[Nigel Bolton]

A finely balanced situation.

An elongated area of low pressure will spread rain northwards across England and Wales overnight. The low is expected to stall across southern England during Sunday, and bifurcate, with one centre remaining near west Wales, whilst a second centre runs away eastwards into Europe.

This will leave southern counties in a 'col', this containing plenty of moisture throughout the layers, and more to evaporate after the overnight rain. A well marked zone of convergence is expected to lie WNW-SSE across southern England, which may become the focus of some slow moving heavy downpours.

Models are indicating just modest CAPE and LI, but moisture would suggest, cloud efficiency will be high within a convective regime. Some thunder is possible.

Convection will depend very much on how much the cloud layers thin and break across southern areas. A grey day with low stratus will produce nothing. However if cloud does break, temperature will soon lift to initiate convection that will be forced by convergence. Well broken cloud may induce an augmented sea breeze, stronger convergence, a narrow line of intense rain, a risk of funnel clouds and a low risk of one or two weak tornadoes.

Areas at risk, Wilts, Berks, north Hants, Surrey, Sussex and Kent.

N.

[Lightningfox92]

Don't know if anything is possible today thunder wise here in Devon? Sky is elevated and looks thundery in nature

Didn't really seem worth having another thread for my question.

This post has been edited by Lightningfox92: 02 June 2012 - 14:00

[Howard Kirby]

Not quite Sunday...but recent Sferics just NE of Guernsey.

[Tony Gilbert]

Hi Nigel. Though low risk IMO well spotted. Started a basic Conv Out here http://www.ukweather...12/#entry804291

PS. If temps can spike up on some cells moving into the boundary the low level spin cud be quite phenomenal!
Not really mentioned the word funnel in the forecast but the potential is certainly there if the desired conditions can come together simultaneously!

This post has been edited by Tony Gilbert: 02 June 2012 - 21:18

[bensainsbury]

Any risk of a few heavy showers and storms in Bristol; a lot of cumulus bubbling up atm.

[Tony Gilbert]

bensainsbury, on 03 June 2012 - 09:49, said:

Any risk of a few heavy showers and storms in Bristol; a lot of cumulus bubbling up atm.

Surface obs currently show nearest convergence to you closer to Swindon region ATM. CAPE looks to remain rather lean based on limited surface warming today though still some potential for a few sharp showers under developing congestus clouds.

[Nigel Bolton]

One should keep a close eye on those showers. They are being steered by the 700hPa wind, this a southwesterly, and some of these are expected to cross the convergence zone, such that they will be undercut by an easterly.

As they cross the convergence zone, there will be a (short) period, where the low level helicity will be considerable, in the correct direction for separation from updraft from downdraft along with tornadogenesis. i.e. veering round from east to southwest in the lowest leyers of the cloud. Although relatively weak, they could for a time develop supercellular charactoristics.

This is not too dissimilar from the day that the Birmingham tornado developed, this being the 28th July 2005, when a thunderstorm in a SSW'ly airflow along a line of convergence, ran up a warm front, this overrunning a zone of cold easterlies.

Look for hard echoes on their southeastern flank.

N.

This post has been edited by Nigel Bolton: 03 June 2012 - 13:53

[Tony Gilbert]

Nigel Bolton, on 03 June 2012 - 13:51, said:

One should keep a close eye on those showers. They are being steered by the 700hPa wind, this a southwesterly, and some of these are expected to cross the convergence zone, such that they will be undercut by an easterly.

As they cross the convergence zone, there will be a (short) period, where the low level helicity will be considerable, in the correct direction for separation from updraft from downdraft along with tornadogenesis. i.e. veering round from east to southwest in the lowest leyers of the cloud. Although relatively weak, they could for a time develop supercellular charactoristics.

This is not too dissimilar from the day that the Birmingham tornado developed, this being the 28th July 2005, when a thunderstorm in a SSW'ly airflow along a line of convergence, ran up a warm front, this overrunning a zone of cold easterlies.

Look for hard echoes on their southeastern flank.

N.

Some sharpened radar returns already!

[Dave W]

bump

[Dave K]

Quite a clear line of it from North Wilts across to Surrey.

[Dave W]

Very heavy showery rain moving into London now from the SW and messing up the pageant..

[Nigel Bolton]

Nasty cell near Bristol about to abutt the convergence zone. Anyone in the area Bristol to Cirencester?

N.

[bensainsbury]

Nigel Bolton, on 03 June 2012 - 17:07, said:

Nasty cell near Bristol about to abutt the convergence zone. Anyone in the area Bristol to Cirencester?

N.

That cell has just passed overhead; didn't hear no thunder but torrential rain and hail. Doesn't have a good structure either.

This post has been edited by bensainsbury: 03 June 2012 - 17:12