Convective / Storm Risk Discussion - 23rd July 2013 onwards

[nitro_deluxe]

C'mon guys lol..my curtains swayed a bit just under an hour ago..hardly a convective report  

 

And i'm as desperate for a storm..flash..even distant rumble 

 

LOL.

[MrSunshine]

Just moderate rain here.

[tara303]

Well maybe a bust after all for Ireland - last x disappears from blitzortung and I'll be off to bed - there is a white blob just appeared below the other blobs on Meteox satellite which might expand like the previous one... just one more update lol!

 

My curtains moved too earlier - maybe the samosas though

[nitro_deluxe]

Curtains again..nitey nite all! lol..

[ZONE 51]

At the moment i would go for just the southeast getting any thundery weather on Saturday, The forecast wants to keep it all east. Time will tell over the next few days but looking at all the conditions on Saturday night i would, at the moment go for rain in the Home Counties, London, East Anglia thunder more confined to the southeast, but stress early days!!!!!

I can't see to much reason to hold the MCS /Thundery rain back from sticking only to the far east side UK. The track after it develops would be of course still unknown exactly as these storms can become bigger than expected. (or not grow at all)

Edited July 25, 2013 by ElectricSnowStorm

[ZONE 51]

Well maybe a bust after all for Ireland - last x disappears from blitzortung and I'll be off to bed - there is a white blob just appeared below the other blobs on Meteox satellite which might expand like the previous one... just one more update lol!

 

My curtains moved too earlier - maybe the samosas though

The thunderstorm over S-Ireland (as I posted sat and indicated earlier) it grew within a 15 min time zone, the recent storm action over the last few days have had this characteristic, it's single cells from showers home grown quite normal (although fast growing compared to usual 20-30mins)l but just saying that it's been noticable how fast the storms become active, how they have been on/off as they travel. 

Edited July 25, 2013 by ElectricSnowStorm

[Convective]

Estofex have this for us 

 

 

Storm Forecast
Valid: Thu 25 Jul 2013 06:00 to Fri 26 Jul 2013 06:00 UTC
Issued: Wed 24 Jul 2013 22:33
Forecaster: GATZEN

A level 2 was issued for south-western France mainly for severe wind gusts and large hail.

A level 1 was issued for western and central France mainly for severe wind gusts and excessive rain.

A level 1 was issued for Austria, the Czech Republic, Slovenia, and north-east Italy mainly for excessive precipitation.

A level 1 was issued for western Russia mainly for large hail and tornadoes.

A level 1 was issued for northern Algeria mainly for large hail.

SYNOPSIS

Low geopotential centred west of the British Isles will extend further south. Ahead of this trough, a deep south-westerly flow evolves across south-west Europe until the end of the period. Downstream development and warm air advection will result in another amplification of the central Mediterranean ridge that will also extend into central Europe. With south-westerly winds, warm air advection sets in across western and central Europe again, and a severe weather episode becomes likely. Over eastern Europe, low-level moisture advection is expected with northerly winds.

DISCUSSION

France

Ahead of the deepening Atlantic trough, increasing south-westerly winds will be associated with low-level warm air advection through-out the period. Steep lapse rates up to 600 hPa present over the Iberian plateau will spread north-east into southern and central France. In the boundary layer, rich moisture is still present as indicated by latest observations and the 12 UTC Bordeaux sounding, so that high CAPE values will likely result in response to diurnal heating.

Thermal low over Iberia due to strong heating ahead of the approaching cold front will enhance easterly low-level winds across north-east Spain and southern/central France with a pronounced convergence across south-west France along the sea-breeze. Moisture pooling will result in 0-500m low-level mixing ratio up to 14 g/kg, and models predict CAPE values in the order of 2-3 kJ. Further east, low-level moisture will be party mixed out. Initiation becomes likely over south-west France in the afternoon/evening due an approaching mid-level vort-max and associated decreasing temperatures above the boundary-layer.

Explosive storm development is expected. 15 m/s 0-3 km vertical wind shear and 200 m²/s² 0-3 km SRH will support supercells capable of producing large or even very large hail. Limiting factor is rather weak CAPE in the hail growth zone. Additionally, a tornado is not ruled out, especially along the sea-breeze convergence. Upscale growth into a convective system becomes likely in the evening hours given the favorable thermodynamic environment along a convergence line forming to the northeast. Bow echoes due to rapidly moving cold pools and storm mergers along the leading gust front will be capable of producing high winds. Excessive rain and high winds may also affect western central or even northern France during the night hours, before the storms weaken due to limited moisture.

Austria, Czech Republic, Slovenia, north-east Italy

Deep moisture indicated by latest Stuttgart sounding will continue to spread east into Austria. Thunderstorms will enter the eastern Alps and the Czech Republic during the morning hours. Widespread storms will continue to affect the region in the afternoon hours as well. Given the rich moisture and rather slow storm movement, locally excessive rain is forecast. Marginally severe hail and winds due to pulse storms or storm mergers are not ruled out although vertical wind shear is weak. The best potential seems to be present in the southern parts of the region, where strongest daytime heating is expected. Storms are forecast to decay in the evening hours quickly given increasing capping due to mid-level warm air advection.

Western Russia

Moist air has been advected to the west at the northern flank of the Russian trough. Another tongue of warm but rather well-mixed air follows from the east, and steep lapse rates can overlap with the moisture. Daytime heating will result in CAPE and thunderstorms are forecast. Given increasing vertical wind shear, storms may organize capable of producing large hail and tornadoes given favorable veering low-level winds. After sunset, convection is expected to decay.

Northern Algeria

Upslope flow of moist Mediterranean air and an elevated mixed layer will lead to strongly capped CAPE. Initiation becomed more likely in the evening hours due to an approaching vort-max that leads to a weaker capping inversion and increasing low-level convergence. Given strong vertical wind shear, storms that manage to develop over the Atlas mountains will have the potential of producing very large hail.

[ZONE 51]

Local report - Heavy downpours (as experiencing now and as seen on radar) moving across Surrey and into the London area now and through the next hour or two (few maybe)

I am in Stanwell (next to Heathrow ap)

Heavy rain now it's quite prolonged. Not any T/L and No lightning seen on radar image.

Edited July 25, 2013 by ElectricSnowStorm

[Biggin]

Yep moderate rain here , no rumbles.

[ZONE 51]

Severe downpour Stanwell now .. edit, slowed now was a very local more intense rain cell (few mins)

Edited July 25, 2013 by ElectricSnowStorm

[staplehurst]

I can't see to much reason to hold the MCS /Thundery rain back from sticking only to the far east side UK. The track after it develops would be of course still unknown exactly as these storms can become bigger than expected. (or not grow at all)

The main thing to note here is there will be a large mass of general frontal rain on the western flank of the plume (ie with no thunder). The thunderstorms themselves will be only on the eastern flank, and at the moment this only affects parts of Kent and Essex at best. Yes there will be some fairly widespread rain over East Anglia and the South East, but the bulk of it won't be thundery sadly...However this is MCS forms (ie if it does track further west) there will still be a large area of just plain rain on the western periphery where the frontal boundary lies. Edited July 25, 2013 by staplehurst

[stainesbloke]

Severe downpour Stanwell now .. edit, slowed now was a very local more intense rain cell (few mins)

Hi fellow Spelthornian! I woke up to sunny skies but everything wet outside here in Staines. Missed the rain but glad we had some after missing out on most of the action earlier this week.

[Norfolk Sheep]

The main thing to note here is there will be a large mass of general frontal rain on the western flank of the plume (ie with no thunder). The thunderstorms themselves will be only on the eastern flank, and at the moment this only affects parts of Kent and Essex at best. Yes there will be some fairly widespread rain over East Anglia and the South East, but the bulk of it won't be thundery sadly...However this is MCS forms (ie if it does track further west) there will still be a large area of just plain rain on the western periphery where the frontal boundary lies.

widespread rain is good

[Coast]

Estofex have this for us 

 

 

Storm Forecast

 

UKASF (morning Dan!) say:

 

 

 

Synopsis:

 

Upper trough will swing northeastwards across Britain around a large upper low anchored to the west of Ireland. Consequently, some cooling aloft will steepen lapse rates slightly, allowing a day of widespread convective showers. At the surface, a front will migrate northeastwards through the morning hours, becoming slow-moving across central/northern Scotland during the afternoon.

Discussion:

 

Behind the surface front, increasing amounts of insolation will allow near 900-1000 J/kg CAPE to build. Slight cooling aloft as an upper trough swings northeastwards will allow scattered showers and thunderstorms to develop, particularly across northern Britain, especially where orographic forcing and low-level convergence can be utilised. Some showers and isolated thunderstorms are possible across Wales/Midlands/East Anglia during the midday/early afternoon hours, but increasing weak ridging will cause the main focus for showers and thunderstorms to shift northwards with time.

 

Initially DLS is rather weak, but as a southerly jet migrates northeastwards across England and Wales, placing the left exit over NE England and S/SE Scotland during the late afternoon and evening hours, DLS will increase to 20-30kts and hence an increase in thunderstorm coverage is expected over these areas later in the day, with any showers/storms drifting northwards through the evening. In any stronger storms, hail up to 2.0cm in diameter is possible, else severe weather should be limited. Main concern is slow clearance of earlier frontal rain/cloud may inhibit insolation and surface temperatures somewhat.

 

 

[poseidon]

 Liking the look of Monday - MO have got lightning symbols for my area in the afternoon already - usually just have heavy rain symbols this far out.

[Coast]

GFS have today down for:

 

 

 

Tomorrow looks mainly confined to Scotland and Saturday:

 

Everything in England now slipping into France and the low countries:

 

[Kain]

Yesterday's time lapse from Bridgnorth filmed on the iPad for anyone interested

 

[Coast]

CAPE looks good down the East coast and in Ireland:

 

 

 

 

SBCAPE especially so in Scotland mid-afternoon:

 

 

Convergence all the way down the East coast of the UK down to East Anglia later:

 

 

 

 

Which looks like it could give us some convective showers:

 

 

 

I'd imagine Ireland and the top of Scotland in for a shout a bit later, possible something in the early evening in the top half of East Anglia, but as always, keep an eye on the radar!

Edited July 25, 2013 by Coast

[Cloud 10]

Had some heavy rain here earlier on this morning which has now cleared,and the sun is 

out and heating things nicely. 

[Coast]

[Nick F]

Risk of further scattered storms developing today and tomorrow across Ireland and the northern half of the UK. A moist and readily unstable airmass across northern and western areas. Cold front and left exit of jet moving NE across northern and western UK through the morning and afternoon will likely aid development of storms across northern England and Scotland. Post-frontal troughing likely trigger storms this afternoon across Eire with help of surface heating. General subsidence (NVA) on the right exit of the jet across southern Britain will generally hamper much in the way of convection. Slack post frontal flow across the UK tomorrow will again become unstable again across northern mainland UK and Eire with surface heating, with scattered showers/storms developing.

 

Then all eyes further south for later on Saturday and early Sunday, as another plume of very warm and moist air with high theta-w values advects north across France towards the UK on Saturday, upper trough and cold front moving in from the west looks to engage this plume over France and SE Britain Saturday night - allowing a thundery low to evolve as a wave develops and moves north along the western edge of the plume, with  widespread heavy rain and storms developing

 

 

Strong jet overspreads the W and NW edge of the plume in the vicinity of SE UK, so upradft/downdraft seperation and some 40-50 knts of DLS will likely allow storm organisation = perhaps supercells an eventually an MCS evolving with potential for severe weather

 

 

Some uncertainty this far out over the western extent of the plume engagement, GFS further west this morning, though most models suggesting heavy rain/storms across SE England/E Anglia at least for now. Though as we all know, an eastward shift could mean it becomes a Kent Klipper, or worse, missing the UK altogether.

Edited July 25, 2013 by Nick F

[tara303]

Big cauliflower clouds out to the west - when the sun is out, it's baking, making steam rise off the lane outside.

 

Could it kick off here today then anyone with the Knowledge, let me know...!

 

Been up since 6am when it was total fog/cloud cover up here on the mountain, has since cleared but clouding over from the west now...

[TEITS]

Somre more lightning shots from Monday nights storm.

 

 

 

 

[Robbie Garrett]

NMM going for a direct Southern England/South East England hit on Saturday night...

 

[BrickFielder]

Mid Level lapse rates are not that impressive again today, although slightly better in the north and east  (mid level lapse rates of 26C + best for storm development).  Low level convergence could again be a focus for development. Eastern coasts, parts of the north and areas in scotland.  Instability (Cape) looks moderate to very weak with northern areas where the mid level lapse rates are best. Surface based cape is the same except for a toungue down into the south west (Seems to aligned with surface convergence).  Perhaps the only surprise is the  possibility of some heavy showers developing in the south west.

 

As for Saturday then its a bit far out for guessing at the moment.