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Convective/Storm Discussion Thread - 8th July onwards


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Holy crap not bad eh ? Am well chuffed with this

That was amazing. The closest to lightning i've ever been....this was Warlingham area (Just oustide Croydon)...    

What a night it was, one of the best storms I have ever seen, maybe even better than July 3rd 2015! I some many great pictures on here today, so I thought I would share some of mine.  

Posted Images

18z looking interesting, it seems to be edging more towards the West for Tuesday night into early Wednesday, not a lot of Cape though. Whether it's just underplaying it a bit or not

 

STORM TUESDAY 12.png

STORM TUESDAY 18.png

Edited by TJS1998Tom
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3 minutes ago, TJS1998Tom said:

18z looking interesting, it seems to be edging more towards the West for Tuesday night into early Wednesday, not a lot of Cape though. Whether it's just underplaying it a bit or not

 

STORM TUESDAY 12.png

STORM TUESDAY 18.png

I think those charts are showing surface-based CAPE (SBCAPE), which would be derived from lifting air parcels from the surface and then calculating the resultant CAPE available. The storms on Tuesday night will be elevated above the surface (and hence not necessarily affected by surface parameters), so MLCAPE (mixed or mean layer) will be a more useful guide as to how much CAPE may be available.

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4 minutes ago, staplehurst said:

I think those charts are showing surface-based CAPE (SBCAPE), which would be derived from lifting air parcels from the surface and then calculating the resultant CAPE available. The storms on Tuesday night will be elevated above the surface (and hence not necessarily affected by surface parameters), so MLCAPE (mixed or mean layer) will be a more useful guide as to how much CAPE may be available.

Ah yeah, I remember someone saying that before. Still a chance for us in the East though seeing as the models are edging the precipitation Eastwards slightly, this website shows some Cape for around 3am on that night more Northwards

CAPE WED.png

Edited by TJS1998Tom
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1 hour ago, Summer Sun said:

Day 4 Convective Outlook

VALID 06:00 UTC Wed 19 Jul 2017 - 05:59 UTC Thu 20 Jul 2017

ISSUED 20:47 UTC Sun 16 Jul 2017

ISSUED BY: Dan

... MORNING ELEVATED THUNDERSTORMS ...

Scattered elevated thunderstorms may be ongoing at the beginning of this forecast period, mainly over the north Midlands / north Wales and perhaps also extending across the Irish Sea to Northern Ireland. Through Wednesday morning these should continue to move northwards into southern Scotland by midday, but probably with a decaying trend since the main axis of instability by these latitudes will have shifted east to the North Sea. Nonetheless, some lightning will still be possible across Scotland, but probably not as active as areas farther south earlier in the morning.

... AFTERNOON / EARLY EVENING SURFACE-BASED THUNDERSTORM POTENTIAL ...

Attention then turns to the warm sector where warm, moist low level airmass will reside and subject to strong heating should sufficient breaks develop in any cloud cover. Surface troughing and low-level wind convergence beneath the upper trough, combined with diurnal heating, may allow isolated surface-based thunderstorms to develop, which would be capable of large hail and localised flash flooding - the focus for these being primarily in a zone from the West Country - Midlands - E England. In general, would prefer better shear but an upgrade to SVR may be possible here - though very much dependent on if any surface-based convection can develop on Wednesday afternoon / early evening. Eastern portions of the Republic of Ireland could also see on or two heavy showers / thunderstorms on Wednesday afternoon / early evening.

... KENT CLIPPER LATE EVENING ...

There is also scope for thunderstorms over northern France to graze the extreme SE corner late evening on Wednesday night (nearer 22-00z).

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-19

'Decaying trend', just typical for me! I know it's still a few days away but seriously...

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This is why I like these types of set-ups. They survive their trip across the channel, and can hopefully become rooted to the boundary level. Inklings of May 27th .. we shall see!

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5 minutes ago, Mapantz said:

This is why I like these types of set-ups. They survive their trip across the channel, and can hopefully become rooted to the boundary level. Inklings of May 27th .. we shall see!

Recent models have been edging more east wards which gives me a chance this time lol

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The MetO map showing the weakening warm front and the 564 dam line creeping back in, around lunchtime on Tuesday. And a trough to kick-start some surface based storms on Wednesday, depending on sky conditions..

Screenshot_2017-07-16-23-55-06.thumb.png.6ff507e5ce6225afa6d28cdffd40d0c2.png Screenshot_2017-07-16-23-55-17.thumb.png.86c6b5392ef5e87f35078ec475c40fa1.png

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35 minutes ago, Flash bang flash bang etc said:

And all that talk of an eastward shift

As already mentioned by net weather, they are currently looking for a fix for this model with regards to convective rainfall. I'm not sure if it's already been done? It's not the only model to favour the SW Tuesday night for storms 

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Lol, Euro4 weakens stuff and curves the most intense storms into the near continent.. a bit like that time in June. 

17071821_1700.gif

It usually finds a way. Hopefully not this time..

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34 minutes ago, Evening thunder said:

Lol, Euro4 weakens stuff and curves the most intense storms into the near continent.. a bit like that time in June. 

17071821_1700.gif

It usually finds a way. Hopefully not this time..

Two fine days and a K*nt clipper...

Devon may be a good area for tmrw

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That Euro4 model is for 18-21z Tuesday. Much of the storm activity is modelled for later in the night.

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On 13/07/2017 at 22:15, SenlacJack said:

I must admit as I get older I find extremes of heat and cold more difficult to cope with but in reality how many days of 'unusually hot weather' do we get a year here in the UK ? Even down here in the south east I would think it rarely exceeds 10-20 days a year. Surely we can cope with that ?

Think of poor old Moki and his like up north......

 

 

I think on average every year we get about three or four heatwaves in the southeast with temps exceeding 32c on some days. These heatwaves can last for weeks at a time so although I don't have any exact figures to hand I do think the number of unbearably hot days in the south east exceeds 10 or 20 days. Forgive me for being a miserable old man about such things, I just find it very difficult to cope with extreme heat. :sorry:

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31 minutes ago, Sprites said:

Two fine days and a K*nt clipper...

Devon may be a good area for tmrw

Haha that's the more appropriate phrase. 

I'm hoping so, especially as my area went between the late May storms and apart from that there's only been a few very distant rumbles this year.. Would be good if it was widespread and shared out with many though.

28 minutes ago, Harry said:

That Euro4 model is for 18-21z Tuesday. Much of the storm activity is modelled for later in the night.

Not for me, the time of interest here has been generally shown to be around late afternoon and evening.

if it does actually look like this up to midnight (it shows storms in the western channel around mid-day and afternoon but weakens them), then it's probably over for me.
17071900_1700.gif
Suppose those little showers in the south could be the start of storms initiating to hit further north though

Edited by Evening thunder
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11 minutes ago, Nick F said:

Agree Brick, storms will be rooted above the boundary layer tomorrow night, can clearly see the warm nose at 900mb on the forecast skew-ts across S England. GFS painting some strong MLCAPE shifting north out of France Tuesday, probably due to the warm moist conveyor/theta-e plume spreading north overrun by an EML originating from SW Europe - creating steep mid-level lapse rates.

So Tuesday we see the theta-e plume spread N out of France ahead of increasingly negatively tilted upper trough moving in from the west coming up against high pressure retreating east.

gfsgif_thetae.thumb.gif.578ab39c56c4ecae4c16ab00e89a7cd0.gif

MLCAPE increasing out of France Tuesday night, as lapse rates steepen with EML spreading N/NE over plume in low-to-mid levels

gfsgif_cape.thumb.gif.68172c330d771fb8e05258649f970d74.gif

Deep-layer shear increasing too, as mid-upper winds strengthen and veer S to SWly with height with approach of upper trough while backed SEly at the surface - so this will organise elevated convection into some storm clusters that may merge into one or two MCS with a threat of hail, torrential rain and frequent cloud-to-ground lightning.

gfsgif_DLS.thumb.gif.48f8ea258ad0ef2e59d13cbaeba90265.gif

Large scale ascent indicated by vertical velocity charts:, charts for winds aloft do show a shortwave moving NE, which is likely causing the ascent

gfsgif_42-54.thumb.gif.9935d62fa8ba04b8d80b418a9e7624fa.gif

Believe it or not, elevated strong storms, which are fuelled by large amounts of CAPE aloft, can be prolific lightning producers, particularly away from heavy rain cores - this is because electrical charges tend to dissipate through rainfall without a lightning strike (water being a good conductor) - whereas drier air the electrical charge building between the elevated base and ground has to overcome it with a lightning strike.

Wouldn't take the precip charts too literally, but we may see elvated showers/storms develop initially over SW England tomorrow evening, before developing further east along N France/ E Channel and moving N across central-S and SE England Tuesday night, before spreading across Wales, Midlands, E Anglia during Wednesday morning, before reaching N England early afternoon and S Scotland later afternoon.

Meanwhile, further south, heat and humidity could spark some home-grown storms, mainly north of M4/London (due to SWly flow into southern most counties having a drier more stable element). Deep layer shear does look fairly weak and there looks like a lack of any particularly focus or forcing other than increasing larger-scale ascent from approach of upper trough from the west. Nevertheless, though, strong heating and fairly strong SWLy flow aloft and decent CAPE may compensate .. to allow some linear clusters of locally strong storms with hail and torrential rain leading to flash-flooding the main threats.

cape_w18z.thumb.png.c35f7396283784fc12619e9ca1fa2724.png

 

Fingers-crossed we see some good lightning shows Tuesday night, these storms drifiting N on Weds morning and then some good home-grown surface based storms on Wednesday afternoon.

 

wind_w15z.png

Has the main focus of lightning tues night shifted slightly more favouring areas west of I.O.W.?   btw have downloaded your thunderstorm guide from a few years ago..Was VERY informative and interesting  Thanks for that..

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2 minutes ago, Jules777 said:

Has the main focus of lightning tues night shifted slightly more favouring areas west of I.O.W.?   btw have downloaded your thunderstorm guide from a few years ago..Was VERY informative and interesting  Thanks for that..

What makes you think that? Don't think there's any particular focus, will have to wait and see, GFS CAPE charts would suggest more energy aloft east of I.O.W., but as ever with storms in the UK, other than N France probably getting a lot of activity, as the norm, it's up in the air for now where the focus will be Tuesday night :)

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