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And we begin.


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Do we want it to be this expansive so early? I thought that was the point of the research.

 

In addition to what wxmx linked, the gains are what really matter. I prefer it to start below average (south of 60N) because that makes bigger gains easier, but there are cases where the snow advance index was high even though we started the month above normal. A lot of this is because the standard deviation of snowcover over Eurasia at the end of October is much higher than at the beginning.

 

We did start the month above normal this year.

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While it may be creating the above average snow cover across northern russia and expansive ice coverage currently, I believe we would want to see that vortex position over northern russia change going through Oct. Iv you look at years with impressive SAI, they had blocking over those regions in Oct. 

 

i'd post some esrl images, but our government blows.

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Here's the Eurasian snowcover (between 30 and 60 degrees North) for the first 7 days of October. The SAI has a small sample size (1998 to present). Within that sample, I don't believe there are any years that have started as anomalously high as this year. I think we are in unprecedented territory in regard to the SAI.

 

post-7423-0-29738700-1381236982_thumb.pn

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Here's the Eurasian snowcover (between 30 and 60 degrees North) for the first 7 days of October. The SAI has a small sample size (1998 to present). Within that sample, I don't believe there are any years that have started as anomalously high as this year. I think we are in unprecedented territory in regard to the SAI.

 

where did you find that product?  thanks

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I messaged him about it too.  He responded indicating he took the raw data and made it himself.  I hope he shares an updated one in a few weeks. 

 

 

He did a few updates last year using the same data and home-made graph.

 

I agree, the graphs are nice.

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Here's an update for this year's SAI. Our areal extent anomalies are still running above normal, so we'll need a huge end to October to have a positive SAI this year. That being said, there are probably other physical mechanisms at play with such a large snow extent to begin the month. This year is eerily similar to 2002. Snowcover in 2002 also got off to a quick start. Also, in the eastern US, October was two-faced: blowtorch to begin the month and deep cold anomalies to end the month. I'd happily take a repeat of 2002-03.

 

 

post-7423-0-52323000-1381756957_thumb.pn

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Here's an update for this year's SAI. Our areal extent anomalies are still running above normal, so we'll need a huge end to October to have a positive SAI this year. That being said, there are probably other physical mechanisms at play with such a large snow extent to begin the month. This year is eerily similar to 2002. Snowcover in 2002 also got off to a quick start. Also, in the eastern US, October was two-faced: blowtorch to begin the month and deep cold anomalies to end the month. I'd happily take a repeat of 2002-03.

 

Thanks for the update! ^_^

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It seems impossible to get a better SAI than 2009 and 2012, due to the 'high start'. More importantly is the physical reasoning behind the SAI, the cooling effect. In my opinion it's only a good thing too start as soon as possible with that. Anyway, coming days more snowfall south of 65N, so we can expect an increase.

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It seems impossible to get a better SAI than 2009 and 2012, due to the 'high start'. More importantly is the physical reasoning behind the SAI, the cooling effect. In my opinion it's only a good thing too start as soon as possible with that. Anyway, coming days more snowfall south of 65N, so we can expect an increase.

 

The October SAI is better-correlated with the winter AO than just plain old average October snowcover (that was Cohen's original index on the topic, in fact).

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It seems impossible to get a better SAI than 2009 and 2012, due to the 'high start'. More importantly is the physical reasoning behind the SAI, the cooling effect. In my opinion it's only a good thing too start as soon as possible with that. Anyway, coming days more snowfall south of 65N, so we can expect an increase.

 

The reason why later October is important is because the state of the polar vortex formation. Furthermore, advancement south of 60N has a lot to do with greater amount of sunlight being reflected back from the albedo of snow cover --> stronger Siberian/Mongolian high forming --> stronger wave flux to the stratosphere

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The reason why later October is important is because the state of the polar vortex formation. Furthermore, advancement south of 60N has a lot to do with greater amount of sunlight being reflected back from the albedo of snow cover --> stronger Siberian/Mongolian high forming --> stronger wave flux to the stratosphere

 

 

Is there a way to measure the state of the polar vortex in November and how this year's SAI affected it (compared to previous years)?

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lots more ice as well.  In an earlier post, I inserted a graph of the arctic temps about 80N.  It is now averaging below zero F in that area (below average as well) and obviously spilling into the remainder of the arctic.  Will be interesting to see how the weather responds as we get further into the season.  The Oct/Nov temp couplet in the States has been a killer the last several years.

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lots more ice as well.  In an earlier post, I inserted a graph of the arctic temps about 80N.  It is now averaging below zero F in that area (below average as well) and obviously spilling into the remainder of the arctic.  Will be interesting to see how the weather responds as we get further into the season.  The Oct/Nov temp couplet in the States has been a killer the last several years.

 

I wonder if the increased ice/cold Arctic reduces the chance for a very dominant -AO this winter vs. if the ice hadn't expanded so much vs. 2012.

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SAI updated. Unless we see a very extensive growth in snowcover to end the month, the SAI is pointing toward a +AO winter.

 

 Agreed. Ironically, the 2013 SAI is currently partially being hurt by there being so much snow near the end of Sep. and during the first few days of Oct. as that has caused the sloped line to start at almost 2 million sq. km. The other three years started at under 1/2 million sq. km. Had 2013 also started around 1/2 million sq. km, the 2013 current slope would have been much higher than it is and a good bit higher than 2007. Isn't it sort of counterintuitive that just starting the month with "too much" snow, via causing the SAI indicator to be lower than it otherwise would have been, will reduce the prospects for a good (-AO) winter? Does it make sense that above average late Sep. to very early Oct. snow hurts the SAI?

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