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Just worth bearing in mind how the models have been handling events just recently... ECM mean 500 hPa height anomaly day 10 ten days ago: And the initialised version: Broadly OK across the NH but a little off in the NE Pacific, but quite a way off for our corner. Way too flat with the Azores ridge and didn't capture the split flow in the NE Atlantic. A relaxation in angular momentum looks about right given tropical developments, but no where near GFS projection. I'd go closer to seasonal norm, possibly a touch below for AAM state. Expect once again the trough in our locale not to be modelled correctly in the day 10+ timeframe.

Let's hope we have plenty of these to look at come tomorrow/tomorrow night and not these i finish work at 2pm tomorrow and it's going to be touch and go and prob'y have to set strait off out again lol.

Extract from previous post copied for continuation purposes A few things posted over the last couple of weeks that offer the chance of some perspective: 1) Assumed NWP atmospheric angular momentum bias Once again, its worth repeating here that the signals lead the models, the models do not lead the signals. Since the step-change in the atmospheric circulation (sudden drop in atmospheric angular momentum) that led to the abrupt change in the weather during the last third of June from mid month heat (for many) to cool and unsettled (for all of us) low AAM bias expectation has much less relevance in terms of NWP evolution. (The previous post explained in a lot of detail why the change had come about and what the causes were). To put this into some synoptic parlance, any individual model suite operational (and even ensemble data) which has suggested any especially purposeful eastward return of the Azores ridge has risked being built around conceivably erroneous assumptions that modelling is auto-correcting from Nina-esque forcing in the Pacific. I think that repeated use of the GEFS forecasting tool for purposes of checking the progress of the Global Wind Oscillation (which is a plot representation of the flux of global windflows/ Jetstream strength and trajectory as calculated through tropical and extra tropical forcings) leads to assumptions being made that the inherent low angular momentum bias within the product is applicable at all times. As stated in previous posts, checks on consolidated actual data is required to get as accurate a perspective as possible on where the atmospheric circulation actually is, instead of using GEFS forecasted data to build in a forecast assumption that this is a 24/7 perma-default subject to persistent over-estimation of Indian Ocean tropical convection forcing. A bias does certainly exist, but its knowing the times when its bias is much less of a factor. This was also a challenge last summer which saw a low angular momentum phase during the first half of the summer due to I/O tropical forcing destructively acting on the pattern in the Pacific at a time when ENSO was transferring through into ENSO neutral > very weak La Nina later in the year The WDT site shows that the GWO was stuck in low amplitude low angular momentum Phase 2 for much of the last week The retracted Azores ridge and Western Europe trough seen up to the weekend is fully representative synoptically of this phase at this stage of the summer. So to the present and outlook: The highlighted post from two weeks back suggested we would need to see the GWO progress back up towards Phase 4 (recovery upwards of AAM) to initiate any more sustainable recovery without slipping back to a more withdrawn Azores ridge and the trough having a greater say once more. Latest modelling is inclining back to retracted ridge for next week and cooler changeable regime more widespread again. I suspect the consolidated data updating through this week will show that there has been an attempted orbit to GWO Phase 3/4 but that an intermittent tropical signal from the Indian Ocean continues to hamper efforts (for the time-being) to revert the atmosphere back closest to where we were prior to the breakdown of the mid June heatwave. This interim partial recovery, largely driven by some +AAM transport into the atmosphere c/o a +ve mountain torque across the Andes - spiking sub tropical ridging to mid latitudes over the 'wavelength' (lifespan) of this torque wave eddy (circa 5/6 days) means that the ridge extension and cut-off low this week allows the window for return of summer proper at least for southern and some central parts of the UK But. this transitory amplification aside, caution is definitely required against any on-going supposition that the models are underestimating the AAM trend over the coming week (commencing 10 July) and therefore assuming that any model forecasts for next week showing the flat pattern and the retracted Azores ridge and Icelandic low interplay are overdone. They likely are not overdone, and so expectations should be adjusted accordingly. Tropical convection forecasts are subject to uncertainty, but such uncertainty on balance still favours another cooler and more generally changeable period, until at least the mid month period. Its not a surprise to see some revision of expectations of more wholesale and wider improvement in status updates from the likes of the METO - when eastward forcing of the tropical signal continues to remain at some distance and in the absence of consensus. Supression of the I/O signal and eastward forcing would help the rossby wave pattern configure towards greater eastward progression of the Azores High (closer to what was seen mid June) and as a consequence more widespread warmer and more settled weather than the relatively brief (but highly welcome) interlude this week offers. But lets remember its not for all of us and those in the NW of the UK will see this pass by once again There is no reason not to expect a return to more widespread warmth and settled weather later this month, but until a greater modelling consensus from the tropics happens then false dawns continue to be a risk 2) Arctic heights - the stratosphere>troposphere profile In terms of anticipating hoped for improvement, we can continue to look to the profile of the layers of the atmosphere retaining low heights to the north. It has been argued that this is accentuating thermal gradients and spawning low pressure systems in terms of the cold air locked to the north and the seasonally much warmer sub tropical air to the south. - therefore hampering a seasonally warm and settled summer pattern for the greater of the UK. However, in the absence of arctic blocking, the other side of the coin is that the AzoresAtlantic ridge is prevented from amplifying further to our west to lead to greater and deeper cool air advection southwards as heights are raised across the pole, locking in the cooler spells for much longer than seen so far. Such as seen in the poorest summers of recent years such as 2007 and 2011, which were both dominated by the double whammy of low atmospheric angular momentum and anomalous arctic high pressure. From the present position of cold stratosphere/troposphere height anomaly layers, still persisting robustly as June has turned into July, it remains a much easier route back to proper summer conditions - much as the last few weeks has already demonstrated So this too, augers better for the next return of summer proper later this month. But for this to happen, the fortunes of all, and not just the south depend upon some awakening of tropical convective forcing moving eastwards, with suppression over the I/O, to enable the Jetstream to move north of the UK and Azores ridging to be stronger and more sustained into Europa - as atmospheric angular momentum returns to buoyancy.

Looking good here. Plenty of altocumulus grimsleyus.

Tricky to forecast due lots of factors involved. Once thing we should perhaps point out is that early storms across the south may not be rooted in the boundary layer. See forecast skewt for London. Further north the picture is a little different. See forecast skewt for west midlands. This does not mean that you will not get an intense storm with lots of lightning and rain fall , just that inflow is not in the boundary layer and so the likes of tornadoes would not be on the cards where storms are not based from the boundary layer. High level cloud due to high level moisture may also limit boundary based convection. Having said that there are signs that we should expect significant rain fall from storms developing across the south. The chart that has caught my attention is lightning wizards 0-2km deep convergence chart. This suggests a significant storm passes across the south of the UK with moisture converging at the outflow boundaries. Lightning wizard explanation of the chart. It shows regions of mesoscale ascent, which are sometimes more and sometimes less established than convergence of the 10 meter wind. It occasionally shows expanding rings of deep convergence when GFS blows itself up into a big convective system. Any storms forming at outflow boundaries have the ability to develop dangerous characteristics. At the moment there is little suggest this will happen, but it is worth keeping an eye on. It will also be interesting to see where any drier air aloft will be positioned ahead of the approaching cold front. Typically models move storm development eastwards and downgrade during the day before storms, only to move them slightly back west and upgrade on the day. So do not be surprised if the next couple of runs move every thing eastwards and downgrades the potential. (Similarly at 3 days out the modelling shows things too far west). Think at the very least somebody should get a good lightning show tomorrow.

Storm & Convective Forecast Issued 2017-07-05 09:30:05 Valid: 05/07/17 06z to 08/07/17 06z DAYS 1 & 2 CONVECTIVE / STORM FORECAST - 5TH/6TH JULY 2017 Synopsis Trough disruption on the southern flank of the broad cyclonic upper Wly flow across the far N Atlantic leads to an upper low to drift S and SE across western Iberia over the next 36-48 hours. As a result, the upper flow across southern UK will back more towards a Sly from the generally Wly flow of recent days, allowing an unstable plume of warm and humid air over Biscay, W France and Iberia to spread N across S England by Thursday morning. A shallow surface low over the Bay of Biscay will expand north across S England with the plume spreading north, thunderstorms are likely to develop and move N within this plume across central, S and E England from Wednesday night through Thursday, some storms perhaps bringing severe weather. Some storms are also possible along a developing cold front moving in from the west across N Wales and N England on the NW edge of the plume. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- DAY 1 CONVECTIVE FORECAST – WEDNESDAY 5TH JULY 2017 (05/07 06z to 06/07 06z) … S ENGLAND TONIGHT … Plume of warm and humid air over France on Wednesday (with wet-bulb potential temps of 18-20C) will spread north into S England in the early hours of Thursday morning, an Elevated Mixed Layer (EML) aloft originating from the Spanish Plateau atop of the warm humid airmass will create steep lapse rates which, combined with isentropic lift on the northern edge of the plume helped by subtle surface trough moving NE over Biscay, will allow development of elevated thunderstorms over N France / English Channel areas tonight – which may move inland across southern counties of England by 6am (end of this day 1 forecast). Although deep layer shear will be weak (less than 30knts) combination of forecast MLCAPE values approaching / in excess of 1000 j/kg and strengthening SWly flow aloft will allow clusters of strong elevated storms to develop and move NE – bringing a risk of hail (isolated large), torrential rainfall leading to flash-flooding and frequent cloud-to-ground lightning. A MARGINAL risk has been issued for southern counties of England for overnight period. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- DAY 2 CONVECTIVE FORECAST – THURSDAY 6TH JULY (06/07 06z to 07/07 06z) … S and CENTRAL ENGLAND, E ANGLIA … Warm and humid air (WBPTs of 16-18C) will continue to advect N and NE across southern UK on Thursday in tandem with surface low drifting NE from NW France. A few clusters of elevated thunderstorms with isolated hail, torrential rain and frequent lightning maybe ongoing in the morning from the start of the forecast across parts of central-S and SE England, these will continue NE across SE England, Midlands and East Anglia, with potential for further storms, perhaps surface-based, to develop in wake of these early elevated storms into the afternoon across Midlands, SE England and E Anglia. Model forecast skew-ts indicate that LCLs (Lifted Condensation Levels), which determine where cloud bases develop, will fall through Thursday, as surface airmass becomes increasingly moist. Also, the warm/dry nose/cap at around 850mb, which keeps convection elevated above it before then, is eroded as heights fall from the west with approach of an eastward-moving shortwave trough, so surface-based storms may develop into the afternoon as lift increases with approach of shortwave trough. Airmass will be rather unstable across S England … Elevated Mixed Layer (EML) will create steep lapse rates atop of hot and humid surface airmass characterised by dew points in the high teens and precipitable water (PWAT) values of 33-36mm) … which is forecast to yield around 1000-1500 j/kg CAPE. A shallow area of low pressure at the surface moving NE across SE England in the afternoon will create surface convergence which, combined with increasing large scale ascent of approaching shortwave, will create forced ascent of unstable surface airmass. As a result, organised surface-based thunderstorms may develop within an environment of increasing deep layer (0-6km) shear in the order 30-40knts … as increasing SWly flow aloft and backed winds towards the surface as upper shortwave approaches from the west. Clusters of storms, perhaps one or two with rotating updrafts / mesocyclones, may pose a risk of all severe hazards ... large hail (1-2 inches in diameter) and torrential rainfall leading to flash-flooding are the main threats – though for now any such threat should be considered isolated / SLIGHT risk. Also storms maybe accompanied by strong convective wind gusts and frequent cloud-to-ground lightning ... an isolated tornado cannot be ruled out, with any surface-based storm that forms along a wind convergence boundary - where storm-relative helicity will be maximised. … E IRELAND, N WALES, N MIDLANDS, N ENGLAND … A cold front developing over Ireland in the morning on the NW edge of the plume spreading into Sern UK will arrive across the above central areas of the UK in the afternoon. Lift by this front of warm/moist air to the SE of front is forecast to support the development of a band of heavy showers and thunderstorms across the above areas in the afternoon/early evening – before this activity clears east into the N Sea. Hail, flash-flooding, strong winds gust and frequent lightning may accompany these storms, so have issued a MARGINAL for these areas. Issued by: Nick Finnis http://www.netweather.tv/index.cgi?action=convective;sess=

Evening all, I saw an identical example of these clouds over Surrey this afternoon. I thought it to be a good indicator of instability and here I am catching up on hundreds of posts! http://earthsky.org/earth/kelvin-helmholzt-clouds

People need to settle down a bit and wait for tomorrow(the actual day) to see what crops up,it is alway's a nowcast situation when it comes to storms and none of the models or forecasts will be bang on correct,it is the same with the warning areas and can shift either west or east of the forecasted warning areas so sit tight... and happy hunting tomorrow

Everyone tomorrow on this forum about storms (or lack of)

Yes it certainly looks similar it's nice to see 2 models take this route even if it is out at the realms of FI

Could turn into a very hot mid July if this is close to the mark.

does anyone have anything to say on topic?.......Ants, whilst fascinating creatures and helpful to mankind in numerous ways don't actually aid thunderstorm/convective development or discussion......lol latest model runs now starting to roll out, hi-res NW due out in an hour or so, how will they handle what is now basically nowcasting?

FOR IMEDIATE BROADCAST ****As of 16.31 severe flying ant warning issued, take cover immediately****

Yes Mark it just goes to show that even though next week is being talked about as cool and changeable / unsettled, the Ecm 12z offers a silver lining..The Azores high might have something to say about next week after all.

Severe thunderstorms possible tomorrow http://www.convectiveweather.co.uk/forecast.php?date=2017-07-06

First signs of some AcCas drifting in - nothing record breaking but tentative signs nonetheless

The Ecm 12z shows the Azores high ridging in again after next midweek following an unsettled few days..whether it's right or wrong it's what's showing. looks better than the 00z in the same timeframe..and a happy ending!

Not the best picture in the world I know, but there are strong convective cloudscapes forming over to my East... Towards Cheshire.

This time last week, this week looked pretty abysmal at times. Fortunes change very quickly so I highly doubt it will be poor for two weeks, especially every day.

The SR has a bit of a convective spin-up issue at the moment, in that it's not picking up on developing convective stuff during the first 3-6 hours of a run very well. So this means the most recent run as and when stuff is happening isn't picking everything up it might. We're working on a fix for that currently, but prior runs up to recent convective events (on the viewer use the view previous run button on the day of the event) have generally done very well.

I've normally championed the NW hi-res model, but on the past couple of convective episodes, it has been hopeless, so yes, not just a pinch of salt, but a whole salt cellar........now casting and radar watching later on this evening will be the name of the game

My thoughts on the positive AO, which after all is merely an index of pressure distribution, is that currently it is not doing us any favours, albeit not disastrously so. I assume the argument is that it locks the cold air safely away to the north but this only really applies providing the interface between the cold/warm air, and thus the strongest thermal gradient, is not too far south. Currently it would appear that it is. Anyway a quick look at this evening's anomalies which tend to agree with this and the latest det. interpretations. There is pretty good agreement in the 6-10 range with the key as far as we are concerned the continuing low pressure over N.Canada/NW Greenland with associated ridge SE over Iceland and the ridge in central North America This then maintains a fairly strong upper westerly flow over the central Atlantic curtailing any permanent movement north of the Azores high pressure. This does not mean that Azores will not influence our weather but is just signalling the usual phasing of the warm and cold air and thus intermittent periods of unsettled weather with the usual north south bias in these situations. The det. runs will of course determine the detail of this in due course. Temps will be tending below average. No significant change in the later period

I'll settle for the ant ,at least it clutches straws ..

So ECM more or less follows GEM... Shame it's at such unreliable range but in general it highlights how simply having a low consolidate near the climatological norm position of around Iceland can really help us out during a period of positive summer AO.

LOl local forecast going nuts and we have storms from 15:00 to 17:00. I'll stick with isolated and damn lucky if you have one.

meanwhile at Bedford HQ above my house.

Here is Met Office's view on tomorrow although Updated: 13:25 on Wed 5 Jul 2017 BST,i don't know when the next update is http://www.metoffice.gov.uk/public/weather/forecast checklist as follows camera formatted and in-car charger:check tripod:check fuel tank full:check drinks and snacks:check no kids and partner yey:check

The south-east is again blessed with the warmest / hottest sunniest weather today, tomorrow, friday and probably saturday although tomorrow indicates some scattered but severe T-storms.

Tough one. I personally think the early afternoon is more favourable - at least for my area (will be in london tomorrow working during the day). However, I am hoping that the storms hold off until I get home in the evening when I have more time to admire them (plus, I just love home storms. There's just something about seeing the place in a totally different atmosphere to what you're so used to that's just incredible and awe inspiring. I'm like a kid in a sweet shop with home storms!).

does it matter if the gfs is overdoing the cape values? theyll still be high and thunderstorms are expected for some, heavy downpours for some others and with the +15c upper isotherm nudging into southern areas let alone most of the uk being under +10 . 27c widespread in any sun before (or after) we get a storm or shower is again perfectly possible. downtalking what we are likely to get, doesnt make it happen you know

06z GFS being an excellent case in point. Little disturbances in the flow dropping to our west driving warmer air poleward. With the +AO signal, a flat Azores ridge is not straightforward and subject to the type of variation we are seeing at T0, T96 and possible again at day 10.

Good luck all, started my new job today couldn't have picked a better week to start. Some of the charts coming out for tonight and tomorrow are astonishing

Thanks for the update Tamara I retain the suspicion that the atmospheric state is not far enough from neutral to lock in a retracted Azores ridge for much time so will continue to watch for weak ridges producing a warm/very warm day or two, but must concede that I did not adjust my AAM corrections down fast enough after the recent underestimated ascending period. So next week does look likely to be changeable with temps mostly varying around average or a little below - but still the chance of an appreciably warmer day or two at least in the south. I do however still view the GEFS week 2 drop of AAM as unrealistically large, as barely a day has been seen in the past year in which it wasn't overdone. So too much drive toward establishing or maintaining a cool and unsettled regime. Good thing is, most on here don't take GFS very seriously at that range anyway

Fine and sunny start here which is a good sign considering the forecast of cloud and showers this morning. The models perhaps hinting that we could squeeze a very warm Sunday as well out of this along with another chance of thunderstorms.

Like i said in the Past ' All computer models you are dwelling on' even last week it was looking grim and droom ' the last 2 days here have been great ' even Hotter here 2day and even Thursday ' stick to Met Office .. Not ECM -GFS - ANNADIN IS GOOD FOR YAH

Interesting !!!

Here in Slovakia there's a great light show happening to my east. Frequent lightning high in the atmosphere but with very little thunder.

My wifi has gone- so my posts may be very limited until further notice, but there is some lovely Altocumulus castellanus!

Evening all A few towers going up directly overhead with dark bases, but not expecting anything here this evening

One of my main reasons that I just couldn't live up north as much as I like it up there it's nice to have a few weeks of high 20s&30s to know summers paid a visit each year, poor Scotland

Well isn't that a beautiful sky!

Flying ants here today are horrendous... never seen so many

Tell you what, the southeasterners on here in the model thread complain about their lack of cold/snow in the winter but they certainly cannot complain about their summers! It got so hot today down at the beach that we had to come off. Got home to the cottage and walked straight into a cold shower! Really sad that presently it is a tale of two halves weatherwise in the UK. Probably go off with a bang tomorrow though but I find that pretty enjoyable too!

Thanks for that, just looked outside and it's antmageddon out there. Not looking forward to leaving work now!

first patches of Cirrocumulus drifting up from the south west....a good sign....I'll be watching for Ac Cas from early evening onwards I reckon

Hi all. I've cleared the day of work tomorrow, charging the cameras & fueled the van, all ready for my first chase of 2017 WOO-HOO. Anyone else in the south planning on chasing

12C? That's awful! Get yourself down here, gorgeous weather.

BBC forecast calling for an early start to storms on Thursday, the far South affected by 6am. By afternoon the focus has shifted North and East with the South drier in hot sunshine.Perhaps a second round overnight Thursday into Friday for the SE.