Strong El Nino events tend to encourage westerlies to dominate the UK winter. Usually there's more of a northwesterly influence Nov-Dec but this particular event has been producing patterns more like we'd expect to see in Jan-Feb, as if the atmospheric responses are a month or two ahead of what's been typical with past events.

The thing is, these events also significantly raise the probability of a major stratospheric warming event, and one situated in the right sort of place to bring a colder period to the UK during the latter stages of the winter. Hence the analogues for such events are divided in late winter between mild (often very mild) and significantly cold. We see a similar divide among the strongest two events of the last 50 years; 1982-83 saw cold spells of some note Jan-Feb, yet 1997-98 was exceptionally mild in Jan-Feb... well, mostly Feb but the point stands.

This year though, we have a strongly westerly QBO which has allowed the strat. vortex to reach record cold levels as of early December. So it's going to take something special - and frankly unusual for a westerly QBO winter with average to low solar activity - to achieve a major warming event and change the game. We have feedbacks from snow cover advance across Asia coming along nicely so that helps, but really it's too finely balanced to make a call yet.

This truly is, IMO, an 'all or nothing' type winter. 

In the meantime, we have a significant modelling problem. You see, tropical convection has managed to become active yet poorly defined; it's spread out across much of the globe's tropical waters. I've read some posts recently that suggest this is tricking the models into seeing pulses of MJO activity when in fact there is none, and having found the usual MJO plots to be blank for a number of days now, I'm starting to believe this is true (http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ALL_emean_phase_full.gif)

The ramifications are large; the models will show false tendencies - moving toward certain large scale patterns which are actually red herrings. This may explain the recent tendency for the output to venture in interesting directions only to 'revert to type' and produce something more akin to the 'advanced El Nino' setup that has been so dominant of late.

A cold snap or two is still achievable this month though, as occasionally convection is likely to become organised enough to trigger wave amplification i.e. ridges extending further north and troughs further south, with the jet meandering more sharply as well. The trick is having a wave come along when the pattern is aligned correctly to bring a cold plunge our way rather than balmy southerlies.

We are seeing such an issue for Friday this week, with the models having generally trended toward there being a mid-Atlantic trough during the amplifying phase as opposed to a Scandi trough. However a complication has emerged in that the mid-Atlantic trough originates far south enough that it may allow for a mid-Atlantic ridge to the N and E of it. This can only happen if the trough doesn't engage with the polar jet before Friday. UKMO does just that - hence no mid-Atlantic ridge - but it's the odd one out, with the majority vote in favour of the trough staying independent of the polar jet for long enough to allow that mid-Atlantic ridge to develop and provide a cooler, drier interlude which will be much welcomed by many if it verifies.

Hopefully UKMO truly is barking up the wrong tree as it's solution would continue to drench those areas that have been hit so hard by the exceptional rains over the past 48 hours.

The strength of this El Nino has always been my major worry... A lot of the analogues and things were pointing towards some late winter cold but this El Nino is a monster with very few other years to connect it to...

Or is timing or buildup a factor.

It's very complicated.

El Nino's do seem to coincide with a more zonal November/December period and more blocking in the latter winter months/March.

What concerns me is the constant outpouring of cold air into the mid Atlantic and lack of blocking around Greenland. We have had a consistent SW wind influence since late October now and it has been quite unusual. Has anyone also seen the global temperature anomalies for the coming week? Their pretty remarkable, with the warmth across Canada particularly extreme.

For me this winter has been in a lot of ways similar to how 1994/95 started, we can only hope that it doesn't go down that route for the rest of it. In 2009/10 we got a slowing down of the AMOC, but I don't know if that will occur this year.

As I say this winter has a lot of parallels with 97/98 and 94/95. The extreme El Nino of 82/83 also had a very zonal November-January period but February 1983 was much more interesting.

The only other El Nino on the same magnitude as this 1997 and 1982 was 1877 and the following winter was poor. Lets hope this winter we have a bit more luck!

thanks darren as always an unbiased informative post.

Another ECM day 10 chart full of snowy possibilities . We need the ECM to show this sort of thing at day 5 though. Better GFS ensembles this morning as well so a step forward today.

http://www.wetterzentrale.de/pics/Recm2401.html

Looking across the pond, GFS 0Z has the 564 line as far north as the southern border of Maine next Sunday!

That should be good for us. It always seems to me that we need mild on the eastern seaboard to get cold on our side of the Atlantic. Perhaps you can dig out years when both the eastern States and the UK were in the freezer simultaneously, but I would wager that such events are very rare.

I would have thought two polar vortices with a Greenland omega block in between is where the NE of North America and this side of the Atlantic could have a simultaneous cold snap or spell?

 ECM not supported by GEFS 0h,which  has a split mild:cold 60:40 at 240h and 70:30 at 360h.So still little sign of any significant cold event.

Sadly the ECM ensembles are also shocking for cold these are as bad as I've seen for at least a week. 

http://www.knmi.nl/nederland-nu/weer/waarschuwingen-en-verwachtingen/ensemble-verwachting-detail

Your right Solar Cycles.Although numbers of years are small the strongest El Ninos >1.5 are strongly biased towards  NAO + winters.However further analysis by month shows that although December  and  January are generally NAO +, February's of these years are more likely to be NAO -.

The answer is simple SC

Strong El Nino = UK dismal, mild winter.
Weak El Nino = UK dismal, mild winter.
Strong La Nina = UK dismal, mild winter.
Weak La Nina = UK dismal, mild winter.
ENSO neutral = UK dismal, mild winter.

Siince, dismal, dank, awful, mild winters are the norm for the UK, how can we draw any conclusions from whatever state ENSO is in and the dismal, awful, winter crud we get in these islands?

1947 - fantastic winter - what were the teleconnecitons which caused that?

1963 - fantastic winter - what were the teleconnecitons which caused that?

1981 - fantastic winter - what were the teleconnecitons which caused that?

2010 - decent winter - now that one I put down to a lack of solar activity during a prolonged minimum.

Maybe we have to wait for the impending solar minimum to get going before we shall have another decent winter, whatever ENSO decides to do!

1947 happened  during relatively high solar output 

1963 was fairly low solar output but nothing exceptional

1981 ditto

2009/10  was also fairly low 

Obviously solar output near to the minimum helps greatly but we can still end up wiith cracking winters during high solar output levels. You rolls ya dice and takes yer chances.😁

ECM looking very encouraging this morning. Not because the op (or ensembles) show any particular cold outlook, but becsue it shows an early death for the PV:

Out to Dec 23rd and some interesting possibilities emerge on the op. Again, ludicrous to take at face value but interesting to look at the trends as the festive period comes into viewing range. If you offer me a UK high with a frozen Europe for Christmas I'd probably take it to be fair

Sample of 5 strongest El Ninos.Ratio NAO + :NAO Dec 60:40 :Jan 60:40 Feb 40:60

Agree

I figured the 12z Op must have been pretty rubbish to elicit no comments here.

Just checked it out and yes  - complete Paddy Pantsdown of a run!