Good support for a UK based Anticyclone in 10 days time from the ECM Ensemble pack this morning.

http://www.wetterzentrale.de/pics/Reem2401.gif

Not unusual for the start of September really is it!

Regarding Cristobal transition from fully tropical starts at 96hr

http://www2.wetter3.de/Animation_12_UTC/96_5.gif

System officially looses tropical status at 120hr (progged) 

http://www2.wetter3.de/Animation_12_UTC/120_5.gif

Looking more settled by the weekend and warmer to and this continuing well into next week.

Typical start to September then.

All the main models going for high pressure over us in early September - a growing trend tonight for something warmer and drier as we begin Meteorological Autumn.

Drier weather next week is the order of the models this morning. You can see my full analysis for this morning's 00z outputs here.

http://www.norton-radstockweather.co.uk/NEW-Model-Analysis(2859336).htm

Shall be glad to see some better weather .Schools back next week so weather changes....

Had that this morning...

After another run of days with frontal rain and showers to contend with, and temperatures a bit lackluster during the day, the models do seem to be coming together on the idea of a ridge building Saturday-Sunday from the SW as LP finally departs to the E or NE.

This could see a clearance of showers from the southwest during Saturday, followed by temperatures to rising to near 20*C, then perhaps 21-23*C widely by Sunday if we get a bit of luck with the cloud amounts.

That ridge then looks likely to gain a foothold to our NE, potentially forming a blocking high. The surface conditions then depend on the airflow and its source - the ECM 00z and GFS 06z runs show a slack flow initially, with a tropical maritime airmass circulating around the HP cell, before a southeasterly feed establishes as the high locates more to our NE, keeping things on the warm side, potentially very warm.

The GFS 00z run developed more of an easterly instead, largely due to more of a trough sliding under the building ridge this weekend. That seemed to hamper temperatures rather a lot - though I suspect the model overdid the supression a bit in the lower-res (192-384 hours).

I'm keeping an eye on the potential for the jet to develop a sharper trough to our west than currently modelled, bringing more of a southerly flow later next week with attendant heat and storm potential. The hot air on offer looks to be at the high end of the scale, as heat displaces from Africa to Spain and develops a broad region of 20-25*C 850hPa temperatures.

I don't see how anyone can be so confident of a calm start to september with Hurricane cristobal wahsing up on the UK is well within the realms of possibilty. When this storm transitions to an extratropical storm, barycyclic effects could cause it to develop into a bomb, particularly if it interacts with a frontal system. This means we are looking at a potentially very deep area of low pressure (<960mb) developing over the course of 36 hours that the models are underestimating. The effects of this are uncertain, and while the storm is more likely to pass to the north of the UK than over it, I wouldn't rule anything out yet.

Hi all,

Here's today's video update:

September Song On The Way?

http://www.gavsweathervids.com

All the sings point to a warmer/drier spell next week. Enjoy.

Indeed. The control run going for 26-27C for the London area by the end of next week. 

JMA pumping up very warm uppers to the country. http://www.wetterzentrale.de/pics/Rjma1682.gif

Well now this is getting very interesting indeed!

There remains some short term disagreement on how the UK trough exits the UK this weekend; GFS has it scoot off east while ECM absorbs most of it into the system containing ex-Cristobal.

Remarkably, both versions of events are now shown to result in a ridge across the UK with a tropical maritime airmass giving some very warm, humid weather, temperatures in the mid to high 20's potentially.

With Cristobal looking to be a very large system (actually rather a lot like Sandy of 2012...), the amplification of the jet stream in response is likely to be very strong.

With the weaker ex-Bertha, a lesser amount of amplication still managed to trap us in a regime of northerly winds with a stalled trough over Scandinavia persisting for a large part of the month.

This was actually due in large part to a second Atlantic trough phasing with ex-Bertha as the system tried to clear away to the NE of the UK. Without that, the ridge in the Atlantic would have most likely ended up more or less over the UK, with near average temperatures and little rain. That's British weather for you!

http://max.nwstatic.co.uk/ecmimages/20140826/12/ecmt850.120.png

This time around, we have the same sort of process, but taking place a lot further west. Ex-Bertha tracked right through the UK, while ex-Cristobal is headed towards Iceland. 

http://max.nwstatic.co.uk/ecmimages/20140826/12/ecmt850.168.png

Currently, both ECM and GFS show a second Atlantic trough failing to phase with ex-Cristobal. The systems may not be all that far apart, but with the main opportunity for that now at the 5-6 day range, it would take an unusually large adjustment to change the result - still something to watch out for though. I think if it happened, the result would be a stalled trough either to our NW or N, though I'm not sure about that to be honest.

As things stand, ex-Cristobal is able to track towards Siberia without too much trouble - though doesn't quite make it on the ECM run - and the amplified jet is represented by the 'left behind' Atlantic trough digging south and the UK ridge building north. At the moment, the jet looks weak enough after Cristobal's passage to allow the UK ridge to sit around without being displaced by trough development across Europe, but that's by no means a certain thing.

Look at the jet stream and its relation to cristobal (see http://max.nwstatic.co.uk/gfsimages/gfs.20140826/18/90/airpressure.png ) , this is what I'm worried about.

http://max.nwstatic.co.uk/gfsimages/gfs.20140826/18/90/hgt300.png

There is scope for explosive development of a secondary low here. Cristobal is already unusual in that despite being tropical it has what look like frontal systems, if its cold front interacts with this jet, then a secondary low could develop extremely quickly due to the high levels of divergence in the upper atmosphere. The secondary low, if it does form would be on a direct course for the UK.