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  1. 38 points
    ...Like shoals of fish they are starting to point the other way in midstream... Recent NWP, up to the start of this week, had seemed suspicious the way it had reverted to extrapolating the default summer pattern out in time throughout the first half of August. Quite a subtle, but distinct shift has duly occurred over the last 2 days. Clear indications now that the return to cooler unsettled conditions after the upcoming plume is not in for a long haul, as by the second half of next week the axis of the upper trough looks set to re-orientate further away to the NW of the country and the Azores ridge allowed to create a downstream extension to extend and sit over and to the east of a greater part of the country. There is still likely to be some secondary trough inroads swinging around the main upper trough, but crucially the approach of these on a subtly different track - and advecting incursions of tropical continental airmasses ahead of them on a more regular basis and with the rather unseasonal North Atlantic airmass incursions less dominant. This implies an increased thundery nature to a greater number of the rain bands, with very warm/ hot sunshine in between, and winds much more often from a southerly vector than seen for much of the summer so far. There, I have said it.,..
  2. 37 points
    Self evidently this is yet more nonsense excessive hyperbole. Ultimately, and it seems ridiculous to have to keep mentioning it on the basis of the weather to come in the days ahead for many - the low frequency tropical signal will return and that implies upstream amplification also returning with the effect of the downstream ridge re-configuring westwards at the same time as pressure falls across NW Europe. But that emphatically ignores several days (at least) of some highly interesting and potentially exciting weather variety - with a distinctly sub tropical theme developing. The over dramatic "ouch" part relates to a computer model snapshot in time of the extended period - and ignores, or is perhaps more likely oblivious, to problems that exist with the timing of any return to the default pattern and also seasonal wavelength changes as August progresses and which do not necessarily compute to the same synoptic result as earlier in the summer. Some should seriously step back and stop paying such irrational lip service to each and every capricious NWP intra day suite. But then how many times has that been said and lost in the hiatus of reactivity rather than calm and rational proactivity with a distanced eye taken to the daily number crunching. It is much more self preserving to question the intra day outcomes rather than falling on the sword of each and every one of them..
  3. 37 points
    It gets a bit of a "boys own" scrum on here. Computer models being assessed like they are competing engines being road tested for performance. Temperatures being frantically compared from one computer model to another as if there is a prize for the winning number cruncher. l take the usual precaution of looking at numerical models before casting any glance over the posting on here, and, being totally detached by the highest temperature analysis and contest, remain quite satisfied with the outlook. That probably makes me the "outlier" in MOD thread parlance. As stated yesterday, prospects of an intense shorter term heatwave are being replaced by a warm/very warm summer spell of weather - taking the country as a whole and not catering for regional back yard interests which take up far too much bandwidth on this thread. The usual bemusing puzzle is why this is not enough for some participants. Getting away from the computer and being out in the sun itself means actually enjoying the weather so long anticipated rather than sitting indoors looking for "downgrades" and when it is likely to end or break down. ( It also means getting important levels of Vitamin D ) As much as being a fan of hot weather, am personally equally at home with plenty of summer sunshine and temperatures in the 20s and overnight temperatures holding reasonably as well. Does it really matter if the odd cloud occasionally appears on a given model screen grab at any time and threatens to interrupt the planned bronzing experience at t94 or whenever on a given planned visit to a beach or pub garden? .Does it matter that much if it is "only" ,say, 22C to 25C instead of 33C to 35C every day? This should be automated tannoy message for this thread at any time, but sensible and advisable to get a rational grip of the realistic limitations of the pattern over this summer which is not pre-disposed to 1976/1995/2003/2006 or 2018 style epic week on week heatwaves. On that basis the temporary interruption to the low frequency base state across the tropics controlling this summers weather pattern should set expectations and mean that onlookers should be grateful for this window of opportunity - and not instead bemoaning what are alleged to be squandered opportunities to break endless weather records and fretting over high upper temperatures being undercut by cooler level winds. With this in mind, there are good indications that such a pause (for some) over the weekend looks primed to be replaced by some humid and possibly thundery potential into next week. Plenty of different interest that *should* keep many happy in the context of the limits of this summer. That is the logical theory anyway. This island rarely has the same wall to wall conditions from its northern tip to its southern tip - but if that sets the expectation with some on this thread then it might be advisable to utilise the moans thread or individual regional thread because disappointment is surely inevitable time after time.
  4. 31 points
  5. 31 points
    A beautiful altocumulus castellanus sunrise this morning.
  6. 30 points
    Astonishing rebound in momentum transport that is behind the current spectacular synoptics and associated high impact weather. Both the heat, and also the powder keg potential for thunderstorms. The GWO has smashed its way through the El Nino attractor phases through into a weak amplitude Phase 5, based on the two day two consolidated lag. A reversal of the standing wave pattern between June and July and a resounding blueprint for the anomalous European and Scandinavian ridging presently in evidence. With that switch in mind, NWP has been suggesting, up to now, a wholesale collapse and reversal back of the present regime during next week. Times like this, ahead of a suggested vigorous pattern change, (or more accurately switch back to a previous pattern) require extra caution because while the atmosphere ""remembers" its previous behaviours, there is no linear one size fits all response from one season to another. Therefore expecting the same responses from the forcing within the tropics and extra tropics, season on season, is over simplistic and erroneous. Especially the size of the correction these models appear to have been predicting. Personally, with all the above waffle in mind, I am watching the disruption of the upper trough next week and how that phases with the residual heat lows from the stagnant heat dome mass that will have sat there for an extraordinary amount of time by the end of the coming weekend. No surprise at all that the Met Office have issued so many thunderstorm warnings day on day and no surprise at all if these calculations of how the Atlantic troughing phases with this stagnant slack low pressure mass runs into some difficulties. There have already been some incremental corrections westward with this process and there is time up to 7/8 days ahead for more of these All in all, a lot to be decided and not take for granted, from my own point of view at least, whatever the present modelling may presently suggest, from the early - but more especially mid to latter part of next week. Edit 6pm This was written earlier this afternoon until home commitments took over. Irrespective of the details (which are irrelevant in the circumstances at this distance in terms of what each model goes on show thereafter), the trend indeed continues further on latest 12z suite, so far, to take the main trough ever west of the UK in the middle of next week. This is one such example of not taking each and every NWP operational and indeed ensemble data at face value but treat them as a snapshot in time and watch instead how they trend over a day or preferably two at a time Should probably pin this as a rider to every post...signals lead models, models do not lead signals.
  7. 29 points
    My first attempt at storm shots (Please don't judge ) The cells are impressive tonight!
  8. 29 points
    I don't understand why temperatures need to be blast furnace level for people to feel satisfied. Mid 20s and settled is perfectly acceptable and useable.
  9. 29 points
    Excuse the self-quoting and the extent of the re-post but over two weeks further on in time, it is surely interesting to revisit this as a means to demonstrate how the utilisation of the global wind-flow and angular momentum budgets can prove highly useful in gaining clues when NWP gets carried away by negative momentum inertia and is blind-sided to the sudden switches in global inertia that lie hidden around a future corner. Hence, akin to the dropping of a red hot potato in the hand, the volte face of the retracted Atlantic ridge and downstream trough that blighted most of July. The largest westerly inertia push since the Spring is underway. Steadily rising frictional torque tendency within the tropics is finally engaging mountain torque tendency within the extra tropics Based on the low level of global momentum up to this time, this injection of wind-flow c/o rising torques within both the tropics and extra tropics has created a very strong rally angular momentum tendency set against such a below average level vs parity. This has been the cue for the models to ditch the persistent Pacific amplification evident since the start of the summer and re-configure the downstream pattern. The end of week plume this past Thursday and especially Friday has been just the opening salvo - much as anticipated in recent posts. The Global Wind Oscillation, a plot phase depiction of global wind-flow inertia, reflects the sharp uptick in momentum and underpins the pattern re-configuration with the downstream ridge tendency that is returning to NWP c/o an orbit dash out of the La Nina attractor phases and into Phase 4 for the first time since the start of summer This feedback builds towards the programming of the substantial heat ridging development through this week The wavelength/timeline of the downstream switch augurs better for at least the first half of August fortunes. The test will be how quickly the default low frequency signal across Africa and the Indian Ocean regains authority and starts to re-amplify upstream once more. However, that is for another time. Very good support for a phase of very warm/hot weather, and with the nuisance upper trough displaced sufficiently away to provide good injections of hot continental air. As stated the other day, secondary low pressure systems will provide interplay with the downstream ridge and this ups the chances for thundery activity including elevated importations c/o some destabilisation over the Spanish plateau. However, for the period under discussion at least, harder for cool North Atlantic air to make the ease of inroads so far east as seen so far this summer. The extent and intensity of the heat advected from southern europe is of course a subject of great interest from a meteorological point of view. From an enjoyment summer perspective many will be grateful for some stunning seasonal weather and it won't matter if temperature records are broken. Very warm evenings for sitting outside with dinner and some glasses of wine will be greatly savoured. Hopefully this will become a familiar form of relaxation when, eventually all being well, I arrive here at a new home an hour from Lisbon. Just got to get the builders in to provide a pool! But first of all fingers crossed that the deposit gets safely paid this coming week:
  10. 28 points
    Last view before the light went....Oxon cell.. I do have a theory viewing this weeks storms over the South/Central and France... With the heat and humidity, so many people nowadays have dehumidifiers, that these are sapping the storms mojo so much that they start and then stop again. People in Cumbria and Lancashire think a dehumidifier is what you use to dry your house out after major floods.
  11. 28 points
    The threads been a bit derailed this eve with a lack of analysis. For the hot weather to remain in situ over England on Sat the wave that has been highlighted for 2 days now would need to track through Scotland & SSW exiting Cornwall thus protecting a big swathe of England from the cooler uppers from the North. The GFS has been to progressive with the cool air & the UKMO has been the opposite. Usually the GFS moves to the UKMO however seen by the charts below which are the same day 24 hours apart (12z runs ) UKMO has corrected SE & the GFS has corrected NW both by about similar amounts so that we are beginning to converge on the 16c Line straddling the SE & the 8c line somewhere over the NW UKMO yesterday 120 first V todays 96 GFS yesterday 120 V todays 96 What we actually have is minimal corrections from day 5 down to 4 > A range of about 50- 75 miles is well within natural variability- & for once the models are perhaps beginning to meet in the middle halfway house. Sadly for some the correction SE from the UKMO swings the surface temps down by around 10c for some going from mid 30s to mid / high 20s. With that annoyance out of the way heat builds back from the SE but its not quite the major heat for records which for most is fine. Some models still hold back the wave to the North & still scope for it to move either way but higher probability would be a move NW not SE. Lets see what tomorrow brings.
  12. 28 points
    A frustrating chase where I spent more time stuck in the car in either heavy rain or heavy traffic, but a few shots came out good! Daytime shot from Holme upon Spalding Moor, having been stuck for 45 minutes in roadworks before! Only had 5 minutes before it was on me! Night shots are from Grindale and Flamborough, East Yorkshire! I guess I could have stayed at home and probably nailed the shot over the south bay I've been trying to get for years but maybe next time!
  13. 27 points
    *** USING THE ECM TO FORECAST TEMPERATURES IN A HEATWAVE - A REVIEW *** I often make predictions based on models several days ahead, and then I find it useful to revisit these predictions after the event to learn for next time. Those who follow my posts know I like to use the ECM to forecast temperatures. Although I find them to undershoot actuals, the point is that the ECM op often picks up on the general trend several days before, and at very least undershoots actual temperatures in a fairly consistent manner. My idea is, if I can work out how much the ECM is likely to undershoot temperatures, it is then possible to adjust the raw values to make an informed prediction in future events. This particular period was of great interest because, very early on, several ECM runs suggested an extended period of extremely hot days for the UK, including a fresh attempt at a UK temperature record. So how did it do? I'm interested in two things 1. Did the ECM (generally) have the right idea about what was going to happen with temperatures at an early stage 2. Was my idea that ECM raw temperatures generally undershoot the actual maximums by 2 to 4C? I've gone back through the MOD threads and found the following predictions from the 12Z run raw maximum values (obtained after each run from weather.us) from August 1st, 2nd and 3rd August - I provide the raw values here, not my "adjusted values". Then, I've listed the "on the morning predictions", which were the maximum "raw" values predicted on the 00Z runs of the same day as the forecast was for - this is followed by the actual maximum, and the difference between the raw and actual. AUGUST 1 (12Z run) Thurs 29 [T120] Fri 33 Sat 34 Sun 37 Mon 35 Tues 34 AUGUST 2 (12Z run) Thurs 28 [T96] Fri 32 Sat 32 AUGUST 3 (12Z run) Thurs 28 [T72] Fri 32 Sat 33 Sun 31 Mon 34 Tues 36 Weds 35 ECM” ON THE MORNING” / ACTUAL / DIFF Thurs 28 / 30 / +2 (Northolt) Fri 34 / 36.4 / +2.4 (Heathrow) Sat 33 / 34.5 / +1.5 (East Sussex) Sun 33 / 34.0 / +1.0 (East Sussex) Mon 33 / 35.5 / +2.5 (Heathrow) Tues 33 / 35.7 / +2.7 (Heathrow) Wed 33 / 35.4 / +2.4 (Heathrow) Thurs 29 / 29.8 / +0.8 (Portmadog, a totally different location!) MY SUMMARY: For my first question, did the ECM spot the trend early on, I would say definitely "yes". It had already seen the longevity of the heat even out to D10 on the August 1st run. I appreciate some of 00Z runs were less certain about this longer period, as was Aug 2nd 12Z, but as it is quite unusual to get a plume that gets trapped for several days over parts of the UK, in my opinion it was quite impressive that the ECM had alerted us to this possibility so early on, even if it did slightly overdo the heat in the latter period of the heatwave. If one averaged out all of the runs, 00Z and 12Z between the 1st and 3rd, though, I think you'd probably have got a fairly accurate picture of what the raw values were to be predicted by T0. Bear in mind, at this stage, the GFS was predicting 23C or 24C maximums after Saturday 8th!! On the second question, I'm mostly interested in comparing the "on the morning" figures to actuals, as taking a prediction from August 1st, for instance, may have varied from the actual due to modelling error, not systematic undershooting of temperatures. Using this comparison, one can see that raw values undershot actuals by between 1C and 3C. This was a bit lower than I'd expected - in the past, between 2C and 4C works. My tentative ideas for what has happened here are as follows: - A high level of uncertainty due to thundery outbreaks and cloud levels make it very difficult to forecast temperatures correctly. Yesterday, the ECM raw values actually needed to be adjusted downwards in areas where cloud and rain was more extensive than forecast. My sense is that the ECM has done this before. So, conclusion 1: In future thundery outbreaks, I will not assume there will necessarily be any uplift on raw maximums at all, and I will continue to analyse this specific context. - On Saturday and Sunday, the raw maximums were forecast to be in the Sussex countryside, and only a 1C to 1.5C uplift was observed. I studied private weather stations in inland Sussex that day, and they were a good 2 or 3 degrees up on all other areas even in the South East and London. I suspect that the raw maximums probably did undershoot the actual maximum by 2C to 3C (and there were genuine maximums of 35C and 36C), but the sparsity of official stations meant these weren't picked up. So conclusion 2: when the maximum is forecast for a rural location, do not take this as a representation of what the maximum official value will be. For that, stick with raw maximums in more urban areas, or airports. - On other days, both raw and maximum values were in or around London, and an uplift of 2C to 2.7C was observed. This is in line with what the relationship I have noted in the past between ECM raw values and actual values. So conclusion 3: Adjusting the raw values by 2C to 3C works when the maximum is forecast to be in a more densely populated area with numerous reporting stations. Of course further possibilities exist which could explain the difference in the adjustments needed; for instance, does the ECM handle heat levels in urban and rural areas differently? Also, I have noticed it doesn't have the best handle on coastal areas - my local station in Gosport was often 4C or 5C up on the ECM "raw" (and a number of other charts, too!) On the whole though, I am fairly pleased with my "project". The initial heat predictions which seemed so outlandish at D7/D8/D9 ended up not too far away, though not quite record-breaking. The idea of adjusting the raw maximum again showed to have value, though with some minor inconsistencies. Hopefully this kind of analysis will help us get an early handle on the next future heatwave. Expect the ECM to be the first to see the big picture, averaged out over a few runs. Expect the raw values to be a little too low, though take note of where maximums are predicted to be, and how unsettled the weather is forecast to be. And now back to the future
  14. 27 points
    Played around with Bristolstormchaser’s photo from twitter on my phone. That thing is an absolute specimen.
  15. 27 points
    Pacific cyclones are a good thing for Western European summers - it demonstrates that the ENSO region is convectively active, trade winds reverse c/o the westerly wind bursts which accompany the thunderstorm and cyclone development and can help the downstream pattern reverse from what we are seeing this summer with a corresponding low pressure anomaly centred to the west in the Atlantic and a perpetuating downstream ridge which ebbs and flows over and to the east (in the same way in reverse that the default retracted Azores ridge is to the west this summer due to the opposite much less helpful configuration) Hence, much more continental influence than we are seeing this summer and also thundery potential as the default Atlantic trough disrupts against the downstream ridge from time to time. Rinse and repeat in a very good way. In the present however, with so much influence from the North Atlantic arcing around the perimeter of the retracted Azores/Atlantic ridge it is no surprise to see the cool and changeable pattern that has dominated and with the upper trough being constantly reinforced to the N and NE and preventing any continental influences. Also no surprise that, last week of June aside, thundery potential from plume scenarios has also dwindled to nothing. The reality is that it was possible to see back in May that a traditional La Nina-esque type circulation might well develop and associated Atlantic ridge and downstream trough - what couldn't be predicted was precisely where tropical convergence would arise and on that basis it was quite possible that a more blended pattern may have resulted. Indeed for a time this was actually the case as the late June mini heatwave demonstrated. However,. the high frequency MJO tropical cycle has become very quiet since late Spring, and following the active cycles during Spring itself which generated the westerly inertia and sustained atmospheric angular momentum above average. More about the high frequency signal later into the post. Frictional torque tendency has been buoyant as described in previous posts. However following what has transpired to be a brief westerly wind burst east of the dateline, and which if sustained would have helped the possible signs of improvement that were apparent up to recently, much of the inertia is now concentrated south of the equator in the southern hemisphere and trade winds across the Pacific look set to see further quite strong phases through the second half of July This will certainly serve to keep angular momentum below average and the Global Wind Oscillation spot welded in the low angular momentum La Nina attractor phases. Notice the contrasting westerly wind anomalies at 30N prior to the start of summer driving the downstream anticyclonic wave-breaking and the switch to easterly inertia at 20N to 30N in recent weeks - switching to upstream amplification at the inflection point of the negative torque mechanism - scrubbing all the westerly inertia from the system .....and this in turn will perpetuate the upstream amplification and the downstream response to that of an Atlantic ridge and upper trough that keeps trending into Scandinavia. NWP at present is showing some signs of e/QBO type stratospheric interference which up till now has kept at least the sub tropical ridge in play and prevent a sustained supressed jet stream sinking further south. On previous occasions the modelling, for reasons given back then, has rowed back on this development, so a watch is required as to how this plays out this time. What could help alleviate or provide some respite from this disappointing pattern? Signs of some activity from the high frequency MJO tropical signal propagating eastwards from the Indian ocean and at least temporarily acting "destructively" on the default walker circulation which is rooting the low frequency tropical signal across Africa and the Indian Ocean and which in turn is boosting all the easterly (trade wind) inertia across tropics and into the Pacific. It is this atmospheric chain that sets up the downstream responses that are so evident. Also heading ultimately into the latter part of summer it could be that just a small recovery of momentum c/o of some MJO related activity allied to ex tropical activity curving around into the Atlantic may create some warm air advection to shake up the pattern - at least for a while. Even in default long term term regimes such as these, it is natural for there to be a "wane" phase. Low angular momentum summers quite often see this the further one heads into August and often September as well based on intra-seasonal factors that can drive these temporary changes before the ridge/trough regime returns into autumn. Though some will consider this too late, the reality though is there is a good 10 weeks or more where summer like temperatures are quite easily achievable with better synoptics. I would recommend looking into the diagnostic element as described and at the whys and wherefores - understanding why patterns entrench themselves like this is a constructive antidote to the rather pointless and self harming processes of agitating and moaning about the weather outside the window and which should be in the appropriate thread anyway, if one has nothing better to do with their day
  16. 26 points
    Morning all UKV also keeps the heat going through Wednesday and Thursday - subject to change. Big excitement for me this coming week is the thunderstorms risk - severe in places. (UK and Ireland) Sunshine/warmth/heat/thunderstorms...that’s what Summer is all about for many of us. Have a good day everyone.
  17. 25 points
  18. 25 points
    That’s the outline of the Brecon storm from 60 miles or so to the NNW
  19. 25 points
  20. 24 points
    I have a piece of a tree that was just struck about 10 mins ago. There’s a small fire and the Fb are just turning up
  21. 24 points
  22. 24 points
    Now look at this beauty. Coming in from the south west (I'm in Deiniolen, north west Wales)
  23. 24 points
    Lightning strike to my north 5 minutes ago! I set up my iPhone and managed to catch this beauty.
  24. 24 points
    @Tamara I wonder if you might answer a couple of questions I have about this. - You note the inevitability of the low frequency tropical signal returning (which you have previously described as "default") and promoting upstream amplification etc. - You also later refer to the default pattern and seasonal wavelength changes in August. I wonder if you could flesh this out a little more. Firstly I'm interested in what you mean by the default pattern. Do you mean on a global basis, or are you specifically referring to default patterns for a UK summer, because there seems to be an implication regarding the effects of this change on UK conditions? I understand that there are more and less typical broader patterns, so an Azores high is typical while a Scandinavian high is less so, but even if you imagine a default Azores high in place, there are many ways for the UK to retain a warm/continental flow, for instance, just as there are ways to be cool and wet with warm southerly or easterly draws. So what is the implication when you say the default pattern will return? Do you just mean, default broader patterns will return, accompanied by relatively moderate conditions and all the usual uncertainty, or are you implying specific conditions in the UK? I suppose I'm asking here because if default broader conditions are to be significant (as you suggest they are) in this context they must imply specific effects for local weather. And yet looking through recent summers we have had prolonged spells of both warm, settled weather (probably majority overall) as well as wetter, cooler weather, such that it is not clear to me what our default summer weather is. So it's not clear to me either what default conditions locally are, or that globally default conditions have predictable effects on weather locally... Secondly, can you add any further detail about seasonal wavelength changes? Is this to do with the jet firing up? Does this mean August should actually be expected to be a less summery month overall than June/July? My understanding was that our recent run of our Augusts was anomalous set against long term averages. A few questions in there I know. I hope you can pick that apart... ----------------------------------------------------------------------------------------------------------------------- An interruption to the heatwave nowcasting being monitored on this thread, but still an important one in my opinion nonetheless. This valuable post by @wellington bootrisked being lost as the previous model thread was closed yesterday morning very soon after it was posted. So I have re-pasted it because it covers the essential points that have been made throughout this summer, so far, and which will continue to be primary influence for the rest of summer and into the following season as well. When I have spoken of the "default" pattern, so often as it has been referred to, that means the primary driver in the tropical> extra tropical circulation that has created the negative inertia wind patterns that translate to an upstream amplification across the Pacific - and which has led to the synoptic downstream configuration of an Atlantic ridge and trough across NW Europe and Scandinavia. So the default pattern hasn't been referring to traditional UK summer patterns - but specific signals that have been primary influence over the summer (at least up until very recently) across the UK and other parts of NW Europe and Scandinavia The low frequency tropical convection signal (the default) controlling the pattern has been rooted, since the beginning of June, across Africa and the Indian Ocean. The persistence of this signal is denoted by the velocity potential convection anomalies (shaded blue). Note how the twin low frequency signal faded in the last part of May across the Pacific and left the African and I/O standing wave to dominate. This positioning of the dominant singular low frequency signal creates uptick in low level easterly trade winds (the African Easterly Waves or AEW) that steer the tropical cyclone developments westwards in the Equatorial Atlantic along the southern perimeter of amplified Bermuda and Azores ridges to the west of the UK. On the northern perimeter of these ridges, has been compensatory increased polar jet energy - hence the low pressure sequences that have kept passing close to the NW of the UK with persistent relatively cool air flowing across the UK from the Northern Atlantic. Recent posts, at least since the second half of July, anticipated a break in the influence of the low frequency signal as the high frequency intra seasonal MJO has overridden this c/o an eastward progression across the tropics which has scrubbed out quite a significant amount of this easterly inertia which has re-configured the upstream pattern (de-amplification). This added momentum transport between the tropics and extra tropics, c/o positive frictional and mountain torque mechanisms, creating rossby wave-breaking downstream, carving our our downstream anticyclone, reversing the pattern configuration of the summer to date and promoting heat advection from southern europe, . The extent of the uptick in momentum (and the reflected extent of the pattern change for the better downstream) is evident from the Global Synoptic Dynamical modelling (GSDM). This is a diagnostic (non numerical) model that calculates wind-flow inertia across the globe. In other words in simple terms it is a useful guide to deciphering jet stream patterns. With so much of the excess easterly inertia scrubbed from the atmospheric circulation at this time, AAM has recovered with a sharp uptick to average levels for the first time since the end of Spring. It is no coincidence that the fall in AAM began just as summer appeared and at the same time as the low frequency tropical signal switched away from the Pacific. It is equally no coincidence that AAM has recovered just as that low frequency (default) signal has been interrupted for the first time since the start of summer. The longevity of the current heatwave centres around the wavelength (timespan) of the influence of the MJO phase cycle that created the distinct upturn in angular momentum tendency. When this intra seasonal signal fades, this will be the cue for the upstream pattern too re-amplify and what I refer to as the underlying default pattern to return. NWP is playing with this evolution in the extended period with hints of a return of an Atlantic ridge with the strngest anomaly to the west of the UK, rather than downstream to the east.. However, considerable intense heat build-up across huge expanses of the mid latitudes, very much including all of Europe means that this process is nowhere near as clear cut in terms of any progressive cool-down as during the earlier summer. Additionally late summer seasonal wavelength changes make it likely that pressure fall across Scandinavia will not be as easily achieved as earlier in the summer. Therefore the pattern could well evolve into an an anomalous Atlantic ridge bridging with enough strength to keep deflecting the polar front far enough north to retain a warm airmass in place for some time. Whilst these will be almost certainly less intense then currently, any dramatic modelling over the coming 10 days that tries to show a sharply retracted ridge, falling pressure to any great extent over and to the NE of the UK - and substantial inroads of very much cooler air very far southwards should be, at present at least, treated as suspicious and an overreaction to falling momentum upstream. That said, angular momentum will definitely fall back when the high frequency signal completes its eastward progression across the tropics, and the trade wind influence returns across the Equatorial Pacific and Equatorial Atlantic, but it is far from certain that the downstream pattern will revert to precisely as it was before the heatwave. The coming several days, at least, are set for some quite remarkable summer weather - irrespective of whether 38C is breached or not in the immediate future
  25. 24 points
    So my take on this outrageous ECM run - taking raw values and adding 2-4C to get nationwide highest temps: Thurs 30-32 Fri 34-36 Sat 35-37 Sun 33-35 Mon 36-38 Tues 38-40 (FORTY) Weds 37-39 It's easy to forget this is the best verifying model in the world. Could it really happen? Feels like a dream.
  26. 23 points
    Yep sad when people get jumped all over for daring to take a view that differs from what people want to see. Whatever happens from now on, people can't really moan about this August.
  27. 23 points
    Lol - Note the awsome accuracy of the UKMO 144 last Monday 00z for today + 0z today side by side
  28. 23 points
    Few captures from yesterday’s chase (31st July 2020) between two counties Nottinghamshire & Lincolnshire. Day started off setting off from Plymouth (Hometown) potentially heading into Kent for developments pushing up from France but my gut told me to hang off with an opportunity in pushing North. Hanged About in Cambridgeshire which looked to be a good half way point to both ends but given convection was starting to fire up towers I made the crucial call and go with what I thought best pushing north into Leicestershire when we was welcomed by storms firing up all around. Ended with an amazing sunset!! May think I’m nuts coming all that way but I love roadtripping and so do my two sons. Going to suffer in work tonight I’m nackered.
  29. 23 points
    So just for fun, here's what the ECM would mean for maximums if one adds the usual 2-3C : Thursday 31-32 Friday 35-36 Saturday 36-37 Sunday 39-40 Monday 37-38 Tuesday 36-37
  30. 23 points
    There is an indisputable correlation between rising global atmospheric angular momentum and associated poleward advection of rossby waves created via torque mechanisms propagating such eddies in the jet stream between the tropics to the extra tropics. - this subsequent wave-breaking leading to the production of downstream anticyclonic ridges. The synoptics that arise are led by seasonal wavelength changes throughout the year, but rising AAM indicates westerly inertia being added within the tropics c/o eastward propagating tropical convection waves and which leads to ridge development in the extra tropics as the westerlies within the polar jet are prone to amplify and buckle downstream as the upstream pattern at the same time sees a de-amplification and jet extension across the Pacific. Understanding these processes and awareness of them gives a good insight into how NWP models the jet stream and this has to be seen as a useful tool in deciphering synoptic pattern evolution. It only becomes perceived as a "cure all" if such diagnostic processes are attempted to be fitted to idealised weather pattern biases without consideration of all other probabilistic outcomes, and which may be more likely at that given time. That said, and as outlined already by process - rising AAM is a very important ally to the creation of very warm Western European Branstrator ridges in summer. It is encouraging that the well respected Euro atmospheric modelling is on board with other model suggestions of recovery of angular momentum heading into August. This increases the chances of further ridge development to a higher level than seen during July and tendency for the jet stream, over time, to adjust somewhat northwards. With that in mind, I would be taking all NWP and ensemble/cluster data with a lot of caution beyond the limits of the plume advection later next week and weekend. The suggestion of the walker cell low frequency signal across Africa and the Indian Ocean continuing to control the pattern quite as rigidly as up to now as set against the uptick in momentum budgets and associated increase in wind-inertia which will have a knock on effect on upstream pattern may well be overplayed on this occasion - rather than the underplaying of that signal that has occurred since the plume event of the last week of June. Such underplaying as demonstrated by the Azores ridge flattering to deceive beyond about day 7 to ridge fully and expansively eastwards - only to correct backwards as closer time periods arrive. So it is not unreasonable to start to see some corrections the other way around with time - that is, notwithstanding some initial erratic progress probable early in the month which might lead to the illusion on a thread of fickle emotions of a thread like this, of August as a whole simply being more of the same. Potential model error likely occurring due to such over estimation of default Nina influence increase the further that August progresses - leading to the Nina-esque "wane" period as discussed in previous posts. This arising, as the intra seasonal high frequency MJO signal progresses eastwards across the tropics and (temporarily) "destructively" interferes with the underlying low frequency signal that has been dictating the pattern since the beginning of summer. One might expect the underlying La Nina-esque signal to return heading into the autumn, but the chances are increasing for the third phase of summer to improve with time and the upcoming plume scenario should not( in my non-forecaster appointed opinion) be seen as a last taste of summer proper
  31. 22 points
  32. 22 points
    The problem we have is, these storms are surface-based and generated by low-level convergence - they eventually managed to punch through the cap, leading to explosive development. However, the cap is still largely in place, and while the storms create their own environment and tap into the moisture-rich surface air, they are primarily forced just from the surface - so as temperatures at the surface begin to cool and low-level convergence reduces through the evening, that only leaves the storms with one choice: to become rooted at some elevated level instead and feed off the moisture available there. Problem is the lack of any substantial forcing aloft to support elevated thunderstorms at this time, and so ultimately after an initial flourish they begin to weaken... In theory better forcing aloft arrives from the west in an hour or two, so should hopefully see an uptick in elevated thunderstorm activity over mid/north Wales 9-10pm, and then later across NW England...
  33. 22 points
    Heres a nice panoramic of it as i couldnt fit it in the picture with an ultrawide lense!
  34. 21 points
    Flamin' typical...me n the wife took a drive towards Ludlow earlier as we thought there was a big cell developing but no luck there...so on our way home, we see this monster developing on the radar out of nowhere, arriving on our doorstep in Bromsgrove and what a view it was from Callow Hill...the wife couldn't get a pic of the face which was evident on the right hand side as it erupted so quickly....so we hammered it back to Bromsgrove thinking a tornado may pop up only to see it fizzing out... I think we'll stay home tomorrow just in case!
  35. 21 points
    Slide into Autumn lol. Another poster that likes a wind up. The 00z GFS has temps widely mid to high twenties for the 20th of august. If that's autumn i cant wait. The 06z is lower, temps widely between 17 and 23c which shows the large difference between runs and therefor low confidence which is to be expected at such range.
  36. 21 points
    The quoted section and especially the bolded part are duly the focus for the coming period. It will take the convective MJO related envelope to propagate to the Maritime Continent before rising angular momentum tendency can start to alter the downstream pattern more sustainably. So underpinning expectations of a further changeable and cooler period to get through before any changes become possible into the new month. Extended NWP evolution is hampered by the fact that RMM MJO analysis modelling is totally scrambled by being superimposed over the low frequency standing wave across Africa and the Western Indian Ocean. So until a clearer trend emerges of the high frequency tropical convection signal propagating eastwards into August, away from the Indian ocean, then the numerical models will keep extrapolating forward the default pattern of the Atlantic ridge and downstream trough and keep delaying any suggested improvement out in time. However, taking NWP and its associated ensembles and clusters at face value requires even more caution that usual because they may act like shoals of fish pointing one way upstream and then suddenly change direction mid stream when the underlying signal emerges from all the "noise" within the tropics. Signals lead models, not the other way around The bottom line is it worth taking erratic extended NWP and modelling such as the EC weeklies with a large spoonful of salt until the signal from the tropics becomes clearer - fine margins in this situation could result in significant changes. Even if such a change would not be likely to produce a long lasting pattern change. However, aside from the very pleasant weather outside my window at the moment in my own locale and where some of the better weather has been - for a summer such as this from a more widespread perspective, many would take a true taste of seasonal conditions however long it might last. This is good analysis by you and it echoes the diagnostic sentiment as described above The final bolded text sentence is the only bit I would not agree with. Based on where the low frequency signal is aligned across Africa and the Indian Ocean and how angular momentum is likely to re-align from any upward trend during the first part of August (depending on the eastward extent of the high frequency MJO signal) there is no prospect of any orbit towards the El Nino attractor phases .(i.e from GWO phase 4 into Phase 5). The last attempt to lift angular momentum in the last week of June as we know was half hearted and only resulted in the GWO transiting through Phase 3 - before heading back to the Nina GWO phases and hence the heatwave/plume of that week subsided to the suppressed pattern that has largely dominated July to date The GWO is wholly restricted within the tropical>extra tropical negative wind-flow inertia created by the position of the low frequency tropical convection standing wave across Africa and the Indian Ocean - and the associated suppression across the Pacific. Hence the default phase is orbits focussed converging mainly around La Nina attractor GWO Phase 2 The maximum outcome this time around, based on long term GSDM wind-flow budget inertia within the atmospheric circulation is a more progressive push through Phase 3 into a low amplitude Phase 4 at the very most. That said, to achieve Phase 4 is arguably at least as difficult to achieve as late June and also based on shifts into high summer wavelengths - such has been the slide in global atmospheric angular momentum this summer to data. Adopting the same principle as with numerical modelling, care also needs to be taken with taking any composite for GWO phases at face value. These composites need adjusting to cater for all relevant drivers influencing the macro scale pattern at any given time and each situation taken on its merits and individual interpretation taken of the composite accordingly. This type of bounce in angular momentum tendency, related to the base state circulation, would likely be enough to promote a downstream ridge as the progress of any incoming trough would slow down sufficiently to promote a plume scenario - but would almost certainly be at behest of when the low frequency signal in the tropics returns to default. If there is shortfall in the intra-seasonal MJO propagation beyond the Indian ocean, that would push the trough through and then revert back to a retracted Atlantic ridge and downstream trough At present, there is certainly still time for adjustments to improve the chances of the former plume type scenario - but this is very dependant on the propagation progress of the tropical wave within the "mini ENSO cycle" - aka the MJO. If this is insufficient, weak and soon aborted, that means the default supressed pattern returns swiftly. On the other hand, if the models underestimate the (temporary) effects of the MJO masking the dominant walker cell circulation, the numerical models may tone down the upstream amplification and instead switch to a more expansive downstream ridge scenario and provide some relief, for a time anyway, from the tedium of the default pattern
  37. 20 points
  38. 20 points
    The Andover storm drought is over. Wouldn’t be surprised to hear of some funnel reports from this.
  39. 20 points
    Just uploaded a timelapse of the incredibly photogenic thunderhead to my SW yesterday evening and a timelapse of the big storm over Birmingham
  40. 20 points
  41. 20 points
    Just back from a nice few days up in the Highlands. We were very lucky with the weather
  42. 20 points
    No real change from what I've seen so far - as is often the case, tonight is a rather complex situation. The elevated mixed layer (EML) will cover most of England and Wales tonight, pushing north towards southern Scotland - so any minor upper forcing may just be enough to develop the odd rogue shower/thunderstorm almost anywhere. However, the main focus is across western Britain where upper forcing will be stronger as a couple of shortwave troughs move north. These help to cool and moisten the upper/mid-levels, generating more instability and encouraging lift. Forecast profile for Wales (below) yields some quite deep elevated convection, IF profiles can moisten sufficiently (they are rather dry right now). This is most likely to occur as one of these shortwaves approaches. From what I can see there may be a minor shortwave (dashed magenta below) running north from north Wales / Midlands into northern England during the night, followed by a more substantial shortwave (blue line) that approaches Cornwall around midnight and heads into Wales late in the night. Elevated thunderstorms often develop along Theta-E ridges, and I've tried to identify the location of this through the night (right image) - notice how as an upper low develops near the Channel Islands, the ridge axis remains more-or-less locked here while it bulges more significantly westwards across Wales through the night. Essentially what you'd be looking for is where either of these troughs (left) overlap with the Theta-E ridge (right) for your best chance of elevated thunderstorms developing - but it is likely the more substantial trough will arrive quite late in the night, so activity may be fairly isolated until this stage.
  43. 20 points
    The way some go on, weather stations should only be placed in the middle of nowhere where no-one lives. They seem to think the station is in the middle of the main runway and being blasted by jet exhausts. I’m surprised they haven’t claimed that the fire at Heathrow yesterday was the station being set alight by the Met Office and blaming the high temperature reading on that. It’s tiresome reading the same comments every time we get a hot day. As if the Met Office aren’t careful and don’t take certain factors into consideration when locating a weather station.
  44. 19 points
    Holy guacamole! What a sight the 00z run is to wake up to. Basically getting stewed for a week with storms galore and 30+ degrees every day, with a few days shooting over 35c! Brace yourselves everyone, looks well and truly like we are on the verge of properly going into the furnace.
  45. 19 points
    View from Bromsgrove of the Wales storm . Stunning
  46. 19 points
  47. 19 points
    Its hard to not write extensively about this because I am very much inclined to agree with you.. So that is what I will have to do. Advice would be to bypass this post, those who participate and/or read this thread and who are not interested in detailed perspective analysis that comes from a diagnostic and proactive point of view, rather than reactive to NWP operational.. Assessing wind-flow inertia, and how it influences angular momentum tendency, across the hemisphere is very useful guide as to jet stream pattern behaviour when used objectively and with no preconceived agendas. However, unfortunately, as technical diagnostic tools like these (most especially the forecasting products), become more familiarly spoken about by larger numbers of people they tend to become dumbed down and treated as over simplified and misconstrued magic bullets as a means to arrive at x+y= outcomes. Such outcomes often bias skewed to what a given individual would like to see, rather than the helpful guide to the range of probabilities they offer in proper practice The twitter-sphere doesn't help in the respect. Far too many over simplified absolutes are conveyed in limited text communication which leads to incomplete, inaccurate and misleading information being accepted as a given, the further the message travels outwards. This in turn leads to discrediting and ignorance of the true purpose and value of these essential meteorological aids - and the science that drives them is lost as the expense of being abused as a novelty fixit. Additionally, the feedbacks to these wind-flow patterns are subject to variation due to seasonal wavelengths and the effect they have on adjusting the longwave patterns as changes occur between the tropics and the pole. So trying to extrapolate the same feedback over straddling seasons further and further out in time will inevitably lead to error - due to the effects that seasonal wavelength changes have on patterns. So, taking all this back the here and now - its worth repeating, once again, a lot of caution is required trying to make assumptions that the extended period is going to be some precise carbon copy of the earlier summer and that somehow this makes an early autumn (in terms of weather type rather than merely the anticipated change of season) an inevitability. If predicting the weather was a simple as that, most of us average jo's would have cleaned up financially be now and would be putting our feet up somewhere that meets all our dreams. Wherever, and whatever that may be. As stated yesterday, and all the models now agree with this, amplification of the Atlantic ridge is highly intuitive to the eventual return of influence of the African and Indian Ocean standing wave as angular momentum slips downwards. It is also likely that the heat will relax its grip over the weekend, but this is a slow process of attrition and all the hyperbole of descent into autumn needs to be put into context of just how hot, both day and night, the current pattern is and will stay like for more to days to come yet. Any westerly influence, should it ultimately arrive, would feel a contrast to such anomalously high levels of heat that will continue to dominate through this week. Timing of all these changes is also very problematic. Such is the nature of numerical models that will pounce on an emerging signal and tend to go into overdrive and overdo the change it suggests Analysis of the here and now is always a good place to start to get some proper perspective on where we are and where we might head, rather than jumping on extended forecasts that are not based on any knowledge of consolidated, present day, data Angular momentum has actually surpassed expectations with its rally since late July. A deficit of more than -2SD (standard deviations) below average has been overturned in the last 10 days and globallly averaged angular momentum is even a fraction above average. This, based on strong propagation of +AAM anomalies from the tropics to the extra tropics. Mountain torques in the extra tropics have scrubbed out considerable easterly inertia Take a look at how the passage of the MJO high frequency signal is overriding the standing wave across Africa and the I/O . The velocity potential convective anomalies, depicted blue, have flipped the pattern heading towards and into the Pacific - and with the low frequency standing wave under supressed convection (shaded orange) The long persistence of easterly trade inertia across the Equatorial Pacific has been cut off. Westerly winds are apparent close to and east of the dateline The Global Wind Oscillation, a plot depiction of net wind flow inertia after additions (or subtractions) via global torques has rocketed in orbit, subject its two day consolidated date lag, into amplitude Phase 4, and is even testing the El Nino attractor Phase 5 threshold. The significance of this is to show how the low frequency standing wave (low momentum default) has at least temporarily (almost) arrived at the point of reversal. Hence the spectacular showcasing of strong downstream heat ridges leading to our NW european cauldron of pressure cooking. That isn't hyperbole, it is factually what has happened. So what is to come? The caution, and usual suspicion with NWP as far as I am concerned anyway, is how fast and to what extent, they are handling the breakdown of this pattern after next weekend. The ECM continues to be a day or two faster than GFS, And there is a risk all NWO could be too aggressive with this. In the extended period, and based on how the momentum budgets have been stretched upwards like elastic from the summer low benchmark, the numerical modelling will be susceptible to being spooked by an equally sharp snap-back of a wind-flow inertia rubber band. However, while the atmosphere often "remembers" its previous default feedbacks based on known intra-seasonal tropical and extra tropical phenomena - it is not always as simple as "what goes up, must come down" on some like for like quid pro quo basis. Based on the persistence of the low frequency signal into the autumn, this does imply persistence of that Atlantic ridging, and the inherent inclination for numerical models to want to angle the jet stream around the northern and eastern perimeter of this ridging and dig a trough far southwards. More on this shortly. Question marks persist over the enigmatic behaviour of the QBO. There is now a very high chance of failure of transition, despite some (future seasonal!) wish-casting in other arenas. Note that July has now reversed the easterly downwelling phase 2020 : Jan -2.51 Feb -3.20 Mar -4.36 Apr -5.03 May -4.86 June -2.78 July +0.34. QBO Calculated at NOAA PSL 30mb zonal wind at the equator, zonal average For info Climate Indices: Monthly Atmospheric and Ocean Time Series: NOAA Physical Sciences Laboratory PSL.NOAA.GOV US Department of Commerce, NOAA, Physical Sciences Laboratory With this, there are now implications for the high frequency MJO signal to remain more active heading into the autumn proper and this would have the tendency to persist in anticyclone wave breaking based on continuation of a +NAO profile and a stable profile across the polar field. On that basis, there risks overreaction to any poleward amplification of the Atlantic ridging, and therefore cooler polar maritime incursions to be over exaggerated in the, aptly named, unreliable timeframes. in short, advisable not to let the exceptional nature of this hot spell, which looks set to last up to the weekend with only a slow cooling process over the weekend itself, over skew perceptions of what may follow it. That is why present day analysis of these AAM tools is much more grounding in terms of assessing future potential impacts, rather than proclaiming what are sometimes over speculative definitive outcomes based on numerical model forecast suggestions -without first having any knowledge and awareness of the existing momentum budgets and then looking at the computer models afterwards. Signals lead models, models do not lead signals
  48. 19 points
    Some nice pics of Ac-cas being posted and it just shows that there is instability in the air i took these not long ago say half hour,stunning sunset with some Ac-cas and the blood orange cirrus in the backdrop. i cannot wait for some action and it wont be long now and i am looking forward to all the pics,clips etc through the next several days,as always with storms they are hard to predict and not everyone will get them but them that do will have a good show no doubt
  49. 19 points
    Yet another model first. A mean 1PM London temperature over 30C at D7!!! From a model that was 5C below the maximum yesterday!
  50. 19 points
    Impressive lightning from a video my wife took in our back garden last night. Yesterday's storms were the most spectacular I've seen here for a few years. We also had numerous power dips after the cg strikes
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