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Storms and Convective Discussion - 20th April 2019 onwards

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31 minutes ago, East_England_Stormchaser91 said:

Elevated stuff gets its fuel from Mid level/Mixed layer CAPE and high theta W values (the plume) which destabilises typically from the west as barometric pressure drops. Surface based activity relies on SB CAPE. If conditions are right though, elevated activity during the day can sometimes transition into a surface based storm, and vice versa when daytime heating wanes. 

Learning new stuff every time - great info thanks ? 

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42 minutes ago, Swansonson69 said:

So surface based relies more on CAPE and elevated doesn't rely on much CAPE?  

From experience elevated needed a good degree of warmth/heat to back it in the atmosphere, not so much near ground level/or channel as water didn't really impact them.. But that heat had to be there.   The elevated storms I have had always followed 1 or 2 days of 25-27C's   apart from 2001 when severe overnight elevated storms happened after a day of 10C and chilly drizzle, but they introduced 25C temps the following day.  Elevated require good backing in front of it, and or behind it.  if it gets neither then they won;t happen.

Edited by StormChaseUK
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I'm progged something half decent for tomorrow night over here in Haute Vienne, both by Meteociel http://www.meteociel.fr/previsions-orage/31908/saint_sulpice_lauriere.htm and Météo France but I'm a long way from the coast and the best our storms tend to be quite orographically driven as we are relatively high up and in a valley surrounded by hills. Nevertheless, I hope you get at least some imports and maybe by the sound of it some homegrown storms as well.

The storms of two days ago in Drôme and Ardèche reminded me so much of 1st of July 2015 https://www.francebleu.fr/infos/climat-environnement/photos-chute-de-grelons-impressionnante-a-romans-sur-isere-1560603655 I've still got the dents in my car bonnet from the Aire Valley supercell!

Happy storm watching...

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45 minutes ago, StormChaseUK said:

From experience elevated needed a good degree of warmth/heat to back it in the atmosphere, not so much near ground level/or channel as water didn't really impact them.. But that heat had to be there.   The elevated storms I have had always followed 1 or 2 days of 25-27C's   apart from 2001 when severe overnight elevated storms happened after a day of 10C and chilly drizzle, but they introduced 25C temps the following day.  Elevated require good backing in front of it, and or behind it.  if it gets neither then they won;t happen.

Arguably the best night storm of the decade here (3rd/4th July 2015) was preceded by quite noticeably cool E/NE winds. 

The night started off clear, and I was observing the distant lightning from as far South as London and Oxfordshire in the cloudtops (very high at 40,000 feet). Then those E/NE winds decided to bring some low cloud and sea mist in with them! Rather annoying, as it impeded the very impressive distant lightning show to the S. 

About an hour later, the mist/Low cloud was still present, but it begun to feel very soupy, as thermal advection in the mid levels drifted N (Storm zone erupting between this and the trough/cold front encroaching in from the W/SW). A short time later I was seeing a faint flash here and there through the low cloud and a continuous very eerie low rumbling was taking place, in what was a very still and calm period (I have a video of shotgun thunder happening at this stage right out of the blue!). Within the next half hour, the sky started lighting up like a trance festival and then all hell broke loose during the next 3 hours. It truly was a storm lovers dream! Interestingly, the winds picked up from the S as the storms hurtled N/NE and swept the low cloud away to give clear cut displays of some spectacular forked and anvil crawler superbolts. Easily one of the best storms of my lifetime. 

But as you say, as long as there is backing from either direction, you are in the game. I tend to find elevated classics often form on the warm front/trough advecting into the cooler air to the N, and as long as the winds are sourced from a continental direction, in order to bring up the proper juice to brew these types of storms (I’m talking about the beasts that have cloudtops over 40,000ft, and not the pathetic attempt of a supercell this week over Lincs, that had tops of only 13,000ft!) 

Edited by East_England_Stormchaser91
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4 minutes ago, East_England_Stormchaser91 said:

Arguably the best night storm of the decade here (3rd/4th July 2015) was preceded by quite noticeably cool E/NE winds. 

The night started off clear, and I was observing the distant lightning from as far South as London and Oxfordshire in the cloudtops (very high at 40,000 feet). Then those E/NE winds decided to bring some low cloud and sea mist in with them! Rather annoying, as it impeded the very impressive distant lightning show to the S. 

About an hour later, the mist/Low cloud was still present, but it begun to feel very soupy, as thermal advection in the mid levels drifted N (Storm zone erupting between this and the trough/cold front encroaching in from the W/SW). A short time later I was seeing a faint flash here and there through the low cloud and a continuous very eerie low rumbling was taking place, in what was a very still and calm period (I have a video of shotgun thunder happening at this stage right out of the blue!). Within the next half hour, the sky started lighting up like a trance festival and then all hell broke loose during the next 3 hours. It truly was a storm lovers dream! Interestingly, the winds picked up from the S as the storms hurtled N/NE and swept the low cloud away to give clear cut displays of some spectacular forked and anvil crawler superbolts. Easily one of the best storms of my lifetime. 

But as you say, as long as there is backing from either direction, you are in the game. I tend to find elevated classics often form on the warm front/trough advecting into the cooler air to the N. 

I remember that storm on July 4th/5th very well and how it first approached with elevated lightning constant flashes whilst it was all calm with no breeze then next thing the storm which moved from London area reached us and lasted a good few hours. Not really had a good storm since then. Would love a repeat of it one day

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Yes the most severe ones will just spark out of thin air literally.  Think 2015 and 2006 (Rugby was the case)

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Just now, StormChaseUK said:

Yes the most severe ones will just spark out of thin air literally.  Think 2015 and 2006 (Rugby was the case)

Yup, you'll be just thinking it's a bust and then suddenly you got this great big storm over head out of nowhere. 

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Evening all. Not had a storm here since 19th of July 2017..and that was a monster, developed in the channel 30 minutes after sunset, and rumbled on for 3 amazing hours

If there's a storm near Worthing tomorrow or Wednesday, everyone who likes this post will get a beer (alternatives are available on request) on me. 

 

That's alright, you're welcome. 

 

Enjoy the now guaranteed storms! ? 

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This was from 27/28 May last year. Glancing blow from a pronounced plume - MUCAPE around 2,000 and incredibly frequent lightning. Sorry, I know it’s the wrong thread...but while we are reminiscing ??

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76096DA6-5D5E-4CBF-9C0F-54F6FFCAB9B8.jpeg

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Models are beginning to shift the storms more west, some have gone as far west as Bristol and the M5 corridor. 

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14 minutes ago, Swansonson69 said:

Yup, you'll be just thinking it's a bust and then suddenly you got this great big storm over head out of nowhere. 

My hopes are on the ICON run which gives East Midlands/Lincolnshire more of a chance with rain heading in a North East direction

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There are a lot of good ingredients at the moment,  moisture, moisture on the ground.   All it needs is the heat to convect like the tropics

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8 minutes ago, StormChaseUK said:

There are a lot of good ingredients at the moment,  moisture, moisture on the ground.   All it needs is the heat to convect like the tropics

Need Heat?!?!?, I'm sweating my bleep off here. It's boiling. Got Windows open and everything. 

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28 minutes ago, Swansonson69 said:

Need Heat?!?!?, I'm sweating my bleep off here. It's boiling. Got Windows open and everything. 

Have you tried a dehumidifier?Screenshot_1.thumb.jpg.f94c0f0852789bf864854a9f690d833b.jpg

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Checking in for tomorrow’s potential, have a rare child free night, so have a bit of scope to get out in the car with the camera. 

Considering taking a trip down to either Shoebury or maybe the east tilbury sea wall at coal house fort, depending on development and placement and timing..... plus how much effort I can muster at 37 weeks pregnant ?

fingers crossed!

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1 hour ago, poseidon said:

Ha! Was gonna post a link to this, love Tony Gilbert’s input and was initially wary of PJB coming along and muscling-in on his ‘patch’ but I’ve got to hand it to both of them they do excellent write-ups of a good many of the forecasts that we get issued.

The detail for tomorrow makes fascinating reading, was learning about adiabatic processes earlier, and now I have a headache ? 

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Well I am not going to try and make heads and tails of the specifics through tomorrow/Wednesday, I will leave this to the experts. In summary I think there are a few areas of potential, with an initial pulse of rain and possible thunder through the middle of the day tomorrow moving north-east across more southern and eastern parts. Areas at risk look quite widespread across southern England but most likely area for thunder to be in a line from approximately the IOW to Norwich south-east (away from the far south-east where it may remain dry). The thunder risk looks low with this, and I think it will be more a rain with the odd possible rumble scenario.

This is then followed by stronger thunderstorms moving up from the Channel. It is here that there appears to be model diversity, with some giving a Kent clipper, others taking in much more of the south-east (maybe as far west as the Midlands). I would be inclined to side with the Met Office, maybe because I want there more widespread forecast to come off ?. Euro4 also brings in a more widespread event than for example the GFS (agreeing with the Met Office) and they do tend to handle convective situations well. I need to be aware though that this model can only depict rain, and rain does not necessarily mean thunderstorms. The GFS would only produce lightning and thunder across Essex/Sussex/Kent.

Finally I would expect the risk of some thunderstorms early in the day on Wednesday across the far east of East Anglia before the mini plume gets shunted off to our continental neighbours, this provided the GFS is not correct.

As many of you know, I am willing to travel to see a storm and my heart is telling me I should head south-east towards London and possibly beyond tomorrow evening. My brain is saying save the petrol and sleepless night, there are better (more reliable) scenarios. I shall revisit following the morning storm forecasts from the experts.

 

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The one fly in the ointment will be the batch of rain moving up over here during mid-morning and the reason why I don't think they'll be any storms for my area ( and possibly others ) later on tomorrow evening. Those in the Southeast fair much better heading in to Tuesday evening, though.

PWAT levels like that would certainly heighten flood risks in localised areas.

viewimage.thumb.png.3f422893f99ae1258546ebaeba1b7c90.png

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Day 2 Convective Outlook

VALID 06:00 UTC Tue 18 Jun 2019 - 05:59 UTC Wed 19 Jun 2019

ISSUED 20:51 UTC Mon 17 Jun 2019

ISSUED BY: Chris/Dan

Firstly, the usual caveats apply to a destabilising plume event. There is an inherently increased level of uncertainty in these type of situations, moreso than most other synoptic events, and even at relatively short time frames. Therefore it is likely parts of this forecast will undoubtedly change from initial thoughts, and further updates / changes may be required. It is often suggested to take a more broadbrush, ingredients-based approach rather than concentrate on specifics, until observational data (radar, satellite etc) provide more convincing clues on how the forecast may evolve. We have attempted to outline the key aspects of this forecast period - but this is subject to change...

... ENGLAND ...

Broad upper troughing will reside over the Atlantic on Tuesday, placing the British Isles under southwesterly flow aloft. Advection of a high Theta-W airmass will likely be occurring on Tuesday morning from France into southern England as a lead impulse drifts northeastwards. Elevated convection will likely occur as a result, initially over the Channel Islands before drifting towards southern England - however, this appears likely to turn increasingly frontal with time as baroclinicity increases on the western flank, with any scope for renewed elevated convection likely to be focussed towards CS / SE England, and later East Anglia. Lightning activity with this first round of activity on Tuesday daytime is uncertain, given somewhat limited instability and subtle forcing. There is a low risk of isolated surface-based development occurring over SE England in the afternoon / early evening should enough insolation materialise.

Later in the day, backing flow as a degenerating shortwave over Biscay approaches will tend to advect an even warmer, moist low-level airmass into southern England, while heights continue to fall aloft. This will be accompanied by stronger forcing for ascent, on the forward-side of the approaching shortwave. It seems likely scattered elevated showers and thunderstorms will develop on Tuesday evening over the English Channel, perhaps organising into an MCS while drifting north / northeastwards across CS / SE England, and then across parts of East Anglia and/or Home Counties overnight. Depending on the forecast evolution, there may be a couple rounds of thunderstorms. Lightning activity with these storms will likely be fairly frequent, with the threat of localised surface water issues should multiple cells move over the same area, and perhaps hail close to 1.5cm in diameter.

There is inevitably some level of uncertainty in these complex setups, with the exact timing and location of thunderstorm potential subject to change. The latest 12z/Mon suite of model guidance has generally trended farther west than earlier guidance from the past few days (with more backed flow allowing cells to track south-north than southwest-northeast), and so the SLGT has been adjusted accordingly. However, it is unclear how reliable this signal is - should this trend persist, then the MDT may also need to be adjusted. Worth noting the 12z EC, which has been remarkably consistent in recent runs, is now much slower with the main shortwave not arriving until Wednesday morning, and therefore produces minimal thunderstorm activity during this particular forecast period.

... ELSEWHERE ...

Elsewhere, scattered heavy showers are likely to develop where low-level convergence or topography will aid forcing - most notably over Wales / NW Midlands / Yorkshire, southern Republic of Ireland and NW Republic of Ireland / Northern Ireland. Later in the night, scattered heavy showers will arrive from the Atlantic onto coastal parts of western Scotland and northwest Ireland as cold advection occurs associated with the sharpening Atlantic upper trough. In all cases, convection will be limited somewhat in depth and so the lightning risk is considered rather low.

http://www.convectiveweather.co.uk/forecast.php?date=2019-06-18

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First time this year where we could go from nothing to widespread elevated storms within an hour tomorrow late evening. 

So, no fretting if the radar/detectors are quiet at 20.00 .

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Hi everyone, hope your all well, 

I wondered if you guy's and girl's can help.

You may have seen from my previous posts I have a child with learning difficulties who hates thunder storms.

I appreciate its difficult to predict but I live in Wendover near to Aylesbury.

So I can prepare him in advance, could any of you experienced people help me to see if we are likely to have anything here? 

I've looked at so many forecasts and they all say different! 

I really do appreciate all your help.

Many thanks so much in advance it means a lot. 

Edited by Sun & Tanned

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11 minutes ago, Andy Bown said:

First time this year where we could go from nothing to widespread elevated storms within an hour tomorrow late evening. 

So, no fretting if the radar/detectors are quiet at 20.00 .

Well said that man...in these kinds of scenarios storms can literally appear in a rash within 10-15 minutes...I know one thing it’s that my windows will be wide open tomorrow night ?? although I remain sceptical about how widespread storms may be as models in my view seem sparing with the MUCAPE distribution.

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