Tally Ho, I think Darren makes some very good points. In a nutshell we need everything in our favour (for cold weather) in the modern era. 

If factors are conflicting = mild zonality. If factors are poor (as they are now) = supercharged mild zonality - hence my suggestion that flooding/temp records are likely to be broken over the coming 3 months.

I think some of the forcing mechanisms support a colder winter this year. Personally I see the La Nina as broadly positive and preferable to El Nino when looking for cold weather. However, the simple reality is you can not ignore month after month of above average temperatures. 

https://www.metoffice.gov.uk/hadobs/hadcet/cet_info_mean.html

The definition of insanity is doing the same thing over and over again and expecting different results.

The science says that, in simple terms, increasing GHGs that cause warming in the lower atmosphere also cause cooling in the stratosphere.

Darren? Is Retron' I assume?

Yes! - Thanks for the link btw!

I was also watching the Winter Update eleven on 'Gavs Weather Vids' and he anticipated as does the data show that the La Nina could have already reached it's peak and the CFS has backed away from the forecast of a strong super La Nina. But time will tell. We will have a La Nina winter of course but will it be a weak, moderate or strong is still unknown a bit like the QBO. Also there is possibility of the SST's warming in ENSO 3.4 region and cooling down in the eastern Pacific which is also interesting too.

Again - I still think the colder than average stratospheric temperatures we have been seeing over autumn/winter months of recent years are the main cause of the strong PV which has strengthened to zonal westerlies and thus given us persistent mild zonality.  

I have had a look at the most frequently used climate indexes and how they correlate to the mean winter CET over the winter periods 1950-51 to 2019-20

What comes out strongly is that the only indexes which have a strong correlation to the CET are the Arctic Oscillation (AO) and the closely related North Atlantic Oscillation (NAO). When the average of the winter values of these indexes are used, the correlation coefficient to the mean winter CET is 0.67. No other index gets higher than 0.19 which may be sufficient to provide “nudges” to the mean winter CET but are far from influential when taken just on their own.

Since the AO and NAO are closely related (correlation=0.78) only the AO is used for the rest of the analysis.

In its positive index phase (high polar vortex strength, low height anomalies over the north pole) the AO leads to a strong “zonal” jet stream across the Atlantic and generally wet and mild conditions in the UK. The opposite occurs with a negative index leading to a weaker flow and more “meridional” or buckled jet stream and often a cold “blocked” winter

At the same latitude in different parts of the world the effect of the AO on winter weather is different. In the north east of North America (such as Newfoundland ) there is a reversed correlation with the coldest weather matching the positive index. In the north west of North America (such as Vancouver) there is no significant correlation. In Eastern Russia the correlation of positive AO index to milder winters starts to return and in Eastern Europe (Minsk for instance) this correlation is as marked as it is for the UK

It is known that the Jet Stream anchors itself to the Rocky Mountains in Canada and, for a strong flow in a positive AO Index, dives south while crossing the USA so that the North East of the USA is on the “cold” side of a powerful jet with winds blowing from the interior of the North American continental mass. Hence this part of the world has the reverse relationship with the index to everywhere else. A more variable set-up would be in place here for a negative AO index with a meandering jet and some easterly flow from a relatively warm ocean.

For the Eurasian land mass a strong westerly flow will bring milder weather from the Atlantic across most of the land mass

It is worth noting that in northern Eurasia the AO index  has the most significant correlation with winter temperature but in the north east of North America it is the AMO index (0.57) and in the north west of North America both ENSO (0.36) and PDO (0.47)  are much more significant

The frequency of winters with a positive AO index (mild in Europe) has increased noticeably from an average of about 25% in the period 1950-1989 to about 60% in the period 1990-2020. As well as general global temperature rise of about 0.87C since 1950, there has also been a more than doubling in the frequency of positive AO index “mild” set ups leading to an overall rise of 1.66C in the mean winter CET on linear trend since 1950

The bad news is that even with all these correlations, just like the CET itself, there is no way to forecast what the AO index for the following winter will be with any accuracy. The synoptic forecasts provide a short -term forecast in exactly the same way that the temperature itself is forecast but only for 14 days ahead at the most.

There is a low correlation between the Autumn AO (Sept to Nov) with the AO Index for the following winter (Dec-Feb) of only 0.27 and a negative correlation between the Autumn AO Index and the Winter CET of -0.15

It is probably a statistical fluke but for the last 6 years the sign of the Autumn AO averaged has been reversed in the following winter average.

And this gets us back to where Benfield Hazzard and the Met were 15 or 20 year ago. If you remember there was a lot of interest in NAO forecasts based on May SSTs and other factors with a long lead time.

Well the data and stats I used from 1950-2020 makes me think they were on the right track.

My main quibble with the paper they produced is that they were focussing on the NAO rather than the AO and trying to find a correlation with Atlantic SST's. As the AO is a global NH index but the NAO is just for the Atlantic area of the NH and the two are highly correlated I would have thought that they should be looking for global NH influences. It seems likley to me that something at a global level (NH) is influencing both indexes in the same way

Winter 2019-2020 is a very good example of how the AO can swamp everything else when determining winters in the UK

Gav's winter forecast was a bust last year (apologies to Gav but he says the same thing in his post review !) even though he went to great kengths to look at the whole range of criteria that could conceivably determine the outcome. On the analogues he narrowed down to 3 earlier years which could be a signal for the 2019-2020 NH hight nomalies

And the actual height anomalies in Autimn 2019 led me to think he may well have nailed it last year as there was a great similarity

But the whole patterned flipped over during the winter to give us the 2nd strongest +ve AO in 70 years and an exceptionally mild winter here in the UK as per the CET/AO correlation

So all someone has to determine is why did this happen

My intuition (or guess) is some relationship to global SST's but it's not at all obvious

And that's the problem. The AO/NAO are just representations of relative pressure at given locations at a given time.

The AO/NAO figures in advance of the date are just a different way of presenting output from models, whilst 'hindsight' examinations of the AO/NAO and correlations to actual conditions have little value in seasonal forecasting.

The holy grail is, of course, finding and connecting the various 'triggers' for what leads to a positive or negative AO/NAO (or whatever such measurement).

Brian mentions the use of North Atlantic SST's in May, which has since been shown to have negligible value. ENSO is also used, but again away from certain areas, this has only very modest use in seasonal forecasting (and I know ENSO is the representation of SSTs in the tropical East Pacific rather than SLP) 

My view is that if enough factors are considered, moderately accurate seasonal forecasts are possible; weather follows the laws of physics after all. It's just that there likely needs to be hundreds if not thousands of individual factors. 

Yes that's true and as you say we are still in search of the Holy Grail - the real cause(s) of why things are the way they are in the hope that it is not just a purely chaotic outcome of the "Butterfly Effect"

But I still think this representation is "only" one step removed from the underlying cause whereas the more common approach of attempting to predict the winter temperature in the UK is a further step (or more) away still

It's amazing how many people don't seem to understand that very point. I won't mention names but some are quite well respected in the field.

The other fun one is people who should know better not understand geopotential anomaly charts - always good for a grin!

(I've seen many a time these people assuming a large positive anomaly near Scandinavia means a Scandi High, for example, or a weak positive anomaly over Iceland means the Icelandic low is nowhere to be seen... neither of which is necessarily the case).

I doubt that would be true for our region.  Weve had enourmous amounts of rain since about June....

Playing golf you notice how soft the ground is, and its not been dry in months

Oh yes. 

https://apps.ecmwf.int/webapps/opencharts/products/extended-zonal-mean-zonal-wind?area=nh&base_time=202011090000

This is interesting , flick through the weeks and look at the zonal wind change 

If there is one single word that I DETEST more than any other in the world of weather it is teleconnections. Don't get me wrong the worlds weather is all interconnected but it is these so called experts who believe they have a handle on being able to read these and how they integrate with one another and how they think they can decipher which one or ones have a stronger influence at any given time is mind bogglingly naive on their part. 

Every year is the same now. These weather enthusiasts ( cringly called experts by some posters) tell us what is going to happen over the coming few weeks ( think twilight zone, crystal ball syndrome )  only to tell us duh MJO wave killed off the nina single (MJO barely out of the cod by the way) or the MJO never materialized. Really, go figure. 

Another good one ie high pressure here low pressure there good for wave breaking etc etc. Reality no wave breaking and upper vortex reaching near record strength complete garbage yet glowingly praised by other weather enthusiasts who are not really sure which direction a northern hemisphere high or low pressure rotate. Regardless of how inaccurate their ( or accurate for all the wrong reasons) forecasts are away goes mystic meg a few days later with another mind numbingly dumb post.

Just a little heads up for those that dabble. If SUPER COMPUTERS can not work out how such complex teleconnects interact and strengthen and weaken within this chaotic circuit then how the eck can you.

Thanks although I wish there was a key to go with it to explain? Obv the thin blue lines are representing each ENS member and thick blue is the ENS mean but... what else!?

As far as I am concerned people can be using seasonal models, pattern matching, teleconnections or a piece of seaweed. My question is a simple one and is always the same: What is their track record?

That's factually inaccurate,"we always had proper cold spells every winter". 

Where were the cold spells during the winter of 1974-75 just as an example? 

74-75 was a bit exceptional in that the cold synoptics came in the Autumn of 74 and then the Spring of 75.

We are now in situation where zonality throughout the winter months is becoming the norm as well as above average Autumns and Springs either side.

My understanding is La Nina is believed to increase the chance of cold periods during the first half of the winter. 

Didn't happen in 1975-76, a strong La Nina , most of the colder wintrier episodes happened during the 2nd half

Thought I would share this:

https://www.severe-weather.eu/long-range-2/winter-season-2020-2021-final-weather-forecast-fa/

Suggesting a lot of cold zonality and if this is right then this could well be a good ski season for Scottish ski resorts. The Alps do very badly for snow when it comes to cold zonality. - Just stumbled cross this ECM seasonal forecast for snow anomaly for the winter 20/21 shows Scotland above average snowfall and Aberdeenshire/eastern Scottish highlands seeing below average snow. Looks like it will be a great snowfall season for the Canadian Rockies (YET AGAIN!)

 Looks like the UK could be one of the coolest part of Europe if this ECM forecast Materialises.

If that first chart is correct then it may be good news for the ski resorts in the west of Scotland but not the east.

Christchurch Harbour 62-63 . Will we see it freeze this year or ever again?