Convective / Storm Discussion - 22nd October onwards 2013

[Robbie Garrett]

Just had a massive flash of IC lightning in London, anyone else see this or has something just detonated?

[Robbie Garrett]

Massive booming thunder. What is this?    Lightning flash as I type.

Edited December 19, 2013 by Robbie Garrett

[Chris W]

I am staying in Epsom tonight with a friend and saw two flashes of lightning with accompanying thunder - the first peal of thunder was very sharp and rapid following the flash.  I do believe that is the first time I have ever seen lightning in December.

[DAVID SNOW]

Just had a massive flash of IC lightning in London, anyone else see this or has something just detonated?

 

 T&L here too.

[Mokidugway]

Probably london heat island effect pepping things up, also been the odd flash in cumbria ,!!...

[max011293]

Thunderstorm just passed through here, with a few CG strikes and some hail for good measure

[ZONE 51]

Just had a massive flash of IC lightning in London, anyone else see this or has something just detonated?

Yep massive bolt of lightning lit up my flat (had low indoor light) boom of thunder at the same time as torrential rain and possibly hail. 

Edited December 19, 2013 by ElectricSnowStorm

[Evening thunder]

Interesting amount of lightning strikes detected with the showery activity for example in the Irish Sea and NW Scotland:

 

Edited December 21, 2013 by Evening thunder

[Liam J]

Very gusty winds and a few claps of thunder here.

 

 

[Lynxus]

Torro got a nice warning out:

 

TORNADO WATCH 2013/007 

A TORRO TORNADO WATCH has been issued at 10:10GMT on Saturday 21st December 2013 

Valid from/until: 10:10 - 22:00GMT on Saturday 21st December 2013 for the following regions 

Parts of (see map) 

TORNADO WATCH 

S Eire 

Wales 

IoM 

Much of England 

THREATS 

Tornadoes; wind gusts to 65mph; hail 10-15mm diamter; CG lightning 

DISCUSSION 

An unstable west-southwestely flow exists across much of the area now, although the south-eastern portion is currently being influeced by a waving frontal system. This feature will move away to the north-east early this afternoon. Following on, a marked trough/comma cloud feature will move in from the west, and appears to be the prime focus for any severe weather. 

Backed winds ahead of this second featured will enhance low-level vorticity/shear, whilst deep lifting will support an area of convection/thunderstorms. Deep layer shear will mean organised storms are possible, perhaps including supercells, although a cluster of activity, perhaps with a quasi-linear element, will be more likely. 

The current convective activity close to NW England should move away soon, with the trough then following through later morning and this afternoon/early evening. The main threat will be strong wind gusts, but a few tornadoes are possible too, especially close to the top end of the trough, where surface flow will be most backed. This looks to be from S Eire through Wales and into N England. However, the risk area has been extended south too, as some models depict convection further south. 

Forecaster: RPK.

 

https://scontent-b-ams.xx.fbcdn.net/hphotos-prn2/1476559_753540241342062_1888995339_n.jpg

[Lynxus]

Nice line here appearing. I suspect some hail in that. Probably quite gusty too.

 

[Convective]

Interesting amount of lightning strikes detected with the showery activity for example in the Irish Sea and NW Scotland:

Lightning 21st December.png Lightning 21st dec blitzortung.png

 

Woke up at 7:30 and went straight back to sleep. Typical.. that storm looks better than we get in the summer! Hopefully some more later!

 

TORRO warning looks good!

[Stuart]

2 warnings from sky warn

 

SKYWARN UK SEVERE THUNDERSTORM WARNING #047ISSUED: 1000UTC SATURDAY 21ST DECEMBER 2013

 

SKYWARN UK HAS ISSUED A WARNING FOR SEVERE THUNDERSTORM CONDITIONS AS FOLLOWS:DAMAGING AND POTENTIALLY DANGEROUS WIND GUSTS - WALES, IOM, NORTHERN ENGLAND, MIDLANDS, SOUTHERN SCOTLANDHEAVY RAIN LEADING TO A RISK OF LOCALISED FLOODING - WALES, IOM, NORTHERN ENGLAND, MIDLANDSPOTENTIALLY STRONG AND DAMAGING TORNADOES - WALES, NORTHERN ENGLAND, MIDLANDS

 

IN EFFECT UNTIL 2100UTC SATURDAY 21ST DECEMBER 2013

 

POST-FRONTAL SHORTWAVING AND A FURTHER WAVE/COMMA DEVELOPMENT, WITHIN AN UNSTABLE AND WINDY ENVIRONMENT

 

DISCUSSION:

THERE IS STRONG MODEL AND PARTNER AGENCY CONFIDENCE IN THE LIKELIHOOD OF SEVERE THUNDERSTORM RISKS TODAY. ONGOING ACTIVE CELLS IN THE IRISH SEA INTO NORTHERN ENGLAND ARE TESTAMENT TO ADVECTED WARMTH AND INSTABILITY BEING SUPPORTIVE OF STRONG CONVECTION. A WELL-SHEARED ENVIRONMENT AS THE UPPER JET PASSES IS PROVIDING SUFFICIENT FORCING TO SUSTAIN UPDRAFTS, FOCUSSED AROUND A POST-FRONTAL SHORTWAVE. STRONG GUSTS ENHANCEMENT IS LIKELY, WITH SPEEDS OF UP TO 60MPH EASILY POSSIBLE AND A SLIGHT POSSIBILITY OF BRIEF WEAK TORNADOES. INTENSE RAINFALL MAY ALSO PROVIDE A LOCALISED FLOODING RISK, THOUGH STORM MOTION IS EXPECTED TO BE FAIRLY SWIFT.

 

LATER THIS AFTERNOON, UNDER THE DIVERGENT ENTRANCE REGION OF THE PASSING UPPER JET BUT AHEAD OF A DEEPER DEVELOPING JET MAX, ADEQUATE FORCING WILL EXIST FOR SUSTAINED AND ORGANISED CONVECTION AND POTENTIAL SUPERCELL PHASES TO STRONGER UPDRAFTS GIVEN ENHANCED DIRECTIONAL SHEAR ON THE SOUTHERN SIDE OF A DEVELOPING WAVE. SEVERE AND POTENTIALLY DAMAGING WIND GUSTS ARE POSSIBLE, AS ARE SOMEWHAT STRONGER TORNADOES WHERE TOPOGRAPHY ALLOWS. HEAVY RAIN AND COPIOUS HAIL ARE ALSO POSSIBLE, LEADING TO EXCESS SURFACE WATER AND POSSIBLE FURTHER LOCALISED FLOODING GIVEN RECENT GROUND SATURATION. THIS WARNING MAY BE UPGRADED, PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY.

 

SPOTTER ACTIVATION IS REQUESTED AND SPOTTERS ARE REQUESTED TO REPORT ALL FACTORS EXCEEDING ACTIVATION CRITERIA

 

**** alerts contd below ****

 

SKYWARN UK SEVERE WEATHER WATCH #046

ISSUED: 1100UTC FRIDAY 20TH DECEMBER 2013

 

SKYWARN UK FORECASTS THE POTENTIAL FOR SEVERE WEATHER AS FOLLOWS:

STRONG, POTENTIALLY DAMAGING WINDS - SCOTLAND, NORTHERN IRELAND & IOM, NORTHERN ENGLAND, WALES, SOUTHWEST & SOUTHERN ENGLANDHEAVY RAIN LEADING TO A RISK OF LOCALISED FLOODING - WESTERN SCOTLAND, WALES, NORTHWEST AND SOUTHWEST ENGLANDBRIEF, WEAK TORNADOES - WESTERN SCOTLAND, NORTHERN IRELAND & IOM, NORTHWEST ENGLAND

 

IN EFFECT FROM 1200UTC FRIDAY 20TH UNTIL 0600UTC SUNDAY 22ND DECEMBER 2013

 

DEEP ICELANDIC LOW GENERATING GALES WITHIN AND BEHIND A BROAD ACTIVE FRONTAL ZONE, WITH FURTHER WAVE DEVELOPMENT THROUGH SATURDAY

DISCUSSION:

THERE IS GOOD MODEL AND PARTNER AGENCY CONFIDENCE IN THE POSSIBILITY OF A SEVERE WEATHER RISK THROUGH THE PERIOD. A BROAD AND DEEP ICELANDIC LOW SYSTEM CASTS A WIDE FRONTAL ZONE ACROSS THE UK, WITH GALE FORCE PRE-FRONTAL WINDS AND POTENTIALLY CONVECTIVELY ACTIVE COLD FRONT. A STRONG ONCOMING BRANCH OF THE JET PUSHES THE TRIPLE POINT OF THIS FRONTAL SYSTEM THROUGH SOUTHERN SCOTLAND AND NORTHERN ENGLAND. SOUTH OF THIS AND UNDER THE DIVERGENT RIGHT EXIT REGION, STRONG FORCING ARISING FROM SHORTWAVES WITHIN THE FLOW MAY ENCOURAGE CONVECTIVE ENHANCEMENT TO THE GUST STRENGTH AND A POSSIBILITY OF LEWP PHASES TO THE SPLIT COLD FRONT. NORTH OF THIS, THROUGH NORTHERN IRELAND AND SCOTLAND, INSTABILITY SHOULD BE DEEPER AND MORE COINCIDENTAL WITH THE COLD FRONT, LEADING TO STRONGER DOWNDRAFT GUST ENHANCEMENT AND THE POSSIBILITY OF TORNADIC ELEMENTS OCCURRING BRIEFLY. OVERALL, THE STRONG WIND ENHANCEMENT TO THE RAINFALL COULD SEE AROUND 40MM OF RAINFALL OVER HIGH GROUND AND COASTAL AREAS OF WESTERN SCOTLAND, WALES, NORTHWEST AND SOUTHWEST ENGLAND, PARTICULARLY SO IN THE SOUTH OWING TO THE LONGER PERIOD OF RAINFALL. HIGHEST GUSTS FROM THE REARWARD COLD FRONT ARE EXPECTED FROM NORTHWEST ENGLAND AND NORTH WALES AND NORTHWARD, THOUGH POSSIBILITIES OF STRONG GUSTS ON THE EASTERN SIDE OF NORTHERN ENGLAND AND SCOTLAND CANNOT BE IGNORED. NORTHWESTERN AND NORTHERN SCOTLAND WILL ALSO SEE PERSISTENT GALES AND STRONG GUSTS THROUGH THE PERIOD REMAINING AFTER THE PASSAGE OF TODAY'S FRONTAL SYSTEM.

 

SATURDAY ALSO SEES A FURTHER WAVE DEVELOPING WITHIN THE STRONG WIND FIELD, WITH CYCLOGENESIS POSSIBLY OCCURRING AS IT EMERGES ON THE LEFT SIDE OF THE JET. IF SO, ENHANCEMENTS TO THE FORCING AND DIRECTIONAL SHEAR WITHIN AN ALREADY UNSTABLE ENVIRONMENT MAY LEAD TO ORGANISED CONVECTION AND THE POSSIBILITY OF SEVERE GUSTS AND POSSIBLE TORNADOES THROUGH NORTHERN IRELAND, ISLE OF MAN, SOUTHERN SCOTLAND AND NORTHERN ENGLAND. THE MODELLING OF THIS FEATURE WILL BE WATCHED CLOSELY AND FURTHER UPDATES MAY BE ISSUED. PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY.

 

SPOTTER ACTIVATION IS REQUESTED AND SPOTTERS ARE REQUESTED TO REPORT ALL FACTORS EXCEEDING ACTIVATION CRITERIA.

 

http://www.skywarn.org.uk/current.html

[Gray-Wolf]

An unexpected boon for my Solstice sheenanigans !

 

We have the added bonus of 'rotor winds', rolling off the hills, getting stood on end as they drop into intersecting valleys ( hence our near common reports of 'mini tornadoes' ( hate that media phrase!) taking out groups of trees/sheds/greenhouses on stormy days).

[Panayiotis]

Line of heavy rain/hail earlier due to high vertical velocity, the animation shows the vertical velocity decreasing only for it to increase during the evening and more so overnight (where I suspect the greatest interest will be)

http://manunicast.seaes.manchester.ac.uk/view.php?t=20131221&d=d02&p=31&l=2

[A.J]

impressive line convection along the trough tracking across the Irish Sea, quite a few thunderstorms breaking out there

[Panayiotis]

impressive line convection along the trough tracking across the Irish Sea, quite a few thunderstorms breaking out there

Winter has more interest than the summer for t/storms!

[Nick F]

Storm & Convective Forecast

 

Issued 2013-12-21 15:05:55

Valid: 21/12/13 15z to 22/12/13 00z THERE IS A RISK OF SEVERE WEATHER FORECAST

Synopsis
Large and deep low pressure system to the NW of the UK will drive a strong cyclonic southwesterly flow across the UK. A frontal wave will slowly clear SE England, whilst a shortwave trough moves in from the west this afternoon and evening, bringing a risk of severe weather to parts of England and Wales.

... Sern IRELAND, WALES and ENGLAND ...

Satellite imagery shows a comma-convective cloud feature down the Irish/Celtic Sea containing some strong convective cells which are producing lightning over the sea. This convective squall is associated with pronounced shortwave trough which will continue to move east across England and Wales late afternoon and through the evening. The broken line segment convection within this system, aided by strong deep layer shear in the order of 60-70knts, will be capable of severe weather over a widespread area ... namely wind gusts of 60-70mph, hail to 10-20mm in diameter, CG lightning and torrential rainfall leading to flash flooding. Also, though a much more isolated risk, there is potential for one or two tornadoes - especially where winds back ahead of the approaching convective system. Therefore have issued a SLIGHT risk of severe weather over a widespread area including Sern Ireland, Wales and much of England.

[Mapantz]

Winter has more interest than the summer for t/storms!

 

I always do better in Winter when it comes to thunder & lightning. I had a storm on boxing day last year, the 27th saw lightning hit a school near here, which burnt the roof down. 

Edited December 21, 2013 by Mapantz

[Convective]

Can hear thunder rumbling away here. Huge squall too.

[The PIT]

Squall line looking good still on the radar. Sheffield shield will be powering up soon in panic mode.

[Liam J]

Absolutely hammering down here the roads are like rivers, bad travelling conditions! 

 

Edit: Fantastic lightening display now!!

Edited December 21, 2013 by Liam J

[Liam J]

Intense gusts coming through now with really torrential rain. Deffo a YIKES moment... Hailstones now!

Edited December 21, 2013 by Liam J

[East_England_Stormchaser91]

Is this really December !! Some folk look to be getting quite a deal more than they would ever do in the depths of summer. Remarkable, it has to be said!

[liamcymro]

Thunderstorms and torrential rain here!