Uk Convective General Discussion & Forecasts, 20th June 2012>

[ZONE 51]

Just checked through GFS's Theta charts, it looks like the moist humid air is to plume up into Southern areas by early morning, should be sweeping in now, especially the SE, this should result in an intensification of the rainfall, and some thundery activity.

The storms to result from all this during the day could be a major flooding issue, and thats before we get through the flooding from this front, so a wide period of time for some action, but also a concern from the potential rainfall overnight/today.

[ZONE 51]

Latest MetO radar shows some intense downpours developing around the Portsmouth/Southhampton area within the main heavy rain area, also to note is the Channel rain has got more organised again, i would expect this to continue as it moves east/northeast, the thunder more likely as it enters the Southeast i would imagine, this is because the de-stablising plume should engage with the rain as it enters the region. Also some heavy showers breaking out ahead of the rain into the Southeast now.

Edited June 21, 2012 by ElectricSnowStorm

[ZONE 51]

Horse head cloud sat!!

[Biggin]

Something about to cross the Brest peninsula ?? Coming our way ?? http://www.raintoday.co.uk/

[Norfolk Sheep]

Ooh, Look East weather had a flashy thing Currently dull, grey and muggy. Will be watching developments with interest!

[Supacell]

I have had a look through the charts (the ones Coast will probably post shortly for drawing and scribbling over ) and my take on things is this, put in very non-technical speak because i am a non-technical person:

The plume from France will soon be entering the uk and this could allow some thundery element to the main frontal band, although i would say the risk of anything more than the odd rumble this morning is low.

It is around midday (behind the front) that storms could start to fire but it is reliant on cloud breaking and sufficient heating to occur. I would expect this to happen around London north towards the Wash, including the northern Home Counties. Through the afternoon the area moves and expands northwards and eastwards into Lincolnshire, the East Midlands and East Anglia. If i was to pick a sweet spot then i would go with somewhere between Grantham and Spalding. There is some shear and so some organisation could occur with the threat of hail and gusty winds, maybe even a tornado risk around the aforementioned sweet spot. Having said that, the best shear and helicity does not look to overlap the best of the CAPE and so this risk is very low. Even so, any storms that do develop will be in a region of moderate instability and there could be frequent lightning. There is also the real risk of localised flooding with storms capable of producing a lot of rainfall.

Teatime onwards the area moves NE to hug the coastline around NE Lincolnshire and E Yorkshire, and my take is it then looks to organise into an area of rain that will move back into the country and give N England a very wet night with a risk of flooding. There could again be some thunder, but the risk of thunder begins to diminish towards dusk.

Another area of interest would be the far SE of England later on today. Around teatime and through the evening there could be some very heavy and active storms moving up from the near continent. As usual, the best is reserved for the low countries but if these do clip the SE then there could be frequent lightning and torrential downpours. I would say areas to the SE of London look at risk with Kent looking best placed. The risk here will subside after dusk also.

An interesting day coming up.

[Lynxus]

Well,

Had a bit of rain last night. Nothing as severe as I thought ( or as the papers and metoffice led me to believe )

Oh well. Maybe next year then lol.

I find todays chance of storms for this region very low.

[tinybill]

http://www.raintoday.co.uk/

some very heavy showers over the french coast at the moment

Edited June 21, 2012 by tinybill

[Coast]

I have had a look through the charts (the ones Coast will probably post shortly for drawing and scribbling over )

Late in today!!! Give me a few minutes and I'll fill a post with colour!!!

[Coast]

OK, here we go with my round up of applicable/not applicable (delete as necessary) information:

A big forecast this morning from ESTOFEX and a tinchy bit of it applies to us in the SE:

DISCUSSION

... France, Benelux, W-Germany and parts of UK ...

Apparently, the intense and progressive vorticity lobe and attendant synoptic boundaries dictate convective initiation (CI). The mid/upper streamline pattern becomes supportive for prolonged/deep lift over NE France/Benelux, with diffluent pattern just ahead of the main trough axis. In fact, unusually strong diffluence is expected over Benelux during the evening hours in response to a negative tilted trough evolution over UK.

A step down to the surface shows an eastward moving occlusion, coupled to the sharp mid-level trough axis, which also increases lift for DMC. Timing of the trough axis/occlusion will be 15Z over C-France, approaching Benelux from the SW at 18Z onwards. Despite overall favorable forcing, we keep an eye on the unusual trough axis configuration (E-W alignement during the evening hours) over UK, which may place NE France/Benelux beneath intense subsidence during the time frame with peak DMC activity.

Modified forecast soundings show somewhat indifferent profiles. Adequate BL moisture is present with surface dewpoints in the mid tens with similar values in the 950 hPa layer. Lapse rates reveal near neutral values but steepen somewhat in the course of the day as somewhat cooler mid-level temperatures overspread the moist BL, so 500-1000 J/kg MLCAPE are expected. A concentrated tongue of higher BL moisture along the confluence zone/occlusion may assist in even higher values, so adequate CAPE for DMC is forecast.

Kinematics not as straightforward as CAPE forecast. Prefrontal diffluent streamline pattern offers 10-15 m/s DLS (E-France/Benelux) with 20 m/s DLS just along the occlusion/trough axis and 20-30 m/s DLS over the E-English Channel/W-Belgium and Netherlands, as an intense 35 m/s 500 hPa streak approaches from the SW. Hence, probabilities for organized DMC increase from SW-Germany/E-France to Belgium/Netherlands.

Early and scattered to widespread CI is expected over most parts of C-France. Diffluent flow regime and messy surface wind field assists in random development with slow and erratic storm motions. During the more discrete initiation stage, large hail and strong wind gusts will be the main hazard. Locally heavy rain accompanies that activity. At 15Z onwards however, incoming forcing and sharpening occlusion start to be the foci for widespread line-up of storms and an extensive eastward moving MCS is forecast to cross E-France at around 18Z and entering SW/W-Germany thereafter. However current thinking is that this MCS remains quite disorganized with only small line segments showing some better organization (embedded multicells/isolated supercells). The main risk will be isolated large hail and strong to isolated severe wind gusts. However a narrow swath or two of severe wind gust reports over E-France can't be ruled out. The MCS weakens, while entering W/SW Germany and becomes sub-severe thereafter.

Further north, strength of forcing and incoming intense mid-level jet may assist in a well organized MCS event, which consolidates over NE France with rapid movement towards Benelux (18Z onwards). A few concerns exist:

a) Potential scattered CI in the prefrontal air mass over Benelux during the afternoon hours (beneath diffluence) may spark a cluster of storms ahead of the incoming MCS, which may assist in more stable inflow air parcels for the approaching MCS

CAPE plume also fans out ahead of the MCS

c) strong subsidence overspreading the area of interest

However most models show a potential strong MCS event and given strength of forcing, we agree that this solution seems to be plausible. Hence, a swath of concentrated strong to severe wind gusts may evolve over Belgium, the Netherland and NW Germany after 18Z. An isolated tornado event can't be ruled out with increase of LL shear and lowering LCLs. Heavy rainfall may occur but progressive nature of storms probably precludes excessive rainfall events.

For now, we do not want to include a level 2 over Benelux with ongoing uncertainties. The level 1 risk becomes more conditional over E-/C-France.

Scattered storms are also forecast over SE-UK, placed beneath the left exit region of the mid/upper jet. Strength of diffluence and connection to the moisture plume over NE-France may result in scattered thunderstorm development and rapid clustering. Heavy rainfall will be the main hazard with isolated marginal hail and strong wind gusts in stronger/more discrete storms. Drier air mixes in from the SW after 21Z and brings thunderstorm chances to an end. Wrap-around moisture may also result in heavy rainfall over parts of UK/Scotland during the night.

Wow, now that's in depth and shows how complicated this current pattern is!!! SkyWarn still have their forecast valid from yesterday, here are some of the charts.

Jet sending things right up through the UK:

Catching the SE corner through the day??? I'll take some of that lightning possibility please!!!!!

East Anglia in the firing line?

Can that French stuff reach us???

No more rain thanks!!

flow:

Tornado chances in EA?

We might be lucky this morning, dew points are right up and it feels as muggy as hell here. Nothing last night for me except rain, but I'm out and about in Sussex today so might get a chance to see some action through the day if this complicated and messy set up allows!!!

I'd probably rather be in East Anglia though this afternoon!!!!

[tinybill]

coast cant wait looking at that lot over france at the moment that looking like its coming the uk way things could get a bit interesting later in the day!!

[Lewis]

Good Morning,

A risk from ESTOFEX today for parts of the South, and then SE, EA and parts of Yorkshire/Lincolnshire for severe thunderstorms.

A rather large downgrade on this mornings NMM on the CAPE and LI, it's not as widespread, although for some areas there is sufficient CAPE to produce severe storms, with a Lifted Index of -3 to -4.

... France, Benelux, W-Germany and parts of UK ...

Apparently, the intense and progressive vorticity lobe and attendant synoptic boundaries dictate convective initiation (CI). The mid/upper streamline pattern becomes supportive for prolonged/deep lift over NE France/Benelux, with diffluent pattern just ahead of the main trough axis. In fact, unusually strong diffluence is expected over Benelux during the evening hours in response to a negative tilted trough evolution over UK.

Potential will boil down to whether or not we can get that sun out with breaks in the cloud, for areas in the East and SE later this afternoon if this happens convection will spark off some storms quite quickly.

Favored areas are EA and the SE. Later in to the evening the risk extends North Eastwards in to N Lincolnshire, East Yorkshire.

Lewis

Edited June 21, 2012 by Humber

[Coast]

It's not really got going there yet, but keep everything crossed!

[Supacell]

I'd probably rather be in East Anglia though this afternoon!!!!

I am planning on heading that way with somewhere on Lincs/Cambs border to start. I feel the petrol costs mounting up today but i am thinking/hoping it will be worth it.

Edit: The Wash area may be a good bet.

Edited June 21, 2012 by Supacell

[Coast]

Edit: The Wash area may be a good bet.

I think so, but anywhere North of Essex may be worth starting in late morning onwards. I'm less sure about us this far SE, but maybe the tip of Kent if you live there.

[Hughsey]

Look to be in a reasonably favourable area today, excited by the chances of some storms .

[syncmaster]

Good Morning,

A risk from ESTOFEX today for parts of the South, and then SE, EA and parts of Yorkshire/Lincolnshire for severe thunderstorms.

A rather large downgrade on this mornings NMM on the CAPE and LI, it's not as widespread, although for some areas there is sufficient CAPE to produce severe storms, with a Lifted Index of -3 to -4.

Potential will boil down to whether or not we can get that sun out with breaks in the cloud, for areas in the East and SE later this afternoon if this happens convection will spark off some storms quite quickly.

Favored areas are EA and the SE. Later in to the evening the risk extends North Eastwards in to N Lincolnshire, East Yorkshire.

Lewis

Mornin lewis, unless we can get rid of some of this murky rubbish during the day were really goin to struggle. the potential is there for a lot later in the day it as to be said,

[Coast]

Blimey, look at those dew points out there!!!!

http://www.netweather.tv/index.cgi?action=current;type=maxd;sess=

There's some fuel in the atmosphere, now we need a few sparks!!!

[fromey]

Morning all, sun has come out here, feeling very warm and humid, currently looking at the rain coming off off the breast peninsular and heading north east.

fromey

[A.J]

Just to get 'no storms club' members in the west reaching for their prozac

To sum up the model outputs & forecasts.....very promising for the east, very poor for the west....you just can't make this stuff up!

[Lynxus]

Just to get 'no storms club' members in the west reaching for their prozac

To sum up the model outputs & forecasts.....very promising for the east, very poor for the west....you just can't make this stuff up!

Someone pass me the community revolver please.

[Carl46Wrexham]

Just to get 'no storms club' members in the west reaching for their prozac

To sum up the model outputs & forecasts.....very promising for the east, very poor for the west....you just can't make this stuff up!

Proof were it required that one of the biggest myths going is the one about the British weather being unpredictable. It is all too predictable.Fact.

[fromey]

Someone pass me the community revolver please.

Me First!!

[Kain]

Someone pass me the community revolver please.

I'll take it after you...

[Coast]

Brussels looks like the place to be!!!