Jump to content

Storms and Convective discussion- 7th August onwards


Recommended Posts

16 minutes ago, Gordon Webb said:

Day 1 Convective Outlook

VALID 06:00 UTC Wed 12 Aug 2020 - 05:59 UTC Thu 13 Aug 2020

ISSUED 07:05 UTC Wed 12 Aug 2020

ISSUED BY: Dan

... SUMMARY ...

Elevated thunderstorms ongoing across NE Scotland and the Northern Isles during Wednesday morning

Aside from isolated elevated thunderstorms, scattered surface-based thunderstorms will develop in parts of England, Wales and Scotland from mid-afternoon, primarily near high ground and convergence boundaries

Thunderstorms will become increasingly numerous through the evening hours, merging into a complex from the Midlands into Wales

Large hail, damaging winds and flash flooding are all possible where storms occur

Other thunderstorms over France may push into S / SE England overnight, but confidence is low

There could be a relative minima in activity across some southern coastal counties, but have retained the SLGT for the overnight risk

... DISCUSSION ...

A marked shortwave will be driving a cluster of elevated thunderstorms across NE Scotland first thing on Wednesday morning, this will continue to lift northwards across Orkney and perhaps Shetland with time. Elsewhere, a few isolated elevated showers/weak thunderstorms may be possible across parts of England and Wales, especially the Midlands / SW England, driven by weak forcing aloft and rooted above a marked elevated mixed layer (EML). This EML will act as a cap, as strong surface heating through the day builds significant CAPE in the order of 1,000-2,500 J/kg - values rarely seen in the UK. In fact a climatology of UK CAPE 2002-2012 suggests the highest observed in this period was locally >3,000 J/kg during the heatwave of August 2003, once again noting how remarkable this current heatwave is.

 

Forecast soundings suggest temperatures in the low 30s Celsius will be necessary to break through the cap, and so true surface-based convection seems unlikely until early/mid afternoon at the earliest; however, a few elevated thunderstorms will be possible during the morning, which may subsequently become rooted within the boundary layer during the afternoon. Convergence zones and topography will be key for initial initiation of surface-based convection, and so high ground of SW Scotland, Cumbria, Pennines, North York Moors, Cambrian mountains and low-level convergence zones along the M4/M40 corridors for example will be the key areas. Once convection manages to break through the cap, explosive development is expected with cloud tops to 40,000ft (ELTs -55C). Shear is a little meagre, 10-15kts, and so likely to lead to downbursts and cold pools, which in turn will lead to daughter cells developing nearby. Damaging gusts of up to 50-60mph will be possible associated with downbursts, and the magnitude of CAPE and mid-level lapse rates suggests large hail 3-4cm, locally 5cm, in diameter is possible. 

 

During the evening, a shortwave will approach from France into southern England, and this may also aid in eroding the cap and allowing numerous thunderstorms to develop near convergence boundaries / topographic forcing / outflow boundaries. 700mb steering flow would suggest storm motion will be 10-15mph to the NW initially, turning increasingly to the WNW and 20-25mph as the evening progresses and the flow aloft backs and strengthens. Thunderstorms may grow upscale into a larger complex as they track westwards across Wales during the evening, and out across the southern Irish Sea / Celtic Sea while lightning activity will probably weaken as it moves into E / SE Ireland.

 

During the evening hours, a band or cluster of thunderstorms over northern France will begin to drift north across the English Channel, potentially affecting the Channel Islands for a time - it is unclear where these storms will survive the crossing, but the vast majority of model guidance is in agreement that they will decay fairly rapidly after leaving the coast, with lightning activity tending to hug the French coastline to the east. Nonetheless, a few elevated thunderstorms may be possible across S / SE England overnight, and perhaps at the end of the night close to the East Anglia coast.

 

edit - just outside moderate and direction of storms does not favor me either but for those Birmingham westwards again look like getting clobbered especially as motion turns more W during evening

Which site is this from, and is there a map coverage to accompany?

Link to post
Share on other sites
  • Replies 6.5k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

A beautiful altocumulus castellanus sunrise this morning. 

Oo she's a beauty 

My first attempt at storm shots 🤷‍♂️ (Please don't judge 🤣) The cells are impressive tonight! 

Posted Images

1 minute ago, simonbiggs said:

Which site is this from, and is there a map coverage to accompany?

sorry normally add that

socialmedialogo.png
CONVECTIVEWEATHER.CO.UK

Forecasting thunderstorms and severe convective weather across the British Isles and Ireland for up to the next 5 days.

 

  • Like 1
Link to post
Share on other sites
14 minutes ago, Azazel said:

Yikes - Midlands north again it is then. This must be one of the best convective seasons of all time up that way and into the North West!

well maybe Birmingham West as the steering winds change during the evening

Link to post
Share on other sites
16 minutes ago, Azazel said:

Yikes - Midlands north again it is then. This must be one of the best convective seasons of all time up that way and into the North West!

Convective Weather's forecast, posted above, is good for areas south of the Midlands.  I'm in the amber area and I'm definitely not in the Midlands.

I reckon a hill in the Cotswolds could be a good bet this afternoon, I might head to Minchenhampton Common if things go well later.

Edited by AWD
  • Like 2
Link to post
Share on other sites
2 minutes ago, AWD said:

Convective Weather's forecast, posted above, is good for areas south of the Midlands.  I'm in the amber area and I'm definitely not in the Midlands.

I reckon a hill in the Cotswolds could be a good bet this afternoon, I might head to Minchenhampton Common if things go well later.

Yeah this is my thinking too! Not sure where Minchenhampton is but I know that Cleeve Hill on the Cotwolds is the highest point and has a great view of Gloucestershire.

  • Like 1
Link to post
Share on other sites

met office has forecast  south and west Today: A few thunderstorms are possible during the morning, though conditions will be mostly hot and sunny once more. During the afternoon more widespread storms are likely to develop, especially towards Gloucestershire and Wiltshire. Maximum temperature 32 °C. Tonight: Thunderstorms rather widespread through the evening, then more focussed across north Devon into Somerset and Wiltshire overnight. Becoming drier with clear spells elsewhere, and turning mostly dry everywhere by dawn. i am going to wait and see 

Link to post
Share on other sites
2 minutes ago, Ben Sainsbury said:

Yeah this is my thinking too! Not sure where Minchenhampton is but I know that Cleeve Hill on the Cotwolds is the highest point and has a great view of Gloucestershire.

I choose this site over others because of the amazing ice cream parlour which passes time whilst waiting.  🍦🍨

  • Like 6
Link to post
Share on other sites

I always seem to be too far East when Midlands gets hit, or too far too far West when a Kent clipper bizarrely goes straight north. Only had a couple of distant rumbles so far this year. Fingers crossed I can blag one today or tomorrow

  • Like 2
Link to post
Share on other sites

Dam it,same areas again by looks of it.I seem to be on the edge every time something happens this year.what ever happend to the ones that stared down south or imports that took out a wide area,the older I get the worse for storms here it seems.it OK people saying oh look it midlands again.I'm in the midlands and it don't happen here,be more specific in where you say.

Link to post
Share on other sites

well i have to say the pics and vids of the storms that have battered parts of the country over the last cpl of days are incredible, and as a long time member of the no storms club, i have to say we are a little jelous.

  • Like 2
Link to post
Share on other sites

Some big towers to the south in Bridlington , camera doesn't do any justice think ill go out and about just incase. 

IMG_20200812_084811.jpg

Edited by Aiden2012
Link to post
Share on other sites

I know you'll all think I'm moaning however I don't like the situation to the south over in northern France. A big decaying storm is likely to send its cloud shield over into the south west as the morning progresses.

Link to post
Share on other sites

 

 

From the GFS 00z.

Window of opportunity exists for storms for Kent/East Sussex between 15z and 18z, conveniently during the time of most insolation. Not a great opportunity, but an opportunity nevertheless. Will there be enough time for storms to form? It's still only a moderately convective environment, no DLS, slack winds, and no convergence zone.

skewt1.thumb.png.8b42970578e44de36ccbac9de73504bf.png

Three hours later the opportunity is lost:

skewt2.thumb.png.8f0e5f96c0ffceb639b7b4523d0edfd0.png

Best hope, according to GFS, for far SE (Kent/East Sussex) is relying on our good friends, the French, to send something our way, later on this evening:

precip1.thumb.png.d7a756da487d6a932a40f72ff79444bc.pngprecip2.thumb.png.30de978bd214588d7bb89f74378a9a21.png

Good luck all !!

 

Edited by VillagePlank
  • Like 2
Link to post
Share on other sites

Another day   and more potential     im sure many will see a light show or thunder at some point this evening 

Link to post
Share on other sites
5 minutes ago, Alderc said:

I know you'll all think I'm moaning however I don't like the situation to the south over in northern France. A big decaying storm is likely to send its cloud shield over into the south west as the morning progresses.

I was worried about this last night.

  • Like 1
Link to post
Share on other sites
15 minutes ago, Ndc Ozzie said:

Dam it,same areas again by looks of it.I seem to be on the edge every time something happens this year.what ever happend to the ones that stared down south or imports that took out a wide area,the older I get the worse for storms here it seems.it OK people saying oh look it midlands again.I'm in the midlands and it don't happen here,be more specific in where you say.

yep seems about right , only got them yesterday because they tracked NE but today back to tracking NW then WNW

Edited by Gordon Webb
to add a r to tacking
Link to post
Share on other sites
16 minutes ago, Mitch perrott said:

I'm going to book a holiday to catacumbe River

 

You mean Catatumbo? It's always been high on my list, but bloody difficult to get to and in a very dangerous country.

Link to post
Share on other sites
Guest
This topic is now closed to further replies.
×
×
  • Create New...