Convective / Storm Risk Discussion - 23rd July 2013 onwards

[Coast]

A new thread for a new day of potential, have you got convective storms or weather or do you think you might be in for some? Here's the place to discuss it!

The old thread is here:

 

http://forum.netweather.tv/topic/77329-convective-storm-risk-discussion-22nd-july-2013-onwards/

[Cheese Rice]

Crazy lightning storm here, constant thunder and lightning!

[Sainsbo]

It's already the wettest day of the year here with 23.4mm of rain in the last hour from the cells that have passed over. I can see surface water flooding being a serious issue in some places soon.

[WillinGlossop]

Perfect view to my north as 300 metres up on a hill so making another coffee and awaiting round two from the south..... Was pretty intense and tropical style thunderstorm here for 30-45 minutes.....

[Convective]

A whole line of storms is developing over me and tracking north now! Heading for Cumbria, Northern Ireland and southern Scotland.

[The watcher]

Hearing the Thunder from those storms coming off the Isle of Man but looks like they are heading on a more Northerly path and will miss me.

[weatherobsuk]

In reply to Manchester Piccadilly getting hit, the delays are already noticeable on the scheduled arrivals/departure times for the station. Not good considering its right before peak rush-hour begins.

 

 

http://traintimes.org.uk/live/MAN

[paul m]

What a nice wake up call boooooom

[LadyEv06]

Thundering again here!

[Norfolk Sheep]

Perhaps everyone not in the S and E will stop going on about "Storms are always in the S and E". They most definitely aren't and haven't been since the 1980s.....

[alr1970]

Well, that was a nice appetiser. Half an hour of moderate to heavy rain with occasional thunder. Dried up now. Here's hoping we get some more later, because 3mm of rain isn't going to make much of a dent in the deficit here.

[Darren Bown]

Hoping that stuff in W Midst develops west a bit to give me more than just the odd flash and bang.

[The PIT]

Will the next band do the business?

[Pompski!]

I didn't expect much last night but WOW! At least 5 hours of fork lightning and still going here in Cambridgeshire. Power kept going off and then back on, saw some amazing close ground strikes and was actually a bit concerned for my house at times. Couldn't have wished for better!

[vortex_liam]

That monster over france is getting bigger acording to sat24, Yet no thunder.. It may be a intresting day. but thats fricken huge!

[Coast]

ESTOFEX latest forecast:

 

 

Storm Forecast

Valid: Tue 23 Jul 2013 06:00 to Wed 24 Jul 2013 06:00 UTC

Issued: Tue 23 Jul 2013 01:13

Forecaster: GATZEN

 

A level 1 was issued for the eastern British Isles mainly for excessive precipitation.

 

SYNOPSIS

 

Two troughs are situated across western Russia and to the west of the British Isles. Between both features, a weakening ridge is present over the North Sea. Short-wave troughs will lower the geopotential within the ridge axis over central Europe from the east and from the west. The eastern short-wave trough moves from central Sweden to Denmark and the southern Baltic Sea, the western trough crosses France and the Benelux countries until the night hours. At lower levels, the axis of warm air will move into Germany and the North Sea, whereas colder air masses are advected into western France and the British Isles as well as into the southern Baltic Sea region. Another plume of warm air spreads into Finland and the central Baltic Sea at the northern edge of the Russian trough.

 

DISCUSSION

 

Northern Spain, France, western Germany, Benelux, British Isles

 

A well-defined convergence zone will be still present on Tuesday morning from the northern Pyrenees across France to the central British Isles. Deep moisture was indicated by Mondays soundings that will also be in place on Tuesday. Additionally, lapse rates around 7K/km will overlap with this moisture, leading to mostly elevated instability in the morning hours along and east of the convergence line. Given QG forcing due to several vorticity lobes ejecting from the Atlantic trough into France and the British Isles, thunderstorms are expected at the beginning of the period. These storm clusters are not expected to produce any severe weather given the weak vertical wind shear.

 

Although clouds and showers will limit the diurnal heating, CAPE is expected to reach more than 1500 J/kg especially across central France due to the higher moisture and remaining steep lapse rates. In the noon and afternoon, a vorticity maximum spreads into the area from the west, leading to QG forcing especially from central to northern France and the Benelux countries and western Germany later on. A frontal wave is indicated to form that will cause increasing warm air advection across northern France and the Benelux countries, whereas cold air advection spreads into France from the west. Further north, the convergence zone will re-intensify across the British Isles ahead of the approaching vorticity maxima.

 

Given the rich moisture and steep lapse rates overlapping with quite substantial QG forcing and a well-developed boundary-layer convergence, storms are likely to increase in number and intensity during the afternoon and evening, especially from northern France to the Benelux countries and across the eastern British Isles.

 

Vertical wind shear will slightly increase as 700 hPa winds will strengthen during the day. In regions with backed low-level winds, especially from northern Spain to southern France as well as from the Benelux countries to northern France and the British Isles, 0-3 km vertical wind shear is expected to reach 10 to 15 m/s according to latest GFS and it may be slightly higher as well. Supercells are not ruled out especially across northern Spain/southern France given larger hodographs there. Further north, storm organization will be weaker, but multicell clusters are forecast that may also produce severe weather. Especially aver France, Spain, and Belgium, and western Germany, large hail seems to be a threat, together with excessive precipitation and severe downbursts with storm clusters and/or supercells. Across the British Isles, hail threat will be weaker, although an isolated event is not ruled out. The main threat will be excessive rain and to a lower extend severe wind gusts. Due to the QG forcing, convection can grow upscale forming an MCS later on across northern France or further north over the Benelux countries and southern England with the main threat being excessive rain.

 

[vortex_liam]

The storm N of Caan must be producing some heavy winds anyone got a webcam?Liam

[Bristawl Si]

3.30am 'alarm call' was BANG on time!

So much thunder and lightning - a few claps of thunder that seemed to shake the house!

Pretty spectacular here for an hour or two in the early hours. V heavy torrential rain as well.

Like going back in time to the 'traditional' breakdowns of yesteryear.

[Gowon]

I can't believe this! Everything's missing my area  All we've had is a 10 minute shower in the early hours..

[tara303]

Oh well, hope you folks enjoying the storms, any chances those mcs can hang a left turn at cardiff and head straight to west limerick???? Pllleeeaaaaaase?

 

Drizzling here, still very warm and muggy 19 degrees at7.30am - in Ireland? who'd a thunk it....

 

Seriously - anyone know what today/ronights forecast is, for me???

[azores92]

think thats pretty much our lot now, had 27mm of rain, some fantastic sheet lightning and cannon-esque thunder. Really piddled it down since 5am but its all moving northwards, best of luck to the rest of ya

[nitro_deluxe]

That monster over france is getting bigger acording to sat24, Yet no thunder.. It may be a intresting day. but thats fricken huge!

Yes please! Early morning wake up call, 5am ish..potent storm, lively wind! Strobe lightning and shot-gun thunder - now three bites of the cherry later, last two bites not quite as juicy Great-stuff at long last!

[I Cumbria Marra I]

please please please give me a thunderstorm!

[Coast]

Latest from UKASF:

 

 

 

Synopsis:

 

Moisture plume will continue to destabilise as a sharp upper trough migrates northeastwards, accompanied by cooling aloft. This will result in a large area of potential thunderstorm activity, with greater than normal uncertainty in the forecast evolution given the notorious difficulties in modelling plume breakdowns.

Discussion:

 

** Map updated at 05:46BST **

 

Models have struggled to simulate convection over parts of the country already this evening, so no great confidence is given to any NWP output during this forecast period. A shortwave trough drifting slowly NNEwards has already developed a mixture of elevated and surface-based thunderstorms, particularly over the north Midlands at the time of writing. This zone will continue to track northeastwards across Yorkshire and Lincolnshire, with continued development possible in places, albeit increasingly elevated as a low-level nocturnal inversion develops. Given some uncertainty and poor modelling of this shortwave, isolated development further west across NW England and S/SW Scotland through the remainder of the night cannot be ruled out, but is deemed less likely.

 

 

... ENGLAND, SCOTLAND, WALES ...

 

The next bout of thunderstorms is expected to arrive along southern coastal counties, particularly Dorset, Isle of Wight and Hampshire (possibly also East Devon) from 00-03z onwards, transferring and expanding northeastwards towards London, the Home Counties and south Midlands during the remainder of the early hours of Tuesday morning as a second shortwave trough destabilises the moisture plume. This area of primarily elevated thunderstorms is expected to continue to track NNEwards across western portions of East Anglia and the East Midlands during Tuesday morning, although probably weakening/fragmenting with time later in the morning.

 

Thereafter it becomes a very messy setup, with a mixture of elevated and surface-based thunderstorms expected. It is possible a second round of initially scattered thunderstorms will develop during the early to mid afternoon hours in response to forcing aloft and diurnal heating, particularly in a zone from SE England northwards through the Home Counties, western East Anglia and the East Midlands. DLS is marginally better, so if cells can remain fairly discrete then they have the opportunity to become reasonably well-organised. Most models simulate a gradual merging of initially scattered thunderstorms into a more defined QLCS towards the end of the afternoon and into the evening, as this line continues to slowly drift eastwards. This QLCS is likely to extend from S/SE Scotland down the Pennines/E England towards the Home Counties, capable of producing strong, gusty winds and perhaps an isolated tornado given slightly backed surface winds ahead of this line. 

 

The slow motion of these thunderstorms and subsequent QLCS coupled with PWAT values of 30-40mm suggests local flash flooding may occur, especially given how dry and hard the ground is currently. Hail between 2.0-3.0cm in diameter is possible from any stronger cells, particularly in the afternoon where any cells can remain discrete.

 

Please note given the complex and (to a certain extent) unpredictable nature of his setup, a few isolated thunderstorms cannot be ruled out elsewhere across the British Isles.

 

 

... IRELAND, NORTHERN IRELAND ...

 

Cooling mid-levels, falling heights and the approach of an upper low will steepen lapse rates through the day, as diurnal heating raises CAPE values to 600-700 J/kg. Scattered showers and a few thunderstorms are therefore expected during the daytime, although may tend to merge into a larger area of showery rain across western parts for a time during the afternoon and evening. Here, hail between 1.5-2.0cm in diameter and a funnel or weak tornado cannot be ruled out.

[ballybabe21]

Thunder quite close to newton Aycliffe. Haven't seen any lightening yet.