Harry

Incidentally, Euro4 holding strong with no precip at all across the SE quarter. I'm trying to cast my mind back to last year - think it was 17th July (the day before El Shelfo across most of the SE) when the BBC forecast and UKMO forecast both ruled out storm risk across the SE (favouring SW and W), then being woken at 1-2 am by my beloved telling me there was thunderstorms. Think I'll have a gander at those Synoptics later to see if there are any similarities.

My heart tells me to expect the worst in my part of the world, but my head says the ingredients exist and to trust in GFS. What's more, the precipitation forecast on the UKMO website clearly favours the West. However, the UKMO charts available elsewhere have continuously pointed towards much more widespread precipitation, including the SE. If UKMO and NMM are correct (and to be honest they've hardly exactly hit the nail on the head the past few days) it would mean nothing fires over N France - over 3,000J/Kg of CAPE, LIs of -8 to -10 (SBCAPE), falling pressure from the west, shearing winds and fronts close by, eventually clattering into that instability also - as Nick F stated last night, it seems a bit hard to compute that it won't detonate. All to play for, I'm going to try avoiding perpetual forum gazing today and try and adopt the Doris Day mantra....que sera sera! (I won't be far away though lol)

Right, off to bed. Fingers crossed that we wake to some more favourable Synoptics, cap busting ones

Estofex out Storm Forecast Valid: Fri 03 Jul 2015 06:00 to Sat 04 Jul 2015 06:00 UTC Issued: Thu 02 Jul 2015 22:17 Forecaster: GROENEMEIJER A level 2 was issued for NW France and the channel region, for very large hail, severe wind gusts and tornadoes and to a lesser extent for extreme precipitation. A level 1 was issued for a greater part of Northern and Western France and the Southern United Kingdom for large hail and extreme precipitation. A level 2 was issues for parts of Northern Germany and Southern Denmark, for large hail, and to a lesser extent for severe wind gusts and extreme precipitation. A level 1 was issued for Northern Denmark, Southern Germany and the Alps for for large hail, and to a lesser extent for severe wind gusts and extreme precipitation. A level 1 was issued for the Southwest Ukraine, Southeast Moldova and East Romania for extreme precipitation and large hai. A level 1 was issue for parts of Northwest Russia including Southern Karelia, and the oblasts Leningrad, Vologda, Tver, Novgorod and Yaroslavl, mainly for severe wind gusts and tornadoes. SYNOPSIS Friday morning at 06 UTC...a ridge extends from the Western Mediterranean to the Baltic States and a cold core low is slowly drifting southwestward over the western Black Sea. Very high lower-troposperic temperatures are present the ridge. An eastward intrusion of cooler near-surface air has made its way into Germany ahead of a second northward impulse over France of particularly hot air. DISCUSSION NW France... The forecast for this area is particularly difficult. NWP guidance suggests that a warm front will set up over the area during the afternoon and evening, and that steep lapse rates and moisture will lead to ample surface-based CAPE of 1000 (ECMWF) to 2000-3000 J/kg (GFS). In addition, a substantial elevated CAPE is forecast to develop during the evening over the Channel and Southern England. During the evening, the warm frontal zone features easterly surface winds, a brisk 10-18 m/s southerly flow at 850 hPa and 15-20 m/s southerwesterlies at 500 hPa. This yields a large curved low-level hodograph with 400 m2/s2 of SREH. Hence, strong rotation is expected in any boundary-rooted storm that might develop. A risk of very large hail producing supercells with - given the 10-15 ms/ 0-1 km shear forecast in the 18-21 time frame - a risk of (strong) tornadoes exists. The difficulty is caused by the fact that NWP models are not uniformly producing surface-based convective storms. Indeed, a significant hindrance to surface-based development is the warm air at 850 hPa of around 18 C. The GFS model initiates what is likely surface-based convection within the level 2 area during the afternoon, but there is very little precipitation in ECMWF. I have decided to go with a level 2, with the understanding that there is a risk that surface-based convective over NW France may not occur at all, in which case the severe weather threat is limited to large hail and extreme rainfall from any elevated storms. England, Channel region, Benelux... Elevated convection should move in from the south during the late evening and after midnight. There is a small risk of large hail and extreme precipitation with these storms. Germany, Denmark... The boundary of cooler air generated on Thursday will likely be the focus of new convective development during the late afternoon and evening. For this area, the level 2 was issued. Along that boundary, relatively high surface moisture should be available, that in combination with the steep lapse rates lead to 2000 or more J/kg CAPE. 0-6 km shear is weak, but with 10 m/s it should sustain multicellular modes. The strong updrafts will likely cause large hail in some places, and the deep boundary layer may lead to strong local downbursts. Away from the boundary the probability of convective initiation decreases, but ample buoyancy still implies a large hail and downburst threat. Across Denmark, convective coverage is not a concern, but the risk of severe weather should decrease with the somwhat lower CAPE forecast there compared to Germany. Alps... In an environment similar to that over Germany, i.e. very hot with a relatively deep, dry boundary layer, scattered storms should develop during the day in response to the mountain circulation. The sizable CAPE forecast to develop over the Alpine slopes indicates that these storms, despite a lack of shear may produce very isolated severe weather, specifically extreme precipitation and large hail, and possibly strong downbursts. NW Russia... Within a strong west-northwesterly flow some CAPE is expected to develop to the warm side of a WNW-ESE oriented frontal zone. NWP guidance indicate modest signals for convective coverage. Nevertheless, the high shear prompts a level 1 to be issued for severe wind gusts but also for tornadoes. Eastern Balkans... On the western fringe of the md/upper-level low ample large-scale upward motion is forecast that should aid storm initiation. Indeed, NWP models simulate widespread convection. The shear is in the 10-18 m/s range, indiicating that some storm systems may be rather well-organized multicells. Some marginally large hail and, in particular extreme precipitation are forecaste to occur on an isolated basis. Creative Commons License

Indeed...but if that cap goes then expect explosive storms.

The black line denotes where severe potential exists. The coloured zones highlight probability of storms. Areas in the MDT but outside the black zone have good chance of seeing a storm but unlikely it will be severe. Areas in the brown or green zone but in the black zone, have less chance of a storm, BUT, if there is a storm, it has a higher probability of being severe.Hope that makes sense.

Convective Weather forecast out. Interesting read, noting the huge caveats. Day 2 Convective Outlook VALID 06:00 UTC Fri 03 Jul 2015 - 05:59 UTC Sat 04 Jul 2015 ISSUED 21:54 UTC Thu 02 Jul 2015 ISSUED BY: Dan ... NW HIGHLANDS ... Some wind convergence and upslope flow may develop a couple of locally heavy showers, perhaps a local flash of lightning in the mid/late afternoon. ... ENGLAND AND WALES ... Rapid warm air advection will develop across southern Britain through the evening hours, causing surface dewpoints to increase as a warm front lifts northwards. Meanwhile, the Atlantic upper trough will pivot NEwards, overlapping with the arrival of this plume during the evening, and providing sufficient lift. Consequently, expect thunderstorms to develop through the evening hours, initially fairly well-scattered across SW England, with activity expanding farther N and E as the evening progresses. With the approaching trough, DLS will strengthen with favourably-backed surface winds. This combined with 800-1,200 Jkg-1 MLCAPE suggests the potential for storms to become organised, perhaps into supercells capable of producing large hail. Forecast profiles suggest most storms will be elevated above 700mb, thus limiting the tornado risk, but if any storms do become rooted within the boundary layer, then there would be the risk of a tornado developing. There exists some uncertainty with developments farther east, namely across SE England and the Channel Isles. Capping may be too strong or upper forcing not strong enough to generate storms here (as per consistent signals in EURO4/UKV/ECMWF) while GFS is more keen to develop storms over northern France and run them northwards into CS/SE England. Given these uncertainties have opted to go for the general consensus for now (hence reducing probabilities towards the SE, the MDT placed where best agreement exists amongst most models) but cater for the risk of large hail and heavy rain (given PWAT 35-40mm) as the primary threats with any strong storms that may develop in central and southern Britain. In either case, mass ascent will see storms become more numerous as instability axis moves north, merging into an area of thundery rain and eventually losing most lightning activity during the early hours of Saturday as instability weakens and clears eastwards to the North Sea. It is likely that this forecast will need updating during Friday with threat level areas tweaked depending on convective trends.

Just remarked on that above...Wouldn't at all be surprised if Estofex, Convective Weather and others leave their forecasts until morning.,.being discussed on UKWW also how divergent the models are, chiefly Euro4 and GFS. UKMO seems to spreading potential back further east (though still firing on all cylinders in the west still), while across NMM varieties we have mass outbreak in Ireland (NetWx NMM4) to a whopping storm across SE and less further West (NMM5)....how a forecaster starts to untangle that I don't know.

My interpretation, perhaps wrong, is that a strong feed of moisture and energy from the SE, combined with prevailing S or SW steering winds (plus a strengthening jet), storms could potentially gain some spin. Moisture invades from the SE but all models predict storm motion either S-N or SW-NE.Regardless of tornadic potential, I am storm starved so would take a big standard storm at this rate Wouldn't at all be surprised if Estofex, Convective Weather and others leave their forecasts until morning.,.being discussed on UKWW also how divergent the models are, chiefly Euro4 and GFS. UKMO seems to spreading potential back further east (though still firing on all cylinders in the west still), while across NMM varieties we have mass outbreak in Ireland (NetWx NMM4) to a whopping storm across SE and less further West....how a forecaster starts to untangle that I don't know.

Hope you're right...this from any particular source? Latest UKMO precipitation forecast an improvement for the SE

Basically, what was a warm front with a trough and cold front tucked neatly behind moving in from the south, is now looking more like an occluded front moving in from the SW. All the while, the reincursion of high humidity and instability across the SE goes without trigger...that's according to an increasing number of models, but some still favouring original outcome.Areas where high instability is present will get nothing, whereas other areas will get rip roaring storms. Models last night and this morning in contrast were much better for the SE. In fact, NMM 5KM 12z still looking very good

Indeed...getting a bit fed up with this lol...expecting 28-30C tomorrow, 28C Saturday and not so much as a flash for the effort. As you say it is a couple of models...I'm just waiting for the 5KM NMM which looked awesome for us this morning...GFS still encouraging but usually it's less strong in very short timeframes. Apparently Euro4 going the way of the UKMO too...ECM not our friend either.

At a glance that looks like a mesocyclone

The Dartford/Medway/Essex storm is the Brighton cell reincarnated...died a death where I am (which is literally a few miles from where it is now) and now has reinvigorated...that is how localised it is. By the way, thanks for all the awesome vids...staggering storms! When you get large hail knocking around, that's the disco ball you get so jealous!!

Brother has just text me to say there is thunder and lightning in Rochester...my old haunt. That's a kick in crown jewels that now...dies here, swerves over my old abode and kicks out sparks....still, nice to have a few dashes of rain to cool the place down, house is still recovering from yesterday lol.

I think this Brighton cell has died electrically...just as its about to arrive... Not my year I'm thinking....even if nothing was forecast for today. Interestingly, didnt notice this before but the 6z NMM suggesting fair bit of SBCAPE around this afternoon, more than GFS was showing last night.

Have set the camcorder up just in case...sky darkening to the south Come on baby...lightning activity seems to be dropping to me however

Keeping my fingers crossed (but not holding my breath) that neat little Brighton cell holds it together...on a direct path for me, however can't see it holding together for an hour or more (even though it is very warm and humid (feeling) here now)... I hope the people who have been complaining about the Channel are watching lol...spawned that if nothing else. UKMO precipitation projections much like the NMM run now...missing the SE out completely...permission to start feeling sad

Thunderstorm broken out in the channel...interesting!!!

Me too...some models strongly steering away from the idea now.... If we get nothing tomorrow, that's three plumes with nothing here. Last year, most plumes produced for me. This year, complete opposite. Still, will await the 12z model outputs before jumping to any firm conclusions.

Mass divergence between different NMM models now for tomorrow....both 06z runs but with immensely different outcomes...the Beeb favouring the western option on their latest online forecast... And just to rub salt in the wound, sun out here and temperature and humidity rocketing after this mornings rain drops.

Channel won't be a problem - it's how far the unstable air migrates from the continent that will be key. MetO have a fat trough wedged behind the warm front tomorrow night, so chances are developments could be over our shores as well as potentially imported

Not just me then...that's good to know It works fine on my iPad but it has obviously offended my laptop!

I am trying to access the MetO website and it keeps coming up as a download....anyone else have this problem?

Like the pretty colours lol. Markedly like the Estofex Lvl 2 shape and location.