Ben Sainsbury

And as these observations are fed into model through data assimilation. This is where a few people were talking before; because the Arctic is so observation-sparse, we really don't know the state of the atmosphere until the airmass makes it in range.

Just for fun, but after T384 it looks like another Scandi high developing, I think

Quite the opposite imo. If the GFS is anything to go by, the polar vortex is all over the shop and away from Greenland/Canada, which is the most important thing!

Purely for fun at this point, but what's that like a 980hPa low deepening well within the Arctic Circle at T318??

This is because the Norwegian/North Seas are both relatively mild (given the time of year & above average SSTs). So through the process of convection, heat is carried up through the atmosphere, leading then to modification of the air, which in this case making the airmass a little less cold.

By T192, here we go! Could be best run of the winter this. Some pretty significant WAA towards Greenland now too.

Absolute corker. Beginning to develop our own cold pool over the UK with the slack low overhead. Can see it since 850s aren't mixing out.

Not sure anyone can complain at tonights GFS run. The whole of the UK basically remains under -5C 850s throughout the entire run, let's ignore its outlandish path to getting there ey? Oh and to top it off, blizzard over Southern England at T360...

It definitely does form from a tropical wave, but judging by the runs today it doesn't look like it really deepens much until it approaches much closer to the UK, probably more akin to sub-tropical rather than tropical. That's my mistake.

I was just going to say, if that low can get a bit of a move on then that's very large part of the vortex to our NE.

It's still 7 days away yet, I wouldn't stress too much!

Looks a lot better over N Europe/Asia then the 00z. Low does have a bit more of a negative tilt too, but maybe just my positive thinking!

Hahaha, that's a name I haven't heard in a while and Exacta Weather too! Might need their old enthusiasm if the models take a turn for the worst tonight! Admittedly, I can't see that happening and I do expect the dartboard low to begin to ease off over the next few models runs, but still!

The GEFS definitely isn't as good towards the end of the period, but when was the last time the models were spot on about a potential breakdown (before it's even started), 9-10 days out? There was no interest in a breakdown 2 days ago, give it another 2 days and the ensembles will probably veer the other way. That's not to say it's not for discussion though, that's what this forum is for, discussing all possibilities!

EC 12z is on the cusp of something special here, if the low drops a bit further SE.

And in theory assuming this "battleground" snow-event happens, the low will bring a lot of tropical moisture up towards the UK, which would result in some extraordinary accumulations of snow. BUT this is merely speculation at this point, just for the fun of it.

Agree with you, very likely here to go onto a battleground event over the UK. You can already see another N'ly beginning to line itself up.

That blow-up low on the ICON 12z & GFS 6z is definitely a tropical system. Obvious warm core on the models, but I just cannot see it strengthening/deepening like it does.

It's almost as if the deterministic models have flipped back today (oops) as the low dropping towards the UK slows down and stays just to the east, therefore avoiding a west based -NAO . Personally (factoring in my S England bias), I'd be very happy if the weather plays out as the models show today. I think almost all areas are at risk of seeing some snow at some point, with some heavier falls likely with any troughs/small-scale lows that develop in the flow. Overtime, you'd like to think the airmass will slowly get colder with the slack winds and consistent flow from the NE, so ice days possible going forward. Confidence is growing!

One thing to remember as a few have pointed out before, is that none of the big cold spells in recent decades have occurred without chopping & changing/having wobbles (BFTE 2018 & Dec 2010 inc). So it's inevitable we're going to see changes especially at this range. Often in the mid-range, models can drop the idea of something... only to bring it back again the following day. I wouldn't be surprised if models flipped back tomorrow to what they were showing yesterday.

I understand some people like to "over-compensate" with regards to 850s when talking about snow potential. But really as long as 850s are within the ballpark of around -5C then there's nowt to worry about at this stage, even if you live Southern England. There are a ton of cases where 850s are -2/-3C and many places see snow. It's not until 48 hours out or so where we can really look into the real ingredients for snow potential. i.e. wind direction/speed, boundary layer cooling, dewpoints, thicknesses etc.

Nicely done here, with some of the fundamentals regarding the main driving forces of our weather. If any/many of you find some of these definitions/phrases overwhelming, I'm a forecaster and I don't really understand half the things on here! But all of these definitions definitely provide a good basis, if understood, to interpret forecast models. @Eagle Eye I always admire your passion! Back to the models, ICON 12z following a similar theme as the GFS/EC, although maybe delaying the cold a touch.

Meteorologically, we're only just heading into the very start of winter and in recent years, December has been deprived of any decent cold. So if we can get anything wintry within the mid-range then I take that as a bonus! Judging by the ensembles, a mean close to -5C at 850hPa is actually pretty decent for this time of year.

This is exceptional footage of large rotation and resulting tornado/waterspout IMO, good job. Have referred your comment to Torro.

Looks like I'm out chasing after all, heading Reigate or Sevenoaks region. Conditions are better this morning than I had expected.