Uk General Convective Discussion & Forecasts, 13th March 2013 onwards

[Supacell]

Heavy showers breaking out outside of the SE now, although any sferics stuck to London like a magnet.

 

Some decent looking showers between Peterborough and the Wash, some across Manchester and a line of showers from Cheshire down to Wiltshire (although these don't seem to have any real beefiness about them currently). Also showers across the SW Midlands working east towards Northampton/Milton Keynes.

 

Will any of them turn thundery???

[Alex95]

Thunder in Keswick and a torrential hail shower again.

[Supacell]

I'm calling it.... bustola crapola! Oh well, its early in the season. Plenty of opportunities in the next 5 months i hope.

[lewisosd]

yep bust today. Overcast greys here. Convection is waning

[Cheshire Freeze]

Whatever happened to those Aprils that offered us more than a passing moderate shower? What happened to the days when a plume didn't just make it as far north as London then miraculously veer into Belgium and the N Sea? Whatever happened to the days when thunderstorms would afflict the west then push into the east during the evening, rather than just soley affecting the east?

 

All questions and no answers!

 

Our more seasonal winters seem to be at the expense of interesting summers!

Edited April 12, 2013 by CreweCold

[poseidon]

Sky just went very dark here, with low cloud. Then torrential hail followed by rain for around 10 mins.

[A.J]

Whatever happened to those Aprils that offered us more than a passing moderate shower? What happened to the days when a plume didn't just make it as far north as London then miraculously veer into Belgium and the N Sea? Whatever happened to the days when thunderstorms would afflict the west then push into the east during the evening, rather than just soley affecting the east?

 

All questions and no answers!

 

Our more seasonal winters seem to be at the expense of interesting summers!

gawds sake, stop moaning!......the answer is simple...you live in Crewe.....It is written in the ancient texts that even the Great Plague reached the town limits, saw the 'Welcome to Crewe' sign, and thought to itself..."Sod this, I'm not even staying in this dump long enough to infect even one person"......Given that, it's no wonder, Cb's give Crewe a wide berth!

[Cheshire Freeze]

gawds sake, stop moaning!......the answer is simple...you live in Crewe.....It is written in the ancient texts that even the Great Plague reached the town limits, saw the 'Welcome to Crewe' sign, and thought to itself..."Sod this, I'm not even staying in this dump long enough to infect even one person"......Given that, it's no wonder, Cb's give Crewe a wide berth!

 

It is a cess pit in all fairness

[A.J]

It is a cess pit in all fairness

why do you think I moved from Penkridge?.....holy smokes, the stench used to flow down the cheshire gap given a north westerly !

 

I jest of course.......

 

 

 

 

 

....It didn't matter what direction the wind was blowing!

 

 

 

 

Aaaaaaaanyhoos, Back on topic, and it looks like convection's on the wane now as we lose solar heating and as warmer T500's moves into the country from the south west/west

Edited April 12, 2013 by ajpoolshark

[dave48]

ESTOFEX called the 15% risk as opposed to the 50% which was spot on with the low coverage as it turned out so well done to them on that.

I was returning home on the train today from Wiltshire back to Kent and there were some fantastic Cbs all the way. Not my favourite convective day though, saw some nice structures but a lot of messy convection too which got in the way.

[lewisosd]

Whatever happened to the days when thunderstorms would afflict the west then push into the east during the evening, rather than just soley affecting the east?

 

 

 

 

 

The East had a relitively poor storm season last year. The Midlands and especially the North East got most of it last year

Edited April 12, 2013 by lewisosd

[Supacell]

 

You did catch the cell that went over Belper around an hour ago, didn't you?

Went very dark and there was heavy rain for about 10 minutes. It appears the cell spat out a couple of sferics but they were about 3 or 4 miles to the east so didn't see anything or hear anything. I think they were more over Ripley and so there is a hill between here and there, would have blocked my view lol.

Unfortunately it caught me out as it pulsed up and died within minutes, otherwise I would have got on it. Typical eh

Edited April 12, 2013 by Supacell

[Convective]

Don't tell me it's going to be another year for France........

[Cheshire Freeze]

Don't tell me it's going to be another year for France........

 

It's always the year for France.

 

If I don't get a storm soon my moaning is going to reach new heights. Sorry AJ

[Convective]

Would love to hop on a flight down to do some chasing down here.. the 18z, like weather09 said looks stunning. For some..

[Captain Shortwave]

Great Yarmouth is excellent for thunderstorms. Then I was forced to move here    

[Stuart]

no 1 posted this

 

Synopsis:

A very intense area of low pressure over the Atlantic will begin to spawn secondary lows, which will dumbbell around each other, while a weakening cold front will continue to track eastwards across Britain. In the post-frontal environment exists the potential for some convection.

 

Discussion:

... IRELAND, NORTHERN IRELAND, W/NW SCOTLAND ...

Cooling aloft coupled with diurnal heating will help generate a few hundred J/kg CAPE, allowing scattered showers to form. Despite steepening lapse rates, the depth of convection will be limited somewhat and only at its deepest during a short time window (3-4 hours), with ELTs potentially as low as -30C. As a result, lightning activity is expected to be quite isolated (if any).

The best convection is expected to be across Ireland during the late morning/early afternoon period associated with the passage of a shortwave trough coupled with cooling aloft. This zone of convective potential then migrates northeastwards into western Scotland during the remainder of the afternoon, whilst warming aloft will limit convective depth across Ireland from mid afternoon onwards. The net result is a quick reduction in coverage of convective showers during Sunday afternoon across Ireland, decaying across southern parts first and becoming largely dry towards Ulster by evening.

However, despite low potential for lightning activity (15-20% chance at any given location in the SLGT area) such convection is expected to be fairly well organised given a highly sheared environment (>60kts DLS). Backed surface winds and significant helicity increases the chance of a low-topped supercell, capable of producing hail up to 1.5cm in diameter and perhaps also a tornado.
This is a classic low CAPE high shear environment that can produce some locally severe weather. Given the strong mean flow, any cells that do form will rapidly move in a N/NNE direction.

Due to the low probability at any given location, the fast movement of cells and narrow window of potential, we refrain from issuing a SVR at this time, but will carefully monitor the situation during Sunday.

*** FIRST ISSUED AT 21:37, EDITED TO EXTEND SLGT ACROSS MUNSTER AT 08:00 ***

http://www.ukasf.co.uk/storm-forecasts/234

[Convective]

Estofex offering a level 1 for parts today! 

 

[MP-R]

This is the sort of setup which often brings thunderstorms in the summer period following a short humid spell with advancing cooler air from the west. Such happened on 21st June 2008 and 21st August 2010.

[VillagePlank]

A small chance of some T/storms in the SE tomorrow although most likely limited to the West and North of the region, say, in a line between IoW and E Anglia, these look like drifting east.

Convection may well initiate but forecast soundings suggest that uppers are not condusive enough to make the clouds sufficiently big. Certainly one or two hefty showers around and the presence of CAPE suggests some hail.

Overall chances: maybe 30% if you're in the right place at the right time.

Edited April 17, 2013 by Sparkicle

[Stuart]

Areas Affected:

 

S England, E Wales

 

 

Synopsis:

A deep, well developed area of low pressure to the north of Scotland will move eastwards into Scandinavia as cold air aloft floods around the northwestern periphery across much of Britain. An occluded front will wrap into Scotland during the afternoon with minor troughs rippling through the flow further south.

 

Discussion:

A northwesterly flow will allow for cold air advection aloft, thus steeping lapse rates. Various shortwaves/bands of PVA will move through the flow, combined with marginal amounts of CAPE that will develop towards midday and into the afternoon, at first across Wales and western parts of England, and eventually spreading further eastwards in the afternoon. 40C ELTs with 40-45 degree lapse rates from the SFC to 500mb will be enough for numerous "blustery" showers to develop even from early on across western Britain and Ireland, but as diurnal heating allows land temps to warm into the afternoon a few showers may be able to tap into 200-250j/kg of CAPE giving the potential for a few sferics with small hail. DLS will be greater across eastern Britain, suggesting that some showers may continue into the evening instead of quickly fading away after dark, however any sferic acticity will likely be during the mid to late afternoon. LLS will only be marginal (around 20kts) and combined with weak instablity any chance of funnels is rather limited.

 

http://ukasf.co.uk/storm-forecasts/235

Edited April 17, 2013 by Stuart

[Jane Louise]

 

Please note: only a slight risk! but it's better than nothing.

 

 

Slight Risk of Isolated Thunderstorms 10Z-19Z Thurs 18th April Wales, Central & Southern UK Regions

 

Filling low pressure NE of Scotland maintains cyclonic flow across UK through period. Long wave upper trough extends eastward increasing lapse rates and environmental lift. A number of weak surface trough expected to develop across SW regions by mid morning and transit eastward across the UK bringing blustery convective showers with small hail and possibly thunder.

A line from central Wales through to Humber looks quite active with GFS and WRF channeling the best instability. Initially potential instability looks to be somewhat hindered by a layer of heavy mid level moisture. Though this is soon replaced by a very dry incursion which should prop up a second round of vigorous convection (all be it relatively shallow). There looks to be limited moisture at surface with a broadening gap between surface temps and dew points. The end result might therefore favour more isolated and relatively high based storm activity. Winds look straight lined at all levels and lacking in surface convergence so the outcome doesn't look to be very organised. Though having said that there is scope for vertical speed shear so one or two storms may well become dominant for a time with the prime risk gusty winds with hail.The main non condusive factor at play for this outlook will sadly be the position of the rear left exit region of the jet stream which will act as a cap to any lifted parcel above 500mb.

 

Courtesy of UK weatherworld:

http://www.ukweatherworld.co.uk/forum/index.php?/topic/97707-convective-outlook-thurs-18th-april-2013/

 

 

 

 

 

 

[AWD]

Showers yes, but instability in the upper level tops doesn't look great enough for anything more IMO;

[VillagePlank]

England

In the range of the mid-level trough, steep lapse rates are expected. Weak CAPE is forecast and showers and thunderstorms are expected in the afternoon hours. Rather weak vertical wind shear will limit the chance of organized storms. Due to the strong pressure gradient, gusty winds are forecast, though.

http://www.estofex.org/

Edited April 18, 2013 by Sparkicle

[Andy Bown]

The first properly convective sky for a long time this lunchtime with CBs all round, heavy downpours including hail and plenty of sunshine in between.

People further to the East could have a fun afternoon as these showers move their way as the morning into early afternoon will have been quite sunny allowing for good solar heating.