Good evening. Here is the report on the 12 noon output from GFS, UKMO, GEM, NAVGEM and ECM for today Wednesday July 17th 2013.

All models continue to show High pressure edging slowly North over the British Isles over the next few days. Changes will be slow and will mostly affect Scotland over the coming days as finally the cloud and rain clear to give these areas a share in the fine and very warm weather that the rest of the UK as enjoyed for a couple of weeks now. Other changes involve the increase of the risk of low cloud and mist moving in off the North Sea to Central and Eastern areas night and morning and the chance of isolated heavy showers or thunderstorms in places over Southern and Western parts of England and Wales in the coming days with the highest temperatures transferring from the Se to the SW from tomorrow.

GFS then shows thundery weather gradually extending North and East across the UK next week with some heavy downpours in places with cooler and fresher weather slowly taking control over most parts by the end of the week. This cooler and somewhat more changeable weather is then shown to last through the rest of the run with occasional rain mixed with brighter spells and temperatures closer to the average.

The GFS Ensembles show a definitive change in temperatures from around the 25th-27th. Until then hot and humid weather persists for most with very little rain. A thundery breakdown from the SW is now the favoured option late next week with some torrential downpours likely before the weather turns cooler and more conventional with more Atlantic based weather bringing rain and showers across the UK at times.

The Jet Stream currently blowing well Northwest of the UK remains here a while longer before becoming more diffuse and broken before the flow becomes directed towards the UK from the west in 10 days or so.

UKMO looks set fair still on Tuesday of next week with fine and very warm conditions for many with still at that stage only isolated showers or thunderstorms to dampen the dust.

GEM tonight shows High pressure still largely controlling the UK weather through the latter half of next week and weekend. The ridge is shown to be best positioned for Northern Britain with a ridge always close by up here while Southern regions are at risk of thundery showers creeping up from the South as low pressure lies over France. Although still very warm for the south the very highest of the temperatures will of waned by the end of the week.

NAVGEM shows any changes temporary as a thundery trough crosses NE through next week before High pressure builds back up from the SW late in the run with a chance of another surge of warm and dry weather developing.

ECM tonight shows slow changes next week involving the infringement of slack thundery low pressure troughs edging up from the South giving rise to some very heavy downpours and thunderstorms locally but a lot of dry weather too in maintained high temperatures. Late in the run the threat increases further with the potential for some quite severe thundery weather in places towards the back end of next week as High temperatures refuse to be displaced at any speed by thundery Low pressure edging into the West and SW.

In Summary over the last few runs there has been a trend towards a thundery phase of weather as we move through next week. The extent of this differs between models but all show something of a threat. I hesitate to use the word 'breakdown' in all of this as high pressure never looks like moving far away unless GFS has the handle on this right and due to the ranges of time we are talking being beyond 6 days then there is still a good chance that High pressure may prove too resilient and lessen the extent of thundery activity though I will concede that with every run that shows this trend from now on, the chances of a moderation in the heat and the threat of some useful rainfall in a thundery form increases.

one hell of a gm run

http://www.meteociel.fr/modeles/geme_cartes.php?ech=144&code=0&mode=0&carte=1&archive=0

Thanks Martin

ECM also brings the 20C isotherm within a whisker of the south coast!

http://www.wetterzentrale.de/pics/Recm1682.gif

http://www.wetterzentrale.de/pics/Recm1922.gif

Very very hot and humid.

Funnily enough, yesterday morning's ECM 00z run suggested something along those very lines, i.e HP not really relinguishing its grip over the UK next week much, if at all. There has been a more towards something more unsettled since this time yesterday, but nothing is set in stone yet.

what chance if any of getting 20 or 25C uppers over southern England - I wonder if that is possible.

http://www.wetterzentrale.de/pics/Recm1682.gif

http://www.wetterzentrale.de/pics/Recm1922.gif

 thats a whole week out and in forecasting terms borderline.

Possable 22 uppers 10th august 2003       Rob spoke about that last night

http://www.wetterzentrale.de/topkarten/fsreaeur.html put that date in

Thursday next week looks a real scorcher from there 33C I reckon many of us would see.

Cheers Polar - thanks.

For sure! No one is saying it's nailed on nor definite. Plenty of uncertainty.

Turning incredibly hot next week with an interesting threat of thunderstorms from the SW from midweek.

I am starting to get the feeling judging by how the models are evolving is that this cut off thundery low scenario will have some influence for a few days, (especially the SW) before eventually filling in situ.

At the same time as the thundery low fills, the Azores High then reinforces itself NE'wards and then links with the old high pressure cell over Scandinavia...hence maintaining the dry, very warm, locally hot conditions as we head into August.

Very little evidence of an atlantic breakthrough tonight.

Of course. Nobody is saying anything else. I do wonder what your agenda is in saying any warmish charts are unlikely to come off but latching onto any showing a breakdown. Why can;t we just discuss what the output actually shows, and the implications that would have, rather than trying to score points?

That would be amazing steve if something like that came off - it really would.

Something for us all to follow.

I think that is entirely possibly Steve, and the UKMO 144hr chart hinted at something along the lines of what you described in the 12z run earlier this evening. Of course, a thundery interruption is entirely possible during next week, but there again there's as much chance IMO that the models could drop this idea at a later time the same way they dropped the return of LP from the NW that the GFS and ECM toyed with briefly last weekend. All will become clearer over the next couple of days I think.

Of course. Nobody is saying anything else. I do wonder what your agenda is in saying any warmish charts are unlikely to come off but latching onto any showing a breakdown. Why can;t we just discuss what the output actually shows, and the implications that would have, rather than trying to score points?

not trying to score points, but if i am dissed for latching on to show charts with a breakdown , i am quite likely to comment on cherry picked hot charts a week away. live and let live i say .

+1 to that  and excitement over cut off lows and rebuilding pressure seems to disregard GFS in F1 but nevermind eh?

As long as it's made clear what's actually the case and what's isn't, I'm sure we can all tolerate a bit of favourism from a member here and there. How else would we survive the winter period?

So please, let's keep things on topic - no need to continue debating the right to free speech or whatever...

I'll accept the +20 isotherm if we finally get the -20 this winter as payback ( though I'll accept -15)  

Hi James, it seem that Navgem was the first model to predict 20C uppers next week that we were not sure if this supported but now it possible being supported that next week would be the hottest one.

The cut off low is slower to form on the 18z and as a result the plume is weaker meaning temperatures are about a degree lower and thundery acitivty is a bit less. However, temperatures would still be widely in the low thirties and Thursday, which on previous runs was cooler, would still see temperatures in the low thirties.

yes, yes Matty go on