Convective / Storm Risk Discussion - 14th June 2013 onwards

[Bobby]

We haven't had any thunder but some torrential rain this morning, nearing 20mm in just 3 hours.

[Bobby]

This looks interesting from UKWW http://www.ukweatherworld.co.uk/forum/index.php?/topic/98359-convective-outlook-fri-14th-06z-sat-15th-june-2013/

 

Moderate Risk of Thundery Showers UK & Ireland Friday Through to Early Sat

Slight Risk of Tornado Development 00Z-06Z Sat Southern UK Regions

A transitional outlook though to save any confusion a cut off point is made at 06Z Sat.

Probably the most conducive severe weather outlook so far this spring. Some good parallels made by both WRF and GFS models; Unseasonably deep upper trough moves eastward enhancing environmental lift to both UK & Ireland. Strong moderately divergent jet stream arcs cyclonically enhancing strong dynamic lift within the front left exit region in line with the surface cold front. Strong PV (Positive Vorticity) aloft aligns well with the frontal boundary.

A number of phases of convection to deal with here; Early general thundery showers possible over central and NE UK today as some pre frontal troughing expected to develop. Later this afternoon Ireland sees a developing vigorous cold front bringing moderate or possibly stronger thunderstorms within the southern sector. Prime risk strong gusts and small hail. By mid night the cold front (possibly split) heads into UK mainland initiating further isolated thunderstorms with the additional risk of tornado development primarily southern counties 00Z-06Z Sat. Conditions associated with this risk include 45 deg veer at low levels with around 25kts 0-3km shear. Helicity values will therefore be sufficient for tornado development and sustained low level mesocyclones. The 500 mb jet is acutely divergent allowing for enhanced deep updrafts to form. Conditions are current borderline to supercell parameters. Reasoning for such development also lies with the depth and speed at which the upper trough transits eastward. The current overlay of cold pooling aloft might suggest large embedded hail reports overnight locally. Many parts will see sferic activity today though not prolific in nature. The prime interest here will be with well defined internal storm structure and mesocycone development. We will be working with lean CAPE values so the outlook is based on a high shear low instability scenario. So some caution needs to be addressed if the basic level of CAPE in not realised.

 

http://www.ukweatherworld.co.uk/forum/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=21880

Edited June 14, 2013 by Bobby

[Staffordshire]

Definitley going to be staying up tonight for any possibilities, i may have a bit ot a sleep around 10-12 then set my alarm to wake me up

[Lynxus]

Some sferics appearing near coventry. Looks liek some heavy showers around that area too!

[Harry]

Love it! Looks as though I'll be setting a 3am alarm, plus window open in case timing is wrong.

 

The MetO precip forecast makes for interesting viewing - showing a wave of intensification from 1am onwards...would appear on that basis alone, the further East you are the better.

Edited June 14, 2013 by Harry

[Coast]

OK, today has a bit of a way to go yet but some are already looking forward to overnight into tomorrow so what have we got?

 

Shear:

 

 

An area(s) of convergence:

 

 

 

The front moving across us:

 

 

and a chance of a tornado (if you can see it in the wee hours)

 

 

 

 

I may be in an induced coma at that time, but I'm sure some will still be up!

[Lynxus]

OOsh. some sferics to the SW of me!

[Coast]

Very little CAPE though as has already been mentioned:

 

[Arnie Pie]

Thunder in Brum !0 mins ago

[Lynxus]

Thunder in Brum !0 mins ago

 

Confirmed

http://images.blitzortung.org/Images/image_b_uk.png?t=22853550

 

[Coast]

NMM have monster deep layer sheer at 03Z!

 

 

 

 

 

 

[MP-R]

Looks like the Bristol area is the breeding ground for the cells further north. Nothing south of Bristol, cells firing up quickly just to the north. Glorious sunshine here in Yatton.

[Cheshire Freeze]

BBC weather not buying any potential for tonight. Latest video forecast- a spell of rain pushing across England and Wales, not particularly heavy.

[Coast]

BBC weather not buying any potential for tonight. Latest video forecast- a spell of rain pushing across England and Wales, not particularly heavy.

 

That's also at odds with GFS then:

 

[Cheshire Freeze]

That's also at odds with GFS then:

 

 

Don't shoot the messenger lol. There was hardly anything (other than a few spits and spots) shown on the graphics either.

 

Starts about 1.10 http://www.bbc.co.uk/weather/

Edited June 14, 2013 by CreweCold

[Coast]

Don't shoot the messenger lol. 

 

No worries CC! At this point neither of them is right or wrong!

[Cheshire Freeze]

No worries CC! At this point neither of them is right or wrong!

 

Given the data the Metoffice have access to, you'd have to go along with their notion at the moment. If owt pops up it'll be a bonus.

[Carl46Wrexham]

Nick Miller's take on the BBC forecast at 13.27 for tonight was "a weakening band of rain"

[Chris.R]

Well the met office text forecast for the UK tonight says this:

Tonight:

A band of persistent, occasionally heavy, rain will push east through the country during the evening and overnight period, with blustery showers following. It will be rather windy.

so they seem to be expecting more than just a dying band.

[Cloudwatcher]

Given the data the Metoffice have access to, you'd have to go along with their notion at the moment. If owt pops up it'll be a bonus.

 

Well the only certain thing CC is that we won't see any action lol! 

[PolarWarsaw]

Yep, Midlands today said predominantly dry over night, a few scattered showers in the early hours and then a bit of a rain moving away east in the morning. No mention of heavy rain, storms, a band of rain anything.

[SnowObsessor90]

Has anyone else here just had thunder?

[Cloudwatcher]

Has anyone else here just had thunder?

Nothing here but the v6 radar is showing a single sferic right over your location! Lucky git! 

[Nick F]

Storm & Convective Forecast - Issued 2013-06-14 14.00

 

Valid: 14/06/2013 1400z to 15/06/2013 0600zHeadline: ... THERE IS A SLIGHT RISK OF SEVERE STORMS FORECAST ...

Synopsis

 

Broad upper trough centred just west of the UK during the forecast will drive a strong SW’erly upper flow. At the surface, low pressure out in the Atlantic will shift NE towards NW Scotland, driving an active cold front east across the British Isles Friday night.

 

... EIRE, WALES AND MIDLANDS NORTHWARDS ...

 

Moist zonal flow, characterised by fairly steep lapse rates underneath cool mid-levels, is unstable across central and northern areas today, with frequent heavy showers and some scattered thunderstorms continuing into the afternoon across Eire, Wales, The Midlands and northern England. There is a risk of torrential downpours leading to localised flooding, CG lightning and hail.

 

... EIRE, ENGLAND AND WALES - EVENING/OVERNIGHT ...

 

An active cold front will move east across much of the British Isles overnight, bringing a small threat of embedded storms which may be capable of producing severe weather, though probability of severe weather will be low in any one place.

Left exit of a strong jet streak will move in across southern Britain tonight creating strong divergence aloft (uplift) working in tandem with the cold front moving east, to create strong forced ascent of Tm airmass ahead of front. Moisture will be greatest across southern England – where dry air is also forecast to overrun in the mid-levels, so there could be enough CAPE generated combined with forced ascent for thunderstorms along/near the cold front.  Strong winds veering with height will also mean any storms will form in an environment of strong deep layer shear ...  so convection is likely to organise into multicellular mode or possible bowing line segments with attendant risk of strong and perhaps damaging convective wind gusts along with hail. Winds backing ahead of CF before veering sharply with passage of front will also generate strong low-level shear., -  so an isolated tornado is not out the question, especially towards the southern counties of England where tongue of relatively warm/moist air is drawn up from the SW ahead of the CF. 

Issued by Nick Finnis

Edited June 14, 2013 by Nick F

[Cloudwatcher]

More sferics starting to show up in that little cell over Runcorn, Cheshire area. All quiet here, sun's just popped out for ten minutes though so who knows....