Convective / Storm Discussion Thread - 31st May 2017 onwards

[Martin Auld]

I honestly can't believe we have the highest level in Europe on estofex tomorrow. Never thought I would ever see the day

[SarahWxm]

I'm so excited!! I live in Wrexham but currently on holiday in East Yorkshire. Later today is looking absolutely amazing!!

[Aiden2012]

2 minutes ago, SarahWxm said:

I'm so excited!! I live in Wrexham but currently on holiday in East Yorkshire. Later today is looking absolutely amazing!!

Yep I'm in Bridlington trying to not get too excited cause knowing my luck it won't happen lol 

[Another Kent clipper]

I'm driving a van between 5 and 9 pm tonight for work. I've a feeling I'm gonna see some stuff but nothing to capture it on

[Pursuer of Storms]

Given the lack of luck so far this year, I'm not going to get my hopes up for today. Still not a single rumble of thunder here this year!

[Delka]

16 minutes ago, Norfolk Sheep said:

A rather brisk easterly already - soon to be a howling gale no doubt. Makes sitting outside a non starter  Semi hopeful for later/tonight, but not totally convinced.

near completely windless here!

[SarahWxm]

6 minutes ago, Aiden2012 said:

Yep I'm in Bridlington trying to not get too excited cause knowing my luck it won't happen lol 

Haha yeah I normally jinx things so hoping this is not going to be the case. It'd be my luck wrexham got more action seeing as I'm not there atm. I'm in Sheffield today but coming back late afternoon, staying in Raywell near Hull. 

[chionomaniac]

Great to see a level 2 over the country today, we have an AC field over East Grinstead already this morning - trending Castellanus, so I see that as a positive sign for those further north already - and I wouldn't rule out a surprise further south too. It all depends on the timing of the upper trough eastwards.

[Summer Sun]

Further torrential rain in the north-west currently

[chionomaniac]

Quite a lot of activity already over north Pennine region, more than expected this early

[VillagePlank]

Today's hotspot, is Birmingham, and, pretty much all of the N Midlands.

A moderately convective environment (KI = 27) may lead to widely scattered severe storms (TT = 53) A (very) large amount of energy becomes available (CAPE = 2,402 J/kg, Dp = 20.9) after being inhibited for most of the day (CIN =  c.200 J/kg) in an extremely unstable profile (LI = -9) carries the risk of frequent lightning, and large hail. Any cells that form will also contain large amounts of precipitation.

Happy hunting!

 

[Supacell]

It would be typical for Derbyshire to get a big storm today as I am not there to see it. To make matters worse the latest storm risk forecasts for where I am in Germany have removed any risk of storms for tomorrow, unless I am able to travel 300-400 miles east over Thursday night, which will not be possible as I have an early flight on Friday. I can just see it is all falling into place for me to take an emotional kicking over the next two days.

So, for those living in the Midlands I will take payment by PayPal, bank transfer or cash once you get flattened by a supercell as a thank you for vacating the area and taking my shield with me

In all seriousness though, it does look good for this afternoon/evening for the Midlands northwards with somewhere like Lincolnshire and along NE England with the best risk later. However, be careful of reading too much into the GFS CAPE charts. They are overdoing dew points and so showing up insane CAPE charts which are not realistic. I would say 1000-1500 j/kg of CAPE is more realistic which is still plenty to produce severe storms if the cap can break (much more likely than on previous days IMO).

 

[Ben Sainsbury]

And just to note those in the region where severe storms are possible, make sure to get plenty of photos! 

[Azazel]

My bets are on Lincoln for later, looks prime to me.

 

Also feel North Wales/Liverpool/Manchester could see something spectacular.

[Derecho]

I don't think I will get anything down here in Southampton still but my family are in Hull so I will be watching with keen interest!

Enjoy your storms, it looks as though further north at least, the cap will be broken.

Can't believe Hull is under the level 2 ESTOFEX warning!

[Ben Sainsbury]

Just now, Azazel said:

My bets are on Lincoln for later, looks prime to me.

 

Also feel North Wales/Liverpool/Manchester could see something spectacular.

I know we have more general thunderstorms now, but as CAPE builds I think the strongest thunderstorms will be in the areas which you have just mentioned.

[Nick L]

Very much a low risk-high impact sort of day south of Manchester. The vast majority in the Midlands and the South will see nothing today.

[Azazel]

Very similar to last year in a way. We seem to get short-lived periods of absolutely sweltering heat down in the south only to see it meekly fizzle out to nothing.

 

I think my one storm last year came on literally the last day of summer.

[sparky1972]

guess i will pack the camera away and leave garden furniture/parasols out then,  bugger, lol

[Stuart]

 

Day 1 Convective Outlook

VALID 06:00 UTC Wed 21 Jun 2017 - 05:59 UTC Thu 22 Jun 2017

ISSUED 08:06 UTC Wed 21 Jun 2017

ISSUED BY: Dan

UPDATE 08:06 UTC Minor adjustments made based on analysis of latest guidance - potential for severe surface-based thunderstorm initiation very late afternoon into the evening hours, initially over NW Midlands / NW England, the focus then shifting E/NE across N England through the evening, perhaps lasting well into late evening before moving offshore to the North Sea. Very large, damaging hail, strong winds, very frequent lightning and perhaps a tornado will be possible with these. Potential also exists farther south through Cambridgeshire/Norfolk etc, but questions over whether cap here can be eroded. Latest guidance continues to suggest increase in coverage of elevated deep convection over SW England and W Country towards the end of Wednesday night / Thursday morning.

 

UPDATE 06:08 UTC MDT over Cumbria shifted east (and hence merged with other existing MDT) given slightly faster eastward motion of thunderstorm cluster, now over NE England

 

Broad upper ridging (and anticyclonic flow) will still be in place across much of the British Isles on Wednesday, but as an Atlantic upper trough approaches it will advect an EML (elevated mixed layer) above a very warm and reasonably moist surface layer (afternoon dewpoints near 19-21C, ignoring the GFS which continues to over-estimate surface dewpoints, and hence grossly exaggerates modelled CAPE). 

 

----------------------------------------------------

 

Elevated thunderstorms will possibly be ongoing / developing at the beginning of this forecast period, especially over northern England and southern Scotland, with general areas of showery precipitation with embedded lightning moving erratically NE-wards across the remainder of Scotland.

 

----------------------------------------------------

 

Farther south, assuming plenty of insolation then strong heating will yield 2,000 - 3,000 Jkg-1 SBCAPE in a notably capped environment - the greatest instability developing during the second half of the afternoon and into the evening hours. Many areas will remain dry under such conditions, but it is just possible that enough forcing from a combination of sea breeze, topography, surface troughing and falling heights aloft during the evening hours may be able to overcome / erode the cap to allow explosive but probably fairly isolated thunderstorm development to occur. High-res models continue to offer little support for surface-based thunderstorms given the strength of the capping and dry layers in the mid-levels, but that said elements of medium-level instability release over northern England could become rooted in the boundary layer, and / or surface-based convection could develop.

 

Given the lack of any useful guidance (aside from 12z ECMWF, GFS has been consistently too moist in surface layers on recent days and continues to overplay the thunderstorm risk) it becomes hard to highlight any specific areas at risk with any confidence - but overlapping of favourable ingredients would suggest one or two isolated but severe thunderstorms would be possible during the late afternoon, more especially evening, hours across N or E England. Such storms could rapidly organise into multicells or perhaps supercells, capable of producing damaging hail up to 4-5cm in diameter, strong gusts of wind and, if surface winds can remain ideally backed, perhaps also a tornado. A severe thunderstorm cannot be ruled out elsewhere in England, but in general capping is likely to be too strong to be overcome.

It is quite possible that very little, if any, notable surface-based convection occurs - but worth stressing should it occur, then it could be quite noteworthy and potentially disruptive. A MDT has been issued for now where this is most likely to occur - but this may need updating with any further guidance.

----------------------------------------------------

 

Overnight, rapid height falls as an upper trough approaches combined with a cold front will allow medium-level instability release to help generate some elevated deep convection with the potential for a few thunderstorms - the risk beginning over SW Britain initially, then running NE-wards with time through the early hours. The exact track, extent and timing is very uncertain at the moment depending on the phasing of the upper trough with residual high WBPT plumes across S Britain, and further updates / tweaks may be necessary to the forecast.

 

http://www.convectiveweather.co.uk/forecast.php?date=2017-06-21

 

[Summer Sun]

 

Day 1 Convective Outlook

VALID 06:00 UTC Wed 21 Jun 2017 - 05:59 UTC Thu 22 Jun 2017

ISSUED 08:06 UTC Wed 21 Jun 2017

ISSUED BY: Dan

UPDATE 08:06 UTC Minor adjustments made based on analysis of latest guidance - potential for severe surface-based thunderstorm initiation very late afternoon into the evening hours, initially over NW Midlands / NW England, the focus then shifting E/NE across N England through the evening, perhaps lasting well into late evening before moving offshore to the North Sea. Very large, damaging hail, strong winds, very frequent lightning and perhaps a tornado will be possible with these. Potential also exists farther south through Cambridgeshire/Norfolk etc, but questions over whether cap here can be eroded. Latest guidance continues to suggest increase in coverage of elevated deep convection over SW England and W Country towards the end of Wednesday night / Thursday morning.

 

UPDATE 06:08 UTC MDT over Cumbria shifted east (and hence merged with other existing MDT) given slightly faster eastward motion of thunderstorm cluster, now over NE England

Broad upper ridging (and anticyclonic flow) will still be in place across much of the British Isles on Wednesday, but as an Atlantic upper trough approaches it will advect an EML (elevated mixed layer) above a very warm and reasonably moist surface layer (afternoon dewpoints near 19-21C, ignoring the GFS which continues to over-estimate surface dewpoints, and hence grossly exaggerates modelled CAPE). 

----------------------------------------------------

Elevated thunderstorms will possibly be ongoing / developing at the beginning of this forecast period, especially over northern England and southern Scotland, with general areas of showery precipitation with embedded lightning moving erratically NE-wards across the remainder of Scotland.

----------------------------------------------------

Farther south, assuming plenty of insolation then strong heating will yield 2,000 - 3,000 Jkg-1 SBCAPE in a notably capped environment - the greatest instability developing during the second half of the afternoon and into the evening hours. Many areas will remain dry under such conditions, but it is just possible that enough forcing from a combination of sea breeze, topography, surface troughing and falling heights aloft during the evening hours may be able to overcome / erode the cap to allow explosive but probably fairly isolated thunderstorm development to occur. High-res models continue to offer little support for surface-based thunderstorms given the strength of the capping and dry layers in the mid-levels, but that said elements of medium-level instability release over northern England could become rooted in the boundary layer, and / or surface-based convection could develop.

Given the lack of any useful guidance (aside from 12z ECMWF, GFS has been consistently too moist in surface layers on recent days and continues to overplay the thunderstorm risk) it becomes hard to highlight any specific areas at risk with any confidence - but overlapping of favourable ingredients would suggest one or two isolated but severe thunderstorms would be possible during the late afternoon, more especially evening, hours across N or E England. Such storms could rapidly organise into multicells or perhaps supercells, capable of producing damaging hail up to 4-5cm in diameter, strong gusts of wind and, if surface winds can remain ideally backed, perhaps also a tornado. A severe thunderstorm cannot be ruled out elsewhere in England, but in general capping is likely to be too strong to be overcome.

It is quite possible that very little, if any, notable surface-based convection occurs - but worth stressing should it occur, then it could be quite noteworthy and potentially disruptive. A MDT has been issued for now where this is most likely to occur - but this may need updating with any further guidance.

----------------------------------------------------

Overnight, rapid height falls as an upper trough approaches combined with a cold front will allow medium-level instability release to help generate some elevated deep convection with the potential for a few thunderstorms - the risk beginning over SW Britain initially, then running NE-wards with time through the early hours. The exact track, extent and timing is very uncertain at the moment depending on the phasing of the upper trough with residual high WBPT plumes across S Britain, and further updates / tweaks may be necessary to the forecast.

http://www.convectiveweather.co.uk/forecast.php?date=2017-06-21

[P-M]

http://www.convectiveweather.co.uk/forecast.php?date=2017-06-21

 

From convective weather who I also find decent at forecasting (as well as you lot on here) - risk shifted further east in line with Nick's forecast.

 

Day 1 Convective Outlook

VALID 06:00 UTC Wed 21 Jun 2017 - 05:59 UTC Thu 22 Jun 2017

ISSUED 08:06 UTC Wed 21 Jun 2017

ISSUED BY: Dan

UPDATE 08:06 UTC Minor adjustments made based on analysis of latest guidance - potential for severe surface-based thunderstorm initiation very late afternoon into the evening hours, initially over NW Midlands / NW England, the focus then shifting E/NE across N England through the evening, perhaps lasting well into late evening before moving offshore to the North Sea. Very large, damaging hail, strong winds, very frequent lightning and perhaps a tornado will be possible with these. Potential also exists farther south through Cambridgeshire/Norfolk etc, but questions over whether cap here can be eroded. Latest guidance continues to suggest increase in coverage of elevated deep convection over SW England and W Country towards the end of Wednesday night / Thursday morning.

 

UPDATE 06:08 UTC MDT over Cumbria shifted east (and hence merged with other existing MDT) given slightly faster eastward motion of thunderstorm cluster, now over NE England

 

Broad upper ridging (and anticyclonic flow) will still be in place across much of the British Isles on Wednesday, but as an Atlantic upper trough approaches it will advect an EML (elevated mixed layer) above a very warm and reasonably moist surface layer (afternoon dewpoints near 19-21C, ignoring the GFS which continues to over-estimate surface dewpoints, and hence grossly exaggerates modelled CAPE). - See more at: http://www.convectiveweather.co.uk/forecast.php?date=2017-06-21#sthash.IVvbiXIF.dpuf

 

 

[sparky1972]

7 minutes ago, Nick L said:

Very much a low risk-high impact sort of day south of Manchester. The vast majority in the Midlands and the South will see nothing today.

guess i will pack camera away and leave garden furniture and parasols out then.  bugger, lol

[P-M]

It appears we all had the same idea!

[Supacell]

Haha, nice to see we all keeping a watch on weather updates from Convective Weather and the like