An Azores Low is bound to cause a lot of uncertainty. Usually the models go too far with the conditions for intensification when it's beyond +120 hours away but of course there will always be some that do bomb out.

I remember in late Nov 2010 there was a time when a lot of ensemble members developed large LP to the SW and shoved the cold air away.

Usually, any large trough to the SW will be perturbed by the cold to a great enough extent that a secondary low develops on its NE flank and breaks away E or NE. I reckon the most likely outcome is either that sort of thing or the main low remaining smaller and moving NE in its entirety, much as the ECM 00z does but perhaps not developing as fast (i.e. as far SW from the UK). Both have similar implications for the UK, with a marked warm sector meaning mostly rain for an unlucky number, a snow-rain-snow or rain-snow event for a great many others, and a mostly snow event for the lucky few.

Having said all that, if the weak secondary low shown to the west of the UK in the below-left image doesn't develop or at least is a lot smaller, the door is likely to be shut in the face of that Azores low until a few days later in time. That's the best way forward IMO, as it allows the cold air to become better entrenched ahead of the potential intrusion.

The secondary low is still far enough away in time to be subject to a lot of uncertainty - after all, ECM's the soonest to develop it out of the morning op runs. GFS has no such feature even out to +216, with the Azores Low still trapped by the so-named Islands. The movement NE takes until lower-res, at which point you may as well ask a 3 year old how it will behave.

Yes. The great thing is that the spikes up to 12C at 144 hrs-plus represent no more than five of the 50 ensemble runs. Ninety percent of the runs keep the max. at no more than 3-5C for the whole 10 days!

Ian F on Twitter:

@fergieweather: indeed, albeit we do nonetheless have good confidence on the colder story, irrespective of potency/longevity/ etc etc

And his view on last night's GFS 18Z:

@fergieweather: ...but my hunch is it probably returns mobility too easily. Often an issue in these situations. But hey-ho, time will tell!

And just posted, ECM ensembles for Bristol: https://twitter.com/fergieweather/status/685032638294429696

^ a whole week with median max below 5C. Doesn't look like mega cold but certainly a welcome change!

When Fergusson goes public with "Brrr!" for my back yard, I start to BELIEVE.

PS Love that he give us a peek at another ECM ensemble. If only that diagram were routinely available.

Edit: Even at day 14 the median max is 4C. Which means in a fortnight's time 24 out of 50 ECM runs show a max BELOW 4C, even for down here.

I don't know what the MetO have been seeing, but from the output we have access to, I can't at the moment see a quick return to an atlantic dominated pattern anytiime soon. Certainly not anything along the lines of what we've been used to for the last two months.

Well neither can I from the output shown. Good news that Ian F has said what he has; as the current METO update for next week remains WORSE than the GFS 18z last night !

i expect that to change considerably today.  Going on JH on the week ahead forecast on the BEEB last night, and based on snippets of other Meto information, it just doesn't tie in with the story they are pumping out on the Metoffice website.

And the coldest run appears to be have a max of below -5C right at the end! 

Still looking ok.........................to me

Until we get to all that cold stuff next week, I've been keeping an eye on that cheeky Channel low progged for Sunday night/Monday morning and it's still there on the 6z GFS, just a few hours earlier making it a night time event (it is also showing up on the other models but to a lesser extent so this could still be an outlier).



I still think/hope the gustiness is likely to be kept over the French side as the strongest wind tend to be to the south of such a feature. Also I can't see any surprise "early" snow out of this as it has a warm sector in the mix (left over from it's birth place over the Gulf?), and the -3 C 850's to the north of that "micro" low (I've seen MCS bigger than that!) is not good enough for snow production. Will have to wait until the middle part of next week before I go into snow ramp mode for my area - and that is still a long way off in forecasting terms.

A lot of water to pass under the bridge until then - as so to speak.

http://modeles.meteociel.fr/modeles/gfs/runs/2016010706/gfs-0-174.png?6

Ironically GFS 06z becomes similar to the ECM at the same timeframe, though it hasn't developed the trough in the Azores !