End of the week & weekend storm risk

[East_England_Stormchaser91]

Very cloudy William. Let's hope it hasn't chucked the spanner in the works for things later on. I wouldn't be having my hopes up too much in all honesty, this is looking quite mediocre to say the least. Hope I'm wrong. 

[William Grimsley]

3 minutes ago, ajpoolshark said:

what you have their is a cirrus veil with some patchy Ac, Ac Cas at a stretch which isn't towering...nothing really that would have me jumoing up and down in excitement..best to wait a few hours to see if anything develops over northern France, but at the moment 'all is quiet on the western front'.....some showery rain over biscay and western france with the odd lightning flash over northern Spain (something which is pretty much seen every day from May to October)

Sorry AJ, but the photos don't do it justice, they are towering very well my friend!

@East_England_Stormchaser91, have you not seen what the photos show? Massive towering Altocumulus Castellanus cloud!

Edited May 6, 2016 by William Grimsley

[A.J]

those are not 'massive towering Ac Cas cloud'.!......a sense of realism and perspective is needed William....either that, or I'm looking a a different set of photos.....nothing of note on visi-sat imagery either, just mainly cirrus with the odd clump of Ac

[Nick F]

Storm & Convective Forecast

Issued 2016-05-06 16:37:19

Valid: 06/05/2016 18z to 08/05/2016 06z

DAY 1 & 2 CONVECTIVE OUTLOOKS

Synopsis

A deeply-amplified upper trough axis will be slow-moving just west of the British Isles down across Iberia over the next few days. Warm conveyor in the low to mid-levels will spread north ahead of this upper trough across France and western Britain over the next 24-48 hrs, while temperatures above this cool with presence of upper trough to the west. Combine this with a plume of steep lapse rates spreading north from France and increasing lift from falling heights from the west, isolated to scattered storms are likely mainly across the west over the next few days.

DAY 1 CONVECTIVE OUTLOOK UNTIL 06z SAT 7TH

... CHANNEL ISLANDS, SW/CENTRAL S ENGLAND, WALES, MIDLANDS, NW ENGLAND, IRISH/CELTIC SEA ...

Isentropic lift (upglide of warm air above cooler air) of warm conveyor spreading north ahead  of a surface warm front spreading north across S/W UK and Ireland overnight will, with help of a weak disturbance running north, generate some mid-level convection, bringing a risk of local heavy downpours and perhaps some isolated elevated thunderstorms overnight to Channel Islands, SW and perhaps central S England, Wales, Midlands, NW England, Irish/Celtic Sea areas. Therefore a low risk of localised flooding where any storms pass.

DAY 2 CONVECTIVE OUTLOOK 06Z SAT 7TH TO 06Z SUN 8TH

...  SW and CENTRAL S ENGLAND, WALES, W MIDS, NW ENGLAND ...

Ongoing isolated overnight elevated showers and storms should clear during the morning. In its wake, cloud breaks allowing heating of increasingly moist southerly flow (dew point reaching 11-13C) beneath steep mid-level lapse rates will create an increasingly unstable surface airmass across the above areas. GFS perhaps overdoing instability due to dew points a couple of degrees too high, with more realistic ECM indicating 300-800 j/kg in the afternoon. Falling pressure/heights, local breeze convergence setting up and upslope SEly flow across western hills will all help in sparking a few isolated thunderstorms during peak heating in the afternoon. Deep layer shear is looking weak ... less than 30knts, so storms are unlikely to organise enough to bring a risk of organised severe weather. Given CAPE values / energy available, a stronger storm may produce strong enough updrafts to generate marginally large hail (1-2cm). But given it's an isolated risk, have only issued a MARGINAL risk. Otherwise, storms may be accompanied by frequent cloud-to-ground lightning, gusty winds and high spot rainfall totals leading to flash flooding.

[knocker]

10 minutes ago, ajpoolshark said:

what you have their is a cirrus veil with some patchy Ac, Ac Cas at a stretch which isn't towering...nothing really that would have me jumoing up and down in excitement..best to wait a few hours to see if anything develops over northern France, but at the moment 'all is quiet on the western front'.....some showery rain over biscay and western france with the odd lightning flash over northern Spain (something which is pretty much seen every day from May to October)

It could even be As as we have here. Fairly obvious on the Camborne sounding although there is some mid level instability.

[East_England_Stormchaser91]

7 minutes ago, William Grimsley said:

Sorry AJ, but the photos don't do it justice, they are towering very well my friend!

@East_England_Stormchaser91, have you not seen what the photos show? Massive towering Altocumulus Castellanus cloud!

William buddy, it isn't them that produce the goods, I'd be more convinced if it was a humdinger of a CB exploding over the channel, then I'd be wetting my pants! 

As AJ has said mate, a sense of realism and open approach to the nature of storms is needed. I don't want you getting upset I case nothing actually comes to fruition, or everything shifts off to the east etc. 

We have all summer yet. If this was in July, it would've been no doubt substantially better. Patience. 

[Harry]

8 minutes ago, William Grimsley said:

Sorry AJ, but the photos don't do it justice, they are towering very well my friend!

@East_England_Stormchaser91, have you not seen what the photos show? Massive towering Altocumulus Castellanus cloud!

This is the sort of thing you want to see....(taken on different days in 2015)

[William Grimsley]

12 minutes ago, ajpoolshark said:

those are not 'massive towering Ac Cas cloud'.!......a sense of realism and perspective is needed William....either that, or I'm looking a a different set of photos.....nothing of note on visi-sat imagery either, just mainly cirrus with the odd clump of Ac

Like I said, the photos do not do it justice... Pffft.

[William Grimsley]

5 minutes ago, Harry said:

This is the sort of thing you want to see....(taken on different days in 2015)

Yeah, not far off that to the west now.

[Harry]

6 minutes ago, William Grimsley said:

Yeah, not far off that to the west now.

Seriously?? That's better going than I had anticipated.

If I recall correctly, the first photo was taken with temps of 26-27C and CAPE levels in the region of 1,500-2,000 J/Kg, whilst the second two photos were taken on 3 July when the entire SE quarter erupted under MLCAPE of 2,500-3,000 J/Kg.

Edited May 6, 2016 by Harry

[Weatherbimbo]

Hi all its been a while....

 

I have since changed from an apple device to an android and I belive the site has been updated since last year.

 

Now, is it just me or is the fact you can't see people's location without clicking on their name really frustrating. 

 

With posts like; it's warm and muggy HERE, Impressive CG strikes HERE....etc 

Where is HERE????

 

Or am I completely missing something??? 

[richep]

Going by the BBC forecast, there's nothing to get that excited about for us down here William mate. Hopefully proved wrong and we get something , but main threat is further out west tonight and if anything noteworthy storm wise will be reserved for more northern areas tomorrow, maybe a few showers around these parts, but probably getting all worked up for a disappointment.

[Speedway Slider]

1 hour ago, Weatherbimbo said:

Hi all its been a while....

 

I have since changed from an apple device to an android and I belive the site has been updated since last year.

 

Now, is it just me or is the fact you can't see people's location without clicking on their name really frustrating. 

 

With posts like; it's warm and muggy HERE, Impressive CG strikes HERE....etc 

Where is HERE????

 

Or am I completely missing something??? 

I'm an android jockey as well, but quite experienced.... I noticed the locations missing ages ago, but assumed it may be A privacy issue....

 

[TropicThunder]

Looks like a no-go for tonight, still plenty more opportunities to come.

[Mapantz]

1 hour ago, Weatherbimbo said:

Hi all its been a while....

 

I have since changed from an apple device to an android and I belive the site has been updated since last year.

 

Now, is it just me or is the fact you can't see people's location without clicking on their name really frustrating. 

 

With posts like; it's warm and muggy HERE, Impressive CG strikes HERE....etc 

Where is HERE????

 

Or am I completely missing something??? 

The old skin still shows the locations. Scroll down to the bottom and click 'theme'

[Ben Sainsbury]

If I was to expect any storms to form overnight, I expect them to form on the North Coast of France and move NNW'wards. Almost experimental!

[Wilxy]

I Love evenings like this!

Lovely looking sky with some hot air balloons getting close to the house

[MattTarrant]

Pretty decent 

Edited May 6, 2016 by MattTarrant

[Cornishdave]

Not sure what William is seeing, but the sky in Exeter from all directions is as per the pics above with the hot air balloons, there's a thin layer of cloud which you can see the sky through, hope people get storms but not sure how likely it is here tonight, bonus is the fact it's a beautiful eve, good luck everyone 

[LeeKay]

In a Mick Dundee voice....classic

Anyway thanks to Nick for a great outlook, and again the banter is top notch. Have a nice weekend everyone.

[Costa Del Fal]

Thought I would throw in my two pence worth!

Very low risk tonight in my opinion. Fairly good agreement across the model suits of some organised precipitation brushing west Cornwall and the Isles of Scilly towards Ireland overnight. Could be some heavy bursts but I have my doubts re: proper thundery weather. Not much instability aloft it seems and it is not really until tomorrow that the core of the theta-e plume reaches us. Cooling air high above and lowering heights as the low pressure encroaches ever so closer may favour a little something as warm air continues to be drifted up. However I cannot really see anything to shout actual thunderstorms; more the odd flash and rumble at best, rather like recent blitzortung maps are showing around the Bay of Biscay/Iberia. <20% risk for any proper thunderstorms in my opinion. The best risk being for the Scilly Isles and Ireland. 

Early tomorrow morning, a few showers/cells may initiate somewhat further East and/or drift up from N France but again a low risk and not really worthy of much discussion in my opinion. Nonetheless perhaps a little precipitation for Devon, Somerset and perhaps Bristol/Gloucs, Herefordshire and S Wales. But again thunder risk <20% imo, perhaps even <10%. 

I think the best interest of the weekend will be tomorrow afternoon. Some outputs look quite dry for Sunday at present, even though some charts such as CAPE advertise decent instability. The question tomorrow will be how much break in the cloud there will be but quite a few models going for initiation in the S Midlands and S Wales. Pretty much north of the M4 being a good guideline. The eastern most extent of this remains an issue. Some models like the NMM favouring something for the E Midlands but best agreement looks to have a focus mostly Leicester and westwards in my opinion. I am particularly interested in an area of convergence which looks to set up over the W Midlands region tomorrow afternoon (late on/early evening) as this may provide a focus and additional forcing to utilise the instability and surface heating. Hi res models like the NMM and Arome going for this. Exact placements inevitably likely to change but pretty good agreement on the best chances of something occuring being around here and then drifting north/north north westwards towards N Wales and NW England. Parts of Yorkshire and areas around the Pennines such as Leeds not without question of something either but as earlier comments here and elsewhere have suggested, somewhere around Cheshire/Wirral towards Lancashire probably at a good shout of something. 

I am a little doubtful however as to how widespread some models are showing precipitation to be and I would not be surprised if activity (if any of course!) is quite well scattered, even isolated, particularly away from regions of convergence. Cloud cover etc all making an impact. Any events from overnight tonight may make key differences too. 

Nonetheless, whilst some elements such as shear are not particularly favourable, any thunderstorms could be fairly intense for a short while. Storms may not move overly fast either as upper winds don't look too strong. Not expecting much if any major organisation of storms. Certainly no July 3rd 2015 if you ask me but that is not to say if caught under a storm, it will not be potent for a bit.

Perhaps highest risk areas tomorrow is a corridor running from Oxford towards Birmingham and Worcester, up towards Stafford/Shrewsbury then Chester with perhaps another focus being Derby, through towards Manchester and Lancashire. Activity perhaps starting to weaken by the time it reaches Cumbria. Perhaps a 3rd area of interest aided by uplift from the Brecon Beacons through towards Snowdonia way? All pure guesswork this bit but worth a guess anyway I feel. 

All storms generally fizzling by late evening. A low risk of some imports into southern England again overnight into Sunday, perhaps especially around Dorset and the IoW, which may drift NNW towards S Wales and the Midlands again but a pretty low risk that imo at the moment.

All the above could end up totally wrong but I wish those looking for a thunderstorm the best of luck and for those who do not want one, a pleasant dry day! 

Edited May 6, 2016 by Costa Del Fal

[Supacell]

Nice post Costa, I am pretty much in agreement with that. It is going to come down to looking at the charts and skies tomorrow I feel. It looks like a case of low risk in any one spot but if a storm can break out then it could be quite intense. As you say the best areas look to be Midlands, NW England, N Wales and areas around the Peak District and Pennines.  

[Convective]

These forecasts aren't exhaustive and will be updated as and when required, but here's my take on tonight's (low) chance, and tomorrow's better chances.

[weatherobsuk]

Northern Africa the place to be for lightning strikes tonight, a few popping up in the Biscay Coast 

https://www.lightningmaps.org/realtime?lang=en#m=sat;r=0;t=3;s=0;d=2;a=2;dc=0;o=0;n=0;y=46.9653365496921;x=2.98828125;z=5;

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Sat 07 May 2016 - 05:59 UTC Sun 08 May 2016

ISSUED 20:31 UTC Fri 06 May 2016

ISSUED BY: Dan

Elevated convection is likely to be ongoing across parts of Wales / Midlands and/or SW England, perhaps as far east as The Wash, on Saturday morning, drifting NNW-wards. In its wake, provided there are sufficient breaks in cloud cover to allow insolation, then 800-900 Jkg-1 may allow isolated thunderstorms to develop during the afternoon and early evening, especially within the SLGT. It appears timing is crucial between the passage of a shortwave trough and maximum solar heating, with an earlier arrival shifting the focus for initiation farther north and probably at an earlier time. It is worth stressing that these thunderstorms are likely to be fairly isolated, with a good part of the highlighted areas likely to remain dry - had storms been expected to form more widely, then this forecast would be upgraded to MDT.

20kts DLS is marginal but may allow some organisation of any isolated thunderstorms that do develop, although the overall risk of severe weather is considered fairly low, with the main threat being from minor surface water issues from heavy downpours (given PWAT 20-25mm). Given expected CAPE and some organisation, then hail up to 2.0cm in diameter is possible from any strong cells that develop.

There is also scope for further elevated convection, in a messy fashion, to either be imported or develop in-situ across Hampshire / IoW / Dorset / Devon on Saturday night, drifting NW-wards towards Wales. Once again, uncertainty exists concerning coverage and lightning frequency, otherwise there would be scope to upgrade Channel coasts to SLGT.

http://www.convectiveweather.co.uk/forecast.php?date=2016-05-07