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The first and most important thing to say is to enjoy the spoils of some excellent weather in the 7 to 10 day period. After a warm week ahead, it could feel quite tropical by the Bank Holiday weekend with hot sunshine for many and some thundery downpours for some....then clearing to let hot sunshine out again. Rinse and repeat for a few days The last post gave some background as to how the early season warm spells have evolved since mid April. The highlighted sections of the above extracts from that post last week then went on to try to anticipate a likely crossroads ahead. This crossroads now broken down into basic suggested pathway scenarios : Changing seasonal wavelengths from Spring to Summer > leading to either, Low atmospheric angular momentum retrogression of the wavelength - North Atlantic/Greenland ridge and downstream trough or, High(er) angular momentum greater retention of downstream Scandinavian/European ridging and a troughing profile in the Atlantic to our west or, There is actually a third scenario that involves a lapse around the 12 to 15 day period into the Option 1 but a bounce (and likely a sustained cyclical bounce) back to Option 2 thereafter. That is I freely admit, covering all options *and sounding like a lot of back covering on her part* but two things here: The aim is, and has never been to give long range predictive forecasts - there are plenty of guru's around who like to do that anyway without adding any more. Secondly, the balance of factors, as I see them, are very finely balanced, so it seems eminently sensible to pitch any summary suggestions to embrace all the spectre of possibilities within that envelope. So I have my own little ensemble suite most of the time, which seems to work for me anyway Speaking of ensembles, NWP has indeed started to take the suggested pathways under the radar as we start the new week. The retrogression spectre started to appear in some low resolution GFS output late last week and now the EPS clusters have started to pick up on this signal. However, the background signals in relation to the tropics, extra tropics and subsequent consequences for atmospheric angular momentum remain uncertain. Based on some more recent historical precedence (and also a seemingly increasingly inherent longer term climate trend, but that is not for this thread) it would be easy to see start of summer and yet another collapsing angular momentum regime as somewhat predictable with a string of summers in the last 10 yrs following this same pattern.... Spring warmth leading to another indifferent cool and damp summer.... But back to basics - where are we with things this since time last week? GLAAM has slumped back below average, losing the gains of the recovery earned since mid April However, as likely commented to be the case last week, relative angular momentum tendency has been holding higher again in the present low cycle ebb than the previous low tide marks in the global wind-flow cycles of mid March and then early April. The inference of this, extrapolated longer term, is that the atmosphere is trying to resurrect itself longer term from the La Nina state that has, mostly, been in evidence for the last two years. Convection in the tropics in reflection of this, is continuing to imprint the active periodicity (recurrence) cycle of the last 90 days. As bolded in the captioned post above, what is very important as we hit June is that we see clear signals that MJO forcing wants to embrace eastward shift to the Pacific as represented by an evolution to Phases 6,7 and 8. This, as demonstration that the upcoming cycle represents a further move away from La Nina with accelerating westerly wind inertia in the atmospheric circulation sustaining the priming of downstream summer warm ridges rather than sustained lapse into downstream summer chilly trough. The deterministic tropical convection forecasts have been proving, not unusually, a bit too progressive with trying to break down amplitude of the latest cycle. There is a conceivable chance this time around that modelling may overcook -ve AAM downside, and hence any blocking in the North Atlantic and/or Greenland may be overblown. Either that, or of it does verify, it does not sustain. Just this side of the Spring/Summer wavelength changes, in the short term the recent fall back of AAM has done no harm at all. Indeed, the upstream deceleration of the jet has/is helping our downstream ridge hold sway with a moribund Atlantic. The deceleration and amplification of the jet upstream in the Pacific clearly represented here by the -ve mountain torque over Asia - with the consequent vacuum created to fill as momentum is lost from atmospheric wind-flows Such a negative AAM regime, however, not recovering as we arrive at imminent changing seasonal wavelengths also assists further retrogression of the longwave pattern and is not desirable longer term. So its important that momentum upstream has some impetus heading into the new month so that any retrogressed ridge to the W or NW (should it evolve) is shunted back east by the jet stream increasing from upstream and as a consequence LP being re-set in the Atlantic. This scenario would suggest a pre-cursor to some further, sustained warmth into the meat and bones of official summer - even if the initial burst of momemtum flattens the ridging initially and allows a (likely brief) more unsettled westerly pattern for a time. Some of our best summers have displayed this sequence of events in early season, so the retrogression scenario of the extended period, should it come about, should not be treated as "summer is over before its officially begun" . It could well prove to be the opposite. On that basis, the present and upcoming spell of weather may well be just a taste of what is to come. So best not fret, just yet anyway, about the new month (and new season) breaking the weather down - it might not be for too long if it does happen Have a lovely week and Bank Holiday weekend

Got this: but now it’s kinda stopped

A stunning end to ECM the high rebuilds and the warmth is spreading across Europe Long may it continue

In a nutshell for this morning, if an endless plume is not your thing, Look away now! Absolute convective paradise for the storm lovers, pretty much right throughout the entire run. What a year this could be shaping up to be, both for coldies earlier in March and for the thunderheads! Or even better if you’re like me and do both!

looking at the output, I'd rather plump for us southerners baking by day and looking Channelwards for elevated storms and multicell clusters and then hear next morning everyone north of Brum moaning because of the detritus and clagg left over from said imports whilst we bake again down south..with a hint of rinse and a dose of repeat ..you know it makes sense!

Phew what a scorcher the Ecm 12z turns into and it's not even summer until T+252 hours..sensational charts for spring, especially when the winds go SEly / Sly!?️..very continental with plenty of very warm / hot sunny BBQ weather on this run!..a risk of T-storms at times too?️

This mornings runs....WOW!! Growing support for a plume into the bank holiday. I mean look at this ridiculous ECM 168 chart today: http://www.meteociel.fr/modeles/ecmwf/runs/2018052100/ECM0-168.GIF?21-12 Nearly the entire UK bathed in +12c uppers, touching +14c in places. Unreal for late May, and could be the third very hot spell of weather for 2018 already, and we're not even in the summer months yet. Superb.

the London cell (closer than it looked!)

ECM ensemble mean at T168 following largely the op with the orientation of the high: Less of the retrogression option, more leaving high pressure over us and to the east. Good set of runs, I'd say, would be interested to see the clusters, T240: As others have said further up the thread, the retrogression option had been increasing on ECM ensemble runs, if the 12z is a move back away from that it is good news.

It would be great to have the storms at night and hot, dry and sunny days..and the set up the Ecm 12z is showing would mean some would get that while others wouldn't but really it's just wonderful not to see any cool unsettled atlantic dross and instead an anticyclonic / continental combo with sizzling sun and a risk of storms..win win for the majority!

To be honest the surface chart looks very possible given the five day anomaly you posted, the ridge extension from the Atlantic into northern Europe with a cut off area of low heights towards Portugal. A generally easterly set up which at this time of year will be warm (or very warm in western areas). That low will be able to push some very warm or hot air northwards over France which could reach the UK which is what the models are suggesting for the Bank holiday weekend. The extended range still looks dry regardless, it just seems to be a question of how far west the high will drift after the bank holiday. I always feel sceptical of these large and clean retrogression patterns, especially as we have an area of low pressure than will continue to want to push hot air into central and northern Europe and as such mitigate any attempts to develop a deep trough over Scandinavia. So further on I suspect heights will probably remain close to the north of the UK though the temperatures may drop from the possible highs this coming weekend back towards the levels we are seeing now (High teens/low twenties).

Yes, what a fantastic post by my Sussex Girl neighbour Tamara. Certainly take what we have now and enjoy. What wonderful weather here in Cheshire. Just timed my Blighty break at the right time. Must be 23c and the Cheshire countryside looks stunning and ever so green.Pint or two this evening in one of my old watering Holes, the lovely "The Bells of Peover " pub ( below ). C

Today marks the transition to the next phase of this fine spell of weather (not forgetting that this hasn't, and isn't the case, in N. Ireland and north west Scotland). as the amplifying north east of the Atlantic ridge disrupts the main trough and forges a corridor to the Scandinavian high pressure. This essentially sets the pattern for the next few days and through the holiday weekend with high pressure to the north and north east dominating proceedings and with an unstable low pressure area to the south an easterly regime over the UK is set in motion with the Atlantic trough relegated to the west by the aforementioned corridor. The detail for the next few days. Today - The front and band of rain is still affecting N. Ireland ans western Scotland and will continue to do so through the day and evening with some heavy pulses traveling along it whilst elsewhere after a clear night another warm, very warm, day beckons once fog and low cloud has receded from eastern coastal areas although it will still be a tad cooler here. But cloud will bubble up in central southern and western areas that could lead to isolated thunderstorms. By Tuesday there is a new high cell north of Scotland where the decaying front is still lingering albeit the rain has died out but temps around the region remain depressed Elsewhere Another very warm sunny day with again the chance of thunderstorms in the south. The usual caveat vis temps along coasts, particularly the east coast with the onshore wind. By Wednesday the center of the high has shifted northeast and whilst warm and sunny conditions continue to dominate in many areas with again the risk of thundery outbreaks, temps in northern Scotland and eastern coastal areas decidedly cooler in comparison. On Thursday the aforementioned 'corridor' to the west is in full swing and with the low pressure to the south pushing north a trough does likewise bringing more concentrated convective outbreaks to the south and west in the freshening easterly wind. A similar story on Friday vis the risk of thundery outbreaks in the south and again another warm day but with a definite westerly bias and cooler in the eastern half of the country with possible some low cloud and mist along the coast. The rainfall distribution reflects the above - hopefuly

finally got my pc sorted out after a burn out of my hard drive(my fault),was cleaning it out and inserted my front fan the wrong way and was blowing the warm air out instead of sucking cool air in,anyway... I don't usaully post at this time of the year as i am a coldie fan but i am loving these charts and weather that we are getting at the moment,what!!!,two may bank holidays with sunshine and warmth,you don't see that every year,ok there might be some hickups regarding some storms especially in the south but after a long cold winter it's payback and we are still not in summer yet latest from cpc show a nice continental drift from the E/SE with HP to our north and at this time of year could/should import some very warm weather from the continent 6-10 and 8-14 day outlook Weerplaza temps,dewpoints and w/direction ECMWF more bullish on touching 30c and you can see the E/SE wind direction gfs temps and wind direction ECM and GFS mean at 144 hrs and 240 hrs all looking good to me and may it continue,with the added thunderstorms too?️

Absolutely sensational. If verified, we will be chasing a monthly temperature record yet again (32.8C). Also the 2nd warmest May on record. However... all extreme patterns have this same feature... they are always extremely close to not verifying

Thunderstorm here in SE London - am on a packed and sweltering train. The last flash and bang made most people on the train jump, lol!!! edit - Train is at a standstill and we just had another extremely close CG and deafening peel. Awesome

Been a while since I've written in this thread, or indeed anywhere on the forum, such has the weather had little of note worth talking about. But as it looks like there is a risk of storms, albeit isolated, most days in the south and west this week, I'm back and with a Netweather Thunderstorm Outlook for Monday. Storm & Convective Forecast Issued 2018-05-20 21:46:39 Valid: 21/05/2018 0600Z - 22/05/2018 0600Z THUNDERSTORM OUTLOOK - DAY 1 (MONDAY 21ST MAY 2018) Synopsis A broad upper trough covers the far N Atlantic with an upper ridge centred over Scandinavia/Baltic Sea. A weak upper low with cooler air aloft over near continent will drift westward across England and Wales in next 24 hours which, combined with diurnal heating of increasingly moist surface flow, will be the catalyst for isolated thunderstorms to develop across southern and western areas on Monday. … S, CENTRAL AND W ENGLAND + WALES … Weak and diffuse upper low/trough drifting west across Sern Britain will introduce subtle cooling aloft in the mid-levels atop moistening weak low-mid level flow from the east overnight and through Monday … this will steepen lapse rates … initially bringing some weak mid-level instability to E/SE England early Monday, which may produce spotty showers. Diurnal surface heating will then increase surface instability into the afternoon, as sunshine warms a moistening airmass (dew points in low-mid teens C) beneath mid-levels cooling from the east, resulting in around 500-1000 j/kg CAPE. This environment should promote the development of isolated thunderstorms across S England, perhaps a little more numerous across W England and E Wales – where weak surface convergence is indicated. Weak vertical shear will limit potential of severe weather from any storm to a low risk, though hail is possible given predicted CAPE and an isolated incidence of large can’t be ruled out … localised flooding may be a greater risk given slow-moving nature of any storms. Storms will generally die out after dark as heating wanes, though there is a risk of elevated instability/convection returning to the SE Monday night, which may bring isolated lightning. Forecast here as well: https://www.netweather.tv/weather-forecasts/uk/convective

Not a bad mean a fairly prolonged spell of warmth for many showers beginning to increase in the south as pressure lowers enough here to trigger some storms at times always drier in the north where pressure remains higher

As has been said above the charts for this weekend (bit far out at the moment though) are insane!!! Decent enough potential across S-UK this week for similar kinds of storms has we saw today - small, discreet but very potent! From Friday onwards though the potential skyrockets. Let’s go hope he conditions come to fruition. 5-7 days out not ideal. Cant resist sharing - terms and conditions apply! All chart grabs are 18z each day starting Friday

Fun getting hot and sweaty and soaked from torrential deluges and dodging lightening strikes..can't wait!...stunning summery model output though and hopefully plenty of dry, very warm and sunny to go with it!!!

Fantastic ecm this evening up to 144 hours!!weekend has a hot south east wind across much of the uk and humidity will be sky rocketing!!

Lovin the 06z ensembles from GFS, 850 temps rising each run. Could be a blowtorch bank holiday weekend with a thunderstorm or five before Spring is out http://www.meteociel...t=1&x=305&y=177

With every passing day, I'm getting more and more positive about the prospects of this upcoming Summer. I know weather can change so quickly, but I really have a feeling this summer will be a very memorable one. All the signs are good.

Probably the CG that hit something very close to where I live near Addiscombe (Croydon) was watering plants about 6pm and saw it out the corner of my eye, followed by a huge bang that set car alarms off. Was almost continuous thunder at one point, mostly from IC lightning, with occasional CGs, was an unexpectedly active cell thunder wise, though high based with a crap structure.

Out to D9 on ECM and high pressure is never far away

Yes, really liking the orientation of the high at T144: Really interested to see where this run goes,

Yes I think my jaw dropped when I looked at the 12z, incredible pattern. As Captain Shortwave mentioned, how many times do we see retrogression to Greenland fail due to shortwaves, if this were to happen next week then its hard to see how the hot air could be displaced. This is an impressive pattern for high summer let alone late May, what I also find interesting is that this is a very unusual pattern with low pressure persisting near Portugal/Iberia bringing up warm air from Africa. A real clash of airmasses, slack winds and hot temperatures could lead to some explosive convection. From my time analysing the best thundery breakdowns / stormy periods, its often those with cyclonic southerlies/SE'lies that deliver the goods. July 2017,2014 and June 1994 come to mind. It may be the GFS OP is on the extreme side of things but just compare today's 12z chart to Monday's... good grief. Today, maximum temperatures and CAPE, which was a decent effort down here. Next monday If this is still being forecast by Thursday I will start getting very excited. Really awesome charts for storm lovers, though to be picky SLP could do with being a bit lower.

Amazing amount of thunder in SE12 (Lee, Lewisham, Blackheath), from the smallest of light grey clouds. Blue sky all around it! Some of the thunder has been properly booming, with repeated high/low bangs over several seconds.

Lots of towers going up very rapidly to my NE/E....

The GFS keeps that 16C isotherm over the south into Monday and Tuesday. An increasingly slack and cyclonic easterly from that low to our south west. Borderline tropical with the GFS even suggesting temperatures close to 30C with the real risk of some pretty beefy thunderstorms developing with some stunning instability being predicted. The question is whether we can cleanly advect the heat towards the UK for the weekend, if it makes it to the UK then we could end May on a high.

Morning all Been away due to a family bereavement and haven't looked at a chart for 10 days or more. The last I remember was plenty of northern blocking building for later in May with heights to the north and persistent LP over Europe leading to an easterly flow and the risk of showers for southern and south western parts. As a man from Sheffield once said "that was then, this is now". The medium term analysis goes out to Thursday May 31st and starts as always with the morning's ECM output at T+240: Not a lot has changed. Heights over Scandinavia and a notable trough over Europe bring in a warm, if not very warm, SE'ly flow for many over the coming Bank Holiday but the HP retrogresses to Greenland meaning pressure drops near the British Isles and shallow Atlantic systems are edging in to the south west with a cooler NE'ly flow across the far north. Settled for now but the notion of things going downhill at speed is evident. GEM 00Z OP at the same time: Some differences to ECM. Good agreement through the weekend with the warm SE'ly but GEM takes the trough further north across the British Isles before heights rise again to the NW and NE and we end with a light easterly flow but still with a risk of showers for southern and south western areas. GFS 00Z OP at T+240: The HP doesn't retrogress as with ECM but moves back into Scandinavia and declines SE but the pressure gradient over the British Isles is very slack. Some residual LP to the south west but very much a holding pattern with showers possible but very light winds. Further into FI and HP builds to the north and north west so another dose of easterly winds before a trough develops over Scandinavia and extends SW bringing in cooler and more changeable conditions. GFS Parallel at the same time: Again, a very slack evolution with a shallow trough over the southern North Sea so showers or thunderstorms possible in southern and eastern areas. Further into FI and a strong ridge develops NE from the Azores into June keeping the weather fine and warm for most. GFS Control at the same time; Heights to the NE remains strong but the European LP has moved up into southern areas bringing in an enhanced risk of showers or storms. Further into FI and the HP and the continental LP re-orient to bring in a cooler ENE'ly flow with showers still a risk in the south. IN summary, a fine and very warm Bank Holiday weekend for many albeit with a growing risk of showers or storms for the south and south west. Into next week and a range of options on offer - ECM offers retrogression but the percentage call looks to be a slack flow which would be reasonable for most but if you do get a shower or storm it would be very slow moving and consequently could drop a lot of rain on a localised area. Absolutely no sign of Atlantic influence and while Parallel offers a nice continuation of the fine spell into June via an Azores ridge other options maintain the pattern of heights to the north and lower pressure over Europe periodically extending across southern parts of the British Isles.

Staggering ensemble too: http://www.theweatheroutlook.com/charts/gefs/gefsens850london0.png Mean touching 10c for a good number of days.

It look's like it is about to piddle down again. I love days like this, warm and sunny, then a storm in the late afternoon. MOAR PLEASE!

The garden looks awesome now the sun is back out. Everything is refreshed and green!

Toasty 12z run for Sunday/Mon/Tues/Wed!

What a remarkable 12z! If it comes off, the final 5 days of the month will average close to 20C and we'd have a genuine shot at beating the warmest May day on record, at least twice!

Ay 32° for London area, Wednesday of Whit holiday week!

Nice structure on that cell.

12z UKMO and 12z gfs has the 16c isotherm touching the south coast at 144 (Sunday). Amazing.

We are a rumbling and a rocking. . And a good sign we have mammatus. .

Right we are going under

Sun has been rather hazy at times today but still managed to top 20C. Cooler tomorrow though as more of an Easterly. Spotted a very large butterfly landing in a shrub in the back garden so rushed out to get a photo. Its colours were identical to the fence, dark green leaves and red berries so very difficult to spot.

Amazing pictures! Thanks for sharing.

Magnificent Tamara.

A few images from our bonus chase day (19th May) near Vernon Texas. A big thanks to the team for getting us in the right places at the right time.

I for one love @Tamara's posts

Regarding the D11-D15 period, we're now at 50/50 in the EC clusters between retrogression to the NW and a continuing Sceuro ridge. The trend is definitely on the up for "clear" retrogression; it was 15% yesterday morning, and 30% last night. That said, I generally look for 2/3rds support for retrogression (so say 65/70%) before really latching onto it - it seems to be one of the patterns that most easily collapses closer to T0 these days. So it's still in the pending file, and I'm still extremely open to a continuation of the continental flow of this week even into June.

The ecm this morning has us right on the edge of the plume Sunday/Monday but a word of caution. This is very dependent on the precise orientation of the low pressure just west of Iberia and the high pressure over southern Norway.. A slight variation on the analysis makes a world of difference.As it stands at the moment.

Yes the longevity of the settled conditions looks quite staggering...hard to see where a breakdown will come from! It's almost inevitable that the progression into next weekend will lead to some sort of plume scenario.