Severe T-Storm Risk UK & IRL June 29th-July 7th

[martinastro]

Moderate Risk of General Thundery Showers 06-21Z UK & Eire

Slight Risk Severe Thunderstorm Southern Ireland, Wales and Southern UK 06-18Z

Slight Risk of Strong Tornadoes Southern UK, Wales, E.Anglia and South Midlands 06-18Z

Probably the most serious forecast that I have posted to the UKWW so far this year;

Deep break away upper trough moves east through Monday increasing lift with steep lapse rates at all levels. Moderate divergent upper jet stream further increases lift with primary focus to the front left exit region. Increasing low level jet at 850mb establishes strong low level shear. Models currently develop high CAPE values as heavy surface moisture advects east mixing with mild air from the south. Potential instability is utilised as dry incursion pushes through inline with the predicted surface trough. Strong vertically stacked PVA max builds over Wales and moves east  adding to stronger convective potential.

Quite a day in store with potential for non severe convective gusts of around 30kts based on mean average values from 800mb to 600mb. Threat of large hail and defined risk of one or more strong tornado events are possible.

Particular attention is given to south Midlands  late in the day where the low level jet is shown to increase and overrun lighter winds at surface. Whilst winds would seem to be straight lined the speed shear should compensate to increase low level field vorticity. Upper winds are strong but show only slight increase with height hense a SLIGHT risk of Severe Thunderstorms is expected ATM.


UPDATE

As per earlier forecast with enhanced tornado risk zone (blue box) 15Z-18Z

Additional risk box added Scotland for enhanced risk of Convergence Zone Tornadoes.

Based on the most recent model update there would appear to be an enhanced risk for tornadoes this afternoon from north Dorset arcing through to E.Anglia where surface vector is reduced increasing LL shear. Upper dry air incursion times in nicely and pushes in from the west creating an arcing line of isolated strong convective cells. It is within this line that severe weather potential today will peak.

It is however noted that due to lack of any considerable veer at surface the risk for meso derived tornadoes today remains SLIGHT. A reminder that the broad coverage box does not mean that everyone in that box will see a storm today, but just that there is a defined risk. In fact I do not expect the thundery activity to be widespread in nature!

[Padraig OBrien]

very interesting indeed lets hope for the best love to be over in the middle of the UK

[Padraig OBrien]

well today so far has certainly lived up to its forecast we had a very bad storm earlier on today cudnt take anything my phone went dead it was very solid structure but didnt last very long  im hearing further thunder to my NW and heading my way the sferics on the irish weather network over Kildare and Laois Countys

[scott86]

barely a drip over belfast today 

[scott86]

spoke too soon, mammoth shelf cloud right over head now! just waiting for some sparks!!!

[martinastro]

Seen a wall cloud earlier but that was it. Instability is very week over NI this evening, storms everywhere else though. Any pics of the shelf Scott?

[Paul]

Quite extraordinary what a difference a few miles can make - torrential rain in Antrim - wipers on full speed, then from Ballyclare onwards, just 10 miles away, no evidence of any rain at all! Sunny here on the coast 20 miles from Antrim.

[martinastro]

I know what you mean Paul. Very sunny and hot here with some cbs over the Sperrins...yet others are getting hammered by storms today. Check out the lightning activity over the UK so far today...

[scott86]

unfortunately not,,everyday there has been some action i have been in work,, im constantly having to nip outside to get a quick look to see whats happening, the main area of rain just missed me but it looked very nasty over towards black mountain! it all seems to be dissipating now, but a lovely sight all the same! any action over your direction?

[Padraig OBrien]

Torrential rain here again but no thunder very active day here

[martinastro]

Nothing of interest here Scott, there was great updraught towers early in the day and a wall cloud but then everything died out. I never expcted any t-storms in NI today due to building stability by the afternoon. I'm happy with what I seen on Sat though..I got my fix lol. This could be the end of the current thundery period until the next event. Chance of something on Tues for Britain but I think NI is out the game for the time being. Still plenty of more chances in Aug and Sept.  ..glad you seen a cool shelf cloud though!

[martinastro]

Moderate Risk of General Thundery Showers 09Z-21Z Central, SE and eastern regions of UK

Probably the last decent run of thunderstorms for a few days.

Occluded front looks to trigger further convective showers through Tues as CAPE values rise once again within a moist unstable climate. Upper cold pool moves slowly east but continues to influence central and eastern regions as surface temps rise. Vertical shear rather limited at all levels and upper levels are saturated up to the trop decreasing risk of any severe weather event. In addition to this we can expect some rather heavy cloud cover reducing insolation in many areas. Prime threat looks to be further localised flooding with slow moving storms.

UPDATE

As per earlier forecast. Whilst risk of Tstorms remains fairly moderate, the level of organisation within these storms looks rather poor. As mentioned by Paul, the whole set up looks to deflate by early evening as surface temps drop within the broad parameter of the outflow. A stray cell may venture toward the southern region of E.Anglia which could utilise some convergence and wind veer but not much else ATM.

Current CAPE overload looks based primarily on moisture advection. Though with expected cloud cover I'm not sure whether GFS predicted surface temps will be realised. Hense the predicted CAPE level is unlikely to be realised (opinion). This could well become evident on the next model output as the indices is adjusted likewise.

[Padraig OBrien]

I heard on the radio today that there was a tornado spotted down in Wexford County

[martinastro]

Thanks for the info Padraig!, let us know if you hear any further details about it. John T from TORRO will probably be investigating that one. Cheers. 

[Padraig OBrien]

Hi Martin just found this link it explains a couples house damaged by a tornado in Wexford County
http://www.irishtimes.com/newspaper/ireland/2009/0708/1224250237597.html