kold weather

Big difference is they are far more keen to keep the low towards the SE rather than swinging it up through England, means a great many more runs pull in colder air again behind, a few tight enough to probably cause a rain-snow event even in the far south. Most runs have a big snow event somewhere, has to be said mainly wet for the south mind you until some pull colder air back in. Then it becomes a roulette again with the hopes of slider lows/Scandi wedges. Quite a plausible evolution imom

Despite a rough start the 18z run goes onto to become a bit of a classic. Goes to show what better upper synoptic can do in the long run if we luck out.

Terrible run for the south in *semi* realustic timeframe, but more than passable further north. Considering how rough it looked at 144hrs though the GFS ends up making a still decent pattern with disrupting lows. Snow-cover would hang around a while I'd say in such a pattern for central areas and maybe get very cold there.

The ECM is full snow for basically everyone other than maybe the exact coast.

Its definately on the more extreme end of the solution range, but the trend has been to make it ever more knife edge even on the runs that do make it. Still plenty of scope though for cold and a snow event, especially further north you are.

To be fair even the far south would have a fairly substantial snow-rain event with that evolution.

A big heatwave of course could hit through there, I think the big difference though between Paris and other locations that have held the olympics (Brazil, Japan, etc) is the humidity that comes with the other locations. Paris undoubtably can go very hot, but it will rarely if ever be able to match the heat index of a peak summer heatwave of Tokyo or Rio, etc. Thats where the real danger is, the combo of both high heat AND high humidity.

I've got a feeling how you read the ensembles will vary depending on where you are. For further north they are still rock solid, and in many cases actually very snowy. Further south, and its about as mixed a picture as you could get, could be snowy, could be flooding type rains given how wet the last 6 weeks have been down here. Regardless, the margins here are small to begin with. In some respects @Met4Cast is correct, the broadscale pattern isn't that different, but when you really drill into the last few suites and look at the trend of the individual runs, you will see the pattern has morphed into an all or nothing type pattern for many. Also, regardless of where it lands, think there is a high chance somewhere will get a notable snowfall out of this at some point providing the models aren't very wrong about the upper high strength to our N/NW.

Right at the tail end of the meaningful snowfall streamer here, not heavy enough to settle but it is a pretty sight to be fair if nothing else. I'd have loved to have been back in SW Essex, looks like they got a couple of hours of moderate snowfall earlier, though I'd imagine it won't be settling that well outside of the heavy bursts.

They've been in a bit of a cold spot for the last few months it seems, bodes well for us as we progress through the winter and the El Nino starts to weaken along with the usual improvements seen through 2nd half of El nino winters.

Starts as snow then would transition to rain and melt it all away for far south where you are. You'd want a weaker low and maybe a little south still.

I totally understand the worry and some are being very dismissive of it this morning. That pattern needs to shift only a fraction north and its going to be a close but no cigar for at least 50% of the populace of the country. We literally *just* get away with it on several models. Again I'd personally want a stronger pattern, get the cold in *then* relax into a LP attack rather than just skip the first stage and hope the cold even makes it in the first place. As it is though most runs are still very interesting, if as others have said, risking incursions of warmer air into the south.

Absolutely an upgrade from 00z ECM, I don't think there is much of a question there. Anyways we have tomorrow first to keep an eye on, think there maybe quite alot of snow showers around tomorrow, even if relatively little actually accumulates.

Absolutely fascinating 12z ECM, synoptically at the end is just fascinating, because you've got an upper low driving SW near Iceland (and will probably form a surface low near Iceland further beyond) but the arctic high and the small upper high over SW Greenland influence each other and are actually rotating around a central point near the center of Greenland, which will mean even if a surface low does form near Iceland its all going to be ejected SE towards the UK anyways. Depending on how much development there was of the low, could evolve into a very snowy pattern...but if it overforms, a pretty rainy one before it moves away. Anyways, it probably won't look anything like that so not sure why I'm overanalysing it!

I think thats also a fair point. sometimes when looking at all the eye candy and then you see something not so good its easy to lose heart. In truth most runs from the GFS ensembles will be cold through to day 10, and sure, most aren't as good as what some of the other models are trying to do but there is probably only a couple that I'd describe as being outright 'bad', most have at least some redeeming elements to them.

As long as we can keep the Arctic high in place to some extent we are always going to be in with a shout that it forces things more favourably for us, I suppose as a veteran of 20 years now I'm a little battle weary when it comes to Arctic highs playing a good role, I've literally seen it a handful of times work out (of course when it does, it tends to make things very tasty). Either way, the models tonight are overall very good still, and if the worst case is a frosty high, then compared to the last month I'll gladly accept it.

GFS ensembles are a mixed bag for sure, some great runs, some real stinkers. 12z control is pretty rough looking out to 192hrs, though probably still going to be fairly cold at the surface for a time as the HP sticks nearby. Indeed HP nearby would be the theme if I had to sum the 12z GFS ensembles, cold but dry with HP nearby and Arctic profile flushing down the toilet on a great many by day 8-9.

Thats the thing of course, I don't want us to have to rely on an Arctic high to help get the job done, fickle beasts that are often poorly modelled. I'd rather the Atlantic profile was good enough to get the job done first time, even if it does mean to start with its a lower risk of big snowfalls.

Its fine as it comes, my main concern is the evolution it shows may easily morph into a close but no cigar type situation. I'd personally perfer any other model thats come out tonight over it, even if it does end up coming good in terms of deeper cold.

The GFS goes quite a hairy route (particularly for the south, I'd not fancy our chances of even getting in the cold in such an evolution tbh) however it just about gets the cold air in. Once it does get in the pattern in the Atlantic is actually pretty decent, solid ridge right into Greenland with the PV lobes being in a decent position to keep things locked in place despite relative lack of heights. All runs so far range from decent to excellent, the GFS might be the worst within 240hrs but its still acceptable in the end.

These are pretty classic high risk high reward type situations. Obviously if it does end up too far west we at best get some limpet cold coming in briefly like a washed up celebrity on a reality TV show. If we are lucky and the high is just right, we get the real McCoy.

Yeah, besides it literally is just one op and there are a range of better options for long term cold. As ever it's a wait and see situation. At lest we will be living the very wet weather for a little while

Unfortunately everything is going to go in the opposite way, the upper high moves west and the LP complex SW as it ejects around the upper high over Greenland.

In my opinion the ECM 00z may not be a technical west based -ve NAO at 240hrs but clearly transitioning that way and as others have said its a dreadful orientation. There will still be some cold in that evolution, but its probably the least impressive solution you could arrive at given such strong foundations to begin with, and the south will probably barely get into the cold full stop in that evolution. Most likely solution from 00z ECM is cold upper pool ejects SW and develops new low, which may briefly drag in limpet N/NE winds before being replaced by SW around the new low.

Yeah the big difference maker is the UK tends to get 1-3mm/per hour type rainfall that can go on for a good 6-12hrs without much of a break, Rome and other more subtropical style locations are capable of getting convective masses that drop 30-50mm+ in shorter time periods. So we probably have fare more 'rainfall hours' than places like Rome, but our rain is generally much less intense so Rome still ends up wetter in terms of overall statistics, even if they are getting what feels like far less rain due to rainfall hours being lower.