Winter 2020-21 Discussion

[CAPE]

7 minutes ago, Maestrobjwa said:

Ya know...as we were going through the doldrums of last winter...I always wondered what's worse: A winter like last year that torches the entire time, or a la nina winter like that one that can break ya heart with the "we're too far southwest" close misses. 

I don't know man...I'm tempted to pick the torch, because I get nearby snow envy...but at least la ninas can still be cold sometimes (and scenery snow isn't completely out of the equation)

This area rarely sees big snow totals from a Nina, but can do ok with smaller events and scraps, and sometimes make it to average. That is a hell of a lot better than the crap we dealt with last winter. Ofc you have to completely tune out the fact that places further north are getting hammered from miller Bs while our region mostly gets jipped. We are who we are here, and we sure as fuuck aren't NNE.

[WinterWxLuvr]

I’ll second the post from above and say, with 100% certainty that there’s no way this winter will be as bad as last year. The WDI will Trump any other acronyms this go around. The winter doesn’t exactly have to do much to top that fiasco.

[CAPE]

CFS is on one of its better "runs" lately, 

Big picture h5 for Dec and Jan look pretty decent, and is a 'believable' look for a typical weak Nina. Feb doesn't look bad either, but with the massive +height anomalies it has in the EPAC, there would probably be more of a ridge in the east, although it also suggests a -NAO lol.

[psuhoffman]

@CAPE I’ll post the h5 composites later when I have time but looking at the last 15 Nina’s going back all the way to 1984 I see absolutely no significant correlation between the QBO and snowfall in our area. 1996 skews things horribly on those plots. Truth is 4 of the 5 worst Nina snowfall years in DC were negative QBO.  1989/2001/2008/2012. The one awful positive qbo winter was 2017. On the other hand if you take out 1996 the 2 next best snowfall Nina years at DC we’re 1986 and 2000 both +QBO. Truth is other than 1996 Nina’s all are a range between totally god awful and average wrt snowfall. With the stj absent in Nina’s getting above avg snow is just VERY unlikely. But the QBO does not seem to have any statistically significant predicting value on differentiating between the really awful Nina snowfall years and the decent ones.

When I have time I will look at the enso profiles (East/West/basin wide Nina) and north pac SSTs to see if one of those is a better predictor if Nina outcomes. Hopefully not north pac sst as those look like hot garbage right now also. 

[Maestrobjwa]

@psuhoffman And also when you have some time...could you run through exactly what factors made 1995-96 do what it did?

[CAPE]

2 hours ago, psuhoffman said:

@CAPE I’ll post the h5 composites later when I have time but looking at the last 15 Nina’s going back all the way to 1984 I see absolutely no significant correlation between the QBO and snowfall in our area. 1996 skews things horribly on those plots. Truth is 4 of the 5 worst Nina snowfall years in DC were negative QBO.  1989/2001/2008/2012. The one awful positive qbo winter was 2017. On the other hand if you take out 1996 the 2 next best snowfall Nina years at DC we’re 1986 and 2000 both +QBO. Truth is other than 1996 Nina’s all are a range between totally god awful and average wrt snowfall. With the stj absent in Nina’s getting above avg snow is just VERY unlikely. But the QBO does not seem to have any statistically significant predicting value on differentiating between the really awful Nina snowfall years and the decent ones.

When I have time I will look at the enso profiles (East/West/basin wide Nina) and north pac SSTs to see if one of those is a better predictor if Nina outcomes. Hopefully not north pac sst as those look like hot garbage right now also. 

Not surprising. As I have said, the QBO correlations seem nebulous, but in theory it impacts the strength of PV, and thus potentially the AO/NAO phases, so I would expect to see better correlation(-QBO) during a Nino, when HL blocking episodes are more prevalent (and we tend to get more snow).

[jaydreb]

1 hour ago, Maestrobjwa said:

@psuhoffman And also when you have some time...could you run through exactly what factors made 1995-96 do what it did?

I’m sure there were other reasons but the strongly -NAO helped.  

[snowman19]

1 hour ago, Maestrobjwa said:

@psuhoffman And also when you have some time...could you run through exactly what factors made 1995-96 do what it did?

95-96 was a weak Niña with a +PDO (strong positive at that), which is very unusual when you have a La Niña. You also were in the midst of a strong +AMO cycle with very warm North Atlantic SSTs, which favor -NAO and positive feedback into that -NAO

[snowman19]

2 hours ago, psuhoffman said:

@CAPE I’ll post the h5 composites later when I have time but looking at the last 15 Nina’s going back all the way to 1984 I see absolutely no significant correlation between the QBO and snowfall in our area. 1996 skews things horribly on those plots. Truth is 4 of the 5 worst Nina snowfall years in DC were negative QBO.  1989/2001/2008/2012. The one awful positive qbo winter was 2017. On the other hand if you take out 1996 the 2 next best snowfall Nina years at DC we’re 1986 and 2000 both +QBO. Truth is other than 1996 Nina’s all are a range between totally god awful and average wrt snowfall. With the stj absent in Nina’s getting above avg snow is just VERY unlikely. But the QBO does not seem to have any statistically significant predicting value on differentiating between the really awful Nina snowfall years and the decent ones.

When I have time I will look at the enso profiles (East/West/basin wide Nina) and north pac SSTs to see if one of those is a better predictor if Nina outcomes. Hopefully not north pac sst as those look like hot garbage right now also. 

Interesting, because Joe D’Aleo’s research showed +QBO/Niña being a bad combo for cold and snow in the east. I wonder what he was looking at to come to those conclusions 

[CAPE]

2 hours ago, snowman19 said:

Interesting, because Joe D’Aleo’s research showed +QBO/Niña being a bad combo for cold and snow in the east. I wonder what he was looking at to come to those conclusions 

Likely depends on the strength of the Nina. A moderate to strong Nina and +QBO likely eliminates any chance of HL blocking. A cold neutral/weak Nina AND a severely negative QBO may allow for either some HL blocking episodes or some favorable EPO periods, providing a mechanism for cold outbreaks in the east. PSU is saying his research finds no correlation, during a Nina winter, specifically between QBO and snowfall for the MA.

[nw baltimore wx]

I’d enjoy seeing some 2-4” clippers with cold, blustery winds behind them. It’s been awhile. 

[WinterWxLuvr]

8 minutes ago, nw baltimore wx said:

I’d enjoy seeing some 2-4” clippers with cold, blustery winds behind them. It’s been awhile. 

That’s like hoping to see a dinosaur lol.

[CAPE]

31 minutes ago, WinterWxLuvr said:

That’s like hoping to see a dinosaur lol.

Sorta like my bigfoot(Daryl) analogy with a -NAO.

[psuhoffman]

2 hours ago, CAPE said:

Likely depends on the strength of the Nina. A moderate to strong Nina and +QBO likely eliminates any chance of HL blocking. A cold neutral/weak Nina AND a severely negative QBO may allow for either some HL blocking episodes or some favorable EPO periods, providing a mechanism for cold outbreaks in the east. PSU is saying his research finds no correlation, during a Nina winter, specifically between QBO and snowfall for the MA.

When you start parting into such specific criteria you end up with not enough samples to get any meaningful results. Even 15 isn’t really enough of a sample to say much other than generalities. But there seems to be an even mix of decent Nina’s and dreg ones in both the +/- QBO category. 

[StormchaserChuck!]

4 hours ago, snowman19 said:

95-96 was a weak Niña with a +PDO (strong positive at that), which is very unusual when you have a La Niña. You also were in the midst of a strong +AMO cycle with very warm North Atlantic SSTs, which favor -NAO and positive feedback into that -NAO

Not really right about the AMO.

[BristowWx]

528 showing up at 384 Sep 5th.  Here we go folks. Rest up!

[WinterWxLuvr]

2 hours ago, BristowWx said:

528 showing up at 384 Sep 5th.  Here we go folks. Rest up!

Will end up 582

[Tom]

I think it's going to be a boom or bust but won't show it's hand, comes down the the NAO and history has shown expect a bust, I am holding out hope though.  Can and low end 25% snowfall if positive NAO up to 150% get a period of -NAO and nobody can predict the NAO this far in advance. 

[psuhoffman]

If we want to hold out hope the current global sst anomalies aren’t far off from this time in 2013. 
@Maestrobjwa if you want to know why 1996 was so good, the first half of that winter was dominated by a good Atlantic and pacific. A pronounced Aleutian low and west based NAO blocking.  The second half was much more variable but with recurring periods of Enough blocking to score a few more snow events. If your asking for a predictive reason...I can’t say for sure. Even now looking at the sst anomalies leading into that winter I wouldn’t have expected that. Sometimes anomalies happen and we don’t fully understand why. 

[North Balti Zen]

7 hours ago, Tom said:

I think it's going to be a boom or bust but won't show it's hand, comes down the the NAO and history has shown expect a bust, I am holding out hope though.  Can and low end 25% snowfall if positive NAO up to 150% get a period of -NAO and nobody can predict the NAO this far in advance. 

Your climate, friend, is much more favorable for finding some snow in a Nina than ours is in the majority of our part of the mid-Atlantic.  You should definitely have some hope. Down here, people are being more or less pretty realistic about what this set-up likely means.

[psuhoffman]

@CAPE the North Pacific sst profile is nothing close to the precursor to the worst Nina’s so that’s good. It’s not really all that close to the best either as it’s an anomalously warm profile for a developing Nina. So hard to say what that means.  The odd thing is the best Nina’s tended to have warmer water encroaching closer to the EPO domain while the worst were an ice bath all across the north pac.  Odd in that it’s the opposite of what you want the sst profile there ri be in a nino. The best overall pac sst match right now is actually late summer/fall of 2013 so that’s not all bad. But that was a weird year with an unexpected result so not sure rooting for a repeat of that is likely. 

[PhineasC]

On 8/21/2020 at 9:06 AM, North Balti Zen said:

Your climate, friend, is much more favorable for finding some snow in a Nina than ours is in the majority of our part of the mid-Atlantic.  You should definitely have some hope. Down here, people are being more or less pretty realistic about what this set-up likely means.

There’s a long history of Philly posters coming here pretending that they are in the same boat as DC, but we all know that is total BS. PHL can catch the ass-end of some Miller Bs, whereas DC basically never gets them. 

[CAPE]

On 8/21/2020 at 1:26 AM, psuhoffman said:

If we want to hold out hope the current global sst anomalies aren’t far off from this time in 2013. 
@Maestrobjwa if you want to know why 1996 was so good, the first half of that winter was dominated by a good Atlantic and pacific. A pronounced Aleutian low and west based NAO blocking.  The second half was much more variable but with recurring periods of Enough blocking to score a few more snow events. If your asking for a predictive reason...I can’t say for sure. Even now looking at the sst anomalies leading into that winter I wouldn’t have expected that. Sometimes anomalies happen and we don’t fully understand why. 

Since it is pretty clear we are heading towards a weak Nina for the winter at this juncture, how many weak Ninas/cold neutrals(just to expand a bit) over say the last 50 or so years have featured a -AO/-NAO for at least a third of the winter? Not that this correlates to above normal snowfall because we already know it doesn't the majority of the time with a Nina. Just trying to gauge the prospects of at least somewhat mitigating what will probably be a less than favorable Pacific, to at least improve the odds for some decent cold periods, and perhaps luck into a few well timed fluke events. Not that we will ever actually see a -AO/NAO in winter again lol.

[psuhoffman]

19 hours ago, CAPE said:

Since it is pretty clear we are heading towards a weak Nina for the winter at this juncture, how many weak Ninas/cold neutrals(just to expand a bit) over say the last 50 or so years have featured a -AO/-NAO for at least a third of the winter? Not that this correlates to above normal snowfall because we already know it doesn't the majority of the time with a Nina. Just trying to gauge the prospects of at least somewhat mitigating what will probably be a less than favorable Pacific, to at least improve the odds for some decent cold periods, and perhaps luck into a few well timed fluke events. Not that we will ever actually see a -AO/NAO in winter again lol.

I am currently doing my work looking at winter stuff and getting some ideas...but its going slow because honestly I have better things to do right now.  It's hard to get at some of that because simply using the monthly NAO numbers can hide the true pattern.  For instance, January 2000 comes in with a +NAO because periods of extreme + anomalies hides the 10 day period of -NAO in the means and as that month proves we don't need the whole month to be -NAO to get snowfall.  I am pretty sure everyone here remembers the snowy period that month more than the uneventful period that came before it.  In some other instances...features that impact the way the NAO is calculated but has very little bearing on our snow prospects impacts the raw numbers.  January and Feb 1996 come in near neutral on the NAO raw numbers...and just looking at that would not give you a good idea of what the true impact of blocking was that year.  

That said... going back to 1990 these are the splits

Cold Neutral Winters: 

96/97: Some blocking Dec and Jan but did us very little good in snowfall

2012/13 Blocking in Feb and Mar but did DC very little good in snowfall...did help places west and north of DC though

2013/14: very little NAO blocking but amazing EPO blocking that extended through the AO domain all winter, very odd for a cold enso winter

Weak Nina

2000/01: some major blocking periods in Dec and March that did DC no good except for 2 painful close misses!

05/06: Blocking periods in Dec and Feb that did lead to snow in DC, one of our better snowfall Nina's, this was one of the few examples where an excellent NAO offset a crap PAC

08/09: There were a couple periods of good west based blocking in Jan and Feb but it did DC little good wrt snowfall, cold/dry periods

2016/17: no blocking until March

2017/18: no blocking until March

Moderate Nina

1995/96 no need to explain

2011/12: no blocking dumpster fire winter start to finish

Strong Nina

1998/99: great blocking in March that did lead to snow in DC

1999/2000: Blocking in January that did lead to snow in DC

2007/08: no blocking dumpster fire winter 

2010/11: Great blocking in December and January that lead to "some" snow in DC but a mostly frustrating period watching Philly and NYC get record snowfalls 

Some observations so far...there is very little observable difference in our chances of a decent snowfall based on the strength of the Nina.  First of there are 2 obvious outliers in 1996 and 2014.  Each due to extreme high latitude ridging, one in the NAO domain and one in the EPO.  One was a cold neutral and one a moderate nina.  I think we can simply toss both as the obvious outliers.  That doesn't mean they can't happen again, just that they are anomalies that shouldn't be "expected" in a cold enso winter and that skew the mean of all the other more typical years so it's better to just chalk them up to "bleep happens".  But there are some decent and some awful snowfall years in each of the subsets of cold enso winters.  Actually only 1 of the 4 strong nina's in the last 30 years was a really bad awful winter wrt snowfall in DC.  The other 3 were all in the more "decent" nina snowfall outcome range (which is still probably way below the standards of some people in here, they know who they are, and they might want to just take a nap until 2022).  

There are 2 clear cold enso types that all the other years fall into.  A warmer and a cold variety.   Unfortunately the cold variety does NOT mean a lot of snow.  They are typically mostly frustrating years like 2001/2009/2011/2018 where DC eeks its way to a slightly below avg (near median) snowfall winter with clippers and being on the fringe edge of northern stream storms and watches Philly and NYC get buried by miller b after miller b.  However, they do not typically end up complete awful snow-less winters like last year.  

The warmer type opens the door to a complete crap winter in DC like 2008/2012/2017 where there is virtually no snow.  But there were also some examples where a period of NAO blocking was able to provide either a period of snowfall or an anomalous storm (1999/2000/2006) within an overall warm nina winter.  

What differentiates the colder/warmer cold enso types seems to be a combination of the orientation of the pacific ridge in conjuncture with any AO/NAO blocking.  If the PAC ridge orients itself further north and can encroach into AK and the northern EPO domain...then it can lead to a colder regime into the northeastern US.  This type also seems to be in conjunction with a bit more propensity for NAO blocking.  The warmer type seems to have a pac ridge centered further south (like last winter) which makes sense as that would act to enhance the jet to its north and speed up the polar vortex and...well we saw the results of that!  

So far being able to easily identify markers that would help predict ahead of time which type is coming (or the possibility we get one of the 96/2014 type anomalies) is not easy.  From a pacific SST stand point there is definitely some tells that you do NOT want, like a very cold northeast pac sst profile...and we don't have that.  But there are still a mix of good/bad results in the set without that marker.   I think @Isotherm may have a much better methodology of using the actual atmospheric circulation patterns to predict these phases rather than the SST anomalies but I am just starting to dip my toe into that pond.  Hopefully he will post some on that soon.   I am not done analyzing things yet, and we are still super early so factors will change yet, but it's clear this coming winter will favor below avg snowfall simply from the cold enso factor.  How much below avg depends on those other factors.  

 

[psuhoffman]

You can see the difference in the Pacific ridge between the colder years and warmer

Colder Nina years

Warmer Nina years

[CAPE]

1 hour ago, psuhoffman said:

I am currently doing my work looking at winter stuff and getting some ideas...but its going slow because honestly I have better things to do right now.  It's hard to get at some of that because simply using the monthly NAO numbers can hide the true pattern.  For instance, January 2000 comes in with a +NAO because periods of extreme + anomalies hides the 10 day period of -NAO in the means and as that month proves we don't need the whole month to be -NAO to get snowfall.  I am pretty sure everyone here remembers the snowy period that month more than the uneventful period that came before it.  In some other instances...features that impact the way the NAO is calculated but has very little bearing on our snow prospects impacts the raw numbers.  January and Feb 1996 come in near neutral on the NAO raw numbers...and just looking at that would not give you a good idea of what the true impact of blocking was that year.  

That said... going back to 1990 these are the splits

Cold Neutral Winters: 

96/97: Some blocking Dec and Jan but did us very little good in snowfall

2012/13 Blocking in Feb and Mar but did DC very little good in snowfall...did help places west and north of DC though

2013/14: very little NAO blocking but amazing EPO blocking that extended through the AO domain all winter, very odd for a cold enso winter

Weak Nina

2000/01: some major blocking periods in Dec and March that did DC no good except for 2 painful close misses!

05/06: Blocking periods in Dec and Feb that did lead to snow in DC, one of our better snowfall Nina's, this was one of the few examples where an excellent NAO offset a crap PAC

08/09: There were a couple periods of good west based blocking in Jan and Feb but it did DC little good wrt snowfall, cold/dry periods

2016/17: no blocking until March

2017/18: no blocking until March

Moderate Nina

1995/96 no need to explain

2011/12: no blocking dumpster fire winter start to finish

Strong Nina

1998/99: great blocking in March that did lead to snow in DC

1999/2000: Blocking in January that did lead to snow in DC

2007/08: no blocking dumpster fire winter 

2010/11: Great blocking in December and January that lead to "some" snow in DC but a mostly frustrating period watching Philly and NYC get record snowfalls 

Some observations so far...there is very little observable difference in our chances of a decent snowfall based on the strength of the Nina.  First of there are 2 obvious outliers in 1996 and 2014.  Each due to extreme high latitude ridging, one in the NAO domain and one in the EPO.  One was a cold neutral and one a moderate nina.  I think we can simply toss both as the obvious outliers.  That doesn't mean they can't happen again, just that they are anomalies that shouldn't be "expected" in a cold enso winter and that skew the mean of all the other more typical years so it's better to just chalk them up to "bleep happens".  But there are some decent and some awful snowfall years in each of the subsets of cold enso winters.  Actually only 1 of the 4 strong nina's in the last 30 years was a really bad awful winter wrt snowfall in DC.  The other 3 were all in the more "decent" nina snowfall outcome range (which is still probably way below the standards of some people in here, they know who they are, and they might want to just take a nap until 2022).  

There are 2 clear cold enso types that all the other years fall into.  A warmer and a cold variety.   Unfortunately the cold variety does NOT mean a lot of snow.  They are typically mostly frustrating years like 2001/2009/2011/2018 where DC eeks its way to a slightly below avg (near median) snowfall winter with clippers and being on the fringe edge of northern stream storms and watches Philly and NYC get buried by miller b after miller b.  However, they do not typically end up complete awful snow-less winters like last year.  

The warmer type opens the door to a complete crap winter in DC like 2008/2012/2017 where there is virtually no snow.  But there were also some examples where a period of NAO blocking was able to provide either a period of snowfall or an anomalous storm (1999/2000/2006) within an overall warm nina winter.  

What differentiates the colder/warmer cold enso types seems to be a combination of the orientation of the pacific ridge in conjuncture with any AO/NAO blocking.  If the PAC ridge orients itself further north and can encroach into AK and the northern EPO domain...then it can lead to a colder regime into the northeastern US.  This type also seems to be in conjunction with a bit more propensity for NAO blocking.  The warmer type seems to have a pac ridge centered further south (like last winter) which makes sense as that would act to enhance the jet to its north and speed up the polar vortex and...well we saw the results of that!  

So far being able to easily identify markers that would help predict ahead of time which type is coming (or the possibility we get one of the 96/2014 type anomalies) is not easy.  From a pacific SST stand point there is definitely some tells that you do NOT want, like a very cold northeast pac sst profile...and we don't have that.  But there are still a mix of good/bad results in the set without that marker.   I think @Isotherm may have a much better methodology of using the actual atmospheric circulation patterns to predict these phases rather than the SST anomalies but I am just starting to dip my toe into that pond.  Hopefully he will post some on that soon.   I am not done analyzing things yet, and we are still super early so factors will change yet, but it's clear this coming winter will favor below avg snowfall simply from the cold enso factor.  How much below avg depends on those other factors.  

 

Excellent write up. The bolded is the bottom line, and pretty much what I expected would be the case.

Another "thought". With SSTs basin wide on fire lately, can a weak Nina even produce the same sort of atmospheric response as it would have say 20 years ago? At some point you would think a sliver of slightly negative sst anomalies would get overwhelmed, and have about the same 'impact' on the atmosphere as a neutral/warm neutral ENSO... more variable/less "typical".

[griteater]

psu - enjoyed your write-up.  Regarding the orientation of the North Pac High during cool Enso winters, I wrote a bit about this in an outlook from winter 17-18.  Take a look at the section titled "North Pacific Pattern"

https://www.americanwx.com/bb/topic/50432-griteaters-winter-outlook-17-18/

[psuhoffman]

15 minutes ago, griteater said:

psu - enjoyed your write-up.  Regarding the orientation of the North Pac High during cool Enso winters, I wrote a bit about this in an outlook from winter 17-18.  Take a look at the section titled "North Pacific Pattern"

https://www.americanwx.com/bb/topic/50432-griteaters-winter-outlook-17-18/

Thank you will definitely take a look!

[psuhoffman]

31 minutes ago, CAPE said:

Excellent write up. The bolded is the bottom line, and pretty much what I expected would be the case.

Another "thought". With SSTs basin wide on fire lately, can a weak Nina even produce the same sort of atmospheric response as it would have say 20 years ago? At some point you would think a sliver of slightly negative sst anomalies would get overwhelmed, and have about the same 'impact' on the atmosphere as a neutral/warm neutral ENSO... more variable/less "typical".

I’m sure there will be an effect due to the changing pac base state, but Im not sure what that will be. The warmer waters around enso could act to enhance the effect due to greater contrast and gradient. On the other hand the warmer profile could wash out the weak cold anomalies.
 

Interestingly there gave only been 4 truly epic snowfall winters in the last 30 years. And 2 were in warm enso and 2 cold. So Im not sure the odds of a 30”+ DC winter is actually affected much by enso. But the odds of beating avg definitely are. Without the STJ we simply have less chances of getting lucky and any snow here is an anomaly and requires luck.  To get the epic winters requires some version of amazing high latitude ridging (EPO/AO/NAO) and that can override enso when it happens. But it’s so rare and hard to predict ahead of time. 

[snowman19]

19 hours ago, psuhoffman said:

I’m sure there will be an effect due to the changing pac base state, but Im not sure what that will be. The warmer waters around enso could act to enhance the effect due to greater contrast and gradient. On the other hand the warmer profile could wash out the weak cold anomalies.
 

Interestingly there gave only been 4 truly epic snowfall winters in the last 30 years. And 2 were in warm enso and 2 cold. So Im not sure the odds of a 30”+ DC winter is actually affected much by enso. But the odds of beating avg definitely are. Without the STJ we simply have less chances of getting lucky and any snow here is an anomaly and requires luck.  To get the epic winters requires some version of amazing high latitude ridging (EPO/AO/NAO) and that can override enso when it happens. But it’s so rare and hard to predict ahead of time. 

Read an old article from HM, he showed that a La Niña/+QBO results in a poleward Aleutian ridge in December. A La Niña/-QBO combo results in a flatter Aleutian high in December