weather09

No change to main risk regions this morning - NI, Scotland initial risk late Tues/early hours Weds, then further destablisation over Wales north and east into N England and Scotland from morning and into the afternoon before clearing into the north sea. As usually is the case with these types of setups, things tend not to follow expectations, however has been run on run consistency now on the more likely track of storms. Conditions certainly conducive to severe storms capable of producing copious amounts of lightning, large hail and severe convective winds.

Ah yes, just saw it. Small warm front lol. Bit odd that official Met synoptic outputs aren't showing it. Think the focus, though, will be as 500mb heights fall from the west, together with disturbances aloft running north engaging very moist and unstable air mass. Steering flow looks like it might be southerly with sfc low tracking NE. Close call for here, then...

Can't see a warm front moving north over the country Tues - 18z analysis showed a warm front over NI/Irish Sea, to be situated over N Scotland tomorrow midday, with parent sfc low out over the Atlantic. Secondary sfc low(s) look to develop on the periphery to the S/SW late Tues - as upper trough and forcing aloft migrates eastward - which will track NE across the country bringing significant increase in low-level moisture and instability. GFS's sig. tornado/supercell parameter outputs look colourful for early Weds across regions of interest given considerable increase in winds and slight turn with height. This together with plenty of moisture and instability and forcing for ascent with upper trough and shortwave disturbances aloft points to risk of severe convective weather. Wales, N England and Scotland the main areas of interest atm.

Latest ECM keeping focus for storms over western and northern parts, with first round over NI and Scotland late Tues into Weds, then main round from SW/Wales early Weds, transferring north and east over northern England during the morning to early afternoon period: This in agreement with GFS, so getting a slightly better handle on track of storms. Meso models over next day or two should make things somewhat clearer.

Not sure why some were expecting something to occur today... Stuck under strong ridge and subsiding air aloft, and little forcing elsewhere to set anything off. We'll see much more CAPE build during Tuesday when temperatures reach the upper 20s/low 30s, but that'll largely go to waste too given ridge aloft.

ECM currently has a more NE steer to the mid-level flow; UKM and GFS more NNE'erly to N'erly. Why the ECM is modeling storms pushing right over the Midlands during the morning whereas the other two have much of the activity over the far W, perhaps nudging into W Mids, before all heads north to NW England and into Scotland. So relatively small discrepancies in upper pattern, which is to be expected, but will cause large differences to where storms develop and where they'll track.

Those are quite realistic values when you consider just how much warmth and moisture there is likely to be at low-levels. Moisture-rich air mass surging north and east from Tuesday evening, and will take a while for c30C heat having built up during the day to weaken. Latest GFS/ECM outputs continue to break out thunderstorms and MCS(s) somewhere roughly over SW/W onward toward Midlands, transferring N and E during Weds morning as 500mb heights erode and forcing aloft arrives with approach of upper trough. Reasonable increase in mid-level winds generates decent deep layer shear for low-end severe convective episode - frequent CG lightning, possibly large hail and strong convective downdraft winds. In other words, a morning very much like June 28 2012. That last part isn't meaning to be merely a ramp- the conditions during period in question look rather similar to that day, and the regions that look likely to be affected, and expected track of storms, also look similar.

Period still covered with uncertainty at this range, naturally, but some quick thoughts having glanced at latest outputs. Tuesday likely to be storm-free with very warm temperatures (perhaps hot toward the south-east) with long draw southerly to south-easterly flow off the continent. Plenty of CAPE showing on GFS, however strong, amplified continental ridge and dry profile aloft means likely to be very little in the way of deep convective activity, save for a very low likelihood of isolated break outs over high elevation over north and west UK. Tues night and into early Weds sees 500mb heights fall from the west with approach of upper trough, with low-level moisture also ramping up from the SW as sfc low moves north and east during Weds. This forcing aloft breaks out mass of thunderstorms from the SW/W, per GFS/ECM modeling, with likelihood of MCS given adequate shear profile. Storms would be rooted above the boundary layer, transferring north and east through early part of Weds. Further risk of surface based storms during Weds if very moist and unstable air mass sticks around long enough before cold front pushes east.

Yep, not surprised GFS modeling has converged with ECM/UKM on a potentially stormy outlook Tues/Weds - euros always leading Already considering booking a day off for this one, should current outputs hold to Monday. Moisture in abundance, plenty of instability, and an adequate shear profile would ensure good storm development/low-end severe convective episode. Still a little too far out though, but, finally, something in NWP outputs to get interested about.

Thanks for the reply, B. Any doopoint stats? Humidity down here has been something else this summer. Have had to turn the con air on a lot more compared to recent summers. Purchased more Magnum ice creams as well...

Ah, right. Is it also warmer and as humid as down here in the urban jungle? What are the doopoints like?

Best one tempers their expectations when it comes to warm and sunny weather in summer, especially if one resides somewhere in the north, such as Leeds. Not so much a problem down here though, tbh. Locals are tanning well, and getting their dose of vitamin D.

Not sure why people are complaining...

Yes, nice outlook for Tues/Weds on ECM/UKM where we see a negatively-tilted upper trough digging south to the west of Iberia, with an amplified stout upper ridge building over southern/central continent. At the surface, low pressure is modeled to approach from S/SW drawing up an increasingly warm, moist and potentially unstable air mass on the eastern flank. GFS different with the trough not getting as far south, and upper pattern generally not as amplified as euro models. More inspiring that it's the ECM/UKM showing the favourable synoptics and not the GFS in isolation, as is usually the case. Bit far out, though, so wouldn't get excited just yet.

Oh... Must be just the Midlands that has seen the good stuff. A lot of variety, so far, this summer. Clouds, rain, sunshine, lightning, hail... A real mixed bag.

Totally agree. As well as that, humidity has been extreme. Very oppressive. Think it's only been northern parts that have had a poor summer. Down here, great stuff.

Despite the fairly active period during parts of May/June, for me, has been somewhat underwhelming this year, so far, for storms. We've yet to see a period of proper heat, with setups favourable for the big storms lacking. Being the UK, always best to keep expectations low, but still.. Short term: shortwave upper low looks to slide SE during tomorrow bringing renewed push of cool mid-levels at 500mb from the NW, steepening mid-level lapse rates and generating marginal instability with surface heating from mid-late afternoon. Discrepancy between Euro4 and other models, though, on how far SE the upper low gets during hours of max daytime heating. Decrease in moisture on previous days - NW flow pegging dewpoints down to low 10s, upper singles figures - and light shear prohibits anything significant. Sea-breeze CZ setting up near eastern coasts with daytime heating, so one area of focus for showers/storms. Activity will be moving SE with NW'erly mid-level flow. Further out, ridge building over much of the country end of the week, but not really going on to set up in a decent location to get the real heat and potential to come to our shores.

Yes, last Thursday had plenty of moisture but relatively low instability, which meant torrential downpours but with lightning amounts not having been that high. Had the skies been clearer and temperature a good few degrees higher, no doubt CAPE would have responded and we would've seen an increased likelihood of severe storms. Agree the amount of moisture in the atmosphere that day would have had a negative effect of updraft strength given the lack of heating and build-up of CAPE, but point is in an environment of moderate/high CAPE, you could have PWAT values of 4-5cm but that wouldn't be considered an inhibitive factor for storm development. Would just tell us that there's a lot of moisture in the atmosphere. Agreed with Nick F when he mentioned that the more southwesterly sourced component to the low-level flow at the time perhaps the reason why it was too cloudy/murky, where a more southerly/southeasterly flow off the continent would have seen more in the way of clear skies.

Useful link on precipitable water and its relevance to storms: http://www.theweatherprediction.com/habyhints/294/ Think some are looking too deeply into this. CAPE and updraft speed determines lightning amounts/frequency. PWAT simply tells you how moist the profile is. Moisture is key to good storm development, however high moisture can lead to the issue of 'water loading', where high volume of water and intense rainfalls can slow updraft speed which can have a noticeable effect in weaker CAPE environments, where in the the initial stages of storm development you'll get some lightning, but then intense falls of rain quickly stifles the updraft. But in environments of high CAPE, this isn't an issue, but does mean that CAPE alone won't tell the whole story concerning potential updraft strength. In the real world, many factors influence updrafts.

Yes, still strong mid-level flow over country tomorrow though jet shifting east into Saturday as upper low and cooling mid-levels migrates eastward over the course of Fri/Sat. Environment becoming unstable to surface heating (perhaps several 100J/kg CAPE) over much of UK under cool 500mb profile and steepening mid-level lapse rates. In that respect, looks better than today as clearer skies look more likely. Being a post-front, maritime environment, however, no real warmth, low-level moisture nowhere near as high as the last 36 hours, and relatively low instability means significant convective weather would appear to be low. Though could be an ideal mix of CAPE and shear, particularly toward the east where models have the overlap of strong SW'erly flow aloft and instability. So shear possibility taking advantage of any stronger updrafts that can develop (enough for updraft/downdraft separation) to bring about a more sig. risk. Moderate size hail and gusty downdraft winds the main risks in that case. Otherwise generally a showery day with moderate risk of scattered storms.

Really good dewpoint obs across the SE - a few 20C readings, but mostly 18-19C. Ripe for storm development with good sfc heating. Environment down there is primed for severe storms. Here's hoping.

Good to see that the regions that were expected to get storms, got them. Nice to see those who said things would stay over the other side of the channel, or only produce occasional lightning if storms did affect here, hold their hands up. Yeah, not likely. Risk continues this afternoon for eastern England and the SE as strong heating of very moist boundary layer airmass (dewpoints currently 18c; Euro4 progging 19C) east of the frontal boundary generates several 100J/kg to 1000J/kg MLCAPE. Mid-level lapse rates steep at over 7C/km. Sfc wind convergence, frontal forcing, and forcing aloft with upper trough and divergence with left-exit jet all providing means of lift. Deep layer vertical wind shear remains favourable given strong SW mid-level flow. Shear mainly unidirectional (little change in direction with height), however doesn't preclude risk of supercell development where speed shear can still induce rotation at mid-level. Large hail and strong downdraft winds the main risks here. Otherwise risk of moderate to strong, organised storms. Low-level shear a bit weak, so tornado potential somewhat inhibited. 0-3km storm relative helicity (SRH) starts of modest but increases toward late afternoon with increased low-level shear, so tornado risk heightened with any strong storms that develop and become mesocyclonic. Interesting period, hopefully.

Shhh, sweep it under the carpet. Let's pretend there are no storms occurring at all...

For those who did say storms were likely to stay over the other side of the channel because of past experience, and because UK, good forecast, guys.

Storms barely clipping Kent they said... Large band of rain with occasional lightning he said... Hahahah.