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staplehurst

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  1. Don't forget that's for surface-based convection - storms on Friday will be largely elevated, and very high-based at that! (10-12,000ft)
  2. I think in general they all vary in their performance - some handle certain situations better than others, and vice versa. Surface-based convection is easier to verify which models handle it best because ultimately the air parcels are always being lifted from the same level, i.e. the surface (for example GFS has a moisture bias and is too keen on develop convection in capped environments). But when it comes to elevated convection, it all depends on which level you're lifting the air parcel from, how much forcing / moisture is available etc, so it ends up being not a fair comparison between events. GEM from memory was rather (rightfully) unenthusiastic for the 21st May event (which ended up largely busting), while also had a pretty good handle on the Aberdeenshire MCS several days in advance on Sat 27th June. ICON-EU probably had the best handle on the elevated thunderstorms that affected Northern Ireland and SW Scotland early on Thurs 25th June (most other models were too far east over the mainland initially). In some cases, such as French imports, it almost ends up being a case of following climatology rather than what the models are suggesting...
  3. Forecast sounding from 00z ARPEGE for Friday afternoon over Cen S England, associated with instability plume arriving from France. Elevated convection rooted from 650mb (cloud bases 12,000ft!). Very dry both aloft and below this level, so precip will likely largely evaporate before reaching ground, and also convection may struggle to maintain itself given how dry it is aloft. Probably why the EC (and most models) look fairly dry with no major rain totals at the surface. This increasing mid-level convective cloud may also impact how high the temperatures reach across southern England on Friday afternoon, for example. Substantial elevated mixed layer and deeply mixed boundary layer would require surface temps around 40C or higher to develop surface-based storms, and even this assumes a dewpoint of 15C which may be too high - which is a shame, because the wind profile is very nice! The whole instability plume will continue to advance NE across Midlands, northern, eastern and southeastern England during Friday afternoon and evening, clearing to the North Sea during the early hours of Saturday. Uncertainty at this stage at how upper forcing will phase with elevated instability, and therefore how widespread any elevated showers/thunderstorms may be. Still a few days away for this to chop and change... Given these profiles, strongest convection could produce some rather gusty winds / heat bursts.
  4. Pockets of elevated convection in the warm advection regime - judging by satellite and radiosonde data, the convection probably wasn't that deep but went up in a hurry...
  5. Just a wave on the front - yesterday's 12z EC did a reasonably good job with it, while many of the high-res models struggled with the extent of the precipitation. This is very common with frontal waves - they are often more extensive and further north than models would imply...
  6. If you zoom in quite a bit you can see the extreme tip of Hampshire is in the pale grey (1 thunder day) shading. But it's quite a quick gradient to 3 days just to your north - where there were some lightning strikes within the 10km radius on Thursday 11th June, for example...
  7. It hasn't ended yet! But potentially not enough upper forcing - we'll just have to see how the next 36 hours plays out, there is plenty of potential, will there be enough trigger...
  8. Looks like an elevated thunderstorm has developed just SE of Falmouth with recent lightning in the area. 12z Camborne ascent (typical environment that will be creeping into Wales this afternoon) requires a surface temperature of at least 29C (preferably higher) combined with dewpoints around 17C to break through the cap, and develop surface-based convection. Modified profile yields 2,000 J/kg CAPE with some reasonable shear. Any storms that can fire, particularly W / NW Wales but perhaps also NW Devon, could become severe with large hail and strong outflow gusts.
  9. For the East Midlands (profiles below from west Lincs) there is potential for elevated thunderstorms during the middle of the day, rooted from around the ~750mb layer, so bases would be around 8-9,000ft. The low-level environment is capped to surface-based convection until perhaps late afternoon or evening, and so it's a bit touch-and-go as to whether something can fire, but if it does it's more likely during the evening hours...
  10. Environment is too capped (CIN shaded green, CAPE shaded orange) across SE England for surface-based storms on Friday afternoon, the hot air is just too deep to overcome the cap - you would need surface temperatures of around 34C or higher, and even then the profile is very dry aloft. This does not rule out the odd elevated shower/storm developing, but most of these will have cleared to the east by the afternoon - and the morning cloud cover associated with these may also hinder surface temperatures somewhat. Conversely NW England has much less capping, and with surface temperatures of 25C or higher, and dewpoints in the mid-high teens, the forecast profiles yield substantial CAPE and likely explosive and potentially severe thunderstorm development.
  11. The UKV isn't exactly 100% right all the time, each run will vary (as is the case with all the other models too). What is worth noting though is that given the degree of CAPE over the English Channel overnight, any storm that does develop will be very active. Models will naturally struggle to simulate exactly where and when these will crop up, but the instability plume will be migrating gradually eastwards through the night so all areas have some level of 'risk' as a result. If I were in southern England tonight I would probably set a couple of alarms, window left open just in case - because it would be a shame to miss out on a potentially good show...
  12. That's the plan ? Anywhere from Cumbria / IoM north into southern then central Scotland.
  13. Aye! Was tricky to know what search radius to set around a location, as your ability to hear thunder varies on many things (background noise, local topography, during the day or night etc) but 10km seems to work relatively well...
  14. Haha I know what you mean. Whenever it gets mentioned you know there's a distinct possibility of a bust! ?
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