Convective/Storm Discussion Thread - 8th July onwards

[Julian 777]

1 minute ago, Nick F said:

What makes you think that? Don't think there's any particular focus, will have to wait and see, GFS CAPE charts would suggest more energy aloft east of I.O.W., but as ever with storms in the UK, other than N France probably getting a lot of activity, as the norm, it's up in the air for now where the focus will be Tuesday night

Just saw a BBC forecast that made me wonder if that was the case , but yes its a case of lightning radar on and enjoy watching things develop..lol

[Nick F]

1 minute ago, Jules777 said:

Just saw a BBC forecast that made me wonder if that was the case , but yes its a case of lightning radar on and enjoy watching things develop..lol

BBC forecast I saw showed storms initially across SW England, but developing and moving north further east Tuesday night. The Beeb forecasts often don't always pan out like they depict with storms, which are tricky to model by even the best supercomputers for the UK, so will be IMO, as usual, a case of nowcasting tomorrow evening!

[Harry]

26 minutes ago, Flash bang flash bang etc said:

What does everyone think we'll get from Estofex for tomorrow?

I reckon it's a level 2... 

Lvl 1 I reckon but quite extensive. 

[Andy Bown]

Nick's convective forecast reminds me very much of the early hours of Saturday 27th May ; spectacular electrical storms in the SW which gained in rainfall but lost electrification as they moved N/NE.

[TJS1998Tom]

Weather warnings are now in place for tomorrow

[SenlacJack]

2 hours ago, Windblade said:

I think on average every year we get about three or four heatwaves in the southeast with temps exceeding 32c on some days. These heatwaves can last for weeks at a time so although I don't have any exact figures to hand I do think the number of unbearably hot days in the south east exceeds 10 or 20 days. Forgive me for being a miserable old man about such things, I just find it very difficult to cope with extreme heat. 

Sorry, no offence intended but heatwaves lasting for weeks at a time...... really ?

Back on topic fingers crossed for those of us wanting thunderstorms in the next couple of days. It's still looking quite favourable for the west in particular though i'm quietly confident for my location here on the south coast.

The potential for this being a night time event is an added bonus.

[Flash bang flash bang etc]

As long as timings stay as they are (no late-afternoon tues, or post-4AM storms weds) I'll bank what we've got so far.

A shift to the east from current forecasts would be nice - but I'm expecting to chase to find the best bits anyway so not too worried about that.

My only concern is if it's in the far, far west (past Devon) - as then it's gonna take a couple of hours to get there - but a storm's a storm and I'm sure it will be more central and widespread than that

 

[wimblettben]

Well based on the forecasts I am expecting to at least witness something in the distance over this period if we don't get anything directly overhead.

I think I would be very unlucky to get nothing out of this now, but I think I am just going to wait and see what happens on the day and night of Tuesday and Wednesday and won't check anymore forecasts as its just going to stress me out.

[Derecho]

Last weeks plume turned out to be quite a good one in the end with the exception of the far south.

I also think what we have is a really good setup with SLP well below 1010mb, which means the chances of any cap being broken are higher.

Cape values aren't that high over Southern England but we do have really high Cape just across the channel. The fact we have a strong south-easterly wind bodes well for French imports.

Also the 850s are really high, it would be good if they marched north a little earlier but its good enough. 18C in parts of the south in the early hours of Wednesday morning.

 

Then on Wednesday the setup looks ideal for the North-East especially for some home growns.

Again some places may be let down or miss out... however I believe this is the best setup of the summer so far and it bears a lot of similarity to July 2014.

[Pat Butcher]

1 hour ago, Flash bang flash bang etc said:

What does everyone think we'll get from Estofex for tomorrow?

I reckon it's a level 2... 

Current model disagreement on shear. If GFS maintains little/no shear, then maybe a Level 1, maybe a 50% lightning zone. NMM, meanwhile, goes for a perfect combo of CAPE/precip/shear/helicity which will definitely push southern UK into level 2 and possibly northern England into Level 1.

[Windblade]

29 minutes ago, SenlacJack said:

Sorry, no offence intended but heatwaves lasting for weeks at a time...... really ?

Back on topic fingers crossed for those of us wanting thunderstorms in the next couple of days. It's still looking quite favourable for the west in particular though i'm quietly confident for my location here on the south coast.

The potential for this being a night time event is an added bonus.

No offence taken and as I said I don't have actual figures to hand but I'm pretty sure the heatwaves we've always had every summer have lasted weeks at a time, yes (at least they felt like it).

[Windblade]

21 minutes ago, Quicksilver1989 said:

Last weeks plume turned out to be quite a good one in the end with the exception of the far south.

I also think what we have is a really good setup with SLP well below 1010mb, which means the chances of any cap being broken are higher.

Cape values aren't that high over Southern England but we do have really high Cape just across the channel. The fact we have a strong south-easterly wind bodes well for French imports.

Also the 850s are really high, it would be good if they marched north a little earlier but its good enough. 18C in parts of the south in the early hours of Wednesday morning.

 

Then on Wednesday the setup looks ideal for the North-East especially for some home growns.

Again some places may be let down or miss out... however I believe this is the best setup of the summer so far and it bears a lot of similarity to July 2014.

I think as you eluded to in your post, our best chances are for french imports in the evening on tuesday (added bonus - french storms are often mcs in nature and put on the most spectacular light shows compared to our usual average run-of-the-mill pulse type homegrown storms, although we do have the odd exception every now and again). For now though I'm going to take things with a pinch of salt - been let down far too many times already this year and last with similar setups only to amount to nothing. I'm going to play the wait-and-see game and see if it pays off.

Edited July 17, 2017 by Windblade

[Alec]

25 minutes ago, Nick F said:

Believe it or not, elevated strong storms, which are fuelled by large amounts of CAPE aloft, can be prolific lightning producers, particularly away from heavy rain cores - this is because electrical charges tend to dissipate through rainfall without a lightning strike (water being a good conductor) - whereas drier air the electrical charge building between the elevated base and ground has to overcome it with a lightning strike.

Elevated storms can indeed produce intense lightning activity, but I don't think it is for the reasons you suggest. Cloud charging and lightning initiation is still an active area of research, but recent studies from the US indicate that the important aspect is the amount of water content reaching an altitude where temperatures are below freezing (the mixed phase region of the cloud), since it is the interaction of ice particles of different sizes in the updraft which produces strong electrical charging. For a given updraft speed, an elevated cloud base helps this charging since there is less water condensing below the freezing level, which can be removed as rainfall instead of supplying the mixed phase region. Additionally, the higher cloud base promotes broader updrafts with less entrainment of ambient air, allowing more water to reach the mixed phase region thereby producing more ice for charging.

Whilst some of the cloud's charge is lost through charge transfer back to ground on falling precipitation particles (the "precipitation current"), lightning is often concentrated around heavy convective rain cores since this is usually near to where the greatest updrafts are found and therefore the strongest charged regions within the cloud. Raindrops no not alter the ambient electric field or air electrical conductivity through dissipation; air conductivity is instead determined by the amount of ions available, with liquid and ice particles implicated as a possible source of lightning initiation due to the enhanced electric field surrounding them.

Hope this is of interest!

 

[Dangerous55019]

Afternoon all 
I'm a bit short on time today, so hence a short post...
Right as normal, I'm using the 00z run for consistency, and I've cherry picked these two charts...


Now the one thing that strikes me looking at these (or certainly the top chart) is the stupidly high Cape and LI figures forecast for Northern France (Cap in place?) but when you look at the storm risk charts, its looking like the English Channel could be the prime place to be! 
So for Tuesday, being as its only tomorrow, I'd say anywhere along the South coast (from Cornwall to Kent) could hopefully get a really impressive light show. 

And finally, I have cherry picked this chart for Wednesday... 

This shows the storm potential moving northwards. 
I personally think that these will be home grown storms, whether or not these will be homegrown MSC or Super cells, I dunno.
But I do think that for the rest of the UK that Wednesday shows the most potential. 

I'll post tomorrow when hopefully the details will finally start to get nailed on, but I'm really hoping that this could be the big thundery breakdown that we're all craving. 

Sorry if this post seems rushed only I'm typing at one hell of speed here, and I do hope that you're all able to read this at the same speed as I've typed it. Lol 

Edited July 17, 2017 by Dangerous55019
Typo

[Hodgheg]

I'm going to heading back up to Yorkshire this week but i've pushed it back a day to Wednesday to give me the best chance of seeing storms.  Best case scenario would be decent overnight storms on Tuesday night down here and then by the time i get to Yorkshire on Wednesday, afternoon storms up there. 

[Julian 777]

3 minutes ago, John Hodgson said:

I'm going to heading back up to Yorkshire this week but i've pushed it back a day to Wednesday to give me the best chance of seeing storms.  Best case scenario would be decent overnight storms on Tuesday night down here and then by the time i get to Yorkshire on Wednesday, afternoon storms up there. 

good luck ,hope it works out for you in both locations..At the moment at least its looking good.

[Flash bang flash bang etc]

Hope everyone gets a storm, and nobody's tree gets stuck by lightning 

[MP-R]

1 hour ago, Andy Bown said:

Nick's convective forecast reminds me very much of the early hours of Saturday 27th May ; spectacular electrical storms in the SW which gained in rainfall but lost electrification as they moved N/NE.

Seeing the same Andy. Managed to benefit from both a beautiful lightning display then a downburst of rain to follow when lightning decreased but the thunder was a lot louder and sounded more surface based.

[Chris K]

1 hour ago, Andy Bown said:

Nick's convective forecast reminds me very much of the early hours of Saturday 27th May ; spectacular electrical storms in the SW which gained in rainfall but lost electrification as they moved N/NE.

I remember staying up late, only to watch sods law unfold before my eyes and the storms dwindled away literally as they touched the edge of Bristol. We did manage a few flashes and bangs North of the city, but nowhere near to the scale of what some on the S coast experienced that night!

[TJS1998Tom]

Hoping that we get a few early morning storms here, however I dont think we will.

[Flash bang flash bang etc]

Those Somerset / Cornwall storms on the 27th were literally awesome. I wasn't there when it happened but watched what I could via webcams at the time, and I've seen some of the vids since.

I think they were a one-off, but I do have a feeling that if tomorrow / weds comes off it's gonna be a good showing at the very least, and hints that we may be entering a new phase of potential for Southern UK areas for the second half of summer.

I'm basing this on the fact that sea temps are up during mid-to-late-summer, which (for my area at least) gives us a fighting chance at getting imports - as well as making the channel a good breeding ground for electrical storms.

Who knows really, but I do fancy our odds 

[Nick F]

2 hours ago, Alec said:

Elevated storms can indeed produce intense lightning activity, but I don't think it is for the reasons you suggest. Cloud charging and lightning initiation is still an active area of research, but recent studies from the US indicate that the important aspect is the amount of water content reaching an altitude where temperatures are below freezing (the mixed phase region of the cloud), since it is the interaction of ice particles of different sizes in the updraft which produces strong electrical charging. For a given updraft speed, an elevated cloud base helps this charging since there is less water condensing below the freezing level, which can be removed as rainfall instead of supplying the mixed phase region. Additionally, the higher cloud base promotes broader updrafts with less entrainment of ambient air, allowing more water to reach the mixed phase region thereby producing more ice for charging.

Whilst some of the cloud's charge is lost through charge transfer back to ground on falling precipitation particles (the "precipitation current"), lightning is often concentrated around heavy convective rain cores since this is usually near to where the greatest updrafts are found and therefore the strongest charged regions within the cloud. Raindrops no not alter the ambient electric field or air electrical conductivity through dissipation; air conductivity is instead determined by the amount of ions available, with liquid and ice particles implicated as a possible source of lightning initiation due to the enhanced electric field surrounding them.

Hope this is of interest!

 

Thanks for that info, I don't doubt that you provide some credible reasoning for why elevated storms produce intense lightning. The theory I mentioned was not my own, but from what I've read from a Meteorologist somewhere on an American forum, which I admit may not be widely accepted.

Lightning production is a fascinating subject and certainly very complex and perhaps still a phenomenon, like tornadoes, which may not be fully understood. One thing from being out in the U.S. chasing storms is observing that lightning is often most powerful / prolific in the updraft area of the storm that is often rain-free too. Strong updrafts, sometimes in the mesocyclone area which produce tornadoes, I've seen some frequent positive bolts - perhaps the region of the storm where the updraft is pushing up at greatest speed into levels below freezing creating charge separation. Also, some of the most dangerous positive bolts are well-known to arc at long heights from the anvil of a strong storm well away from any rain/hail core, indeed sometimes away from the storm - resulting in those 'bolts out of the blue' or in blue skies. Basically if you can hear thunder - you are always in very slight danger, if exposed, of being struck by lightning.

Edited July 17, 2017 by Nick F

[Harry]

16 minutes ago, Nick F said:

Thanks for that info, I don't doubt that you provide some credible reasoning for why elevated storms produce intense lightning. The theory I mentioned was not my own, but from what I've read from a Meteorologist somewhere on an American forum, which I admit may not be widely accepted.

Lightning production is a fascinating subject and certainly very complex and perhaps still a phenomenon, like tornadoes, which may not be fully understood. One thing from being out in the U.S. chasing storms is observing that lightning is often most powerful / prolific in the updraft area of the storm that is often rain-free too. Strong updrafts, sometimes in the mesocyclone area which produce tornadoes, I've seen some frequent positive bolts - perhaps the region of the storm where the updraft is pushing up at greatest speed into levels below freezing creating charge separation. Also, some of the most dangerous positive bolts are well-known to arc at long heights from the anvil of a strong storm well away from any rain/hail core, indeed sometimes away from the storm - resulting in those 'bolts out of the blue' or in blue skies. Basically if you can hear thunder - you are always in very slight danger, if exposed, of being struck by lightning.

I remember watching an interesting tv programme some time ago which discussed theories that lightning frequency was linked in some way to the ionosphere and magnetosphere, with some meteorologists noting that there were patterns in lightning activity globally, i.e there were peaks and troughs in terms of lightning activity which was not simply accounted for by seasonal variations

 

[Alec]

6 minutes ago, Harry said:

I remember watching an interesting tv programme some time ago which discussed theories that lightning frequency was linked in some way to the ionosphere and magnetosphere, with some meteorologists noting that there were patterns in lightning activity globally, i.e there were peaks and troughs in terms of lightning activity which was not simply accounted for by seasonal variations

 

Yes, there's evidence that lightning activity is surprisingly strongly influenced by the sun's magnetic field polarity, with observational data identifying that lightning flashes were up to twice as frequent over the UK when the sun's magnetic field was pointing towards the Earth compared to when it pointed away. Of course, the magnetic field can't generate the storms themselves (that's left to it's visible spectrum!) but the change in field seems to promote electrification of existing storms or at least help their discharge through lightning. The physical mechanism for this is still unknown, but may be due to the influence of high energy particles altering the environment of the upper portion of the cloud. If you're interested you can check out this link to a recent research papers for more info from a UK perspective:

http://iopscience.iop.org/article/10.1088/1748-9326/9/11/115009/meta

http://onlinelibrary.wiley.com/doi/10.1002/2015GL066802/abstract 

[East_England_Stormchaser91]

40 minutes ago, Alec said:

Yes, there's evidence that lightning activity is surprisingly strongly influenced by the sun's magnetic field polarity, with observational data identifying that lightning flashes were up to twice as frequent over the UK when the sun's magnetic field was pointing towards the Earth compared to when it pointed away. Of course, the magnetic field can't generate the storms themselves (that's left to it's visible spectrum!) but the change in field seems to promote electrification of existing storms or at least help their discharge through lightning. The physical mechanism for this is still unknown, but may be due to the influence of high energy particles altering the environment of the upper portion of the cloud. If you're interested you can check out this link to a recent research papers for more info from a UK perspective:

http://iopscience.iop.org/article/10.1088/1748-9326/9/11/115009/meta

http://onlinelibrary.wiley.com/doi/10.1002/2015GL066802/abstract 

Probably explains why we used to get much more in the way of storm activity back at the solar peak (90's) than what we have been used to recently.

It isnt selective memory either, I remember many times in the summers as a child being terrified and dashing into the parents' room because of the intense lightning and thunder roaring on for hours and hours! There's also a page on that library showing MCS's affecting the UK from 1981-1997 or something, and there really was quite a few, some of them so big that they were covering areas near enough the size of Ireland I believe! So pretty much all of the Midlands and east Anglia at once! 

Edited July 17, 2017 by East_England_Stormchaser91