ECM looks very good for the 31st don't despair just yet. 

http://www.wetterzentrale.de/pics/Recm1921.html

Thanks, I will bank that one 🙂 The positive I guess is how we cannot even forecast the low tomorrow that well, so hopefully that low next week disappears sharpish.

Good luck to you. You're right in that forecasts for a week ahead are changing daily. We had the same issue in May 1997. It rained at some point pretty much every day in the week leading up, but the big day itself was great.

British weather sucks most of the time, though.

Huge rainfall spike for the south tomorrow. 

 I dont think you can tell yet an exact forecast for your location on a day , 8 days away. It might not be settled and hot, but chances are it will be mostly dry . It would be unlucky if it was a real soaker. I dont think i would want it scorching hot , all done up in suit and tie and the bride and groom sweating like a pigs 

With the ground so dry, with very heavy rain predicted to develop as it moves west to east across the South tomorrow will just run off these surfaces and lead to flash flooding. Wouldn't be surprised if thunder was heard given the timing of instability, more particularly towards the SE.

http://www.wetterzentrale.de/pics/Rtavn304.gif
http://www.wetterzentrale.de/pics/Rtavn364.gif
http://www.wetterzentrale.de/pics/Rtavn3611.gif

Each new run seems to develop more organisation to tomorrow's event, with some particularly heavy rain crossing the far south from west to east.

I await the high-resolution model runs with interest.

With this and further persistent rain on Sunday followed by showers on Monday, the prolonged drier than average spell across the south look to be well and truly over.

In light of which I'm glad to see GFS offering some warmer temperatures for Wed-Thu next week under a weak ridge supported by a shallow low over Europe. It's the most hopeful outlook I've seen from GFS for a while, discounting the longer-range teases (which have been tenuous from GFS lately... though ECM has at last begun projecting a decent build of pressure across the UK with some consistency).

The MJO projections have updated after a three-day hiatus, and show that UKMO and JMA are sticking with a new event building in the W. Pacific at some point in early August. ECM seems to be sniffing out the idea at now, but GFS remains out on a limb.

Based on what I know about tropical convection and El Nino events, this encourages me to put more faith in UKMO/JMA than usual, and less than usual in GFS. Bear in mind this only really applies from around day 8 onward (which is beyond UKMO's public output range).

Looking to be a very very wet day tomorrow for parts of the South.  

http://modeles.meteociel.fr/modeles/wrfnmm/runs/2015072312/nmmuk-25-37-0.png?23-19

Extremely windy in the East for the late July. 

http://modeles.meteociel.fr/modeles/wrfnmm/runs/2015072312/nmmuk-11-40-0.png?23-19

When you run through this sequence, note how the very far south east tip of Kent actually avoids the rain - the Folkestone Rain Deflector in full effect? Of course, this is just one of the many options offered by the various outputs - even though it is at close range.

http://www.meteociel.fr/modeles/wrfnmm.php?ech=3&mode=1&map=330

It also shows how the "eye" of the developing low pressure system passes right over Kent in the small hours of Saturday morning.

http://www.meteociel.fr/modeles/wrfnmm.php?ech=1&mode=2&map=330

Is it just me or is tomorrow's event being underplayed?  It does seem to me that there could be some significant localised flooding.

Poor ECM run tonight, next weeks high looks very weak with low heights so plenty of cloud I suspect but then the high collapses as low pressure edges in from the Atlantic.

No improvement on this run, MetO also very poor and I just can't be arsed to look a GFS.

Andy

The models have really upped the intensity of the event over the past 24 hours of runs.

The Met Office could place total faith in them due to being the most recent, but standard practice is to take into account how consistent the runs are with the previous ones, so they may hesitate to go all-out with predicting an absolute deluge.

Having said that, the official warning talks of 'the potential for over 60mm', which seems a very reasonable interpretation of the 06z and 12z high-res model runs to me 

Glad to see the models are a lot less keen on a repeat event next week. In fact a GFS/ECM consensus has emerged for weak high pressure to be in control from Wednesday for at least a few days  It looks a bit on the fresh side mind, with a risk of a lot of cloud tending to bubble up during the daytime. A benign spell after the drama of tomorrow and the autumnal theme of Sunday.

Beyond that... who knows. Subtle hints from ECM that the high-latitude blocking will start to shift position toward something more like we had to kick off the month (some serious heat potential but unstable), while GFS shunts it over to Svalbard, which is arguably a better outcome if you want a more sustained spell of warm, settled weather affecting a large part of the UK. 

It seems to me that the models are still unsure to some extent as to what is likely to pan out after the LP early next week has moved off to the continent. The ECM 12z attempts to build pressure after this over the UK, but it is a less convincing effort that was shown on the 00Z and, alarmingly, it has reinforced blocking over Greenland at the same time. Hopefully it'll be an outlier; this morning's ECM did not have such strong heights over Greenland by the end of the run, and neither does the GFS 12z. Consistency has in some ways been lacking from the models at times recently.

Given that there still appears to be some uncertainty over the extent of tomorrow's rain for southern and possibly central England, it isn't surprising that there is still a question mark over next week, once the low forecast for Sunday & Monday has departed to the east.

I'd say that at 144hrs, UKMO looks a bit more promising that both ECM and GFS in that the Azores High looks to be somewhat stronger and better organised than on the latter two models. Although ECM and GFS look almost identical in the chart for 6 days ahead, they take differing paths thereafter, with GFS making a more convincing effort of building HP over the UK for a while and deflecting the LP in the atlantic to the NW at 240hrs. ECM, as I said above, goes for reinforced blocking over Greenland once again pushing the jet further south, and the brief pressure rise it shows for a time next week is lesser than that shown on GFS.

For once, I hope GFS is correct, although FI doesn't look too clever I must say!

As is always the case, pinning your hopes or despair on any chart beyond a few days is stupidity. All summer long all the models have flipped around wildly at only 3 or 4 days out

The 12z NMM high res model accumulated precipitation chart at 0z on Saturday shows an area of 50-60mm of rain aligned SW-NE from Dorset to Norfolk. At this time rain is still falling across much of this area, particularly in East Anglia.

So there does appear to be a possibility now of >50mm falling in quite a wide area.

http://modeles.meteociel.fr/modeles/wrfnmm/runs/2015072312/nmm_uk1-25-36-1.png?23-19

GFS also showing >50mm in places

http://modeles2.meteociel.fr/modeles_gfs/runs/2015072312/39-777UK.GIF?23-12

The EURO4 model has lower totals at around 35-40mm.

http://expert-images.weatheronline.co.uk/daten/proficharts/en/euro4/2015/07/23/basis12/ukuk/rsum/15072512_2_2312.gif

German ICON model has even lower totals with only the far SE corner exceeding 30mm

http://modeles.meteociel.fr/modeles/icon/run/iconfr-12-43.png?23-12

So still plenty of uncertainty but it does at least look like the gardens in the south will see a good soaking which is good news. I have only recorded 48mm of rain since 15 May so we are definitely due a significant rainfall event.

And Euro now comes with a similar idea - the bulk of the rain juuuuuuuuust skimming by me by a whisker off to my north west, I think it's to do with the "eye of the system" passing right over my location tonight: http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=euro4&MODELLTYP=1&BASE=-&VAR=prec&HH=21&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

Of course, it's very much an ongoing situation with last minutes adjustments. It'll be right down to radar watching on the moment.

That on the time frame but you will get hit with heavy rain as it move eastward and doesn't jump from location to location.  The radar look weak and rain kept fizzling out as it move NE. Some already passed here and it odd no dampness found here.  I think all the posts talking about high nationwide rainfall totals had been over the top, yes if we are in USA then that can be done but not in the UK with standard lame rainfall events of light to moderate rain and not heavy often as shown on the radar.

We really need the rain down here as its very parched in many places and I am very much hoping that the overcast skies over the next 5 days actually deliver some decent amounts of rain.  The sunshine anomalies will be of great interest this month as I think its been  sunny locally compared to average.

By Wednesday (29th) the ECM shows the unsettled interlude for the south to have been and gone.

Fair point Matty. I think the often slack pressure patterns we've often had over the past month have only caused the models more problems that might have been the case otherwise.

If only it were . . . . 

Good work from the models today, with forecast rain moving in to the South please the potatoes and tomatoes.