Storm & Convective Discussion 12z 21/7/14 ------>

[Flash bang flash bang etc]

Saw elevated flashes for a whole over in Sevenoaks but called it a day - now hoping for stuff to happen further west

[Supacell]

Although it is a messy picture today there are areas that interest me. Firstly I notice the CAPE levels indicated by GFS for this afternoon with around 700-1000j/kg being progged, this almost mirrored by the NMM although CAPE just slightly watered down on here for the same sort of time.

 

 

 

Lapse rates are up earlier in the afternoon with the highest lapse rates transferring northward through the afternoon and evening period. ELT's also looking favorable, these two things together would indicate a possibility of hail and frequent lightning as storms mature.

 

 

Although there is some deep layer shear it is probably not enough in itself to allow storm organisation but low level shear and speed shear is looking better. This creates some interest in the early to mid afternoon for the Midlands into Northern England as there appears to be a slight tornado risk should any storms organise. Shear does look to increase from the south later in the afternoon and evening but this may be too late for the highest storm risk area as it moves northward (although keep this in mind for later).

 

 

Clearly convective precipitation is not in short supply with the picture looking messy. This may actually prove to work against storm potential as we may just end up with a mass of heavy rain pushing north.

 

 

Another thing that has caught my eye is the NMM developing a small area of enhanced CAPE (upwards of 1000j/kg) around Gloucestershire mid-late afternoon and a subsequent thunderstorm developing and moving NE through the Midlands into the late afternoon and evening. It is a small risk but if this did happen then this will form in the aforementioned area of more favorable shear and could develop into a more organised storm cell for a time.

 

 

 

At this same time, looking at the wind charts, you can clearly see convergence over N England, this having pushed northward through the middle of the day and another area from the Gloucestershire to Midlands area.

 

 

Overall it is a very messy picture and a complicated forecast. I am probably out my depth here but putting things together this could become a day of plenty of cloud and plenty of rain with the odd rumble. Alternatively today could become another good day for storms. If storms do occur there looks to be two prime risks. The first is along a band that pushes north across the Midlands by midday and into Northern/Eastern England this afternoon. The second is a lesser but more interesting risk of more a more isolated storm pushing NE from somewhere just inland of the Bristol channel up through the Midlands.

 

Charts provided by netweather and www.lightningwizard.com/maps

Edited August 2, 2014 by Supacell

[sunnijim]

Crack of thunder overhead here in hither green just now!

[nanu]

Nice storm going on here,, nice crash of thunder, crapped the life out of me!!

Edited August 2, 2014 by nanu

[Biggin]

Bit o thunder just now.

[Cloud 10]

Cold front looking very active already on radar,with small trough ahead of it.

 

 

 

http://www.metoffice.gov.uk/weather/charts/FSXX00T_12.jpg

[BrickFielder]

 Tricky as supacell says.I think supacell has picked up on something with some post frontal troughing. Top level humidity charts for NMM are picking this up.

 

 

Looking at satellite pictures I have a feeling the troughing will be much closer to the back of the front.  The little bit of dry air aloft between bands of rain could enhance convection in the second band of rain although NMM is not that keen on it. Mid level humidity charts also show some development behind the front.

 

 

Mid level vorticity charts suggest better destabilisation of the frontal band as it moves out of the midlands.

 

I cannot help thinking that cloud cover is going to play a part in keeping temperatures down and think surface based instability is likely to be more enhanced with post frontal troughing.

 

Low level Wind shear looks best under the frontal band, but there is moderate deep layer shear.

Low level shear being enhanced a little by perhaps a convergence zone in the south west.

 

There is a fly in the ointment for post frontal storms and it comes in the form of the potential state of the top level of the atmosphere. Particularly temperature which will tend to limit cloud height.

 

Overall slight chance of a storm. Cloud cover generally limiting development  during the morning so north of the midlands generally favoured. Some postal frontal heavy showers possible with perhaps an isolated one being more severe.

[Mapantz]

The rain that has just fallen here was incredible! Third weekend in a row now, and the third time co-op has flooded out too.

[Nick F]

Storm & Convective Forecast

 

 

Issued 2014-08-02 10:12:31

Valid: 02/08/2014 1000z to 03/08/2014 0600z

 

THERE IS A RISK OF THUNDERSTORMS FORECAST

Synopsis

Slow-moving upper trough axis lying N-S across western side of the UK and down into Iberia continues to drive a cyclonic S to SWly flow across much of the UK, veering W to NWly across EIRE. At the surface, an area of low pressure over the Irish Sea will slowly drift N, to be centred over SW Scotland by 00z, associated warm lying SW from SE Scotland to Liverpool Bay will move N while cold front lying S to Dorset will moves ENE, the cold front clearing the E coast by 00z.

 

... ENGLAND, WALES and S SCOTLAND ...

 

Moist airmass will cover much of England and Wales today will become increasingly unstable though the day as falling temperatures aloft from the west and daytime heating create 400-800 j/kg CAPE. Large scale forcing from falling pressure/heights and lift from surface cold front moving through will support the development of thunderstorms, which may organise near cold/occluded fronts moving E, with more scattered t-storms also developing in the cooler flow following the fronts. More organised storms maybe capable of producing marginal large hail (1-2cm), strong wind gusts and torrential rainfall leading to localised flooding. Surface wind shift/backing winds ahead of frontal zone could allow rotation with more organised storms - so an isolated tornado can't be ruled out - particularly across E Midlands and E England.

 

Issued by: Nick Finnis

Edited August 2, 2014 by Nick F

[Spikecollie]

Looking good here in Limousin for this afternoon after yesterday evenings CuNbs flopped as soon as they got here. We got one enormous rumble of thunder and that was that, but they loped off over Creuse so there was some nice distant lightning.

 

The UK looks soggy and unpleasant...!

[TonyH]

Sferics breaking out over NW Devon 

Edited August 2, 2014 by TonyH

[gottolovethisweather]

Thunder heard due West of me, dark skies here for midday that is for sure.

[richep]

Not sure if the showers in Devon are going to go north of me but there has been lightning detected

[gottolovethisweather]

Rain rate of 99.4 mm per hour to boot since last report, no further Thunder detected but very sodden out there now and still raining. Expecting a good half an inch before this lot clears. 

Edited August 2, 2014 by gottolovethisweather

[TonyH]

A bit dark over Coventry:

http://bws.users.netlink.co.uk/webcam.htm

[Supacell]

Nice line of radar returns down the Welsh borders currently approx Liverpool to Gloucester, I have my eyes on that. 

[East_England_Stormchaser91]

Decent storm off the Lincolnshire coast. Suns out in borough, let's hope that lot in the midlands fires up on its way N/NE.

[gottolovethisweather]

Not that round one of those intense downpours has finished yet with over an inch falling but my eyes are drawn to proceedings over Salisbury now, will that lot follow the same path and provide round two, I wonder? Given the flooding seemingly likely in this area, I would hope not, but Mother Nature will do what Mother Nature wants anyhow. The garden birds and their young are soaked too, poor blighters.

Edited August 2, 2014 by gottolovethisweather

[Panayiotis]

Yep thunder every minute here, nice little surprise

Edited August 2, 2014 by Panayiotis

[Chris K]

Yep thunder every minute here, nice little surprise

 

Oh hello i came on just to see any chances over the next week and I see that heading my way... what a surprise if it keeps going!

[Somerset Squall]

Just heard some thunder in Taunton, looks pretty dark out there.

[William Grimsley]

A thunderstorm just rattled to the N of me with 3 rumbles of thunder heard. I might see something later now the wind is off the land instead of off the sea which stopped anything developing here.

[Supacell]

The storm in the North Sea is a bit of a beast but not likely to affect 99% of us. However, if you live on the far east side around the Humber it may be worth keeping a look out.

 

Another storm has developed in the Bristol Channel and surrounding land, this is of more interest as it is moving into the country rather than out of it. It has a long way to go to get anywhere near here though but good for those closer to it.

[TonyH]

New sferic near Aylesbury

[Raidan]

Just heard thunder hope it comes this way and doesn't stay in the Bristol channel.