Convective / Storm Chat And Discussion

[chrisbell-nottheweatherman]

Morning all, looking at the radar for the past few hours, the storms either missed me to the West or fizzled as they got here.

[Neilsouth]

HIGH RISK of Thunderstorms & a MODERATE RISK of Severe Thunderstorms & TORNADO WATCH - Saturday 7 May 2011

Strong WAA training has become firmly established as an elevated plume moved N from N Iberia & Biscay last night. In its wake a strong WAA process has continue with a strong vortex anchored to the West. Enhanced pressure differential between the West and East of the United Kingdom will lead to an increased pressure gradient and further strengthening of 9.5 to 10g/kg mixing within the moderate to high risk zones during the afternoon. A strong jet streak rounds the base of the vortex to the South and West of the United Kingdom spreading across the warm/moist plume aiding in 200-300m2/s2 helicity, 30-35 kts LLS and 40kts of DLS. The jet streak is likely to assist in strengthening this wind-shear profile across parts of the West Midlands, North Wales, Pennine areas and North West England running into part of Southern Scotland. As a result we are expecting a very active day of thunderstorms with a HIGH RISK 70%> being issued for these areas. MLCAPE in the order of 600-900j/kg is expected to be realised by surface heating and synoptic forcing. Due to the kinematic environment combined with numerous VORT MAX lobes and strong PVA coupled with increased surface convergence some strong or very strong multi-cells are likely with an attendant threat of supercell(s) capable of producing tornadoes, perhaps a strong tornado locally. An additional tornado watch has been issued with key focus around the HIGH and VERY HIGH RISK zones. A MODERATE RISK of Severe thunderstorms has been issued for these areas where frequent lightning, damaging wind gusts and large hail will all be possible in the strongest cells. Locally some storms have the potential to become very dangerous and the general public are advised to sky-watch today and be aware of the threats due to danger of lightning and the other attendant threats aforementioned. Elsewhere in the MODERATE and SLIGHT risk zones wind-shear is forecast lesser, but all the same a risk of severe storms will remain, albeit slightly lower in coverage. Again anywhere across South West/West Britain will be at threat of a tornado in any stronger cell under such volatile environmental conditions. It is a day to get chasing, but be careful - especially in the MODERATE and HIGH risk areas. Other threats include flash flooding. During the evening another convective systems is forecast to move up from the English Channel to affect Southern England between 18-21Z bringing a more elevated risk of thunderstorms, most prominent near area Weymouth to Brighton. This feature has the potential to develop into an MCS and will pose a more significant threat to Eastern parts of Britain as it moves N during Saturday Night into Sunday morning. The main threat will be excessive rainfall and flash flooding. The general agreement in the model spectrum is for the heaviest rainfall bias to be confined to areas around London/Reading moving N into East Anglia/East Midlands N into Pennines and North East England up into much of Scotland during Sunday. Again some embedded convection is likely, but lightning is not anticipated to be as frequent in nature with perhaps the exception of North East England early Sunday.

Just a reminder then, there is a HIGH RISK of thunderstorms today for much of N Wales and NW England and some parts of N England and the N Midlands. A MOD RISK of severe thunderstorms has been issued too. An attendant tornado watch will be issued in a moment or so. Please take extra care today. Enjoy the storms!

Bumped from a few days ago below as additional analysis:

Risk of Tornadoes and Stronger Thunderstorms on Saturday

************************************************

Saturday is being monitored and the first in the start of the potential of severe thunderstorms. The general thunderstorm threat will likely increase quite significantly at this stage with the kinematic environment also strengthening. Latest GFS06Z guidance as of 5 May 2011 shows strong WAA being transported Northwards from the South as a strengthening vortex to the SW/W edges closer to the Western shore. To the East of the United Kingdom high pressure remains assertive and the squeezing effect of the vortex to the West will likely strengthen the pressure gradient. Due to the synoptic positioning of high and low pressure this only enhances warm air advection processes, leading to increasing moisture loading and as a result greater potential instability. 06Z output runs a jet around the base of the vortex from N Iberia into Western and Northern parts of Britain during Saturday. The combination of lowering heights at 500mb and increasing moisture/heat advection will only aid in steepening mid-level lapse rates and CAPE in the order of 500-800j/kg should be realised. Lower level moisture advection and LCL(s) 800M< will favour tornadogenisis and some storms could route to the boundary layer. A jet streak in the order of LLJ 72kts will aid in increasing multi-level windshear and it appears that ingredients are coming together for the potential of some stronger multi-cell thunderstorms, perhaps more organised in nature. The main threat at this early stage will be across Wales, The Midlands, running into Derbyshire and the Peak District and perhaps becoming more widespread across Northern England running into the North East. The main threat will be widespread thunderstorms with an attendant threat of a few stronger severe cells capable of producing tornadoes and large hail. Downpours, flash flooding and gusty winds also becoming a problem. This development does need close monitoring. Also worth mentioning will be the cloud equilibrium projections below -50, very favourable for very active lightning within the cells. Should model guidance continue to stengthen for Saturday a HIGH risk of thunderstorms would appear likely with perhaps a moderate risk of Severe storms for some. A tornado watch is anticipated for the weekend. An offical warning and update will be issued closer to the time-frame.

TORNADO WATCH - Western Britain - Sat 7 May 2011

A Tornado Watch is in affect for much of Western Britain during Saturday.  A mixture of elevated and routed convective will become established, but regions where sunshine can break through and aid insulation will be at risk of increasingly routed storms.  Those that do route to the boundary layer will be capable of tornadogenisis.  Latest guidance suggests a fairly capped environment through the morning hours until 12Z so most convection will be elevated in nature during this period.  However from 12Z-15Z the CAP weakens as the vortex moves against an increasingly warm plume.  Any heating will be maximised initially across Wales and the South Midlands, eventually firing across much of the Midlands.  LCL(s) in the region of 800M< will be evident further W, thus storms around Birmingham and immediately to the SW, W and NW especially could become tornadic in nature.  Towards late afternoon and evening the CAP weakens to the N across North West England as storms become more prevalent here.  Strongest theta-ew overlap +50 occurs across N Wales and the Midlands 15Z-17Z with strengthened SFC convergence towards the N Staffordshire/Derbyshire and Pennine area during this time.  Enhanced surface convergence in hillier terrain and across this area could enhance the localised possibility of a tornado.  Due to topographical features being elevated in the pennines an additional threat of large hail maybe possible. Tornadoes will be likely today across parts of the Worcestershire/Wales area as initiation early in the afternoon before becoming more widespread during the afternoon to affect all of the W/N Midlands/N Wales and NW England and again the Pennine/Derbyshire area.  A SLIGHT/MODERATE risk of tornadoes has been issued here due to the favourable environmental conditions, perhaps the risk of a MODERATE strength tornado.  Elsewhere to the South West and across the West Country much of the convection will be predominately elevated sufficiently enough to preclude a greater risk, although a funnel or weak tornado is still possible - especially across the Bristol channel/Somerset/Devon and running into Gloucestershire.

TC on TWO

[Paul]

Another heads up - USA chasers enjoying some cracking night time lightning chasing on the stream now:

http://bit.ly/cElYhg

[Neilsouth]

http://91.121.84.31/modeles/wrfnmm/nmm-1-24-1.png?07-07

http://91.121.84.31/modeles/wrfnmm/nmm-1-25-1.png?07-07

http://91.121.84.31/modeles/wrfnmm/nmm-1-26-1.png?07-07

Might be a mcs moving into the south east but as usual NAE say's no, nowcast folks

[gottolovethisweather]

Good, in depth forecasts from Brickfielder and others in the forecast thread for those wanting extra info on the storm risks today:

http://forum.netweat...ost__p__2073932

Cheers to whole team at Netweather, some amazing details there, much of which goes over my head but the dedication that some folk put into this website is simply beyond belief.

Go have a quick guys n gals.

Thundery Regards

gottolovethisweather

PS! to my untrained eye the clear skies at least IMBY and the associated daytime heating should almost certainly produce SOMETHING VIOLENT out there today.

[Backtrack]

Another heads up - USA chasers enjoying some cracking night time lightning chasing on the stream now:

http://bit.ly/cElYhg

That stream is very laggy for me. Is it my laptop or is it the same for everyone else?

[Karen Ann]

So near yet so far. I sat and watched distant flashes from several storms last night from about 6.30pm through to 1.30am. They just seemed to skirt past me, a little too far to the east. I heard very few distant rumbles though despite the intensity and frequency of the lightning. Guess I was just that little bit too far away. An active night if ever I've seen one.

Roll on this evening, perhaps it will be my turn. Certainly humid enough out there. Dilema - do I give the dog a sedative tonight in his tea or not? I didn't last night which was a good call on my part (didn't have my thunder headache so took a guess that things would miss me).

Fingers crossed for everyone again this evening.

[Alex95]

Gosh its muggy outside! I thought there was going to be an onshore breeze today! NAE wants to bring thunderstorms in NE England this afternoon, whereas the GFS says NW England.

[Flipflop]

That stream is very laggy for me. Is it my laptop or is it the same for everyone else?

Same for me also..

[Paul]

Live stream will lag sometimes - they're running off mobile connections in the middle of nowhere so the signal is sometimes not great despite the gadgets they have in place to boost it!

[Alex95]

That stream is very laggy for me. Is it my laptop or is it the same for everyone else?

Its a bit laggy, but only every 30 seconds. Its not much fun though at that resolution as the lighting is just little flashes on the horizon.

[NL]

Gosh its muggy outside! I thought there was going to be an onshore breeze today! NAE wants to bring thunderstorms in NE England this afternoon, whereas the GFS says NW England.

Not muggy here on the coast with a stiff breeze coming off the sea infact the wind is quite chilly, cant see anything happening here anytime soon, need the surface wind to change direction, at least theres no low mist/cloud coming in..!!

[sendandreturn]

Hello all, just got back from sitting on the beach watching the storm come in from the channel - amazing lightning show finished off with a healthy dose of large rain drops and cracking thunder. What a night especially as we thought we might be just that bit too far east!!

Last night we lost our power in wickham, so we went to in laws in dorset, thinking i'd be too far east too, really jealous this morning, would have LOVE to have seen...its such a vantage point , seeing them either off portsdown hill, or from the sea...

[weatherobsuk]

Convection initiating over the Channel south of Exeter where the clear slot currently is moving in. Trigger temp I believe is around 20-22'c for surface based convection here in the North so I'll be looking at the temp gauges in around 3 hours from now.

[philglossop]

The sun is trying hard to come out- this could bode well.

[Alex95]

Not muggy here on the coast with a stiff breeze coming off the sea infact the wind is quite chilly, cant see anything happening here anytime soon, need the surface wind to change direction, at least theres no low mist/cloud coming in..!!

Those 8 miles from the coast really make a difference here!

[Carl46Wrexham]

Even if you miss the storms your area should see very heavy rain later tonight into tomorrow morning.

I still believe the areas that will miss out are Wales, W/SW England, Norfolk, Essex, Suffolk,Kent. The reason being is the models continue to suggest central areas will be hit the hardest. When this area of storms hits the S im thinking around the Hampshire, W Sussex, Surrey area before moving directly N.

Not what I wanted to hear after missing out last night.

When a Spanish Plume fails to deliver its time to start thinking of being stuck in the no storms club for a while yet.

[Kain]

Just took up Pauls offer on the net weather radar. Pretty nice discount for those who are unsure!

[NL]

Those 8 miles from the coast really make a difference here!

They certainly do Alza..!! Might have to jump on the metro (me motorbike is off the road ) to catch any warmth nevermind any storm activity...

♫ Oh I do hate to be beside the seaside..Oh I do hate to be beside the sea..♫...:lol:

[sparky1972]

only 16c here this morning no sign of any sunshine to pick the temps up enough to trigger anything here i think. light rain at the mo.

[conor123]

Just light rain here in Telford at the mo, still havent had an overhead storm since 28th July 2008 or was it 19th July 2007?

[95 Degrees]

current temperature a humid 18.4C, hopefully the storms will be a tad further east today for those who missed out.

[Kain]

Slowly getting brighter here now, but raining lightly, showing signs of actually stopping. starting to feel close too.

[Jane Louise]

Hi all,

If you look on the webcam in my sig, the cloud is breaking away beautifuly

Certainly bodes well for later.

[chrisbell-nottheweatherman]

only 16c here this morning no sign of any sunshine to pick the temps up enough to trigger anything here i think. light rain at the mo.

Odd really, I'm not that far from you as the crow flies, and it's sunny here, albeit with some cloud floating around.