Ben Sainsbury

39.7C Cambridgeshire - Mon 18th July.

For what its worth NetWx-MR also going for 40C at T168, only at midday too!

UKMO would be hot post T168, probably a shy cooler than GFS though. With the ICON, GFS & UKMO all going for a plume of sorts, then I'm not sure I'd give the GEM the time of day... unless the ECM backs it that is!

This is one of the rare situations CoxR where since we have never experienced this here in the UK in real world that we wouldn't know what temperature this would correspond to in reality. Just looking closer at this GFS 6z run, the *28C* 850hPa isotherm just about skims Kent, with 27C more widely. Utterly remarkable.

At a glance, GEFS 12z looks better than 6z and 0z respectively. Less of a dip next Thurs-Friday and then more runs reach 20C at 850hPa from Saturday.

You're correct there! Good to see Dan back doing the forecasts, not that Chris was bad at all! Also NMM is known to overdo CAPE amounts, most other models are more on the conservative side in line with Dan's forecast.

If I really had to try and nail down a location for tomorrow, I think a region between Wrexham, Liverpool, Manchester towards Blackpool might do best.

To add on from Paul, in basic terms higher cloud tops would be indicative of a stronger updraft - so possibly more instability. Also, higher cloud tops might indicate a greater risk of hail/lightning but that is also dependent on a number of other factors. For low cloud base, this can help determine whether thunderstorms are likely to be surface based or elevated. In technical terms, low cloud bases can support funnel cloud/tornadic development, but that is also assuming other conditions are favourable.

The models have an awful grasp on the synoptics tomorrow, with many still in disagreement there's every chance you still might see something.

Two regions of interest to me, one across Wales, W Mids into NW England. Another across CS/SE England and towards Essex. The latter of the two probably have a higher risk of storms becoming electrified.

Thursday looking particularly interesting on UKV 9z. NMM also going for some absurdly high CAPE values but more across Central areas, but as we know NMM often overdoes these.

Just wanted to add @Paul that the addition of ML & MUCAPE charts have been brilliant since release, as a storm enthusiast they're extremely helpful, so thanks for that!

As @East_England_Stormchaser91 has said, potential for some decent activity later this week due to a combination of strong surface heating and cooling upper levels due to an upper trough approaching from the south on Thursday, before merging with another upper trough moving in from the NW on Friday. Currently thinking is risk of one or two surface based storms late afternoon/evening on Thursday as CS England into Midlands, 500-600 J/Kg of CAPE and some directional shear so some organisation of cells for a time. Friday looks the greater and more widespread risk, although some concern over cloud cover. Assuming we see enough sunny spells, then could see instability reach 800-900J/Kg in places again with some directional shear, therefore Midlands, N England and East Anglia at risk of seeing a few fairly active surface-based storms during the afternoon. That's taking the models at face value currently and so details are expected to change in the coming days. If we see a slight delay in the arrival of the upper troughs then a more widespread area may be at risk on Friday.

Experienced this when I was in Brighton during the active overnight event a month or so ago. Quite a bizarre feeling and unsurprising as you're still in the high Theta-W airmass.

System in SE now classified as an MCS, with a large & impressive squall line and possiblility of an embedded supercell somewhere in there.

Several people screaming 'Kent Clipper' and yet again no evidence of a Kent Clipper! This year has been a remarkable year so far for elevated thunderstorms coming up from the south. I'd imagine large CAPE being released now at the boundary between the high Theta-W airmass and the trough/front moving down from the north. Judging by the radar, quick upscale into an MCS looks quite likely atm as it clears ENE.

No storms today... some mid-level instability however the atmosphere is very dry and nothing to trigger significant convection so a bit of AcCas but that's about it. Tomorrow, looks mostly confined to the SE for anything decent, though there's still an awful lot of uncertainty regarding where storms will initiate etc. Possibly some embedded thunder within the rain band over western/central areas tomorrow.

UKV 6z quite similar to NMM, some decent instability and strong DLS across the SE. Could be some very electrically active cells initiating for a time tomorrow evening as they clear ENE into the North Sea and Mainland Europe.

Yep, ECM remains the most interesting of all the models for convective activity.

GFS only shows surface-based CAPE, that'll be why! Unfortunately, surface-based storms in this environment are often more exciting as they can become severe, however that isn't looking as likely as it was a few days ago. Looking at a Skew-T, what is more likely is if storms can initiate from 800hPa (elevated thunderstorms) then I would expect large CAPE release with very frequent lightning, but even this remains to be seen yet.

Both ICON & GFS 18z have both slowed the clearance of the heat on Saturday compared to their 12z counterparts. GFS in particular is quite an improvement, with the 24C isotherm close to the S coast at 2000 on Saturday!

Just having a scan through the models today and for my location near Benson, majority of the models had a max temp here of 21C including GFS, ECM & UKMO whereas UKV has 23C. Currently 22.5C and rising, already goes to show the models underestimating max temps by a degree or two.

ARPEGE 6z will likely be an improvement for maximum temperatures on Friday too compared to the 0z run. 0z run had widespread low 30s, peaking at 34. 6z run has 850s at least 2 degrees warmer across the SW early on Friday, so maybe seeing 35C on this run? Unfortunately cannot see past T72.

You're not wrong and I do agree to some extent, but surely this logic should be applied to all of the models because they all begin their runs with the same observational data so should have somewhat similar errors (obviously I know the model physics differ slightly). But as I said in my previous comment, the UKV having the highest resolution means it should still perform slightly better regarding the peak max temps for this Friday (whether that be 32C or 36C), regardless of whether one of the variables is slightly off or not. Maybe saying it would be a 'disaster' is a bit far, but this brief hot blast will definitely give us a good insight into how we should perceive the models (& UKV in particular) going forward when we are expecting extreme heat.

Definitely right on the upper end of the models, ARPEGE reaches 33C maybe 34C, GFS not far off now either. Logically, the UKV is by far the highest resolution model we have, so in theory it should be best in forecasting min/max temperatures. The fact that the UKV has consistently been forecasting 34-36C too, to me assuming it produces the same values the day before then if we don't see temperatures of 34-36C then I think it will be a bit of a disaster from the UKV tbh.