Negative NAO coming?

[NaoPos]

Based on the state of the stratosphere, I wouldn't be surprised if there is limited blocking until February, perhaps the whole winter.

I assume you're talking about how cold it is?

[CAD_Wedge_NC]

Based on the state of the stratosphere, I wouldn't be surprised if there is limited blocking until February, perhaps the whole winter.

Let me know how that forecast works out for you..........As you well know, blocking is something that can show up very quickly on the models (within two weeks). I can't believe you are going to base an entire winter forecast on the current state of the stratosphere in mid-November.

[HM]

I thought September's 50mb QBO number was peak but the October number is now peak and quite amazing:

2011 6.00 6.02 6.31 6.25 8.24 9.30 9.35 9.06 10.00 11.46

Here are the latest solar flux values:

2011 834 946 1158 1125 958 958 941 1017 1345 1372

And the ap index

2011 6 6 8 9 9 8 8 7 12 7

The state of the stratosphere is very much acting like the research of HT currently with a very cold stratospheric vortex / +AO. The temperatures are coldest in the lower levels

(50-70mb) while 30-10mb is a bit warmer.

We need to get beyond this recent flare-up in solar activity before we can get back to a more conducive blocking pattern (+QBO / higher solar correlations won't work this

winter and especially in early winter):

Interestingly, the MJO has had a speed that has at the very least surprised me. Someone pull the plug on it already! A phase 7-8-1 response in mid-November is not a good

thing for cold lovers, esp. during a cold ENSO. This time of year becomes very tricky assessing how the MJO will affect circulation since the overall jet stream is in the

process of going into "winter mode." Anyway, this autumn, the EPO goes positive during +AAM tendencies/global mountain torques. These periods have had a weakened

Aleutian High. It may not be a bad thing getting the forcing back into phase 2-5 to allow the Aleutian High to rebuild.

One possibiliy is that we are heading for a relative max in the AAM in December or even early January and this may keep the MJO moving quickly. While ENSO is saying, "get

back to where you belong," the state of the stratosphere is saying just the opposite. These conflicting factors may be why the MJO is doing what it is doing but this is only a

hunch. This will pay off down the road because the same factors causing the warmth now will become favorable for split flow / +PNA/-NAO.

[HM]

Interestingly, there are some decent similarities to 1999-2000 and 1975-76.

-Both had lower stratospheric winds over the equator that were positive (50-100mb)

-Both were second/third year La Niña events

-Both had a similar pattern to the Nov and predicted Dec MJO forcing with 1975 being a better match

2011 has a stronger +QBO and weaker solar/geomagnetic state than both years. It is also weaker with La Niña, too.

Apym 1999 10 12 14 12 8 7 10 15 19 19 14 10 12.5

Apym 2000 13 16 9 15 15 15 21 16 18 18 17 7 15.0

Apym 1975 16 18 20 16 13 11 12 10 10 12 18 12 13.9

Apym 1976 13 17 23 17 14 10 9 9 13 12 9 10 12.9

Apym 2010 3 5 5 10 8 7 5 8 5 6 5 4 0.0

Apym 2011 6 6 8 9 9 8 8 7 12 7 . . 0.0

I suspect when solar activity drops in January, like it did in 2000, the NAO / AO will be extremely negative for a time. In terms of December, both 1975 and 1999 had a decent

-NAO develop 12/15-20. They significantly diverge in general circulation for the CONUS in early December, however. This is a very noisy time as we transition to winter and

there are a wide range of possibilities for 2011.

While ending November on a warm note seems like a given, the North Pacific will be in the process of retrograding. This may give rise to the PNA in early December. So while

a full blown Arctic Attack may not be in the cards, a general PNA pattern is very possible as the overall N PAC continues to retrograde. Perhaps this ends up being brief as the

MJO continues to send us "bad signals" through mid-December. Maybe the SE ridge returns for a while before the development of a -NAO takes the heights down.

[skierinvermont]

Let me know how that forecast works out for you..........As you well know, blocking is something that can show up very quickly on the models (within two weeks). I can't believe you are going to base an entire winter forecast on the current state of the stratosphere in mid-November.

As I showed in the other thread, a November with a top 10 cold stratosphere as we have now has an AO in January that is nearly +2 higher than a.warm stratospheres. If the stratosphere remains cold for a few more weeks then the disparity grows to +3 and the chance of a -AO falls to 10% or less. The correlation is quite strong and thus far the stratosphere remains in a classic pre +AO state both in terms of overall temperature and the stratospheric pattern. I will let you know how the forecast works out.

I found another stratospheric temperature data set that goes back to 1950. This time I focused on the area 50-90N 90E-150W (basically Russia and surrounding areas) where the correlation is strongest.

I used 70mb stratospheric temps from the NCEP reanalysis: http://www.esrl.noaa.../timeseries1.pl

Based on this I would give us at least a 75% chance of having a +AO in December+January. If the stratosphere remains near record cold for the next 2-3 weeks, our chances diminish even further. There has never been a significantly -AO January following a top 10 cold stratosphere.

November stratosphere

-The December AO was 1.09 higher following the 10 coldest than the 10 warmest.

-The January AO was 1.75 higher following the 10 coldest than the 10 warmest.

-The December AO was .63 higher following cooler than average than warmer than average

-The January AO was 1.71 higher following cooler than average than warmer than average

November + December stratosphere

-The December AO was 1.82 higher following the 10 coldest than the 10 warmest

-The January AO was 2.81 higher following the 10 coldest than the 10 warmest

-The December AO was .72 higher following cooler than average than warmer than average

-The January AO was 1.41 higher following cooler than average than warmer than average

- 8/10 coldest had +AO Dec, only 1 below -.1

- 8/10 coldest had +AO Jan, none below -.2

-9/10 warmest had -AO Dec, none above +.2

-9/10 warmest had -AO Jan, none above +.3

For reference this is what this Oct 15 - Nov 15 looked like this year:

Which matches very well to the November stratosphere preceding +AOs. The following is a correlation between the November stratosphere temperature and the subsequent January AO.

In addition, if we look higher in the stratosphere at 20mb the spatial pattern of anomalies 10/15-11/15 has matched that of other Novembers preceding +AO December and Januaries. The similarity is astonishing. The current stratosphere is in a classic "pre +AO pattern."

10/15-11/15 20mb temps this year:

November 20mb temp correlation to subsequent AO:

[Lookout]

Nothing to add except to say this is a fantastic thread. Great stuff everyone and thank you for it.

[usedtobe]

skierinvermont

"As I showed in the other thread, a November with a top 10 cold stratosphere as we have now has an AO in January that is nearly +2 higher than a.warm stratospheres. If the stratosphere remains cold for a few more weeks then the disparity grows to +3 and the chance of a -AO falls to 10% or less. The correlation is quite strong and thus far the stratosphere remains in a classic pre +AO state both in terms of overall temperature and the stratospheric pattern. I will let you know how the forecast works out."

The strength of the stratospheric westerly with the polar night jet does worry me some. The current state suggests that the NAM may be in the state that does favor a positive AO through most of the winter. However, the AP index which also correlates to the AO and NAO is low which favors a negative nao and the atlantic ssta pattern also would try to nudge us towards a negative index. The conflicting signs, including the October snow cover which was pretty neutral, suggests the amount of blocking is a tough call. Initially, I think any regime change will be driven by the vortex over AK getting displaced westward allowing ridging to take place across western NA giving us at least a period albeit maybe not a long one, with a pna pattern.

[uncle W]

Interestingly, there are some decent similarities to 1999-2000 and 1975-76.

-Both had lower stratospheric winds over the equator that were positive (50-100mb)

-Both were second/third year La Niña events

-Both had a similar pattern to the Nov and predicted Dec MJO forcing with 1975 being a better match

2011 has a stronger +QBO and weaker solar/geomagnetic state than both years. It is also weaker with La Niña, too.

Apym 1999 10 12 14 12 8 7 10 15 19 19 14 10 12.5

Apym 2000 13 16 9 15 15 15 21 16 18 18 17 7 15.0

Apym 1975 16 18 20 16 13 11 12 10 10 12 18 12 13.9

Apym 1976 13 17 23 17 14 10 9 9 13 12 9 10 12.9

Apym 2010 3 5 5 10 8 7 5 8 5 6 5 4 0.0

Apym 2011 6 6 8 9 9 8 8 7 12 7 . . 0.0

I suspect when solar activity drops in January, like it did in 2000, the NAO / AO will be extremely negative for a time. In terms of December, both 1975 and 1999 had a decent

-NAO develop 12/15-20. They significantly diverge in general circulation for the CONUS in early December, however. This is a very noisy time as we transition to winter and

there are a wide range of possibilities for 2011.

While ending November on a warm note seems like a given, the North Pacific will be in the process of retrograding. This may give rise to the PNA in early December. So while

a full blown Arctic Attack may not be in the cards, a general PNA pattern is very possible as the overall N PAC continues to retrograde. Perhaps this ends up being brief as the

MJO continues to send us "bad signals" through mid-December. Maybe the SE ridge returns for a while before the development of a -NAO takes the heights down.

1975 was mild until mid December...It turned colder (very cold at times) into February...There were brief warm ups and no sustained cold...Late February saw 70 degrees in our area and March continued the up and down pattern...Snowfall was light...1999-00 didn't get cold until mid January when a sustained cold and snowy pattern set in that lasted into February...Very cold at times...It got warm again in late February and it continued thru March...snowfall was light...1975-76 was the colder snowier but hardly a good one in our area...1999 probably is the better analog as of now...Maybe a January 2000 replay...I'm liking 1974-75 and 1971-72 more as analogs...February was the snowiest months for those years while December into January were not...

[WxMidwest]

Skier Vermont, That is pretty neat stuff, although I would hate to have a consistently +AO.

Here is a graphic that was just constructed, I don't think all hope is lost, but there is a difference between them if you categorize them for ENSO. Also, IF you take a look at the QBO, if it's Below -1.5 it seems to make a difference, via past research I've done in the past with QBO value/trend/ENSO matrices has shown that values between -1.5 and 5.5 (Neatral), Above 5.5 (High), and Below -1.5(Low) using -1.5 and 5.5 as critical points. In that (Low) category include 1983, 1989, 1967, 1988, 1986. QBO.DAT file has 2011 below that -1.5 critical point already...

[Amped]

Lol 26th-30th of every month something bizzare happens.

But 80kt SE LLJ is normal for most areas so I guess not this month

[chionomaniac]

One has to say that there are conflicting signals for the coming winter especially from the stratosphere. The evidence that skiinvermont produces regarding the 70 hPa temperatures and the following AO seems pretty conclusive, and if one was a betting man then it would be unwise to bet against a positive AO for December and January.

This to me fits in with some thoughts from across the water, however there does appear to be hope later on in the winter. I have suspicions that we may actually get a SSW in January that will lead to a negative AO in late January and February. Firstly though, I think that we will need to see a reduction in the remaining residual westerly QBO from the lower tropical stratosphere that will alter the whole composition of the stratosphere.

These winds can still be seen here:

These have been reducing during the last month.

This recent study suggests to me that there are good possibilities for a SSW in January.

http://www.agu.org/p...GL045756.shtmle

"The variability in the number of major sudden stratospheric warmings (SSWs) is analyzed in a multi-century simulation under constant forcing using a stratosphere resolving atmosphere-ocean general circulation model. A wavelet-analysis of the SSW time series identifies significantly enhanced powers at a period of 52 years. The coherency of this signal with tropospheric and oceanic parameters is investigated. The strongest coherence is found with the North Atlantic ocean-atmosphere heat-flux from November to January. Here, an enhanced heat-flux from the ocean into the atmosphere is related to an increase in the number of SSWs. Furthermore, a correlation is found with Eurasian snow cover in October and the number of blockings in October/November. These results suggest that the multi-decadal variability is generated within the ocean-troposphere-stratosphere system. A two-way interaction of the North Atlantic and the atmosphere buffers and amplifies stratospheric anomalies, leading to a coupled multi-decadal mode.

• 
• 
• 

Figure 3 of 3"

There is a better chance of stratospheric feedback later on in winter if we have good Autumnal Eurasion snowcover (achieved) and enhanced North Atlantic heat flux from the ocean. This is already significantly increased during November.

See post from Glacier Point here http://forum.netweat...2/page__st__140

Presently the cool stratosphere is creating a pretty resilient polar vortex 'surf zone' that is proving hard to break, however we are now seeing an encouraging build of ozone around this surf zone that augers well for later on as more attempts of wave breaking from deflected Rossby waves after MTs introduce ozone into the vortex destabilising it. At the start of winter I was unsure about how strong the BDC would be this year as we are mid solar cycle, but it looks to be picking up.

This study here http://www.columbia....Volume-2010.pdf suggests that we need to keep an eye on the Northern annular mode (NAM) at 150 hPa as this will give us a better idea of how the AO is likely to respond in the following weeks - better evidently than tropospheric indications. The only problem here is that I can't seem to find NAM readings at 150 hPa!

I certainly would be surprised if December and early January had an AO of anything other than positive, but from mid January on I think that the chances of a negative NAO increase dramatically, especially if we have a SSW on our hands.

c

[skierinvermont]

Great post - agree regarding the February and perhaps late January AO. Given the factors you mentioned that seems to be the period that is most likely to see a -AO. Also the cold Russian stratosphere statistics I presented showed very little correlation between November and/or December and the February AO. I found it interesting that November correlates well with a 2 month lead to January, but December does not correlate well at all to February with the same lead time. Perhaps there is a tendency for the dam to break in February due to some of the factors you mentioned?

Also can you point me to the data showing the build up in ozone you mentioned?

[nzucker]

Almost every -AO summer was followed by a -AO winter, and Summer 2011 had an AO of -0.8 so we should be in decent shape.

[chionomaniac]

Great post - agree regarding the February and perhaps late January AO. Given the factors you mentioned that seems to be the period that is most likely to see a -AO. Also the cold Russian stratosphere statistics I presented showed very little correlation between November and/or December and the February AO. I found it interesting that November correlates well with a 2 month lead to January, but December does not correlate well at all to February with the same lead time. Perhaps there is a tendency for the dam to break in February due to some of the factors you mentioned?

Also can you point me to the data showing the build up in ozone you mentioned?

Frustratingly I am having difficulty logging on to cpc sites intermittently. If you find the cpc stratosphere home page, current and previous ozone levels can be found from there. There is a five day forecast available towards the bottom of the forecast and analyses page.

[skierinvermont]

Almost every -AO summer was followed by a -AO winter, and Summer 2011 had an AO of -0.8 so we should be in decent shape.

The primary mechanism for this appears to be that the stratosphere remains very warm following -AO summers. The following is a composite of the Novembers following the top 10 most -AO summers. Notice the large warm anomalies in the polar stratosphere, especially over Siberia (+4C anomalies in the stratosphere are large for even a single year, nevermind a 10 year composite). The second image is November thus far this year, which is essentially the exact opposite.

For this reason and the strong correlation I have noted between a cold November stratosphere and a +AO in December and January (see my quoted post a page back), I believe this year will be an exception to the correlation you note. The mechanism by which it operates appears to not be applicable this year.

I also checked each of the years in the composite individually, and all 10 had a warm stratosphere, usually centered over the Siberian coast. This would make 2011 the ONLY top 10 -AO summer to be followed by a cold stratosphere in November.

I also checked -AO summers ranked 11-15 and they ALL also had warm stratospheres in November usually over the Siberian coast. #16, 2007, is the first -AO summer I found that was followed by a cold stratosphere in November in Siberia (like this year). 2007 also is one of the only ones to have a +AO winter. I believe 2011 will follow 2007. 1956 also had a mildly -AO summer, followed by a cold stratosphere in November and a +AO winter.

I also checked (not pictured) higher levels of the stratosphere and the effect is even stronger. At 30mb the 10 november composite is entirely 3-7C above average in the polar stratosphere with the strongest 6-7C anomalies over the northern Siberia coast. This year is again essentially the opposite with widespread 4-7C negative anomalies, with the strongest centered over Siberia.

[HM]

Skier, you hardly have any La Nina events on there which significantly impacts lower stratospheric temperatures in the polar regions. You do have 1967 and that year did have a cool anomaly over Siberia....perhaps not to the extent of 2011, but this year has a tremendous +QBO at 50mb ongoing.

[skierinvermont]

Skier, you hardly have any La Nina events on there which significantly impacts lower stratospheric temperatures in the polar regions. You do have 1967 and that year did have a cool anomaly over Siberia....perhaps not to the extent of 2011, but this year has a tremendous +QBO at 50mb ongoing.

Actually that's 1987 (tough to read I know). 1967 had a +AO summer.

I'll expand my sample size and/or look only at -AO summers with -ENSO fall/winter and see what happens. I did mention 2007 which falls at #16 on most -AO summers and that was a -ENSO fall/winter and had a +AO winter. But I didn't include that in my composite of top 10. Apparently the top 10 -AO summers were all neutral/+ENSO years.

1960 was in the composite of top 10 -AO summers and like the rest had a very warm November stratosphere centered over Siberia. It was a negative neutral ENSO year and had a -AO winter.

[HM]

The idea of a SSW this January has been something I have liked for a while now. All the years with a setup similar to 2011-12 had a substantial SSW/MMW and some of my favorite years had it in January. It is quite possible that a majority of January and February come in cooler than normal across the eastern US, but it depends on how fast this all occurs.

Some of you are arguing for a late January response, which is perfectly reasonable. However, if the MJO continues to remain faster than normal, you are going to get a tropical boost much sooner than that in the month, possibly jump-starting the SSW.

Whenever this period occurs, it will have significant cold / snow and be similar to the last couple of years' outcomes in terms of wintry extremes. The potential exists for historic snow / cold with this particular round of -AO and the timing of it couldn't be better (or worse) for significant cold.

[HM]

Actually that's 1987 (tough to read I know). 1967 had a +AO summer.

I'll expand my sample size and/or look only at -AO summers with -ENSO fall/winter and see what happens. I did mention 2007 which falls at #16 on most -AO summers and that was a -ENSO fall/winter and had a +AO winter. But I didn't include that in my composite of top 10. Apparently the top 10 -AO summers were all neutral/+ENSO years.

Oh okay gotcha. Yeah, you are rarely going to see very warm 70mb temperatures in well-defined La Nina events during the autumn across the polar areas, especially with a peaking +QBO wave.

Either way, I do like the idea of a major turn-around in January in terms of the NAM.

[chionomaniac]

The primary mechanism for this appears to be that the stratosphere remains very warm following -AO summers. The following is a composite of the Novembers following the top 10 most -AO summers. Notice the large warm anomalies in the polar stratosphere, especially over Siberia (+4C anomalies in the stratosphere are large for even a single year, never mind a 10 year composite). The second image is November thus far this year, which is essentially the exact opposite.

For this reason and the strong correlation I have noted between a cold November stratosphere and a +AO in December and January, I believe this year will be an exception to the correlation you note. The mechanism by which it operates appears to not be applicable this year.

I also checked each of the years in the composite individually, and all 10 had a warm stratosphere, usually centered over the Siberian coast. This would make 2011 the ONLY top 10 -AO summer to be followed by a cold stratosphere in November.

I also checked -AO summers ranked 11-15 and they ALL also had warm stratospheres in November usually over the Siberian coast. #16, 2007, is the first -AO summer to be followed by a cold stratosphere in November in Siberia. 2007 also is one of the only ones to have a +AO winter.

I also checked (not pictured) higher levels of the stratosphere and the effect is even stronger. At 30mb the 10 november composite is entirely 3-7C above average in the polar stratosphere with the strongest 6-7C anomalies over the northern Siberia coast. This year is again essentially the opposite with widespread 4-7C negative anomalies, with the strongest centered over Siberia.

I may be in agreement with your belief of a positive AO for the first half of winter ski, but not necessarily this reasoning. Firstly when looking at the stratosphere I think we should be concentrating on the middle levels (10-50 hPa) - this is the driving force that affects lower altitudes. One of the largest reasons imo that we have a super cold stratosphere this autumn, is a knock on from the extremely low levels of ozone since the record low last spring. This, I feel helps explain why the - AO summer is the exception to the rule. In essence the stratosphere has taken a large time to recover, and it is only recently that we have seen the Brewer Dobson circulation bring up levels surrounding the stratospheric polar vortex up to something near normal.. But that looks too late for the first half of this winter. If we see a further increase in these ozone levels during the coming weeks then I feel that we will have a loaded gun situation later on in winter. The cold strong polar vortex would be primed to be broken at this point.

The decaying wQBO has not helped in the build up to this winter and I believe that we are always better off starting winter with no tropical residual westerly winds present, but there is still a lot to be learnt about the precise timing of QBO lower stratosphere changeover.

There is still a lot to be learnt about stratospheric/tropospheric coupling interactions. The Eurasion snow cover has been shown by Cohen et al to be an important feedback mechanism, but it is not a definitive science and can still be overridden. The strong polar vortex will take some breaking this winter and I suspect a lot of patience will be needed by those waiting for the break.

[skierinvermont]

OK HM here is a composite of the November stratosphere following the top 25 -AO summers ONLY -ENSO fall/winters. You can see the warm stratosphere signal still persists. Of these 8 years, 5 had significantly -AO winters, 2 were near neutral (1956, 2008) and 1 was significantly positive (2007). 1956, 2008, and 2007 also had the coldest stratospheres, unlike the other 5. The one +AO year, 2007, had the coldest stratosphere of all. Thus again 2011 bears more resemblance to the years that buck the '-AO summer = -AO winter' rule, even when we restrict ourselves to -ENSO years. For this reason I believe the -AO summer = -AO winter rule is not applicable this year.

[skierinvermont]

I may be in agreement with your belief of a positive AO for the first half of winter ski, but not necessarily this reasoning. Firstly when looking at the stratosphere I think we should be concentrating on the middle levels (10-50 hPa) - this is the driving force that affects lower altitudes. One of the largest reasons imo that we have a super cold stratosphere this autumn, is a knock on from the extremely low levels of ozone since the record low last spring. This, I feel helps explain why the - AO summer is the exception to the rule. In essence the stratosphere has taken a large time to recover, and it is only recently that we have seen the Brewer Dobson circulation bring up levels surrounding the stratospheric polar vortex up to something near normal.. But that looks too late for the first half of this winter. If we see a further increase in these ozone levels during the coming weeks then I feel that we will have a loaded gun situation later on in winter. The cold strong polar vortex would be primed to be broken at this point.

The decaying wQBO has not helped in the build up to this winter and I believe that we are always better off starting winter with no tropical residual westerly winds present, but there is still a lot to be learnt about the precise timing of QBO lower stratosphere changeover.

There is still a lot to be learnt about stratospheric/tropospheric coupling interactions. The Eurasion snow cover has been shown by Cohen et al to be an important feedback mechanism, but it is not a definitive science and can still be overridden. The strong polar vortex will take some breaking this winter and I suspect a lot of patience will be needed by those waiting for the break.

I'm not proposing a mechanism for the cold stratosphere - whether it is low snowcover or low levels of ozone or something else or a combination I don't know. All I know is that it exists, that it is unusual if not unprecedented following a -AO summer (thus the -AO summer = -AO winter rule does not apply), and that it correlates strongly with a +AO December and January.

[chionomaniac]

I'm not proposing a mechanism for the cold stratosphere - whether it is low snowcover or low levels of ozone or something else or a combination I don't know. All I know is that it exists, that it is unusual if not unprecedented following a -AO summer, and that it correlates strongly with a +AO December and January.

Fair enough, I certainly agree with that. However, as a thought, if it is unprecedented can we question the following winter correlation?

I suspect we can question, but like you, unless we see a dramatic early season stratospheric change, then we are looking at the positive AO.

[HM]

OK HM here is a composite of the November stratosphere following the top 25 -AO summers ONLY -ENSO fall/winters. You can see the warm stratosphere signal still persists. Of these 8 years, 5 had significantly -AO winters, 2 were near neutral (1956, 2008) and 1 was significantly positive (2007). 1956, 2008, and 2007 also had the coldest stratospheres, unlike the other 5. The one +AO year, 2007, had the coldest stratosphere of all. Thus again 2011 bears more resemblance to the years that buck the '-AO summer = -AO winter' rule, even when we restrict ourselves to -ENSO years. For this reason I believe the -AO summer = -AO winter rule is not applicable this year.

Thanks. Did you mean to do it at 30mb?

[Glacier Point]

The idea of a SSW this January has been something I have liked for a while now. All the years with a setup similar to 2011-12 had a substantial SSW/MMW and some of my favorite years had it in January. It is quite possible that a majority of January and February come in cooler than normal across the eastern US, but it depends on how fast this all occurs.

Some of you are arguing for a late January response, which is perfectly reasonable. However, if the MJO continues to remain faster than normal, you are going to get a tropical boost much sooner than that in the month, possibly jump-starting the SSW.

Whenever this period occurs, it will have significant cold / snow and be similar to the last couple of years' outcomes in terms of wintry extremes. The potential exists for historic snow / cold with this particular round of -AO and the timing of it couldn't be better (or worse) for significant cold.

I like this idea alot.

That high amplitude phase 8-1-2 MJO phase in late October really caught the eye and told us alot about where the atmosphere was at and where it wants to go. Most years when these October / November strong phase 1-2 projections were +AAM. Of the two low AAM years, a similar net result suggesting a big turnaround in January.

Additionally we have continued eastward propagating MJO and an AAM state which is running ahead of where it should be given the oceanic signal.

Given the QBO state and solar flux suggesting middle part of winter for a relaxation in zonal winds and a possible westerly wind burst timed for late December, I wonder, a tropospheric lead warming being followed up with the upper atmosphere following the lead. Kind of like 1984/5.

[skierinvermont]

Thanks. Did you mean to do it at 30mb?

Oh, no my mistake, I've been posting 70mb for consistency but also looking at 30mb (it's always very similar) and forgot to switch back. So here's 70mb. Very similar, and very unlike this year. With again 1956, 2007, and 2008 being cooler than the rest and having more neutral/+AO winters. 2007 being the coldest and most +AO.

[uncle W]

Almost every -AO summer was followed by a -AO winter, and Summer 2011 had an AO of -0.8 so we should be in decent shape.

from the NYC forum...

back in August we had the 3rd lowest August AO monthly reading since 1950...Here is a list of years with the lowest August monthly index and the following winters lowest monthly index...15 of 17 years listed had a winter month with a lower index...Two of the five la nina years had a higher index...reds are El nino years and blue la Nina years...Black's are neutral...The AO is now positive since August...1974 and 1999 are the only years the AO index was higher during the winter months...Some other years saw a positive AO after August...1977 was one...that was an el nino year though...1964 went positive for a month in October but slipped back negative by November...

year......August AO....low winter AO

1977..........-1.412..........-3.014 Feb...

1964..........-1.207..........-2.084 Feb...

2011..........-1.063..........????

1960..........-1.008..........-1.506 Jan...

1966..........-0.945..........-1.401 Dec...

1950..........-0.851..........-1.928 Dec...

1987..........-0.836..........-1.066 Feb...

1986..........-0.826..........-1.473 Feb...

1958..........-0.755..........-2.013 Jan...

1959..........-0.745..........-2.484 Jan...

1969..........-0.728..........-2.412 Jan...

2004..........-0.720..........-1.271 Feb...

1999..........-0.672.........+1.076 Feb...

1968..........-0.671..........-3.114 Feb...

1956..........-0.652..........-1.513 Feb...

1963..........-0.625..........-1.178 Dec...

1974..........-0.533.........+0.194 Feb...

[brad1551]

Almost every -AO summer was followed by a -AO winter, and Summer 2011 had an AO of -0.8 so we should be in decent shape.

Amen to that note. Just going to take a little longer than usual this year.

[LithiaWx]

from the NYC forum...

back in August we had the 3rd lowest August AO monthly reading since 1950...Here is a list of years with the lowest August monthly index and the following winters lowest monthly index...15 of 17 years listed had a winter month with a lower index...Two of the five la nina years had a higher index...reds are El nino years and blue la Nina years...Black's are neutral...The AO is now positive since August...1974 and 1999 are the only years the AO index was higher during the winter months...Some other years saw a positive AO after August...1977 was one...that was an el nino year though...1964 went positive for a month in October but slipped back negative by November...

year......August AO....low winter AO

1977..........-1.412..........-3.014 Feb...

1964..........-1.207..........-2.084 Feb...

2011..........-1.063..........????

1960..........-1.008..........-1.506 Jan...

1966..........-0.945..........-1.401 Dec...

1950..........-0.851..........-1.928 Dec...

1987..........-0.836..........-1.066 Feb...

1986..........-0.826..........-1.473 Feb...

1958..........-0.755..........-2.013 Jan...

1959..........-0.745..........-2.484 Jan...

1969..........-0.728..........-2.412 Jan...

2004..........-0.720..........-1.271 Feb...

1999..........-0.672.........+1.076 Feb...

1968..........-0.671..........-3.114 Feb...

1956..........-0.652..........-1.513 Feb...

1963..........-0.625..........-1.178 Dec...

1974..........-0.533.........+0.194 Feb...

I really like your posts I'd like to say first off, said posts are always informative in one form or another. This post gives me some hope for the upcoming winter. Is the first line of your data wrong? You list 1977 as a positive AO for winter following a negative in August. The 1977 line lists a negative winter low AO, the second most negative in your data set. Was 1977 really that volatile where it saw a -3 AO but also had an average of positive for the winter?

[usedtobe]

Some really good posts. Chionomaniac, I like your reasoning and think it does argue for the ao to average in the positive range through dec and into Jan. However, if the AK vortex gets displaced, there still can be transitory cold shots in an otherwise crappy pattern. I like the figure showing how snow cover might impact upon the nao.