12Z ICON trends the NYD low a bit shallower and south. 

Chances of a snow event central areas increasing. 

Originally Posted by: nsrobins 

It also manages to bring damaging winds across most of England and Wales, an atrocious run. I still think people are focusing too much on snow and not enough on the very real potential for a nasty storm! Here are the peak wind speeds by the end of New Year's Day - the deep burgundy is 62mph or higher in terms of gusts.

https://images.meteociel.fr/im/78/20868/iconeu_uk1_52_108_0uht9.png 

Originally Posted by: Retron 

Sorry but 62mph gust is a winters fart for most away from inland areas whereas a chance of snow 🌨️ ❄️ well that is something to look forward to.

Originally Posted by: picturesareme 

Support in the cluster for decent cold spell starting. Obviously could go wrong but this is what is exciting knowing before others! Just don’t mention it 

Originally Posted by: ballamar 

Happy days for cold weather fans if GFS 12Z is correct. In fact, if this is how things pan out it would probably be one of the most amazing winter u turns in the recorded history of UK weather. A sub zero January CET wouldn't be out of the question.

Originally Posted by: Brian Gaze 

Lots of people are on it already I can assure you. 😂😂😂

Originally Posted by: Brian Gaze 

I think the old saying of "Expect the unexpected" is sometimes quite apt with the British weather, Brian.

For instance, if someone had said to me back in November 2009 during the wet, wild and mild weather that dominated that month that a month-long freeze would be starting shortly before Christmas that year, I wouldn't have believed them. IIRC when the models began to pick up on the beginnings of that spell, they did so almost all at once and then stuck rigidly with it. The same things happened in the lead-up to the December 2010 freeze to if my memory serves me well.

Originally Posted by: David M Porter 

2009 was spotted around 10 days in advance by GEFS - first as a couple of stragglers, then gradually more and more members followed suit.

2010 was similar, GEFS started to cotton on around 10 days out, and unlike 2009 once it picked up on it there was far less scatter.

2010 was also spotted a good month in advance by GLOSEA, I remember the MetO long-range text forecast being very bullish on it throughout... more bullish than they've ever been at that range since!

Here's a snapshot of the GEFS just as the autumn/winter 2010 cold spell was kicking off down here. It's interesting to compare it to the current output...

(And FWIW it persisted in trying to return to normality throughout the cold spell, there weren't any days when it was showing cold throughout the run!)

https://ukwct.org.uk/weather/2010/ens.png 

Originally Posted by: Retron 

Wasn’t Dec 10 primarily due to an SSW in the right place etc?

Originally Posted by: ballamar 

2009 was spotted around 10 days in advance by GEFS - first as a couple of stragglers, then gradually more and more members followed suit.

2010 was similar, GEFS started to cotton on around 10 days out, and unlike 2009 once it picked up on it there was far less scatter.

2010 was also spotted a good month in advance by GLOSEA, I remember the MetO long-range text forecast being very bullish on it throughout... more bullish than they've ever been at that range since!

Here's a snapshot of the GEFS just as the autumn/winter 2010 cold spell was kicking off down here. It's interesting to compare it to the current output...

(And FWIW it persisted in trying to return to normality throughout the cold spell, there weren't any days when it was showing cold throughout the run!)

https://ukwct.org.uk/weather/2010/ens.png 

Originally Posted by: Retron 

Interesting.  Do you happen to recall, for December 2010, did GEFS get steadily better (from around 10 days out), or were there a few hiccups over the 10 days?

The reason I’m asking is that it feels a bit like that at the moment.  Specifically for “Inverness”, there started to be a 7+ day sub- -5° 850hPa in the 00z and 006z runs on the 25th.  It then rowed back on that for a couple of days but, as of 12z yesterday, started to look rather promising again.  It will be interesting to see if it continues to solidify, although I dare say that the precise tracks of the lows on the 31st and 1st/2nd may continue to move around a bit ….

Originally Posted by: ABainbridge 

There wasn't a "proper" SSW, i.e. a reversal - there had been one earlier in the year (following on from the cold start to the year) and the next one was in 2013 (which led to a cold spell).

https://www.researchgate.net/figure/List-of-the-Major-SSW-Events-Recorded-Between-1958-and-2013-Peak-lunar-tidal-Peak-ZMZW_tbl1_324608809 

In 2010 we had repeated pushes of warm air up the west side of Greenland, which is the classic way to start a cold spell. As for what caused those to happen, I honestly couldn't say, but I remember the GFS in particular modelled it well. Presumably GLOSEA3 modelled it well too, further in advance, which led to the MetO's bullish long-ranger. I know at the time GLOSEA3, unavailable to us mere mortals, was regarded as an almost mythic model!

It's never had such an impact since.

Originally Posted by: Retron 

There were hiccups, but that was more because the WZ charts kept messing up! Here's an animation of the end of November's charts, minus a couple where WZ went haywire (one with green lines all over, one with just the op run and nothing else).

It'll be an interesting comparison with the current output.

https://i.postimg.cc/52wFQ8Bq/ani.gif 

Originally Posted by: Retron 

2009 was spotted around 10 days in advance by GEFS - first as a couple of stragglers, then gradually more and more members followed suit.

2010 was similar, GEFS started to cotton on around 10 days out, and unlike 2009 once it picked up on it there was far less scatter.

2010 was also spotted a good month in advance by GLOSEA, I remember the MetO long-range text forecast being very bullish on it throughout... more bullish than they've ever been at that range since!

Here's a snapshot of the GEFS just as the autumn/winter 2010 cold spell was kicking off down here. It's interesting to compare it to the current output...

(And FWIW it persisted in trying to return to normality throughout the cold spell, there weren't any days when it was showing cold throughout the run!)

https://ukwct.org.uk/weather/2010/ens.png 

Originally Posted by: Retron 

There wasn't a "proper" SSW, i.e. a reversal - there had been one earlier in the year (following on from the cold start to the year) and the next one was in 2013 (which led to a cold spell).

https://www.researchgate.net/figure/List-of-the-Major-SSW-Events-Recorded-Between-1958-and-2013-Peak-lunar-tidal-Peak-ZMZW_tbl1_324608809 

In 2010 we had repeated pushes of warm air up the west side of Greenland, which is the classic way to start a cold spell. As for what caused those to happen, I honestly couldn't say, but I remember the GFS in particular modelled it well. Presumably GLOSEA3 modelled it well too, further in advance, which led to the MetO's bullish long-ranger. I know at the time GLOSEA3, unavailable to us mere mortals, was regarded as an almost mythic model!

It's never had such an impact since.

Originally Posted by: Retron