Convective/Storm Discussion Thread - 8th July onwards

[Frosty hollows]

1 minute ago, Aqbadger said:

So close yet so far here in Didcot. Bit of rain and distant rumbles

Five miles away and it's pepping up now after I thought it'd miss us

 

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Tue 18 Jul 2017 - 05:59 UTC Wed 19 Jul 2017

ISSUED 19:58 UTC Tue 18 Jul 2017

ISSUED BY: Dan

UPDATE 19:58 UTC MDT redrawn based on latest guidance, minor adjustments locally to SLGT. In general, clusters of primarily elevated thunderstorms will continue to develop through the remainder of the forecast period, and head generally N or NE, such that some areas could see some locally disruptive storms with very frequent lightning, while others stay storm-free. It is impossible to say exactly which locations will be impacted, but the MDT offers a reasonable guide as to those areas expected to have a higher chance if nothing else. Potential for portions of the Republic of Ireland to also be upgraded to MDT, but have refrained for now. Risk of hail and flash flooding continues overnight

Upper ridge over the British Isles on Tuesday will slowly drift east, as a negatively-tilted upper trough approaches from the Atlantic. On its forward side, poleward advection of a high WBPT airmass will occur from western Europe into southern then central Britain. Falling heights as upper trough approaches, combined with subtle shortwaves, will provide the focus for destabilisation of the mid-levels, with significant CAPE available from approx 850mb upwards by Tuesday evening/night.

Heavy showers / isolated thunderstorms could be possible as early as Tuesday morning close to Cornwall/Devon/Channel Islands from AcCas, though in general the risk of elevated thunderstorms here increases moreso during the afternoon hours, perhaps extending towards Dorset and Somerset by late afternoon. Bifurcating flow could also see an elevated thunderstorm complex pass close to Kent/Sussex during the first half of the evening, but more likely to stay a little to the south and hence no MDT issued for now.

Elsewhere, likely still dry at this stage, but through the evening hours increasing isentropic lift will allow numerous scattered elevated thunderstorms to develop on the leading edge of the Theta-E ridge, particularly focussed over SW England then extending east across Cen-S England, though the exact phasing of upper dynamics interacting with the plume is still uncertain - earlier destabilisation would then require the MDT to be extended farther south towards the south coast. A broken line of scattered elevated thunderstorms is then expected to drift north through the night into the Midlands, parts of Wales, and perhaps extending towards London and East Anglia - some question marks over how far east these may extend, and so have refrained from stretching the MDT too far east for now.

Some elevated thunderstorms could also form over the Republic of Ireland on Tuesday night, through a combination of advection of existing cells from SW England / SW Wales and new cells developing in-situ, generally moving towards the NW.

The magnitude of CAPE and steep mid-level lapse rates is such that lightning is likely to be very frequent with some thunderstorms, particularly those over England and Wales, and hail up to 1.5-2.0cm in diameter would be possible with the most potent cells. The risk of flash flooding is mitigated somewhat by notably dry surface layers, at least initially, but these will tend to moisten with time and bring a greater threat of some locally high rainfall totals should multiple storms move over the same area. Given the lead time, there is undoubtedly still some uncertainty over the exact forecast evolution, and further updates may be issued as new guidance becomes available.

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-18

[alexisj9]

Incidentally that light rain over dover seems to be anoprop

[tomp456]

The most interesting cloudscape of the day here

Edited July 18, 2017 by tomp456

[CaptainHappy]

2 minutes ago, Christchurch storm nut said:

What are your thoughts about what's brewing in the channel?  I have my camera gear at the ready if it comes this way.

 

If any of you fine people find yourself at mudeford Quay in a storm and see a very excited person taking photos next to a red Nissan note, it's probably me lol 

 

And if you're a fellow storm enthusiast, do say hello 

I must admit I am currently holding fire to see how the stuff to the south evolves. I would prefer to not be directly underneath it to be honest, as the rain appears to be pretty intense so you cant enjoy the experience without drowning.... With its current course, it will probably be a trip back to Barton on Sea to keep just east of it.

[Robbie Garrett]

Any Thunderstorms will be embedded,  the current cell is moving NNE at 25knots and has TOPS of FL390.

Quote

EGTT SIGMET 05 VALID 181830/182200 EGRR- EGTT LONDON FIR EMBD TS FCST WI N5000 W00015 - N5000 W00123 - N5029 W00418 - N5126 W00350 - N5048 W00009 - N5025 E00051 - N5000 W00015 TOP FL390 MOV NNE 25KT NC=

Quote

 

 

[MP-R]

Can see sunlit anvils to my south in the far distance.

[Chloe]

thunder & lightning west london yay!!!

[Frosty hollows]

That storm has suddenly got a a shift on. Moving much faster now. Heavy rain t and l. 

[Norfolk Sheep]

Oops, told my sister she was in line for some heavy rain nr Haslemere and she reported one or two spits and spots.....

[Allseasons-Si]

2 minutes ago, alexisj9 said:

Incidentally that light rain over dover seems to be anoprop

It doesn't look like anoprop to me,it's moving NE where as anoprop doesn't move,i hope this helps for future reference.

[dave reid]

What to do.

Back in Bournemouth now, thinking of heading toward Dorchester way

[Summer Sun]

 

[East_England_Stormchaser91]

36 minutes ago, 80sWeather said:

Hmmm is that cluster heading for E Mids/ E Anglia?

Looking like its on a collision course straight for the likes of Cambridgeshire/Northants and perhaps S Lincs/W Norfolk! Here's hoping it holds out. 

[Harry]

3 minutes ago, Summer Sun said:

Day 1 Convective Outlook

VALID 06:00 UTC Tue 18 Jul 2017 - 05:59 UTC Wed 19 Jul 2017

ISSUED 19:58 UTC Tue 18 Jul 2017

ISSUED BY: Dan

UPDATE 19:58 UTC MDT redrawn based on latest guidance, minor adjustments locally to SLGT. In general, clusters of primarily elevated thunderstorms will continue to develop through the remainder of the forecast period, and head generally N or NE, such that some areas could see some locally disruptive storms with very frequent lightning, while others stay storm-free. It is impossible to say exactly which locations will be impacted, but the MDT offers a reasonable guide as to those areas expected to have a higher chance if nothing else. Potential for portions of the Republic of Ireland to also be upgraded to MDT, but have refrained for now. Risk of hail and flash flooding continues overnight

Upper ridge over the British Isles on Tuesday will slowly drift east, as a negatively-tilted upper trough approaches from the Atlantic. On its forward side, poleward advection of a high WBPT airmass will occur from western Europe into southern then central Britain. Falling heights as upper trough approaches, combined with subtle shortwaves, will provide the focus for destabilisation of the mid-levels, with significant CAPE available from approx 850mb upwards by Tuesday evening/night.

Heavy showers / isolated thunderstorms could be possible as early as Tuesday morning close to Cornwall/Devon/Channel Islands from AcCas, though in general the risk of elevated thunderstorms here increases moreso during the afternoon hours, perhaps extending towards Dorset and Somerset by late afternoon. Bifurcating flow could also see an elevated thunderstorm complex pass close to Kent/Sussex during the first half of the evening, but more likely to stay a little to the south and hence no MDT issued for now.

Elsewhere, likely still dry at this stage, but through the evening hours increasing isentropic lift will allow numerous scattered elevated thunderstorms to develop on the leading edge of the Theta-E ridge, particularly focussed over SW England then extending east across Cen-S England, though the exact phasing of upper dynamics interacting with the plume is still uncertain - earlier destabilisation would then require the MDT to be extended farther south towards the south coast. A broken line of scattered elevated thunderstorms is then expected to drift north through the night into the Midlands, parts of Wales, and perhaps extending towards London and East Anglia - some question marks over how far east these may extend, and so have refrained from stretching the MDT too far east for now.

Some elevated thunderstorms could also form over the Republic of Ireland on Tuesday night, through a combination of advection of existing cells from SW England / SW Wales and new cells developing in-situ, generally moving towards the NW.

The magnitude of CAPE and steep mid-level lapse rates is such that lightning is likely to be very frequent with some thunderstorms, particularly those over England and Wales, and hail up to 1.5-2.0cm in diameter would be possible with the most potent cells. The risk of flash flooding is mitigated somewhat by notably dry surface layers, at least initially, but these will tend to moisten with time and bring a greater threat of some locally high rainfall totals should multiple storms move over the same area. Given the lead time, there is undoubtedly still some uncertainty over the exact forecast evolution, and further updates may be issued as new guidance becomes available.

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-18

Very kind of Dan to envelope me in the MDT zone but I'm yet to see so much as a flicker let alone a proper raindrop.

Let us hope that's more for later rather than this vista obscuring monstrosity 

[Homerr]

Picking up in NW London now 

[alexisj9]

1 minute ago, Allseasons-si said:

It doesn't look like anoprop to me,it's moving NE where as anoprop doesn't move,i hope this helps for future reference.

Nothing fell from the sky, so not anoprop your right, but evaporating on the way down.

[mike5900]

lightning detector just beeped. saying 17 miles away

[Hirudine]

Starting to get some interesting cloud formation here in Brum

[sendandreturn]

1 minute ago, dave reid said:

What to do.

Back in Bournemouth now, thinking of heading toward Dorchester way

lulworth?

[Hodgheg]

Not much going on here now. My view north west is blocked by crud. Probably will give it another hour before i come back now. 

[Paul Sherman]

God I wish that stuff was not to my south as would be on my way to the M11 now - Holding firm for now

[chrisbell-nottheweatherman]

Just has a line of altocumulus (not castellanus) heading north.

[Southern Storm]

2 minutes ago, CaptainHappy said:

I must admit I am currently holding fire to see how the stuff to the south evolves. I would prefer to not be directly underneath it to be honest, as the rain appears to be pretty intense so you cant enjoy the experience without drowning.... With its current course, it will probably be a trip back to Barton on Sea to keep just east of it.

I completely agree about the rain part, once it hits it's game over when it comes to taking photos, I'm about to head out, and hopefully get some nice footage, good luck

 

[Mokidugway]

A few sferics showing up off  the coast of Anglesey.