Uk Convective General Discussion & Forecasts - May 2012

[DeepSnow]

Would it be similar areas affected tomorrow as last night? or is the west in with a chance? lol

[NO LONGER POSTING]

The only thing about Wednesday nights rain into Thursday as it is set to hang around a little longer..

[MP-R]

I still find it incredible that despite being in Egham since September 2010, I've only witnessed one thunderstorm on May 26th last year. Egham's obviously not a favoured spot compared to other areas in the southeast.

Typically, my Mum at home was treated to a pretty decent distant lightning display last night apparently to see her birthday in.

[dave48]

Can't believe I slept through the whole thing! Wasn't on the ball at all...What a shame!

[Supacell]

If Round 2 is tomorrow I may consider driving down. Will need plenty of coffees/red bulls for work the next day but it would be worth it. I will take a closer look tomorrow and give it some serious thought. Living in Bradford, the only way I will see a good storm is to go to it, not wait for it to come to me.

UKASF have a forecast out for tomorrow indicating overnight storm possibilities, although do highlight less so than Monday night. Met office rainfall prediction looks remarkably similar to last night. Met office have no mention of thunder though, whereas they had warnings etc for thundery rain last night. Better idea by tomorrow morning i think.

Edited May 1, 2012 by Supacell

[snow raven]

Tomorrow Night is looking very Similar to Monday Night Across Southern Counties and the SE/East Angia.

Another disturbance Moves from SE-NW & Rounds the Low to our South West bringing Thundery Rain along a Moist Conveyer From Near The Alps.

Anyone for Round 2 Tomorrow Night ???

I won't be throwing in the towel half an hour before any storms arrive, thats for sure! I still can't believe I went to bed and missed a lightning show and some rumbles last night. Might have only lasted 20 minutes (according to Mr Raven who decided not to bloody wake me!) But even so, I feel cheated

I will personally buy matchsticks for my eyes in anticipation for tomorrow night - I'm not missing out on any potential!

Can't believe I slept through the whole thing! Wasn't on the ball at all...What a shame!

Snap!

[Coast]

Morning storm monsters!

Let's start by totally dismissing ESTOFEX (well, just for imby reasons you understand!! ):

Storm Forecast

Valid: Wed 02 May 2012 06:00 to Thu 03 May 2012 06:00 UTC

Issued: Wed 02 May 2012 06:14

Forecaster: PUCIK

A level 1 was issued for Germany mainly for excessive precipitation and large hail.

A level 1 was issued for Belgium and SE Netherlands mainly for excessive precipitation.

SYNOPSIS

The main macrosynoptic feature at mid-levels will be a cyclonic vortex over the Atlantic, with a trough stretching into Northern Italy in the beggining of the forecast period. Satellite images as of Tuesday 21 UTC reveal a well developed cyclonic vortex within this trough. Towards the east/southeast a n inconspicuous higher geopotential fields prevail. Going to the north a brisk mid-level flow with several disturbances covers Central to Northern Scandinavia. Closer to the surface, an unseasonably warm airmass is present over much of Central Europe. This airmass is characterised by rather steep lapse rates and relative dryness although dewpoints did increase slightly over the area during the recent few days. A diffuse frontal boundary is predicted over Germany and a sharp frontal zone running from Scandinavia to Russia.

TBH I think they have a point and it could of course be that any action overnight is confined to our continental neighbours in the flatlands, however Dan's (Staplehurst) UKASF forecast may bring some of us in the extreme SE a bit of a smile:

Forecaster: Dan

Last Updated: 2012-05-01 21:34:00

Valid: 2012-05-02 00:00:00 - 2012-05-02 23:59:00

Areas Affected:

SLGT: Parts of E Anglia and SE England

Synopsis:

Low pressure centred to the west of Iberia will allow an easterly flow to become established across the British Isles, with advection of higher WBPTs during the evening hours.

Discussion:

During Wednesday evening, slight advection of higher WBPTs will provide some moisture convergence across parts of East Anglia and the far SE. This will steepen mid-high level lapse rates and generate a few J/kg MLCAPE. Given nocturnal surface inversion, it is possible that elevated storms may develop over highlighted areas as moisture plume destablises, eventually merging into a mass of rain along the occluded front.

Current thinking is that conditions are slightly less favourable than the Monday night event, but there is a chance nonetheless for some elevated thunderstorms to develop, capable of producing IC/CC lightning, and given PWAT values up to 26mm, some torrential downpours are possible, increasing the risk once again for flash flooding given the already saturated ground. Due to the elevated nature of said storms, severe weather is unlikely (with the exception of flash flooding).

Storms, if they develop, could potentially continue beyond the end of this forecast period (23z) into the early hours, but with ever-increasing saturated vertical profiles, sferic activity will gradually diminish.

No updates from SkyWarn or TORRO as yet, I'll go and find a million charts to post for you to exercise your scrolling fingers!

[Coast]

Michael Fish did mention a few rumbles of thunder on his 6.30 BBC SE Today weather forecast this morning, so are we going to get a repeat of Monday night?

21st OWS going with the Benelux countries and beyond really:

The lightning possibility ensembles are tantalisingly close at midnight:

General weather forecast (GFS) has it all to our East:

Again, the tongue of CAPE is close, offshore near Essex in the North Sea:

GFS shear has it all to the East too:

HiRLAM more towards Essex and East Anglia:

Convergence:

Plenty of rain out there:

My head says if you follow the charts it's all in Belgium, Holland and Germany, my heart says look at Monday overnight and see what sprang up from non-chart potential.

You know where to be during the late hours of today into tomorrow?????

http://www.netweathe...lightning;sess=

http://www.netweathe...ion=radar;sess=

[Coast]

Struggling to find some positive signs for later, SkewT isn't great on the Essex coast:

Can someone with some 'proper weather knowledge' tell us what they think please??

[Pixel]

Visually... very interesting to watch things develop in France today

http://www.meteox.com/h.aspx?r=&jaar=-3&soort=satradar

whether or not anything electric will get to us is indeed open to debate (-:

[Coast]

OK, I've been trying to find some chart based straws to grab at, the 'best' I can get so far are the NW Extra NMM Hi-res ones which back up the GFS with a lobe of MLCAPE and LI off Paul Sherman's house at midnight tonight. The TT Index ( http://www.theweathe.../habyhints/302/ ) is encouraging for that small area of Essex and a bit of Sussex

I suggest everyone gets around to Paul's house at about 11.00pm tonight and I'm sure that as the generous bloke he is, he will have the beers in and set up already......

My solace is that Monday/Tuesday didn't really evolve until much later in the day and not as the charts initially showed.

[legritter]

could be some embedded storms in our batch of thundery rain ,we will know me thinks come 8 /10 pm this evening ,by looking at light detector . although i did see some lightning the other night me mother in law said 3am yesterday it was flashing a lot but she never heard any thunder . will be interesting to see how fast this developes today i wouldnt be surprised to see parts of s/east and coastal south parts get something by 7pm this even going by current sat pictures and returns . could have done with a boat yesterday morning going around country lanes , i also wonder whether something interesting could set up for this sunday ,BUT thats 5 days away .heres hoping for tonight cheers

[Coast]

i also wonder whether something interesting could set up for this sunday ,BUT thats 5 days away .heres hoping for tonight cheers

General feel from GFS is a real 'no' down here!

[Suburban Streamer]

Monday was certainly a nice surprise after the charts left me feeling less than confident of seeing anything.

So if todays charts are slightly worse than Monday for tstorm potential, then hopefully the storms will be a little better. How's that for deranged logic lol? Fingers crossed

[Supacell]

I'm not feeling confident for you guys regarding tonight i am afraid. Looking at the charts it is, as Coast says, a case of straw clutching. I may be wrong, i'm no expert, but just doesn't look as good as Monday did IMO.

Today looks a fantastic day.... to be in Belgium.

[Bluebreezer54]

Certainly different conditions here today compared with Monday. Then it was a warm sunny day, today is just grey muck and currently 10.8c. I would think they may be a factor in lack of potential ?

[Eskimo]

Certainly different conditions here today compared with Monday. Then it was a warm sunny day, today is just grey muck and currently 10.8c. I would think they may be a factor in lack of potential ?

It's going to get progressively sunnier as the day goes on so it should be fine for the evening.

[Robbie Garrett]

Certainly different conditions here today compared with Monday. Then it was a warm sunny day, today is just grey muck and currently 10.8c. I would think they may be a factor in lack of potential ?

These storms are as a result of converging winds, etc and not diurnal heating. Both would provide monsters however. Most of the storms on Monday started off at 2200hrs... or so.

[Coast]

Alright here we go, this is what the Dutch think will happen during the course of today and where any action may be heading later:

Look to Belgium after dark and see if anything gets into Essex and beyond I guess.

[Coast]

We've also now got SkyWarn on board:

SKYWARN UK SEVERE THUNDERSTORM WATCH #017

ISSUED: 1130UTC WEDNESDAY 2ND MAY 2012 (GJ/SM/DH)

SKYWARN UK HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR THE FOLLOWING REGIONS:

EAST ANGLIA SOUTHEAST ENGLAND SOUTHERN ENGLAND MIDLANDS WALES SOUTHWEST ENGLAND

IN EFFECT FROM 1400UTC WEDNESDAY 2ND UNTIL 1800UTC THURSDAY 3RD MAY 2012

CONTINENTAL CONVECTION EMBEDDED WITHIN A STRONG MOISTURE PLUME ADVECTED ACROSS THE SOUTH OF THE UK OVERNIGHT

THERE IS A POSSIBILITY OF SEVERE WEATHER AFFECTING THE INDICATED REGIONS IN THE TIME PERIOD SPECIFIED. THREATS WITHIN THIS WATCH INCLUDE, BUT ARE NOT LIMITED TO:

HEAVY RAIN...FLOODING...STRONG GUSTS...HAIL...LIGHTNING

DISCUSSION:

THERE IS STRONG MODEL AND PARTNER AGENCY CONFIDENCE OF THE POSSIBILITY OF A SEVERE WEATHER RISK OVERNIGHT AND THROUGH THURSDAY. DEVELOPING CONVECTION OVER CENTRAL EUROPE AS A RESULT OF A DEEP MOIST MIXED LAYER AND STRONG VORTICITY WILL BE DRAWN ACROSS THE TOP OF A STABLE BOUNDARY LAYER OVER THE SOUTHERN HALF OF THE UK. STEEP MID TO HIGH LEVEL LAPSE RATES WILL GENERATE STRONG ELEVATED CONVECTION, PERHAPS WITH HAIL AND FREQUENT CG LIGHTNING, AND SOME INTENSE RAINFALL PARTICULARLY FOR THE EASTERN PORTION OF THE WATCH AREA THROUGH THE NIGHT. WIDESPREAD ACCUMULATIONS UP TO 20MM CAN BE EXPECTED, WITH PERHAPS LOCALISED FALLS OF 40MM THROUGH CENTRAL, SOUTHEASTERN AND SOUTHERN ENGLAND. A FAVOURABLE DIRECTIONAL SHEAR PATTERN WITH UP TO 40MPH WINDS AT THE 850MB LEVEL MAY ORGANISE STORMS, THOUGH A BROAD MCS IS A MORE LIKELY MODE FOR THE CLUSTER OF THUNDERSTORMS EMBEDDED WITHIN A MORE GENERAL MASS OF RAIN. OVERALL DLS IS WEAKER THAN MONDAY, WHICH MAY LEAD TO SLOWER MOVING CORES AND COULD ENHANCE RAINFALL AMOUNTS CONTRIBUTING TO FLASH FLOODING AND RIVER FLOODING AS A RESULT OF ALREADY SWOLLEN CATCHMENTS. PRECIPITATION IS EXPECTED TO BECOME MORE DYNAMIC FURTHER WEST, THOUGH FURTHER TRIGGERING OF CONVECTION MAY OCCUR AS A RESULT OF HIGH GROUND IN WALES AND SOUTHWEST ENGLAND. THERE IS ALSO THE POSSIBILITY OF CONVECTION BEING TRIGGERED OVER THE MIDLANDS INTO WALES DURING WEDNESDAY, AHEAD OF THE ADVECTED MCS. PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY. THIS WATCH MAY BE UPDATED OR UPGRADED.

You can be fairly sure there is going to be a lot of rain tonight and the MetO have a warning out:

UK selected warning

Rain

Issued at: 1116 on Wed 2 May 2012

Valid from: 2000 on Wed 2 May 2012

Valid to: 1200 on Thu 3 May 2012

Outbreaks of locally heavy rain will spread west across southern England and Wales this evening, overnight and into Thursday morning Totals of 20 to 40 mm are likely in places, falling on saturated ground. The public are advised to be aware of the risk of some disruption from surface water flooding.

http://www.metoffice.../?regionName=uk

Emergency advice, do not go outside without wellies in the night, when the dog needs to have a wee!!!!

[Paul Sherman]

I suggest everyone gets around to Paul's house at about 11.00pm tonight and I'm sure that as the generous bloke he is, he will have the beers in and set up already......

Unfortunately I Have no beers as I used them whilst Salivating at my first day on the Netweather 2012 StormChase

5,000 Cape Anyone

[VillagePlank]

Good Afternoon, SE Storm-Lovers,

Let's start with the skew-t,

TT gives a figure that indicates likely thunderstorms in a marginal convective environment (KI,LI). TT normally gives an indication of the severity of storms should they occur, and KI indicates how convective the atmosphere is at that point. Given exceptionally little CAPE, and positive LI, we should conclude that storms are unlikely from a convective point of view. Remember that when we talk of convection, we talk of convective heat transfer. The fact that TT is high is all we need to keep in mind - since it really isn't going to be that warm at midnight, anyway .

OK, so how do we get the air to rise up and deliver the goodies? One way is if we have shear: this basically is changes in wind strength and or direction. Here's the charts from the floor to 500hPa,

At 10m we basically have a reasonable N'ly flow, but if you look at the 500hPa chart it's a SE'ly flow and much slacker; this means we have directional shear, and strength shear - this should get the air spinning, and, by the looks of these charts, it should be East of a line from Isle of Wight to E Anglia - but S Wales should watch out, too. Winds brushing up against either at different speeds, can be summarised as vorticity (ie how strong a vortex, either up or down is likely to occur) Here you go,

Red is going up, blue is going down - the stronger the colour the stronger the vorticity

Right, so we have air rising, and potential to create thunderstorms (not severe ones, I might add - but sufficient) is this enough? As you'd expect, not quite - you can make air rise as much as you want, but it still needs fuel. In T/storms that's moisture - here's the chart,

Yep - that's right storm lovers - all that potential in NE France/Belgium is connected to us by a conveyor belt of moisture - a plume. A question most storm lovers will ask, is is it going to import? Well, as moisture makes clouds it releases heat, and we can see how the heat moves around with the following chart,

Here we can see that we are connected (see what I mean about S Wales, too?) to the continent, but only just, and the channel does seem to be within the error margin of GFS - inconclusive, then.

A chart I like to use that kinda summarises all this lot is the vertical advection charts - ie by how much is air rising, and how vigorously,

With everything else taken into account, then, I'd go for reasonable chances if the temperature advection holds (see the 12z this afternoon for updates) for Wales - although NE Wales/Manchester might only see rain, and Kent, and marginally E Sussex. Vigourous showers perhaps in N Essex, and the southern part of E Anglia.

SE Kent coast - ie Dover - is the place to be.

There's the 6z view according to me

Happy Hunting,

Edited May 2, 2012 by Boar Wrinklestorm

[dallas]

Cheers Coast and Boar, very informative

[Harry]

I wouldn't say the MetO is completely against the idea of thunder

London & South East England

Headline:

Dry at first, but some heavy showers developing later.

Tonight:

Rather cloudy with outbreaks of rain. The rain is likely to be heavy and thundery at times, but becoming generally lighter towards dawn. Minimum

[SxK]

Boar - super post - very objectively put and also very helpful for all on the forum to learn a thing or two.