Uk Convective General Discussion & Forecasts - April 2012 Onwards

[Jane Louise]

Nothing here yet.. hoping tomorrow may be the day ,

Anyhows, here is a forecast from TORRO which is something to keep an eye on.

TORRO CONVECTIVE DISCUSSION 2012/001

A TORRO CONVECTIVE DISCUSSION has been issued at 1200GMT on Tuesday 17th April 2012

Valid from/until: 1200 – 0800GMT on Tuesday 17th/Wednesday 18th April 2012 for the following regions of the United Kingdom & Eire:

Cent and S Eire

Wales

Midlands

E Anglia

S England

Channel Islands

THREATS

Isolated tornadoes; hail to 10mm; CG lightning; heavy rain; gusty winds

SYNOPSIS

Deep upper low and associated occluded surface low will move from west of Ireland to S Wales in this forecast period. An unstable rPm airmass will be in place across the area. Reasonable shear this afternoon (0-6km around 30 knots; 0-1km 15-20 knots) along with a slightly unstable atmosphere should allow some organisation of cells into short lines, and perhaps some brief rotation within the more robust updraughts. Hail up to 10mm diameter and wind gusts to 45-50mph are possible, along with a low risk of one or two brief tornadoes. CG lightning is also likely.

Overnight, the low will move towards Wales. A tightening gradient on its southern flank will increase the chance of some 50mph gusts across SW England, and the increasing low-level flow to the east along with some backing may cause the tornado risk to continue along and just inland from the south coast (dotted area). The remainder of the area is expected to see reduced instability, and with much reduced shear, any showers should be disorganised.

Forecaster: RPK.

http://www.ukweatherworld.co.uk/forum/index.php?/topic/90613-convective-outlook-tues-17th-april-2012/page__pid__797357#entry797357

[Costa Del Fal]

Not being rude fella, and I have alot of respect for you! But I think you need to be patient, last year you got some great night time stormslf I remember correctly? alot better than some of the other middlanders! It's only April and we have plenty of time yet!

Dont worry, im prepared to wait. The above was just some Banter with those who have already had about 5 storms in a few days when some have managed a measly shower or two. :lol:

[Lauren]

Where you looking Lauren?

That was earlier on my drive home. Poor grammar on my part!

[Costa Del Fal]

Quite a few Sferics in the Atlantic and Southern Ireland right now tied in with that low due to affect England and Wales tomorrow. Could those Sferics be a sign of things to come I wonder???

Edited April 17, 2012 by Blizzards

[Cheshire Freeze]

Interesting that the GFS (12z) modeled the low to centre over the Midlands, whereas the Met's global and mesoscale models continue to go for a SW/CS England option.

LCLs rather low tomorrow (400m or below) as the depth of the profile is saturated, with substantial low-level vorticity and ascent close to the low centre which, combined with steep mid-level lapse rates and lightly converged sfc winds, might contribute to funnel or weak tornado development. Also a hint at sufficient low-level verticla wind shear and CAPE overlap, but rather unconvincing in all for a severe conv. threat.

I personally think the Midlands solution is more a goer......but then again, what do I know lol! GFS been consistent in modelling of the track as far as I can remember.

The latest WRF high res has the low centre over the Midlands now too on its 12z run which is coming out on Meteociel now

Edited April 17, 2012 by CreweCold

[Joey.G]

Short timelapse of the cell that passed over Reading earlier here:

And a pic

[Paul]

Here comes the low pressure which should bring some fun and games through much of the rest of the week..

[dave48]

Another thundery week, quite a thundery April this is turning out to be, especially if as mentioned there is more to come at the end of the month.

Edited April 17, 2012 by dave48

[NO LONGER POSTING]

Here comes the low pressure which should bring some fun and games through much of the rest of the week..

cheeky

[Lynxus]

Another thundery week, quite a thundery April this is turning out to be, especially if as mentioned there is more to come at the end of the month.

Already had more thunder this year than in the last 2 years!

I hope this is a good sign. Gotta get a new laptop holder for the car and can then get on the road. Im hoping to get a nice amount of pics and vids this year + free data from work means plenty of data on the road!

Edited April 17, 2012 by Lynxus

[Lynxus]

Estofex's latest warning isnt too promising.. But then again, ive had a level2 over here before and its been clear!

[Raytheon]

Great Day! Those Reading shelf pics looked amazing! If the 00z doesn't jump ship this is the game plan for tomorrow. Am I on the money or do i need Mother Nature to read my map first? cheers

[Eskimo]

Lots of rain for quite a few tomorrow. NAE going for an average of 20mm.

[Marcus_surfer]

Some quite active showers moving in the last 20 minutes, very gusty winds then it goes calm then very heavy hailstones

[Andy Bown]

Guess where the centre of the LOW is!? Right over my BA12 area and the surrounding region as it drifts gradually East.

Awesome satellite and radar images from 06.00 this morning, the sky was clear overhead with very dark cloud to the S/SE as very heavy rain passed that way. However in the last hour the centre has filled with misty low Stratocumulus which may be picked up once there's a visible sat image available.

Net Weather 06.00 Radar

Net Weather 06.00 Radar zoomed to BA12, you can see the rainfall all around the LOW centre

Met Office 06.00 Satellite

Edited April 18, 2012 by Andy Bown

[DeepSnow]

Just had some heavy rain that turned into hail... will be interesting to see what today brings, I hope for my first storm of the spring but is that asking too much?

[NO LONGER POSTING]

Just had a rumble of thunder here lol!?

[Coast]

Morning all.

As I feared, ESTOFEX confirming the major convective activity as far as they are concerned is across the Channel today:

Storm Forecast

Valid: Wed 18 Apr 2012 06:00 to Thu 19 Apr 2012 06:00 UTC

Issued: Tue 17 Apr 2012 20:52

Forecaster: SCHLENCZEK

A level 2 was issued for W Turkey for severe wind gusts, excessive convective precipitation and tornadoes and to a lesser extent for large hail.

A level 1 surrounds the level 2 for severe wind gusts and tornadoes.

A level 1 was issued for W and NW France mainly for severe wind gusts and an isolated tornado.

SYNOPSIS

There are three well-defined cyclonic vortices over the European region which may be associated with deep moist convection on Wednesday: One low pressure system is initially centered over the Irish Sea and moves eastwards towards Benelux and Germany. The second low crosses the Baltics and eastern parts of Scandinavia and continues towards the Barents Sea. The third low is located over the Aegean Sea and moves rapidly northeastwards into the Black Sea region.Intense gradient winds within the boundary layer are expected over the eastern Mediterranean region and over western Europe.

DISCUSSION

...British Isles, France, Benelux, W Germany...

Near the center of the low pressure system, a strong gradient flow will persist through the day. Given some hundred J/kg of uncapped MUCAPE and EL temperature in order of -30°C, showers and thunderstorms are likely to occur in this area. Wind speeds in order of 20 - 25 m/s at 850 hPa and 0-3 km shear around 15 - 20 m/s are fairly enough for some organized multicellular lines and clusters which may produce isolated severe wind gusts. A tornado is not ruled out either as LL shear in order of 15 m/s is present and 0-3 km SRH is also enhanced. According to the GFS model, the tornado threat is maximized along the coastline of W and NW France. The peak activity is expected in the early afternoon as most of the CAPE is tied to the diurnal cycle.

It should be coming into the Channel straits by now:

Will Southern areas get some of it??

Fingers crossed!!!!

Hi-res charts for today:

A little bit more inland?

Interesting area over Wales later!

Lapse rates over London:

Plenty of rain

As the low comes into the Home Counties:

Helical activity confined to France???

An interesting day with some possibilities across the South depending on who and what you are looking at. Time to pull up a comfy chair and tune into your favourite radar site and wait for any action!!!!

[Stuart]

Slight

Areas Affected:

SLGT: Most of the United Kingdom, excluding W Isles, Borders, N Eng and N + W Wales. E Ireland also included.

Synopsis:

A vertically-stacked low becomes slow-moving, centred across the Midlands/CS England, and fills slowly. Main convective threats will be in areas where slack conditions persist, mainly to the north of the low over northern Britain, and within the centre of the low itself.

Discussion:Cold-mid levels will overspread the forecast areas (-30C at 500mb), and combined with increasing LSTs will steepen lapse rates and generate >500 J/kg CAPE locally. Widespread convective showers are expected to develop throughout the forecast period, and with ELTs forecast to be as low as -45C in places such convection is once again likely to reach a sufficient depth for lightning in stronger cells.

Most notable convection is likely across Scotland and eastern Ireland with a slacker flow and more in the way of cloud breaks, increasing insolation. A second 'zone' of deep convection will occur across the Midlands and southern England in particular, behind a wrap-around occlusion. However, it is quite possible that even along the occlusion itself there may be some embedded convective activity.

Shear is rather weak, although locally up to 30kts DLS is possible over Ireland and Scotland, so here convection is likely to become better organised and more longer-lived, forming into distinct bands in response to local topographical and orographical effects against the mean flow. Weak shear in the South will result in quite a messy 'rash' of convective showers, some thundery, but poorly-organised. That said, up to 35kts LLS may develop locally with an increased threat of a funnel or weak tornado developing, heightened more especially with local convergence effects where winds become slack for any period of time.

Hail is likely in many of the showers, especially in stronger cells where locally diameters could reach 1.5cm. However, cause for concern, especially in the southern-most region, is excessive cloudiness and saturated vertical profiles, associated with occlusion debris. This may inhibit convection depth and intensity somewhat.

http://www.ukasf.co.uk/storm-forecasts/153

[Nick F]

Storm & Convective Forecast - Issued 18/04/2012 07:00

Valid: 18/04/2012 09:00 - 19/04/2011 06:00

Headline: ... THERE IS A RISK OF THUNDERSTORMS FORECAST...

Synopsis

Upper and collocated surface low will drift E across southern Britian during Wednesday, with cool and unstable showery airmass across the UK.

S WALES, S ENGLAND, MIDLANDS, E ANGLIA, LINCS

GFS develops 300-400 j/kg SBCAPE across southern England, The Midlands and E Anglia by this afternoon - where greatest moisture flow will be in the circulation of the low moving E across southern areas ... therefore these areas can expect to see scattered heavy showers and thunderstorms develop. Peak of thunderstorm activity will once again be late morning and through the afternoon - when solar heating will be maximised. Storms will organise into bands near wrap around occlusion and tend to be slow-moving as steering winds fall light under the low circulation - so localised high rainfall totals may bring a risk of localised flooding where storms organise and linger. Also, storms maybe capable of producing hail to marble size in stronger updrafts along with gusty winds. With wind convergence towards the centre of the low circulation and local backing of winds, funnel clouds are possible and even weak tornado cannot be ruled out.

E IRELAND, SCOTLAND

Scattered heavy showers and a few isolated thundestorms are possible in the modestly unstable N to NE flow across these areas during the afternoon, with a risk of hail and gusty winds.

[Coast]

SkewT for Eastbourne looking OK ish for midday onwards:

[Coast]

Is that activity I can see out over Cherbourg and the Channel Islands????

http://www.viewsurf.com/vue-89-Cherbourg_Octeville_-_Port.html

http://www.netweathe...lightning;sess=

[Lynxus]

Hmm, The low is progged to track directly overhead of me

Currently looking food for North , West and South of here IMO. ( Albeit not much further north of here )

Little cape if needed.. Not sure how much its going to be of help however.

Should quiet down during the day with the risk moving eastwards as the day moves on.

The "green" areas I personally feel will be best suited for organised slow moving showers/storms.

Edited April 18, 2012 by Lynxus

[Nick F]

Is that activity I can see out over Cherbourg and the Channel Islands????

http://www.viewsurf....lle_-_Port.html

http://www.netweathe...lightning;sess=

Cherbourg reported 'Light rain and thunderstorm in vicinity' 09:30 BST:

METAR: LFRC 180830Z AUTO 19022G35KT 7000 -RA VCTS BKN014/// OVC024/// //////CB 08/07 Q0982

I suspect there were a few rumbles for the Channel Islands earlier too. NW France looking quite good for a few severe events this morning/early afternoon with fairly decent vertical and speed shear in place, could be a few tornadoes where surface winds back.

[A.J]

Already the atmosphere is responding to favourable conditions over some southern areas with some quite lively showers firing over Salisbury Plain, tapping into quite a bit of convective energy & considerable lift