Convective Weather UK

[Andy Bown]

TORRO have issued a warning for tomorrow: http://www.torro.org.uk/site/forecast.php

Looking at the BBC weather maps, a sharp line of more intense precipitation shows up from 9:00 - 15:00 crossing southern England, which seems to line up with the cold front showing on the Fax charts.

Yes that's going to be worth following, it could be quite an intense squall line with the wind suddenly changing direction

as it passes.

[Neilsouth]

Bit of a stretch, the forecast for line convection, severe convective wind gusts and tornadoes. Nothing really to suggest that sufficient convection will develop ahead of the cold front or INVOF triple point. However, the GFS does give subtle hints at the possibility of southern and south-eastern counties being better placed for anything that does happen to form, given better surface moisture, and perhaps also some drying of the mid-levels. But, again, it's a stretch. Despite the impressive shear environment, instability looks to be non-existent with the passage of the frontal system. Without sufficiently deep convective clouds, the shear has nothing to interact with.

http://www.metoffice.gov.uk/public/pws/invent/weathermap/

Run the radar for tomorrow , looks like an interesting line developing behind the rain !

[Coast]

This has been posted elsewhere, but worth repeating and pursuing in the morning:

TORRO CONVECTIVE DISCUSSION 2010/017

A TORRO CONVECTIVE DISCUSSION has been issued at 17:35GMT on Wednesday 10th November 2010

Valid from/until: 0000-2359GMT on Thursday 11th November 2010 for the following regions of the United Kingdom & Eire:

England Wales Scotland N Ireland Ireland

THREATS

Wind gusts to 65-75mph; tornadoes; occasional CG lightning; hail

SYNOPSIS

Rapidly deepening Atlantic storm will push an occluding frontal system across the British Isles overnight and through Wednesday. Instability along the occluded front and cold front is not predicted to be deep and very large; however, a forced line of shallow convection is possible across parts of Eire/N Ireland, and into Scotland/N England later tonight and for a time tomorrow morning. Strong ascent across northern parts of Ireland and N Ireland and into W Scotland could lead to somewhat deeper convection here, with a risk of thunder. Wind gusts of 50-65mph possible, along with isolated tornadoes.

Across Wales and central and southern parts of England, the cold front is forecast to split, with the surface cold front making somewhat slower eastwards progress than further north. Thus the risk of line convection is lower here. However, across S Wales and southern parts of England, as the upper trough extends SE'wards and a strong mid-level jet streak rounds the base of this, a wave may develop along the cold front in the SW approaches during the morning hours and then move eastwards across southern parts through the middle of the day and into the afternoon hours. Shallow convection may develop in a rather strongly-sheared environment. Broken convective lines are possible with rear-inflow, promoting severe wind gusts (55-65mph) along with a few tornadoes. A tornado watch may be required tomorrow morning for this.

Further north, behind the front heavy showers and few thunderstorms are expected, especially close to western coasts. Strong-severe wind gusts are likely with these.

Forecaster: RPK

[ZONE 51]

Yeah something interesting could develop very quickly across the south more likely se area, we could see severe gusts taking down trees in the line convection, very much a concern is how it would occur quickly, possibly small tornado causing damage. i would say if this happens then 60-70MPH CONVECTIVE GUSTS the first part of the day in s/se england and any tornado higher winds than this. then we have the rest of the day GALES. maybe thundery squally downpours causing SEVERE GUSTS.

(MY SE/S england forecast for thursday am-late pm) THE RISKS maybe up or down graded, later ,so keep updated.

[Coast]

To go with the above, UKASF have this one out:

Storm Forecast Issued: 2010-11-10 23:03:00

Valid: 2010-11-11 00:00:00 - 2010-11-11 23:59:00

Regions Affected

W Scotland, Northern Ireland (all of the United Kingdom is included in the WATCH)

Synopsis

Exceptionally deep extratropical Low pressure system "Carmen" will progressively move eastwards across Scotland during Thursday evening/night, which will dominate the weather across the United Kingdom.

A split cold front will cross southern England during daylight hours. Whilst the upper cold front will provide stratiform rainfall, the surface cold front looks likely to exhibit convective features, and whilst thunder/lightning might be isolated (or even non-existent), strong gusty winds, small hail and a tornado is possible along this convective line.

Behind the occlusion, numerous showers and isolated thunderstorms are forecast to develop in the rPm airmass across western Scotland and Northern Ireland.

During the evening hours, showers and isolated thunderstorms will become increasingly widespread over the North Sea as the occlusion continues to clear further east.

Hail is possible in some of the showers, mostly small but a chance of an isolated moderate event. There exists a risk of a tornado developing any these showers also. Showers will persist overnight in the aforementioned areas.

[Andy Bown]

Well the forecast line is clear on the radar but it's not very active!

[Joneseye]

Well the forecast line is clear on the radar but it's not very active!

It has just passed over Newbs and has started to pick up intensity. Not sure the rumbles I heard were from my belly or not

[Coast]

A few sferics sparking off in Ireland at the moment, going to keep an eye on that and see if we can get something closer to home.

[staplehurst]

Looks like some lightning occured with the convective activity along and ahead of the cold front towards the Hull region. Lightning would be more favourable here given better upper cold pool thus steeper lapse rates.

Much further south and the radar shows that particular convective line becoming slightly more defined as it crosses over Wiltshire, Berkshire and Hampshire currently. Whether this will lead to a severe convective gust event remains to be seen. In my view this would seem unlikely. But with enough ascent of one or two cells that can develop, this will bring the risk of transporting the much higher winds in the mid layers to the surface.

At the moment though, the more potent convection is taking place across Lincs and the Hull region, given better cold upper air over there.

Edit: What are the conditions like beneath that line of convection across London and surrounding regions?

Convective line (so to speak) passed through Norwich around 2pm. It was accompanied very torrential, driving rain, reducing visibility significantly and very strong, gusty winds.

[Andy Bown]

Well the forecast line is clear on the radar but it's not very active!

I was wrong as it turned out! More accurate was what I posted last night!

Much further south and the radar shows that particular convective line becoming slightly more defined as it crosses over

Wiltshire, Berkshire and Hampshire currently.

There were 2 distinct squall lines, one just before midday and the other around 14.30!

Both of which provided very heavy rain and squally gale force winds which were impressive to watch.

Looking at the NW radar zoomed in some of the rain rates approached 100mm per hour but, because they were moving so quickly,

just 5mm more fell from both lines and it rained for 10 minutes maximum between both lines!

[staplehurst]

I was wrong as it turned out! More accurate was what I posted last night!

There were 2 distinct squall lines, one just before midday and the other around 14.30!

Yeah we experience a second squall during the afternoon, can't remember the time of it though here in Norwich.

[The watcher]

Some interesting convective clouds trundling around here this evening as the sun sets. Have about 4 Anvils surrounding me and nice flat tops.

[Coast]

ESTOFEX concerned about activity off the Irish / SW English coast:

Storm Forecast

Valid: Tue 16 Nov 2010 06:00 to Wed 17 Nov 2010 06:00 UTC

Issued: Mon 15 Nov 2010 19:58

Forecaster: KOROSEC

A level 1 was issued for Ireland and areas towards extreme NW Iberia mainly for strong/severe wind gusts and brief tornadoes.

SYNOPSIS

Another feature of interest will be rapidly deepening surface low beneath the robust slowly negative tilting upper trough west of UK. Strong surface cyclone moves towards NE just west/near Ireland during the forecast period.

DISCUSSION

... Ireland ...

During the morning hours, rapid cyclogenesis takes place just west of Ireland and moves towards NE during the day. A strong cold front extends from its center towards SW and will be moving east towards UK, France and NW Iberia. With rather strong WAA ahead of the front and coming steep lapse rates aloft, some destabilization and convective cells/line is likely to occur along the surface frontal convergence. Mostly, strong to severe wind gusts will be the primary threat. Closer to the low, better veering profiles suggest enhanced SR helicity which could bring some organized rotating convective cells as well. A couple of funnel clouds or brief tornadoes cannot be excluded there either. Behind the front, strong CAA moves towards the continent with numerous shallow convective cells.

[Coast]

Looks like there might be a chance of an isolated storm developing tomorrow across southern England and Wales, but more in particular southern and southeastern counties of England from late morning.

I was prompted to have a look myself by BBC South East Today's Kaddy Lee-Preston who said something similar. Nothing from the usual websites but prior to a round-up in the morning (if necessary), here are the Lightning Wizard charts to think about:

It looks like a long shot, but if anywhere is going to get it, I should be in the firing line (just watch the IOW get the action! )

[Jane Louise]

I might get one too Coast lol :DOne can always hope I suppose!

[ZONE 51]

colourful charts their, i like it when they are put on..it gives that sense of thunderstorms..0:

Good luck on the coast should be some nice skys and afterdark lightning displays, just hope for something thundery or hail inland. (:

[Stormyking]

Wow last night was a shock about 1am i was about to go bed then my mate rang to tell me there was lightning going off everry few seconds or so and was hearing distant thunder and this was coming our way.

I went up to look for about 30 mins before i went to bed and saw 5/6 very bright flashes with 2 cgs then dies down so I thought I might as well go to bed so I did. As I was just dosing there was a huge crack of thunder outside which got me straight out to look. After that I went straight back to bed as I was so tired but yeh we had a thunderstorm last night

[Coast]

BBC local TV weather forecast still going for thunder later today, ESTOFEX, TORRO and UKASF have nothing for us currently. As discussed last night, it's a slim prospect but the SE corner on the coast, could be favoured if any:

12Z Herstmonceux sounding should tell us, I'm still going for the IOW to start off!

[Coast]

Today I'll go for the IOW at around 1430 - 1500hrs and Eastbourne by around 1530hrs........

[Stormyking]

Today I'll go for the IOW at around 1430 - 1500hrs and Eastbourne by around 1600hrs........

Well im at college now and just went threw torrential hail and extremely heavy rain and places are flooding again, last night came as a shock to me with the thunder and lightning as didnt expect it.

[Coast]

Nice big swathes of rain coming through, but no lightning showing up yet.... :unsure:

[Stormyking]

Nice big swathes of rain coming through, but no lightning showing up yet.... :unsure:

That big lot of showers some had hit the east side of the IOW but yeh no thunder or Lightning heard from them, may see a few strikes as it gets closer eastbourn or even kent.

I think they have the potential to produce those showers, the towers from thoughs showers I can see from here and look quite impressive

[Coast]

Not an exactly encouraging 12Z sounding out of Herstmonceux, scattered Tstorms at the very best:

[Costa Del Fal]

Just had some very heavy rain move through. Quite dark skies (no im not on about night lol).

[Andy Bown]

Good to have an interesting afternoon with some small but quite potent cells moving through between 14.30-16.00!

I have 5mm in my gauge and it didn't rain for more than 10 minutes in total in the several showers!