Storm & Convective Discussion - 02/07/15 Onward - Heat & Plumes

[Karl83]

Music to my ears...

The 3KM NMM shows storms maturing around Bristol/West Midlands and then moving in to the East Midlands/Parts of East Anglia during Saturday morning.

 

You cut the power to the music!

Really? I see them dying out as they reach Bristol with major development over Ireland?

[dusk]

My take on tomorrow for the Midlands :-

 

<guesswork>Had lots of rain here this afternoon which has saturated the ground. A late sunny evening did nothing to evaporate the moisture, and has been on the cool side. Friday dawns sunny with a cool atmosphere, and starts to eke out the moisture from the ground, whilst during the afternoon hot and humid air from the South adds to the moisture, By late afternoon, a trough and frontal system trigger convection. Storms ensue.</guesswork>

 

This report has been brought to you courtesy of Appleton Estate rum with its partner, Coke Zero.

 

Please hold. Your call is important to us........ 

[Hathers]

Is this going to be the

most widespread thundery activity in the UK in recent years.

It could well be.

[Daniel*]

Tomorrow night:Southeast England high risk for supercell and tornadoes.

I like your style

[Wilxy]

I'll try typing this again and hopefully my phone won't crash on the fourth paragraph!

Was going to suggest u jump in the car tomorrow after work and head over near Reading with your camera(s) in tow.

Sit tight there and watch developments on radar.

Position yourself near an arterial route like the M4 - to give yourself easy travel option to the east or west.

Basically this will improve your odds of seeing what could potentially be an incredible night of storm activity.

Worst case scenario - it costs you a small amount in fuel and you see nothing.

Best case scenario - well you know the score... ;-)

 

This is exactly my plan as well because the nature of the direction the storms will generally suggest that the M4 will be a very good route to intercept storms moving north  

[Pigwhocouldfly]

Uh oh...did someone mention mini tornados.....?

All quiet here in Dereham. Been warm and sticky, but nowhere near as oppressive than yesterday. I'm watching with interest as you all decipher the charts and hope that those of you who mention East Anglia are right!

[Chris K]

Well out of this whole spell tomorrow night is probably the best chance for parts of the West, even if it does mean the models currently show us as more of the initiation zone as they push NE. Better than diddly squit! (if it verifies..)

 

MLCAPE looking great on the 3km NMM for much of the Southern half of England & parts of Wales as it pushes through.

Edited July 2, 2015 by Chris K

[Flash bang flash bang etc]

[Michelle Baker]

Trying to decide on best place to head to tomorrow. Seems it's too widespread to predict the best area to be in. I'm thinking south coast perhaps or would you say southwest like Minehead way?

[Karl83]

BBC have the storms over Wales. Obviously not to be taken literally but things are definitely looking better for the West!

 

Bring it on!

[Flash bang flash bang etc]

This is exactly my plan as well because the nature of the direction the storms will generally suggest that the M4 will be a very good route to intercept storms moving north

Is that sarcasm? :-)

Sorry i think I misread it!

Edited July 2, 2015 by Flash bang flash bang etc

[Trancemaster1966]

That supercell in the Netherlands appears to be weakening...only about 300 strikes p/m now :)

[Buckster]

18z out - looks shunted east to me ?

[Biggin]

Very little if nothing for the SE according to BBC just now, all to west n north Hope they are wrong as usual To those that do get something Enjoy.

[Mapantz]

18z out - looks shunted east to me ?

 

I don't see much of a difference out to T+39, the GFS is sticking to it's guns!

[Buckster]

ah - sorry - has GFS always shown S-East into the North Sea for the storms then ?

 

and more thundery rain for rest of uk ? - just seems to show little instability other than in S-East?

[Chris K]

ah - sorry - has GFS always shown S-East into the North Sea for the storms then ?

 

and more thundery rain for rest of uk ? - just seems to show little instability other than in S-East?

 

problem with the GFS is it is shown in 3 hour increments - hard to gauge at a short range where precipitation is most likely to be heaviest, what areas have the most instability each hour etc.

 

Plus for these storms we are probably more interested in MLCAPE rather then Surface CAPE, as they are likely to be elevated in nature. MLCAPE still looks good on the high res models for many parts.

Edited July 2, 2015 by Chris K

[Buckster]

ah ok - got you

 

seems tomorrow will be a wait and see event anyway really

[Mapantz]

Just as an example on the small differences, for midnight tomorrow..

 

12Z:

 

 

18Z:

 

[Nick F]

From what I can see on Wunderground and also the 'Home and Dry' app which both have ECM charts, unless I'm mistaken the ECM does break out precip/storms for most of the SE with only perhaps Kent and the far east of east Anglia so I thought it was a relatively positive run

 

12z ECM charts for 00z-06z Saturday, heaviest precip towards the NW, less towards the SE, though like you say, not immune.

 

 

Cold front engaging hot and moist plume returning W/NW from the near continent tomorrow evening, which in theory should create storms all along it across Ireland through the UK moving NE.

 

 

I guess some models break out heaviest precip towards the N and W of the UK, as this is where the greatest forcing for ascent will be in the left exit of the jet moving up the western side of the UK tomorrow night with capping more evident further east. But GFS suggests, and I would go along with it too, potential for storms all along the cold front.

 

Strong SW flow aloft and backed Ely winds ahead of the cold front should produce decent enough DL shear, 40-50 knts for well organised storms - line segments or even one or two supercells along/ahead the cold front capable of producing large hail and damaging winds. Strong enough veering for tornado potential too.

Edited July 2, 2015 by Nick F

[NO LONGER POSTING]

What I don't get.. Storms need juice, the only juice looks to be over the southern half into the Midlands...

Unless the GFS is being a div?

BTW the 18z is rolling out

[Staffordshire]

Have any sites released a forecast yet?

[Harry]

Convective Weather forecast out.

Interesting read, noting the huge caveats.

Day 2 Convective Outlook

VALID 06:00 UTC Fri 03 Jul 2015 - 05:59 UTC Sat 04 Jul 2015

ISSUED 21:54 UTC Thu 02 Jul 2015

ISSUED BY: Dan

... NW HIGHLANDS ...

Some wind convergence and upslope flow may develop a couple of locally heavy showers, perhaps a local flash of lightning in the mid/late afternoon.

... ENGLAND AND WALES ...

Rapid warm air advection will develop across southern Britain through the evening hours, causing surface dewpoints to increase as a warm front lifts northwards. Meanwhile, the Atlantic upper trough will pivot NEwards, overlapping with the arrival of this plume during the evening, and providing sufficient lift. Consequently, expect thunderstorms to develop through the evening hours, initially fairly well-scattered across SW England, with activity expanding farther N and E as the evening progresses.

With the approaching trough, DLS will strengthen with favourably-backed surface winds. This combined with 800-1,200 Jkg-1 MLCAPE suggests the potential for storms to become organised, perhaps into supercells capable of producing large hail. Forecast profiles suggest most storms will be elevated above 700mb, thus limiting the tornado risk, but if any storms do become rooted within the boundary layer, then there would be the risk of a tornado developing. There exists some uncertainty with developments farther east, namely across SE England and the Channel Isles.

Capping may be too strong or upper forcing not strong enough to generate storms here (as per consistent signals in EURO4/UKV/ECMWF) while GFS is more keen to develop storms over northern France and run them northwards into CS/SE England. Given these uncertainties have opted to go for the general consensus for now (hence reducing probabilities towards the SE, the MDT placed where best agreement exists amongst most models) but cater for the risk of large hail and heavy rain (given PWAT 35-40mm) as the primary threats with any strong storms that may develop in central and southern Britain. In either case, mass ascent will see storms become more numerous as instability axis moves north, merging into an area of thundery rain and eventually losing most lightning activity during the early hours of Saturday as instability weakens and clears eastwards to the North Sea.

It is likely that this forecast will need updating during Friday with threat level areas tweaked depending on convective trends.

[ancientsolar]

Well, ~ better buy some popcorn .. you may see some thunder and lightning in your microwave then .. unless you boil.. 

[Staffordshire]

What I don't get.. Storms need juice, the only juice looks to be over the southern half into the Midlands...

Unless the GFS is being a div?

BTW the 18z is rolling out

if they develop in an area of 'juice' they can persist into areas of no/little 'juice'

E.g storms pushing into, and continuing in the North Sea out of France/Benelux

However I understand these storms look to intensify in the north tomorrow, perhaps due to the Fax chart just posted showing a cold front straddling Northern UK?