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Convective/Storm Discussion Thread - 1st June onwards

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For the first time in the last 7 days of heat and crazy strong UV it feels oppressive thus afternoon. Thickening black clouds around, feels like a spark’s needed to set it all off, but not sure if it’ll happen. Bit borderline here in Glos looking at various predictions for later. 

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1 hour ago, TheFlyingDuck said:

Im in the red square, but no sign of any of the rain on the radar?

Does virga get picked up?

I believe it does given that radars scan all heights up to the cloud base as far as I know.

From reports I've seen in Devon & Cornwall, it appears that even down there, it's been wet but not as much so as you might think based on radar.

 

Given the dry thunderstorm risk, it's good to see such limited lightning reports so far today. 

Questions will still be asked this evening though, as the unstable section of the plume attempts to waft in across the far south following a day of considerable surface layer heating (currently in the 29s here despite seeing a fair bit of cloud in the past couple of hours; it's not just the ground but the lower levels of the air as a whole that are hot).

Basically, that surface heating may be sufficient to break the capping inversion (CI) in a few spots, and where this happens, there's enough energy for a pretty feisty storm - but not a particularly wet one given limited moisture availability. Those in the SW so far today have had less intense peak rain rates than is typically seen during summer t-storms. So that's why there's a 'dry thunderstorm' risk today, as much of the rain may evaporate in the warm lower level air, leaving any fires initiated by CG lighting with nothing much to put them down.

A possible saviour could be the ridge reasserting from the north; if this happens fast enough, the instability above the CI will be put to bed before much in the way of t-storms can get going. The most recent high-res model runs have generally favoured this outcome. ARPEGE was retaining some very shallow convection across CS England into tomorrow morning, but has dropped that in today's runs.

 

So the signs are that most of those in CS and SE England will be waiting until at least Wednesday for significant rainfall, and even then it's only a lottery in the form of scattered 'popcorn' convection; slow-moving storms that don't keep going for very long as their own downdrafts kill them off. From my perspective, I'm concerned that with a slack pattern in place, the sea breeze will tend to push the showers inland of me before they really get going. The latest ARPEGE runs have shown exactly that scenario. Southern coasts may find more than 1 or 2 mm of rain very hard to come by within the first 10 days (at least!) of July, once whatever develops today has cleared away.

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Had all my action in April, looks like a long summer ahead with no🌩️

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BBC suddenly saying home counties may now get storms tonight after saying nothing for a week. Could it be they just seen the monsters leaving the French coast.  They are well spread out.

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GFS tonight shows a more showery outlook so possibly something in the mix more widely later in the week.

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23 minutes ago, The PIT said:

GFS tonight shows a more showery outlook so possibly something in the mix more widely later in the week.

Yes also Net-Wx for Thur/Fri.

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47 minutes ago, biddie said:

BBC suddenly saying home counties may now get storms tonight after saying nothing for a week. Could it be they just seen the monsters leaving the French coast.  They are well spread out.

I saw on the metoffice map that they showed some storms breaking out about 10pm. 

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Possibility of a surprise for the SE overnight?

 

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21 minutes ago, Cableguy said:

Possibility of a surprise for the SE overnight?

 

Hopefully, desperate for the rain, what models are showing that

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Those thunderstorms in west and east France are moving slowly and the ones going up west France from bay of biscay are moving slowly

Edited by Tom dewey likes thunder

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I have big news... something like drops of water are actually coming out of the sky

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All this heat last week  and for the next two weeks , but very limited and isolated thunder risk it seems , still no thunder here since may 2017, the longest thunderless period for probably many many decades, the clock is now ticking, anything after mid august is unlikely now

I would bet on this heat just whimpering away from the north west when it does finally end , rather than going with a bang, certainly for here

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Looks like tonight will remain very warm however I fear that debris from the decaying French stroms will only serve to ruin tomorrow!! Not much electrical activity likely imo.

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6 minutes ago, IanR said:

All this heat last week  and for the next two weeks , but very limited and isolated thunder risk it seems , still no thunder here since may 2017, the longest thunderless period for probably many many decades, the clock is now ticking, anything after mid august is unlikely now

I would bet on this heat just whimpering away from the north west when it does finally end , rather than going with a bang, certainly for here

Jesus Ian , you're a barrel of laughs tonight .

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35 minutes ago, Alderc said:

Looks like tonight will remain very warm however I fear that debris from the decaying French stroms will only serve to ruin tomorrow!! Not much electrical activity likely imo.

Nothing forecast for tomorrow anyway, not like it was a loaded gun to be ruined by a decaying MCS🤔

 

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24 minutes ago, Cableguy said:

Nothing forecast for tomorrow anyway, not like it was a loaded gun to be ruined by a decaying MCS🤔

 

I meant ruin the day in general down here, sorry should have been clearer, that said we got to 29.2c no almost no sun after 10am today.....

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https://www.viewsurf.com/univers/ville/vue/13398-france-aquitaine-bordeaux-les-quais

beautiful storm in Bordeaux right now, probably too far south to reach here but even so...

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It's two weeks away but this would be great after getting all this heat from the latest GFS run

image.thumb.png.b6e47cc71decacc304ba9b82b1aa9261.png

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Day 1 Convective Outlook

VALID 06:00 UTC Mon 02 Jul 2018 - 05:59 UTC Tue 03 Jul 2018

ISSUED 04:16 UTC Mon 02 Jul 2018

ISSUED BY: Dan

Residual high ThetaW plume lingers across southern England on Monday morning, but will slowly retreating to the SW as the Azores high extends across northern Britain, backing the flow over southern Britain. Subtle forcing aloft destabilising this plume continues to provide the focus for sporadic elevated showers over southern counties of England during the morning, some perhaps capable of producing a few lightning strikes.

These showers will become increasingly confined to Devon/Cornwall as the morning progresses, and while most NWP guidance remains rather unenthusiastic there is scope for an uptick in lightning potential as a minor shortwave passes close to Cornwall late morning into the afternoon, perhaps allowing deeper convection to develop. Confidence is not particularly high, so the SLGT should be treated as a low-end (i.e. near 30%). Shear is weak, so any thunderstorms that do occur will be rather pulse-type in nature and probably largely elevated. Main threat, therefore, will be local rain accumulations causing some surface water issues. Any showers/storms that do occur will gradually fade during the evening hours, though further elevated showers are possible on Monday night over the English Channel, perhaps getting close to the south coast at times.

http://www.convectiveweather.co.uk/forecast.php?date=2018-07-02

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10 hours ago, Scott Page said:

https://www.viewsurf.com/univers/ville/vue/13398-france-aquitaine-bordeaux-les-quais

beautiful storm in Bordeaux right now, probably too far south to reach here but even so...

Second night of intense storms here in the Charente (storm mentioned above). By far the most electrically active storm I have ever witnessed with constant lightning (and I mean constant). Pretty gusty wind and virtually no rain reached the ground. Rinse and repeat tonight. Heat is very oppressive.

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Day 2 Convective Outlook

VALID 06:00 UTC Tue 03 Jul 2018 - 05:59 UTC Wed 04 Jul 2018

ISSUED 19:16 UTC Mon 02 Jul 2018

ISSUED BY: Dan

Upper low west of Biscay will elongate and extend northwards towards Celtic Sea during Tuesday. Portions of the high ThetaW airmass over France will be drawn northwards across the English Channel into southern England / south Wales, and overnight into southern Republic of Ireland. Subtle forcing will allow some elevated convection to develop, although rather marginal instability suggests lightning would only be isolated at best, and given dry air in the low-levels much of any rain will evaporate before reaching the ground. Slightly deeper instability and moisture exists over SW England and so Devon/Cornwall would generally have a slightly higher chance for some sporadic lightning should any showers develop - but confidence is not high enough to warrant a SLGT.

http://www.convectiveweather.co.uk/forecast.php?date=2018-07-03

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