Storm & Convective Discussion - 1 September 2015 onwards

[William Grimsley]

Day 2 Convective Outlook

VALID 06:00 UTC Sun 03 Apr 2016 - 05:59 UTC Mon 04 Apr 2016

ISSUED 14:30 UTC Sat 02 Apr 2016

ISSUED BY: Dan

Falling heights as an upper trough pivots NEwards across Britain and Ireland, coupled with a moist low-level airmass and rather slack surface flow, may allow some deep convection to occur across central Ireland on Sunday daytime, the focus gradually shifting a little westwards with time. Hence scattered showers or pulses of showery rain are likely at times, which may produce some sporadic lightning given 200-300 Jkg-1 CAPE.

 

Moisture plume will also begin to advect north on Sunday afternoon/evening across southern and eastern Britain from the nearby Continent. At the same time, flow will continue to back as upper trough migrates NEwards, steepening mid-level lapse rates and increasing instability. It seems likely that at least some elevated convection will occur but in an environment with rather meagre CAPE (50-100 Jkg-1) and hence even if this does develop, it is still rather questionable as to how much lightning activity there will be, and the overall risk is deemed to low to issue a SLGT (which requires >30%). Main area of interest is from IoW-Humber eastwards, generally the risk increases as you head further E.

[William Grimsley]

There are already quite a few heavy showers approaching the Isles of Scilly suggesting that instability is a lot further west than originally thought.

[NO LONGER POSTING]

12 minutes ago, William Grimsley said:

There are already quite a few heavy showers approaching the Isles of Scilly suggesting that instability is a lot further west than originally thought.

 

 

All forecast as normal, those showers will die out and drift slowly north although I think you're too far West for later.

[William Grimsley]

2 minutes ago, Surrey said:

All forecast as normal, those showers will die out and drift slowly north although I think you're too far West for later.

I would say you were being slightly incorrect there, check the Euro 4, lots of heavy downpours for later as well as the Met Office and BBC both showing the same setup... Hehe! That's the NMM model, I remember last time it predicted severe thunderstorms over this area and nothing materialised.

Having said that, this isn't the best start to the day...

Edited April 3, 2016 by William Grimsley

[NO LONGER POSTING]

1 minute ago, William Grimsley said:

I would say you were being slightly incorrect there, check the Euro 4, lots of heavy downpours for later as well as the Met Office and BBC both showing the same setup... Hehe!

I wouldn't be getting any hopes up, I certainly am not and according to the euro4 I'm smack bang in prime spot. Certainly from last year I learnt the lesson of believing the charts 

[William Grimsley]

2 minutes ago, Surrey said:

I wouldn't be getting any hopes up, I certainly am not and according to the euro4 I'm smack bang in prime spot. Certainly from last year I learnt the lesson of believing the charts 

No, go back on the latest run and it shows a large cluster of heavy, thundery showers over Devon. But, fair enough, just wait and see.

Edited April 3, 2016 by William Grimsley

[NO LONGER POSTING]

3 minutes ago, William Grimsley said:

No, go back on the latest run and it shows a large cluster of heavy, thundery showers over Devon.

Let's wait and see what happens before guessing what ppn will be thundery  every signal chart we have posted needs a giant pinch of salt with it

 

[William Grimsley]

7 minutes ago, Surrey said:

Let's wait and see what happens before guessing what ppn will be thundery  every signal chart we have posted needs a giant pinch of salt with it

 

Fine. Not getting in an argument over the odd rumble here and there...

Also, according to http://www.convectiveweather.co.uk, we have the same thunderstorm risk as you. So, there you have it.

Also, no thunder mentioned on the most recent BBC Weather forecast so it's all completely presumptive.

Edited April 3, 2016 by William Grimsley

[staplehurst]

5 minutes ago, William Grimsley said:

Fine. Not getting in an argument over the odd rumble here and there...

Also, according to http://www.convectiveweather.co.uk, we have the same thunderstorm risk as you. So, there you have it.

Not entirely true, because the map just shows a risk anywhere between 5-30% chance of lightning in the whole 24 hour period from 06 UTC (07:00 BST). It could easily be 5% chance in Devon but 25% chance in Surrey, yet they come under the same threshold. The inclusion of SW England is mainly for the end of tonight into Monday morning as the steeper lapse rates in the post-frontal environment arrive and spread NE. As always, the detail is in the text...

 

"It seems likely that at least some elevated convection will occur but in an environment with rather meagre CAPE (50-100 Jkg-1) and hence even if this does develop, it is still rather questionable as to how much lightning activity there will be, and the overall risk is deemed to low to issue a SLGT (which requires >30%). Main area of interest is from IoW-Humber eastwards, generally the risk increases as you head further E."

[William Grimsley]

1 minute ago, staplehurst said:

Not entirely true, because the map just shows a risk anywhere between 5-30% chance of lightning in the whole 24 hour period from 06 UTC (07:00 BST). It could easily be 5% chance in Devon but 25% chance in Surrey, yet they come under the same threshold. The inclusion of SW England is mainly for the end of tonight into Monday morning as the steeper lapse rates in the post-frontal environment arrive and spread NE. As always, the detail is in the text...

 

"It seems likely that at least some elevated convection will occur but in an environment with rather meagre CAPE (50-100 Jkg-1) and hence even if this does develop, it is still rather questionable as to how much lightning activity there will be, and the overall risk is deemed to low to issue a SLGT (which requires >30%). Main area of interest is from IoW-Humber eastwards, generally the risk increases as you head further E."

My word, I wasn't being percent specific I was just pointing out that the general risk was quite widespread across southern England. Yes, ok just because you both live in SE England you are pointing out that you are going to get hit by several supercells, but that's fine because it won't happen.

[NO LONGER POSTING]

@William Grimsley don't worry bud I'm not arguing I like your posts and vibe, I too love a good thunderstorm and would be good if everyone could get a thunderstorm later, but unfortunately that won't be the case

 

Risk is low tonight and this afternoon it's just not the best time of year to get this kind of setup although I'm pretty confident a rough strike here and there can't be ruled out

As ever the case, good luck all eyes to the sky and radar.

We are firing up the BBQ at lunch if it gets warm enough! First one for 2016!

[William Grimsley]

Just now, Surrey said:

We are firing up the BBQ at lunch if it gets warm enough! First one for 2016!

Good luck with that!

[Supacell]

Any risk today is low - as pointed out in the Convective Weather forecast posted earlier. If we were to be picky then the SE has a slightly higher chance than the SW but in the grand scheme of things the chance is still low. I live in the Midlands and so not the SE or the SW and I would love the chance to chase today. I could in theory drive the same distance to the SW or the SE but I won't be as I would have a very high (around 95%) of seeing nothing whichever direction I took myself.

Tomorrow poses better chances for more widespread thunderstorms, although I am at work. However, reasons to be positive are that the GFS charts are littered with potential during the next two weeks (FI in know), some people have already had a storm this year and it is only April 3rd. Last year didn't get going until around mid-May if I remember correctly.

 

Edited April 3, 2016 by Supacell

[William Grimsley]

1 minute ago, Supacell said:

Any risk today is low - as pointed out in the Convective Weather forecast posted earlier. If we were to be picky then the SE has a slightly higher chance than the SW but in the grand scheme of things the chance is still low. I live in the Midlands and so not the SE or the SW and I would love the chance to chase today. I could in theory drive the same distance to the SW or the SE but I won't be as I would have a very high (around 95%) of seeing nothing whichever direction I took myself.

Tomorrow poses better chances for more widespread thunderstorms, although I am at work. However, reasons to be positive are that the GFS charts are littered with potential during the next two weeks (FI in know), some people have already had a storm this year and it is only April 3rd. Last year didn't get going until around mid-May if I remember correctly.

 

Another great post, Supacell! As I pointed out, no place has a much higher chance than anywhere else so it will just be radar watching.

[Supacell]

3 minutes ago, William Grimsley said:

Another great post, Supacell! As I pointed out, no place has a much higher chance than anywhere else so it will just be radar watching.

Thank you. Yes, admittedly I will be radar watching later today as there is always that chance something could happen and would be very disappointed in myself if I missed it 

[William Grimsley]

7 minutes ago, Supacell said:

Thank you. Yes, admittedly I will be radar watching later today as there is always that chance something could happen and would be very disappointed in myself if I missed it 

I've tried to have a look at your YouTube videos, but they're all private?

[Harry]

Interesting day ahead, shame it isn't Mid Summer really.

Charts today in the round haven't changed much from yesterday.

Consensus generally from the models is Hampshire east is best for lightning prospects. GFS the most stingy SBCAPE/MLCAPE wise whereas (perhaps unsurprisingly) NMM/WRF more bullish.

Tomorrow looks a little better too from my perspective but that said far SE still likely to be outside the crosshairs tomorrow, whereas Wales/SW/C England best placed.

[William Grimsley]

2 minutes ago, Harry said:

Interesting day ahead, shame it isn't Mid Summer really.

Charts today in the round haven't changed much from yesterday.

Consensus generally from the models is Hampshire east is best for lightning prospects. GFS the most stingy SBCAPE/MLCAPE wise whereas (perhaps unsurprisingly) NMM/WRF more bullish.

Tomorrow looks a little better too from my perspective but that said far SE still likely to be outside the crosshairs tomorrow, whereas Wales/SW/C England best placed.

I agree. Just checked the latest BBC Weather forecast. Lots of heavy and showery rain pushing up through Devon this afternoon, however this turns more widespread and possibly thundery as it moves northward and eastward. Monday still looks interesting especially in the morning with a possible downpour with hail/thunder thrown in during the afternoon.

Edited April 3, 2016 by William Grimsley

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Sun 03 Apr 2016 - 05:59 UTC Mon 04 Apr 2016

ISSUED 07:50 UTC Sun 03 Apr 2016

ISSUED BY: Dan

UPDATE 07:50 UTC No change to overall expectations highlighted below, LOW area has been extended farther N across northern England into SE Scotland for very low chance of embedded convective activity overnight

Falling heights as an upper trough pivots NEwards across Britain and Ireland, coupled with a moist low-level airmass and rather slack surface flow, may allow some deep convection to occur across central Ireland on Sunday daytime, the focus gradually shifting a little westwards with time. Hence scattered showers or pulses of showery rain are likely at times, which may produce some sporadic lightning given 200-300 Jkg-1 CAPE.

Moisture plume will also begin to advect north on Sunday afternoon/evening across southern and eastern Britain from the nearby Continent. At the same time, flow will continue to back as upper trough migrates NEwards, steepening mid-level lapse rates and increasing instability. It seems likely that at least some elevated convection will occur but in an environment with rather meagre CAPE (50-100 Jkg-1) and hence even if this does develop, it is still rather questionable as to how much lightning activity there will be, and the overall risk is deemed to low to issue a SLGT (which requires >30%). Main area of interest is from IoW-Humber eastwards, generally the risk increases as you head further E.

http://www.convectiveweather.co.uk/forecast.php?date=2016-04-03

Edited April 3, 2016 by Summer Sun

[A.J]

1 hour ago, staplehurst said:

Not entirely true, because the map just shows a risk anywhere between 5-30% chance of lightning in the whole 24 hour period from 06 UTC (07:00 BST). It could easily be 5% chance in Devon but 25% chance in Surrey, yet they come under the same threshold. The inclusion of SW England is mainly for the end of tonight into Monday morning as the steeper lapse rates in the post-frontal environment arrive and spread NE. As always, the detail is in the text...

 

"It seems likely that at least some elevated convection will occur but in an environment with rather meagre CAPE (50-100 Jkg-1) and hence even if this does develop, it is still rather questionable as to how much lightning activity there will be, and the overall risk is deemed to low to issue a SLGT (which requires >30%). Main area of interest is from IoW-Humber eastwards, generally the risk increases as you head further E."

Liking your forecasts Dan, nice to see you back posting on the forum 

Edited April 3, 2016 by ajpoolshark

[staplehurst]

23 minutes ago, ajpoolshark said:

Liking your forecasts Dan, nice to see you back posting on the forum 

Thanks AJ! Just trying to manage expectations this early in the season ha!

Fingers crossed for a good season this year 

[Azazel]

1 hour ago, William Grimsley said:

My word, I wasn't being percent specific I was just pointing out that the general risk was quite widespread across southern England. Yes, ok just because you both live in SE England you are pointing out that you are going to get hit by several supercells, but that's fine because it won't happen.

Crikey.

Tempted to dust off the Go Pro and set up a timelapse with the external battery. You never know! 

[Supacell]

3 hours ago, William Grimsley said:

I've tried to have a look at your YouTube videos, but they're all private?

Whoops, making them public may help! Try again now they should all be available.

[lassie23]

Gordon Webb is online, storm season must be underway

[William Grimsley]

4 minutes ago, lassie23 said:

Gordon Webb is online, storm season must be underway

Ah, I remember Gordon from 2014, I hope he got some help!