Uk Convective General Discussion & Forecasts, 26th June 2012>

[Coast]

"Let me tell you where I am with this; I'd like to make you an offer........."

[Robbie Garrett]

See my entry last Saturday....I posted my thoughts on this then.......the models were predicting this secondary low for several days, nice to see the consistancy

http://forum.netweat...00#entry2321406

Yes mate, I saw it too when I came online.

It's been very consistent. I take it's not a secondary low, but more so a bay of Biscay disturbance?

"Let me tell you where I am with this; I'd like to make you an offer........."

I'll tell you where I am...

[A.J]

Some interesting conversations going on over on ukww. Talk of possible supercells and large hail up to 5mm!!!

http://www.ukweather...28th-june-2012/

I may abandon my Lincolnshire chase today and save the petrol money for tomorrow, as things are starting to look quite interesting. Considering Brick's forecast earlier, i cannot see the point in travelling to see heavy showers and the odd rumble of thunder. I want to be seeing MCS's/Supercells with hail and frequent lightning

Pop over to my place in the west midlands tomorrow...prospects look rather good atm....I am planned to help out in the kids school sports day, but I've a hunch it may well be cancelled...lol

[I Cumbria Marra I]

Are supercells very rare in the uk?

[Nick F]

Threat of sustained supercells for irish sea areas? wooooww!

Not sure about sustained or Irish Sea areas either, though strengthening shear towards the SW with the approach of the SW'erly jet max could favour some elevated supercell structures across SW England, S/E Wales and SW Midlands tonight as the high theta-e plume destabilises.Rotating updrafts in these storms could favour isolated moderate size hail.

Alot of uncertainty though, so a case of nowcasting with the N-W radar - storms most likely across the SW tonight, early tomorrow - perhaps forming an MCS - though a few isolated storms popping up further east on the eastern edge of the plume as it destabilises.

An MCS probably tracking further NE across Wales, Midlands and N England during Thursday, plume still holding on across the SE and E Anglia through the day and if overnight detritus clears sufficiently, temperatures reaching 26C could trigger some strong storms before the cold front moves through later in the day.

All-in-all could be the most interesting 36 hrs for storm potential so far this year.

[Neilsouth]

Are supercells very rare in the uk?

Rare yes but they do happen, i've seen one

Amazing even just to watch them develop upwards of a late evening

[Bobby]

Analysis of the forecast tephigram for Plymouth for the overnight hours suggests ~700 J/Kg of elevated CAPE and cloud layer shear of around 30-35 knots.

This is enough for updraught rotation and perhaps elevated supercells and multicells. Hail to 2-3cms would be possible from this activity, and it may conglomerate into an MCS –

If the latest NMM upgrade is right than it's more like ~1,500+ j/KG cape, there is also much more SBCAPE showing. Estofex also mention MCS/Supercells. Interesting stuff. I guess it'll come to radar and window watching in the end.

Estofex:

The interaction of modest forcing and the aforementioned CAPE plume results in numerous areas, where CI is likely, mainly from NW/W-France to SW-UK/Ireland. A coupled jet configuration will be in place, so current thinking is that numerous large storm clusters evolve with a gradual movement to the E/NE. Shear in all levels increases by 5-10 m/s, so well organized multicells/isolated supercells are likely. The main activity will be elevated with ongoing deep/intense WAA, but we can't exclude a few near surface based storms mainly over NW France, where highest BL moisture is forecast. Conditions seem supportive for a large MCS to affect Ireland and UK during the night.

Edited June 27, 2012 by Barb-

[Deluxe]

The only thing that worries me about the upcoming event is how much cloud there will be tomorrow. It would be awful if the risk was heavily diminished because of cloudy detritusy rubbish. Apart from that, it's all good!!

[Mapantz]

I like the estofex forecast .. level 1 MCS.

[Jane Louise]

This is all so exciting It's going to be a long night. Thank you to all who have posted up charts and forecasts keeping us updated. I really can't wait to see what happens.There's so much potential there! I'm going to remain optimistic and if for some reason we don't get a storm there's always going to be a next time.

[DeepSnow]

Just seen BBC weather forecast for Wales and overnight tonight and into tomorrow it showed thundery rain moving up mainly over south/central Wales (first time i have seen the lightning symbol on there for a long time) so fingers crossed. Just wish all this cloud would go!

[Chris.R]

Well it's cracking the flags here and I haven't felt it this humid since 2006!

[Keraunic]

You just watch; I'll be on my way to Ipswich later and Norwich will have a mahoosive storm.

[NO LONGER POSTING]

Looking good guys good luck everyone! At this moment in time its anybodys game ! So hold tight!

[Supacell]

All the forecasts go on about torrential rain, hail, convective gusts etc.... but if i am filming i would like some good lightning aswell. I have always wondered which of the parameters and charts can be useful for getting details of the frequency/intensity of lightning. Can anybody help me with this so i can check the charts for whether there will be much lightning. Any MCS's i have seen in the past have always been accompanied by plenty of lightning, is this always the case though?

[NO LONGER POSTING]

urrent surface observations show dew points in the region of 17-18oC across much of the Central/East Midlands, South East and Northern England, these generally 1oC lower than model guidance thus CAPE projections look reasonable. Their is now a HIGH RISK of thunderstorms for much of the Midlands, Northern England and parts of the South East through the early hours of Thursday Morning and through Thursday Afternoon. Due to the over-run of a strong jet streak these are likely to become organised with pulse storms embedded within the flow - some of these accompanied by large hail and gusty winds. EML plume affects all other parts with a quite widespread risk of lightning (some parts frequent). Worst affected areas are very likely to see very frequent lightning in this event.

Plume moves Northward from France and Biscay tonight as an MCS is expected to evolve and move across the country to affect many of us. Elevated mixed layer engagement is possible and with this the risk of heavy rainfall in a few places and the increasing threat of lightning (potentially very frequent and widespread). Through Thursday Afternoon stronger storms will be likely across the East Midlands and Northern England where a tornado watch is likely

A vortex to the W/SW of the United Kingdom is forecast to continue to strengthen and retrogress (move west-east) towards the United Kingdom. Model guidance continues to simulate a weak ridge of high pressure (anti-cyclonic) arched from the Bay of Biscay across Southern/Western Europe drawing in our airmass from a deep South Westerly source. As the vortex moves progressively further East and closer to our shore so stronger WAA (Warm Air Advection) will develop. Strong WAA with +55/+58 theta-ew gradients or T850 (+15) will begin to filter Northwards during late Tuesday into Wednesday increasing the overall risk of a few heavy showers or thunderstorms developing before the bigger engagement on Thursday. CAPE in the order of 500-800j/kg is being forecast for Wednesday as WAA training begins. Relatively strong subsidence CAPPING will be in place as the upper levels remain stable (however) an upper trough and cooler 500mb region across more North Eastern parts of England could increase the risk of a few thunderstorms breaking out as early as Wednesday (perhaps) the odd one breaking out across Eastern England in general.

Timing remains uncertain (during Thu AM) a warm EML (Elevated Mix Layer) plume will begin to engage and some isolated to partially scattered thundery rain or storms could break out across Western England and Wales and move some-where close to the Midlands for early morning Thu. Some uncertainty exists in this forecast at present and greater detail will be provided in updates to follow. CAPE during Thu AM early hours is projected relatively high at 600-1200j/kg but any convection will likely be high-based and elevated in capacity of a Spanish Plume initiation. Main risk frequent lightning where engagement does manage to unfold. Rainfall risk should be limited (for the time being).

Greatest threat will be as we move into Thursday as very warm air is advected Northward and a well defined and strengthening vortex advances from the West. The cold front engagement with the very warm moist plume is likely to be the focus point for more geral convection and thunderstorms. Real attention is needed on the strengthening LLD (Low Level Jet) in association with the advancing vortex (low pressure). Strongest CAPE potential with overlap of this strong jet-streak will enhance general deep and shallow wind-shear profiles and will likely promote some quote intense storms (potentially severe) with the threat of large hail, gusty winds and the odd tornado where cells become routed to the boundary layer. Areas that have been boxed and oulined in purple are those that are projected to see an overlap of the jet streak with highest levels of CAPE. The West/East Midlands, Lincolnshire, Pennines and perhaps parts of West/East Yorkshire are definitely early areas to watch. Away from this area, surface heating could lead to a later CAP break and strong outbreak across London, Kent, Sussex and much of East Anglia into the evening - although these becoming mostly MCS and elevated again with a lesser tornadic threat.

So included in the graphic above is a wide-spread risk of isolated storm outbreaks with the initial onset of the cold front and then the more intense engagement potential across much of Northern England, Central England, South East for the Afternoon and Evening on Thursday. Specific details are difficult to ascertain at this rather early stage, but we rather suspect that this could be a firework event, especially for those further North and East. As we move into meso-scale we will add some detail on equilibirum levels, strom helicity and tornado threats. The Elevated Mix layer which could bring lightning displays to much of England will also be assessed.

As of Today:

Mixing ratio as of 09Z this morning across large portions of England are 9 - 9.5g/kg - intense heating over France during the day promotes mixing in the region of +14 - +15g/kg. Higher mixing in the region of 11 - 12g/kg overspreads some-time in the early hours of Thu AM 3am sort of time before intensifying further 13 - 13.5g/kg across parts of Central England and the South East. CEQ of -25< occurs primarily across West Country Eastwards coldest CEQ projections -30 or lower evolve from Kent, Sussex to London up towards much of the Midlands, East Anglia into Northern England. Elevated mixed layer lightning would be greater in lower CEQ areas, thus on current GFS output probably towards the SE arching into the Midlands etc. A pretty good region of consistency is evolving around Kent again for enhanced lightning. HIRLAM does project a greater lower CEQ further W towards Wales and Gloucestershire into SW England but here their is greater uncertainty as to how far along the engagement will be. East Midlands and Kent my bet on best lightning and hail risk

Boxed areas on the following graphic represent highest likelihood of lightning associated with tomorrow morning/afternoon MCS event. This is experimental as precise most active areas are majorly difficult to forecast - but the above should be a good guide. Remarkably similar to original forecast projections. Therefore graphic on the warning above in red remains the same.

THIS IS NOT MINE!!! WELL DONE IF YOU READ IT ALL AND YOU GOT TO HERE!!! WWW.METMONKEY.CO.UK THANKS TO KEITHY JOE FOR THIS FORCAST!!!!

[Mapantz]

The models have a 'mare during plume set-ups, so lots of variations on models runs, at this point i wouldn't worry too much if they're not showing what you want. It's likely to go down to last runs to get a decent idea, it could turn out to be a classic.

[Guest archiesmummy]

Hi all, don't groan at my stupid question but your all so clever on here so here goes....

Just because the forecasts on telly/apps etc don't show storms, is it possible they form from all the ingredients coming together so that it catches people out?

It just feels so oppressive here, and I am sure I can smell like a sulphur type smell out there!

Thanks in advance

[Kain]

urrent surface observations show dew points in the region of 17-18oC across much of the Central/East Midlands, South East and Northern England, these generally 1oC lower than model guidance thus CAPE projections look reasonable. Their is now a HIGH RISK of thunderstorms for much of the Midlands, Northern England and parts of the South East through the early hours of Thursday Morning and through Thursday Afternoon. Due to the over-run of a strong jet streak these are likely to become organised with pulse storms embedded within the flow - some of these accompanied by large hail and gusty winds. EML plume affects all other parts with a quite widespread risk of lightning (some parts frequent). Worst affected areas are very likely to see very frequent lightning in this event.

Plume moves Northward from France and Biscay tonight as an MCS is expected to evolve and move across the country to affect many of us. Elevated mixed layer engagement is possible and with this the risk of heavy rainfall in a few places and the increasing threat of lightning (potentially very frequent and widespread). Through Thursday Afternoon stronger storms will be likely across the East Midlands and Northern England where a tornado watch is likely

A vortex to the W/SW of the United Kingdom is forecast to continue to strengthen and retrogress (move west-east) towards the United Kingdom. Model guidance continues to simulate a weak ridge of high pressure (anti-cyclonic) arched from the Bay of Biscay across Southern/Western Europe drawing in our airmass from a deep South Westerly source. As the vortex moves progressively further East and closer to our shore so stronger WAA (Warm Air Advection) will develop. Strong WAA with +55/+58 theta-ew gradients or T850 (+15) will begin to filter Northwards during late Tuesday into Wednesday increasing the overall risk of a few heavy showers or thunderstorms developing before the bigger engagement on Thursday. CAPE in the order of 500-800j/kg is being forecast for Wednesday as WAA training begins. Relatively strong subsidence CAPPING will be in place as the upper levels remain stable (however) an upper trough and cooler 500mb region across more North Eastern parts of England could increase the risk of a few thunderstorms breaking out as early as Wednesday (perhaps) the odd one breaking out across Eastern England in general.

Timing remains uncertain (during Thu AM) a warm EML (Elevated Mix Layer) plume will begin to engage and some isolated to partially scattered thundery rain or storms could break out across Western England and Wales and move some-where close to the Midlands for early morning Thu. Some uncertainty exists in this forecast at present and greater detail will be provided in updates to follow. CAPE during Thu AM early hours is projected relatively high at 600-1200j/kg but any convection will likely be high-based and elevated in capacity of a Spanish Plume initiation. Main risk frequent lightning where engagement does manage to unfold. Rainfall risk should be limited (for the time being).

Greatest threat will be as we move into Thursday as very warm air is advected Northward and a well defined and strengthening vortex advances from the West. The cold front engagement with the very warm moist plume is likely to be the focus point for more geral convection and thunderstorms. Real attention is needed on the strengthening LLD (Low Level Jet) in association with the advancing vortex (low pressure). Strongest CAPE potential with overlap of this strong jet-streak will enhance general deep and shallow wind-shear profiles and will likely promote some quote intense storms (potentially severe) with the threat of large hail, gusty winds and the odd tornado where cells become routed to the boundary layer. Areas that have been boxed and oulined in purple are those that are projected to see an overlap of the jet streak with highest levels of CAPE. The West/East Midlands, Lincolnshire, Pennines and perhaps parts of West/East Yorkshire are definitely early areas to watch. Away from this area, surface heating could lead to a later CAP break and strong outbreak across London, Kent, Sussex and much of East Anglia into the evening - although these becoming mostly MCS and elevated again with a lesser tornadic threat.

So included in the graphic above is a wide-spread risk of isolated storm outbreaks with the initial onset of the cold front and then the more intense engagement potential across much of Northern England, Central England, South East for the Afternoon and Evening on Thursday. Specific details are difficult to ascertain at this rather early stage, but we rather suspect that this could be a firework event, especially for those further North and East. As we move into meso-scale we will add some detail on equilibirum levels, strom helicity and tornado threats. The Elevated Mix layer which could bring lightning displays to much of England will also be assessed.

As of Today:

Mixing ratio as of 09Z this morning across large portions of England are 9 - 9.5g/kg - intense heating over France during the day promotes mixing in the region of +14 - +15g/kg. Higher mixing in the region of 11 - 12g/kg overspreads some-time in the early hours of Thu AM 3am sort of time before intensifying further 13 - 13.5g/kg across parts of Central England and the South East. CEQ of -25< occurs primarily across West Country Eastwards coldest CEQ projections -30 or lower evolve from Kent, Sussex to London up towards much of the Midlands, East Anglia into Northern England. Elevated mixed layer lightning would be greater in lower CEQ areas, thus on current GFS output probably towards the SE arching into the Midlands etc. A pretty good region of consistency is evolving around Kent again for enhanced lightning. HIRLAM does project a greater lower CEQ further W towards Wales and Gloucestershire into SW England but here their is greater uncertainty as to how far along the engagement will be. East Midlands and Kent my bet on best lightning and hail risk

Boxed areas on the following graphic represent highest likelihood of lightning associated with tomorrow morning/afternoon MCS event. This is experimental as precise most active areas are majorly difficult to forecast - but the above should be a good guide. Remarkably similar to original forecast projections. Therefore graphic on the warning above in red remains the same.

THIS IS NOT MINE!!! WELL DONE IF YOU READ IT ALL AND YOU GOT TO HERE!!! WWW.METMONKEY.CO.UK THANKS TO KEITHY JOE FOR THIS FORCAST!!!!

Too far east I hope

[NO LONGER POSTING]

Too far east I hope

BLOODY GOOD FORECAST THOUGH!

[Liam J]

This is all so exciting It's going to be a long night. Thank you to all who have posted up charts and forecasts keeping us updated. I really can't wait to see what happens.There's so much potential there! I'm going to remain optimistic and if for some reason we don't get a storm there's always going to be a next time.

I have a very nice Moet & Chandon chilled in the fridge.... Get the glasses ready Jane

*Tries not to get toooo excited*

Edited June 27, 2012 by Liam J

[Cloudwatcher]

Well it's cracking the flags here and I haven't felt it this humid since 2006!

Just got the same grey murk that we've had pretty much all year here. Doesn't feel that humid or warm either.

[Kain]

BLOODY GOOD FORECAST THOUGH!

You would say that!! since its right over your head

[Keraunic]

Hi all, don't groan at my stupid question but your all so clever on here so here goes....

Just because the forecasts on telly/apps etc don't show storms, is it possible they form from all the ingredients coming together so that it catches people out?

It just feels so oppressive here, and I am sure I can smell like a sulphur type smell out there!

Thanks in advance

Ah, the smell of sulphur. That can be an indicator for some people. my niece smelt rotten eggs some weeks ago and minutes later we had a thundery downpour.

[Harry]

You would say that!! since its right over your head

Correct....I am in agreement what a superb forecast indeed

Glad to see my initial favoured hotspot (which I declared yesterday) of Lincoln still in the running