Exactly - we had a negative NAo during the summer months and all 3 months were above average and July was well above average!

Back to the models - the ECM at +216 and +240: - This could be a snow event?

Cold air coming in from the north east and uppers of -10@ 850hpa to ]north and most of country under sub -5c @ 850hpa. and a front coming in from the SW!?>

+216

+240

Too far off to be anything other than speculative, but shades of 2014 beginning to appear? Seen several charts like this one recently with "afterburners" beginning to fire up.

yes rubbish in the long term.Who cares if the minus 10 line comes in,it all be over in 24 hours.

A poor outlook for cold fans, if the gfs is correct,

Yes, you remind people every year, and quite rightly given the huge amount of ECM data available there.

As for temperature scale, it’s not difficult to convert: F minus 32 x 5/9

To be accurate you mean if the GFS OP is correct.  Once you get more than a few days out the professionals look at the mean and clusters and so should we.

GFS control

Hopefully will end up further west that currently modelled. Looks awful for canvassing. Who wanted a Dec election?

Control will please Steve

06z ensembles for London:

One or two ensembles want to keep this cold snap going from 2nd Dec:

Precipitation spike on 10th Dec:

Yes a really horrific run post day 9 with a deep PV and strongly +ve AO/NAO combo, backed up by many of the ensembles.

GEFS 06z extend the cold snap but there is still a cluster bringing back milder air quickly.

Indeed! Good for now and good thing is that next weekend if will feel more seasonal and the colder spell and intensified! Several ensembles want the keep it cold longer:

P 1 - Cold and frosty daytime maxes at or just above freezing at midday. 

P 10  -A gentle easterly.

P 11: - Battle ground with sub -10 @ 850hpa to our north.

P 13 - The coldest with -10c @ 850hpa giving us a northerly!

P 15 - Tries to build HP over Scandinavia giving us an easterly!

I still cant believe after what now 14 years on the forum you still haven't fathomed out how a model works especially the GFS.

For 3 days you have been saying the 10 day mean looks horrific - yet if day 1 was 10 day then day 3 should be day 7. Ergo your horrific charts arent getting closer-

This dovetails with the fact that we started out with no sub -6 days then late yesterday transitioned to -8 days & now are flirting with -10c days - With that in mind it doesn't take Sherlock Holmes to deduce that when we max out on uppers - the length of the cold spell will extend as well because your mild synoptics are still stuck at day 10.

How about this headline - 06z Sat GFS ENS mean had london at +8c for around 03rd December- My forecast ( conservative ) will be -6c - Thats a 14 Degree swing to cold all because of model bias.

Just for one season instead of blindly following the GFS at least observe the full model picture.

I fear the milder air will wind and wetter weather will return but at least it gives us some hope of ate least the possibility of the colder snap holding on and becoming a cold spell - albeit a very slim one.

One or two rather cold days at the end of Nov beginning of Dec is normal fair if it even comes to that. We have seen enough times already this Autumn how an amplified pattern at t168 flattens out by the time you get to t72. This may have legs and stay the course but t144 -168 is at the extreme limit of reliability. 

Many times now we have seen this micro analysis of model output for colder options than what the models are actually showing by one or two  posters especlally  when it comes to continental flow ( east/ northeasterlies) and it has come to diddly squat which had been the general concensus of most of the other posters at the time. As I say lets hope this one has legs.

devils advocate is good - not downright ignore :)

UKMO wasn't great so lets see how that lands on the 12z

But the trending thus far has been great !

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao_index_mrf.shtml

no denying that or reason to be chastised for pointing it out.

As a general observation this is fine but I’ve not seen anyone commenting on something that’s not in the model output - have you?   There has been perhaps more emphasis on the GFS trending towards a sharper cold spell but nothing more.  The ensembles - both GFS and ECM - have a clear signal for it to turn milder but we’ve all seen the ensembles flip just as much as the operational, so I would emphasise the uncertainty after a short, not unusual, cold spell.

Exactly - and worth repeating that the NAO predictions are just a function of the GFS output, AFAIK.