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 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 

Given the zonal winds are so strong at 10hpa, it's unusual to see the models go cold is it not? and it looks like the zonal flow will go record breakingly strong in the news few days yet again? There must be a Decoupling...would you agree!? I don't have access to the NAO but if anyone has access to it how is it looking? I can only see it on gavsweathervids? thanks

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.gefs.sprd2.png

ECM 12Z @ 240z shows -10c uppers just by the east coast on 7th midday:

Wind-chill would make it brutally cold if this came off esp in the south in this still easterly winds and temps around the 0 to +2c mark!? - Will it bring any snow with it though?? - time will tell and it's not often we get upgrades in cold weather re computer models. All eyes on 18z now i guess?

https://www.theweatheroutlook.com/charts/ecm/12_240_mslp850uk.png 

Originally Posted by: tallyho_83 

What’s more striking is the depth and longevity of the AO index:

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml 

Originally Posted by: White Meadows 

18z GFS op run shows at least 3 if not 4 snowfall events in the south from channel lows pushing up and eastwards and stalling/stagnating. The low on 2nd but depends on tracking of it, BUT 4th & again on 5th shows snow, followed by easterly winds and channel low to form and bring snow to the south on 6 and 7th and another channel low on 9th to 11th bringing heavy snow to the south. I looked at the ENS briefly and the OP is a mild outlier between 4th -8th! wow! As for the OP it shows daytime maxes still at or just a smidge above freezing by 13th January and that's a long way off now but goodness me! - The 18z control run plunges the UK into the freezer!

I would be gutted if not one came off despite all that. On the plus side we are seeing upgrades in the cold each run and the positioning of the low is crucial. Timings are almost nailed on but the positioning isn't it could take a southerly track or more northerly. Very interesting times ahead!

The caveat is that NE America are expecting a cold spell as well and usually we all know what this means for the UK, so i will remain cautious until Monday at least. It could all go Pete tong! We have been here before but I can't remember seeing such cold blocked charts in January for several years and even then they have not always verified, so I am remaining cautious!

Originally Posted by: tallyho_83 

You’d be gutted if not one came off? None have been showing at all like this, prior to this. I haven’t looked at the ens, but I’d imagine this projection has little support from its own model let alone other models. Maybe it has….

Originally Posted by: Matty H 

Just a shame that there is that spell of stormy winds over a large swathe of Southern England on New Year's Day to get through first, 

Originally Posted by: idj20