Storms and Convective discussion - September 2023

[Ben Sainsbury]

Airmass is very quite unstable it appears this evening and tonight, just a lack of forcing is an issue. Met Office still has a trough moving northwards around midnight across SW England & Wales and often these small-scale features are hard to pick up on the models. Still hoping for a few surprises tonight. If AROME is anything to go by, then watching the Bay of Biscay rest of this afternoon/evening, might be an indication of what's to come tonight.

Edited September 6, 2023 by Ben Sainsbury

[minus10]

29 minutes ago, Flash bang flash bang etc said:

Gotta be honest it’s looking good for the CS on satellite - stream of cloud right up from western France.

Nothing to get too excited about but worth keeping an eye on

Pretty thin gruel really when you consider the storms..some very destructive of course over Europe and the med over the last few weeks..

With temps like these over the next few days you would expect more quite frankly..

...however we all know that its not just about temps. ..forcing, moisture, topography, cape etc etc

It would be so fitting i think to have the breakdown of this quite exceptional September hot spell accompanied by active storms but i suspect, to the much frustration for many areas, that wont be the case..

..working outside as a gardener it is pretty tough going in this heat which i enjoy if i have nothing to do..and it would be worth it if i knew there were some cracking storms to end it..i suppose i look back to when i was a kid in the 70s and 80s with rose tinted glasses no doubt but we seemed to get some crackers after hot periods...the hazy sky turning darker slowly with distant rumbling becoming louder...ofter the night storms imports from France and huge storms they were...

...still hopefull but dont hold out much hope....contradictory eh...well this is the weather...

Edited September 6, 2023 by minus10

[Alderc 2.0]

Quite a bit of mid level instability pushing north at the moment. 

[mike5900]

Showers  now crossing the English  Channel. 

[ChannelThunder]

If you live in Devon or Cornwall you might want to check out the 12z Arome, which ignites the trough right over your heads overnight

[viking_smb]

1 minute ago, ChannelThunder said:

If you live in Devon or Cornwall you might want to check out the 12z Arome, which ignites the trough right over your heads overnight

have you got a link to that please m8

[ChannelThunder]

3 minutes ago, viking_smb said:

have you got a link to that please m8

On mobile at the mo but hopefully this works

https://www.wxcharts.com/?panel=default&model=arome,arome,arome,arome&region=eng&chart=convective_overview,accprecip,wind10mkph,snowdepth&run=12&step=016&plottype=10&lat=51.500&lon=-0.250&skewtstep=0

 

[viking_smb]

4 minutes ago, ChannelThunder said:

On mobile at the mo but hopefully this works

https://www.wxcharts.com/?panel=default&model=arome,arome,arome,arome&region=eng&chart=convective_overview,accprecip,wind10mkph,snowdepth&run=12&step=016&plottype=10&lat=51.500&lon=-0.250&skewtstep=0

 

thanks mate

[viking_smb]

34 minutes ago, ChannelThunder said:

On mobile at the mo but hopefully this works

https://www.wxcharts.com/?panel=default&model=arome,arome,arome,arome&region=eng&chart=convective_overview,accprecip,wind10mkph,snowdepth&run=12&step=016&plottype=10&lat=51.500&lon=-0.250&skewtstep=0

 

according to the met office inshore forecast, the showers are going to be west of lands end and in the irish sea as I use the inshore forecast frequently in work 

Edited September 6, 2023 by viking_smb

[Ben Sainsbury]

Signs of mid-level instability here too. Satellite is promising and as @ChannelThunder said, AROME 12z is promising too. UKV remains decent for far SW. Fingers crossed.

Looking further ahead, Saturday night and Sunday looking more of a widespread risk.

[viking_smb]

10 minutes ago, Ben Sainsbury said:

Signs of mid-level instability here too. Satellite is promising and as @ChannelThunder said, AROME 12z is promising too. UKV remains decent for far SW. Fingers crossed.

Looking further ahead, Saturday night and Sunday looking more of a widespread risk.

with the widespread risk, I think it will be more northern areas that will cop it, as UKV showing some activity in the south on sat night, but that will change closer to the time

Edited September 6, 2023 by viking_smb

[ChannelThunder]

17 minutes ago, Ben Sainsbury said:

Signs of mid-level instability here too. Satellite is promising and as @ChannelThunder said, AROME 12z is promising too. UKV remains decent for far SW. Fingers crossed.

Looking further ahead, Saturday night and Sunday looking more of a widespread risk.

Saturday looks good to me overnight, there's another trough floating its way up, this time a little more centrally to tonight's one.

[Flash bang flash bang etc]

I really don’t understand anyone who takes anything but a grain of salt with any forecast beyond 6 hrs … Saturday may as well be mid-November in terms of what we know will happen, and even in terms of what the supercomputers modelling the models know what will happen.

That said - it’s good to look into ‘close FI’ (as I’m now calling it) as a guide to what may be in store - but seriously don’t expect any of it to be even marginally correct.

Hot, anomalous bodies of water are proving to be one of mankind’s biggest headaches at the moment - in terms of forecasting. Thunderstorms are complicated beasts at the best of times, but I can’t even begin to imagine the complex interplay between polar, stateside and European airmasses and all those oceanic thermal influences that will play out over the coming days to produce whatever the weather will do by Saturday.

Things do look good at the moment from an IMBY perspective, but it will change many times before we get there - and the weather isn’t fair, so the likelihood is a warm evening with the odd shower and nothing more

(that’s my forecast and I’m sticking with it lol)

[ChannelThunder]

3 minutes ago, Flash bang flash bang etc said:

I really don’t understand anyone who takes anything but a grain of salt with any forecast beyond 6 hrs … Saturday may as well be mid-November in terms of what we know will happen, and even in terms of what the supercomputers modelling the models know what will happen.

That said - it’s good to look into ‘close FI’ (as I’m now calling it) as a guide to what may be in store - but seriously don’t expect any of it to be even marginally correct.

Hot, anomalous bodies of water are proving to be one of mankind’s biggest headaches at the moment - in terms of forecasting. Thunderstorms are complicated beasts at the best of times, but I can’t even begin to imagine the complex interplay between polar, stateside and European airmasses and all those oceanic thermal influences that will play out over the coming days to produce whatever the weather will do by Saturday.

Things do look good at the moment from an IMBY perspective, but it will change many times before we get there - and the weather isn’t fair, so the likelihood is a warm evening with the odd shower and nothing more

(that’s my forecast and I’m sticking with it lol)

I see what you're saying, but 3-5 days out, if there's some sort of consistency combined with cross-model agreement, then I take things more seriously, still with a grain of salt though of course. 

A good example is tonight's little trough in the southwest; it was picked up by models circa. 4/5 days ago IIRC, and its positioning and timing largely hasn't changed since then. Of course, details on a local scale when the time comes are always all to play for though when it comes to thunderstorms, becoming a nowcasting situation!

[Flash bang flash bang etc]

Skies looking increasingly potent overhead. Long way to go to produce any lightning but I’ve seen skies like this before on days when we have had results

[alexisj9]

29 minutes ago, Flash bang flash bang etc said:

I really don’t understand anyone who takes anything but a grain of salt with any forecast beyond 6 hrs … Saturday may as well be mid-November in terms of what we know will happen, and even in terms of what the supercomputers modelling the models know what will happen.

That said - it’s good to look into ‘close FI’ (as I’m now calling it) as a guide to what may be in store - but seriously don’t expect any of it to be even marginally correct.

Hot, anomalous bodies of water are proving to be one of mankind’s biggest headaches at the moment - in terms of forecasting. Thunderstorms are complicated beasts at the best of times, but I can’t even begin to imagine the complex interplay between polar, stateside and European airmasses and all those oceanic thermal influences that will play out over the coming days to produce whatever the weather will do by Saturday.

Things do look good at the moment from an IMBY perspective, but it will change many times before we get there - and the weather isn’t fair, so the likelihood is a warm evening with the odd shower and nothing more

(that’s my forecast and I’m sticking with it lol)

Re storms I fully agree, even 6 nours out isn't right often. Models are good for knowing when conditions are about, but the actual storms are more or less now cast, see what the sky is doing situations.

8 minutes ago, Flash bang flash bang etc said:

Skies looking increasingly potent overhead. Long way to go to produce any lightning but I’ve seen skies like this before on days when we have had results

I still have milky white.

[minus10]

Although high level, pity these two bands moving north (second one slight east component i think) couldnt develop some major lightning storms to coincide with darkness here..

[Flash bang flash bang etc]

18 minutes ago, alexisj9 said:

Re storms I fully agree, even 6 nours out isn't right often. Models are good for knowing when conditions are about, but the actual storms are more or less now cast, see what the sky is doing situations.

I still have milky white.

We are right under that central band. Not knowing the forecast I would assume there were storms due. Great sky

[Ben Sainsbury]

First sferics off Cornwall. Elsewhere, showers over NW France beginning to look more potent.

[Sam jackson88]

starting to feel opresive and muggy as hell here in southampton, air feels very heavy. lets hope the cells coming off france become electirfied big time.

[Flash bang flash bang etc]

2 minutes ago, Sam jackson88 said:

starting to feel opresive and muggy as hell here in southampton, air feels very heavy. lets hope the cells coming off france become electirfied big time.

Don’t forget we have a low probability of a slight chance that it might be possible that there may be almost a storm.

Good odds for the CS

[Sam jackson88]

Just now, Flash bang flash bang etc said:

Don’t forget we have a low probability of a slight chance that it might be possible that there may be almost a storm.

Good odds for the CS

at least there is a chance XD even if there is a 1% chance i have hope. need a good storm for the cs region deffo as we have missed every storm so far this year

 

[Eagle Eye]

Sorry for the late forecast. Made this earlier today but was waiting for Jay to do the map. Was playing cricket so couldn't help him when making it either. 

Convective Outlook ️ 

A large Theta-E airmass advection will allow for near tropical moisture rates along the Irish Sea and the coasts of Eastern Ireland and western England up to western Scotland. 1000+ J/KG of MLCAPE looks to advect and create showers and storms Wednesday night/Thursday morning, with potentially frequent lightning in some of them. They will move roughly north as it goes into Thursday morning.

 

This kind of saturation and moisture levels tends to allow for very frequent lightning once the cap is broken. If the capping isn't broken then it's a bust but it looks fairly likely to break and so some storms around the previously mentioned coasts could have quite frequent lightning rates.

 

Further into Ireland may see some scattered storms at random points throughout the night. These may have fairly frequent lightning, having good lapse-rates along with near tropical like moisture amounts and fairly good MLCAPE.

 

850's Theta-W at 16°C+ is enough for the elevated storms to form. Lots of elevated CAPE and good hydrolapse rates continue to suggest frequent lightning rates at times possible.

 

The inflow layer is fairly large with good below zero CAPE. Along with good hydrolapse rates and a supportive hodograph, severe hail is quite possible.  Hail could potentially be up to 2 inches but it's probably unlikely to reach it's potential but I suspect some 1.5 inch hail is possible. Some surface flooding is also possible.

Timing wise and it's on Wednesday night, storms should form in the southern part of the Irish Sea and into the SW of England, moving north towards SW Scotland potentially by around mid morning. These storms will be mostly longer-lasting pulse-type reaching 9-10 km before new storms should form after one falls. They might form into a weak but wide MCS with some near severe wind gusts depending on DCAPE strength.

[Flash bang flash bang etc]

Tony G at UKWW suggested a lot of hail will melt before hitting people on the ground. So… expect soggy people, albeit unhurt.

[pad199207]