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Convective Storm/Discussion thread - 11/06/16 onwards

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Feels like groundhog day here. Another morning with leaden skies and relentless drizzle. Plus side it looks like it may clear faster than yesterday, so always a chance of some homegrown storms later on. Pretty sure we will miss anything that sprouts up in the channel or over France.

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good morning all, well, things not going to forecast, lol.  due to be cloudy but dry, maybe a shower around 8pm, actual, very dull, cloudy, heavy drizzle, feeling fresh, no fuel for any thunderstorms here

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*Upgraded to a MODERATE chance of thunderstorms, some may be SEVERE*

Day 1 Convective Outlook

VALID 06:00 UTC Thu 23 Jun 2016 - 05:59 UTC Fri 24 Jun 2016

ISSUED 08:41 UTC Thu 23 Jun 2016

ISSUED BY: Dan

UPDATE 08:40 UTC Early convection beginning to clear eastwards this morning across East Anglia / SE England, leaving a legacy of extensive low cloud, but this should begin to thin and break at times by the afternoon to give some hazy sunshine. Surface dewpoints are already 17-19C - and may climb 1-2C through the day - which combined with any surface heating that can develop could yield 700 - 1,000 Jkg-1 MLCAPE. Isolated to well-scattered thunderstorms should develop late afternoon along areas of low-level convergence, particularly the N-S orientated cold front near A1 corridor. Strong DLS should allow organisation, perhaps into supercells during first 1-2 hours, but eventual growth into a line seems probable as the risk transfers NE across East Anglia / Lincolnshire with time through the evening. Also a risk of further imported thunderstorms from the English Channel, although this signal less obvious than compared with yesterday. SLGT has been expanded in size, with a MDT issued to areas with a better chance of sfc-based convection later today. A SVR has been issued to cater for the risk of hail up to 2.5-3.0cm in diameter (particularly during the first couple of hours of initiation), strong, gusty winds and the ongoing flash flood risk given saturated ground from thunderstorms last night. The tornado threat is fairly low, but not zero. This does not mean everywhere within the SVR will experience severe convective weather, but that the environment is favourable for the strongest cells to pose a risk of some severe weather

Atlantic upper trough will continue to track eastwards through Thursday, while a high WBPT low-level airmass covers the southeastern quarter of the British Isles. There are two main areas of deep convection likely:

(1) As the upper trough advances eastwards, accompanied by cooling mid-levels, strong surface heating will yield 300-400 Jkg-1 MLCAPE across the Republic of Ireland and Northern Ireland. Scattered showers and a few thunderstorms will develop in an environment with 30kts DLS, with some organisation possible. As a result, hail up to 1.5cm in diameter is possible, along with gusty winds.

(2) A surface cold front marks the boundary of this very moist, warm airmass (typically east of a line from The Wash to the Isle of Wight), but with a large amount of uncertainty as to how extensive this air will be across the SE. This seems to be tied to the development of a small surface low during Thursday morning, with a more developmental low (as per 18z E4 and multiple GFS runs) likely to lead to better backing of the flow and advection of this high WBPT airmass across parts of the British Isles, typically yielding afternoon dewpoints of 19-20C - quite exceptional for UK standards. A less developmental low will restrict this advection (as per 00z E4), with dewpoints reduced to nearer 16-17C typically. This will play one of the crucial factors on whether deep convection develops on Thursday afternoon/evening.

One other crucial factor is cloud cover limiting insolation. Either way, it seems likely that elevated convection will be ongoing at the beginning of this forecast period on Thursday morning across eastern parts of East Anglia / SE England (questionable as to whether there will be any lightning activity left with this, though), this gradually clearing eastwards but leaving a legacy of cloud at all levels. It seems reasonable that sufficient breaks should develop to allow strong surface heating with 700-1,000 Jkg-1 MLCAPE, and given rather slack conditions with proximity to small surface low, sea breeze component (and other areas of low-level convergence along / near cold front boundary) will likely provide the focus for isolated to well-scattered thunderstorm development during the late afternoon and through the evening hours (note: potential for late initiation). Within a strongly-sheared environment, initial storm mode may be supercellular, especially where local backing of the low-level winds is a little more pronounced. However, low-level flow is not particularly strong, and given unidirectional winds aloft, it is likely that such storms will tend to line-out with time.

Moistening of the boundary layer through the evening hours, and local backing of the surface winds, may promote the risk of a tornado, but the main hazards will be hail up to 2.5cm in diameter, damaging winds and local flash flooding (given PWAT 35-40mm). This would certainly satisfy our SVR criteria and it is possible an upgrade to highlight this risk may be required nearer the time. Uncertainty over how widespread this activity will be (if any at all) precludes the issuance of a MDT for now. The overall situation then becomes messy through the mid-late evening hours, with elevated convection likely to be imported from northern France / English Channel to mainly affect the extreme east of the SLGT area.

http://www.convectiveweather.co.uk/forecast.php?date=2016-06-23

Edited by Summer Sun

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loudest clap of thunder i've ever heard in my 46 years, last night at about 01.30. you could hear it splitting the air and the rain was awe-inspiring! anyway i expect Kent to be destroyed by a supercell today...

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It's *really* humid here in Watford, having problems with condensate on our air conditioning systems/building up on refrigeration in the kitchen like never before. Very warm as well even though no sun so far today, clouds are low but look to be breaking in places a little so fingers crossed for something later on

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Indeed, storm wise I would give last night's display 6/10. I think after a 'proper heatwave' the ingredients end up in place for some to see 10/10 storms in terms of what a storm can produce.

If you are a fan of rain normal reserved for the tropics then last night ticked all the boxes! 10/10. Never have I witnessed such PROLONGED torrential rain here.

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Just noticed the SE corner of England is on a level 1 estofex - last time they warranted this we had an absolute belter (July last year)

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3 minutes ago, Homerr said:

Just noticed the SE corner of England is on a level 1 estofex - last time they warranted this we had an absolute belter (July last year)

Wasnt SE England under lv1 yesterday? 

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3 minutes ago, James_southampton said:

Wasnt SE England under lv1 yesterday? 

Yeah just looked and it was - and it delivered! I'm trying not to get my hopes up but my inner Pyro is getting a little excited :yahoo:

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3 minutes ago, Stormyking said:

Here you go guys, my friend has aloud me to kindly share this with you, a beautiful CG, over mist bank from last night, there was alot of fog and msit banks last night, luckily soemtimes it clear to allow the lgihtning to be visible over it

Loght 5.jpg

We did great here. Was sat down by Ryde marina as the first storm rolled in. Certainly was beautiful.

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I have a feeling the murk and clag will scupper a lot of today's potential, however if the cloud does break and we get some good heating then my area of interest re. severe weather would be. I of course could be very wrong!

Weather 4.png

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Looking at the satellite the cloud won't be disappearing anytime within the next several hours here.

meh.

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Just now, East_England_Stormchaser91 said:

Lightening up a bit here now. Luton airport up to 21c. Is the sun out further down south? 

no signs of it getting brighter here, very murky with drizzle, not a chance of anything thundery here, never seen a forecast be so wrong, on the plus side i di me my first funnel cloud forming right in front of us while i was in france last week

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Just remember we didn't have much sun last week and we still had some decent lightning and thunder

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Some incredible mammatus on the edge of the initial group of storms that hit the south East last night! 

 

DSC_0081.JPG

Edited by <<Ryan>>

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Seriously thick air outside! We had a good light show about 11 and then some cracking gunshot thunder about 2ish? I couldn't get out of bed to look because my little one was asleep with us, but my god the rain! All routes into London were blocked via Liverpool Street and the roads were horrendous. I came back to work from home and I'm glad I did because I discovered that our roof has developed quite a severe leak into the kitchen. Quite drizzly here now, I've got the heating on to try and dry the floor out (!). Might actually try and set up the camera properly for tonight, I didn't want to hex things last night! 

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There's already a lot of cloud over the area where there's potential for storms, and if you check the radar there's a cluster of weak storms and general rain moving NE from France, currently over the Channel Islands with a huge cloud shield ahead and around it. 

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Really good dewpoint obs across the SE - a few 20C readings, but mostly 18-19C. Ripe for storm development with good sfc heating. Environment down there is primed for severe storms. Here's hoping. 

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19 minutes ago, East_England_Stormchaser91 said:

Lightening up a bit here now. Luton airport up to 21c. Is the sun out further down south? 

No ! Its very grey here, getting darker, very humid and a little drizzle.

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Very sleepy as was up till 2am with the storms.

 

Outside very still, lots of cloud and very warm.

Edited by West Sussex Kate

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