Convective / Storm Discussion Thread - 31st May 2017 onwards

[snowprincesspboro]

Flying ants here today are horrendous... never seen so many

[poseidon]

Euro 4 does not look encouraging for late afternoon/evening surface based storms in the south. And even early morning elevated ones are sketchy. Will be interesting to see which model(s) come out on top. Possible Thursday evening organised storms in the Midlands?

Edited July 5, 2017 by poseidon

[Thunderstruck]

No flying ants here today thank goodness (hate them!). Looking up, there's been quite a bit of accas and cirrus around today and humidity has been through the roof. Hope we see something tomorrow!

[jamesthemonkeh]

4 minutes ago, Mapantz said:

Flying ant day then? I had two of those last year, neither of which coincided with any thunder potential.

As far as I am aware, different ant species have different flying days, with the most common ant species being around the end of July - and I believe that it is temperature-driven.

[ThundersnowDays]

Loads of them here too

[A.J]

does anyone have anything to say  on topic?.......Ants, whilst fascinating creatures and helpful to mankind in numerous ways don't actually aid thunderstorm/convective  development  or discussion......lol

latest model runs now starting to roll out, hi-res NW due out in an hour or so, how will they handle what is now basically nowcasting?

[Flash bang flash bang etc]

I'm calling it a bust already 

[Ben Sainsbury]

Well isn't that a beautiful sky!

[Frosty hollows]

32 minutes ago, Mapantz said:

Flying ant day then? I had two of those last year, neither of which coincided with any thunder potential.

Spoilsport! I was getting more excited about the flying ants than than severe weather UKs thunderstorm forecast

http://www.severeweatheruk.com/thunderstorm-forecasts

[Supacell]

If Euro4 is correct then I will be a happy man. Unfortunately I am at work until around 4pm and so anything before that I will miss out on. I agree on seeing a storm at home has a different feel, but it's not something I have experienced for a very long time. Why would tomorrow be any different I ask?

I await the 12z suite of hi-res models with baited breath.

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Wed 05 Jul 2017 - 05:59 UTC Thu 06 Jul 2017

ISSUED 16:12 UTC Wed 05 Jul 2017

ISSUED BY: Dan

UPDATE 16:12 UTC SLGT shifted eastwards, in line with thoughts from this morning. Potential for upgrade to MDT over English Channel and adjacent coasts, but awaiting full 12z runs for any potential increase confidence. ECMWF and high-res AROME (which uses ECMWF boundary conditions) both consistently offer a much later development (i.e. after this forecast period) and only affect S/SE England on Thursday, which lowers confidence somewhat. 

UPDATE 07:44 UTC No modifications to the map for now, just to add some commentary based on 00z guidance. ECMWF continues to keep developments farther south and therefore elevated thunderstorms only reach far south coast at the very end of the forecast period (06 UTC). Most other output continue to hint at developments being farther north (and hence earlier / quicker motion to the NE), though broad trend would be to shift the SLGT farther east from its current position, roughly Dorset eastwards - this may be required on further updates.

... N WALES / N MIDLANDS / N ENGLAND / S SCOTLAND ...

Diurnal heating of a warm and relatively moist surface airmass will likely develop some marginal instability across these areas - though in reality, surface-based parcels likely capped by a warm nose around 850mb suggesting lightning rather unlikely given limited depth to any convection. Given also little signal from most NWP output (ignoring GFS with its dewpoints of 16-18C vs EURO4 with 11-13C), have refrained from issuing a LOW threat level for now - but will need monitoring. Some residual elevated instability may also produce the odd shower over the Midlands into East Anglia too.

... S ENGLAND / S MIDLANDS / HOME COUNTIES / S WALES ...

Upper trough west of Iberia will continue to disrupt southwards, backing the flow and allowing advection of high WBPT airmass from Biscay to occur into southern England on Wednesday night. Falling heights aloft will result in an increase in coverage of elevated thunderstorms, though the exact forecast evolution is marked with some uncertainty.

The vast majority of guidance suggests a few thunderstorms will develop over the English Channel and/or S/SW England 23 - 02z, expanding in coverage through the remainder of Wednesday night as the focus shifts northwards and eastwards over S Britain as the new warm front lifts north - hence in a broad sense, probabilities per given location increases as you head farther north and east across the SLGT area. However, the ECMWF has been fairly consistent in keeping the main upper forcing a little farther south, and hence any thunderstorms may only graze the extreme south coast towards the end of the night. At the same time, it also allows more activation of the frontal boundary towards Northern Ireland and western Scotland. Given the ECMWFs history of generally having a good handle (compared to many other models) on medium-level instability events, this casts a little doubt on how widespread thunderstorms may be over southern England - though the degree of instability and very steep mid-level lapse rates would suggests any thunderstorms that do occur would be prolific lightning producers, perhaps capable of producing some hail and gusty winds. A MDT may be issued should confidence improve.

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-05

[Rob Walker]

3 minutes ago, Summer Sun said:

Day 1 Convective Outlook

VALID 06:00 UTC Wed 05 Jul 2017 - 05:59 UTC Thu 06 Jul 2017

ISSUED 16:12 UTC Wed 05 Jul 2017

ISSUED BY: Dan

UPDATE 16:12 UTC SLGT shifted eastwards, in line with thoughts from this morning. Potential for upgrade to MDT over English Channel and adjacent coasts, but awaiting full 12z runs for any potential increase confidence. ECMWF and high-res AROME (which uses ECMWF boundary conditions) both consistently offer a much later development (i.e. after this forecast period) and only affect S/SE England on Thursday, which lowers confidence somewhat. 

UPDATE 07:44 UTC No modifications to the map for now, just to add some commentary based on 00z guidance. ECMWF continues to keep developments farther south and therefore elevated thunderstorms only reach far south coast at the very end of the forecast period (06 UTC). Most other output continue to hint at developments being farther north (and hence earlier / quicker motion to the NE), though broad trend would be to shift the SLGT farther east from its current position, roughly Dorset eastwards - this may be required on further updates.

... N WALES / N MIDLANDS / N ENGLAND / S SCOTLAND ...

Diurnal heating of a warm and relatively moist surface airmass will likely develop some marginal instability across these areas - though in reality, surface-based parcels likely capped by a warm nose around 850mb suggesting lightning rather unlikely given limited depth to any convection. Given also little signal from most NWP output (ignoring GFS with its dewpoints of 16-18C vs EURO4 with 11-13C), have refrained from issuing a LOW threat level for now - but will need monitoring. Some residual elevated instability may also produce the odd shower over the Midlands into East Anglia too.

... S ENGLAND / S MIDLANDS / HOME COUNTIES / S WALES ...

Upper trough west of Iberia will continue to disrupt southwards, backing the flow and allowing advection of high WBPT airmass from Biscay to occur into southern England on Wednesday night. Falling heights aloft will result in an increase in coverage of elevated thunderstorms, though the exact forecast evolution is marked with some uncertainty.

The vast majority of guidance suggests a few thunderstorms will develop over the English Channel and/or S/SW England 23 - 02z, expanding in coverage through the remainder of Wednesday night as the focus shifts northwards and eastwards over S Britain as the new warm front lifts north - hence in a broad sense, probabilities per given location increases as you head farther north and east across the SLGT area. However, the ECMWF has been fairly consistent in keeping the main upper forcing a little farther south, and hence any thunderstorms may only graze the extreme south coast towards the end of the night. At the same time, it also allows more activation of the frontal boundary towards Northern Ireland and western Scotland. Given the ECMWFs history of generally having a good handle (compared to many other models) on medium-level instability events, this casts a little doubt on how widespread thunderstorms may be over southern England - though the degree of instability and very steep mid-level lapse rates would suggests any thunderstorms that do occur would be prolific lightning producers, perhaps capable of producing some hail and gusty winds. A MDT may be issued should confidence improve.

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-05

Ooooh 
"The vast majority of guidance suggests a few thunderstorms will develop over the English Channel and/or S/SW England 23 - 02z, expanding in coverage through the remainder of Wednesday night."
I wasn't going to bother staying up later until I saw this... tempted now!

[MP-R]

Looking good here. Plenty of altocumulus grimsleyus.

[Ben Sainsbury]

Just now, MP-R said:

Looking good here. Plenty of altocumulus grimsleyus.

Ahahaha don't get me started!! Good signals of instability here!

[matt111]

Signs of something happening here.

[A.J]

Arome 12z 1.3km hi-res output is horrific for storm lovers west of London and south of Birmingham.....no elevated storms overnight (kent clipper only) and tomorrow afternoon midlands through northern/NE/E England only......nothing at all for the entire SW and southern counties (bar the extreme south east) hope it's wrong as it makes me want to cry

ARPEGE 12z much better for the west country and southern counties (it is a lower resolution model though)

the GFS12z run is more of the middle man

haven't seen any other 12z output as of yet

[Marcus_surfer]

All to play for. Southwest Uk looks set dry though so far. I think the main heavy activity will be east anglia, lincolnshire, yorkshire

[Thunderstruck]

On the edge of the SLGT. Last time Convective Weather was spot on...

[Justin123]

I believe that we may be experiencing storms for a solid 18 hours to 24 hours from around 2300z tonight, cirrus very present across southern Britain, an early indication of the instability to come.

[tomp456]

NW's will it thunder has been at 80% for the last 2-3 days.

on the latest run its gone down to only 62

Typical!

 

But I did get thunder two weeks ago when it was on 0% lol

[MattTarrant]

18 minutes ago, ajpoolshark said:

Arome 12z 1.3km hi-res output is horrific for storm lovers west of London and south of Birmingham.....no elevated storms overnight (kent clipper only) and tomorrow afternoon midlands through northern/NE/E England only......nothing at all for the entire SW and southern counties (bar the extreme south east) hope it's wrong as it makes me want to cry

ARPEGE 12z much better for the west country and southern counties (it is a lower resolution model though)

the GFS12z run is more of the middle man

haven't seen any other 12z output as of yet

ARPEGE is very good in a broad sense really, seems a battle is developing between the models. 

[AL.]

2 hours ago, slinky1989 said:

Thanks for that, just looked outside and it's antmageddon out there.

 

Not looking forward to leaving work now!

I'm in Swindon and haven't seen any?

[LightningLover]

Yaaay I'm in the SLGT zone!! (Also this was this mornings sky looking out to sea.

[MrNooo]

3 minutes ago, AL. said:

I'm in Swindon and haven't seen any?

None here thankfully but do have some lovely altocumulus Castellanus clouds rolling in, surely a good sign!

[The PIT]

Still just in the convergence zone however national forecast downplaying the storm risk tonight saying isolated storms. GFS showing plenty of shower activity tomorrow. Overall no real change looking at the GFS wonder why they are down playing now.

Just seen Summers post which explains it. So a dead duck for tomorrow which probably means good storms for us then. Funnily enough local forecast has a storm symbol for us.

Edited July 5, 2017 by The PIT