Convective / storm Discussion - 5th June 2014 onwards

[Chris101]

As a couple of others have said, this event is looking pretty much the same as June 2012, So i would say some average storms running through the SW through the night, and then Saturday during the day an explosive outbreak of more severe storms (possibly another supercell) running from the Midlands NEwards into Leicstershire, Lincolnshire, parts of East Anglia into the afternoon/Evening.

[Mapantz]

I never rated my chances here from day one to be honest, I'm sure they'll be a period of showery rain but it'll turn electrified as it moves further inland.

However, decent MLCAPE does push across the channel during the early hours of Saturday, elevated lightning is certainly a possibility. That MLCAPE really ramps up as it moves in to central southern, midlands, southeast, parts of the northwest..

The ELT's don't look too shabby either, see how they get colder through the day; -40 to -50C is perfect for hail production (large hail too) and of course, lightning.

Those higher dewpoints start to appear too, although not quite as high as they were showing as day or two ago, but still high nonetheless. 15C and above is usually a good thing for thundery developments (subject to other conditions of course) those dewpoints increase inland during the day, it does look particularly sticky.

The heavier rain being progged by the GFS for the Northwest on Saturday PM could be just that, heavy rain; CAPE ingredients start to disperse, but the contrasts between the air masses should produce some very heavy rain, the 850 poteq (theta e) chart shows this nicely. A large vortmax lobe across the same area too, it'll be interesting how the MO go about a warning.

Overall, I'd say Liam's map is not too far of the mark, as it stands now, anyway. It's still subject to change as we head in to the mesoscale side of it. I think some folks may get a bit more than they bargained for.

Edited June 5, 2014 by Mapantz

[Speedway Slider]

We had a fairly similar setup during Wimbledon a couple of years ago (2011?) with very moist and unstable airmass across C/S/E England, with very high dew points, very high CAPE/LI, high temperatures and an active cold front pushing through around mid to late afternoon - the result was a massive line of very active tropic like thunderstorms which rode the front SW to NE, frequent lightning, torrential rain, relatively large hailstones and lasted for a good hour or two. The primary difference I can see between then and Saturday is on that day the temperature had reached 30C by midday then as the storms were firing they dropped off to around 22C.

 

I'm very much hoping for something similar - that was an awesome day with great green hues in the sky and one storm after another riding the front. The thunder on that particular day was extremely loud and angry too.

 

This was a clip posted by a chap I am very grateful to 

 

Blimey!!!!! Just watching that, 4 years later, has given me a belly ache, butterflys in my belly and a cold sweat!!!!! Hope we don't get anything that close/violent/loud in Leicester on Fri night, Sat day....!

 

 

[Tom Jarvis]

Can we pls get a supercell storm in the Sussex area as I would love to go out and chase it lol

[radiohead]

Looks like a CAPE upgrade on the 06Z GFS for Saturday. Should get a better idea when the 06Z NMM rolls out later.

 

 

 

4pm Saturday on the 0Z vs 06Z . A slight difference of around 1,000 j/kg in places!

 

 

Edited June 5, 2014 by radiohead

[BrickFielder]

Some early thoughts for Friday into Saturday, although I must stress that its way too early to put any detail on this.

The first detail that stands out is divergence aloft moving into the UK and a high level jet approaching from the south.

 

That kind of  divergence aloft always makes me think about an MCS. MCS in my mind tends to be lots of cloud and heavy rain with a bit of lightning and thunder thrown in.

 

It has been suggested that this is a typical spanish plume, by that I mean that the source air flow is across Spain where it gets lifted by the iberian plateau to create an elevated mixed layer. Typically from this storms are not surface based but can give a good high level lightning show. I have mixed feelings about whether this is true. Low level flow is a bit mixed.

This in contrast to the steering flows at 850hpa and 500hpa which tend to just clip Spain, but it may make a difference in moisture levels in the lowest levels and whether storms are surface based.

 

Now four charts to compare and a challenge for you.

 

So the question is why does the convective precipitation not overlap with the highest lapserates and mixed layer Cape . Why might the deep layer shear be more westerly based. Clues i think are in the air flows at different levels and positioning of the front and vorticity differences.

 

Finally a proper FI (Fantasy Island) chart or just plain scary.

 

 

Which suggests high cloud tops for the UK (more chance of lightning) , very unstable atmosphere (think strong updrafts and hail) , wind speed shear going up the atmosphere and some directional and speed shear in the lowest level.  Not quite a classic super cell , tornado SkewT due to lack of directional shear aloft, but impressive for the UK.  It is however at this range almost certainly a misrepresentation of how the air profile will be on Saturday. 

 

The typical spanner in the works for this scenario might be storms developing over France overnight and leaving dull, damp conditions under stratiform, cloudy skies  during early the next day which takes too long to clear.  So it could still be a complete bust,but something tells me that the divergence aloft will have its say.  Biggest threat might be localized flooding.

 

[Dancerwithwings]

Yesterdays 06z Cape 14:00 Sat

 

 

Todays 06z cape 14:00 Sat

 

 

Then Upgrade for the North it looks.

 

[Speedway Slider]

11:06 Thursday.....

Met Office Updated Warning For Saturday Now Modified...

 

The word Thunderstorm/s have been totally removed from the forecast!! Now only saying heavy, thundery downpours......

What's going on!???

[Neilsouth]

BBC Forecast just said that the south east may remain dry and humid

[Liam J]

Meto updating the warnings page, still with low confidence in the forecast and which areas will see the worst of the weather.  

 

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=map&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1401922800

Edited June 5, 2014 by Liam J

[Speedway Slider]

Right my friends........ What's?

 

The difference between surface based and elevated/high based thunderstorms?

Is it the types of lightning produced, or storm longevity of storms, intensity, or something else......?

[Liam J]

Weather impact matrix, likely impact pretty high but confidence remains very low...

Edited June 5, 2014 by Liam J

[Paul]

Jo's just written a blog about the storm threat this weekend:

http://www.netweather.tv/index.cgi?action=news;storyid=5935;sess=

[NUT]

Still looks incredibly close for my area. Seems we still just miss some juicy CAPE although it's a close run thing. Argh!

[Dancerwithwings]

Off topic; Was it just me then or did N/W site just go down?

[Harry]

Off topic; Was it just me then or did N/W site just go down?

 

Yep (well the forum anyway)...seems to be back up now

[Jan]

yes it went all funny, pages not complete etc, thought it was me

 

Just watched the latest forecast on the Beeb, 'some nasty thunderstorms for Saturday'

Edited June 5, 2014 by Jan

[Mapantz]

Off topic; Was it just me then or did N/W site just go down?

I've had a problem with the forum off and on all week, the forum doesn't render properly, so I cannot see or post anything.

Meto updating the warnings page, still with low confidence in the forecast and which areas will see the worst of the weather. http://www.metoffice.gov.uk/public/weather/warnings/#?tab=map&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1401922800

Don't let William Grimsley see that, all hell will break loose! ;)I'm sure it'll update again though. Edited June 5, 2014 by Mapantz

[Harry]

Let's not forget that the MetO really leave a lot to be desired in respect of convective forecasting...take two weeks ago for example, swathes of England and Wales under a yellow warning, for much of the Midlands/EA/SE England to be removed the day in question. Within hours storms erupt in and affect the very areas cut out of the warnings, whilst those under yellow warning were largely unscathed. El Brummo was another prime example of woeful forecasting - supercells had been considered likely for the West Country/Midlands/N England for days and days and their warnings scantily inadequate until the storms were already causing damage.

 

Stick to advice on this forum given by the likes of BF, Nick F & Co who know their stuff!

[Nick L]

Let's not forget that the MetO really leave a lot to be desired in respect of convective forecasting...take two weeks ago for example, swathes of England and Wales under a yellow warning, for much of the Midlands/EA/SE England to be removed the day in question. Within hours storms erupt in and affect the very areas cut out of the warnings, whilst those under yellow warning were largely unscathed. El Brummo was another prime example of woeful forecasting - supercells had been considered likely for the West Country/Midlands/N England for days and days and their warnings scantily inadequate until the storms were already causing damage.

 

Stick to advice on this forum given by the likes of BF, Nick F & Co who know their stuff!

 

Fully agreed. The Met Office were appalling with the last thundery outbreak. It's as if they issue warnings at 11am and then just switch the computer off for the rest of the day! They seem to have a problem with convective weather.

[Dancerwithwings]

yes it went all funny, pages not complete etc, thought it was me

 

Just watched the latest forecast on the Beeb, 'some nasty thunderstorms for Saturday'

That's not the word i would use

[iamgazza]

Let's not forget that the MetO really leave a lot to be desired in respect of convective forecasting...take two weeks ago for example, swathes of England and Wales under a yellow warning, for much of the Midlands/EA/SE England to be removed the day in question. Within hours storms erupt in and affect the very areas cut out of the warnings, whilst those under yellow warning were largely unscathed. El Brummo was another prime example of woeful forecasting - supercells had been considered likely for the West Country/Midlands/N England for days and days and their warnings scantily inadequate until the storms were already causing damage. Stick to advice on this forum given by the likes of BF, Nick F & Co who know their stuff!

Agreed - I'm not fussed if we have METO on board or not when it comes to this stuff. Interesting coouple of days model watching hopefully resulting in a cracking (See what I did there) weekend showdown.

[Summer Sun]

Updated warning area for the met office for Saturday removes Devon and Cornwall along with parts of west Wales

 

 

Issued at: 1053 on Thu 5 Jun 2014 

Valid from: 0300 on Sat 7 Jun 2014 

Valid to: 2345 on Sat 7 Jun 2014

 

Heavy, thundery rain is expected to affect parts of the UK on Saturday. The public should be aware of the potential for localised flooding due to the intensity of these downpours although at this stage the location of the heaviest rainfall remains uncertain.

 

Chief Forecaster's assessment

 

Warm, humid air will be pulled northwards from France and Spain late on Friday and during Saturday. Within this air mass, there is an increasing likelihood of heavy, thundery downpours breaking out. It is likely that many places within the current broad warning area will miss the worst of the storms, but it will prove difficult to highlight the areas most at risk until nearer the event itself.

 

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=warnings&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1402095600&regionName=uk

[Jan]

That's not the word i would use

That's what he said, 'nasty'........ I get told by some that I am a misery when I say there are storms on the way, it's like Christmas can't wait for it all to start happening. I missed the storms here on Merseyside the other week, hopefully Saturday will deliver

[Speedway Slider]

I've had a problem with the forum off and on all week, the forum doesn't render properly, so I cannot see or post anything.

Don't let William Grimsley see that, all hell will break loose!

I'm sure it'll update again though.

 

 

I've had a problem with the forum off and on all week, the forum doesn't render properly, so I cannot see or post anything.

Don't let William Grimsley see that, all hell will break loose!

I'm sure it'll update again though.

Yep, me to...took 8 goes yesterday to make a post stick.. Seemed like the forum lost all its formatting and html coding....seems better now..