Convective / Storm Risk Discussion - 23rd July 2013 onwards

[Team Jo]

Very Humid this morning, we pretty much had *something* going on from about 1am - 6am, and now it's just raining. Be interesting to see what unravels this afternoon.......

 

This was 4am

 

[jam2010]

Just wondering why the storms have just become boring rain.

[Supacell]

Morning all, feeling tired after last nights fireworks.Easily the most vicious storms seen in this area for +20 years.It just kept filling in from the south, without any logic, just lightning all over the place!I really hope anybody that missed out will get a storm.I think the East of the region is in for the French imports later.Local flooding is rife, saw a few cast iron drain covers pushed out of place, and it's still warm!

 

 i'm just glad I made the decision to go out and about. Belper got some action last night but nothing like the monsters over the eastern half.

[Emz by the Thames]

Short but sweet shower just before 4am - three loud booms in the middle distance and a few minutes of glorious rain.

 

I am just washing up at to my surprise I can see a tower cloud quite far away to the west of here - in south Oxfordshire perhaps.

[NOAJOA]

where is the party? I feel like ive missed out...

[I Cumbria Marra I]

We had very heavy rain for 3 minutes then 2 thunder which didn't even sound close and no lightning then spits of rain now and again, please tell me there's more to come? Sick of this s*** happening time and time again.

[Convective]

Here we go.. 

[john175]

good morning everyone , what a lovely wake up call ! ..pretty intense storm , lightning every 5 seconds 

[NUT]

Something is closing in on us I think. Might be interesting soon

[VillagePlank]

Here's my attempt at a forecast for 15z today from GooFuS 00z,

 

Warm and moist 18C plume starts to retreat south and east, this afternoon,

 

 

which consequently exaggerates lapse rates to the west of the retreating 18C theta-w area (air doesn't move homogenously all in one block, some layers move faster than others),

 

 

Initial thinking must be that those on the western side of the retreat under the more the significant lapse rates are therefore more at risk of thunderstorms. A quick glance at the skew-t's plays this out,

 

 

Which shows that whilst similarly convective, Manchester down to Cambridge develops more CAPE, and instability,

 

 

This isn't the whole story, however. A number of convergence zones set up. The primary one of interest must be the one running up the spine of the UK, but note the divergent zone in the channel (recall that if air is not moving parrallel to itself, it creates spin, and therefore lift),

 

 

Also, the mid-layer part of the plume will pretty much be gone by 18z creating a dewpoint depression exactly where you want it (approx 800hPa-500hPa),

 

 

Leading to more risk where the lower 850hPa theta-e temperature is significantly higher than the mid-layer 700hPa value. All in all, quite a complex scenario with different areas having different reasons for expecting thunderstorm development this afternoon. This shows quite well on the following charts,

 

 

Which, I think, illustrates the risk areas very well. Tip for the day: whilst the the far SE corner is not the most favourable place, retreating mid-layer theta-e + daytime surface heating, could start something.

 

Happy hunting,

 

Edited July 23, 2013 by Sparkicle

[MP-R]

Absolutely amazing thunderstorm here in North Somerset between 02.30 and 04.30. Very flashy with not much lightning definition but very bright flashes and loud booming thunder between the constant elevated roll of thunder. Despite the length, only 2mm of rain is in my guage this morning.

[Norfolk Sheep]

Same here, a shower about 23:00 last night, nothing since.  Looking at the radar everything is to the west and all of that is now just rain.

 

Can we make that triangle a quadrilateral ? 

Or a hexagon?   I suppose I ought to be grateful for the light rain really. It's beyond depressing though. If I hear any more comments in the next few months about "oh, the east always gets the storms" I will not be responsible for my actions.....

[Kain]

Been awake 27 hours now..

 

I think thats all folks for the west mids, but I'm happy!

[Mark Griffin]

Just distant thunder for us last night, mostly coming from the Manchester area so a bit disappointed but still plenty of chances today.

[Methuselah]

Or a hexagon?   I suppose I ought to be grateful for the light rain really. It's beyond depressing though. If I hear any more comments in the next few months about "oh, the east always gets the storms" I will not be responsible for my actions.....

The Polygon of Pish? 

[Ross B]

Jusr had a high based storm above the low cloud over Edinburgh.. so weird!

[Lynxus]

Such a shame. Missed out

 

A storm came pretty close ( sould see from distance ) but not much thunder and it soon passed to my west.

 

Hopefully we will get something else. Its tooooo hot and muggy now

[JamieUK]

Oh wow. FINALLY. After missing out on everything so far, looking at the radar i think we MIGHT just get a storm here in Aylesbury. I hope!!!!

[Emz by the Thames]

More cauliflowers than a greengrocers building in the Thames Valley, seemingly shifting north ...maybe north-east. Hazy to the south east. I hope it's going to be an interesting day!

Edited July 23, 2013 by Team Squirrel

[aggy]

Seriously kicking off in Ayr sw Scotland I'm feart lol

[joggs]

When the heat builds in the south home grown storms will develop so anybody looking at the radar thinking game over,give it a few hours.Good luck all

Edited July 23, 2013 by joggs

[Coast]

When the heat builds in the south home grown storms will develop so anybody looking at the radar thinking game over,give it a few hours.Good luck all

 

Activity in the Channel moving towards the coast:

 

[Tom Jarvis]

Still waiting for my good storm

[Boro Snow]

past 24 hours 24,115 lightning strikes across the uk, not bad eh

[Nick F]

Valid: 23/07/2013 0600z to 24/07/2013 0600z
Headline: ... THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FORECAST OVER PARTS OF THE UK ...

Synopsis
Upper low will be situated to the SW/W of Ireland during the forecast period, with a slack, warm, humid and increasingly cyclonic surface flow across the UK. One or two shortwave troughs are moving NE across the UK this morning, creating large scale ascent and widespread storms. A cold front is developing across SW England, Wales and NW England, which will move erratically E and NE, becoming slow moving across the east by 00z Weds.

... ENGLAND, E WALES and SCOTLAND ...

Large scale destabilisation of warm and very moist plume overnight (theta-w values of 18C+) has lead to widespread thunderstorms to drift N and NE across much of the UK since midnight, the large scale ascent attributed to an upper shortwave trough moving N and NE. S Scotland, N England, The Midlands and E Anglia will see further thunderstorms this morning and into the afternoon, these storms moving north across central and N Scotland this morning aswell, these areas will continue to see a risk of flash-flooding along with hail, gusty winds and frequent CG lightning.

In wake of these storms moving north, a warm and humid airmass remains in place across much of  England ahead of cold front developing further west. 00z soundings show rather steep lapse rates above 900mb still in place and with dew points of 17-19C forecast along with increasing amounts of strong insolation as overnight cloud detritus breaks, large amounts of CAPE, perhaps 1000 j/kg+ maybe realised, meaning the airmass will be increasingly unstable this afternoon. Sea breeze convergence inland from SE England through the Midlands and N England along with ascent along cold front moving erratically from the west will likely allow surface-based storms to develop by the afternoon across these areas. The strong instability and modest 20-30 knts of deep layer shear , maybe enough for one or two supercells to develop, or at least multicell structures,  capable of large hail, excessive rainfall, strong straight-line wind gusts and frequent CG lightning. With winds backed E or SE'erly towards the surface from the general S flow aloft - particularly near or just E of convergence zones, an isolated tornado can't be ruled out with strong updrafts in the high instability environment. Therefore have issued a SLIGHT risk, mainly for large hail, excessive rainfall with risk of flash flooding.

Issued by: Nick Finnis