18th Aug 2011 - Storm/convective Forecast Discussion And Reports

[Coast]

Go on then, I'll start a cheeky wee thread for possibilities today:

ESTOFEX have the SE covered in their forecast for the French/Belgian stuff:

Storm Forecast

Valid: Thu 18 Aug 2011 06:00 to Fri 19 Aug 2011 06:00 UTC

Issued: Wed 17 Aug 2011 21:49

Forecaster: GATZEN

A level 2 was issued for portions of France and south-western Germany mainly for severe wind gusts and large hail.

A level 1 was issued for portions of Spain, southern Portugal, France, the Alpine region, Germany, and the Benelux countries mainly for severe wind gusts and large hail.

SYNOPSIS

To the north of a broad ridge over the Mediterranean, a strong westerly flow affects portions of Europe in the wake of a short-wave trough stretching from Scandinavia to western Russia. Another short-wave trough will migrate into Central Europe during the period. This will be associated with the advection of warm and unstable air into southern Germany.

UKASF have that NE portion of England into Scotland highlighted:

Forecaster: Dan

Last Updated: 21:12 Wednesday, 17th August 2011

Valid: 00:00 Thursday, 18th August 2011 - 23:59 Thursday, 18th August 2011

Areas Affected:

SLGT: E + NE Scotland, Borders, NE England

Synopsis:

A weak upper ridge migrates eastwards to be replaced by a weak, yet rapidly-intensifying, upper trough. A warm and humid airmass with high dewpoints and ThetaW is advected across SE England behind a warm front, with a broad frontal zone.

Discussion:

Despite a warm and humid airmass being present across SE England, moderate northeasterly winds and excessive cloud cover are likely to inhibit 2m temperatures from rising above 20/21C. Along the frontal zone itself, a wave is forecast to move NEwards across CS Eng/S + E Mids/E Anglia during the forecast period, providing an intensification of rain. Some appreciable falls are likely, in the range of 10-15mm, but locally up to 40mm is possible. Given the fact that this will be falling over many hours, rather than in a short period of time, this precludes any higher threat level. Such precipitation is not expected to produce any lightning although an embedded cell cannot be completely ruled out given this type of setup.

Particular interest is given to NE Scotland southwards into NE England. A couple hundred J/kg CAPE coupled with quite a pronounced NNE-SSE convergence zone will provide the main focus for any stronger convection. A line of heavy showers is expected to develop from early afternoon onwards, and with ELT's as low as -25C, lightning is expected in stronger cells. Slack and variable surface winds will ensure such line will be slow moving, if not quasi-stationary in nature, and could give some locally high rainfall totals (potentially in excess of 40mm very locally). Under such conditions, some minor flooding is possible although exact locations are difficult to pinpoint. Meagre DLS and LLS precludes the tornado risk, although a CZ-type funnel is not out of the question.

Showers are expected to persist well into the night, probably not showing any significant signs of decay until around or after the very end of this forecast period.

A few showers are also expected across Ireland and Northern Ireland, although slightly higher geopotential heights here will limit the risk of any lightning and consequently such convection will be shallower in nature.

Looks like some convective cloud with that rain:

Small amounts of CAPE in Scotland midday:

Look where it's at its best though later:

I think this one is confined to France and maybe Scotland:

Interestingly, Kaye Forster on the BBC South East today weather at 6.30 had the rain coming into the Northern areas of Hants, Sussex and Kent later, with the dry band along the Southern coast? I'll forgive her this morning as she did do her hair nicely (and had dried it after getting out of the shower for once!!!)

[Harry]

Could be an interesting day across the south IMO - warm fronts can and have brought thunderstorms in the past.

Rain v heavy across the SW and moving in a N or NE direction.

[Coast]

Well, there seems to be indications of convective rain at least, this is Shoreham Airport near Brighton:

http://wxweb.meteost...1&submit=submit

Mind you, it should be pouring down by now according to that and we've got clear blue sky!!!

[Harry]

That Low seems to be coming closer than initially thought....my understanding was that it would move into N France, the warm front to the North and then drift NE between Kent and Benelux and move out towards Scandinavia. Based on that chart above the Low comes further North....hmmmm

It's a complex ol' day today....I wouldn't want to be a forecaster (even by their own admission they're finding this VERY difficult)

[Coast]

That Low seems to be coming closer than initially thought....my understanding was that it would move into N France, the warm front to the North and then drift NE between Kent and Benelux and move out towards Scandinavia. Based on that chart above the Low comes further North....hmmmm

It's a complex ol' day today....I wouldn't want to be a forecaster (even by their own admission they're finding this VERY difficult)

Has it all stalled?

[chionomaniac]

It is one of those days where there could be a little surprise in the SE corner this afternoon. My guess is that there will be convective potential SE of the main band crossing the country. There could also be a convective component in the southern edge of this main band as well. Already some very heavy radar signatures showing up.

[gottolovethisweather]

I have no more to add other than the fact that it's raining pretty heavily in Newbury at the moment and the date is 18TH AUGUST, coast?

Coast, is it pre-plume excitement kicking in.

Cheers

gottolovethisweather

[Harry]

Has it all stalled?

What's that? The Low or the warm front? I notice your chart says CF but I'm struggling to see a CF on any of the pressure charts

[staplehurst]

What's that? The Low or the warm front? I notice your chart says CF but I'm struggling to see a CF on any of the pressure charts

MetO have it down as a trough

[Evening thunder]

Well, we already have thundery activity pushing into South Dorset as shown here and on the Netweather Radar in association with the torrential downpours and heavy rain, which has, surprise surprise, missed me by the skin of it's teeth again.

[Summer of 76]

Interesting to note that the met office have updated their web site at just before 10am for the East of England which now refers to a developing area of rain, thundery at times and a brisk NE wind developing, earlier it was mentioning showery rain when updated at 3am.

Interesting day me thinks.

Chris

[dave reid]

heavy rain here in Bournemouth and just had a flash & rumble, just the 1 thou. Perfect airshow weather

[Harry]

MetO have it down as a trough

That's what I suspected but it did throw me

Fair bit of sferic activity developing across the S/SW now...very slow moving at that!

[NO LONGER POSTING]

Hi guys, some very very very very!!! Dark skys to the South west of me..I think it is the front approaching..Below are some pictures

Its like a wall of dark cloud moving over me..Looks like something out of war of the worlds

[chionomaniac]

Radar has the look of a homegrown MCS developing over Poole area.

[EML Network]

WOW what an amazing thread, and so many new charts for me to get to grips with, awesome stuff, think i'll be spending a large part of autumn over here trying to figure out what they all mean..if someone has some time I don't suppose anyone would be able in laymans terms be able to very briefly explain exactly what the many charts at the top of this thread are actually describing in the real world ??

[dave reid]

second flash & rumble in Bournemouth and closer than the last one :)

second flash & rumble in Bournemouth and closer than the last one

and No. 3

[toggerob]

A day for RADAR watching and keeping the plastic mac in the rucksack just incase. BBC forecast was going for the 'wave' from the south migrating northwards throughout the day, slowing as it reaches the Midlands and bringing some high precip totals between the Birmingham-Lincoln areas. North of this they mentioned convective showers breaking out in the NE and over Scotland so anything can be happening today.

[Jane Louise]

Nice sky there. Just a blanket of low cloud here with moderate rain. more on the way.Hoping to get a rumble and a flash at some point today.

[NO LONGER POSTING]

I will be some what un happen if that misses me lol..And looking at the direction of it..Looks like it is ohwell Need to go out later

[Coast]

second flash & rumble in Bournemouth and closer than the last one

and No. 3

Send it along the coast a bit please and turn it up to Gas 5!

Nice little bit of activity to the West:

[dave reid]

VERY heavy rain and another flash, Roads now turning into rivers.

[xerxes]

Away from some intense rain that affected Alton a while back the developments closing in on the IOW need watching. That's a very intense and developing convection line heading NE. Probably responsible for the Bournemouth activity

[vortex_liam]

Just brought another radar sub for a year! There is some good thundery active's inside the core of that heavy rain!

[Harry]

Miffed by the lack of a MetO warning to be honest