Ian Fergusson
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Posts posted by Ian Fergusson
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Yes, NAE progging 20-30mm rainfall accumulations across parts of Wales, south-western and perhaps central southern counties by 12z Tuesday- with >10mm accumulations across the west Midlands. Not to mention the potential for heavy showers and perhaps isolated weak thunderstorms over same areas.
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.
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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....
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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
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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.
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.
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Thanks Ian, I thought as much but just wanted reassurance I was looking at the correct feature.
Kain
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.
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Call me stupid, but the overshooting top, how is it defined on a vis sat image? Would that be it what I marked on the image?
Exactly (plus note my comment re multiple overshooting tops)
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sorry to drift off the topic of our storms for a sec but wow what an explosion that around Torino is.
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
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I reckon we do only play at it here judging by the explosive clouds down the Eastern Coast of Spain visible on the link.
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.
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I take it that on the NAE 12Z that the very last chart shows plenty of showers developing in Wales, The Midlands and Southern England.
Still unsure as to their thundery element though. GFS doesnt create an exciting scene at all.
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.
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haha im just going by what netweather have said for my area between 4pm and 7pm they predicted 800 - 900 cape! wouldnt mind my own weather balloon to be honest!
Sunny here now good sign so that the convection can get going more!
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....!!!
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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....
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the big cloud turned out to be a dud!! im still hopeing as cape is still rising past 900J/Kg
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? ;-)
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It's cool seeing the storm cell move across the south east and split into two seperate ones
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.
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Very large thunderheads to my North, no doubt due to the action over the midlands.
It's the top of the thundery cells aligned up through N Herts (Hitchin to Royston, and adjacent Beds) you are seeing.
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Not convinced that would be the Brum UHI, rather could just be a broader development (though less intense than over the Cotswolds) along the general trough that is now clearing the West midlands.
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.
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Looks like the line of storms in the West Mids are increasingly turning into a Bow Line, or is it just my eyes being deceptive?
No, a bow-line is something quite distinct from this.
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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.
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Lightning to your West or South?
It's all still mostly due south of you - flashes in last 5 mins from about 1 miles south of Great Witley.
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They're delivering frequent lightning right now across Shelsleys, Hillhampton and environs. Lighting-up the ATDNet system in that district every minute.
.... plus two more flashes now recorded from another cell east of Worcester, above village of Crowle (off A422) and Peopleton (off A44)....
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Still no new cells behind this trough. I suspect thats how it will stay tbh.
They're delivering frequent lightning right now across Shelsleys, Hillhampton and environs. Lighting-up the ATDNet system in that district every minute.
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Why have the cells on the northern edge of the cells that have left Wales weakened so much? Seems to have coincided with a shift in direction of the cells.
Aaron
Various factors at play.... Probably losing the (upper) forcing as the shortwave trough eases east.
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Heavy shower just formed west of Margate NW radar.
Sky black to the west.
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.
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has a small shower here but nothing now could anything form this way ?
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.
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Hi Ian,
From what I can see the showers coming out of wales now over West Midlands are pushing across the penines to affect yorkshire and east yorkshire later this afternoon.
The high res NMM model shows this clearly;
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.
Convective Outlook
in Storms & Severe Weather
Posted
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.