Ian Fergusson

Today's Phrase of the Day: Isentropic Upgliding Oh yes, it's a major part of the mechanism that's led to a lot of you seeing some storms today! So, impress your friends by using it down the pub. Or in Scrabble. But best swot-up on what it is, perhaps? e.g., http://www.theweatherprediction.com/advanced/isentropic2/ Enjoy.

Agreed.... I suspect we could get into a situation where the combined accumulation of frontal PPN and convective / localised stuff become a bit problematic for some. We shall see.

Just saw the MOGREPS prog charts for Tuesday.... the rainfall prob >10mm that day looks like offering a right soaker for a fair part of the West / West Mids / Wales....

Divergent motion now very evident on radar (if you refresh the feed). Gone supercell - a swift left-mover....? They had a good supercell there back in July 2008, I recall. http://www.meteoliguria.it/dati_osservati/areali/radar.html?type=rpa

Divergent motion now very evident on radar (if you refresh the feed). Gone supercell - a swift left-mover....? They had a good supercell there back in July 2008, I recall.

No worries. Radar interesting for this one.... a hint of an echo-free vault and somewhat divergent storm motion on last frames (?) but I'm going to try an log into a higher-res feed from Ligurian Met folks. I still think it's a severe multicell gig on balance but we'll see. Historically, a good area between there and into Switzerland / Austria for supercells, certainly.

Exactly (plus note my comment re multiple overshooting tops)

The higher-res vis-sat I've checked shows apparently a number of overshooting tops..... plus radar suggestive of something perhaps emerging into an MCS-like feature. So not supercell but note on vis-sat the clear shadow cast eastwards on the ground by the explosive growth - - it's a monster. Local radar for those interested via our Italian colleagues at http://www.meteoligu...r.html?type=rpa

Yup, sure thing - however if I was storm chasing anywhere in Europe right now, I'd be around Torino, NW Italy, plus anywhere northwards into the Alps.... serious severe T-storm action there right now. Not sure if it's gone supercell as yet for that Torino monster (possibly - I need to check; lots of SFERICS from it also), but the development has been truly explosive. Fab stuff. Check the loop at www.sat24.com/it and the clearly visible shadows from the overshooting top.

Yes, but killed-off eastwards now as the transient ridging takes over. Vast improvement already here in Bristol: Beefy TCu's of only 25mins ago now replaced by very well capped Strato Cu and plenty of blue sky / late sunshine.

Indeed! Yes, I guess that's via the GFS products.... You'll note how the GFS modelling of windfields at different levels is pretty good today across the UK. For example, check out the anvil flow off CB's very evident in parts of Herts and East Anglia at www.sat24.com/gb and you'll see they're blown largely northwards in the prevailing flow up at the tropopause.... then align this with the GFS 300 - 500hPa windfields.... versus the prevailing storm motion and the 700hPa fields. Clearly a balloon would be a lot of fun, albeit not - in your case - if released from Watford into paths of the many airliners routing / holding via the VOR navigation beacons at Bovingdon and Brookmans Park....!!!

Incidentally, the transient ridging and clearing skies that'll gradually ease eastwards this evening / tonight are now very well marked on vis-sat imagery.... some super evening sunshine into Bristol and environs now and those clearing skies evident into many adjacent districts too (as are the convective / T/S tops out east), if you check out latest EUMETSAT loop via www.sat24.com for example....

You saw the back of the cell (with a hint of some flanking line) heading now up past Stevenage to the NE.... hey, how can you tell the CAPE values? Have you gotten a balloon and Radiosonde for yourself from eBay? ;-)

Yes, the outflow effects on generating adjacent cells are often quite marked; tricky to accurately model too, much as on a wider (MCS) scale. All sorts of localised variables.

It's the top of the thundery cells aligned up through N Herts (Hitchin to Royston, and adjacent Beds) you are seeing.

Agreed. General trend later into tonight is for all to slowly quieten-down before midnight, albeit UKV continues to offer PPN rates of 30mm+ in 3 hrs from some cells (low point probability of this, however; 10-16mm p/hr being reported from a number of SREWS lately). Vast majority of districts turning dry and settled into late evening and overnight as the transient ridge shows its hand (already doing so into the west). Still a few (ever-weakening) showers continuing over parts of central Pennines until daybreak, however. Broad thrust for tomorrow's developments remain as previously noted here in my earlier message. New NAE, as modified by Chief F/C at Exeter, highlights deepest instability tomorrow expected in NE England and Scotland. Story for Tuesday remains as before, with much more widespread signal for heavy convective PPN and potential T/S.

No, a bow-line is something quite distinct from this.

So far, so good with the NAE/UKV prog this afternoon.... the lively development out east of Crawley and into Kent being the only mesoscale element missing, but it'll be assimilated into the next run. I'll return to offer any relevant update later.... Dashing off now, as I need to turn my attention to preparing our F1 forecast for next weekend's race at Montreal. Have lots of fun with those storms! Ciao.

It's all still mostly due south of you - flashes in last 5 mins from about 1 miles south of Great Witley.

.... plus two more flashes now recorded from another cell east of Worcester, above village of Crowle (off A422) and Peopleton (off A44)....

They're delivering frequent lightning right now across Shelsleys, Hillhampton and environs. Lighting-up the ATDNet system in that district every minute.

Various factors at play.... Probably losing the (upper) forcing as the shortwave trough eases east.

It's turned thundery, Dave. Two SFERICs recorded in last few mins from it (one offshore). The next nearest action to you has just sprouted-up over in Sussex.... we're watching a few SFERICs in last few mins at the east end of Gatwick's runway and a couple of miles away east of there at Domewood.

I'm expecting it to east of you. Watching developments at this very moment over the Cotswolds (near Colesbourne and further north just west of Stow-on-the-Wold). This is the first hint of the evolution for that region I mentioned in my earlier post a little while ago.

Yes, the NAE and UKV are in broad agreement with NMM, albeit taking the clusters largely a tad further northwards later, into Yorkshire / Durham / Tyne & Wear and the majority then exiting 'stage right' into the North Sea by around 20-21z. Also a signal for some hefty cells later into this evening in parts of the NW (NW Pennines, to the south of Cumbria). The driver for this is a shortwave trough and associated high vorticity.... it'll get swept-up ahead of the main trough arriving from the west and in doing so, provides a quite distinct focus for the showers / t-storms into the NE this afternoon and evening.