Early run up to Winter 2021/2022 discussion

[Catacol]

23 hours ago, sebastiaan1973 said:

https://easternmassweather.blogspot.com/2021/11/outlook-2021-2022-in-like-lion-out-like.html

A lot which is good in there for the UK and another touting a SSW. I remain quietly optimistic about this winter despite what long range MetO and ECM products are suggesting. SSW will be key though. 

[northwestsnow]

2 hours ago, Catacol said:

A lot which is good in there for the UK and another touting a SSW. I remain quietly optimistic about this winter despite what long range MetO and ECM products are suggesting. SSW will be key though. 

EC seasonal looks blocked Dec and Jan C.

It's only Feb we see a +NAO..

[damianslaw]

2 hours ago, northwestsnow said:

EC seasonal looks blocked Dec and Jan C.

It's only Feb we see a +NAO..

If I had a preference I'd rather see a cold Dec- Jan combo than a Jan- Feb combo and certainly a Feb- Mar combo.

Last time we had a cold Dec- Jan combo was 2009- 2010. Jan 11 was chilly and overall colder than average but never severe. Rare to see a Dec and Jan that throughout are cold from start to finish. Optimum time perhaps mid Dec onwards - a la 2009. Wonderful time!

[Catacol]

3 hours ago, northwestsnow said:

EC seasonal looks blocked Dec and Jan C.

It's only Feb we see a +NAO..

Hmmmm - as with all charts and ensemble means and tercile probability graphs etc the beauty, such as it is, is in the eye of the beholder. The 3 month smoothed average from ECM is fairly grim

 

and the charts uploaded from Weathermodels by Sebastiaan recently were only a little better, January perhaps being the pick

 

These aren’t great to be honest, but we rarely see smoothed monthly or 3-monthly charts that look great for the U.K. But it doesn’t matter to me because modelling of SSW impacts is still really in its infancy. If we don’t get an SSW I won’t expect much to happen unless we get very lucky. If we get the vortex toppled from its throne then we have a chance no matter the charts.

 

Edited November 8, 2021 by Catacol

[Anthony Burden]

Evening all lots of uncertainty from the met office this evening,their mild to average temperatures

through this coming winter could be shot to pieces.All on what happens when this vigorous low crosses 

to the north of the U.K. into Scandinavia leaving this void for high level blocking to occur.Exact time 

for this to happen uncertain,and of course nothing certain in weather terms.But as charts are showing 

that rare phenomenon northern blocking starts to take place throwing a spanner in the works of plenty

of forecasts.We will wait with bated breath a very important weather change that’s for sure if it happens.

[MP-R]

On 08/11/2021 at 17:52, damianslaw said:

If I had a preference I'd rather see a cold Dec- Jan combo than a Jan- Feb combo and certainly a Feb- Mar combo.

Last time we had a cold Dec- Jan combo was 2009- 2010. Jan 11 was chilly and overall colder than average but never severe. Rare to see a Dec and Jan that throughout are cold from start to finish. Optimum time perhaps mid Dec onwards - a la 2009. Wonderful time!

Definitely, plus a +NAO never seems to be as bad in Feb & Mar as in Dec & Jan.
 

Cant get much better timing than December 2009 for the onset of cold. I clearly remember the transition from wet and windy on the 07th to mild and sunny on the 09th to cold and foggy on the 11th.

[MattH]

1 hour ago, Catacol said:

Hmmmm - as with all charts and ensemble means and tercile probability graphs etc the beauty, such as it is, is in the eye of the beholder. The 3 month smoothed average from ECM is fairly grim

 

and the charts uploaded from Weathermodels by Sebastiaan recently were only a little better, January perhaps being the pick

 

These aren’t great to be honest, but we rarely see smoothed monthly or 3-monthly charts that look great for the U.K. But it doesn’t matter to me because modelling of SSW impacts is still really in its infancy. If we don’t get an SSW I won’t expect much to happen unless we get very lucky. If we get the vortex toppled from its throne then we have a chance no matter the charts.

 

The seasonal models, especially the 3 month mean plots are often useless. The individual monthly breakdown while still likely to bring errors, at least does provide some further insights which support the broader background teleconnections, with the signal there for blocking patterns through the early part of the winter.

While one could call this cherry picking, we only need to look back to this time last year and the 500mb EC Seasonal Nov update for the Dec, Jan and Feb period and what actually occured, it wasn't even close...

Again, cherry picking perhaps and what's not to say it won't be right this year, etc, etc. The point here mind is that just like we can pre-empt NWP in the short-term, with teleconnections and the likes the GSDM, we can also provide a counterbalance to the raw seasonal model output which we all know is fraught with difficulties, despite the impressive computer power at hand.

Given the broader background signals in play then I don't think we have a better chance of blocking patterns this winter and also it will bring in to play scientific analysis as well. There are clearly many studies/journals/analysis on the early winter blocking signals within an La Nina regime (especially depending on the type of Nina), while there is also a known link between the relatively rare La Nina and eQBO combo combining to increase the risk of a winter SSW, as well. The 'modern unknown' mind which I don't think anyone can factor in properly is global warming, the state of the arctic and global wildfires, etc. As ever mind we can never cover it all to the nth degree when it comes to seasonal predictions and analysis, it's just not possible as you know too.

While we always need to be cautious for any connection between the strat and the trop within the next 4 to 6 weeks, there remains room for optimism, that this won't be a period where the connection is strong and robust like would be seen within a strong Nino/wQBO winter, for example. We all know it is the default pattern, so are constantly fighting against it, but clearly that fight can be won, as perfectly exampled in 2009, 2010, etc.

Therefore the SSW risk may not necessarily be the 'holy grail' this winter, as is often the case IMO. Granted, the broader evolution through Jan and Feb within a La Nina winter is towards a +ve NAO regime, which the seasonal models do show, etc. This is also another setup whereby if a significant SSW event occured in Jan (particularly if a split/wave 2 event, as compared with a wave 1 displacement), then the seasonal models could be way off for the second half of the winter, but that whole potential will take care of itself as the weeks progress by. The 'holy grail' for all winter fans this winter would be a trop-led blocking pattern through the early winter, and this then being followed by a mid-Jan SSW of significance which then potentially brings late winter blocking synoptics as a resultant of the SSW.

First and foremost, between now and late Dec, the key features to keep tabs on are a continued lack of any organised strat and trop connection, and an overall 'unusual' setup whereby blocking patterns are often in evidence within NWP, again similarly to 2009/2010. I'm not saying, by any means this will be a repeat early season, but it's that unusual repetative blocking signal that needs to be watched for, as apposed to the typical PV of doom that setups up shop over Greenland within the next 2 weeks and then writes off the first third of winter. Again, this the often 'usual' evolution for our 'corner of the N Hem' but I have a distinct feeling that won't be the case this year...

Cheers, Matt.

 

 

 

[Anthony Burden]

25 minutes ago, MattHugo said:

The seasonal models, especially the 3 month mean plots are often useless. The individual monthly breakdown while still likely to bring errors, at least does provide some further insights which support the broader background teleconnections, with the signal there for blocking patterns through the early part of the winter.

While one could call this cherry picking, we only need to look back to this time last year and the 500mb EC Seasonal Nov update for the Dec, Jan and Feb period and what actually occured, it wasn't even close...

Again, cherry picking perhaps and what's not to say it won't be right this year, etc, etc. The point here mind is that just like we can pre-empt NWP in the short-term, with teleconnections and the likes the GSDM, we can also provide a counterbalance to the raw seasonal model output which we all know is fraught with difficulties, despite the impressive computer power at hand.

Given the broader background signals in play then I don't think we have a better chance of blocking patterns this winter and also it will bring in to play scientific analysis as well. There are clearly many studies/journals/analysis on the early winter blocking signals within an La Nina regime (especially depending on the type of Nina), while there is also a known link between the relatively rare La Nina and eQBO combo combining to increase the risk of a winter SSW, as well. The 'modern unknown' mind which I don't think anyone can factor in properly is global warming, the state of the arctic and global wildfires, etc. As ever mind we can never cover it all to the nth degree when it comes to seasonal predictions and analysis, it's just not possible as you know too.

While we always need to be cautious for any connection between the strat and the trop within the next 4 to 6 weeks, there remains room for optimism, that this won't be a period where the connection is strong and robust like would be seen within a strong Nino/wQBO winter, for example. We all know it is the default pattern, so are constantly fighting against it, but clearly that fight can be won, as perfectly exampled in 2009, 2010, etc.

Therefore the SSW risk may not necessarily be the 'holy grail' this winter, as is often the case IMO. Granted, the broader evolution through Jan and Feb within a La Nina winter is towards a +ve NAO regime, which the seasonal models do show, etc. This is also another setup whereby if a significant SSW event occured in Jan (particularly if a split/wave 2 event, as compared with a wave 1 displacement), then the seasonal models could be way off for the second half of the winter, but that whole potential will take care of itself as the weeks progress by. The 'holy grail' for all winter fans this winter would be a trop-led blocking pattern through the early winter, and this then being followed by a mid-Jan SSW of significance which then potentially brings late winter blocking synoptics as a resultant of the SSW.

First and foremost, between now and late Dec, the key features to keep tabs on are a continued lack of any organised strat and trop connection, and an overall 'unusual' setup whereby blocking patterns are often in evidence within NWP, again similarly to 2009/2010. I'm not saying, by any means this will be a repeat early season, but it's that unusual repetative blocking signal that needs to be watched for, as apposed to the typical PV of doom that setups up shop over Greenland within the next 2 weeks and then writes off the first third of winter. Again, this the often 'usual' evolution for our 'corner of the N Hem' but I have a distinct feeling that won't be the case this year...

Cheers, Matt.

 

A great read Matt very informative.

 

 

[damianslaw]

1 hour ago, MP-R said:

Definitely, plus a +NAO never seems to be as bad in Feb & Mar as in Dec & Jan.
 

Cant get much better timing than December 2009 for the onset of cold. I clearly remember the transition from wet and windy on the 07th to mild and sunny on the 09th to cold and foggy on the 11th.

Yes it was a rapid turnaround after the exceptionally wet November which was also very mild. It was an unusual transition, azores high ridged north through the UK and to scandi, heights seemed to appear out of nowhere to our NE at the same time.. then we had a 4-5 week very cold snowy spell - perfect timing, and I preferred it to December 2010.

[damianslaw]

1 hour ago, MattHugo said:

The seasonal models, especially the 3 month mean plots are often useless. The individual monthly breakdown while still likely to bring errors, at least does provide some further insights which support the broader background teleconnections, with the signal there for blocking patterns through the early part of the winter.

While one could call this cherry picking, we only need to look back to this time last year and the 500mb EC Seasonal Nov update for the Dec, Jan and Feb period and what actually occured, it wasn't even close...

Again, cherry picking perhaps and what's not to say it won't be right this year, etc, etc. The point here mind is that just like we can pre-empt NWP in the short-term, with teleconnections and the likes the GSDM, we can also provide a counterbalance to the raw seasonal model output which we all know is fraught with difficulties, despite the impressive computer power at hand.

Given the broader background signals in play then I don't think we have a better chance of blocking patterns this winter and also it will bring in to play scientific analysis as well. There are clearly many studies/journals/analysis on the early winter blocking signals within an La Nina regime (especially depending on the type of Nina), while there is also a known link between the relatively rare La Nina and eQBO combo combining to increase the risk of a winter SSW, as well. The 'modern unknown' mind which I don't think anyone can factor in properly is global warming, the state of the arctic and global wildfires, etc. As ever mind we can never cover it all to the nth degree when it comes to seasonal predictions and analysis, it's just not possible as you know too.

While we always need to be cautious for any connection between the strat and the trop within the next 4 to 6 weeks, there remains room for optimism, that this won't be a period where the connection is strong and robust like would be seen within a strong Nino/wQBO winter, for example. We all know it is the default pattern, so are constantly fighting against it, but clearly that fight can be won, as perfectly exampled in 2009, 2010, etc.

Therefore the SSW risk may not necessarily be the 'holy grail' this winter, as is often the case IMO. Granted, the broader evolution through Jan and Feb within a La Nina winter is towards a +ve NAO regime, which the seasonal models do show, etc. This is also another setup whereby if a significant SSW event occured in Jan (particularly if a split/wave 2 event, as compared with a wave 1 displacement), then the seasonal models could be way off for the second half of the winter, but that whole potential will take care of itself as the weeks progress by. The 'holy grail' for all winter fans this winter would be a trop-led blocking pattern through the early winter, and this then being followed by a mid-Jan SSW of significance which then potentially brings late winter blocking synoptics as a resultant of the SSW.

First and foremost, between now and late Dec, the key features to keep tabs on are a continued lack of any organised strat and trop connection, and an overall 'unusual' setup whereby blocking patterns are often in evidence within NWP, again similarly to 2009/2010. I'm not saying, by any means this will be a repeat early season, but it's that unusual repetative blocking signal that needs to be watched for, as apposed to the typical PV of doom that setups up shop over Greenland within the next 2 weeks and then writes off the first third of winter. Again, this the often 'usual' evolution for our 'corner of the N Hem' but I have a distinct feeling that won't be the case this year...

Cheers, Matt.

 

 

 

Great post. Thanks for your thoughts. I've commented on the strat thread how quiet the atlantic has been this year, similiar to 1996 and 2010 Not saying we will see a Dec like 1996 and 2010, but interesting to note both years brought cold ends to November, and highly blocked cold Decembers - very cold in the case of 2010. Were both years la nina as well I think... mmm...

[Uncertainty]

44 minutes ago, MattHugo said:

The seasonal models, especially the 3 month mean plots are often useless. The individual monthly breakdown while still likely to bring errors, at least does provide some further insights which support the broader background teleconnections, with the signal there for blocking patterns through the early part of the winter.

While one could call this cherry picking, we only need to look back to this time last year and the 500mb EC Seasonal Nov update for the Dec, Jan and Feb period and what actually occured, it wasn't even close...

Again, cherry picking perhaps and what's not to say it won't be right this year, etc, etc. The point here mind is that just like we can pre-empt NWP in the short-term, with teleconnections and the likes the GSDM, we can also provide a counterbalance to the raw seasonal model output which we all know is fraught with difficulties, despite the impressive computer power at hand.

Given the broader background signals in play then I don't think we have a better chance of blocking patterns this winter and also it will bring in to play scientific analysis as well. There are clearly many studies/journals/analysis on the early winter blocking signals within an La Nina regime (especially depending on the type of Nina), while there is also a known link between the relatively rare La Nina and eQBO combo combining to increase the risk of a winter SSW, as well. The 'modern unknown' mind which I don't think anyone can factor in properly is global warming, the state of the arctic and global wildfires, etc. As ever mind we can never cover it all to the nth degree when it comes to seasonal predictions and analysis, it's just not possible as you know too.

While we always need to be cautious for any connection between the strat and the trop within the next 4 to 6 weeks, there remains room for optimism, that this won't be a period where the connection is strong and robust like would be seen within a strong Nino/wQBO winter, for example. We all know it is the default pattern, so are constantly fighting against it, but clearly that fight can be won, as perfectly exampled in 2009, 2010, etc.

Therefore the SSW risk may not necessarily be the 'holy grail' this winter, as is often the case IMO. Granted, the broader evolution through Jan and Feb within a La Nina winter is towards a +ve NAO regime, which the seasonal models do show, etc. This is also another setup whereby if a significant SSW event occured in Jan (particularly if a split/wave 2 event, as compared with a wave 1 displacement), then the seasonal models could be way off for the second half of the winter, but that whole potential will take care of itself as the weeks progress by. The 'holy grail' for all winter fans this winter would be a trop-led blocking pattern through the early winter, and this then being followed by a mid-Jan SSW of significance which then potentially brings late winter blocking synoptics as a resultant of the SSW.

First and foremost, between now and late Dec, the key features to keep tabs on are a continued lack of any organised strat and trop connection, and an overall 'unusual' setup whereby blocking patterns are often in evidence within NWP, again similarly to 2009/2010. I'm not saying, by any means this will be a repeat early season, but it's that unusual repetative blocking signal that needs to be watched for, as apposed to the typical PV of doom that setups up shop over Greenland within the next 2 weeks and then writes off the first third of winter. Again, this the often 'usual' evolution for our 'corner of the N Hem' but I have a distinct feeling that won't be the case this year...

Cheers, Matt.

 

 

 

Fantastic to have you back posting in here Matt. Hopefully the models will fall into line with our statistical reasoning in the coming weeks. Let’s hope it does, as the less said about next year’s probable WQBO, Positive enso and higher solar combo the better!

[northwestsnow]

December shaping up to be a very cold month across much of Europe thanks to a blocked Atlantic...

I wouldn't be surprised to see a Euro freeze later this month onwards..

[John88B]

The models now showing plenty of northern blocking are tying in with the winter forecast given by our local weatherman Fergie a couple of weeks ago.

Of course nothing is guaranteed but with the Atlantic having been pretty dead for months now and northern blocking already appearing I feel that there is now strong chance of a cold/very cold winter ahead. We're certainly due one.

[Anthony Burden]

Hi independent meteorologist like Matt Hugo John Hammond all leaning towards a cold 

early winter scenario,due to la Nino E-QBO influence,plus Matt feels that an SSW could well

show its face in December bringing a possible longer cold winter to our shores.Met office 

not so keen, always cautious and never bullish although trying to cover all scenarios.

[Catacol]

16 hours ago, MattHugo said:

 

The 'holy grail' for all winter fans this winter would be a trop-led blocking pattern through the early winter, and this then being followed by a mid-Jan SSW of significance which then potentially brings late winter blocking synoptics as a resultant of the SSW.

 

Wholeheartedly yes Matt - and in a weak/moderate Nina with eQBO we probably have the greatest chance of this coming to pass compared to other background setups. NWP beginning to firm up on the atlantic ridge we all expected/hoped to see appear at the start of the season. First building block....

[Sunny76]

I just hope its not too much of a good thing scenario. 

A few days of snow is fine, but anything lasting more than a week, will become tedious, and possibly dangerous. 

Especially with winter bills going up this year, it could be sods law if we get an extended bitter spell.

[SqueakheartLW]

On 08/11/2021 at 21:07, Uncertainy said:

Fantastic to have you back posting in here Matt. Hopefully the models will fall into line with our statistical reasoning in the coming weeks. Let’s hope it does, as the less said about next year’s probable WQBO, Positive enso and higher solar combo the better!

Table 1 A table of the timings and strengths of the possible extreme El Niño Modoki events in 2020s. The confidence interval is at the 90% level.

WWW.NATURE.COM

Should take a look at this. If this is correct then cold could still be on even for winter 2022/2023 if this prediction of a modoki EL Nino turns out to be true. We all know what happened during the 2009/2010 modoki EL Nino event.

Based on this table there should have been one in 2019/2020 but that year strange things were going on in the atmosphere, the southern SSW, the disrupted QBO and the record positive IOD which no doubt disrupted the formation of the possible modoki EL Nino that year and the polar vortex of doom would have likely overridden everything anyhow.

[frederiksen90]

Den NAO -indekset i efteråret 2021 til sammenligning med NAO i 2012

2021

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

 

2012

https://1.bp.blogspot.com/-OwO-iO59NXw/UKOoMxTVZKI/AAAAAAAAFHU/YgMrEyqVQ8Q/s1600/NAO_late2012.JPG?fbclid=IwAR3g4aR-Wv9o2UcdqTMrdDPaMufDyU7MYxHqRPa37Gq2XFg9Xh7mawvu7F8

 

Bemærk den identiske tendens med først en negativ NAO i august begge år, derefter en stigning til kortsigtet positiv i september. Dernæst kraftig negativ NAO i oktober, før en kort stigning igen fra start til midten af november. En generel negativ NAOmed korte afbrydelser. De minder ret meget om tidspunktet for de korte positive perioder i september og november med den mest negative periode i oktober. Går den så i negativ igen i december? 2012 var året, hvor vi var på vej ud af det sidste solminimum (begyndelsen af solcyklus 24) med stigning i solpletter, men med lav geomagnetisk aktivitet. 2021 er med andre ord samme sted som 2012, hvor vi nu igen er bevæget os ind i en ny solcyklus på vej ud af minimumet med en stigning i solpletter, men stadig med lav geomagnetisk aktivitet. Begge år med Eastern QBO og et dødt Atlanterhav.

 

Optimismen er fortsat høj. For det første passer korrelationen mellem AP-indekset og oktober NAO perfekt. Nu stemmer sammenhængen også mellem efterårets NAO- tendens i år med 2012 (begge år samme sted i solcyklussen). Og i forhold til sidste år er den negative NAO blevet endnu stærkere dette efterår. AP/ NAO- forskning antydede, at blokade i troposfæren og en negativ NAO skulle forbedres, når et lavt AP-indeks faldt sammen med østlig QBO . Det kan nu bekræftes, at efter skiftet til østlig QBO kombineret med lav geomagnetisk aktivitet, har vi nu den mest negative NAO- periode siden vi forlod vinteren 2012/13

Edited November 9, 2021 by frederiksen90

[Uncertainty]

20 hours ago, SqueakheartLW said:

Table 1 A table of the timings and strengths of the possible extreme El Niño Modoki events in 2020s. The confidence interval is at the 90% level.

WWW.NATURE.COM

Should take a look at this. If this is correct then cold could still be on even for winter 2022/2023 if this prediction of a modoki EL Nino turns out to be true. We all know what happened during the 2009/2010 modoki EL Nino event.

Based on this table there should have been one in 2019/2020 but that year strange things were going on in the atmosphere, the southern SSW, the disrupted QBO and the record positive IOD which no doubt disrupted the formation of the possible modoki EL Nino that year and the polar vortex of doom would have likely overridden everything anyhow.

That’s fascinating research pal, what a great find. I hope it’s correct.

Finally, some good news: The BCC model, which really did the best last year in going for extensive blocking is at it again.

Last Year wasn’t its only success story:

2015

Successfully pining down the +AO

Last Year

Commendable and picked out the very high average polar heights

2014/2015, a very forgettable winter despite model hype 

picked out the boring signal at least

2018/2019

Not terrible as there was an SSW this year but the highway heights over Spain / Portugal prevented anything cold penetrating frequently towards the U.K. 

Interestingly , the projection for this month might not end up too far off…

Not falling for the big GH like the GFS and, to a lesser extent EC46 then.

Heights build through the U.K. into December

But January gets really interesting

No let up in February, this would really put the cat amongst the gas price pigeons, but also please a great deal of viewers of this website…

So just a bit of positivity for coldies in the gloom. 

Let’s be clear, the vast majority of other seasonals have plumped for a +NAO and another horrid wet winter, but I personally will retain hope as this model has come good in the past. And indeed many background signals are supportive of cold spells this winter. What a stunning coup it would be if it were to be correct this time, even partially so.
 

Then we really would have to view it front and centre of our seasonal selections.

I just can’t see Glosea showing anything but a hardcore ++NAO tomorrow but I’m Staying on the fence for now. It’s only mid November and not the time to throw the towel in.

[Don]

2 hours ago, Uncertainy said:

That’s fascinating research pal, what a great find. I hope it’s correct.

Finally, some good news: The BCC model, which really did the best last year in going for extensive blocking is at it again.

I think BCC was also one of the few models which predicted the very hot summer in 2018, too.  Doesn't mean it will be correct for this coming winter, but certainly keeps the hopes alive!

Edited November 10, 2021 by Don

[damianslaw]

3 minutes ago, Don said:

I think BCC was also one of the few models which predicted the very hot summer in 2018, too.  Doesn't mean it will be correct for this coming winter, but certainly keeps the hopes alive!

Yes Beijing Climate centre did very well last year..  only one that did. 

[sebastiaan1973]

Cohen view. https://www.aer.com/science-research/climate-weather/arctic-oscillation/

-----------------------------

Plain Language Summary

I use October Eurasian snow cover extent (SCE) as one of our main predictors for winter temperature anomalies across the Northern Hemisphere (NH).  Eurasian SCE was slightly above normal for the month of October coupled with La Niña is biasing the AER winter forecast on the cold side of normal for western and central North America, Northern Europe.  The winter forecasts from the government centers are much warmer (at least in extent).  One wild car could be the water temperatures in the North Pacific, if strong enough they can favor the core of cold temperatures further to west across North America.

Impacts

I have been promising a preliminary winter forecast for surface temperature anomalies for the Northern Hemisphere and today I deliver.  The forecast was generated the last week of October using my estimate of October Eurasian snow cover extent (SCE), the dominant sea level pressure anomaly across Northern Eurasia for October, the September Arctic sea ice extent anomaly and the predicted winter (December-February) Niño 3.4 index (a common indicator for El Niño/Southern Oscillation (ENSO)).  Also I included in this winter’s forecast my own very rough estimate for the winter Pacific Decadal Oscillation (PDO) index.  Typically, I don’t include the PDO index in my winter forecasts, but the strong negative PDO pattern has emerged, and it could very well be a factor.   in Figure i, I present a preliminary AER winter forecast that was shared with clients at the end of October.  I will share an update to the winter forecast on the blog at the end of the month. Please keep in mind since the forecast was generated the observed values for October SCE and SLP are now known and will be used in updated forecasts.  Also, I used as my climatology the values from 1991-2020.

Figure i.  Forecasted surface temperature anomalies for December 2021 - Fwbruary 2022 from the AER model.

I have to say when the forecast was first generated, I was surprised by how cold the forecast appears.  At this point I don’t have a lot of confidence in the forecast, and it will certainly be revised.  But just to emphasize how cold the forecast appears, at least visually (and to be honest the anomalies are not large), all I need to do is present in Figure ii a consensus of the dynamical model temperature anomaly forecast from the North American Model Ensemble (NNME).  The dynamical models are predicting almost universal relative warmth across the Northern Hemisphere continents except for Alaska and Western Canada.  Across North America it is a canonical La Niña pattern and across Eurasia is it a global warming signal.  To be fair there is probably some global warming influence included in the North American forecast as well. 

Figure ii. Forecasted surface temperature anomalies for December 2021 - Fwbruary 2022 from the NMME models.

I have discussed this before, but the lack of variability among the model forecasts is noteworthy and one should look at all the NMME more forecasts to see just how much they all resemble each other (see NMME winter forecasts).  The European C3S ensemble also looks similar but has not been updated for November yet (see C3S winter forecast).  In my opinion observational analysis between ENSO and NH winter temperatures does not support such a high degree of confidence in the forecast from the dynamical models.  I have argued in my papers that the dynamical models are insensitive to Arctic forcing and overly sensitive to tropical forcing (e.g. Cohen et al. 2016).  The large amount of variability or noise in the climate system is used to criticize arguments of Arctic influence (including my own), i.e., the large amount of noise makes it impossible to distinguish or identify the signal of Arctic influence, i.e., all noise and no signal.  Yet when it comes to tropical influence it is all signal and no noise?  Anyway, enough of my griping.

But as I have argued many times before even if the AER winter forecast is completely wrong, I strongly believe that it provides value in at least it is an alternative forecast and not a herd forecast.  And all we need to do is look to last winter to see how wrong the herd forecast can be (see the blog post from March 8, 2021).  But I readily admit if the polar vortex remains strong this winter, the dynamical models will look like champs in March 2022, which is one takeaway from winter 2019/20.

I do think that Arctic surface conditions, especially with the recent snow blitz across Asia are well suited for disrupting the polar vortex.  Negative sea anomalies heading into the winter are focused in two regions.  The first is the Barents-Kara Seas and low sea ice in this region is thought to be most favorable for disrupting the polar vortex.  The other region is Baffin Bay.  As I showed last week, negative sea ice anomalies in this region are associated with relatively cold temperatures in the Eastern US and Northern Europe.  Whether sea ice anomalies in this region can force anything I don’t know, and they could just be a lagging indicator (they indicate recent Greenland blocking that favors relatively cold temperatures in the Eastern US and Northern Europe but warm temperatures in Baffin Bay, which inhibits sea ice formation).

Though October SCE was not impressive and only slightly above normal but so far November SCE is very impressive.  But for full disclosure, I have not shown any analysis that November SCE has any influence on winter weather, but other studies have (see blog from October 25, 2021).  Also, there are three weeks left and SCE could still change dramatically.

But snow and sea ice can remain very favorable for disrupting the polar vortex from now until March, but they alone are not sufficient to force a polar vortex disruption.  Whatever signal they provide will never make it to the polar vortex without blocking/high pressure in the Barents-Kara Seas/Ural/Scandinavia region.  Right now, there are no signs of a meaningful return of blocking/high pressure to this region.  Based on the model forecasts I believe you have to bias the probability of a relatively strong polar vortex and a relatively mild pattern across the NH including the Eastern US and Northern Europe heading into December.  The best possibility of resulting in meaningful cold, especially to the Eastern US, in my opinion would be another stretched polar vortex in December as is occurring now.  A larger polar vortex disruption that is associated with a sudden stratospheric warming takes longer to occur and without dramatic changes I don’t see one occurring in December.

But it is early, and I do believe that Arctic snow and ice favor a return of Barents-Kara Seas/Ural/Scandinavia region more so than its continuous absence.  But also in my opinion, the blocking needs to be persistent and not transitory to have enough influence to impact the winter means.  Early in my career all I wanted to see was Greenland blocking but now I am much more fixated on Ural blocking.  I see little evidence that Greenland blocking can perturb the polar vortex, instead Ural blocking is critical.  And I am more and more convinced that without some type of disruption to the polar vortex notable (or from my perspective memorable) winter weather is nearly impossible.  But to be fair to Greenland blocking it may be an early precursor to polar vortex stretching as we showed in Cohen et al. 2021.  And I don’t intend to diminish that Greenland blocking is strong signal for a Northeastern US snowstorm and certainly cold and snow for Northern Europe. Whether the new obsession is warranted is still an open question.

Finally, I did see the October value for the PDO and it was deep into negative territory; seems to me that it has been a while since we have observed a number that negative and my PDO index used as a predictor in the winter forecast may be too conservative.  A more negative PDO would favor pulling the cold temperatures across North America further west with more warming in the Eastern US.  I wish that I could be as confident as the dynamical models but as I see it, there are many mixed signals so far and therefore lots of uncertainty. AO Blog Update | AER | Weather Risk Assessment

  

Edited November 10, 2021 by sebastiaan1973

[SqueakheartLW]

Christmas 2021 Update Number 6

Christmas update number 6 is now upon us as I have collected another weeks worth of 2m temperature data from the CFS 9 monthly runs so here we go. Time to present the data I have gathered so far in the image below. Week 1 is no longer visible now so if you wish to see this data refer to an earlier Christmas update of mine.

As we can see here just like with all other weeks we have a whole range of outcomes again from mild to cold. No new record highs or lows were set during this last week.

How does week 6 compare with all of the others and will it be milder or colder than update 5 or sit somewhere in the middle or can be set mildest or coldest update so far, here are the numbers.

Week 1 came out like this                                                         Week 2 came out like this

              Average Min     Average Max     Average Mean                      Average Min       Average Max      Average Mean

Temp          3.61                      5.79                    4.70                  Temp          4.21                       5.96                     5.09

Anom        +1.52                     -1.24                  +0.14                 Anom        +2.12                     -1.07                    +0.53

Week 3 came out like this                                                         Week 4 came out like this

                Average Min    Average Max    Average Mean                     Average Min       Average Max      Average Mean

Temp           2.71                      5.43                     4.07                Temp          3.96                       6.36                     5.16

Anom          +0.62                   -1.60                    -0.49                Anom        +1.87                     -0.67                   +0.60

Week 5 came out like this

                Average Min    Average Max    Average Mean

Temp           4.00                      6.57                     5.29

Anom          +1.91                   -0.46                    +0.73

Week 6 summary

How does week 6 compare with weeks 1 to 5 and will we be milder or colder than last week or maybe even milder or colder than weeks 1 to 5. Included is the change from week 5 as well

                    Average Min                Average Max            Average Mean

Temp          4.14 (up +0.14)           6.54 (down -0.03)     5.34 (up +0.05)

Anom        +2.05                             -0.49                          +0.78

When we averaged out all of the max, min and mean data for week 1 it wasn't a great start for cold fans with the overall +0.14C milder anomaly. The coldies misery continued in week 2 when we shifted more into the direction of a milder Christmas overall and stood at a weekly average of 5.09C which was +0.53C above the 1991-2020 25th December mean. Week 3 was good news for coldies as we came back with an overall Christmas Day mean of 4.07C which is -0.49C below the 1991-2020 25th December mean. Update 4 came out as the mildest one so far last week with a Christmas Day mean anomaly of +0.60C. Update 5 was the mildest of the lot with a Christmas Day mean anomaly of +0.73C.

The bad news for coldies is that week 6 has pushed even further in the direction of milder conditions for Christmas Day as we have set a new averaged out mean of 5.34C which is +0.78C above the 1991-2020 Christmas Day mean and this is an increase of the anomaly by a small 0.05C. This puts us at 5 milder updates and just 1 colder update so far so chances of cold if CFS is to be believed are reducing every week I do these updates.

Edited November 11, 2021 by SqueakheartLW

[Day 10]

On 09/11/2021 at 21:46, frederiksen90 said:

Den NAO -indekset i efteråret 2021 til sammenligning med NAO i 2012

2021

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

 

2012

https://1.bp.blogspot.com/-OwO-iO59NXw/UKOoMxTVZKI/AAAAAAAAFHU/YgMrEyqVQ8Q/s1600/NAO_late2012.JPG?fbclid=IwAR3g4aR-Wv9o2UcdqTMrdDPaMufDyU7MYxHqRPa37Gq2XFg9Xh7mawvu7F8

 

Bemærk den identiske tendens med først en negativ NAO i august begge år, derefter en stigning til kortsigtet positiv i september. Dernæst kraftig negativ NAO i oktober, før en kort stigning igen fra start til midten af november. En generel negativ NAOmed korte afbrydelser. De minder ret meget om tidspunktet for de korte positive perioder i september og november med den mest negative periode i oktober. Går den så i negativ igen i december? 2012 var året, hvor vi var på vej ud af det sidste solminimum (begyndelsen af solcyklus 24) med stigning i solpletter, men med lav geomagnetisk aktivitet. 2021 er med andre ord samme sted som 2012, hvor vi nu igen er bevæget os ind i en ny solcyklus på vej ud af minimumet med en stigning i solpletter, men stadig med lav geomagnetisk aktivitet. Begge år med Eastern QBO og et dødt Atlanterhav.

 

Optimismen er fortsat høj. For det første passer korrelationen mellem AP-indekset og oktober NAO perfekt. Nu stemmer sammenhængen også mellem efterårets NAO- tendens i år med 2012 (begge år samme sted i solcyklussen). Og i forhold til sidste år er den negative NAO blevet endnu stærkere dette efterår. AP/ NAO- forskning antydede, at blokade i troposfæren og en negativ NAO skulle forbedres, når et lavt AP-indeks faldt sammen med østlig QBO . Det kan nu bekræftes, at efter skiftet til østlig QBO kombineret med lav geomagnetisk aktivitet, har vi nu den mest negative NAO- periode siden vi forlod vinteren 2012/13

Great post, thanks.

Translation to English for peeps.

 

The NAO index in the fall of 2021 for comparison with the NAO in 2012 2021

2012

Note the identical trend with first a negative NAO in August both years, then an increase to short-term positive in September. Next, strong negative NAO in October, before a brief increase again from start to mid-November. A general negative NAO with short interruptions. They are quite reminiscent of the time of the short positive periods in September and November with the most negative period in October. Will it then go into negative again in December? 2012 was the year we were heading out of the last solar minimum (beginning of solar cycle 24) with increase in sunspots but with low geomagnetic activity.

In other words, 2021 is the same place as 2012, where we are now again moving into a new solar cycle on the way out of the minimum with an increase in sunspots, but still with low geomagnetic activity. Both years with Eastern QBO and a dead Atlantic. Optimism remains high. First, the correlation between the AP index and the October NAO fits perfectly. Now the correlation is also correct between the autumn NAO trend this year with 2012 (both years in the same place in the solar cycle). And compared to last year, the negative NAO has become even stronger this fall. AP / NAO research suggested that blockade in the troposphere and a negative NAO should improve when a low AP index coincided with Eastern QBO. It can now be confirmed that after the switch to Eastern QBO combined with low geomagnetic activity, we now have the most negative NAO period since we left the winter of 2012/13

[SqueakheartLW]

12th winter 2021/2022 update based on the CFS 00z 9 monthly run dated 11/11/2021

As per usual we have reached my winter update time again and with the general getting milder trend on average with these updates it seems CFS is firmly in the milder winter domain now but will this update confirm this or will it spring out a nice cold surprise for us all. Time to summarize each month as normal.

December 2021

On this particular run for December 2021 the milder than average updates continued and unfortunately we came away with a milder update than last week for this month. Today we stand at 6.52C which is +1.55C above the 1991-2020 December mean and continues a general run of mild or very mild updates that kicked in a few weeks ago now. As December isn't that many weeks away now it would seem now that CFS is basically nailed on for a mild December 2021 now. The question is how mild more than is it going to be mild now.

January 2022

Last week's January 2022 update was basically about average but how did this week compared with that one. We came out more or less average again but slightly on the colder side of average this week compared with the slightly on the milder side last week. Today we stand at 4.50C which is -0.16C below the 1991-2020 January mean. This means January 2022 could very much still be up for grabs and it may take a few more updates on this particular month to get an idea where CFS thinks we are heading.

February 2022

February 2022's updates have been a little up and down lately with some mild updates followed by cold ones then back again. Last week was one of the cold ones but will this week come out cold to start a trend again or will we switch back mild and continue the recent alternating trend we have had. Unfortunately for coldies we have switched back to milder than average again as we came out at 6.00C which is +1.11C above the 1991-2020 February mean. Starting to look like February 2022 is a more up for grabs month now rather than a more definite bet for colder.

March 2022

March 2022, ever reliable for colder than average updates. Will March be able to save the day for coldies since the other 3 months have very much let us all down. The answer is yes but not by a huge margin. We came in at 5.89C which is only -0.85C below the 1991-2020 March mean and for March updates this is one of the less cold ones. Fits the overall theme of this update really it has to be said but at least good old reliable March 2022 can be relied upon at present to get us a colder anomaly to average.

Overall December 2021 - March 2022 based on CFS 00z 9 monthly run dated 11/11/2021

Overall we came away with a mean on this run of 5.73C which is +0.41C above the 1991-2020 mean for December to March. This was to be expected after the milder than average December and February updates here along with the average January and only a small amount colder March. Looking less likely we'll get a colder than average winter now if CFS has it nailed on and particularly December 2021 is looking increasingly likely to be mild now unless something strange happens.

3 Updates latest trend

Here are the previous tri update means as well as the most recent at the bottom of the list

Update batch                  December 2021        January 2022        February 2022        March 2022        OVERALL

Updates 1, 2 and 3         4.17C (-0.80C)           3.11C (-1.55C)        2.76C (-2.13C)         4.02C (-2.72C)     3.51C (-1.81C)

Updates 2, 3 and 4         3.45C (-1.52C)           3.26C (-1.40C)        2.99C (-1.90C)         4.67C (-2.07C)     3.59C (-1.73C)

Updates 3, 4 and 5         4.58C (-0.39C)           3.61C (-1.05C)        2.88C (-2.02C)         5.03C (-1.71C)     4.02C (-1.30C)

Updates 4, 5 and 6         4.51C (-0.46C)           3.88C (-0.78C)        2.67C (-2.22C)         5.37C (-1.37C)     4.10C (-1.22C)

Updates 5, 6 and 7         5.70C (+0.73C)          4.84C (+0.18C)       3.51C (-1.38C)         5.16C (-1.58C)     4.80C (-0.52C)

Updates 6, 7 and 8         5.55C (+0.58C)          4.26C (-0.40C)        4.57C (-0.32C)         5.01C (-1.73C)     4.85C (-0.47C)

Updates 7, 8 and 9         6.97C (+2.00C)          4.76C (+0.10C)       5.01C (+0.12C)        6.06C (-0.68C)     5.70C (+0.38C)

Updates 8, 9 and 10       6.68C (+1.71C)          3.69C (-0.97C)        4.76C (-0.13C)         5.69C (-1.05C)     5.21C (-0.11C)

Updates 9, 10 and 11     6.39C (+1.42C)          4.40C (-0.26C)        4.55C (-0.34C)        5.81C (-0.93C)      5.29C (-0.03C)

Latest                              December 2021       January 2022       February 2022      March 2022        OVERALL

Updates 10, 11 and 12  5.75C (+0.78C)        3.81C (-0.85C)       5.20C (+0.31C)        5.08C (-1.66C)     4.96C (-0.36C)

December 2021 - December 2021 has maintained it's position as the mildest month overall on my updates and this week is no exception. As update 9 was the freaky December 2015 ish mild update and this one has finally moved out of the 3 update rolling mean then this means despite today's mild update the rolling mean has still in fact become less mild as it has shifted from last weeks 6.39C (+1.42C milder) to this weeks 5.75C (+0.78C milder). This looks like good news on the 3 update trend but this doesn't change the overall story that the recent December 2021 updates have all come back milder than average and that is the most important trend I feel.

January 2022 - January 2022's 3 update mean has generally been bouncing around recently between milder, average and colder values. Last week we stood at 4.40C which was -0.26C colder than the 1991-2020 January mean. This week despite churning out a basically close to average January 2022 update we have taken a noticeable shift in the direction of colder with a new 3 update rolling mean of 3.81C which is -0.85C colder than the 1991-2020 January mean. This is because update 9 was a mild January 2022 update and now updates 10-12 contain two basically average updates 11 and 12 and update 10 which was one of my coldest January 2022 updates which has pulled this mean some way below 0 on the anomaly scale at least.

February 2022 - February 2022 had been the most likely month to turn out colder but recently this chance has reduced. Just bad news overall for February 2022 today. The update itself produced a milder February 2022 and not only that our 3 update rolling mean has shifted from 4.55C (-0.34C colder) to 5.20C (+0.31C milder) than the 1991-2020 February average. Looking less good for February 2022 now if this continues and in fact today's 3 update rolling mean for February 2022 is the mildest one so far.

March 2022 - March 2022 has been the most consistent to get a colder than average update and this week was no exception as it produced the month with the coldest anomaly again. Not only did we get a colder March 2022 update today we have in fact shifted the overall 3 update rolling mean for March 2022 further into colder territory. The change has been from 5.81C (-0.93C colder) last week to 5.08C (-1.66C colder) this week. This is thanks to the fact that update 9 was the sole mild March update and this is now no longer in the rolling mean.

Overall - A bit mixed overall news if you are a cold weather fan. Today's update itself was another milder than average one but the good news if you can call it this is despite the milder update the 3 update rolling mean for the overall updates average has in fact shifted in the direction of colder. Last week we were stood at 5.29C (-0.03C colder, more or less average really) to this week's 4.96C (-0.36C colder). This is thanks to update 12 being less mild than update 9 so this lowers the overall 3 update rolling average as a result.