Winter 2011-2012 trend/forecast discussion.

[John1122]

With the general summer pattern well in place of hot/pop up t-storm/hot I am starting to get the itch to look at the pattern for the upcoming winter season.

So far models I am seeing through March 2012 are predicting anywhere from a weak La Nina to a weak El Nino. This kind of pattern can be good for snow and cold weather for our area.

We just came off a very strong La Nina this past winter but due to cooperation from the NAO and some other factors we managed to do reasonably well for snowfall across a large portion of Tennessee.

Looking back at previous patterns doesn't always help, as was the case last year, but they will often follow similar trends.

The last time we came off a very strong La Nina and went into weak El Nino territory was in the mid to late 1970s. Those winters turned out to be some of the most legendary winters we've seen in the Eastern US for snow, but especially for extended and frigid cold weather.

Weak La Nina's have also produced some great winters. 1995-96 was a weak Nina year. It's one of the most legendary winters for my area for both snow and cold. It featured around 35 inches of snow and temps as low as -20.

Just going on gut alone, it's been so snowy in my area the past two years I can't believe we'd get a 3rd winter in a row with so much above normal snowfall.

 But true bone chilling arctic cold has been in short supply for a long time now. We've not saw a -10 reading here in a long time and have rarely saw anything below 0. We used to see temps approach or exceed that every couple of winters. The -15 to -20+ stuff is more rare but was still a once every 10 years kind of event. I believe it's been 15 years since we went below -10 here.

I am not going to predict we make it there, but the ENSO pattern is one that's favorable at least for very cold temps to roll into the area. ENSO was neutral for the frigid December 89 arctic outbreak. Weak La Nina for the cold late 70s. Weak La Nina for the record breaking 1985 cold wave. Weak La Nina for the -20 in 1996.

Ultimately winter will be much more directly impacted here by the NAO, AO and PNA but those aren't addressable until we get into winter.

[Cyclonicjunkie]

Last winter was certainly one to remember, and if we have alot of blocking this winter it will be just as good if not better. The thing that was missing most of the time last winter was a +PNA. If we could have gotten a huge +PNA ridge out west last winter it would have been an epic winter IMO here.

I think the -NAO is certainly going to play another major role this coming winter, but the key mixing factor to that, is the elusive +PNA. It looks like a La Nada winter right now, but as John said it could easily slip into weak Nina or Nino territory by winter's start. It certainly will be fun watching things start to unfold around autumn. 

Let me say that, after last winter, ENSO just dont mean as much to me as it used to. 

[John1122]

What I was looking at this morning pretty much had all the models showing a spread of .5-1c on either side, with slightly more being slightly below normal through March 2012 on the ENSO. Which is why I am leaning towards a weak LaNina/Netural phase through winter.

It's a long way off, but it's also the first time in quite a while I can remember CPC not having us in the above normal temps for DJF on their extended outlooks from this time of year.

After a fairly long run of mostly positive stuff the NAO has fallen back into a mostly negative pattern like it was doing last year. It's spent almost all of the last 2.5 months in the negative with the exception of about the first week of June. It's predicted to spend the next 14 days negative too.

I believe that was what got us into such a snowy pattern last winter, the NAO pretty much stayed negative or neutral with only short trips into positive territory last fall and on through winter up until late February.

The PNA has actually spent a fair amount of time in positive territory since mid March compared to winter when it seems like it stayed negative for about 3 straight months from Dec - Feb.

[StormNine]

 The ENSO, NAO, AO, PNA, MJO, PDO etc.. and such are like puzzle pieces for how the winter went.  Sometimes one or more of these factors is a bigger piece than normal.  The last two winters the -NAO, -AO were the biggest pieces and the ENSO, PNA were smaller pieces.  In 1997-98 the ENSO was the big piece and others the smaller pieces.

In some winters the pieces are close to equal.  You are not always going to have a record low -NAO or -AO every winter.  Just like you are not always going to have a raging La Nina or El Nino every winter. Not every winter will feature either a huge trough or a huge ridge over the Western US.  It is how all the pieces form that gives you the big picture.

[John1122]

The ENSO, NAO, AO, PNA, MJO, PDO etc.. and such are like puzzle pieces for how the winter went.  Sometimes one or more of these factors is a bigger piece than normal.  The last two winters the -NAO, -AO were the biggest pieces and the ENSO, PNA were smaller pieces.  In 1997-98 the ENSO was the big piece and others the smaller pieces.

In some winters the pieces are close to equal.  You are not always going to have a record low -NAO or -AO every winter.  Just like you are not always going to have a raging La Nina or El Nino every winter. Not every winter will feature either a huge trough or a huge ridge over the Western US.  It is how all the pieces form that gives you the big picture.

The NAO probably has the most effect on us out of all of them though. It's pretty much a question of how much staying power it will have once it goes negative. If the pattern is more progressive the shots of cold will be brief. But last year wasn't the first time an extended -NAO overcame the ENSO to produce a harsher winter than would normally be expected under that ENSO pattern.

The PNA, if it cooperates, is the way to really drive true Arctic air from Siberia and Alaska into the picture.  It also helps suppress the storm track south so we can get the storms moving into Southern Cal and trekking east across Texas if we are lucky.

Last year we averted a truly brutal winter on par with the late teens, late 70s etc due to the PNA being stubbornly negative which didn't really allow for any exceptional cold to go along with the snow across the area.

[StormNine]

While I agree that NAO impacts weather in our area more than ENSO does.  It is also important as mentioned in this thread that not all the time will there be a sharply -NAO and -AO scheme like there was the last two winters.  At times where the NAO may be slightly negative, neutral, or slightly positive will be where we really need the +PNA ridge to step in.  This winter ENSO shouldn't be much of an issue as we look to be neutral or weak on either side, so that won't be a huge piece to begin with this winter. 

  There is talk that in the last few winters we moved from a cycle of +NAO winters to a cycle of -NAO winters.  So that could favor us for a -NAO winter, but we will have to wait and see if that follows through and how low it goes if it does follow through.  Like mentioned by many that a Western US Ridge is another big piece of the puzzle.

[Curt]

While I agree that NAO impacts weather in our area more than ENSO does.  It is also important as mentioned in this thread that not all the time will there be a sharply -NAO and -AO scheme like there was the last two winters.  At times where the NAO may be slightly negative, neutral, or slightly positive will be where we really need the +PNA ridge to step in.  This winter ENSO shouldn't be much of an issue as we look to be neutral or weak on either side, so that won't be a huge piece to begin with this winter. 

  There is talk that in the last few winters we moved from a cycle of +NAO winters to a cycle of -NAO winters.  So that could favor us for a -NAO winter, but we will have to wait and see if that follows through and how low it goes if it does follow through.  Like mentioned by many that a Western US Ridge is another big piece of the puzzle.

Well worth noting, too that during the sharply negative NAO last December and early January, this part of the state was cold, but unlike places further east, dry as well. West and Mid TN seem to do better with a mildy neg NAO during its transition and/or flucuations. The neg PNA was not a help last year either.

And while all of the winter signals are a puzzle, Mempho and I have taken a look at historical stats which usually show that in this part of the state(and middle most likely as well), a weak La Nina plus mildly neg NAO = good combo for winter precip. It doesnt guarantee it, but odds are better.

[StormNine]

Good point Curt.  Strong -NAO signals favor more Plateau and eastward.  Most of your storms west of the Plateau are ULL driven, overrunning, sometimes but it is rare they can be Miller A storms.  The Miller A/Nor'easter pattern that was favored the last two winters typically helps out areas from a line to Cookeville to Winchester TN eastward.  I really learned last winter that it is impossible to predict snow fall amounts in the heaviest bands.  If you go under one of those bands in a strong ULL situation you can really overachieve.  We also found that out locally during the March 2008 and 2009 events.

[Kat Aurelia]

Can we please have some scientific analysis that led you to this conclusion? Either provide some sound reasoning (and not a one-line statement with wild declarations) or your comment will be removed.

Eh, I'll remove it, Kevin.  I was half asleep when I posted that.  LOL.  Sorry.  I'll post a more reasoned answer later on lol

[Memphis Weather]

Eh, I'll remove it, Kevin.  I was half asleep when I posted that.  LOL.  Sorry.  I'll post a more reasoned answer later on lol

Thanks. Sorry to be a bit harsh...but we just have to advise anybody making any type of forecast-like post or claim to have reasoning/explanation for such. Otherwise...your motivations could be in question to the staff and it also creates additional questions among the forum community (like we saw here). Posts that don't follow those guidelines are subject to removal. Again...we only ask this for those making posts that can be perceived as a "forecast"...short-term or long-term.

[John1122]

Good point Curt.  Strong -NAO signals favor more Plateau and eastward.  Most of your storms west of the Plateau are ULL driven, overrunning, sometimes but it is rare they can be Miller A storms.  The Miller A/Nor'easter pattern that was favored the last two winters typically helps out areas from a line to Cookeville to Winchester TN eastward.  I really learned last winter that it is impossible to predict snow fall amounts in the heaviest bands.  If you go under one of those bands in a strong ULL situation you can really overachieve.  We also found that out locally during the March 2008 and 2009 events.

It's tough to get the right situation for the entire state, but some of the best coverage of snow and frigid cold for the whole state have been with the -NAO/-AO/weak La Nina set up.

I believe the whole state was snow covered during the late 1970s, the 1985 outbreak and the 1996 outbreak.

[Cyclonicjunkie]

It's my belief that large scale indexes such as the NAO will not favor one side of the state more than another. I believe when you get down to that kind of specific detail, one has to look more at the orientation of the trough that accompanies a negative NAO. Also, stormtrack, stormtype (Miller a and b etc), and what synoptic pattern allowed this certain storm to give one side of TN more snow than the other.

Of course a -NAO will be more favorable for snow during winter, for the whole state, but which side is dependant on more smaller scale details and not indexes such as the NAO etc..I really dont believe the NAO impacts smaller scale details, such as stormtrack and type to the point where one can say it favors east TN over west TN.

Of course how negative or postive it is, will favor certain patterns, but when these patterns are layed out I truly believe they're smaller players on the field. These small details determines which side of the state gets more cold and snow IMO.

Also I am seeing some interesting analogs coming up, including 66-67 and 95-96, which both had very intense winter cyclones that produced significant to major snowfall in the eastern US.









Now im not very big on analogs, as no two winters will ever be the same, but they are fun to talk about and pass the time until winter arrives. Anyways IMO it looks like another winter that will be dominated by the negative NAO/AO regime, and ENSO status won't make a big difference one way or another, but of course all this is still very preliminary.

[Nashville_Wx]

Already itching for winter eh.... Me too 

[John1122]

It's my belief that large scale indexes such as the NAO will not favor one side of the state more than another. I believe when you get down to that kind of specific detail, one has to look more at the orientation of the trough that accompanies a negative NAO. Also, stormtrack, stormtype (Miller a and b etc), and what synoptic pattern allowed this certain storm to give one side of TN more snow than the other.

Of course a -NAO will be more favorable for snow during winter, for the whole state, but which side is dependant on more smaller scale details and not indexes such as the NAO etc..I really dont believe the NAO impacts smaller scale details, such as stormtrack and type to the point where one can say it favors east TN over west TN.

Of course how negative or postive it is, will favor certain patterns, but when these patterns are layed out I truly believe they're smaller players on the field. These small details determines which side of the state gets more cold and snow IMO.

Also I am seeing some interesting analogs coming up, including 66-67 and 95-96, which both had very intense winter cyclones that produced significant to major snowfall in the eastern US.

Now im not very big on analogs, as no two winters will ever be the same, but they are fun to talk about and pass the time until winter arrives. Anyways IMO it looks like another winter that will be dominated by the negative NAO/AO regime, and ENSO status won't make a big difference one way or another, but of course all this is still very preliminary.

I am seeing a bit of an analog from the 1975-76 winter to the 1976-77 winter as far as the ENSO goes. '75-76 was a strong La Nina. By '76-'77 the ENSO had recovered to neutral/weak El Nino. The fall/winter of '76-'77 was pretty brutal in the East. It was so cold the Lakes froze by Mid-December. The NAO went very negative in October and stayed mostly that way until January 1977. It also had the benefit of a +PNA locking into place. Temps that winter were 8 degrees below normal across the Ohio Valley and it snowed in Miami, Florida and there was rain/snow mixed in the Bahamas.

A slightly lesser ENSO analog is 1956-57 into 1957-58. That was a strong La Nina into a moderate El Nino. I don't think we will see quite that much warming taking place this year. It wasn't as dramatic as the late 70s as stronger El Ninos don't work out quite as well here. Still Nashville recorded it's first double digit snow accumulation in 6 years that winter.  The late 70s winters, starting in 76-77 kicked off a the only period in Nashville history with 3 20+ inch snowfall seasons in a row.

As for trends, this is, by I believe 4 years, the longest stretch in Nashville history without recording an 18+ inch snowfall season.



 

[Cyclonicjunkie]

My first PRELIMINARY fall/winter outlook, this is all based on the -PDO -NAO -AO -QBO mixed with a weak Nina ENSO condition and a couple of analogs that I prefer with some climo.

I come up with a active to very active subtropical jet with a persistent trough over the eastern US, but I have come to a conlusion that the PNA will stay more negative again this winter due to the -PDO and -QBO combination.

I feel like the Apps runner will be the most dominant storm track this winter (Great for west TN folk) with a few more than normal Miller b's also I would think. Anyways these are very preliminary and should be taken very lightly this far out as alot can change between now and fall.

I just couldnt resist an early outlook during this boring wx pattern. My long range winter outlook last year was pretty decent but I messed up on the Mid atlantic area. Going to be fun talking about winter in the next few months and I look forward to discussing it with all of you.



Temp outlook
Dark blue=Much below normal
Light Blue=Below normal
Grey=Normal
Red=Above to much above normal








Precip outlook

Dark green=Much above normal
Light Green=Above normal
Grey=Normal
Red=Below to much below normal


Snowfall potential
Purple=Much above normal
Dark blue= Above normal
Light blue=Normal
Grey=Normal to above normal





Main storm tracks late fall thru winter



ALL MAP OUTLOOKS HAVE A MARGIN OF ERROR OF + or - 50 to 150 MILES.
If you have any questions as to my reasoning for any of the outlook maps, just ask and I will be glad to discuss the reasoning behind the outlooks.

Thanks
Toot