2013-14 MA Winter Disco - 'cause it's never too early.

[usedtobe]

Wes. Can you post that four quadrant graph you had last year showing the storms for each of the ao/nao combinations?

 

 

 

Hpe you can read it OK.  All the dots below the dark horizontal line have a negative AO.  All the dots to the right of the dark vertical line have a positive NAO.  Note only 3 cases had a positive AO and negative NAO.  but there were 16 or so with a negative AO and positive NAO.  Note the graph  is for DC 4 inch or greater storms. 

 

If you want to look at the importance of the nina and AO together for 20 inch plus winters.  The graph below shows why you don't want a nina and want a negative AO.

 

[snow.]

 

 

Hpe you can read it OK.  All the dots below the dark horizontal line have a negative AO.  All the dots to the right of the dark vertical line have a positive NAO.  Note only 3 cases had a positive AO and negative NAO.  but there were 16 or so with a negative AO and positive NAO.  Note the graph  is for DC 4 inch or greater storms. 

 

If you want to look at the importance of the nina and AO together for 20 inch plus winters.  The graph below shows why you don't want a nina and want a negative AO.

 

 

 

my guess is we will have similar to last winter..with the AO being more negative than the NAO which didn't really help us as the mean block was too far east....I figure this winter is more of the same with probably a little weaker -AO, and a -NAO that puts the mean negative height anomaly to our north and east...

[snow.]

Yes, with split flow we can get this. Split flow allows gulf moisture to be sucked into a ns vort diving down. The majority of our big storms are strong vorts barreling across the desert sw and through tx/gulf before turning north. It's very hard to get something like that without an active stj.

The nw track mostly applies to the big storms this winter. They will close and wrap and cut unless a heck of a lot lines up. The whole threading/timing thing. Those that do cut far enough east will likely be ov/coastal jumpers.

IMO- the best chances at widespead events (even modest ones) will be from enough blocking to allow a strong vort to take the perfect track. Similar to what st mary county/RIC/Orange Co have seen in the last couple years. We just need to be in the bullseye because those systems aren't extensive geographically.

I'm absolutely not ruling out a timed phaser because they can happen in any enso setup. I'm not counting on one but will glady track the miracle of 13-14.

 

something like this (very crude) would give us our best chance for a 6"+ event...we'll probably get the pattern at some point, but then we need things to sync which is still an uphill battle, but easier with the split flow...without the northern stream helping, anything out of the south will most likely be our standard 1012 mb amorphous, pathetic low that ambles out to sea, or has a herculean primary gutting the OV...

 

[Bob Chill]

something like this (very crude) would give us our best chance for a 6"+ event...we'll probably get the pattern at some point, but then we need things to sync which is still an uphill battle, but easier with the split flow...without the northern stream helping, anything out of the south will most likely be our standard 1012 mb amorphous, pathetic low that ambles out to sea, or has a herculean primary gutting the OV...

 

 

 

The WD index argues strongly for the freak timed/phased vorts with a track from northern AL to Va beach. 

 

But I do totally agree with what you're saying. That's the most likely way to get some form of a miller A'ish event. Gotta nail the timing of the block and 50/50. The kind of system with a sharp cutoff and ene trajectory and not some beautiful ride the coast track. As much as I would love to see that it would require way too much of everything going right. We haven't done well with everything going right since 2010.  

 

One of the other ways is to get something on the tail of the fropa from a cutter. Nice little wave with a modest 2-4/3-5 type of outcome. 

[snow.]

The WD index argues strongly for the freak timed/phased vorts with a track from northern AL to Va beach. 

 

But I do totally agree with what you're saying. That's the most likely way to get some form of a miller A'ish event. Gotta nail the timing of the block and 50/50. The kind of system with a sharp cutoff and ene trajectory and not some beautiful ride the coast track. As much as I would love to see that it would require way too much of everything going right. We haven't done well with everything going right since 2010.  

 

One of the other ways is to get something on the tail of the fropa from a cutter. Nice little wave with a modest 2-4/3-5 type of outcome. 

 

 

yeah..I think that is our 2nd best option...and certainly the most likely for a 3-5" event (14" for Bluemont, VA)....we just have to hope it shuts off before the changeover or we just go to drizzle and 35....then we have the superclipper and hope we get Hollywooded as you mentioned...and then the anomalous super strong ULL that takes a perfect track that usually gives CHO 4" while DCA is 41, and Montreal is 50

[NJwinter23]

yep

 

here is his interview from last year..he was pretty much wrong here

 

http://www.washingtonpost.com/blogs/capital-weather-gang/post/leading-forecaster-judah-cohen-favors-harsh-winter-for-washington-dc-east-coast/2012/11/21/ea5ff790-33e8-11e2-9cfa-e41bac906cc9_blog.html

 

 

I agree on that-- and then that LATE -AO was technically spring.  (Meteorological ..)

 

Yup it really really rubbed me the wrong way when he came out in april and claimed victory by throwing March into the equation when his forecast was for DJF. Would have had much more respect for him if he came out and said something along the lines of, "the direct temperature correlation part failed for the U.S. this winter, HOWEVER, the AO indicator of it did not...The -AO does not guarantee cold in the U.S. every time because other factors come into play too" ...But that wouldn't have been good for his product that he sells... I really respect his research and knowledge but that spin didnt sit right with me.

[uncle W]

the ao becomes a big factor when it's at one extreme or the other...otherwise it's just another player on the court...

[WinterWxLuvr]

AO_vs_nao_snow.gif

Hpe you can read it OK. All the dots below the dark horizontal line have a negative AO. All the dots to the right of the dark vertical line have a positive NAO. Note only 3 cases had a positive AO and negative NAO. but there were 16 or so with a negative AO and positive NAO. Note the graph is for DC 4 inch or greater storms.

If you want to look at the importance of the nina and AO together for 20 inch plus winters. The graph below shows why you don't want a nina and want a negative AO.

ao_enso_seasonal.png

Wes, thanks so much. That's how I remembered it. A neg AO and a pos NAO looks like a disaster. Quadrant 3 is obviously the best, but if one has to be positive, then we want both pos as quadrant one has the next most storms.

On the ENSO graph, niño wins, but only 10-7 on the 20+ Years. The 40+ is a different story though.

[mattie g]

Wes, thanks so much. That's how I remembered it. A neg AO and a pos NAO looks like a disaster. Quadrant 3 is obviously the best, but if one has to be positive, then we want both pos as quadrant one has the next most storms.

On the ENSO graph, niño wins, but only 10-7 on the 20+ Years. The 40+ is a different story though.

Looking at that, I'm pretty sure a +AO and -NAO is the death knell.

Since I really don't know much, I'd be curious as to the conditions this combination would cause, resulting in such a poor winter.

[usedtobe]

Looking at that, I'm pretty sure a +AO and -NAO is the death knell.

Since I really don't know much, I'd be curious as to the conditions this combination would cause, resulting in such a poor winter.

Not really a death knell.  There were 18 snowstorms with a positive AO versus about 32 with a positive NAO.  Of those 32 positive NAO events about half came with a negative AO and a positive NAO.  There were 44 negative AO events.  I didn't break down the 8 inch or greater events the same way. I would guess they are even more heavily weighted towards having both a negative AO and NAO but I don't know that for sure. 

[WxUSAF]

Looking at that, I'm pretty sure a +AO and -NAO is the death knell.

Since I really don't know much, I'd be curious as to the conditions this combination would cause, resulting in such a poor winter.

I think Wes' chart is very suggestive, and certainly suggests that the -AO is probably as important as a -NAO, all things considered.  But I'd say a little warning about the statistics of small numbers and drawing conclusions when the AO and NAO have a fairly high degree of correlation between themselves (i.e., they often have the same sign).  There are also times when the sign of the AO or NAO can be a little deceptive relative to what we "expect".  Take last year for instance with the mega -AO, yet we didn't go solidly below normal until very late in the winter.  Similarly, sometimes the way the NAO gets calculated can give you technical -NAOs or +NAOs with unexpected upper air patterns.  

 

Still, I think we can confidently draw the conclusion from that chart that a -AO/-NAO is the strongly favored situation to get big snows in DC. 

[H2O]

Not really a death knell.  There were 18 snowstorms with a positive AO versus about 32 with a positive NAO.  Of those 32 positive NAO events about half came with a negative AO and a positive NAO.  There were 44 negative AO events.  I didn't break down the 8 inch or greater events the same way. I would guess they are even more heavily weighted towards having both a negative AO and NAO but I don't know that for sure. 

 

Wes, didn't you once talk about how some of these events occurred when the AO/NAO were transitioning from either a huge +/- to the opposite state?  My memory might be off on this but being in a + doesn't always mean bad news if it is headed towards a more favorable number.

[WxUSAF]

Wes, didn't you once talk about how some of these events occurred when the AO/NAO were transitioning from either a huge +/- to the opposite state?  My memory might be off on this but being in a + doesn't always mean bad news if it is headed towards a more favorable number.

Big storms often change the NAO from - ---> +.  These are the so-called "Archambault events".  Naso much the case of + ----> -.  

http://journals.ametsoc.org/doi/abs/10.1175/2010MWR3362.1

 

Edit...ugh, did it backwards the first time.  

[mitchnick]

Big storms often change the NAO from + ---> -.  These are the so-called "Archambault events".  Naso much the case of - ----> +.  

http://journals.ametsoc.org/doi/abs/10.1175/2010MWR3362.1

I'm not certain we're disagreeing, but I'm pretty certain that the days leading up to 1/96 and 2/6/10 the NAO was rising from being in the cellar.

Not to say it was positive when the storms hit, but do recall seeing the number as calculated rising; I just can't find anything with a quick search that gives daily info.

[Bob Chill]

I'm not certain we're disagreeing, but I'm pretty certain that the days leading up to 1/96 and 2/6/10 the NAO was rising from being in the cellar.

Not to say it was positive when the storms hit, but do recall seeing the number as calculated rising; I just can't find anything with a quick search that gives daily info.

 

 

It works both ways it appears.

 

Jan 96 NAO:

 

 

 

Feb 2010 NAO:

 

 

 

96 was a transition from - to + and 10 was a strengthening NAO.

 

Big -nao's are bad for storms in the MA. I would have to check a ton of data to prove it but it's probably a fair assumption to say no big storms have hit the MA with a nao lower than -2 unless it is sharply rising at the time. 

[mitchnick]

It works both ways it appears.

 

Jan 96 NAO:

 

Jan 96 NAO.JPG

 

 

Feb 2010 NAO:

 

Feb 2010 NAO.JPG

 

 

96 was a transition from - to + and 10 was a strengthening NAO.

 

Big -nao's are bad for storms in the MA. I would have to check a ton of data to prove it but it's probably a fair assumption to say no big storms have hit the MA with a nao lower than -2 unless it is sharply rising at the time. 

thanks Bob....where did you get those graphs?

[WxUSAF]

It works both ways it appears.

 

Jan 96 NAO:

 

Jan 96 NAO.JPG

 

 

Feb 2010 NAO:

 

Feb 2010 NAO.JPG

 

 

96 was a transition from - to + and 10 was a strengthening NAO.

 

Big -nao's are bad for storms in the MA. I would have to check a ton of data to prove it but it's probably a fair assumption to say no big storms have hit the MA with a nao lower than -2 unless it is sharply rising at the time. 

I think '96 shows the classic Archambault type event.  The blizzard kept moving NE and turned into a big vortex that switched the NAO to positive.  Then we torched, got a major rain event and flooded.  

[Bob Chill]

thanks Bob....where did you get those graphs?

 

I make them. i have the AO/NAO/PNA daily datasets in text format. I graph with excel. 

[Bob Chill]

I think '96 shows the classic Archambault type event.  The blizzard kept moving NE and turned into a big vortex that switched the NAO to positive.  Then we torched, got a major rain event and flooded.  

 

Looks like it to me too. I need to take a look at the Feb 06 and 07 storms. They were unsual with the overall winter patterns. Kinda saved winter both years even if one was mostly sleet. That stuff froze into concrete and had serious longevity on the ground. My best friend's wife is an xray tech. She made a fortune from people trying to sled on a sleet pack. Waiting room was stuffed with broken bones for days following that storm. 

[mitchnick]

considering Canada, we're at least the same snow cover this year as 2009

 

 

2002 for giggles

[WxUSAF]

Among the raw numbers for NH snowcover at the end of October, I think we're going to do pretty well.  SAI is trickier.  

[mitchnick]

Among the raw numbers for NH snowcover at the end of October, I think we're going to do pretty well.  SAI is trickier.  

a lot is made of the change per Cohen

but if you look back I don't "believe" (and it's been a while since I looked at the numbers since I lost my link to snow cover and can't seem to locate it on the CPC site in a pinch) but very few winters at the top of the list for NH snow cover at the end of OCT were bad for us

[mitchnick]

a lot is made of the change per Cohen

but if you look back I don't "believe" (and it's been a while since I looked at the numbers since I lost my link to snow cover and can't seem to locate it on the CPC site in a pinch) but very few winters at the top of the list for NH snow cover at the end of OCT were bad for us

here was the link I was looking for but I see it is no longer maintained (as of 2010)

ftp://ftp.cpc.ncep.noaa.gov/wd52dg/snow/snw_cvr_area/NH_AREA

[WxUSAF]

a lot is made of the change per Cohen

but if you look back I don't "believe" (and it's been a while since I looked at the numbers since I lost my link to snow cover and can't seem to locate it on the CPC site in a pinch) but very few winters at the top of the list for NH snow cover at the end of OCT were bad for us

Having good coverage certainly doesn't hurt.  

 

If you want to feel sad though, go read some of HM's posts today in the Philly winter thread.  Talking about mega +AO potential this winter.  

[mitchnick]

Having good coverage certainly doesn't hurt.  

 

If you want to feel sad though, go read some of HM's posts today in the Philly winter thread.  Talking about mega +AO potential this winter.  

Meh.....Reality of the winter will be here soon enough. At least now I can still feel like we have a chance at something better than the last 3.

[mitchnick]

Having good coverage certainly doesn't hurt.  

 

If you want to feel sad though, go read some of HM's posts today in the Philly winter thread.  Talking about mega +AO potential this winter.  

I knew that active sun was not a good thing when it started last week and questioned it in the NE forum I believe.

always something....always something    

[WxUSAF]

I knew that active sun was not a good thing when it started last week and questioned it in the NE forum I believe.

always something....always something    

Well, I don't think the active sun alone is what would make the AO anomalously high this winter, but is just one more factor that would support a +AO. 

[mitchnick]

Having good coverage certainly doesn't hurt.  

 

If you want to feel sad though, go read some of HM's posts today in the Philly winter thread.  Talking about mega +AO potential this winter.  

HM potential winter cancel, potential uncancel!

http://www.americanwx.com/bb/index.php/topic/41091-winter-2013-2014/?p=2455192

[MN Transplant]

a lot is made of the change per Cohen

but if you look back I don't "believe" (and it's been a while since I looked at the numbers since I lost my link to snow cover and can't seem to locate it on the CPC site in a pinch) but very few winters at the top of the list for NH snow cover at the end of OCT were bad for us

 

I plotted DCA snow vs snowcover extent (week 43, end of October-ish) from the Rutgers snow lab.  There is a very slight positive with increased Northern Hemisphere and Eurasian snowcover, but the R-squared is like 0.01.  North American snowcover has absolutely no bearing, with a completely flat slope. 

 

The big 4 (78/79, 02/03, 95/96, and 09/10) all had medium or high extents, but so did the stinkers of 97/98 and 72/73 and the last two years.

[WxUSAF]

I plotted DCA snow vs snowcover extent (week 43, end of October-ish) from the Rutgers snow lab.  There is a very slight positive with increased Northern Hemisphere and Eurasian snowcover, but the R-squared is like 0.01.  North American snowcover has absolutely no bearing, with a completely flat slope. 

 

The big 4 (78/79, 02/03, 95/96, and 09/10) all had medium or high extents, but so did the stinkers of 97/98 and 72/73 and the last two years.

Did you make the same plot for DCA temp vs. snow cover extent?  I'd guess that has a higher correlation, but maybe it is also lower than I'd think.