Convective / Storm Discussion - 21st May 2014 onwards

[Nick F]

Although GFS doesn't looks too interested in the thunder tonight, as that mass of heavy rain moves out of France, Met Office UK forecast outlook does mention embedded CBs and isolated TS spreading in across the SE tonight. But, as always in these types of set-up, when we are relying on storms spreading out of France or destabilisation overnight, nowcasting is the best tool to nail down where is mostly likely to see a show.

 

So, for now, we can only mention 'potential' rather than 'certainty'. A look the GFS charts other than CAPE does show potential, a plume of warm moist air spreading north across France and Benelux clips SE and E Anglia later, cold front moving N and E across France also moves across the SE corner of the UK ... which combined with jet causing divergence aloft ... could allow sufficient forced ascent of the plume to allow storms to reach S/SE England,  while the occluded front attached further west moves the heavy rain north across England and Wales Thurs morning.

 

 

Vertical Velocity charts show plenty of uplift spreading north out of France this evening:

 

 

Once this thundery rain clears north tomorrow morning, warm and humid airmass follows from the south across southern England, Mids and E Anglia, so likely sunshine, with temps reaching 22C, will help steepen lapse rates and build several 100 j/kg CAPE by the afternoon, as shown by GFS, so hoepfully we should see some scattered storms develop by the evening here. Potential for some large hail, towards the east - where vertical shear will be strongest near the jet streak moving north over Benelux and the N Sea.

Edited May 21, 2014 by Nick F

[lassie23]

SHOCK FORECAST: Worst thunderstorms in 50 years to rip through Britain THIS week!

 

Jonathan Powell, forecaster for Vantage Weather Services, said: "Fierce thunderstorms will tear across the country bringing torrential downpours and violent gusts.

 

I have discovered why many people's thunderstorms have vanished this week! It's because the Daily Express and Jonathan Powell said it was going to thunder!

Edited May 21, 2014 by lassie23

[Jane Louise]

SHOCK FORECAST: Worst thunderstorms in 50 years to rip through Britain THIS week!

 

Jonathan Powell, forecaster for Vantage Weather Services, said: "Fierce thunderstorms will tear across the country bringing torrential downpours and violent gusts.

 

I have discovered why many people's thunderstorms have vanished this week! It's because the Daily Express and Jonathan Powell said it was going to thunder!

Seen it already lol No suprise there when it comes to the Express it gets sillier and sillier.   Best to stick to Netweather.

[Harry]

Seen it already lol No suprise there when it comes to the Express it gets sillier and sillier.   Best to stick to Netweather.

 

Never a truer word JL!!

[Dancerwithwings]

Seen it already lol No suprise there when it comes to the Express it gets sillier and sillier.   Best to stick to Netweather.

Yes i hear that Nick F ^^^^ ain't too bad

[lassie23]

Seen it already lol No suprise there when it comes to the Express it gets sillier and sillier.   Best to stick to Netweather.

Anything is better than the Daily Express, (maybe not metcheck) but the paper kind of curses things! Hundred days of snow! We have got the whole summer for thunder storms though, so nobody should get too disappointed this week!

[Marcus_surfer]

SHOCK FORECAST: Worst thunderstorms in 50 years to rip through Britain THIS week! Jonathan Powell, forecaster for Vantage Weather Services, said: "Fierce thunderstorms will tear across the country bringing torrential downpours and violent gusts. I have discovered why many people's thunderstorms have vanished this week! It's because the Daily Express and Jonathan Powell said it was going to thunder!

LOL

[Harry]

Is (CAPE) static? I mean if it builds over Leicester, it stays over Leicester, it doesn't get blown around/move with a front, and the weather/cloud/rain moves into an area with cape or without cape? Do you see what I mean.....?

 

CAPE itself is not a thing, but a marker signifying how air behaves. As airmasses/parcels move, then CAPE does too. Think of it almost like temperature in a way - temperature is not of itself a thing, merely a marker as to the average heat energy within a particular parcel of air. If hot air is blown east, it moves east. Similarly, if the nice warm humid air near the surface does not move, but cold air higher up in the atmosphere is blown over the top, CAPE builds (even though air near the surface has barely moved at all).

 

So in answer to your question, CAPE is certainly not static and will change every time air moves (whether at ground level, mid levels or upper levels)

[Jane Louise]

I always remain optimistic I just can't help it lol. It's the excitement leading up to it also whether any of us will get something when the potentials there. Even on a normal day and the clouds look stormy I'm forever thinking and saying that a storm could come along and that it can happen when its not even been forecast. Yes we have the rest of the summer and Autumn or even winter yet Here's to a most excellent, exciting, awesome and astounding storm season 

[Harry]

Anything is better than the Daily Express, (maybe not metcheck) but the paper kind of curses things! Hundred days of snow! We have got the whole summer for thunder storms though, so nobody should get too disappointed this week!

 

Lol...speaking of metcheck just had a goosey-gander and this is an extract from their take on tonight;

 

OK, so back to the scenario and today it is all about Central and Western France where a cut-off low and long-wave trough are residing over the Eastern Atlantic. The centre of this low then disengages and spins quickly North. Within this flow, a plume of steep mid-level lapse rates will push North. Sure, the temperatures at the moment aren't anything like we would see in mid-Summer, but the airmass is so unstable it will allow storms pushing in from the continent to survive longer across parts of Kent, Essex and later Sussex and Norfolk. 

[Dancerwithwings]

Anything is better than the Daily Express, (maybe not metcheck) but the paper kind of curses things! Hundred days of snow! We have got the whole summer for thunder storms though, so nobody should get too disappointed this week!

I know before anybody says it, it would never happen.... selling papers is there only objective...headlining.... Drizzle....doesn't do it.

 

But if the Daily Express mentioned 100 days of drizzle... it would be just the best summer ever...

[BrickFielder]

 I think its too early to forecast much about tomorrow.  This evening we might have a few storms clipping the east coast as a trough in the warm sector clips the coast.  Models dont really agree on the positioning, with the NMM suggesting this might be out to sea. So a possibility of an off shore light display, although I am not convinced.

Overnight a front moves through giving some moderate rainfall and by ealy morning is across the north midlands and Wales. It looks like the sun breaks through the cloud over very southern areas by mid morning with some cloud bubbling up as a result.

The upper level jet is to the east of the country as are the steepest mid level lapse rates and although there are signs of low level wind convergence across east anglia , low level moisture arrives late in the day.

 

 

Convection does not look like over lapping with any appreciable sheer either except perhaps the very east. Forecast SkewT's suggest a cap at 800hpa which only relaxes later on.

 

Over all shifting things 50 to 100 miles east or west will make a big difference. Speeding up the clearance of the front  or changing its orientation slightly will also change the possibilities. So at this point the models can give you a hint of possibilities, but we could also easily end up with no storms tomorrow. So its too early to tell at the moment.

 

 

[Jane Louise]

Oh, thank you BF I guess we will have to wait and see  I do have a little convection here at the moment Lol. I guess we'll all be busy watching the radars tonight just in case one pops up out of nowhere.

[legritter]

Good morning ,certainly going to be an interesting evening, night, and thursday day ,with finer details still to be agreed .But having just looked at current radar and SAT returns i personally think our incoming weather system is already a couple of hours ahead of what was forecast last night and earlier in this mornings broadcasts on BBC .Some very high rainfall totals and as regards embedded storms some places getting the bees knees no doubt .Lets hope this system does not stall or pivot too much as we all know flooding is a hell if it affects you .its going to be interesting watching todays updated forecasts and the met office will soon probably update their severe weather pages .already some storm potential showing up much further down over France  ,so chins up and lets wait and see what the weather Gods bring ,catch up with you all later ,cheers .

[Speedway Slider]

CAPE itself is not a thing, but a marker signifying how air behaves. As airmasses/parcels move, then CAPE does too. Think of it almost like temperature in a way - temperature is not of itself a thing, merely a marker as to the average heat energy within a particular parcel of air. If hot air is blown east, it moves east. Similarly, if the nice warm humid air near the surface does not move, but cold air higher up in the atmosphere is blown over the top, CAPE builds (even though air near the surface has barely moved at all). So in answer to your question, CAPE is certainly not static and will change every time air moves (whether at ground level, mid levels or upper levels)

Thanks, so how big/small is a parcel of air??

[Nick L]

Thanks, so how big/small is a parcel of air??

 

It's not a defined quantity. The units of CAPE (and many other quantities) is per kg, so it doesn't change depending on the size of the air parcel. Air parcels are just a concept used to gain an understanding of physical processes governing the atmosphere.

[lassie23]

This forecast up date from weatherweb.net does sound promising for some, regarding thunder tonight! Especially over East Anglia, London and the Southeast! Heavy downpours with 20 to 30 mm possible! The Wednesday look ahead video on the home page is 9minutes  long, the 'thunder talk' , starts at 7minutes onwards!

 

Still not biblical Daily Express thunder, but thundery rain never the less! I think this is what the 'forecasters' at Metcheck were banging on about Harry!

 

http://www.weatherweb.net/wxwebtv2.php

Edited May 21, 2014 by lassie23

[Jane Louise]

On Twitter one of my tweets mentions an outbreak of severe storms over France and Benelux. Let us all jump in a boat and go and watch them Lol. Maybe after all, members in the SE will see something even if its looking out to sea.

[Lauren]

This forecast up date from weatherweb.net does sound promising for some, regarding thunder tonight! Especially over East Anglia, London and the Southeast! Heavy downpours with 20 to 30 mm possible! The Wednesday look ahead video on the home page is 9minutes  long, the 'thunder talk' , starts at 7minutes onwards! Still not biblical Daily Express thunder, but thundery rain never the less! I think this is what the 'forecasters' at Metcheck were banging on about Harry! http://www.weatherweb.net/wxwebtv2.php

Are you saying weatherweb is the Express of the internet?

[Harry]

Thanks, so how big/small is a parcel of air??

 

I'm no meteorologist so probably best something else steps in - but CAPE is measured in J/Kg, i.e energy (joules) for a kilogram of air (if that's any help)

[lassie23]

Are you saying weatherweb is the Express of the internet?

No, LOL  Simon is a pretty good forecaster and level headed too! He detests The Daily Express Btw! His forecast is for thundery rain tonight, not the worst storms for 50 years! Sorry for the confusion, did I balls up my post!

Edited May 21, 2014 by lassie23

[paul m]

On Twitter one of my tweets mentions an outbreak of severe storms over France and Benelux. Let us all jump in a boat and go and watch them Lol. Maybe after all, members in the SE will see something even if its looking out to sea.

AWW Jane are you inviting us all out on a date......

After the misses I have had this week, I think I may go APE!

I am with you on that one.. Yesterday was just horrid

[A.J]

well for what it's worth, the 06z GFS is not very inspiring for overnight action. Maybe a kent clipper, but the majority of the energy will be across the water affecting the benelux countries. Not much convective energy in the atmosphere generally speaking for the south of the UK, maybe a lobe of slightly more instability over the far south west...In fact, some areas (central southern england) may even stay relatively dry overnight.....again, based on the GFS 06z run

[Harry]

well for what it's worth, the 06z GFS is not very inspiring for overnight action. Maybe a kent clipper, but the majority of the energy will be across the water affecting the benelux countries. Not much convective energy in the atmosphere generally speaking for the south of the UK, maybe a lobe of slightly more instability over the far south west...In fact, some areas (central southern england) may even stay relatively dry overnight.....again, based on the GFS 06z run

 

Hi AJ, if you scroll back through the posts you'll see Nick F has done an analysis as too has BrickFielder.

[East_England_Stormchaser91]

Hate to be a killjoy, but I can see this being game over already! that precip is doing its swerving action as per usual. 

 

Unless anyone wants to jump on the eurotunnel now? !

Edited May 21, 2014 by East_England_Stormchaser91