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And we begin

weathafella

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Tom

Tom

Posted
Posted

spend most of my time reading and learning, great topic...my question past few days saw some posts about the loss of snow over the last days of October may not have an impact on overall winter pattern since the "damage" (good snow cover) has been done so to speak....If that is the case should we remember if in the years to come the last 2-4 days of month have huge gains should be discounted since the bulk of month is already over, or is this a one sided?  Should their be consideration as a "hard" date such as Oct 25th and not count additions or losses for rest of month?  

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griteater

griteater

Posted
Posted

spend most of my time reading and learning, great topic...my question past few days saw some posts about the loss of snow over the last days of October may not have an impact on overall winter pattern since the "damage" (good snow cover) has been done so to speak....If that is the case should we remember if in the years to come the last 2-4 days of month have huge gains should be discounted since the bulk of month is already over, or is this a one sided?  Should their be consideration as a "hard" date such as Oct 25th and not count additions or losses for rest of month?  

 

For snow advance south of 60N in Eurasia (Cohen's Snow Advance Index 'SAI'), what matters is the linear regression (best fit line) of all daily data points for the full month of October (cfbaggett's graph above) - the greater the slope line, the greater the SAI value for the month.  This Oct we have the second highest SAI on record (Oct 1976 is the only one higher).  

 

In terms of pure snow cover extent across all of Eurasia for October, and associated timing, see millwx's post (and others) here - http://www.americanwx.com/bb/index.php/topic/44473-and-we-begin/?p=3099244

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Cold Rain

Cold Rain

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Posted

For snow advance south of 60N in Eurasia (Cohen's Snow Advance Index 'SAI'), what matters is the linear regression (best fit line) of all daily data points for the full month of October (cfbaggett's graph above) - the greater the slope line, the greater the SAI value for the month. This Oct we have the second highest SAI on record (Oct 1976 is the only one higher).

In terms of pure snow cover extent across all of Eurasia for October, and associated timing, see millwx's post (and others) here - http://www.americanwx.com/bb/index.php/topic/44473-and-we-begin/?p=3099244

Grit, in terms of pure snow cover, what's the final ranking in historical context? Looking at Badgett's graph, it looks like the final is close to 2009, but that's just south of 60N, right? The eyeball test indicates total coverage is greater, if I'm looking at the right maps!

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DTWXRISK

DTWXRISK

Posted
Posted

wow  that  wrong   I mean really  wrong ... its  not a  catastrophe   and 2nd  as  already stated   its the  slope of the line that is important   --   linear regression (best fit line) of all daily data points for the full month of October

 

 

Actually I was eyeballing 60 and south. Regardless, SAI will likely take some hit with -3msk. How much of a hit? Comparing the 27th and today does look pretty catastrophic in terms of snow loss. We'll know soon enough.

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griteater

griteater

Posted
Posted

Grit, in terms of pure snow cover, what's the final ranking in historical context? Looking at Badgett's graph, it looks like the final is close to 2009, but that's just south of 60N, right? The eyeball test indicates total coverage is greater, if I'm looking at the right maps!

 

CR - I don't have the hard data on end of month full Eurasia snow cover and how this Oct compares.  Maybe GaWx or someone else has that data.  My guess is that we are in the 65-85 percentile.  In the SAI paper, Cohen notes that 2009 wasn't a super high snow cover extent (SCE) year, but it WAS high for snow advance (SAI) - "However during October 2009 it was not the mean SCE that was exceptional but rather the rapidity of the snow cover advance that was exceptional [Cohen et al., 2010]."

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Cold Rain

Cold Rain

Posted
Posted

CR - I don't have the hard data on end of month full Eurasia snow cover and how this Oct compares. Maybe GaWx or someone else has that data. My guess is that we are in the 65-85 percentile. In the SAI paper, Cohen notes that 2009 wasn't a super high snow cover extent (SCE) year, but it WAS high for snow advance (SAI) - "However during October 2009 it was not the mean SCE that was exceptional but rather the rapidity of the snow cover advance that was exceptional [Cohen et al., 2010]."

Gotcha, thanks man. Just wondering about the overall SCE and where it ranks historically in the context of Millwx's ideas.

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Tom

Tom

Posted
Posted

For snow advance south of 60N in Eurasia (Cohen's Snow Advance Index 'SAI'), what matters is the linear regression (best fit line) of all daily data points for the full month of October (cfbaggett's graph above) - the greater the slope line, the greater the SAI value for the month.  This Oct we have the second highest SAI on record (Oct 1976 is the only one higher).  

 

In terms of pure snow cover extent across all of Eurasia for October, and associated timing, see millwx's post (and others) here - http://www.americanwx.com/bb/index.php/topic/44473-and-we-begin/?p=3099244

 

Thank you

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griteater

griteater

Posted
Posted

Gotcha, thanks man. Just wondering about the overall SCE and where it ranks historically in the context of Millwx's ideas.

 

Around Oct 26, we were 2nd highest on record for snow cover extent, which is in millwx's noted timeframe...then we had the dropoff to end the month - http://www.americanwx.com/bb/index.php/topic/44473-and-we-begin/?p=3098909

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Absolute Humidity

Absolute Humidity

Posted
Posted

wow  that  wrong   I mean really  wrong ... its  not a  catastrophe   and 2nd  as  already stated   its the  slope of the line that is important   --   linear regression (best fit line) of all daily data points for the full month of October[/size]

Yes wayyyy off, bear goggles were effecting snow goggles. I suppose I was looking at last year...erg

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Shawn

Shawn

Posted
Posted

It's weird that the snow cover at Central SC isn't showing up on this map.

 

Most if not all of it is melted.  Within minutes of the snow ending, it just went bye-bye.  We've been really warm, and the surface air was much above freezing.  It accumulated so impressively due to the heavy, sloppy rates.

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GaWx

GaWx

Posted
Posted

And so October ends...

Amazing month. The slope, as I calculate it, was 295,000 km^2/day. Thus, it appears we can predict with reasonable confidence a strongly negative AO winter.

Let's watch how the pattern evolves over the next few weeks. Heck, maybe instead folks in the Southeast should simply look out the window. Heavy snow in the low-country of South Carolina this morning!?!?!?!?!

In case anyone were to suspect cfbaggett had a -AO bias as regards predicting DJF AO via the SAI, think again. All you really have to do to eliminate those suspicions is to just look at last year's autumn Eurasian snow thread. You'd see there that he is consistently pretty pessimistic on the chances for a -AO in DJF 2013-14 pretty much throughout most of October, largely due to the fast start near Oct. 1st of last year as well as the sluggish increases thereafter. Consistent with this, he said that last year's SAI was in favor of a moderately +AO for last winter as per this post/graph of slopes:

http://www.americanwx.com/bb/index.php/topic/41113-and-we-begin/?p=2458000

Another thing one can see is that he brought over the identical regression based lines that he had in last year's graph for past years and put them in this year's graph. So, I very much trust cfbaggett is being objective in all of his SAI related analyses and am also thinking strong -AO is likely for DJF 2014-5 (also helped by OPI and that we're supposedly going to be in a weakish El Niño).

Edit: In that same thread in case anyone cares, I, myself, was acknowledging several times that the fast start last October really hurt. So, I also hope others don't take me for being -AO biased.

Also, check last year's thread for a great post from HM explaining how it made sense that the early high

snowcover of last October was not a good thing.

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weathafella

weathafella

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Posted

Ok friends. I'm your thread starter. I've been doing this since my 50s and I'm rapidly closing in on 70 (25 months...yikes!).

And we begin is the thread title.

I start by mid September.

No pretenders. The one year we had one was among the weakest winters of the past 100 years...lol.

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Ginx snewx

Ginx snewx

Posted
Posted

And so October ends...

Amazing month. The slope, as I calculate it, was 295,000 km^2/day. Thus, it appears we can predict with reasonable confidence a strongly negative AO winter.

Let's watch how the pattern evolves over the next few weeks. Heck, maybe instead folks in the Southeast should simply look out the window. Heavy snow in the low-country of South Carolina this morning!?!?!?!?!

IMG_20141102_144541.jpg
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cfbaggett

cfbaggett

Posted
Posted

In case anyone were to suspect cfbaggett had a -AO bias as regards predicting DJF AO via the SAI, think again. All you really have to do to eliminate those suspicions is to just look at last year's autumn Eurasian snow thread. You'd see there that he is consistently pretty pessimistic on the chances for a -AO in DJF 2013-14 pretty much throughout most of October, largely due to the fast start near Oct. 1st of last year as well as the sluggish increases thereafter. Consistent with this, he said that last year's SAI was in favor of a moderately +AO for last winter as per this post/graph of slopes:

http://www.americanwx.com/bb/index.php/topic/41113-and-we-begin/?p=2458000

Another thing one can see is that he brought over the identical regression based lines that he had in last year's graph for past years and put them in this year's graph. So, I very much trust cfbaggett is being objective in all of his SAI related analyses and am also thinking strong -AO is likely for DJF 2014-5 (also helped by OPI and that we're supposedly going to be in a weakish El Niño).

Edit: In that same thread in case anyone cares, I, myself, was acknowledging several times that the fast start last October really hurt. So, I also hope others don't take me for being -AO biased.

Also, check last year's thread for a great post from HM explaining how it made sense that the early high

snowcover of last October was not a good thing.

I do try my best to be objective with regard to the data. However, I freely admit my bias toward wanting a cold and snowy winter!   :santa:

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Absolute Humidity

Absolute Humidity

Posted
Posted

Apologies if it's been posted already, but what were the final SCE, SAI, and OPI values for last month?

 

Also does anyone know a better (and more updated) source for historical SCE and SAI than the graph in this paper? http://web.mit.edu/jlcohen/www/papers/CohenandJones_GRL11.pdf

You can get SCE from here, updated through Sept. But the oct weeklies are there upto week 43.

http://climate.rutgers.edu/snowcover/chart_vis.php?ui_year=2014&ui_month=9&ui_set=1

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das

das

Posted
Posted

Das, what web site is that from?

 

Another web site that I found recently, the Canadian Cryospheric Information Network page: https://www.ccin.ca/home/

 

Sorry for the delay, was busy this weekend.  The VIIRS snow temp data is from Peter Romonov's great automated snow mapping system at NESDIS Satellite Applications and Research (http://www.star.nesdis.noaa.gov/smcd/emb/snow/HTML/snow.htm).  Click the VIIRS global snow map link at the bottom right or go here for the direct link ftp site for the full rez images:

 

ftp://www.star.nesdis.noaa.gov/pub/smcd/emb/snow/viirs/snow-fraction/images/north-east/

 

There's some info on the mapping process, imagers used and resolution captured earlier in this thread.  Ping me if you have any detailed questions.

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michsnowfreak

michsnowfreak

Posted
Posted

Ok friends. I'm your thread starter. I've been doing this since my 50s and I'm rapidly closing in on 70 (25 months...yikes!).

And we begin is the thread title.

I start by mid September.

No pretenders. The one year we had one was among the weakest winters of the past 100 years...lol.

I literally cannot believe that not only is another winter is starting, but that signs are strong (no guarantees of course) for yet ANOTHER severe winter. Last years record winter will not be matched (locally), but if it is indeed another hard winter I will say it. The trio of late '70s winters have been replaced!
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das

das

Posted
Posted

Gotcha, thanks man. Just wondering about the overall SCE and where it ranks historically in the context of Millwx's ideas.

 

Around Oct 26, we were 2nd highest on record for snow cover extent, which is in millwx's noted timeframe...then we had the dropoff to end the month - http://www.americanwx.com/bb/index.php/topic/44473-and-we-begin/?p=3098909

 

Here it is in graphical form.  This is total SCE for the entire Eurasian domain in 1km resolution in Plate-Carre latitude-longitude grid mapping (not polar-stereographic like IMS).  

 

multisensor_4km_ea_snow_extent_by_year_g

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GaWx

GaWx

Posted
Posted

I looked at the SAI paper written by Cohen and looked at figure 2 in it:

 

http://onlinelibrary.wiley.com/doi/10.1029/2011GL049626/full

 

1) For 1997-8 through 2013-4 (except I don't have 2011-2): SAI's calculated based on daily SCE

 

 All were good to excellent imo except for 2001-2 (SAI predicted a - AO and it verifed as a +AO) and 2010-1 (SAI predicted a +AO and it verified to be a -AO). So, it did well for 14 of the 16 or 88% of them, which is excellent!

 

 

2) 1973-4 through 1996-7: SAI's calculated based on weekly SCE (definitely not nearly as accurate..so it is good that the daily data is now available)

 

It did great with 11: 74-5, 75-6, 76-7, 82-3, 84-5. 87-8, 88-9. 90-1, 92-3, 93-4, 95-6

It did pretty well with 4: 80-1, 83-4, 85-6, and 96-7

It didn't do well with 9 :

a. SAI suggested too +AO for 5: 77-8, 78-9, 79-80, 81-2, 86-7 (mostly late 70's to early 80's)

b. SAI suggested too -AO for 4: 73-4, 89-90, 91-2, 94-5 (mostly late 80's to early 90's)

 So, it did pretty well to great for 15 of the 24 or 63% of them. Thank goodness daily snow data is now available.

 

3) 1973-4 through 2013-4 (except 2011-2): when SAI's either +1+ or -1-: did well overall, especially once daily snow data available, when it did very well 100% of the time (4 of 4):

 

It did very well for 7 of 9 (78%):

 - -AO prediction: 76-7, 09-10, 12-13

- +AO prediction: 88-9, 92-3, 98-9, 07-8,

 

It did pretty well for 1 of 9 (11%):

- +AO prediction 83-4

 

It didn't do well for 1 of 9 (11%):

- -AO prediction: 73-4

 

4) With the SAI in 2014 being the 2nd highest since the calculations started in 1973 and had that chart included 2014-5, it appears that it would be below the -3 line by my estimate and not all that far above 1976-7! Judging by how well the SAI has done with extremes, especially since the daily SCE data became available, the chances of the very high 2014 SAI correctly foretelling a sub -1 AO this DJF are quite high.

 

 

***EDITED AGAIN..should be correct now***

 

**3rd section has now been improved to better assess when SAI is over or under 1**

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