Storm & Convective Discussion - 01/09/14 onwards

[Mapantz]

That's SB CAPE, not really a good measure, ML CAPE is way more widespread so more likely for storms to become more night based and more elevated than surface based.

 

To say it's not a good measure, is incorrect.

 

You've got to know many other data points before determining whether a storm will be taking advantage of a particular CAPE.

[Spikecollie]

I'm baking here in Dijon. 28c today and that makes for an uncomfortable 8 hours of teaching in classroom with no aircon! It's 22c still now and there's no air movement at all and it feels more and more humid. I think Thursday, Friday and Saturday will see storms here - I'm probably heading back on Saturday so camera at the ready for those CuNbs, but I'd like some elevated night storms to try some photos - Thursday and Friday look excellent for those!

[Greeny]

Looking juicy around my area currently for Friday.

[William Grimsley]

To say it's not a good measure, is incorrect.

 

You've got to know many other data points before determining whether a storm will be taking advantage of a particular CAPE.

Ok, I know there are loads of other factors such as high level wind speed, wind shear, upper level wind shear, lapse rates etc. but SB cape is not relevant in night time as it only occurs during the day.

[legritter]

Morning all ,nice to see the possibility of some thundery weather creeping into the UK .And with the evenings now getting darker some hopefully observed flashes ,but does look from this range a very hard call on locations and intensity ,but a real bonus for us at this time of year to get what we all crave for .best of luck to all ,Cameras and radar at the ready 

[Karl83]

Ian F did mention 'severe storms' yesterday, for Thursday night into Friday.

[Panayiotis]

Ian F did mention 'severe storms' yesterday, for Thursday night into Friday.

Yep destabilization shown perfectly on the EURO4 this morning, this will be the likely cause of the thunderstorms during the night:

Again its looking like Portsmouth to Brighton northwards will be in the firing line with some isolated storms moving north through the SW, it has been a reoccurring theme this summer.....

[Mapantz]

Yep destabilization shown perfectly on the EURO4 this morning, this will be the likely cause of the thunderstorms during the night:

Again its looking like Portsmouth to Brighton northwards will be in the firing line with some isolated storms moving north through the SW, it has been a reoccurring theme this summer.....

 

Portsmouth to Brighton? That's rather narrow lol.  If you're going by that second chart, more like Weymouth to Hastings.

[Bobby]

It looks like significant surface cape builds tomorrow afternoon with thundery showers developing across many parts of the South. Some mid-level CAPE developing on Thursday night could fuel storms through the wee hours.

 

Then even more and widespread surface cape builds on Friday afternoon with potent storms possibly in S and Central areas.

 

 

Friday

 

More fun on Saturday and possibly Sunday too

 

 

Edited September 17, 2014 by Bobby

[Andy Bown]

Could we be looking at a repeat of the night of Thursday 17th July!?

 

Just in case anyone has forgotten (how could you) storms developed very rapidly late evening and became pretty severe and widespread as they moved North overnight.

 

So, as a reminder, if the radar/detectors appear inactive during the evening, it does not mean game over!!

[Spikecollie]

It's all evolving quite slowly over here in France. Alertes oranges were put out yesterday for Aude and Herault (south) and although there has been some incredible rain in Herault and also Gard, Aude has not yet been touched. The warning has been extended until tomorrow morning as things are moving more slowly than the forecasters expected. It's the lack of storm movement that is worrying people - I have had night and day long storms down there when conditions have favoured.

 

All regions will get storms here - nothing exceptional in the main (for France), but some strong thunderstorms will be in there. Although I have experienced these many times, I never take them for granted and enjoy every moment. The instability is substantial and I think the UK will see some of this - the ML CAPE values are indeed very promising as folks have pointed out - whatever happens let's all stay safe and enjoy...

[Wilxy]

I remember the night of the 17th clearly, there was naff all on radar until suddenly an explosion of cells from the south and well we all know what happened next!

[Bobby]

Could we be looking at a repeat of the night of Thursday 17th July!?

 

Just in case anyone has forgotten (how could you) storms developed very rapidly late evening and became pretty severe and widespread as they moved North overnight.

 

So, as a reminder, if the radar/detectors appear inactive during the evening, it does not mean game over!!

 

There is plenty of mid level CAPE during the night. I think we will first see thunderstorms across the SW, S on Thursday afternoon and then spreading further N through the night and becoming elevated? Then more storms developing on Friday as the sun gets to work on the still unstable atmosphere.

 

Edited September 17, 2014 by Bobby

[Spikecollie]

There is plenty of mid level CAPE during the night. I think we will first see thunderstorms across the SW, S on Thursday afternoon and then spreading further N through the night and becoming elevated? Then more storms developing on Friday as the sun gets to work on the still unstable atmosphere.

 

And Saturday - still loads of instability and ML CAPE. I'm looking forward to a great cloudspotting trip back to the UK late Saturday afternoon! Me thinks I have storms to enjoy before that though...

[Spikecollie]

Weird afternoon here. Just had some work to do after classes but I'm going out soon to have a beer and watch the clouds go by. 27c some altocumulus castellanus beginning to appear and some cirrus virga. Free day tomorrow to cloudspot and window shop!

Edited September 17, 2014 by Spikecollie

[Karl83]

I remember the night of the 17th clearly, there was naff all on radar until suddenly an explosion of cells from the south and well we all know what happened next!

Twas a great night. But boy was I tired the rest of the weekend!

[Spikecollie]

Sferics just kicking off over here in France, some near but not too near me. An active little cell just North of Montpellier is worth watching for it's rainfall impact. It'll intensify day by day...enjoy! Still 26c by the way, and the beer was gooood - Pelforth for the initiated, and I had two...

Edited September 17, 2014 by Spikecollie

[Greeny]

A little storm has fired off the coast of Southern Ireland.

[Flash bang flash bang etc]

I remember the night of the 17th clearly, there was naff all on radar until suddenly an explosion of cells from the south and well we all know what happened next!

I was on Butser Hill near Portsmouth and saw the first strikes dropping over the channel at about 10pm. Awesome to see, forks were clearly visible but miles and miles off. About an hour later and it went nuts!

Got the green light for a few hours chasing tomorrow night around Guildford and maybe down into Hants if things all go to plan :-)

[Mapantz]

Forecasts didn't really set me alight. You'll be very lucky to catch a storm tomorrow night/Friday .. or unlucky, depending how you look at it.

[Thunderbolt_]

Hoping one might stray up here on Friday or Saturday, though I think I might be a bit too far north, to be honest... but we shall see.

Edited September 17, 2014 by ScottRichards10

[Nick F]

Have issued a forecast for Thursday, storms look mostly isolated and concentrated towards the SW during the day, but one two perhaps reaching the SE late evening/Thurs night. Friday looks to see a more widespread risk of storms across England and Wales. Given weak vertical shear both days, no organised severe looks likely, though there is a risk of local flooding.

 

Storm & Convective Forecast

Issued 2014-09-17 20:37:22

 

Valid: 18/09/2014 0000z to 19/08/2014 0000z

 

THERE IS A RISK OF THUNDERSTORMS FORECAST

 

 

Synopsis

Slow-moving upper and surface low circulation off NW Iberia will advect increasingly warm and moist airmass with high theta-w values north across Sern Britain and S Ireland over the next 24 hrs, with the easterly flow becoming increasingly unstable from the SW during Thursday..

 

... S IRELAND, S WALES AND S ENGLAND ...

 

Occluded frontal system will move NE into the far SW from 00z Thursday, marking the northern extent of warm/moist high theta-w plume advancing north out of France and Bay of Biscay. Isolated elevated thunderstorms are possible along the leading edge of plume moving north in the early hours/morning across SW UK and S Ireland. These storms capable of producing locally heavy rain leading to a risk of flash flooding.

 

For the rest of Thursday, unstable warm moist plume continues to slowly advance north across S England/S Wales - surface heating into low to mid 20s and NEly/SEly breeze convergence over S England/S Wales may support development of more widespread isolated thunderstorms, chiefly Hampshire/Wiltshire/Oxon westwards in the afternoon/early evening but one or two isolated storms perhaps reaching further east across SE England later in the evening. Given dry ground, heavy rainfall from these storms may produce flash flooding and hazardous driving conditions locally. Given weak vertical support/wind shear, no severe weather is anticipated.

 

Issued by: Nick Finnis

Edited September 17, 2014 by Nick F

[timeless]

l assume its going to be similar for saturday if the ouputs dont deviate too much? tho from what lve seen things start clearing up from saturday onwards.

 

lm assumung at least by the current GFS here that this annoying thundery weather should move on and give us a more settled picture where thundery weather is conserned.

[ancientsolar]

Blitzortung showing some a sferic off the SW Coast ~ this will be an interesting 3 days!

Courtesy of developing cells in the atlantic*

Edited September 17, 2014 by ancientsolar

[Eskimo]

             

 

Edited September 17, 2014 by PerfectStorm