And we begin.....

[midatlanticweather]

I think it is way behind 2014 personally. You are talking 100s of square miles of difference. It can make up ground quick. But it will be interesting to see how much difference there is after last year's record growth rate.

[Mallow]

I think it is way behind 2014 personally. You are talking 100s of square miles of difference. It can make up ground quick. But it will be interesting to see how much difference there is after last year's record growth rate.

 

I know it was brought up a lot last year... but although it might not make a huge difference, starting October on the low side in Eurasia south of 60°N would make it easier to see a high "advance" during the month--that is, you wouldn't have to end the month quite as high if you start the month lower.

[The_Global_Warmer]

Do you guys think this process will be as strong as normal with an East based super Nino?

[Mallow]

Do you guys think this process will be as strong as normal with an East based super Nino?

 

I don't know.

 

But what makes you think it'll be east-based this year?

[AvantHiatus]

Ice expansion may hit a brick wall for a long time around 76N due to the elevated SSTA.

 

[oldlogin]

Time sensitive------Looks like ski season may start early in Italy

 

http://www.persicetometeo.com/public/popup/alpe_siusi_panorama.htm

[mitchnick]

I know it's meaningless in the big picture and will probably be gone in a day or 2, but that's some pretty far south snow cover over in Asia for this time of year (9/23)

[Bob Chill]

Quick comparison to the end of Sept last year. Lagging obviously but really doesn't mean anything. Doesn't look like there will be any substantial gains in Eurasia over the next 3 days so we will likely start Oct a fair bit lower than 2014. We'll see how things go next month when the data crunchers come out of the woodwork and track gains by the square foot. 

 

 

 

[Met1985]

Quick comparison to the end of Sept last year. Lagging obviously but really doesn't mean anything. Doesn't look like there will be any substantial gains in Eurasia over the next 3 days so we will likely start Oct a fair bit lower than 2014. We'll see how things go next month when the data crunchers come out of the woodwork and track gains by the square foot.

9.30.14.JPG

9.27.15.JPG

Bob that may be a good thing correlating to the AO if we do not start so high.

[Bob Chill]

Bob that may be a good thing correlating to the AO if we do not start so high.

 

Could be. The jury is out more than ever at the correlation and exactly what is important and what isn't. If it wasn't for the epo overwhelming last winter the season would have been an epic bust that couldn't have gone more wrong by all metrics. 

 

Of course I'd prefer this year to perform in a fashion that makes a strong case but if it doesn't I'm not going to lose sleep over it. 

[Met1985]

Could be. The jury is out more than ever at the correlation and exactly what is important and what isn't. If it wasn't for the epo overwhelming last winter the season would have been an epic bust that couldn't have gone more wrong by all metrics.

Of course I'd prefer this year to perform in a fashion that makes a strong case but if it doesn't I'm not going to lose sleep over it.

Thanks Bob.

[Bob Chill]

Thanks Bob.

 

No prob. Not sure if you have read the SAI paper. It's pretty short and to the point:

 

http://web.mit.edu/jlcohen/www/papers/CohenandJones_GRL11.pdf

 

Here's a read tailored more for non-scientists and has some nice detail about the 13-14 winter:

 

http://web.mit.edu/jlcohen/www/Cohen_NOAA_fcst.pdf

 

Initially, the SCE was used as a tool prior to the SAI. The SAI shows promise as being more accurate than the SCE with a fairly high correlation using weeks 40-44 as a baseline.

 

I broke down SCE #'s a few years ago so these screen snips don't include the most recent years. You can see the SCE seems like an OK predictor but with some obvious busts (2006 in particular). But overall seems pretty sound. Like with any long range tool, there is no smoking gun and things will go wrong from time to time. The one thing that I didn't like was Dr. Cohen's interview at the end of last winter. He took credit for a correct temp forecast (which it was) but it was right for the absolute wrong reasons based on what the literature states. The literature is quite specific to the winter state of the AO and how that affects winter temps in the northern hemisphere. I also read Dr. Cohens periodic updates all of last winter. It was a constant long lead chase of the fabled "SSW" and how it was going to happen and turn the AO negative. It simply didn't work out last year. And IMO, it's more important to identify exactly why and admitting as much instead of taking credit for a temp forecast. But that's just me. 

 

Here's the SCE spreads I put together a couple years ago. The bottom one includes top 10 & bottom 10. SAI definitely seems a little better. 2006 was a big outlier in the top 10 group but the SAI didn't indicate a robust -AO signal. 

 

 

 

 

 

 

[Met1985]

No prob. Not sure if you have read the SAI paper. It's pretty short and to the point:

http://web.mit.edu/jlcohen/www/papers/CohenandJones_GRL11.pdf

Here's a read tailored more for non-scientists and has some nice detail about the 13-14 winter:

http://web.mit.edu/jlcohen/www/Cohen_NOAA_fcst.pdf

Initially, the SCE was used as a tool prior to the SAI. The SAI shows promise as being more accurate than the SCE with a fairly high correlation using weeks 40-44 as a baseline.

I broke down SCE #'s a few years ago so these screen snips don't include the most recent years. You can see the SCE seems like an OK predictor but with some obvious busts (2006 in particular). But overall seems pretty sound. Like with any long range tool, there is no smoking gun and things will go wrong from time to time. The one thing that I didn't like was Dr. Cohen's interview at the end of last winter. He took credit for a correct temp forecast (which it was) but it was right for the absolute wrong reasons based on what the literature states. The literature is quite specific to the winter state of the AO and how that affects winter temps in the northern hemisphere. I also read Dr. Cohens periodic updates all of last winter. It was a constant long lead chase of the fabled "SSW" and how it was going to happen and turn the AO negative. It simply didn't work out last year. And IMO, it's more important to identify exactly why and admitting as much instead of taking credit for a temp forecast. But that's just me.

Here's the SCE spreads I put together a couple years ago. The bottom one includes top 10 & bottom 10. SAI definitely seems a little better. 2006 was a big outlier in the top 10 group but the SAI didn't indicate a robust -AO signal.

top10eurasian2.JPG

top10eurasian.JPG

top10bottom10eurasian.JPG

Good read and tables Bob. Yeah the past few years have not gone the way that they were suppose to in accordance to the AO and winter. A bump in the road? Possibly but this winter I think will be telling. Will it be right or another bump. It will be interesting watching this October snow growth because we are starting at such a lower level than last year. Also I remember reading Dr. Cohens blogs about the SSW that never really happened. He took credit for all the wrong reasons for sure.

[Bob Chill]

Good read and tables Bob. Yeah the past few years have not gone the way that they were suppose to in accordance to the AO and winter. A bump in the road? Possibly but this winter I think will be telling. Will it be right or another bump. It will be interesting watching this October snow growth because we are starting at such a lower level than last year. Also I remember reading Dr. Cohens blogs about the SSW that never really happened. He took credit for all the wrong reasons for sure.

 

Looking back at last year we were all a bit blinded (I know I was at least) by the SAI instead of concentrating on what was actually happening during Dec. Even through the monthly # only came @ .413 the behavior (especially at the end of the month into Jan) was a pretty big warning shot. It was pretty clear that a +AO was favored overall. The SAI is the best early look we have but what happens in Dec can be really telling regardless of the early indicators. 

 

A couple years ago I did a breakdown of the Dec AO readings and what it implies through Jan-Feb. When Dec is anomalous either way, the following J-F follow in its tracks way more often than not. At the very least there appears to be a 45-60 day cycle built into an anomalous Dec AO.

 

Last year wouldn't have made the list because December was only .413. However, the period of Dec 13th through Jan 13th came in at +1.215. That was a big red flag. By mid Jan I had the sinking feeling. Luckily other factors overwhelmed and the east still had a decent winter up and down with the NE obviously getting destroyed. 

 

Here's a couple charts of how the ensuing J-F look when Dec features an anomalous AO:

 

 

 

The one thing I won't do this year is ignore what happens in Dec if the SAI is pointing strongly one way or the other. 

[Met1985]

Looking back at last year we were all a bit blinded (I know I was at least) by the SAI instead of concentrating on what was actually happening during Dec. Even through the monthly # only came @ .413 the behavior (especially at the end of the month into Jan) was a pretty big warning shot. It was pretty clear that a +AO was favored overall. The SAI is the best early look we have but what happens in Dec can be really telling regardless of the early indicators.

A couple years ago I did a breakdown of the Dec AO readings and what it implies through Jan-Feb. When Dec is anomalous either way, the following J-F follow in its tracks way more often than not. At the very least there appears to be a 45-60 day cycle built into an anomalous Dec AO.

Last year wouldn't have made the list because December was only .413. However, the period of Dec 13th through Jan 13th came in at +1.215. That was a big red flag. By mid Jan I had the sinking feeling. Luckily other factors overwhelmed and the east still had a decent winter up and down with the NE obviously getting destroyed.

Here's a couple charts of how the ensuing J-F look when Dec features an anomalous AO:

AO -1.00 or lower.JPG

+ao Dec.JPG

The one thing I won't do this year is ignore what happens in Dec if the SAI is pointing strongly one way or the other.

Some great data and something new to think about heading into December. Some great charts in reference to your studies also. Just another piece of the puzzle essentialy. Well time is ticking down to when we really see how the Sai goes. Shall be fun as always.

[scottmartin49]

???? IIRC, Cohen called the SSW perfectly last January, and the cold dropped east on cue, but it was caused by the split in the vortex, rather than a drop in the overall AO index. Am I wrong about this? I recall posting on the SSW around the time he posted it, and when it did arrive was disregarded as weak, but it (the 'weak' SSW) did just what he'd called for, even though it wasn't linked to an overall AO index change....

 

Edit: Found the old thread; http://www.americanwx.com/bb/index.php/topic/45183-ssw-on-the-3rd/

 

Hindsight is more fun than prediction(!)- sometimes.

[Bob Chill]

Dr. Cohen called for a SSW constantly once he realized that things were going awry in Dec. The splits were brief and the warming events were weak. The strat vortex was strong and intact almost door to door last winter. IMO- most if not all of the cold in the MW and E was EPO driven. Yes, the brief splits did help displace cold from the high latitudes but nobody can convince me that Dr. Cohen and the science behind the SAI performed well last year. 

[weathafella]

At the end of the preseason....

1 year ago....

[Absolute Humidity]

Less is better in early October

[nynjpaweather]

Let the games being, next 3 weeks help forecast the AO.  Not 100% air tight, but if you are forecasting a cold winter in the Eastern US, the snow growth and depth better be above normal or you'll have egg on your face.

[Absolute Humidity]

The Last week is just as important, the 700K loss last week of Oct last year was a red flag.

[The_Global_Warmer]

The Last week is just as important, the 700K loss last week of Oct last year was a red flag.

That seems logically unlikely.

That is such a small area of snow cover. In an already waning solar output.

I guess the physical mechanism would already be underway by then.

But I don't know

[Bob Chill]

Quick coverage continues in Eurasia

 

 

 

 

Positive anomalies showing in central Russia

 

 

 

Looks to be an active period coming up around 60N and coverage should spread south of there along with a good portion of eastern Siberia. 

 

 

 

[Superstorm93]

GFS over the next 10 days....

 

Impressive growth to say the least. Though with its current 500mb NH scores, I remain a bit weary. 

 

 

 

 

[Absolute Humidity]

That seems logically unlikely.

That is such a small area of snow cover. In an already waning solar output.

I guess the physical mechanism would already be underway by then.

But I don't know

Maybe not enough to reduce SAI regressive curve, but by then we saw the lower heights over the Kara Barrets seas, possible influenced by typhoon Nuri. The -AO never recovered.

[DTWXRISK]

LINK FOR THOSE IMAGES ? 

 

GFS over the next 10 days....

 

Impressive growth to say the least. Though with its current 500mb NH scores, I remain a bit weary. 

 

 

 

 

[DTWXRISK]

    WOW   folks still  jumping on that  old song ?   the drop off at the end of  OCT  was   meaningless

The Last week is just as important, the 700K loss last week of Oct last year was a red flag.

[Superstorm93]

LINK FOR THOSE IMAGES ?

GREarth

Sent from my SM-G925V using Tapatalk

[Cold Rain]

WOW folks still jumping on that old song ? the drop off at the end of OCT was meaningless

Last year, that Millwx guy did a lot of analysis, even down to the number of days at the end of the month and the specific week, showing where snow advance/melting was the most meaningful. Then he quit posting.

[Absolute Humidity]

WOW   folks still  jumping on that  old song ?   the drop off at the end of  OCT  was   meaningless

Last year, that Millwx guy did a lot of analysis, even down to the number of days at the end of the month and the specific week, showing where snow advance/melting was the most meaningful. Then he quit posting.

Yes millwx argued that week 43 and 44 were critical times in terms of snow loss, with week 43 having slightly more weight.