a more sustained fall in momentum, and without the recovery seen in April, then the models are likely to latch onto a more supressed jet stream remaining with pressure staying higher across the NE Atlantic and lower pressure displaced between the UK and Scandinavia. This particularly for approach into summer if the CFS AAM trend to default longer periods of increased trade winds verifies in the immediate approach to summer. There are no definite answers to these questions at this time - the analysis simply points out factors to look out for. On top of uncertain e/QBO progression timing, NWP volatility is likely to persist as a result of a combination of likely still ongoing volatile GSDM momentum patterns (as described in this post and earlier by @Singularity ) and also the issue of possible (?) data glitches related to the ongoing global crisis (non weather related).
  5. I have started skim reading the Coronavirus thread and reading factual/information based posts rather than reading each post. It is of course extremely worrying for all of us and I have had plenty of my own bad patches like most. But too many posts are apocalyptic in nature and the need for some self preservation is urgent. Some keep dwelling on death and trying to equate personal risk to it. While the fear is quite understandable, this simply feeds not just personal very disturbingly unpleasant feelings but also massively enhances them in others who read the horror outcomes based on them - and so it becomes a vicious circle of worsening panic and despair. When the process is repeated over days and sustained into weeks it becomes ever more damaging and unhelpful. This is where some self discipline is required. There is still a lot not known about this virus, but whilst uncertainty feeds fear - lack of knowledge needn't necessarily be all a bad thing . While the mild cases slipping under the radar are also feeding the supply line of cases because they are unrecorded and indeed often enough a-symptomatic and 'invisible', it makes it equally true that the ratio of all cases to fatalities is very much less than appears than at face value. I do think that as time moves on, and as cases keep rising, a much more rational perspective will be found about this virus. At the same time as much more is learned about the virus, including steps to eventual clinical protection. Of course in the meantime we are deeply concerned about potential effects to ourselves and those around us, based on the relative unknowns of the virus and that presently there is no vaccine to prevent it. However, there are still many different ways to try to self preserve : Reduce exposure to social media and indeed step back from this thread if you are spending large amounts of time each day on it. The consequences at their most extreme can be exactly the scenario so many fear with Coronavirus itself - as this tragic tweet confirms Focus on evidenced facts and information rather than headline drama - then give it all a break and get on with the day in the safest way you can. The news channels on television are also guilty of increasing anxiety with their style of reporting. So switch the telly to a different channel as much as re-focus any internet attention. Help others as a way of helping yourself. It could be in the supermarket, on your local street, wherever and whenever. Especially the most frail and vulnerable obviously. Share anything you are lucky enough to have of your own with them. It feels good to do this at any normal time of course, but it is the best antidote during this crisis to the selfish heartless minority who look to seek to profit at the expense of those least able to look after themselves. Have a 'de-clutter' and put together a collection for shelter establishments for homeless on the street - one highly vulnerable group at any time ( irrespective of Coronavirus) but who risk being among the least considered in this crisis. Take deep breaths of fresh air - outdoors, if you can and away from crowds of people, filling the lungs and get oxygen into them and into the body. Keep repeating this process as often as you can each and every day.. If the sun is out, spend some time in it and do something you enjoy, whatever it might be. Or just simply look at the sky, trees and birds etc. I spent time doing these things yesterday in the garden, while doing some tidying up a bit after all the wet and windy weather there has been for so long - and it helped me a lot. It helps with the stress at the same time as priming oxygen into the blood to the organs of the body. Eat good fresh food - enjoy some wine with it. Get plenty of restful sleep if possible - even though this can be difficult with all that is happening. All the more reason to take distractions - otherwise mental exhaustion will prove the least desirable preparation for navigation through this virus. This is obviously not going to go away anywhere near as fast as we would all like, but as much as it seems it is just getting worse and worse, it will eventually leave us alone
  6. I have tried to adopt a positive attitude to the government approach in this country to Coronavirus, and do understand the stated rationale behind it, at least to a point anyway. I think I said as much the other day in a previous post. But things are moving on way too fast and out of control than one might have been trying, at least, to envisage and this post is very, very different in its overall tone and expression of concern Based on the past form of the very selective approaches of this government according to whichever policy it pigeon-holes as idealistic or realistic, its not without reason to support the view that a more pro-active approach should now be implemented that ensures that the disciplines apparently entrusted on the public to self isolate appropriately etc, as outlined by the government yesterday, are followed through in reality to give more confidence and much needed reassurance that this not just part of a behavioural ideology test. I very much sympathise with the concerns and palpable anxiety expressed from some on this thread that there is a feeling of being part of some kind of 'tough love' experiment in terms of sacrificing numbers of our own to the impact risks of the virus - so as to allegedly claim a future immunological gain in the future and which, in relative terms, is supposed to ease extremely intense pressure on the NHS and gives the most vulnerable better chance of more concentrated protection. Like I say, the rationale is understandable to a point - but the very possible range of realities and dangerous risks is quite another matter It adds weight to those in this thread who are criticised for calling out the government for not doing enough, when too much is being perceived to be weighted on an ideological basis that feels like a socio-medical experiment trial. Trials should be expedited through pushing the vital progress being made with anti viral medicines and vaccines - not by playing roulette with public welfare and lives, The continuing uncertainties, relating to a new virus at large across the globe that has no preventative safety valve against it, and based on some of the very distressing precedents being set in the leading affecting countries it has taken such toll on, merit full attempts by government and supporting health experts (of all expertise persuasion) to be seen to strike a path that is strict enough in ensuring the virus doesn't run riot, at the same time as their preferred approach of 'short term pain, long term gain'. Its a very hard balance to strike, and an unenviable one, but I do support the view that more could be done to lessen the increasing considerable anxiety over this short term pain policy - and the growing feeling of impending doom that accompanies it, of being sentenced to be some kind of survival of the fittest situation where we all hope to see as many of us as possible 'on the other side'. I found the approach and tone of delivery of yesterdays conference deeply disturbing and unsettling in this particular respect. I always try to be one who keeps perspective and prefers not to overreact where possible - whether its to do with weather patterns or any other subject. However I freely admit that my own personal anxiety levels are now very high, and this spectre of an experimental approach vs so many lack of precedents and unknowns worries me considerably individually and in terms of those close to me, let alone as part of any discussion debate -, and just trusting the methodologies as provided through the interpretation of this government, is no longer enough. More pro-active measures are needed in terms of protection, separation and ensuring limited gatherings of people and if this, by way of formal policy issue, means restricting numbers at public events much more strictly than at present, looking at school provisions and public services much more tightly, being officially scrupulous from the top with visits to care homes and associated places of vulnerability, rather than leaving such homes, hospitals etc to fend for and decide for themselves what is best for them, than so be it. The list of possible suggestions is not exhaustive - so those mentioned are merely examples. There is palpable evidence in the 24 hrs since yesterdays official guidance update, that more and more of the public, increasing numbers of business and sporting institutions are making their own decisions some way beyond that of the government. Frankly this is inevitable as it is sensible and vital - the official data is the tip of the iceberg in terms of the stats. I personally welcome these self initiatives to act independently in respect of safety first . We all do have a responsibility to play our part, irrespective of government advice and implemented steps,.and would further hope this this trend keeps growing and growing in the absence of the government not stepping up more than they are. I do get the idea of not imposing draconian measures too soon for all the reasons given in terms of firing all the bullets in one go, so to speak- but it seems obvious to me that this concept has been and gone in terms of any window of opportunity - this thing has a momentum of its own that has already outdated yesterdays advice simply even just by the number of well known people from all walks of life who are coming forward as tested positive. I know that the government advisors suggested they are many more than the official figures, but the approach they are adopting vastly underestimates and under anticipates the pace of change and acceleration, and what inevitably les ahead. There are far too many flashing red warning signals - and surely rapid climb-downs must be coming. Much, much better and more reassuring that they were not forced, but anticipated ahead of time The government is acting, or tying to act, to slow/delay a juggernaut that has already passed its point of no return of control of speed. They need to be more pro-active with this - they are not going to earn the trust of the public in terms of self discipline, if rapidly increasing numbers feel as though they are unwilling victims of what could end up as tantamount to a eugenics exercise. For some more perspective , this will not be popular on these pages and I acknowledge the inevitable brickbats that will come - but it has to be said frankly because it is, and will only become, an ever bigger foreboding backdrop to a year that is not yet 3 months old and is falling apart at the seams more than anyone could have conjectured : The government is fully confident, as stated just today, that it can implement a system-level trade deal by the end of this year and tackle the spiralling crisis of this pandemic at the same time -and continues to rule out easing pressure on the transitional period timetable to do things rationally and properly. This is, so it goes, apparently possible when no-one can be sure that any event, however small, will be going ahead tomorrow because of Coronavirus and when no-one, literally no-one, has the remotest clue what effects it might high impact on the country as a whole (as well as across the world) on both a social/welfare and economic level by the summer let alone by December ! I apologise, it might not be de rigueur these days, and it wasn't long back that experts were seen but not heard - but accountability for actions and decisions matters at all times and most of all in national and global crisis. As based on a humanity crisis that began, metaphorically speaking, as the tiniest ripple over the other side of the world on the last day of 2019 ….but has seismically exploded into a globally monstrous tsunami within 3 months. But while life with Coronavirus is a national and global emergency and shroud of desperate uncertainty with rapidly destabilising hysteria bubbling just below it like a high category tornado supercell about to breach the atmospheric cap - it remains 'business as usual' and utter certainly of clarity months and months ahead when it comes to the sacredness of idealist populism. I did say it wouldn't be popular - but it is a valid and wholly credible perspective of the crisis ahead.
  7. Some points and suggestions coming from various angles related to COVID 19 : It is a good idea to keep in mind focus on lung fibrosis - which is a key focal point of attack from this virus once it invades the human cell and propagates through the respiratory tract. Lung fibrosis occurs for a variety of different reasons - and especially with greater age. However, within the context of COVID, it refers to scarring of tissue due to the inflammatory action of the virus on that tissue as it attacks it - and which in turn leads to the symptoms of cough and shortness of breath allied with the rise in temperature as body immunity response to the virus attack. It is obvious that the existing condition of the lungs, prior to attack from the virus, will be a major factor in determining potential extent of damage the virus further imposes on the lungs - and in turn the potential further increased severity of symptoms. Of course other underlying factors, as outlined in the professional health expert guidance come into play from one individual to another - but travel to the lungs, and the effects therein, is clearly a vital process for priority monitoring. A very quick, and basic test of ones own lung condition can be very easily accomplished by anyone of us at any suitable time : Choosing a well ventilated place, and preferably a step outside into the fresh air in isolation of others - take a full deep inhalation of air and fill the lungs as much as possible to capacity. Hold the air there, as tight as can be managed, for a good 10 seconds before exhaling out once more. If its possible to fill the lungs to full capacity, and experience no discomfort or pain in doing so (but most especially without involuntary coughing or spluttering during this time that aborts the exercise), then this is a reasonable provisional indicator that pre-existing fibrosis, from other causes and agents, is not present. There is little doubt in my mind that the potential severity of case reactions pivots around general lung condition at the time of infection (and in tandem with other factors that might undermine personal immunity and weakening organs within the body that especially includes the lungs). A lot of the worst and most alarming cases seen in the worst affected countries centre around this alarming and very distressing oxygen starvation issue - then compounded by not enough ventilation equipment and related resources to support those with least capacity. It is the stealth process of oxygen starvation that in turn impacts the other organs within the body and makes the patient condition even more critical. The resources of national NHS (and other international country major health organisations) is out of our individual control...and much could be said about that as a related subject!. But oxygenating the bloodstream and organs on the larger scale in terms of general moderate exercise is a good free of cost measure to choose to take at any time, and whilst it will not prevent potential infection from COVID, it will at least help assist the body combatting the COVID threat. Drinking of fluids is very important. It is one that I need to keep reminding myself to do more than I do - its too easy to forget to do it and/or or not consciously make time to stop and do it. Flushing the body helps detox the main organs which as discussed can come under pressure during virus attack. Of course this is very much in tandem with the imperative need for hand washing prevention to minimise the risk of ingestion of virus and pathogen in the first place. A balanced diet assists the immune system and blood count - especially one low in refined sugar carbohydrates and 'bad cholesterol' saturated fats. This is much better than relying on supplements (and which will make next to no difference in my opinion in context of COVID). It is additionally a very simple way to lose some unwanted weight over time and 'drop a size or two' - steadily and safely. Also it is a diet that makes it possible to still eat lots of delicious food and one I am very glad I embarked on a while back and to a better degree than I used to ! Next the subject of testing vs case increase. It is wholly inevitable that very sizeable increases in active cases are going to happen in the days and weeks ahead. My own view is that ongoing figures almost certainly cannot realistically account for a very significant number of case infections going under the radar. Neither, rightly or wrongly, can achievable time vs resources make this possible and so it is unrealistic to expect officials and administration, anywhere, to be able to succeed in this respect.. Therefore anticipation and expectation management of all stats updates on COVID is better paced accordingly for mental sanity purposes with all this in mind. On that basis better to not be overly dismayed or overreactive to sudden jumps when they happen, as much as not feel any false sense of security due to any lower than expected individual update(s). Not relevant just for ones own country of nationality but also other countries that are leading the biggest increases at this time. Rather like monitoring the computer models in weather patterns, it makes sense to measure trends over days (and indeed ultimately weeks) than blanket frenzied analysis and then instant reaction and conclusions drawn from each and every update - especially wrt social media tweets which require very careful pruning.... Its going to be a very long process over many weeks to see how this virus play out and we simply have to ride out each day at a time which is going to be difficult., and when reassurances are naturally always a top priority of instinctive human need.. Most everyone is very concerned over the spread of this virus and its impacts, but much better to keep the official advice in mind when looking at these figures and what they themselves expect to see emerge. I am not a fan by any means of this government in terms of its, um shall we say, wider remits and objectives, but there is some reassurance that each conference update on COVID derives very much from the expert medical view of those either side of the PM at these briefings - and a sign that for this serious matter at least for once, expert opinion is being heeded when decisions are made and are based on that advice and not by the much more familiarly witnessed damaging political ideology that result in facts, truth and perspective going right out of the window....
  8. Just a one-off summary before disappearing once more.. I freely admit I have no interest whatsoever in attempting to fit patterns to preferred outcomes, despite my own preferences which much more closely align these days in terms of this thread at the opposite time of the year - so this approach will be in stark contrast to the overwhelming one adopted in this thread and likely disregarded due its later conclusions I have only done a bit of speed reading through most of the posts on this thread, and the majority of them are rooted in my honest opinion within confirmation bias circles anyway. But despite so many claims to the contrary, this is in truth a very typical late autumn low angular momentum driven pattern that features an anomalously amplified wavelength as dictated by a strong NE Pacific ridge leading the downstream configuration of ridge/trough/ridge/trough These low momentum phases in autumn are often punctuated by an intra seasonal higher phase tropical cycle which augments the underlying natural downstream Atlantic ridge profile that the default La Nina type circulation imprints. Forget the actual ENSO base state here - it is the tropical/extra tropical circulation that the atmosphere is adopting to the base state that matters in terms of wind-flow inertia to determine the jet stream behaviour - and it remains likely in my opinion that a Nina type disconnect will persist through at least the first half of the winter So the current intraseasonal phase tropical signal is attempting to pass the Pacific over the coming period and this is providing an added boost to the amplified ridge/trough profile. Much of the seasonal modelling is in excellent agreement with this signature for November, so a continuation of trough disruption likely to continue this side of the Atlantic for a while yet based on the meridional aspect to the wavelength. The CANSIPS, as one of the various majority of models in agreement with the longer term evolution of the pattern is a very close matching example indeed of what is advertized to persist well throughout November As the tropical signal ultimately heads back towards the Indian Ocean following this period, and returns alignment to the default circulation, the period beyond this looks accordingly highly susceptible to a renewed collapse of angular momentum and occurring very conceivably at the same time as the seasonal wavelength change occurs as November progresses closer and into December. Such a renewed drop in momentum implies increased energy returning to the polar jet and re-alignment of sub tropical ridging as trade winds re-dominate the Pacific. With this in mind, and with the the stratospheric vortex uptick to over 40 m/s prior to upcoming temporary (relative) reduction in speed - it means that the November planetary wave poleward momentum providing some perturbing of the tropopause has to be taken into context of longer term angular momentum trends related to the tropical cycle - and also related to the transition of the QBO which is still within its transition phase to easterly. This transition unlikely to complete till late winter. On that basis its hard, at present at least, to see how a disconnect will sustain beyond the tropospheric support available over the coming few weeks and this in my opinion would point in such circumstances to an elevated chance of quite a pattern change during December I am very aware that this suggestion will not be taken seriously, but the context of a chilly November therefore, has (in my opinion anyway) to be treated in sensible perspective and *shouldn't * be extrapolated forward into winter as part of the huge bias preference in this audience. Similar principle to warm late Springs that often are featured as part of low angular momentum wavelength regimes - but, with a few exceptions, more often than not give way in accordance with summer wavelength changes to cooler and more unsettled summer patterns If a warm May was in progress, I would be enjoying it, but still cautious of prospects beyond this time -, so as far as I am concerned the same applies to below average Novembers( for those enjoying that if its your thing) and the portents for winter. And yes, before the usual response(s) appear, I am perfectly aware of all the arctic feedbacks that are chattered endlessly in these threads every year with cast iron guarantee and which always are supposed to lead to the *big one* - but these still require a conducive tropospheric/stratospheric pathway to engage them and in turn provide a sustainable pattern to make it snow... I am not a forecaster, and don't pretend to be able to second guess the weather - but continue to differ from the popular bias view and can see support for the seasonal modelling suggestions of a milder much more south westerly driven type ultimately taking over heading into/or during the early part of the winter. The seasonal models can be wrong, and will surely be wrong again at sometime - but that doesn't mean they are always wrong and especially when it is clear to see from a bias free diagnostic approach that less appealing solutions are indeed also possible than the one most want to fit to suit their preference. Those *other*solutions might entail a NW/SE type of split, with reduced air frost risk and the wettest and windiest weather transferring accordingly away from more southern parts and some hope perhaps for some quieter drier weather here after so much rain this autumn - and at least for the benefit of a very small minority of those who visit this thread, also a much welcomed chance to reduce heating bills at least during the day. With that in mind, the CANSIPS model closely reproduce this prevailing thinking with the seasonal wavelength change showing a much less amplified Pacific/Atlantic ridging regime during December - and a European downstream ridge replacing the disrupted trough. At present at least, most of the other main models have close variations on this same theme Time of course as always will tell. The winter as a whole of course remains anyone's guess Best wishes for the remainder of 2019 and for the start of 2020 . A very few of us will wait as patiently as possible for Spring and the longer days spending more time outside once again..
  9. First I wasn't presenting a seasonal forecast ( just a paraphrased post) and am not a competitive forecaster anyway, and don't subscribe to competitive 'methods' either. If you read the post properly (which you didn't) then you would see that I illustrated this by saying that I don't have the technical where-with-all of the person (person(s) to which I referred. Being honest isn't a weakness and doesn't need to be compensated by tub-thumping statements that proclaim what the 'talk of the weather community is these days'... This is an an internet site for people of all levels and hopefully of managed ego's - , not a platform for parading 'method manifestos'. There is too much of this grandstanding in our outside world as it is... Arctic amplification was mentioned - I referred to it briefly as part of a condensed post and simply didn't write extensively about something that is pertinent to what you want to be the peoples anthem for the coming winter. It is one factor of many, which on its own does not lead to one favoured outcome all the time (as one season to another each year bears out), but involves consideration of multi-variables that might imply more than the one solution than a majority might want to hear. You are free to do this of course, if you want to steer towards a populist outcome - but things don't always work out in reality however convincing they might appear to those who like what they hear. Indeed things don't always work out for anyone when based on attempted objective discussion - the weather makes mugs of all of us. But better to start from a baseline that manages expectation and hopes to learn from mistakes rather than be a tribal lead to populist weather preferences . The price of narcissism does have limits
  10. Just as a very brief addition (before properly retiring to the sidlelines until next Spring) to the previous post made about 5 weeks back which alluded to the escalation of confirmation bias wrt weather preferences which.rises to its highest levels in autumn and winter Its based on a conversation I have had with someone who is a very well respected observer elsewhere, with a level of knowledge and perception that many would aspire to and of a higher technical level for sure than my own. Most importantly they suspend their own natural preferences and make judgements neutrally and based on the merits of all variables present and not selectively. Such observers I think are the ones particularly worth listening to and trying to learn from. Anyway, relevant to the here and now situation but extrapolating that forward in terms of future possibilities - here is some of that conversation based on my own contributions. A few further additions have subsequently been made to make it most relevant to the UK and Europe Yes for my own purposes, a defacto traditional Nina regime looks increasingly likely to persist in the months ahead. The question being where any Pacific convergence may set up to interfere with the regime and create scope for less tropical and extra tropical disconnect to the base state. In that sense the much less disconnected SOI plays a bit part if any westerly wind compartment is isolated, so to speak, due to a wider overriding -ve momentum inertia High amplitude Phase 3 GWO could well be set to return to Phase 1 as trade winds increase across the IO following the recent extra tropical increase in momentum. Once the +EAMT wavelength fades over coming days, -ve FT in the tropics will lead MT momentum trending -ve once more and maintain the GWO well within the Nina attractor phases - providing the steer to persisting sub tropical ridging. This sub tropical ridging is well in evidence in present modelling and amplification of this ridging during autumn and indeed winter to provide short lived colder incursions is quite consistent with many similar years and not at all unusual, or any signal of a harsh winter, This, plus question marks wrt QBO transition needs to be balanced against any weakness within the polar field c/o arctic and other destabilizing factors and why I personally continue to be much more ambivalent and sceptical about the relevance of blocking patterns at this stage of autumn in terms of what it might imply ahead. Just my view of course - and which customarily tries to be detached from mainstream hype that grows each and every year, at this time of year - and when sensible weather preferences and ideals often attempt to fit too many drivers to produce that desired outcome, when probabilities often suggest alternative solutions that are much less popular to the masses. The gist of this extract is that much is yet to become clearer in terms of seasonal overview, but especially stressing that model output commentary during the early stages of the short seasons and making assumptions based on persistence of certain aspects of patterns is fraught with error when attempting to assign specially selected drivers as a means to fit the desired outcome. To all those following progress of the weather patterns in the weeks ahead, try to enjoy progress and evolution - regardless of outcomes vs preferred outcomes
  11. Its been forgotten that the opening week or so of the month was warm both by day and night and the CET was (technically) well above average and the second third of the month has simply corrected that opening warmth to average. With several days of, mostly, very warm conditions to come heading into this last week of the month, it looks highly likely that for all the negativity attached to the wind and rain of late, August will probably finish on the +ve side of the rolling average(s) I think it goes to show that so many dubbed 'poor' summer months nowadays are viewed with quite a different benchmark perspective to, say, 30 to 40/50 yrs back. Heaven knows what some of the 'poorest' summer months would have been described as back then, had the internet and social media existed.... Its interesting, if a little elusively frustrating from a weather observer point of view, that so many consecutive summers have seen either La Nina type forcing dominating or at least a trend as the summer has progressed for some countervailing -ve momentum to appear, and prevent overspill of some the mainland record breaking temperatures to the UK due to an element of Atlantic blocking intervening. NB: -Before there are the inevitable protests from a few, this is a weather related observation and interest, and not personal welfare or infrastructure based However, I think that when there is 'alignment' once again of the atmosphere during the summer, to a greater extent than happened even in last summer 2018, with a sustained El Nino type feedback encouraging extensive and prolonged 1976/2003/2006 type mid latitude ridging, the 40C barrier will be broken with a little maybe to spare. Its seems simply a matter of when, not if. The plot below is a depiction of momentum tendency that includes wave activity flux convergence (beyond just the typical individual torque processes) which is simple terms is a very useful guide to jet stream velocity and trajectory trends This summer managed its new UK summer record...just when atmospheric tendency was at a brief peak in late July...it is not a mere coincidence... This implies just what might be managed with a more sustained momentum/ridge feedback to the atmospheric circulation The crash in momentum at the start of August also doesn't exist by coincidence with the downturn in weather that occurred either soon after. So also applies to the latest uptick relating to the return of the ridging and fine warm weather...and so on and so forth... With all the above in mind in terms of momentum transport phasing - as we approach September, rather than momentum downside, there are signs that beyond the imminent African easterly wave and upturn of tropical activity in the Equatorial Atlantic, there is greater long term upturn potential in +ve AAM momentum transport than existed this month overall. ECM convection velocity potential chart forecasts identify the principle standing wave to occupy the Pacific during September - this reverses the profile that has dominated a vast swathe of August and means that greater westerly wind inertia should be added from the tropics to the extra tropics and lead to further downstream ridge development rather than inevitably the upper trough of the last couple of weeks Albeit tentative, there are also signs that deterministic MJO modelling is starting to identify a higher frequency response migrating eastwards towards the Pacific through the first 10 days of September. At this provisional stage it is not the amplitude that matters, it is the general trend of direction that is relevant. Since the last post, excerpt as quoted above, the numerical models have followed the captioned theme quite closely, with quite the struggle to gauge the parity between an impressively poleward expansive sub tropical ridging regime to mid latitudes vs an equally robust polar jet steering low pressure systems along quite a tight thermal boundary between moist tropical air flowing around the top of this ridging and relatively much cooler air to the north of the zone. Fortunately, sub tropical ridging has become increasingly expansive in modelling, and improved the micro scale prospects as we head into the B/H weekend. With this in mind I don't personally think it is worth getting too hung up about the small feature causing mischief for Monday and let it overtake the bigger picture. Yes, some eastern parts are best favoured for the latter part of the weekend holiday - but taking the weekend as a whole, it remains generally fine and warm with just isolated shower risk (if not very warm and hot for some) The period following the B/H is prone to further numerical modelling faux pas. A slow breakdown attempt of the present lovely weather seems likely and has some shorter term support - however to what extent and for how long? There may well be continued further effort in the coming few days to stall momentum and dig the upper trough further south with an Atlantic ridge present rather than across Europe. However, there will be the ongoing curveball of tropical developments which can just as easily generate warm air advection and ridging ahead of them, than get steered to our shores - and then based on the upstream tropical>extra tropical signals in the new month, any upper trough scenario could well run into trouble without tropical interference in the coming days anyway. Some extended NWP is already playing with the idea of persisting with a greater element of downstream ridging and retaining a more discreet trough further NW. So while the mood occupancy of this and other threads will likely drop interest in warm weather like a stone, and flip into hunting for the first frost and distant three month signals that this winter is going to be 'the one', a minority of others will be away watching with interest for hopes for some extended summer Au revoir for me for this year. @Scorcher If emigration isn't possible, then maybe a warm winter retreat might be a good idea (one can only hope its still possible to escape easily enough!)
  12. Another self quote - just for the purposes of continuing thought relevance to the way ahead. The much recently discussed mercurial set-up in the Pacific, at a time when the first hints of seasonal change are starting to appear within an unstably punch drunk arctic profile - are manifesting themselves through inchoate, and somewhat capricious numerical modelling in terms of energy flow and distribution. Endless repetition of not taking NWP at face value, and not reacting too much into each and every operational output, is admittedly a broken and probably annoying record, but with NWP caution in mind, the ensembles continue to persist, overall, with the idea of anomalous mid latitude ridging, ebbing and flowing, and consistent with the overall volatile mix and duelling of low frequency signal vs intermittent -ve wind anomalies in the EPAC. The danger, and I have seen this in some social media weather pattern commentary, is taking these countervailing wind-flows in isolation and trying to fit individual numerical modelling solutions to them that (appear) to most closely identify - and presenting a rolling 'forecast' forward based on attempted coefficient x+y assumptions about how strong each of the variables present are - when each variable is in reality, the sum of all parts and not compartmentalized in isolation. This is very much an especially blended diagnostic outlook and one where the blended solution in the numerical models is, equally, therefore the most sensible way forward at times like these Overall, with a slight erring to relative angular momentum being fractionally weaker than optimally desired for very best ridging profile for warmth and most settled conditions nationwide - - those percentages support the idea of mid latitude ridging slightly to the west of the UK and with a little more +ve momentum in the polar jet than would be preferred for that greater nationwide settled potential. The sub tropical ridge ebbing and flowing with the westerly upper flow and steering systems downstream close to Iceland The more downside to AAM, then the greater chance of ridging retracting and greater trough disruption. Up to now, this has been perceived as reasonably contained and not sustainable. However, its worth a bit of additional perspective here - Much has been spoken of the low frequency signal and the ally of having an oceanic SST configuration to assist a convergence zone . However, in the light of the persistent -ve zonal wind anomalies in the EPAC, the time is coming where support is increasingly required from the high frequency MJO signal to provide a big additional spike in westerly wind additions to properly combat the EPAC trade winds, ramp up angular momentum on a more substantial level, and in turn prevent the Pacific from more widespread cooling that would diminish the tropical convergence in the Pacific and which would have some ramifications to blend with other intra seasonal factors that evolve, for many weeks ahead (and right through the autumn and possibly beyond). The MJO itself has been quiet for some weeks and this has had some influence in supressing the upside to angular momentum, despite the weak walker cell producing a modest supply of westerly winds in the CPAC to counter balance the EPAC trade winds. As stated in the previous post, the MJO is only a part story to the whole GSDM budget. But it often is, nevertheless, a major catalyst to shaking up the atmospheric circulation and forcing pattern change at the synoptic level. Interest in this intra seasonal cyclical tropical wave phenomenon tends to be restricted to the winter, due to being ( totally erroneously) perceived soley as a magic bullet to deliver cold spells and of no significance or importance at any other time of year.. However, its influences wax and wane all year around and it can have significance for weather patterns equally all year (and not necessarily always to fit human weather preferences) In the here and now, the longer that the high frequency tropical convection signal stays quiet, then the tendency for more sustained falls in angular momentum grows, as easterly wind inertia is allowed to spread from the tropics to wider areas of the extra tropics. This would be reflected in the Global Wind Oscillation incrementally orbiting further towards the La Nina attractor phases - , - and in tandem with seasonal wavelength changes, increase the chances of atlantic ridging taking up residence too far to our west to influence better weather - and inviting a longer lasting trough signal. This doesn't mean automatically mean a La Nina base state would be arriving It simply refers to a somewhat a-typical relationship that the atmospheric circulation would adopt to the (neutral) base state at such a given time (if such a circumstance evolved) Based on intra-seasonal factors (and related to the end of the Indian Monsoon summer cycle) the high frequency signal may well pep up once again over the coming weeks, but hopes of late seasonal warmth and an Indian summer for those like me who would highly welcome it, will more and more rest on this type of eventuality .
  13. Excerpts from last Saturday post as means to try to help link and document progress since that time Since that post, NWP has duly responded by focussing away from any notion of a persisting trough between the UK and Scandinavia, and towards return of ridging next week - as the upstream changes in wind-flow pattern discussed in the previous post(s) create our downstream improvement in conditions, initially most especially further south. As proposed in the quoted post, it remains the case that no instant heat looks likely as the changes get underway, but every sign that by the bank holiday the cooler air left in the wake of the weekends deep trough will have been mixed out with time - and also with warmer air starting to be drawn up from the south as the High migrates close by. Using Atlantic/European views, both ECM and GFS day 10 means are very closely aligned - look set fair for a weekend that hopefully will be some compensation for the two decidedly poor weekends that are preceding it. With the present unsettled pattern in mind, its worth looking at how the GSDM diagnostics represent the changes. On this 2 day lagged data, notice how far down -ve torque tendency ( strong -ve wind-flow anomalies at 20 to 30N) has led to considerable -ve momentum transport in the extra tropics and supressed the present pattern in our downstream location - due to sudden amplification upstream. The Global Wind Oscillation, a key plot phase indicator of extra tropical wind-flows, has responded with a rapid aborting of the Phase 4 +ve tendency orbit late last week to -ve tendency Phase 8 through the weekend and into this week. This type of rapid orbit momentum phasing, is a signal of an unstable GSDM momentum budget within the atmosphere, and often red flags high impact weather events due to the rapid shifts they force on the Jetstream. as the laws of conservation of angular momentum rapidly re-apportion wind-flow inertia to fulfil Mother Natures need to fill a vacuum. Its not a surprise that this spooked the models in their longer term programming - before seeing that the mechanisms responsible for it are set to hit reverse afterwards.... In the very extended period - as for any hint of retrogression (which is 2 weeks away on operational GFS output)….very little point in speculating at that range, much as just recently has been illustrated with the modelled over extrapolation ahead of the UK/Scandinavian trough - and very slow to dissolve it right to the Bank Holiday period itself as analysed above.. For what little it is worth discussing at this time, a late summer/early autumn 2017 full-on La Nina style collapse, in angular momentum (as opposed to this temporary -ve momentum phase) would steer towards a major retrogression outcome. GFS -ve momentum tropical bias would be catalyst for tendency to default to retrogression in lowest resolution (and quite possibly its a trend one or two observers would like to see such as an outcome which is a factor here as well ) The upstream Pacific pattern this August is different to 2017 and with a +ve PDO pattern in evidence that was not there then - but regardless, at this range, and based on the persistence/re-occurrence of the low frequency convergence zone in the Pacific, such sustained relapse, at present at least, is highly questionable in terms of support. Notice the strong suppression signal over the Maritimes (shaded orange) on the velocity potential chart....this is hallmark of return of a standing wave in the Pacific.. …so ensuring the entire Pacific basin is not dominated for the time being by trade winds, as occurred heading into autumn 2017. Instead, classic wind anomaly convergence conducive to deep thunderstorm development,occurring at the dateline with -ve wind anomalies east of the dateline and +ve westerly winds at, and just to the west of the dateline. All c/o the split SST distribution of warmth to the west of the dateline and (relatively) cool to the east. The latter influenced by trade winds upwelling cooler sub water as triggered by intermittent -ve phasing of the South Pacific Oscillation and associated high pressure zone ( cool SST anomalies in South Pacific below the Nino 1.2 ENSO zone). Its important here to differentiate between the low frequency walker cell circulation and the cyclical high frequency MJO cycle. Effects on momentum transport and related angular momentum tendency require key considerations of different proxies.. A reliable assessment of tropical convection and its potential effect on synoptic patterns cannot be made by simply referring to an MJO forecast alone. Extratropical propagation of momentum transport from the tropics has key variables, especially at a time when the Hadley cell is being skewed poleward by the latent heat processes of convection created by additional warming in the tropical oceans. Then, factor in the amplification mechanisms created by the disturbingly low arctic sea ice, and it is no surprise to keep seeing some unprecedented scenarios cropping up within extra tropical hemispheres from one season to another. More than enough to dwell on....At this stage its a case of seeing out the current unsettled spell and seeing in a highly welcome change to more settled conditions through next week
  14. Autumnal synoptics and increased mood music of summers demise, but the premier bullfight is a sneak preview of this years provisional winter message with its traditionally perspicacious advice to 'forget the teleconnections' (aka its going to snow) There will be plenty of time for the building blocks for a redux of that 'beau ideal' of winters, 1739-40, to be weaved and plotted. Just leave the computer models to follow the carefully laid trail of selected drivers, as well as those deselected and inappropriately not fit for purpose, and then simply put on the central heating, put your feet up and wait for the first river to freeze over.... Yay! Job completed. First of all back to the mundanity of the kindled bonfire that MOD thread HQ has tossed summer 2019 onto - without its required 3 week notice Having had help to make the summer gazebo safe today in that wicked 'autumnal' wind, it might require some patience before it can be fully utilized a next time, but it hasn't been fully dismantled and put away. Clear signs now of the ongoing reversal of strong E'rly trade wind momentum close to and east of the dateline from midmonth - and with convective suppression retreating away from the Pacific. This is concordant with return of the low frequency convergence signal in the CPAC. The w/QBO and presence of Nino type walker cell circulation together continuing to regenerate westerly wind bursts in the Western and central Pacific belies the macro scale adjustment through the summer to an ENSO neutral status in the Pacific. As previously alluded to the unassuming neutral status disguises some stark contrasts in SST's across the Pacific which looks set to throw curveballs to modelling now and through into the autumn itself. In the here and now it continues to question the retention of La Nina type downstream flow advertised by NWP in the medium/longer term range. Albeit there is an eventual very slow relinquishing of the trough solution between the UK and Scandinavia. There is no route back to heat that can yet be justified, but any lingering cool air advection looks most likely linked to the transitional relaxation of the upper trough as ridging takes over from the south. This in turn though, an eventual bridge to warmer and settled conditions to return as thicknesses rise and any cooler uppers get mixed out. Prior to the present trade wind burst override, atmospheric angular momentum in recent days has been returning close to average... …...with the extra tropical measure of aggregate wind-flow, the Global Wind Oscillation, reflecting a small increase in momentum flow with a very weak amplitude orbit in Phase 4. This is a two day lagged plot and just ahead of the trade wind burst which will be returning the GWO back to lower momentum phasing while its effects remain. It explains why the current low was not able to secure a more westward track attendant with a stronger downstream ridge response which would have arisen with a higher amplitude and longer lasting GWO Phase 4 orbit. Minor, but significant margins for why the UK narrowly missed a plume yesterday. and instead witnesses an 'autumnal' style deep low... However, based on the subsequent return of the low frequency signal in the CPAC and further westerly winds added back to the atmospheric circulation, there is not really support for a persistent Nina type low angular momentum response long term c/o of a Scandinavian/UK trough and amplified Western Atlantic profile either... The suspicion remains that NWP is being too slow in the extended period to acknowledge the upstream pattern and obfuscation to a ridging transition is overly procrastinated. One word about any MJO/GWO composite inference here. Live proxy data, including wind anomaly, convective velocity potential, OLR data, and polar field profile in relation to the troposphere should always be used to help interpreting synoptic patterns to wind-flow changes across the hemisphere. Much as NWP interpretation, any teleconnection based composite should not be taken at face value without sufficient diagnostic proxy data support. Especially important with so much superimposed heat stress skewing responses within tropics, extra tropics and pole. On the other hand, myopic and parochial dismissal of the role tropical and extra tropical momentum transport processes via torque mechanisms play in altering rossby wavelengths - and hence changing the velocity/ trajectory of the jet stream and providing such a useful advanced insight into how NWP may evolve weather patterns ….is not an act of perspicuity
  15. I agree very much with the premise of this post, and especially its conclusions Signs that the tropical stratosphere is staging a warming ahead of typical seasonal transition. Seasonal warming in the SH implies laying the pathway towards the start of seasonal cooling in the polar stratosphere. The precise increasing differential of temperature between the poles and the associated transport of ozone/assessment c/o Brewer-Dobson circulation to determine the potential strength of the new season vortex still some weeks away of course. However, based on the legacy of a final warming of the stratosphere very late in Spring and into the early summer, that overstayed so many meteorological predictions this summer in terms of its dynamic tropospheric shock waves - then there is going to be increasing pressure to flush out remaining warm anomalies within the troposphere, with the cooler anomalies that have been pent up higher in the stratosphere descending thereafter as the highest levels cool further So in essence I think there is something of a further -ve zonal wind anomaly precursor in the troposphere/stratosphere boundary ahead of a more neutral AO regime(ultimately +ve) under way that makes things 'worse' in the short term wrt summer blocking and supressed Jetstream. Add in the interruption to the weak walker cell low frequency signal circulation in the Pacific at the expense of increased trade winds - -,and in the absence (to date) of any high frequency tropical signal (MJO) to compensate this by helping adding extra supplies of westerly winds to the atmospheric circulation during mid summer, then its easy to see how angular momentum has been trending slightly below average for a while. This -ve wind-flow anomaly assists the upstream pattern becoming increasingly amplified, while this side of the NH at the expense of the higher latitude heights supressing the jet stream in our locale. Much of this has been discussed at length recently. On the other side of the equation however - disparity of SST anomalies shows sharp contrasts in the WPAC and the EPAC. Considerable warmth west of the dateline contrasts with neutral/slightly -ve anomalies east of the dateline Why does any of this matter so far way downstream? This disparity supports the weak walker cell re-emerging sooner or later c/o CPAC tropical convergence and ingredients for convection/deep thunderstorm development - and this translates to questions over the longevity of the amplified upstream pattern as momentum transport increases due to westerly wind bursts returning to the Pacific. At the same time as the AO begins a slow trend towards neutral and also alters the jet stream path To add to the mix, the high frequency tropical signal is starting to show signs of activity following its mid summer slumber . The slumber c/o quite an active Indian Ocean monsoon season. The I/O intra seasonal signal assisting keeping a lid on atmospheric angular momentum and the trend towards the more La Nina-esque pattern that is spoiling Augusts middle third fortunes. There is discrepancy within the deterministic MJO modelling, with the GFS keen on amplified progression to the Pacific whilst the ECM exhibits what can be a problem bias to Maritime convection - but these are quite unreliable beyond 5 days or more anyway. However the velocity potential (VP200) anomalies, a more consistent source of inspection for the purpose, continue to point towards propagation of a more active regime in the Pacific replacing the trade wind suppression of activity from after mid month. Note the movement of suppression across the tropical Atlantic and towards Indo/African Western Hemisphere as this is predicted to occur. . So there is increasing pressure from within the polar field to neutralise heights with time, and for a rally in angular momentum c/o a return to Pacific rossby wavelength control as summer season (not necessarily weather) draws towards its official close. This does not present a clear cut prognosis at all for NWP evolution the further the month progresses. Having spent the last few posts cautioning against taking each NWP suite et ensembles at face value - and especially extrapolating them too far forwards in time, I appreciate the difficulties in the context of this thread of that successfully being heard But from my own point of view, and being naturally sceptical of NWP interpretation of diagnostic drivers, the outlook heading into the last third and especially last week/and end of August period is far from certain. Such scepticism includes the likes of the EC weekly, and its own suggestions of timings (and that of any other long term numerical modelling product). Unsettled and not especially pleasant at all to mid month and shortly after? Yes, alas very much so. But as it stands the upcoming very volatile pattern, further augmented by an astonishing amount of ocean heat north of 30N in tandem with hot continental landmasses to sharply define thermal boundaries, nevertheless risks in its dramatic context, to obscure and risk overdoing a signal that appears to have longer term drivers acting against it. Something eventually gives in my opinion - its a question not of if, but when? That is the most difficult question.
  16. Quoted a further time simply for purposes of continuity and in the face of some advertised less than desirable computer modelled weather through to mid month This sticking trough solution is now, not unexpectedly, coming very much under the radar in the 10 day period - but (for what it is worth) am still very much of the view that it needs to be seen as just another phase of weather, rather than anything sustained very long term. The greater problem in the coming days, than the synoptics themselves, continues to be the risk of taking each individual ensemble data at face value wrt this trough solution and extrapolating it too far forward. More of that shortly. For the near mid to end of week term, the models did not seen the slowing trough solution until the resolution came within the 7/8 day period either. Until fairly recently the ensemble means saw a seamless phasing of the departing mid week trough and the advancing one at the end of the week and a flatter pattern with no warm air advection evident. It is only a transitory downstream reinforcement of warm air advection, and unlikely to much assist those further NW - and does not prevent a continuation of unsettled conditions, and flatter solution beyond this in the medium term,. But it is a reminder of how surface patterns can take on different shapes to the suggested interpretations of pressure anomaly charts at distance. Irrespective of the likely somewhat cooler and remaining unsettled sequence in the following week, it means that temperatures for the next 6 days at least, despite showers and rain about, look set to remain in the average to warm category (warmest further SE). From later next weekend and into the following week comes that suggested cooler incursion as the upstream pattern amplifies in the Western Atlantic with a holding UK/Scandinavian trough downstream. The tropical diagnostic support for this points to blame c/o -ve zonal trade wind increase in the Eastern Pacific as a result of suppressed convection and interruption to the low frequency signal in the central Pacific (that has supported ability of downstream ridges to develop between Atlantic troughs for quite some time this summer).. The increased trade wind burst close to and east of the dateline very evident on Hovmollers (shaded deep blue) and reflected by the strong suppression in the same location(shaded orange) on the VP200 convection anomaly chart The convection anomaly forecast is now just starting to focus on the eastward propagation of this suppression phase and return of dateline active phasing of convection convergence, soon after mid month. Despite a neutral Nino 3 zone, there remains considerable warmth to the west in Nino 4 - and this suggests that central Pacific convergence still remains a valid default signal. In tandem with the return of the low frequency signal, the MJO 'mini ENSO cycle. convection pattern also perhaps re-cycling back to the Pacific for the last third of August and early September period. This would add even further support for a warm end to official summer and leading into September. NWP cannot, this soon, be relied on to 'see past' the suppression phase and associated programmed amplification upstream which holds the downstream trough in place. So simply not worth agitating about the inevitable under par operational and ensemble suites in the coming week and little sense at all in drawing conclusions longer term about them. However, with time as suppression focusses further east in the tropics across the Equatorial Atlantic and Africa, and active convergence of convection returns across the Pacific - then this cuts off the supply of -ve trade zonal wind close to the dateline . The consequent increase in upstream momentum from the Pacific>US as this wind-flow switch occurs should flatten out the upstream pattern and blow a hole in the ridge in the Western Atlantic and across W/Greenland, and as a result greater sub tropical ridging forced downstream instead - so in this way lifting out the downstream trough from SW>NE for the last third of August and retreating it away across NE Europe. On this basis, continued (and increased) supportive reasoning, in my opinion, for an improved scenario with warmer and drier conditions to see out the last official days of the summer
  17. Further self-quoting from the other day, but it has the well meaning intention to reiterate the theme of 'snapshots in time' instead of taking every operational/ensemble/cluster suite at face value, These also extend to the associated upper air pattern representations which also are subject to change as numerical modelling keeps reading the diagnostic elements (comprising fluxing tropical and extra tropical wind-flow phases) over time. Extrapolating all of the numerical modelling representations ahead for unduly long periods of time is fraught with error when margins of change can sometimes emerge over periods of days at a time, rather than every 6/12/24hrs at a time The bolded extracts in the quoted post are simply for particular emphasis. An interruption to the low frequency tropical walker cell signal in the Pacific that has dominated much of July (and that propped up the Atlantic trough/our downstream ridge) has been in progress and is set to persist into the new month with the renewed increase in trade winds over the Pacific clearly evident since the end of last week (shaded blue in and around the dateline) ,...This will be helping propagate -ve AAM anomalies to higher latitudes based on a slump in global atmospheric angular momentum . So essentially this slump is now catching up on us - and as a consequence helps re-invigorate blocking at higher Greenland latitudes and this side of the Northern Hemisphere inviting a path towards a supressed Jetstream and low pressure phasing between the Atlantic and Scandinavia by next week. Therefore a trough close to the NW of the UK has support in this respect. However, temperatures throughout this period look quite respectable and warm at times - especially perhaps this coming weekend before the pattern flattens out (as expected) so nothing in those respects that is poor by summer standards. (Also see the conclusion of this post). Personally, for what it is worth, I'm not attaching confidence in a Scandinavia/UK trough as any long term sustained solution encompassing 'the rest of summer' - and continue to think that the numerical modelling risks over dwelling on this signal. For me anyway, its a case of sitting on hands, and letting the scenario play out. The numerical models are not going to drop it immediately within a day or two, which further envisages in my mind the moans thread busier with standard writing (or repeating) of summer obituaries - but that is where the risk lies in interpreting/making assumptions about longevity. Summer 2012 style, did not materialise following the first two thirds of June 2019 after all....And whilst the last third of summer beckons immediately, there remains plenty of time for summer-like weather So as was the case in June, its also too soon to summon the meteorological priest at this time It remains likely that the pattern will keep retrogressing, as suggested previously, so that ultimately at some stage the jet stream will be forced to lift a trough further NE and invite a further ridge response towards Europe - and irrespective of any trough signal over Scandinavia. This is especially true if tropical activity in the southern Atlantic is created by the actions of a convectively coupled kelvin wave activity passing through Africa from the Atlantic - such a CCKW is occurring during the first half of August. This type of activity often throws curveballs in modelling at short notice during many late summers and as an interruption to mid Atlantic ridging and Scandinavian trough scenarios and cuts short their attendant less than desirable cool changeable north westerly winds, besides which, are often over modelled at distance. Those - that are one of the culprits for summer obituaries There is a lot over the coming 10 days that could,and conceivably will, alter the apparent prognosis for August as a whole,. Whilst an unsettled spell is supported and it may also turn cooler for a while around the second week and towards mid month (pending tropical developments) it makes sense in my opinion to compare ensemble suites and clusters over that opening week to 10 days as an evolutionary way forward, rather than taking each at face value individually, on repeated intra day intervals and drawing conclusions/extrapolating the snapshots in time too far forwards Notwithstanding the above suggestions about not taking individual modelling suites at face value, even if I break my own rules at this early time (as subject to the further evolution as discussed) there is nothing exactly terrible anyway about the latest temperature ensemble set assessed against the implied (and fully expected) flatter pattern phase for the second week August period. Its maybe forgotten just how very much cooler than this the early to mid June period was.
  18. Looking back at a previous post last weekend, and some thinking expressed back then, its clear that the lesser progressive solutions did lead the way in some erratic modelling that was forced into some impressive westward corrections. The closer detail reveals that this weekend is turning out wetter and therefore cooler than could have been anticipated at such a range, and across what is a microcosm of an area in relation to deciphering the Atlantic and European pattern. However, this rather distorts the bigger picture which shows that the very hot airmass has proved every bit as difficult to shift eastwards as these lesser progressive solutions suggested. Indeed it is this same slowness that has resulted in the stalled front and associated rainfall in evidence today and into tomorrow for quite a few of us. The next thing to say, is that very many contributions and updates from a wide range of posters has made this, and other threads, following the modelled progress of the heatwave, an excellent read this week - and so in my opinion a lot of credit and thanks is due to a large number of members for some very detailed discussion and debate Its been an astonishing week - not just for the heat itself, but also ( just for example) the outflow winds from thunderstorms which actually exacerbated that heat on Thursday evening associated with active and prolific 'dry lightning'. These strong outflow winds were picked out by high resolution models - as the EML theta plume (Elevated Mixed Layer) very gradually destabilised set against the very high upper air temperatures that had been 'capping' it - and have been taking so long to displace eastwards Looking ahead, in my opinion a main theme of this summer stands a good chance of repeating itself. The recurring 'spasmodic' blocking of this summer previously discussed c/o a highly unstable polar profile keeps duelling with a very organised low frequency walker cell in the tropics that equally persists in renewing sub tropical ridging to our mid latitude. At the same time according with this, and with our SST signatures helping, an Atlantic pattern fails to sustainably send a procession of lows under any block for a length of time, as one might expect with recurring higher latitude blocks, and instead sees follow up low slow on approach and give the sub tropical high every opportunity to ridge into the void ahead of it. The modelling has shown itself this summer as susceptible to wanting to keep the pattern too flat for too long with the phasing of these lows and instead the sub tropical ridge proves more resilient ahead of it. This is something to watch in the snapshot in time ensemble suites and not take too much at face value from the more immediate suites - but maybe instead judge them from how they evolve during the coming days ahead. Persistence factors alone do not of course guarantee past trends will be mimicked in future trends. Next weeks blocking programmed to the north is likely to migrate westwards with time, in tandem with pressure falling over Scandinavia and also tending to migrate that low pressure west to phase with approaching troughs in the Atlantic . This initially looks set to flatten the pattern to create the illusion of a longer term procession of lows. But as the pattern retrogresses, then this increases the likelihood that a follow up trough will, ultimately, like previously seen this summer, deepen in western/mid Atlantic and so a re-occurring downstream sub tropical ridge response accordingly gains traction, in time, with the modelling. On that basis, the present fall in pressure over Europe (created by a displaced arm of the jetstream digging southwards, elongating the trough that was to the NW of the UK and gravitationally forcing its new centre of low pressure into the continent) represents the conclusion stage of a repeating cycle that commened at the start of summer, progressed its second cycle through July to its present end stage, and over the coming 10 days is looking set to commence its third cycle. The differences between the first two cycles has been that seasonal wavelength changes vs the tropical/extra tropical windflow circulation on the jet stream (the low frequency walker cell and convectively coupled kelvin wave activity in the Pacific) have helped incrementally back the pattern westwards. This trend takes us to the third cycle. So that : 1) In June we saw the trough directly over us, and then immediately following up were still subject to cool air advection influence with the very high uppers that followed. 2) During July we have seen the trough resisted close by to our west. Hence the least progressive solutions verifying and the very warm/hot air advection managing to stick long enough to share the noteworthy conditions that mainland Europe saw in June 3) As August progresses our third tropical/extra tropical cycle of the summer, there is a reasonable chance that we may see a trough sequence further displaced to our west and a more prominent late summer anticyclone influence from Western Europe/Scandinavia. Especially perhaps if some activity in the tropical Atlantic assists in the process. At the moment, the modelling is best 'seeing' the phasing of falling of pressure across Scandinavia (from its latest downstream ridge peak) with the trough(s) approaching in the Atlantic next week. The caution is in extrapolating and making assumptions too far ahead from this - and so not a bad thing to be mindful of the risk of NWP persisting, in error, of this synoptic stage for too long. Too soon to suspect August may follow any alleged underwhelming tradition, even if the ending of July and heading into the new month might appear to be getting off us off to a (relatively) unremarkable start. But temperatures still look respectable over the coming period and perspective has to be set against the spectacular events of last week
  19. A bit of balance might be required, not unusually, for this thread: 1) Starting from round about now, the weather is on a fast track improvement for many and one thing is certain is that it is going to become very warm, and decidedly hot for some. Excepting of course those furthest north west who are ones to maybe have some justification for feeling a little left out and have reason to moan. 2) Whilst the odds on an extended heatwave scenario continuing from late this coming week have clearly reduced over the last 24 hrs, the latter part of this week nevertheless remains an NWP minefield - and there is not yet consensus on precisely how things are going to pan out. 3)The 'worst case' scenarios still look to manage low to mid 20s for many next weekend even when the greatest heat is 'swept away' These sort of temps have graced much of the month so far, again for quite a few (if not always all) and are a far cry from the dismal first two to three weeks of June. 4) The latest ECM operational is a least progressive and one of the warmest favoured solutions, but it is not far fetched in its evolution (as I commented with this type of scenario the other evening) and even its ensembles still suggest (currently) something very warm persisting into the following week - with the uppers remaining above 10 right throughout next weekend for many central and eastern parts. Yes these temperature numbers are for London, in the most favoured SE region, but they illustrate some perspective of how much the 'cool down' might be 'Normal service' ie low 20s is not suggested until well into the following week on these - though as a snapshot in time they are of course subject to change....either way.. 5) Its worth bearing in mind that the FV-3 ensembles have performed a spectacular volte face in 18 to 24 hrs and moved the heat zone more than several hundred miles in that time later next week. So whilst caution is required with any snapshot in time NWP ensemble suite, it certainly applies also to the FV-3 here. Starting with that secondary low from midweek... This caution equally applies to the other modelling, including the UKMO at day 6. 6) The diagnostic approach, which I favour, cannot help further with a scenario like this because the full range of micro scale numerical solutions on offer for the UK all fit within the macro scale range of the diagnostic at what is a relatively short distance for such non numerical evaluation. Just a 100 to 200 miles lee-way, either way in this sort of situation, could make some very big differences when trying to dissect the fortunes of a tiny island at a crossroads to a huge wind-swept ocean one side, and a hot and humid landmass the other. 7) With that in mind, maybe a good idea to enjoy the coming days (if like me who are a big fan of this type of weather), rather than already be thinking its over before its barely begun. And especially when specifics later this week still are not wholly certain. Living in the moment doesn't come easy with weather pattern watching, and especially for quite a few on this thread - but weather enthusiasm is also about life itself and appreciating the here and now, when so much worse can happen in the real world than how long a heatwave lasts. Again, in weather terms, those furthest north and west will not gain much consolation in that - but for the UK there are always winners and losers as it is rare to have a whole island witnessing the same conditions at any given time with our maritime climate.
  20. The ECM 12z operational might be an outlier of this evening, and indeed may prove by next week to have been just that - but it fully exemplifies (to the greatest extreme maximum!) the scenario I outlined yesterday, and which is also present in sections of the FV-3 GFS suite as well. NWP model suites are simply snapshots in time, and each one develops the themes of the previous suite according to the diagnostic probabilities. So its quite conceivable for even upper air patterns to diverge from one suite to another when an essential part of the jigsaw in terms of the upstream pattern shows a large spread degree of uncertainty. And from memory someone posted a substantial degree of spread of the eastern Atlantic yesterday which illustrated the conundrum of how energy is split with the trough responsible for ushering in the initial (very) warm air advection from the start of next week. Climatology favours the more progressive solution, and it could be that the expected two/three day plume = fresher air to follow does indeed verify, but I wouldn't personally be astonished to see a curveball. This based on the diagnostic probabilities that suggest and support some deceleration of the jetstream across the Atlantic round about the pivotal time that heat advection is pushing north through the UK. This interfering with the distribution of energy in the eastern Atlantic at the key period - and which leads onto that Atlantic ridge late next week to fill the void left by the slowing pattern to complicate things further and help stall the eastward shunt script. And which is clearly modelled on the ECM 12z as well The ECM 12z might turn out to be some viewing entertainment in the fulness of time, but as a few have already hinted at, there is nothing about its modelling within the day 4 to 6 period which is not credible - even if the chances of such sustained intense heat as it shows are likely (relatively) moderated. Or maybe not as the case might be...
  21. This is a good question - I agree with the response that @Singularity has made earlier. For those who dislike very extended wider discussion detail, this post eventually 'gets there' in terms of its relevance to the here and now model discussion context - but there are benefits from a bit of analysis in terms of the increasing difficulties of 'pattern matching' and why it is increasingly fraught with potential error if too many x+y= assumptions are made about composite analysis synoptic responses. This in turn affects those who attempt forecasts, short and longer range, using diagnostic vs traditional NWP methods. I'm highly grateful that I merely offer observances and reflections such as these in posts, than attempt (or want to be involved in) any competitive forecasting element itself Caution is required when referring too literally to composite analysis of the tropics (MJO) and extra tropics (GWO) when trying to decipher synoptic NWP responses, as ocean/atmosphere and polar/troposphere disconnects and a-typical synoptic responses become increasingly common - no doubt at all ever more skewed by the modern climate context.. That doesn't mean in any way that the GSDM is invalid - quite the opposite and far from it. Simply that the vital wind-flow (jet stream) diagnostic offered, requires to have the minds that utilise them, (and are open minded enough to acknowledge them) adapted to full acceptance and lack of denial of the changes that are happening out of human control (it would seem!) and which the science has harder and harder challenges to keep up with While the arctic sea ice stresses and subsequent amplification feedbacks are obviously well known enough on sites likes these, and as one major element of this macro scale step change shift, there are also feedback stresses within the tropics where superimposed, additional anomalous heat in all the tropical oceans, above the norms, is also creating ever more skewed ocean/atmospheric responses. A very good example of unusually strong disconnect was the strong El Nino event of 2015/16 which managed to manifest starkly a-typical -ve forcing aspects due to the unusually high SST's that persisted in the I/O at the same time as the very warm ENSO event was present in the Equatorial Pacific. This anomalous extra superimposed ocean heat across all the ocean seas in the tropics is very much a factor of the regime shifts being seen and which have accelerated ocean/atmosphere feedback distortion further this decade. This blog entry, at the time of that event, remains a very good discussion pertinent to the post question under discussion https://blog.weatherops.com/global-warming-and-enso-a-helter-skelter-atmosphere Also, very much part of the jigsaw connected to the increase in Nina-esque disconnects to Nino phases, we have being seeing persistent feedbacks since last year from relatively cooler southern ocean waters, as mentioned in the post the other day, that create a -ve SPO (South Pacific Oscillation) and hence a quasi -permanent sub tropical high pressure propagating zone which acts 'destructively' on warm ENSO events. This means more prevalent trade wind phases than might be expected during an El Nino are restricting relative angular momentum tendency to lower levels than might be expected with a traditional event. More on this further down wrt frictional torque mechanisms. The atmospheric divergence created by greater, overall, trade winds, creates wind shear that is hostile to eastward propagating tropical convection, and this stabilising suppression of the atmosphere transfers into stronger sub tropical ridges which, according to seasonal wavelength changes, periodically push northwards towards mid latitude. Hence prominence of poleward amplified anticyclones in both Pacific and Atlantic during any -ve (Nina-esque) forcing. This particular link refers to the analysis and effects of -ve SPO regime. https://www.climate.gov/news-features/blogs/enso/look-south-enso-forecasters The inference in GSDM terms is that negative SPO feedbacks create negative tendency of frictional torque in the tropics. In the here and now, notice the persistent trend of -ve FT within the sub tropics below 30N as indicated by the -ve (easterly trade anomalies). The largest anomalies, circled that are in blue, naturally coincide with the greatest departures in frictional surface torque. It is these -ve easterly wind anomalies and associated -ve torque mechanisms that underpin the sub tropical anticyclones and create compensating westerly polar jet momentum at mid latitudes on their poleward flank, according to the laws of conservation of angular momentum, and so impacts on jet and pressure profiles downstream across the US and in the Atlantic Stronger trade wind bursts, as well as reducing the eastward propagating effects of convective convergence in the western and central Pacific, assist upwelling of cooler sub surface waters in the EPAC, In terms of my own 'at home' observation as a fascinated pattern watch observer, there is no doubt in my mind that these sub tropical ridging patterns, whilst always a feature of greater trade wind phases, and typically subject to seasonal wavelength changes and Annular Mode variations, are becoming more and more dominant as part of shifts in long term global changes. With the tropics forcing one way, due to anomalous extra heating, set against the destabilised polar profile creating larger swings in AO responses as the sea ice patterns distort feedbacks there, a new way of interpreting composite analyses for H500 patterns is certainly required. Innovation in forecasting science is great, adaptability to undeniable forcing change on the weather patterns, and the benefits that follow of greater further understanding is even better. All the more reason, in my opinion, to pay greater attention and scrutiny to what are dubbed on this thread the 'background signals' because they present greater and greater challenges to deciphering NWP, as they equally test the performance standards of NWP modelling itself Which brings us back once more to the here and now and that mercurial mix of low frequency tropical forcing in the Pacific vs the South Pacific Meridional Mode - both acting against each other. A twin low frequency signal acually persists over both Africa and the Pacific. This presents a disconnect element when the African wave predominates over the Pacific wave, and its associated equatorial easterly wind anomalies propagate across the Equatorial Atlantic and create wind shear in the EPAC which suppresses convection. This stable suppression helps poleward promotion of that South Pacific ridge and in turn downstream strengthening of the Azores sub tropical ridge in our sector. However, the presence of another standing wave due west to the dateline and separate low frequency signal in this region creates resultant tropical convection convergence zone where the African equatorial easterlies meet the Pacific low frequency westerlies. It is this convergence that prevents a more full blown Nina-like response in the Pacific - and which equally therefore prevents the Azores ridge retracting, with added polar jet flow over the top of the ridge depositing a downstream trough in our vicinity for any sustained period of time With such countervailing factors evident, not unreasonable to expect a combination of upstream pattern that presents a neutral enough PDO regime to enable downstream split energy of the jet stream that allows downstream ridging to occur as troughs deconstruct, but also at the same time persists with a recurring strength of sub tropical ridging in both the Pacific and Atlantic (Azores ridge) due to the equal presence of the African wave supporting the sub tropical ridges. Final outcome probabilities, in synoptic terms, allows the type of scenarios where cut-off lows result as trough deconstruction occurs, and in the wake of this deconstruction, the sub tropical ridge upstream re-asserts a renewed eastward ridge from within the Equatorial Atlantic to reinforce the existing downstream ridge, trapping that cut-off low beneath the ridging, and potentially sustaining heat ridging in place for longer. With meandering and sluggish jet patterns, choreographed through a mix of highly unstable tropical and polar forcing, which in turn create destabilised and often disconnected GSDM profiles, heat trapping scenarios are bound to become more regular summer time features it would seem, to me at least as much as implications of various kinds can be drawn for the opposite times of year.. The UK's fate, in terms of tapping into continental increases in heat, rests as usual in the actual wavelength that the sub tropical ridge amplifies. All tied into that primary wavelength dictated by frictional torque tendency within the Pacific, as just discussed according to the controlling tropical wave(s). But also the polar profile determining the latitude the ridging sets up. Late June, with greater downwelling of -ve zonal wind anomalies from the final warming legacy also a main factor than is the case now, was a myriad of Nina-like sub tropical ridging in the North East Atlantic, set against the struggling Nino low frequency standing wave in the Pacific, with the result that cooler air advection was able to come around the retracted stronger sub tropical ridge in the Atlantic ( the weaker less dominant sibling ridging extension over Europe could not prevent this) and off-set the furnace level upper and lower temperatures from mainland Europe manifesting themselves at ground level here in the UK beyond a day as the dominant Atlantic ridging briefly weakened This time around, the downstream pattern is allowing trough progression to be able to force greater sub tropical amplification of ridging ahead of it - instead of what occurred in late June when the wavelength favoured earlier retrogressive amplification. My own interpretation from the 12z thus far is quite consistent in inclining towards the ECM ensemble consensus this morning. The consolidating downstream European ridging is also a good sign of +ve poleward momentum transport taking place - and which according with the increased maturity of the +QBO phase, also suggests intuitively that a more +AO and +NAO regime may be forthcoming for this second half of summer.
  22. If I might interject here The lack of MJO forcing in the Pacific, with emphasis of activity sticking in the I/O, is being dampened/offset by the low frequency signal which remains firmly in the Pacific- and a reminder to us all that the MJO is not always the be all and end all when it comes to pattern change dictation from the tropics. Its early days, but there are some similarities developing with the latter part of the summer in 2016 developing. That is not to say it is going to pan out exactly the same as the second part of that summer, but a Pacific low frequency wave train is present at this time as it was then. These persisting westerlies showing up orange shaded close to the dateline here: The latter part of summer 2016 and indeed well into September produced a re-cycling pattern of plumes interplaying with eastward displacing Atlantic and Azores ridging that alternated cooler more unsettled phases with these warmer plumes. The prominence of the low frequency signal is echoed by the SOI (Southern Oscillation Index) which ironically is more -ve now than at any time this year that an Nino SST signature has been present in the Pacific (SST's overall now trended neutral - warmest to the west, coolest to the east) So despite the fact that angular momentum has slipped to levels not seen for over a year c/o loss of westerly momentum in the extra tropical circulation (and is also at a similar level to late summer 2016), the weak walker cell circulation and associated convective convergence zone is still enabling something of a downstream synoptic response that is more reminiscent of El Nino than the extra tropical wind-flow Global Wind Oscillation might suggest. Hence the ability for some a-typical sub tropical ridging downstream, as a reprieve from occurring too far upstream and allowing a UK trough dominating instead as one might expect from a lower AAM extra tropical response. Its still only mid July, and clearly still rather early to say for sure, but this tropical forcing disconnect, if it can prevail/re-cycle may yet produce a better second half of summer, than the increasingly Nina'ish extra tropics implies Much as happened in August/September 2016. As long as the western/central Pacific walker cell circulation keeps producing convergence close to the daleline (as it encounters countervailing trade winds c/o divergent/stable relatively cool waters in the Southern Pacific) then there is no automatic assumption to be made that a more typical Pacific/.Atlantic Nina-esque circulation should take over (such as it did after mid July in 2017 as a good example) and which resulted in a retracted Atlantic ridge with enhanced polar flow and troughs steered close to the UK.
  23. Just wanted to send a 'thank you' to several kind members who have sent lovely supporting messages over the last 10 days. It has been very much appreciated So to keep on topic, I had better add some relevant substance to the post. Its another of those regular occurrences when addressing NWP requires caution - both in terms of shorter term detail around the weekend period and also in the extended period. The areas of relatively greater uncertainty just to the NE in terms of how much the eastward migrating trough digs southwards and the extent to which cool air advection comes south is suggested from the recent spread maps for the start of the weekend The overnight UKMO being representative of an opposite end of the spectrum comparison to the ECM in terms of retaining warmest uppers within the parameters of such a spread In terms of the picture beyond this time, ensemble suites are, as always, simply snapshots in time within an evolving situation and the clusters themselves (e.g that can seen within the ECM) usually identify the solution(s) that the diagnostic points to. Though these too can be prone to change direction like shoals of fish in midstream when contradictory factors are providing different diagnostic solutions. I think to break such an overview down into straightforward terms, then @Singularity has done this very well already today in terms of the diagnostic - and @Man With Beard identifies the post weekend likely route of the pattern equally well as per the NWP solutions that the diagnostic identifies. As long as a convergence zone c/o of westerly winds close to and to the east of the dateline in the Pacific is present, then it is unlikely that any fast breakdown from upstream is likely to occur. Those +ve zonal westerly winds clearly visible on the Hovmollers plot The Southern Oscillation (SOI) remains indicative of a very weak El Nino standing wave, despite the more neutral SST pattern overall across the ENSO zones. This too, an indicator therefore of that convergence zone within the Pacific Furthermore, tropical activity has finally emerged in the EPAC since the trade wind burst during June ended (and which helped wreck UK prospects with all the Atlantic blocking in tandem with late season final warming downwelling from the stratosphere). The greatest -ve VP200 anomalies (velocity potential) dovetail very well with the location of this tropical activity and where ocean>atmosphere feedback is taking place, concurrent with greatest SST anomalies. These plots, borrowed from Mr Ventrice site, are very good illustrations of the activity that is helping direct the upstream pattern. Note also the corresponding convective suppression c/o downstream wind shear across the Equatorial Atlantic. The Atlantic blocking pattern (and which in turn encourages heights to amplify in the Greenland region) is exacerbated by any upstream amplification occurring in the Pacific (setting the downstream configuration of ridges and troughs) - but a weak trade wind pattern within the Pacific as described already (ie lack of -ve zonal easterly winds which therefore allows persisting Pacific tropical activity) will make this hard to achieve sustainably over the coming period. This is correctly acknowledged as such by @Quicksilver Taking into account the upstream forcing as described, then it makes sense that in the medium term at least, there is more likely to be the presence of a trough rather than any sustainable ridge in the Atlantic. That leaves the conundrum of the arctic high pressure pattern. As described this is exacerbated during peak summer wavelengths as a product of the tropical cycle when it enters the Western Hemisphere where an African standing wave co-exists with the Pacific wave - and creates a more 'destructive' element to the Pacific standing wave when the low frequency MJO signal is passing through this part of the tropics. Precisely what happened in the first half of June. I think, for what it is worth, that the trend of the remainder of the summer is for this to become less 'spasmodic' (to coin a phrase from a well respected member not on this site) - but that does rely on how the tropics behave heading towards August to prevent the type of breakdown we have seen in quite a few recent years for the last third of summer. Even the glories of last summer succumbed to this trend - albeit with a more +ve AO/NAO signature retained. There is however no strong signal of this happening just yet - and just one other good reason not to extrapolate anything at all just yet from any 2 week extended ensemble suites that might want to hint at programming extensive Greenland heights and a southerly tracking Jetstream Taking into account the persisting inclination of the long term trend of the NAO to retain a -ve signature... ...whilst uncertain and low confidence, it is still not impossible that rather than any inevitable eastward extension of an eastern Atlantic trough across the UK, an interim ridge next week amongst a mixed overall UK wide pattern might prove more resilient instead with a slower advancing or even stalling trough to the west emerging in that extended term period and create considerable warm air advection ahead of it. Especially if the models continue to correct the strength of heights across the US as they have been doing over the last day or two ( they have been adjusting to the greater suggested +ve zonal wind-flow across the Pacific than they anticipated) This is turn implies relatively lower Atlantic/Greenland pressure and more tendency for downstream ridge manifesting. Anyway, I just wanted to acknowledge good folk. Whatever the weather, enjoy the rest of the summer .
  24. My own summarisation of prospects for this season to date has been concluded, but before that happens, I cannot leave the quoted post remain unanswered as it requires 'outing' for its wholly unacceptable misrepresentation and inaccuracy of reporting. I suggest the poster reads in full the posts to which he is referring and which he clearly has not already done and furthermore should acknowledge that quoting posts, and in their full context, is the respectful and reasonable way of reference rather than this kind of exercise. The diagnostics have pointed persistently to split outcomes this season - as identified some time back in the second half of Spring. There has been more than enough repeated attempted guidance as to how the conundrum of the stratospheric final warming vs the tropical/extra tropical circulation feedbacks on the pattern may run into some major headaches for NWP modelling. Others too have clearly endorsed such views in their own attempts of assisting deciphering these complexities. There is every evidence, as already correctly documented by some in this thread that the intense dynamic blocking responses of the last 6 to 8 weeks are coming to some resolution - and some comparisons were made a couple of weeks back by myself with other years that have shown similar stratospheric/tropospheric downwelling evolution as this year. Amongst them, 1995, 1997, 2009 and 2013. Two of those, 1997 and 2009 also showed very similar low frequency tropical signals to this year. More of that later. But taking them all together, a variety of different synoptic outcomes verified through the course of these summers but I am not going to waste yet further time referring back to any of this. This year, for what it is worth, it has stayed my view as per some weeks back when these seasonal updates began, that once the -AO forcing over the polar field started to respond to summer wavelength changes (and which it is now showing quite clear evidence of doing) that the fate of the summer synoptics would then be more clearly in the hands of the tropical/extra tropical cycle and whether this shows either: A) a continued risk to adopt -ve momentum tendencies c/o of an amplified upstream Pacific pattern and associated persisted trade winds resulting in a retracted Azores High downstream and added polar jet flow keeping cool Atlantic circulation across the UK and a changeable mobile element to the greater part of the isles or B) whether the low frequency standing wave in the Pacific can hold out against any increased trade wind phases and relocation of that standing wave to the Western Hemisphere (that assists scenario A) and help sustain improvement from the less than desirable base line of the start of summer and increase the frequency and duration of downstream summer ridges. As things stand: The present situation with respect to the tropical wave and associated propagating westerly wind bursts which aid downstream ridge amplification is that the velocity potential convection anomaly charts (VP200 anomalies) point to propagation of the tropical signal to the dateline in the Pacific during the last third of June In favour of option A: In association with recent tropical suppression phase in the Pacific (shaded orange above), trade winds increased at the turn of the month and helped exacerbate the recent stratospheric/tropospheric lock in of the resident trough c/o intense Greenland/N Atlantic blocking. Wind anomaly forecasts continue to point to -ve zonal winds persisting to the east of the dateline in the Pacific, and which, potentially, presents some question mark over extent of propagation of the latest tropical wave advancing into the Pacific and currently over the Maritime Continent. Notice the muted response west of the dateline in terms of advancing westerly winds in association with the tropical signal indicated on the convection anomaly plot above. Taken at face value, the net effect of sustained trade winds against the suggested weak propagation of the tropical wave by the ECM would suggest that the tropical wave would beat a retreat towards the dateline (by or probably before MJO Phase 7) and this would be the cue for derailing downstream amplification of any mid latitude ridge and initiating a flatter Atlantic pattern with the Azores high retracted westwards In favour of option B: The GFS model forecast, below, has a clearly significantly stronger westerly wind burst advancing into and across the Pacific than the ECM forecast, even if it does retain the same sort of trade wind sequence in the Eastern Pacific. The ECM is known to exhibit some -ve tendency bias with eastward propagating tropical waves from the Maritimes to the Pacific, so whilst it is not necessarily wrong here, there is no inevitability of Scenario A. Undercooking westerly propagation plays some part in over estimating -ve easterly trade winds in terms of compensation of wind-flow inertia which cannot by nature, exhibit an inequality of vacuum within the atmospheric circulation. There has to be a compensatory wind-flow response for each and every other one that occurs - and according to the laws of the conservation of atmospheric angular momentum. Also, and with that caveat to -ve bas tendency in mind, its worth looking at the ECM's own suggestion that irrespective of -ve zonal winds in the EPAC, a low frequency tropical standing wave will remain in the western and central Pacific in tandem with a developing twin low frequency signal over Africa/Western Hemisphere. The engagement of the former supports a Pacific downstream response, irrespective of the EPAC trade winds mitigating the signal and suppression of the Pacific standing wave whenever the twin signal in the Western Hemisphere is engaged, The GFS interpretation of the tropical signal is to propagate wave eddies into the extra tropics, fully engage +ve torques and the resultant push to angular momentum resulting in a break away into the El Nino attractor phases 5 and 6 of the Global Wind Oscillation Taken at face value, this would be a red flag signal for summer in our part of the NH to spectacularly reverse fortunes with anomalously very warm summer ridges extending across large areas from Scandinavia and mainland Europe in the east, through the UK and out into the central Atlantic and with the Jetstream displaced a considerable way to the north. The GFS interpretation of the GWO needs to clearly be taken with some certain caution, but equally a careful watch is required on any suggestion of early termination of this signal c/o trade winds killing off the advancing tropical wave prematurely. To add to the mixed messaging, the extended overnight ECM suite within NWP has two clusters of more amplified downstream response solutions than the first flatter cluster the operational and control sits within by day 10. A similar pattern exists within GEFS and GEM ensemble suites. One gets some idea of which tropical>extra tropical signal these cluster solutions are representing Furthermore, usual disclaimers applied with very long range suites - but the latest EC weeklies continue the theme of mid latitude more typical flow and signs that a trough/ridge interplay will persist from June well into July. But a clear evolving northward shift in jet stream trend that becomes more evident with time is suggested by these. Based on proxy and diagnostic evidence, including the tropospheric profile comparisons, there is some intuitive support for such a summer trend and this is consistent also with some of the helpful seasonal modelling evidence based summaries given by @Mike Poole amongst others Its always possible to check diagnostics vs NWP - and unless there is a very compelling signal one way, there is more often than not more than one possible solution ahead and which does not always tie with a bias preference solution. However, with the removal of the intense blocking signature over the polar field and a more traditional tropospheric mid latitude pattern returning with some zonal type flow, the influences within the tropics and extra tropics should no longer be scrambled to the extent they have been. That has consistently been the takeaway from these summaries for quite some time, and that time has now come when the way forward becomes more and more dependant on the tropospheric influences rather than dictated by late season intense stratospheric downwelling processes. With the well meant intention of trying to be helpful, I would suggest that those of you who are interested and there are some who try to contribute to this thread (notwithstanding the ongoing difficulties in doing so) as well as those who do not post but like to keep updated), continue to monitor some of these plots and indicated possible trends to see how the rest of the summer might play out. Whatever the weather holds, best wishes for the remainder of the season
  25. There is some sense within that post and I certainly agree with the opening sentiment that also applies to a core small number who persist in ignoring any objective discussions and instead appear determined to make this thread an unhelpful and tedious read. I guess that is where the ignore facility comes in use to provide some respite, though a big shame it doesn't also block out the text when these posts are responded to. The section about "background signals" though, like I said yesterday very often is misunderstood and misrepresented at all times of year. This term, is very overused and loses its true meaning and purposes. More specifically and accurately, it is a non numerical evidence based diagnostic process to identify the drivers at any given time that NWP is making its own calculated interpretations of. This means that if used objectively, it can provide a very useful insight into the range of possibilities within deterministic solutions and identify where patterns may change (or may not change where indicated to) based on a range of recurrent intra seasonal wind-flow signals and torque mechanisms that relate to the laws of conservation of atmospheric angular momentum. The diagnostic looks at wind-flow mechanisms which steer the jet stream and give clues to where changes may occur based on a range of teleconnections and proxy data which are well identified to produce specific synoptic responses within given ranges of parameters at different times of the year. It is not a stand alone approach and combines with other seasonal factors that include stratospheric and sea ice trends and states which can alter these synoptic responses. 2018 to 2019 alone has been a powerful example of this sort of complex blend of factors, which sometimes have a-typical and countervailing aspects and make deciphering aspects of weather pattern modelling highly challenging for the best professional minds - let alone the enthusiastic student with the curious mind at home. So the likes of the Global Synoptic Dynamical Model (GSDM) is a diagnostic supplement to purely NWP driven investigation, but NOT a silver bullet with sole purpose to endorse human weather preference from one season to another - though clearly there will be times when given factors will combine to include such a preferred solution within the overall diagnostic which may point to more than one possible solution in addition to the bias solution. The problem with threads like these, and its especially poor in winter with the huge volume audience all baying for one popular outcome, is that the bias preference overwhelms everything and people will latch onto the "background factors" if the diagnostic happens to suggest a percentage probability of the desired solution...but will choose to ignore any other solution. Other times, members will migrate to any NWP which may be following a signal that doesn't even exist within the diagnostic - and that is a time to not bother posting otherwise because such analysis would be considered being a "killjoy". Of course whichever route is taken, the end result is the same when the desired solution doesn't verify (which tends to happen more times than not when any selective process is undertaken). Irrespective of the reality, it will the be the "background factors" which are to blame - not the consensus bias of people who took the NWP model(s) at face value. And so it goes on from one season to the next and from year to year, with some none the wiser. So I don't accept its the diagnostic "background signals" that are wrong - its the human interpretation and applied bias use of them that inevitably increases error rate. So what is new today, away from the flurry of intra day reaction and overreaction to specific NWP outputs? This is interesting in terms of where convergence of tropical convection may be adjusting in the Pacific, at the same time as changing the Indian Ocean Dipole signal. Redolent of a semi quasi centrally based neutral/ El Nino type signal or very weak "Modoki". To try to put this into simpler language - This comes about through the effects of trade wind increases in the central and eastern Pacific, augmented by suppressed phases of MJO convection such as currently being witnessed as the active MJO passes through the I/O resulting in increasing cooling of the surfaces of the eastern ENSO Equatorial zones through upwelling. However, at the very same time, there is an opposite eastward moving current to observe in the Western Pacific which creates a convergence zone of maximum downwelling and consequential surface warming in the W/C Pacific. This convergence zone consequently spawns an ideal site for tropical deep thunderstorm convection development n tandem with a similar trend in the Western Indian Ocean where downwelling currents also create favourable cyclonic convection sites. Putting the two opposite co-existing signals in the tropics together, the net result of this is to create an a-typical Nino atmospheric imprint (La Nina like) on the rossby wavelength whilst the MJO imprints the warmest zone in the I/O but then defect also to a constructive coupled response in the Pacific when the wave phase propagates this region of the tropics. Why does any of this matter this far away? It matters because the tropical phase will be induced to produce the type of downstream response we are seeing at present with a downstream trough when the I/O low frequency signal engages, but with a tendency to contrasting signal of Atlantic trough and downstream ridge when the Pacific convective signal engages - and hence the opportunity for warm and settled spells maximised at this time. Its yet another of the factors that could be shaping this summer and why numerical models may be subject to curveballs due to a twin aspect tropical>extra tropical wind-flow signal. Something else to chew on while the rest of the previous analysis remains consistently on course at present. So, still cuing up some kind of mid month onwards shift : With the SOI still in negative territory reflecting the continued presence of a weak El Nino signal despite the destructive action of the supressed phase of tropical convection : and relative global atmospheric angular momentum still above average and with the active phase of the tropical cycle set to approach the Pacific from mid month... ..reflected by associated further rise in angular momentum tendency at precisely the same time as westerly wind bursts replace the supressed phase and easterly trade wind uptick.. ...then the pressure is growing for NWP to start reflecting a more downstream high pressure outlook and some kind of trough response in the Atlantic rather than the UK. But with the principle of the diagnostic in mind as discussed above, there is likely to be associated risk probabilities to continue to observe. The fly in the ointment remains the very stubborn -ve zonal flow at higher latitudes which continues to negate some of the more favourable warmer and especially settled aspect to the pattern, but this too should come under increasing pressure with summer seasonal wavelength changes as long as the I/O tropical signal does not start to dwarf the Pacific and become the more default response The latter will have to be continued to be carefully monitored, but plenty to observe as antidote to NWP derived swerves in temperament.
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