I wonder how long that would have to persist before it started sending cold air in our direction.

Until today’s GFS run would have been a start? 

All but into the 5-day 'reliable' forecast period and anything could happen on Sunday and after as ex-hurricanes get a move on across the Atlantic.

GFS0z - intense depression off NW Scotland at T+144 (Mon) continuing to move NE

ECM - Less intense depression but over central England at T+168 (Tue) and heading off SE to Med

MetO - Weather for the week ahead last night flatly refused to forecast anything! But the forecast they offer for Chichester shows the summary for Sunday as wet but with hour-by hour chance of rain at 10%. Fax however at T+120 shows a line of southerly tracking lows with Maria bringing up the rear for later.

Interesting times!

I'm running in the Cardiff Half Marathon this weekend and I've been watching the weather for Sunday for the last few days and it has varied wildly from dry and calm to heavy rain and wind. Currently, the Metoffice 7 dayer is showing mainly dry but a 20% chance of rain which is, oddly, in contrast to Chichester's lower percentage of rain but wet. It's clearly one of those times when it will be a nowcast on the day.

Sunday still up for grabs. ECM has (reluctantly?) joiined in with GFS in developing a storm for the NW out of the remnants of Maria, but Fax and the MetO 7-dayer suggesting a lot more rain across the south. NHC agrees, placing storm Maria just off SW Ireland on Sunday (now there's a naming anomaly for Neil)

http://www.nhc.noaa.gov/graphics_at5.shtml?cone#contents

Lee hadn't been updated to Sunday at time of writing but may well get to cat3 status before being swallowed by Maria.

The local MetO forecast for Chichester has gone from no rain(<10%) for Sunday to heavy rain all day (>80% 1000 - 1900) in the space of a day. I'd back that outcome.

👍 I reckon secretly the UKMO is hoping the system doesn't meet their 'naming criteria' as it will be a bit complicated. 'Brian' is next on their list but what do you call a low that has ex-tropical characteristics born from the remnants of Maria and Lee?

I'm guessing 'Storm Brian derived from the remnants of a non-synchronous post-transitional fusion of ex-Hurricanes Maria and Lee' doesn't flow very well does it? 😂

That's something that's still being considered apparently. When the named storms scheme was first thought up, I believe it was decided that all tropical remnants would keep their hurricane name. It's not something I'mm too fond of, as it will completely mess our named system up.

Hopefully however, they end up naming it as per their system.

If Maria marries Lee, why shouldn't they have a son called Brian? Though it rather looks as if Maria is taking the role of the female spider and swallowing Lee whole.

It looks very Unsettled for Sunday and Monday and a ridge improves our Weather for Tuesday and Wednesday next week.

There is some rain in today and next 48 hours after midnight a.m. Thursday.  Saturday looks fine and settled for many.

And for the NW and North UK more Westerly winds SW to NW flow from about Wednesday and Thursday next week, at that time the SW and SE and S UK parts should see higher pressure from retreating ridge of High P. where dry and mild weather should return. 

A prolonged spell of heavy rain on Sunday and Monday early and late is possible and expected, heavy blustery showers for many with some gales and severe gales looking quite a possible forecast as via the GFS and UKMO, the ECMWF is backing these two up very well indeed, Sunday very warm and humid, or mild.  Chilly NW winds on this coming Monday.😆🔚🔎🌎.

That Atlantic low takes over both Maria and Lee The fax charts, 

https://www.theweatheroutlook.com/twodata/datmdlout.aspx

which are the ones I would trust at this stage, look as if the north will get enhanced wind (though nothing more than an average autumn gale) and the south will get the extra rain

Tricky temperature details within a relatively easy broader-scale setup developing next week; deep troughs near Greenland look very likely to throw a lot of warm air across N. Europe and Scandinavia at the upper levels, which then slows and takes on a general sinking tendency, promoting extensive high pressure for those regions. A 'Scuero High' as some call it - and something seen all too often mid-late last winter in place of the more effective (for wintry weather) standalone Scandinavian Highs. 

As it is, we're in mid-autumn and so the exact positioning and orientation of the extended ridge will make the difference between an 'Indian Summer' (this now being technically applicable following frosts in some spots earlier this month) and a run of very cool nights and fresh but still potentially very pleasant days (depending on how much of a breeze there is).

Either way, good odds on abundant dry weather which will be a welcome relief for many after a generally damp (in SE) to soaking wet (in N, particularly NW) Aug-Sep period. Assuming, that is, that some ex-tropical feature doesn't come along and upset the whole pattern again...!