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@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

so 36.3 today unless theres any final updates - A sort of halfway house of the extreme heat forecasts & the 'not so hot ones' - All in all a fair reflection as the cloud edged in- I think heathrow would have been 37/38 otherwise- Theres always tomorrow where we come from a higher starting point !! As was mentioned above UKMO 144 presents a possible spack reload from the SE which would bring the furnace back as the trough sinks west of the UK- interesting !

36.3’C at Heathrow currently. Hats everywhere can rest easy

From this to this in 20 minutes:

That's killed it then.:)

Would like to congratulate the Midlands, North and North West for next week and get it in early - Lololol Only got to 91f here today and clouded over with Virga now so at least something to look at but not the drizzle experience from our neighbours in Surrey. Horrible hot evening and night to come not a breath of wind and literally no air its awful

Afternoon all A really crazy few days of modelling coming up for the southern half - a bit more straightforward, fairly decent summery weather for the north, apart from a shower or two! Some thoughts: First, because of the uncertainty over cloud and rain, it's going to be nearly impossible to predict maximums beyond 24 hours. There's little precedent in modelling for this set-up - maybe September 2016 is the closest (which produced a 34C). The trouble is, Arome's ability to predict temperatures is not so good when cloud is around I feel, and while Arpege is great at frontal systems, I don't think it performs that well at convection coming from the east. It will be interesting to see how the HIRLAM does, as it's pretty good on easterlies in winter, though this is probably a totally new ball game. The maximum figure, in my opinion, could be anywhere between 30 and 35C on each day, and perhaps up to 37C tomorrow / Tuesday if the cloud forecast is completely wrong. Dare I say it - the Met Office might possibly be the best source in this set-up

The blob over Leicester, not a lot reaching the ground.

Hmm that's interesting That set-up reminds me of a couple of famous past thunderstorm events, July 1923 July 1925

Met Office country wide warning for thunderstorms (Monday 00:00 - 23:59) Writeup: Areas of thunderstorms are increasingly likely to develop over the south of the UK or nearby continent late in the weekend or early next week, and will generally track north or north-westwards, potentially affecting all parts of the UK at some points during this period. Whilst the most intense thunderstorms, in some instances associated with large hail, will most probably be those triggered by the high temperatures of the day over England and Wales, other areas of storms producing heavy rainfall and frequent lightning could reach further north at times over Scotland and Northern Ireland. These could occur at any time of the day. Of the area highlighted, at present the west of Northern Ireland and west of Scotland seem less likely to be affected than other areas, but still could not be ruled out. Where the storms occur, rainfall totals of 30-40 mm could fall in an hour, with some locations potentially receiving 60-80 mm in 3 hours, although these will be fairly isolated.

Morning all Stormy runs being churned out now on a daily basis - will it actually happen though is the question? Snapshots of the latest UKV: Tuesday 21:00 to Wednesday 03:00

With what could be the most thundery spell of the season upcoming I think now is a good time to start a shiny new thread. A little early to go into too much detail on what will happen but some models are bringing in the risk of storms from as early as tomorrow night. There then looks to be a few days where hot, humid air residing over at least the southern half of England and Wales could lead to numerous rounds of thunderstorm activity. This could spread further north at times. Both homegrown and imported storms are a possibility, and with the magnitude of CAPE being forecast some of the storms could be quite spectacular. The old thread is here If you want to talk about a lack of storms then the No Storms Club is still open for business. Keep on chatting

The GFS looks kind of in line with general thoughts regarding a breakdown midweek before building the Azores high towards the U.K. Goodness knows what the UKMO is up to, potentially setting up to reload the extreme heat over Spain by cutting off the thundery circulation that will bring the interest over the next few days.

I will be starting a new thread tomorrow morning to take us into what looks like a storm fest for the weekend and next week. Let's hope it comes of.

WOW Tamara, you are a legend!..as for the GEFS 6z mean, sure there’s a stutter mid range but generally speaking this is light years better than July..apart from July 31st that is!..enjoy all the heat, sunshine and thunderstorms blah blah in the meantime!

Once this current crud clears through there might be a bit of stormy fun later - hopefully a walk up my local hill will be required. This looks tasty for 17:00. Convective Weather WWW.CONVECTIVEWEATHER.CO.UK Forecasting thunderstorms and severe convective weather across the British Isles and Ireland for up to the next 5 days. One to keep an eye on for our W/SW storm lovers especially. Also got excited about these blanket warnings for next week...then read West of Scotland is least likely to see anything. More than likely one for our NE/E/SE members! @Kirkcaldy Weather

Just been out for a post-BBQ wander and I have to say, it's a lovely dusk sky out there, with trains of Ac Cas, towering nicely in spots and looking great against the orange western skies. There are some interesting looking showers coming out of France, seemingly along the same train of instability I'm seeing. I would say some very lucky spots might get a CG or two out of these through the night hours.

So on the basis of this evening's ECM, adding 2-4C to raw values (today's max was 3.3C up on raw max for example), this is what could be expected as a UK maximum in the coming days *IF* it is right. (Not far off those outlandish predictions of last weekend!) Sat: 35-37 Sun: 35-37 Mon: 35-37 (all these three days have a raw 33 somewhere) Tues: 33-35 Wed: 33-35 Thursday and Friday may scrape a 30 in the far SE, but after that it's over. If I were to take a punt at temperatures being at the lower or upper end of the ranges given, I'd go for the lower end - I have a feeling the ECM predictions match up better with reality when there's more cloud around. A further note (northerners look away...), the heat is not that localized in the next three days - if you're inside an area from Exeter to Birmingham across to Norwich down to Kent, you'll probably see 30C based on ECM predictions on each of these days. But as I mentioned earlier ... with cloud around, a really good temperature prediction may not be possible until each morning, lots of cloud will kill it, no cloud will see it soar - EDIT @Mapantz post above is a case in point of what too much cloud will do!

Aye, it's gone awfully clammy just now, hasn't it? God, I'll be hurling my teddies, rattles and Stickle Bricks out the window if (when?) I don't see any thunderstorms next week!

UKMO 12z on the other hand maybe bringing something a bit warmer again? T144:

Looking towards the last third of August, to be sure there are some very good signs from the GEFS 6z!..in the meantime, a significantly better update from Exeter today compared to previous days..but they were preety good to!

Hopefully with a Country wide Red warning.. then Purple Warning.. then website crashes.

You will be surprised when you see the 12-2 maximas we will surpassing 35c by then. Max temp today around 5-530 pm

Why do people get so hung up on cloud cover predictions? They ate often very inaccurate at even close range. @Alderc you should know that as you were not expecting much sun yesterday and did quite well.

Probably won't come off but still nice to look at

Could be the hottest 5 days on record by an absolute mile of this happens. 36c plus for 5 days straight is mind blowing really.

To be utterly honest I like mid-20s and that'll do me. The veg garden grows well in that. I know some do like it hot, but not for me I'm afraid.

This sustained heat is going to be trouble for a number of people with resputaory problems including myself, stay safe everyone and hopefully we'll get some decent storms next week to cool things off.

Single bolt of lightning and booming thunder over Northampton about 15mins ago. It’s woken the town up. No more than that though.

I thought this might be of interest in the, what seems like, perennial discussion about the Heathrow temperature readings

Nice sunset from Southampton just now

I see these next few days as a learning process with the models. We've seen plenty on how the perform with a straightforward plume, but how do they perform with a complex heat low to the south? It will be very interesting to look back at the end of this week. ECM, UKMO, fairly consistent so far aside a couple of wobbles at the start of the week, will they beat all again?

GFS kicks the heat away by Wednesday - so if heat isn’t your thing, 4 days to go. After that a few cooler days before high pressure returns for the weekend and starts to warm things back up into the 25-28c range. Much more comfortable!

Today is the hottest recorded August 7th in the UK, previous record set in 1975 at 34c in Bromley, smashed it by over 2c. I bet in the coming days more daily records will fall.

If that wind would just die down it would be a decent day here even though the cloud hasn't melted away as I thought it would. Temperature sitting between 22/23c and gusts between 2 and 9km/hr. At least it's dry I suppose. Spoke to a client earlier who is down near Laurencekirk and he had wall to wall sunshine, and it does look to be brighter to the south. Oh well, it'll soon be gin o'clock and I'll be on holiday for the next two weeks so fingers crossed for decent weather in that time.

Some nice convection to my west.

Guess who thought it'd be a smart idea to wear shorts and t-shirt as it was fine when I left the house and guess who regretting that now as the rains started DO'H

There is jo need to panic re high temps. The hourly increase between 10-2 is about 2/2.5c For example we were 23.2 at 10 its already 24.9 here +1.7 in 35 mins.. Top outs for 10am were ~ 25c. That gives us a projected temp for somewhere like heathrow as 33-34c at 2pm. 4 hours post that to get 3-4 degrees is entirely realistic. First target is 30c at 12pm..... Thanks

Great looking run there Mr.Frost! As said before, as the heatwave goes on the more unstable things get, especially from Monday onwards, good chance of evening storms kicking off in many different parts of the country and rumbling away into the overnight hours. Should be a pretty interesting spell coming up now!

Good to have summer back. Max of 22c with bountiful sunshine and a decent enough breeze sufficient to keep all of the flies away whilst working outside. Gorgeous sunset as well, perfect backdrop for the evening walk with friends.

Chaotic UKV run here:

A difference between a front and a trough is that on a front the dewpoint will fall, not necessarily so on a trough, indeed quite often it does not

24c here with partly cloudy skies, very warm for the East Neuk. No sea breeze the wind is SWly!

Not even into the weekend yet and we’re already seeing small showers develop when it was initially looking to be fairly settled for today. I have a good feeling next week will be spectacular for thunderstorms.

Yep spotted this to my SW.

The dynamics compared to last week are different, in fact there was a fairly sustained southerly breeze last week, which quickly dried the air at the surface out. This allows temperatures to rise quicker. Obviously today we have very light winds so a slower rise during the morning isn’t a surprise. GFS op on the 06z has 34c for central London, actually given the set up I think London will be the top spot (Kew Gardens or St James park) and I will still go for 36c today. Stronger winds tend to push the hottest temperatures towards the north/west of London and areas north of that (Oxford/Cambridge corridor for instance). More model related - Euros still fairly consistent in trying to break the heat down mid-week with low pressure trying to lift northwards. However following it does seem that the Azores high could build back in from the west again to bring more settled conditions after the potential fireworks next week.

A fair few small showers dotted around in the Southwest over Devon and to the S in the Channel. The Hirlam has been onto these for over a day! Be interesting to see what they do as they head over the country.

The 2nd half of August 1984 was surprisingly hot. However lets take the temperatures in London since thats within the area that the heatwave will really hit hard: August 1984 had 5 days above 27c in London (and only 0.5mm of rain, so dry for sure!) The forecast is for London to have 5 days above 32c...in a row...and quite possibly end up with nearly 5 days above 35c! They are worlds apart at least in terms of heat intensity. Really, the only comparisons that compare for the this upcoming 7 day period in terms of peak heat intensity is probably August 1911, June/July of 1976, maybe August 1990, August 2003 and maybe July 2006. I