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

[Harry]

Hmm, not sure about that. NAE's not exactly showing the love for the SE at the moment.

Look like it's gonna go down from the Midlands north.

You know it makes sense.

Based on most of the models thus far I agree with that Weather09

However I remain sceptical about the models continuing (bar the latest 18z GFS) to ignore the storm hungry south easterners....A bombastic atmosphere is a bombastic atmosphere and I fail to see why the atmosphere would bang for say the Midlands but not the SE...there is IMO no obvious reason why...SBCAPE AND MLCAPE, check, heat, check, trigger, check, high wet bulb and all the other stats, check...the one poison is CIN which I still fail to see a valid enemy, given the presence of a trough AND active CF.....

I more often than not accept the models but my gut on this occasion says noooooooooooo to the computer saying noooooooooooooooo!!

[Harry]

Yep, the NAE (if it's to be believed) keeps the SE quadrant almost bone-dry throughout the entire period out to T48 on this current run....awaiting on tonights NMM run....twists & turns to come, me thinks

Precisely!!! An atmosphere rich with moisture but the SE gets nuffink????

36-48 hours left to play....

[A.J]

Based on most of the models thus far I agree with that Weather09

However I remain sceptical about the models continuing (bar the latest 18z GFS) to ignore the storm hungry south easterners....A bombastic atmosphere is a bombastic atmosphere and I fail to see why the atmosphere would bang for say the Midlands but not the SE...there is IMO no obvious reason why...SBCAPE AND MLCAPE, check, heat, check, trigger, check, high wet bulb and all the other stats, check...the one poison is CIN which I still fail to see a valid enemy, given the presence of a trough AND active CF.....

I more often than not accept the models but my gut on this occasion says noooooooooooo to the computer saying noooooooooooooooo!!

A good post H...whilst we're pouring all over the latest model data it's easy to overlook that model data is very rarely 100& accurate even at the very short time scales, and that's where sky watching and radar watching become more and more prevalent...The models suggest Midlands northwards, but it's not definitive

Edited June 26, 2012 by ajpoolshark

[lorenzo]

Looking forward to Thursday.. some excitement in the weather at last. Beats a stagnant pattern any time.

Do not claim to have any expertise with these and they are on my learning to do list. Matt posted them on Twitter the other day and still the CAPE figures still look 'uplifting'. Think it will take a while to understand skew-t and soundings.

FWIW this chart from Fairford draws attention..

You can create plots here and the list of places/available plots can be downloaded from here.

[Lewis]

Anyone want to see a magic trick??

You look at the SB cape and it shows this

You look at the ML cape and it shows this

And that's for 2am thursday morning, the NMM shows tomorrows (wednesdays storms) rumbling on right through the night, conditions are excellent to support storm development anywhere in England starting from tomorrow through to thursday!

[Supacell]

Hmm, its still all over the place with the models for Weds night into Thursday and i am too tired to make heads or tails of it now so i think bedtime for a few hours and then wake up refreshed in the morning with the hope of some better agreement between the models.

I do, however, feel reasonably confident that the East Midlands and Lincolnshire into East Anglia will be the best placed areas for tomorrow. Question is, after i have spent the afternoon pottering around these lands should i then be driving down to the southwestern coasts for a possible overnight MCS, go home and wait for more storms on Thursday or just sleep on a park bench somewhere awaiting a morning drenching

Loving the magic trick Lewis and that is why i am thinking of heading south - those elevated storms may be something to behold. I could then try and chase the storms all the way back to my house. I think i am going to need a red bull or three tomorrow night as may be doing an all-nighter.

Edited June 26, 2012 by Supacell

[Lewis]

Hmm, its still all over the place with the models for Weds night into Thursday and i am too tired to make heads or tails of it now so i think bedtime for a few hours and then wake up refreshed in the morning with the hope of some better agreement between the models.

I do, however, feel reasonably confident that the East Midlands and Lincolnshire into East Anglia will be the best placed areas for tomorrow. Question is, after i have spent the afternoon pottering around these lands should i then be driving down to the southwestern coasts for a possible overnight MCS, go home and wait for more storms on Thursday or just sleep on a park bench somewhere awaiting a morning drenching

I feel so privileged

[Supacell]

I'll add some more to that: http://www.estofex.org/

They reckon multicells/supercells overnight with a large MCS expected to affect the UK and Ireland.

Edited June 26, 2012 by Supacell

[Bobby]

There's a lot of talk about the E and N (MetO especially) being the hotspots but the Estofex seems to agree with the NMM with the SW looking pretty good too. The latest NAE also has have upgraded precipitation for the SW, with the HIRLAM looking tasty too. Hopefully we'll all get something.

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.

Conditions seem supportive for a large MCS to affect Ireland and UK during the night. Heavy to isolated excessive rainfall amounts will be the main hazard next to isolated large hail and strong wind gusts.

Tasty

Edited June 26, 2012 by Barb-

[Darren Bown]

I'll add some more to that: http://www.estofex.org/

They reckon multicells/supercells overnight with a large MCS expected to affect the UK and Ireland.

Interesting as when you read through the discussion at the end of the UK discussion, it almost suggests there could be a possibility of an upgrade if certain factors change.

[Costa Del Fal]

"The main area of interest will be Ireland and UK, situated along the tip of the ridge, where weaker cap and better forcing probably assist in scattered CI. DLS remains modest with 10-15 m/s forecast, so pulsating storms/isolated organized multicells are possible. This activity weakens during the evening hours.". Yummy.

Must say, Estofex do sound pretty darn confident on some of the best goods for the UK.

Edited June 26, 2012 by Blizzards

[richardc1983]

Had a look through the threads but cant find anything relating to Leeds. How is it looking for us?

[Kain]

This is getting to be a very exciting few days asl long as we don#t have El Gordo MkII

Things are looking up for Shropshire..I'll be darned!

Edited June 26, 2012 by Kain

[Costa Del Fal]

I must say with all that ML campe being spilled out tomorrow night like shown on the NMM 18z I will be stunned if something doesnt kick off. Cant remember the last time so much energy transferred over this way overnight and also how much of it is in the far West at fist and spreading NE giving pretty much everyone a chance.

[Keraunic]

Don't know if it can be relied on, but my weather app has changed in the last hr or two and it has Ipswich getting storms from early evening into the night on Thursday. We shall see.

[Sprites]

Is this a spanish plume setup? I dont think it is exactly , more of a tropical maritime airmass being replaced with a polar maritime regime perhaps setting off convection.

[ZONE 51]

Precisely!!! An atmosphere rich with moisture but the SE gets nuffink????

36-48 hours left to play....

What's actually going to happen is an MCS storm system the size of north France is likely to track across southern areas wednesday night and then hit the northern areas through thursday leaving behind home growns across the south and these tracking.. er.. north

Well proberly not!

[ZONE 51]

ESTOFEX storm forecast is interesting, there onto the potential MCS tonight(wednesday) ..if you don't already know this type of storm system would give widespread frequent lightning, so lots of thunderstorms around but kind of joining forces!

[ZONE 51]

Not any less risk for storms.

I'm especially interested in developments for tonight, very warm and humid air mass out there which will get more sticky today, with increasingly unstable air, the energy is building in the atmosphere and it won't be to long before those clouds go up into massive thunderheads, i am staying with moderate confidence of storms developing by thursday at least, there be around i'm quite sure of that but where exacty is the question.

Taking a look at some charts from GFS 00z

this is the convective cloud cover and soaring index for midnight, this shows where deep convection is possible, so why am i looking at this far south?and not homegrowns, this is because tonight we have the risk of imports from France, the areas with

bright green lines is stronger and most likely to create thunderstorms,

3am, this deep cloud cover pushes up into western areas, and look at the area into the South coast and Southeast,

very warm over France and really a humid night for us with 15-16C in the southeast, but depending on sunshine these temps

could be higher,

the NAE has these higher,

next the dew points at 3am same time as the temp charts above,

moist!

this really is thundery air,

UKMO at midnight, this is the 850s upper temps, see the 15C dotted line, thats the plume,

by thursday afternoon the highest upper 850s are still in the southeast,

(there are still variations in the models so nothing is set yet, but i do think a good chance of imported thundery activity across southern England through tonight and this pushing north/ne)

We now get to the stage were precipitation models can be used to scale down to more exact areas

early hours of thursday, HIRLAM model,(still on 18z)

charts so far are 00z

NAE shows a lot of action in the west, midnight-0600hrs

0300-0900hrs, this shows that the MCS if it develops would go up the west side(i would say it's likely at least over France)

but that won't rule out isolated storms in the east!

GFS includes more of the east, this is what i expect to happen,0000-0300hrs

this is 0300-0600hrs

the GFS CAPE at midnight, down over France! this is where the big ones develop

Lifted index at midnight!!

down there develops the storms for us, they would be so strong that they should make the Channel,

next the Lifted index charts show that very unstable air mass moving in, the would be thunderstorms, remember the 850s hitting the south coast around this time, a Theta chart next.

Thundery plume in the charts and it's heading our way!!

Just before i finish..

Are leave you with two charts for today, and this is before tonights potential storms!!

If i got anything wrong please do correct me! my post is also aimed at those that don't know the charts, but i'm sure many would be happy with what is showing today!

[Phelpsy]

Im loving the level 1 on estofex! Will see how things go, good luck evryone, excited muchly : )

[Liam J]

Pouring with rain here, not a pretty morning! 14.8c and feeling muggy.

Looking good later tonight and into Thursday, ESTOFEX chart looks interesting and rather busy.......

Edited June 27, 2012 by Liam J

[Supacell]

Good prospects for a lot people over the next 48hours and the bbc forecasts are now on board also with thundery downpours being mentioned for both today and tomorrow.

Today i will be out chasing around Lincolnshire as it is looking like the prospect of some storms developing across the East Midlands, Lincolnshire and northern half of Norfolk. These could then move up towards East Yorkshire later. I don't think they will be severe in nature but could still contain some decent lightning. The main threat from these will be large rainfall totals - and the slow moving nature of them will add to this risk (but make it easier for chasing). I will be avoiding cities on my chase as do not want to end up caught up in traffic going to see the olympic torch as it travels around Lincolnshire today

The level 1 from Estofex is more in relation to the overnight period. My initial plan was to head down towards the SW (specifically around Dorset) for an overnight chase but the latest charts from Hirlam (18z) and GFS (00z), although still showing great potential for an MCS, put the best storms being over N England tomorrow around midday/early afternoon and moving up into the NE - so on this basis i would be best served to save petrol and stay local. My final decision regarding tonight will be made on the basis of the 06z suites. I would fully expect Estofex to issue a level 1 for the eastern half of the country later on tonight for tomorrow.

[DanN]

Looking forward to Thursday.. some excitement in the weather at last. Beats a stagnant pattern any time.

Do not claim to have any expertise with these and they are on my learning to do list. Matt posted them on Twitter the other day and still the CAPE figures still look 'uplifting'. Think it will take a while to understand skew-t and soundings.

FWIW this chart from Fairford draws attention..

You can create plots here and the list of places/available plots can be downloaded from here.

That looks a pretty decent skew-t. Backed surface winds, not capped and looks like full height CB's if anything develops?

Later forecast skew-t actually has the surface winds backed up until 12pm and then they start the south westerly shift (for the same area), I guess that's the front which would suggest its run through the south west by 3pm Thursday - surface temp drops off and some much drier air over 800hpa by then as well.

[Coast]

I'll add some more to that: http://www.estofex.org/

Morning all, let me just expand ESTOFEX to get that detail:

A level 1 was issued for parts of UK and Ireland mainly for heavy rainfall amounts, isolated large hail and strong wind gusts.

SYNOPSIS

A long-wave trough is still situated over NE/E-Europe with another trough approaching western Europe during the forecast. Weak ridging in-between covers parts of the Mediterranean area.

DISCUSSION

... Parts of Spain, Bay of Biscay, parts of France, UK and Ireland ...

An extensive warm sector evolves over the area of interest ahead of an approaching trough over the E-Atlantic. A pronounced EML mixes to the N/NE during the day and overspreads a BL with increasing moisture. For this forecast, a medium between GFS and EZ was used regarding surface dewpoint forecast as GFS seems to be too bullish and EZ too reluctant. With dewpoints in the upper tens already present, we would not be surprised to see a few spots in the lower twenties mainly over W/NW France. With steepening lapse rates atop, capped MLCAPE exceeds 1kJ/kg during the afternoon hours onwards over NW France with lower values to the east, UK/Ireland and towards N-Spain.

During the daytime hours, a strengthening ridge and intensifying WAA regime probably preclude CI for most parts of the forecast area. The main area of interest will be Ireland and UK, situated along the tip of the ridge, where weaker cap and better forcing probably assist in scattered CI. DLS remains modest with 10-15 m/s forecast, so pulsating storms/isolated organized multicells are possible. This activity weakens during the evening hours.

During the daytime hours, a few thunderstorms also evolve over N-Spain, as a weak PV streamer moves in from the W (beside weak forcing as a mid/upper wave grazes the area of interest). During the evening hours onwards, a few small storm clusters may evolve with a movement to the NE (e.g. offshore over the SE Bay of Biscay and also towards far SW-France). Large hail and an isolated severe wind gust event is possible during the daytime hours (discrete storm mode) with a trend to hevy rain, marginal hail and strong wind gusts during the clustering stage.

The focus then shifts to the west ahead of a weakening short wave, which crosses the Bay of Biscay during the evening hours onwards. 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. Heavy to isolated excessive rainfall amounts will be the main hazard next to isolated large hail and strong wind gusts. Storms further south (NW/W-France) remain more discrete, so large hail (one or two very large hail events) and a few severe wind gust events are well possible.

Right now, there is no sign that the overnight MCS event may produce any swath of enhanced severe wind gusts over UK/Ireland due to modest LL/mid-level flow and late arrival of strongest forcing. Hence a broad level 1 will cover the risk for now.

UKASF say:

Forecaster: Dan

Last Updated: 2012-06-26 21:00:00

Valid: 2012-06-27 00:00:00 - 2012-06-27 23:59:00

Areas Affected:

SLGT: N + E Midlands, Cheshire Plain, N East Anglia, Northern Ireland, NW Ireland, CS + SE England

Synopsis:

High WBPT advect northwards behind a double-structured warm front across Britain. Low-level convergence ahead of WAA over southern Britain will be the primary focus for convection initiation, especially if any shortwaves develop.

Discussion:

Confidence isn't high for today's general evolution due to extensive cloudiness and the WAA taking place. Nevertheless, with high dewpoints and SFC temps, some convection is possible over the Cheshire Plain and Lincolnshire, and possibly The Fens/Norfolk in the evening. Given CAPE projections of 600-700J/kg, and ELTs down to -30C, it is possible that a few thunderstorms may develop. Should a cell develop then 30kts DLS may allow the storms to become sustained for a time, but relatively slow storm-motion will result in locally large rain totals given PWAT up to 36mm.

A similar story exists for Ireland/Northern Ireland behind the warm front, with similar CAPE values forecast. Either way, these will be afternoon/evening thunderstorms, and thus are likely to decay overnight as diurnal heating subsides and a surface inversion subsequently develops.

Although a weak funnel cloud may just be possible, severe weather is unlikely.

------------------------

While WAA will provide sufficient capping over southern Britain during the daytime, the approach of the surface cold front and pre-frontal trough with the Theta-E ridge will allow destabilisation to occur with mid-level thunderstorms forming during the evening hours over northern France and the English Channel, drifting northwards into southern counties of England during the late evening hours. Due to the evelated nature of such storms, severe weather other than local flooding is unlikely.

Simulated MLCAPE values of >1000J/kg over the Channel would indicate quite frequent sferic activity, but with saturated upper profiles, storms will probably lose some sferic activity as they move inland, accompanied by a fall in MLCAPE. Depending on the evolution of developments, an upgrade to MDT may be necessary for lightning coverage.

Nothing from SkyWarn or TORRO just yet, I'll go and dig out some charts to consider shortly.

[Norfolk Sheep]

On the plus side, smiley Carol hasn't mentioned the H word at all this morning