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Storms and Convective discussion- 15th August onwards

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A shiny new thread. As expected last week brought severe thunderstorms for a few of us. Not everywhere has been affected though and where some have been deluged, others have remained dry. A fantastic week for storm enthusiasts (I am still editing my videos from both Tuesday night and Wednesday evening), not so good for those caught in the flooding.

Old thread here 

It's busy in here at the minute, so please be mindful that if your post is not to do with convective weather it should not be in here. It will likely remain busy with further thunderstorms expected over the next four days and the risk spreading north once more. So please, carry on chatting and enjoying.

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What are the thoughts on today? Looking very similar to yesterday at the moment so I won’t be holding my breath for any storms.

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Posted (edited)

Looks like the best time for storms today in the South East will be 19:00.

Here is the CAPE and the Lifted Index for the South East

BAE0D0D6-3644-4BBF-AFDA-A571301EAE39.png

A5396AB6-20DD-4B84-B473-84D86764862B.png
 

And for the UK at the same time

F2721174-D941-4027-9734-6CD4AD880827.png

0506599C-3C89-4048-A9AF-EE080B5885ED.png

Edited by Stevie B
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I will start by saying lets ignore my comment from yesterday. This is not thePlace for such posts. Hope it made someone’s day loool.


Anyway moving back to real weather dynamica.

 

Well today is a bit different to yesterday. We have a cold front pushing from the south. But also a weak trough moving from the continent. This could cause some pulse storms or showers this morning i suppose moving E-W however from what i see we should start to see a more S/SE’ly flow overnight tonight and in Tomorrow  and Monday giving us another chance for the next few days before return to atlantic weather.
The front leaving france seems to be pushing cloud with it so hopefully we can see some of the cloud break and more sun this afternoon to help give some parts Another chance for some fireworks. Just my thoughts on today do correct me if im wrong looooool
 

 

4A613829-B194-410D-8250-208252B97F9F.png

C589B0A8-7FAB-4D37-AB9D-FEE71B3B869F.jpeg

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https://    www.netweather.tv/forum/topic/94168-storms-and-convective-discussion-15th-august-onwards//?do=getLastComment

...to go directly to latest posts in this new thread (remove the added space in the URL)

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Day 1 Convective Outlook

VALID 06:00 UTC Sat 15 Aug 2020 - 05:59 UTC Sun 16 Aug 2020

ISSUED 07:31 UTC Sat 15 Aug 2020

ISSUED BY: Dan

Upper low over Biscay will slowly approach from the southwest, serving to cool the upper levels on Saturday. Residual high Theta-W plume straddles much of central/southern Britain across to Ireland, and provides the focus for sporadic elevated convection as minor impulses drift westwards in the easterly flow aloft. PVA tends to increase during Saturday night, and so this may be when elevated showers/weak thunderstorms become more widespread, albeit the focus shifted somewhat further north compared with earlier in the day. Instability overall is weaker than previous days, and so lightning will probably be rather isolated.

At the surface, extensive low cloud and mist is expected once again, although forecast profiles reveal the low-level warm nose that was present on Friday will gradually erode, in theory allowing greater mixing to occur and prospects for some breaks in the cloud to allow surface heating. This will be crucial for developing deep convection, primarily focussed along low-level convergence zones - one likely close to the M4 corridor through London and then northeast into East Anglia, and another along the south coast. Temperatures into the low 20s will be required to trigger deep convection (in conjunction with convergence zones / topography), leading to very tall but very skinny CAPE profiles. 300-600 J/kg CAPE may build, primarily over East Anglia / SE Eng / Cen S Eng where cloud breaks are most likely (especially around London) and this could aid a few heavy showers or weak thunderstorms during the afternoon or early evening. Slow storm motion (5-10mph) and PWAT 35-40mm suggests the risk of local flash flooding where showers/storms do occur. A funnel cloud or weak tornado may be possible given low cloud bases and low-level vorticity that may be ingested into an updraft - especially SE England.

A low-end SLGT has been introduced where sufficient cloud breaks / surface heating is most likely, with concerns about cloud cover elsewhere. A SLGT has also been included for the Channel Islands where some sporadic lightning may be possible towards the end of Saturday night as thunderstorms approach from France, but uncertainty as to how active they will be by arrival.

http://convectiveweather.co.uk/forecast.php?date=2020-08-15

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Wind has backed round from an NE to E here now, so cloud cover has broken up earlier, and it's fairly sunny (at the moment), so it's fingers crossed for those that have been "stormless".

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What’s the mechanism by which the cloud will break? Will the sun burn it off or are we looking for the odd small gap here and there?

On satellite looks like we could be waiting ages for it to happen, more keeps appearing wherever it clears 😬

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23 minutes ago, Flash bang flash bang etc said:

What’s the mechanism by which the cloud will break? Will the sun burn it off or are we looking for the odd small gap here and there?

On satellite looks like we could be waiting ages for it to happen, more keeps appearing wherever it clears 😬

I'd hazard a guess and say that the clear skies are coming from France, pushing North & may be here by this afternoon.

I have a lack of hope for anything today due to this pesky cloud hanging about.

63929741_GMTStandardTime(1).thumb.gif.78a970030c27dcfa462e87a11acd571c.gif

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Ugh, day two, total clag again however this is it’s constantly drizzling.....little sign on the satellite of any breaks coming. Worst and most painful thundery breakdown ever.....

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12 minutes ago, Alderc said:

Ugh, day two, total clag again however this is it’s constantly drizzling.....little sign on the satellite of any breaks coming. Worst and most painful thundery breakdown ever.....

Definitely bad for some people, but for others it’s been a cracking breakdown for the midlands, Wales, Scotland etc. I would have been stormless too if I hadn’t taken action and driven straight through the Thursday afternoon Surrey storm 😂😂

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13 minutes ago, oliverek7 said:

Definitely bad for some people, but for others it’s been a cracking breakdown for the midlands, Wales, Scotland etc. I would have been stormless too if I hadn’t taken action and driven straight through the Thursday afternoon Surrey storm 😂😂

Was that the one over Epsom?

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Just looked at the models and its desperately bad news for here, the cloud doesn't really clear all weekend and thundery outbreaks again tomorrow look like forming further north while todays risk appears to have vanished from the Arome/Arpege....

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The only good thing this week was that I managed to work each day. Nearly took time off but as the forecasts were so uncertain I didn’t want to lose out on a day’s pay just to stare at thunderless rain or clear sky.

It would actually be quite depressing otherwise. What a waste of a week of potential that could have been historic.

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1 minute ago, Alderc said:

Just looked at the models and its desperately bad news for here, the cloud doesn't really clear all weekend and thundery outbreaks again tomorrow look like forming further north while todays risk appears to have vanished from the Arome/Arpege....

Friday onward never looked particularly good to me. Yet the Met Office warnings keep on coming!

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2 minutes ago, Lance M said:

Friday onward never looked particularly good to me. Yet the Met Office warnings keep on coming!

I know, its almost laughable, I know its tricky sometimes to forecast how quickly low cloud will clear etc however two minutes looking at radar and satellite should be enough to see its not going to happen. 

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1 hour ago, DIS1970 said:

Wind has backed round from an NE to E here now, so cloud cover has broken up earlier, and it's fairly sunny (at the moment), so it's fingers crossed for those that have been "stormless".

north sea muck thinning aye, a few holes in it today

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Posted (edited)
40 minutes ago, oliverek7 said:

Definitely bad for some people, but for others it’s been a cracking breakdown for the midlands, Wales, Scotland etc. I would have been stormless too if I hadn’t taken action and driven straight through the Thursday afternoon Surrey storm 😂😂

"Punching the core", eh? 😀 No tornado, probably just a bunch of road works instead...  🙂

I could see that storm from Reigate and it was pretty epic!

As for today, well I have to hang onto the forecasts and hope something shows. Currently it is overcast with severe yellow weather warning drizzle. Dodgy stuff, that.

It doesn't feel like anything can emerge, and Estofex have a very thin forecast for the southern UK.  Fingers crossed!

Edited by StormLoser
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11am Update

Risk of Elevated Convection continues over parts of England and later Wales, Low Risk of Very Heavy Rain / Thunderstorms developing over parts of the SE this afternoon for a time (IF Surface heating can occur)

Models continue to struggle with the very complex thermodynamic structure to the atmosphere over the Central & Southern Part of the UK. This is evidenced by the 00Z Hersmonceux ascent and the Camborne Ascent. The 00Z Unmodified Herstmonceux ascent indicates a very moist profile up to 850mb, and elevated instability to 700mbs, then some slight warming then a further cooling aloft assoc with some skinny elevated instability. This implies there are multiple hurdles to overcome in order to generate anything particularly convective over the Central and Southern parts of the UK through today.

The 00Z Camborne Ascent is extremely saturated in the boundary layer with much drier and buoyant air aloft to the W. (Given the Hodograph)
This more buoyant air is associated with the increasing vorticity assoc with the upper trough and increasing cyclonic vorticity moving towards the SW in assoc with the cyclonic upper vortex located to the west of Brest at present.

Changes are now expected to be slow during the day, pockets of elevated convection will continue to develop but also wane as pockets of mid level instability are triggered by Isentropic uplift as the pseudo upper front moves NW.

There is still scope for some breaks to occur in the SE and around London and that now seems to be the main chance for surface based convection to develop. The Herstmonceux Ascent is very high in Precipitable Water with over 40mm in the column which could be released in a short time should some surface heating occur. Temperatures are already picking up to 21C and if a further 2-3C can occur then the Ascent becomes unstable to the surface and with some indications of a small low developing over SE England this afternoon then local convergence seems likely to occur.

During the evening as the approaching upper trough moves north, this may enhance any convection over the SE for a time before the sun sets. Further scattered elevated convection forced by the isentropic uplift may be augmented by increasing differential thermal advection over parts of Wales into Central England and this may enhance the elevated convection a little - but overall risk of Thunder in this zone appears low.

A very complex thermodynamic environment and once again this evolution is given low confidence given the complexities and subtleties in the atmospheric column. Models are struggling to resolve the complex vertical temperature and moisture variations.

From

PJB  UKWW

Says it all really

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Posted (edited)

met office have updated there warnings removing parts of the midlands for today and having storms and showers moving north tomorrow with higher chance of severe storms more especially Eastern England and later East Midlands into afternoon and evening for tomorrow and this contradictory warning for Monday

which reads thus

Thunderstorms are expected to develop in many areas of England and Wales during Monday. Some slow moving thunderstorms may form during the afternoon before these largely die out through the evening. Many locations within the warning area will miss the thunderstorms altogether, but where they do occur 30-40 mm may fall in an hour with 50-70 mm possible in 3 hours. Thunderstorms may be accompanied by large hail, frequent lightning and gusty winds

this is tomorrows

Areas of heavy showers and thunderstorms are likely to move north across England and Wales during Sunday. Some locations within the warning area may miss the thunderstorms altogether, but where they do occur 30-40 mm of rain may fall in an hour with the potential for 60-90 mm in a few hours. The most likely areas to see the larger totals are in the East of England and then the East Midlands during the afternoon and evening. The thunderstorms may be accompanied by large hail, frequent lightning and gusty winds.

the only possibility for higher rainfall totals maybe slightly warmer temps are expected further East tomorrow but I suggest they really don't know

but given uncertainty even at short range can these warnings really be taken at face value considering their warnings from yesterday and today not really panning out and most probably tomorrow and Monday been the same as well

Edited by Gordon Webb
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42 minutes ago, I remember Atlantic 252 said:

north sea muck thinning aye, a few holes in it today

Sun may be out (not clear), but more breeze & temp struggling a little, just hit a whopping 19C. Storm warning removed for West Mids also, be surprised if anything happens now other than plain old showers.

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1 hour ago, I remember Atlantic 252 said:

north sea muck thinning aye, a few holes in it today

Same here, burning away fast now and more blue sky that patches of crud.  Temps not a patch on yesterday though, only just reaching 20C right now, but it's a nice reprieve from the heat of the last few days.

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Posted (edited)

Yep, some on and off sunshine here, though the cloudy is taking the victory now. Not expecting much of anything particularly convective or thundery in this part today (although the Met Office does go for a chance of some (thundery) showers later tonight over West Midlands). Tomorrow I feel will be more promising for something stormy. I appreciate though we’ve already had a few storms earlier this week (but it’s hard not to want more 😂) and would be cool to see others that have missed out get a turn too.

In actual fact, the weather feels like it’s been behaving the way it does in Animal Crossing New Horizons. Sunny one moment, cloudy the next, or like earlier this week, pouring with rain! And thunder!

Edited by DiagonalRedLine
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