October Pattern Suggests Stronger Winter 13-14 EPO Blocking Than NAO and AO

[bluewave]

The phase of the October NAO since 2002 has been a very reliable indicator of what the winter NAO would look like.
I have constructed three composites for the different states of the October NAO going back to 2002.
The negative NAO October years were 2002, 2003, 2004, 2005, 2006, 2009 , and 2010 which averaged -1.27.
The positive NAO October years of 2007 and 2011 averaged +0.42. October 2008 was near neutral and
averaged -0.04. You can see by looking at the composites below how reliable this relationship has
been since 2002.


-NAO October to winter composites






+NAO October to winter composites






Neutral NAO October to winter composites






It will be interesting to see if we see a similar relationship between this October and the coming winter.

[blizzardof09]

Very nice composition put together as usual bluewave. I know we've had blocking for a while now and as we head into october it looks to continue, but im still a little jittery about having it reverse back to a positive NAO regime as we head into the winter months or atleast not be as pronounced. I am eager to see what it looks like come late november because im really hoping we can have a much better winter than the last one. Maybe not a blockbuster like our recent three year streak but atleast a slightly above average one.

[uncle W]

the nao and ao charts are up and down since June...The lowest point was in June for both...The highs and lows for the AO/NAO are rising...I'd like to see the trend downward continue...It's predicted to rise again......

[blizzardof09]

the nao and ao charts are up and down since June...The lowest point was in June for both...The highs and lows for the AO/NAO are rising...I'd like to see the trend downward continue...It's predicted to rise again......

"if" that prediction holds some merit it may end up screwing us for the beginning of the winter. We need a good NAO/AO to establish itself or atleast show signs of it as we head into november/december. Doubt this winter will be as bad as last one though, that winter was a kick in the plums

[uncle W]

"if" that prediction holds some merit it may end up screwing us for the beginning of the winter. We need a good NAO/AO to establish itself or atleast show signs of it as we head into november/december. Doubt this winter will be as bad as last one though, that winter was a kick in the plums

looking back at last winter in retrospect it wasn't as bad as 1972-73, 2001-02 and 1997-98...The October storm (largest on record) was a 4" slush fest...We got another 4" storm in January and two dustings in February...1972-73's largest storm was 1.8"...2.8" for the season...2001-02 had one three inch storm in January and another dusting...1997-98 had a few dustings and a last minute 2-5" snowfall the first day of Spring...

[KEITH L.I]

12z GFS love that blocking near Greenland .much different than last year at this time

[SnoSki14]

Looks like the NAO will be near neutral as we enter the 1st week of October, but of course the NAO varies constantly so who really knows how it will be.

[earthlight]

Not worth all that much, but the NAO has been running generally on the negative side of normal since June 1

[earthlight]

the nao and ao charts are up and down since June...The lowest point was in June for both...The highs and lows for the AO/NAO are rising...I'd like to see the trend downward continue...It's predicted to rise again......

Just expanding on the post above -- the NAO has been fluctuating, but definitely has averaged more negative especially since June 1. It didn't really come near a positive departure until the last week and a half of June when it reached near neutral and then dropped again. The fluctuations continue now as we head into fall with a hard numbers lean towards the negative side.

You can see how the GEFS bring the NAO up over the next few days, with a breakdown of high latitude ridging and development of a more neutral NAO pattern.

http://www.meteo.psu.edu/~gadomski/ENSHGTAVGNH_0z/ensloopmref.html

[uncle W]

Not worth all that much, but the NAO has been running generally on the negative side of normal since June 1

the chart shows it's been negative most of the time but September had the highest positive number...If October gets a stronger positive spell I would start worrying...

[Isotherm]

Chris,

It may be because of the small sample size, but I've actually found a stronger negative correlation b/t the Oct NAO and ensuing winter. I think it's about 63-66% of Octobers with a +NAO feature a winter -NAO. It seems the past decade that correlation has broken down a bit as you've correctly illustrated above. I did some more research after last winter and found that November has a fairly strong positive correlation with its NAO modality and DJF -- about 68% of Novembers with a -NAO featured a winter -NAO, and the same story percentage wise with the AO. Once into December, the positive correlation is about 88% b/t the Dec NAO and DJF. Basically I think it's a matter of a certain high latitude pattern locking in place by mid/late Nov and particularly by early December. I'm going to wait longer this fall to give thoughts on the winter b/c I think Nov is very important. Also it helps to be able to see into the beginning of December - not always - we've seen some +NAO Nov/Dec couplets followed by -NAO JFM. But long range forecast is all about correlations, persistence, and analogs right...

[famartin]

the chart shows it's been negative most of the time but September had the highest positive number...If October gets a stronger positive spell I would start worrying...

Yes, draw a straight line to smooth out all the bumps and you get a less than pleasant trend.

[nzucker]

Chris,

It may be because of the small sample size, but I've actually found a stronger negative correlation b/t the Oct NAO and ensuing winter. I think it's about 63-66% of Octobers with a +NAO feature a winter -NAO. It seems the past decade that correlation has broken down a bit as you've correctly illustrated above. I did some more research after last winter and found that November has a fairly strong positive correlation with its NAO modality and DJF -- about 68% of Novembers with a -NAO featured a winter -NAO, and the same story percentage wise with the AO. Once into December, the positive correlation is about 88% b/t the Dec NAO and DJF. Basically I think it's a matter of a certain high latitude pattern locking in place by mid/late Nov and particularly by early December. I'm going to wait longer this fall to give thoughts on the winter b/c I think Nov is very important. Also it helps to be able to see into the beginning of December - not always - we've seen some +NAO Nov/Dec couplets followed by -NAO JFM. But long range forecast is all about correlations, persistence, and analogs right...

Watching the stratospheric temperatures in November will be key. Nov '09 and '10 featured a huge increase in temperatures around 5-10mb in the upper atmosphere, and this coincided with an extremely potent -NAO/-AO regime. Nov '11 had the opposite tendency in the stratosphere, and the winter was the polar opposite of the two preceding cold seasons with a stubbornly positive NAO and EPO. It took the Arctic Oscillation under February to go negative last winter, and then the blocking was clearly on the wrong side of the pole. If we do witness high-latitude blocking this November, we also need to take a look at the location.

[Isotherm]

Watching the stratospheric temperatures in November will be key. Nov '09 and '10 featured a huge increase in temperatures around 5-10mb in the upper atmosphere, and this coincided with an extremely potent -NAO/-AO regime. Nov '11 had the opposite tendency in the stratosphere, and the winter was the polar opposite of the two preceding cold seasons with a stubbornly positive NAO and EPO. It took the Arctic Oscillation under February to go negative last winter, and then the blocking was clearly on the wrong side of the pole. If we do witness high-latitude blocking this November, we also need to take a look at the location.

Agreed. Solar will also be important to track the next few months. Watch for any spikes or declines in solar flux and geomagnetic activity, as we saw the former occur last fall and it was one of many unfavorable factors leading to the ragion arctic vortex.

[bluewave]

So far we are starting off October with more of a blocking pattern than we had last year.

The NAO has been somewhat negative for the beginning of the month. It is forecast

to go briefly positive and then drop down to negative values again.

Expanding the conversation to the AO aspect of blocking, the GFS is forecasting a strong drop

over the next week. The GEFS are hinting that we will see an AO drop down below -2. I found

some AO values since 2002 for October that dropped below -2.

10/23/10....-2.555

10/11/09....-2.666

10/17/06....-3.192

10/18/04....-2.377

10/16/03....-3.257

10/18/02....-5.098

It will be interesting to see how the forecast verifies and what the pattern for the rest of the

month looks like.

[Sundog]

All winners except 06. How was November during those years?

[bluewave]

All winners except 06. How was November during those years?

Some of the Novembers varied from the Octobers and others were similar.

The interesting point about 06-07 was that the blocking translated into cold for February.

But the Valentine's Day Storm was sleet and freezing rain. So a solid blocking pattern

for even part of the winter doesn't always translate into a snowy one for us.

I would much rather a blocking pattern though to at least have a shot at a decent

snowstorm even if the pattern can't deliver for us.

[Sundog]

Some of the Novembers varied from the Octobers and others were similar.

The interesting point about 06-07 was that the blocking translated into cold for February.

But the Valentine's Day Storm was sleet and freezing rain. So a solid blocking pattern

for even part of the winter doesn't always translate into a snowy one for us.

I would much rather a blocking pattern though to at least have a shot at a decent

snowstorm even if the pattern can't deliver for us.

Yup the turnaround around mid January was dramatic. If that VD storm produced snow instead that winter would have been looked upon differently. Regardless of the actual results that winter was still much better than the following debacle of 07-08. That was a 10 day winter.

Agree on the blocking btw. It's better to at least have a shot at some snow. 07-08 showed us what happens when we don't.

[Alpha5]

The way things are looking over Alaska.......we are so screwed

[supermeh]

The way things are looking over Alaska.......we are so screwed

lol

[bluewave]

The models have been becoming more bullish on the blocking over the last few days.

[blizzardof09]

We need to see these kinds of forecasts come to fruition by late november/december. Yes it is nice or would be nice to see them work in tandem but i want to see it this way in a month and a half before getting excited. You are right though past few days they have been becoming more bullish as far as more negative nao/ao departures

[bluewave]

We need to see these kinds of forecasts come to fruition by late november/december. Yes it is nice or would be nice to see them work in tandem but i want to see it this way in a month and a half before getting excited. You are right though past few days they have been becoming more bullish as far as more negative nao/ao departures

My early guess right now is that we'll have blocking patterns to work with at some point this winter.

But it's tough to tell this soon if it will turn out like a 06-07 blocking pattern with little snow or the other

years that did better. So as always, we'll have to take a wait and see approach on the snowfall potential.

[blizzardof09]

Wait and see is right. Im actually concerned about the ENSO and if we can stay positive and if we can also get the pacific to cooperate at crucial times this winter. We all know we can have a great west-based -NAO/-AO but if that pacific doesnt do squat the snowfall may be hard to come by. I short bluewave its gonna be an interesting 4 weeks to see where all of our chips fall even outside the nao/ao, im actually keeping a close eye on our snow buildup north of the border as well.

[uncle W]

he AO is at its lowest point in months...I like what I see...so far so good...

[Kaner587]

Regardless of the final outcome we can say with certainty that this fall is unfolding quite differently than last. What implications this will have is anyone's guess. But after the Halloween storm everyone here began freaking out when in nov and dec it seemed like fall never ended. My amateur opinion is that we will have much more cold air to work with this upcoming winter. It remains to be seen if we can couple good blocking (assuming we get it at all) with an active storm track. I think at the minimum it's a near normal winter in terms of snow...at worst slightly below. Well see what happens.

[Isotherm]

The fact that the -NAO has been so persistant over the past several months has me concerned that it'll break down at the worst time. Blocking this month is nice and all - finally a normal autumn progression - but it doesn't get me excited for winter. We'll see what the N Hemisphere looks like 3-4 weeks from now.

[blizzardof09]

The fact that the -NAO has been so persistant over the past several months has me concerned that it'll break down at the worst time. Blocking this month is nice and all - finally a normal autumn progression - but it doesn't get me excited for winter. We'll see what the N Hemisphere looks like 3-4 weeks from now.

Absolutely right isotherm, the nao has to reverse sometime in the future and im worried its gonna be when we need it, in december through february. Ive been voicing this same concern and although we arent in a deeply negative depature its been predominantely a -NAO regime with some brief spikes to positive territory. This is one of the teleconnectors im worried about as we head into november as to see what its gonna do when it matters to us

[Neblizzard]

The fact that the -NAO has been so persistant over the past several months has me concerned that it'll break down at the worst time. Blocking this month is nice and all - finally a normal autumn progression - but it doesn't get me excited for winter. We'll see what the N Hemisphere looks like 3-4 weeks from now.

What I do like is the very warm waters near Greenland so far this year. That can be conducive to frequent blocking over the next several months. Definitely a different look than last year..

[NYCSuburbs]

The way things are looking over Alaska.......we are so screwed

Alaska's not looking too good, although at least considering that they had periods of ridging as well it's definitely an improvement over last year (almost anything is an improvement compared to that), and the NAO continues to remain generally negative. One of my concern as others have also stated is that the -NAO and -AO, after persisting for so long, fall apart at the wrong time. It took the pattern until late March to change which by then it was too late for winter to begin, we spent most of the summer with a -NAO, and the only thing worse would be if a +NAO and +AO return again just in time for winter. We'll have to see where that goes along with the Alaska and NE Pacific pattern but I'm somewhat optimistic at this time, especially with the periods of occasional blocking.