Convective / Storm Discussion - 8th September onwards 2013

[Guest William Grimsley]

GFS still keeping things to our South:

 

 

 

Maybe a bit of convergence along the Channel facing coasts will pep things up?

 

 

I hope so!

just having a first glance at the GFS12z output.....certainly is some mid-level energy and instability over the far south.....interesting!

I hope so!

[Flipflop]

Had my share this year of storms (need more) so i really can't complain-ish but i do like to see what people video or photograph so if you do get lucky in the next couple of days please post.....and i'll do the same as we all love a good visual of some kind whatever the quality..

Edited September 27, 2013 by Raptor Raw

[A.J]

off to bed shortly, but a quick post on the 18z NMM hi-res model......for the forecast period starting overnight friday into saturday afternoon...lots of mid-level energy with very bouyant air with high theta-e values associated with steep lapse rates and moderate mid-level capping acting as a 'pressure cooker'......As mentioned earlier a shortwave trough will move north-eastwards during the forecast period helping to destabilize the air aloft.......getting rather excited to be honest as elevated convection (i.e elevated thunderstorms) could form readily over the SW & CS England if these parameters verified..... (1000+j/kg MLCAPE with 4-layer indicies of -4 to -6, with lapse rates of 28C for the 850-500hpa boundaries and u to -100j/kg of CIN (mixed layer convective inhibition or capping)

[Coast]

Going with NMM, potential does look to be in the SW and possible central Southern areas:

 

 

No surface CAPE to speak of, but not unusual I guess with the strength of the sun as it is at this time of year:

 

 

 

 

GFS general overview still reluctant to build things as far North as the UK:

 

 

 

Lightning Wizard GFS also not as encouraging:

 

 

 

 

So has NMM got the Northerly element correct or will we all be left crying in our beer again as France cops the lot as GFS hints at?

 

 

 

 

 

 

[Supacell]

NMM are usually quite accurate and bbc does mention the odd rumble. I cannot see the charts but it may be worth checking the NAE for their thoughts and at this range the met office invent is a good source too.

[Guest William Grimsley]

off to bed shortly, but a quick post on the 18z NMM hi-res model......for the forecast period starting overnight friday into saturday afternoon...lots of mid-level energy with very bouyant air with high theta-e values associated with steep lapse rates and moderate mid-level capping acting as a 'pressure cooker'......As mentioned earlier a shortwave trough will move north-eastwards during the forecast period helping to destabilize the air aloft.......getting rather excited to be honest as elevated convection (i.e elevated thunderstorms) could form readily over the SW & CS England if these parameters verified..... (1000+j/kg MLCAPE with 4-layer indicies of -4 to -6, with lapse rates of 28C for the 850-500hpa boundaries and u to -100j/kg of CIN (mixed layer convective inhibition or capping)

Bring it on! The S Coast looks like being the best place to be!

Going with NMM, potential does look to be in the SW and possible central Southern areas:

 

ML CAPE 280913 12z.png

That looks great!

off to bed shortly, but a quick post on the 18z NMM hi-res model......for the forecast period starting overnight friday into saturday afternoon...lots of mid-level energy with very bouyant air with high theta-e values associated with steep lapse rates and moderate mid-level capping acting as a 'pressure cooker'......As mentioned earlier a shortwave trough will move north-eastwards during the forecast period helping to destabilize the air aloft.......getting rather excited to be honest as elevated convection (i.e elevated thunderstorms) could form readily over the SW & CS England if these parameters verified..... (1000+j/kg MLCAPE with 4-layer indicies of -4 to -6, with lapse rates of 28C for the 850-500hpa boundaries and u to -100j/kg of CIN (mixed layer convective inhibition or capping)

Bring it on! The S Coast looks like a good place to be, this weekend!

[Coast]

NMM are usually quite accurate and bbc does mention the odd rumble. I cannot see the charts but it may be worth checking the NAE for their thoughts and at this range the met office invent is a good source too.

 

OK, here's what they have:

 

 

The disturbance is a little further North across the SW and into Wales

 

 

MetO and the front midday tomorrow:

 

[Guest William Grimsley]

There is quite a high storm risk for the S coast of England, Sat 28/09 12:00.

 

UK storm risk. Valid: Sat 28/09 12:00.

 

[Supacell]

Thanks Coast. Its looking quite good for the south coast into more of SW England. Nothing for me but in all fairness i have had my share. Time for the SW to have a turn.

[Guest William Grimsley]

Thanks Coast. Its looking quite good for the south coast into more of SW England. Nothing for me but in all fairness i have had my share. Time for the SW to have a turn.

I think you are very kind. Thanks, Supacell.

[Mapantz]

Colder ELT's move in to the South overnight, so it may just be enough for some hail production. As somebody pointed out, elevated storms/lightning is a distinct possibility. As there's still a lot of disagreement across the models, even at this stage, i'll probably forget about them and simply see what unfolds on the radar.

Edited September 27, 2013 by Mapantz

[Guest William Grimsley]

Colder ELT's move in to the South overnight, so it may just be enough for some hail production. As somebody pointed out, elevated storms/lightning is a distinct possibility.

Yeah. Tomorrow, on the S coast of Devon/Dorset, there will be widespread showers/thundery showers. Sunday, on the S coast of Devon/Dorset, there will be a few showers/thundery showers.

 

As there's still a lot of disagreement across the models, even at this stage, i'll probably forget about them and simply see what unfolds on the radar. 

Good idea.

[A.J]

another good set of outputs from the NMM06z suite.....Parameters look good for elevated thunderstorms from the early hours of tomorrow morning and more especially middle of the day for the SW & CS Eng regions, more especially the west country, there's a good signal for elevated thunderstorms in these areas......surface CAPE is irrelevant as the instability is in the mid-levels......just got home from Worcester and already there are signs of some slight instability in the mid-levels as under a veil of high cirrus there is patchy altocumulus which is starting to tower into Ac Cas

Edited September 27, 2013 by ajpoolshark

[Chris K]

Aj, a rather selfish question if i may:

 

How far north would any developments likely reach if these signals were to verify? As far North as the Bristol/Gloucestershire/S Midlands areas? Or more staying down near the S coastal regions and perhaps parts of Dorset/Somerset/Wiltshire/Devon etc?

[A.J]

Aj, a rather selfish question if i may:

How far north would any developments likely reach if these signals were to verify? As far North as the Bristol/Gloucestershire/S Midlands areas? Or more staying down near the S coastal regions and perhaps parts of Dorset/Somerset/Wiltshire/Devon etc?

It all depends what model output you're looking at Chris....Personally I favour the NMM hi-res, and this model shows a good signal for elevated thunderstorms especially Stretching from Dorset and Wilts into BANES,and then into south Wales.....Other models will have a different handle on this....As as we know, thunderstorms are one of the most difficult weather phenomena to forecast especially from model output, so the best bet is to radar/sky watch tomorrow to see what happens

[jtay]

Aj, a rather selfish question if i may: How far north would any developments likely reach if these signals were to verify? As far North as the Bristol/Gloucestershire/S Midlands areas? Or more staying down near the S coastal regions and perhaps parts of Dorset/Somerset/Wiltshire/Devon etc?

We'll keep you posted re: what's happening down here Chris.

[Coast]

No forecast weather warnings from MetO for tomorrow:

 

http://www.metoffice.gov.uk/weather/uk/uk_forecast_warnings.html

 

They don't even have anything much in the way of rain forecast:

 

 

http://www.metoffice.gov.uk/weather/uk/uk_forecast_weather.html

 

ESTOFEX for today until tomorrow 6.00am shows:

 

Also during the night, elevated thunderstorm activity occurs over W/NW France and probably also over SW UK and parts of Ireland. Despite marginal hail and heavy rain, no severe risk is anticipated. Still, storm motions of 5 kt and high TPWs point to an isolated excessive rainfall risk especially over far NW France.

 

So anybody's guess still?

[Bobby]

NMM and the Met Office charts look interesting tomorrow, mainly for S and SW England. 50-100 miles further N would be nice please, will be rather annoying to miss out narrowly on storms again.

 

Met Office chart:

 

Edited September 27, 2013 by Bobby

[Chris K]

NMM and the Met Office charts look interesting tomorrow, mainly for S and SW England. 50-100 miles further N would be nice please, will be rather annoying to miss out narrowly on storms again.

Met Office chart:

rh9e.jpg

That is certainly more precipitation than what was being forecast last time I looked on the Met Office site yesterday evening...but like you said just a tad further north please! Edited September 27, 2013 by Chris K

[A.J]

just to add to earlier.....nice elevated convection here in Wiltshire, Ac Cas towers going up readily as lapse rates steepen from the south in conjunction with a decaying cold front straddling the region......SAT24 imagery shows things starting to develop over Biscay and the south west approaches....one to keep an eye on

[wimblettben]

Yes it is looking quite good now, I can see some slightly unstable mid-level clouds allready and am getting a bit excited.

 

There are obviously no severe weather risks out about these coming showers as it will be all elevated so not as dangerous.

[liambailey09]

Glad I chose to study in Portsmouth, might have to cycle down to the seafront if there are any interesting developments! 

[Andy Bown]

Yes it is looking quite good now, I can see some slightly unstable mid-level clouds allready and am getting a bit excited.

 

There are obviously no severe weather risks out about these coming showers as it will be all elevated so not as dangerous.

Elevated storms can still give torrential rain, large hail and frequent CG lightning!

[Guest William Grimsley]

just to add to earlier.....nice elevated convection here in Wiltshire, Ac Cas towers going up readily as lapse rates steepen from the south in conjunction with a decaying cold front straddling the region......SAT24 imagery shows things starting to develop over Biscay and the south west approaches....one to keep an eye on

Yes, saw some altocumulus castellanus clouds to the SW earlier, here!

Edited September 27, 2013 by William Grimsley

[paul m]

Glad I chose to study in Portsmouth, might have to cycle down to the seafront if there are any interesting developments! 

Keep an eye on your bike. There seems to be a lot of thefts going on down there. (Pompey born and bred)