Chris K

If this "key uncertainty" does unfold I may start accidentally throwing computer equipment from the window

Looking at the fax charts, I assume those particular storms are forming along the first surface trough where on the 0600hrs was over NW France and by 0600hrs Weds sat over the W country and Wales. Can see why the Met Office extended the warning area. This does not necessarily mean there won't be further changes.

My total guess would be that they are waiting on the 06z model runs as a minimum first.

Lies...the Bristol shield will hold up.

To be fair they are presenting a broad risk area for the storms - It's not worth taking the rainfall locations literally as shown on the map. Considering there are still disagreements within the key models, there is still plenty of uncertainty, as always.

I remember staying up late, only to watch sods law unfold before my eyes and the storms dwindled away literally as they touched the edge of Bristol. We did manage a few flashes and bangs North of the city, but nowhere near to the scale of what some on the S coast experienced that night!

The risk of storms still hasn't gone away for Tues night into Wednesday. The fax charts are showing the surface trough moving up from the South as you can see off the Southwest coast at 1200hrs Tues and by 0000hrs Weds it is lying across England and Wales. The Netwx-mr model is showing some heavy rainfall moving up as well and this matches quite well with the positioning on the fax charts. I wouldn't take this precipitation chart literally but it gives an idea. Also, when comparing this to the fax charts, I would expect a little movement eastwards. Whether this will be thunderstorms or bog standard rain I will leave to the more knowledgeable to provide the more technical convective charts, but it looks quite promising for now!

Ssshhh don't start that just yet!

To be honest I think most of England and Wales are in the risk zone for now, but until we start seeing the details from the higher resolution models and skew-t charts, I don't have the knowledge to be specific for locations. The netwx-MR for example shows rainfall developing across more SW and central areas, Wales, parts of the Midlands/ N England and up through the Irish sea. However last time it started to push all this eastwards as we got closer to the day. Equally it could move more westwards! Difficult to tell at this range. Can't totally rely on models either - great for guidance but it comes down to watching the radars and skies on the day.

Well the GFS 12z keeps the theme of an outbreak of storms across much of S England and Wales that push North overnight. Things are nearly into the higher res range, especially by late Sunday on-wards, so we will get a better idea then. It is also worth keeping an eye on the fax charts (surface pressure analysis) issued by the Met Office. You can see from the below outputs that developing upper warm front off the S coast at 1200hrs tues and by 1200hrs Weds it has pushed across much of England. Looking at other charts currently available, this is where I would currently expect to see storms initiate through the night if the favourable conditions are available. The centre of the developing LP moves from the Bay of Biscay to reach Wales by 1200hrs Weds. These are worth watching as they update these charts each day.

Next week (specifically Tues night/Weds) still looking quite interesting in terms of potential storm development. Storms are modelled to break out across much of the South and move Northwards/. My only concern is that this seems like a repeating pattern we are in, with the associated tendency for the Jet and steering winds to be underestimated due to the nature of the synoptic setup. Although we do at times see things actually move back West, I would expect an eastward push is likely due to the Low pressure system edging in more quickly than originally modeled and on a more NE path. Something more akin to the ECM perhaps.?

To be honest, a few days ago it looked promising for us over here, but the shift eastwards came in day by day in the model outputs. The problem is, as AJ mentioned yesterday, the steering flow (T500 and T700 I believe) has resulted in a much more progressive movement of potential thunderstorms, rather than the original more Northward path up from the S coast. This originally meant showers were going to form more widely across SW quadrant of England along the surface trough, but that is currently moving across the SE corner, with the storms forecast later to develop along areas of wind convergence.

Looks like that is a weakening cold front moving in across the country later on. Wind convergence zones are due to form ahead of this, which is the main trigger I believe that is meant to spark scattered thunderstorms later on this evening across some parts of the Midlands and E/NE/SE areas later. If it was an active slow moving cold front I assume we could have been looking at something more widespread. Checking the most recent met office surface pressure chart the corresponding symbol: http://www.metoffice.gov.uk/guide/weather/symbols

Definitely a tiny bit more eastward shift again in model outputs, with the emphasis of thundery showers across NE England and then later down into C/E/SE England as convection kicks off. I think some people are perhaps writing this off too early though, as there is always a lot of uncertainty with storm development. Some forecast to see storms may end up with zilch, whereas some who thought they had no chance get one! I know I use them extensively but precipitation charts are not always the best tool to use in isolation. The skies certainly looked unstable on my drive into Bristol this morning - but I think it'll be developing east/NE during the afternoon, rather than staying over here. Interesting to watch it develop nonetheless...

AROME 00z run still shows some showers breaking out this afternoon in the main risk zones. It has been pretty close so far, I think? (Ignore 1300hr output as it seems to have not updated properly - the rest are fine)

12z high res AROME precpitation. You can see the two "waves" of storms being forecast. Barely grazes my area if at all but hopefully some people will do well from this, particularly the further East you are.

Agree. The Netwx Sr model keeps the first opportunity of storms moving NE, sticking close to the S coast towards London during tomorrow daytime. Then, a line of thundery showers break out early evening down the spine of England moving Eastwards. I wouldnt quite say the W country has no chance but the faster progression eastwards is appearing as we get closer The AROME model is further east yet again and I rate that model quite highly at the moment. Whilst I know models are only a guide and it comes down to watching radars on the day, my excitement has dwindled really. Met office warning area still looking the like the main risk zone, but a movement east may occur.

Ah but that is mainly showing surface CAPE in line with surface heating of the day. You also want to be looking at the MLCAPE and other convective charts - keep an eye out - I'm sure some of the more knowledgeable will post them over the coming couple of days as we enter a higher resolution on the models.

Yes, but with a slight more eastward emphasis starting to appear now in my opinion - moving towards what the Met office warnings show. However on the grand scale of things, a tiny adjustment will be substantial when it comes to seeing who gets the storms and who doesn't, in our part of the world.

Probably the two most sickening let downs for my area - smack bang in the middle gap only for storms to re initiate to our North, and the other time veering away just before reaching us. Classic.

Interesting, but certainly a quicker evolution eastwards when comparing it to the 6z run. However, too early to worry about that right now. I am happy just to see another opportunity developing at this stage.

At the moment, I feel next week is looking quite good for some convective action. It may not be the same as having a large plume of heat de-stabilizing , but there would still be enough instability around for a more widespread area to see some storms developing, in the form of homegrown thundery showers. As ever the nature of these may be quite hit and miss. Still, with enough daytime surface heating, there could still be some crackers if the timings are right. Will be keeping an eye on things as we move through the weekend

At least your office has AC - I am in a large building designed with the lovely glass ceilings so essentially 3000 staff, with computers, inside a giant greenhouse. Grim. Our mercury thermometer says it is 35 degrees in here. But I feel more sorry for those working outside in the sun!! It also makes me sick I won't be seeing any storms to wave the heat goodbye.

It isn't much, but certainly some clouds starting to develop to my East (I live close to Gloucestershire/S Glos border). Was clear blue sky only 30 mins ago. I guess later we will see if the cap can be broken. Met office rainfall forecasts showing very isolated showers around 4-5pm.