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CAPE

Winter 2020-21 Discussion

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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".

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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!

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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. 

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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 

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Just got the new Farmers Almanac...”sheets of sleet” for LWX.  Curious use of words.  Chuckle worthy but traditional. 

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3 hours ago, BristowWx said:

Just got the new Farmers Almanac...”sheets of sleet” for LWX.  Curious use of words.  Chuckle worthy but traditional. 

What I found interesting about them last year was...not even THEY forecasted in big storms for last winter like they usually tend to do! That shoulda warned us of last winter's drudgery, lol

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2 hours ago, Maestrobjwa said:

What I found interesting about them last year was...not even THEY forecasted in big storms for last winter like they usually tend to do! That shoulda warned us of last winter's drudgery, lol

Agree.  They do mention the solar minimum but offset by continued warming.  They are spitballing like the rest of us.  Anything would be better than last winter.  

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September edition of the CanSIPS is out. My glass half full overview-

Overall it looks less torchy for the winter months than the previous run. For December, not a half bad look, and verbatim just about average temps. At h5 the positive heights in the EPAC are such that the mean ridge is decently placed..close enough for perhaps a +PNA at times. Beyond that the heights shift westward in Jan, but still not a terrible look for the east coast- maybe a gradient type pattern. By Feb the EPAC ridge is a monster, max +height anomalies south of the Aleutians, and whatever winter there was would be over. Up top, December looks like a neutral AO/NAO, Jan a somewhat +AO/NAO,  Feb ++AO/NAO. So not much help in the high latitudes.

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3 hours ago, CAPE said:

September edition of the CanSIPS is out. My glass half full overview-

Overall it looks less torchy for the winter months than the previous run. For December, not a half bad look, and verbatim just about average temps. At h5 the positive heights in the EPAC are such that the mean ridge is decently placed..close enough for perhaps a +PNA at times. Beyond that the heights shift westward in Jan, but still not a terrible look for the east coast- maybe a gradient type pattern. By Feb the EPAC ridge is a monster, and whatever winter there was would be over. Up top, December looks like a neutral AO/NAO, Jan a somewhat +AO/NAO,  Feb ++AO/NAO. So not much help in the high latitudes.

It honestly looks like a typical La Niña “front end loaded” (Dec - mid January) winter. It’s truly amazing that the models continue to advertise +NAO/+AO, just amazingly persistent for years now. December does look more neutral like you said

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On 8/20/2020 at 6:25 PM, nw baltimore wx said:

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

Something like Feb. 14, 2015 would be kinda cool!!  That wasn't really 2-4" area-wide, but I got like 2" in an hour or so followed by gusty winds and temperatures plummeted into the teens for the next day or so, as an Arctic front went through.  One of the coolest "mini events" I can remember.

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11 pages for a Winter 2020-21 thread, and we're barely into September...oy gevalt!!  Either desperation or hope, I'm not sure which.

I didn't read the whole thing, but has Ji canceled this upcoming winter yet?  And how many times? :lol:  Do we have Panic Room previews??  @WxWatcher007 promised so many new amenities this upcoming season for the wayward weenies!!

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On 8/20/2020 at 5:15 AM, CAPE said:

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

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.

2039074935_cfsruns.thumb.png.4135f4bec229babd8870729e877f69bb.png

The latest CFS runs now have a torch for December lol, but then a pretty good look for January- similar to above but better- deeper trough and hints of a bit of HL help. Looks pretty similar to h5 back in Jan of 2018 when we had the cold period(and the bomb cyclone). February doesn't look terrible either. All just for fun ofc at this juncture with these climate models.

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2 hours ago, North Balti Zen said:

Sounds like a CFS CFS blend gets us three months of winter. Off to pitch my analysis to Bastardi...

Yeah a CanSIPS Dec followed by a CFS Jan and Feb would be pretty decent.

A month from now we can reanalyze.This is fun.

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3 hours ago, snowman19 said:

Looks like this is going to be a +QBO winter, August’s QBO number went up to +4.78

QBO won't make much difference. Its impacts are nebulous imo, and even more so in Nina. The AO/NAO is pretty much guaranteed to be positive for the winter months based on persistence and general correlation to Nina. Not to say we wont have a few periods where it is less positive or neutral. Maybe the solar minimum will save the day(winter).

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44 minutes ago, CAPE said:

QBO won't make much difference. Its impacts are nebulous imo, and even more so in Nina. The AO/NAO is pretty much guaranteed to be positive for the winter months based on persistence and general correlation to Nina. Not to say we wont have a few periods where it is less positive or neutral. Maybe the solar minimum will save the day(winter).

Keep this in mind though...going back 50 years DC hasn’t had a warning level snow during a Nina without some NAO blocking preceding the event. I went back and looked at EVERY Nina warning event a few years ago and found every one was set up by blocking. In some cases it was a bootleg block that didn’t necessarily tank the numerical NAO.  But when I examined the h5 it was there. So absent any blocking kiss any chances of more than minor events in DC goodbye. 

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11 hours ago, psuhoffman said:

Keep this in mind though...going back 50 years DC hasn’t had a warning level snow during a Nina without some NAO blocking preceding the event. I went back and looked at EVERY Nina warning event a few years ago and found every one was set up by blocking. In some cases it was a bootleg block that didn’t necessarily tank the numerical NAO.  But when I examined the h5 it was there. So absent any blocking kiss any chances of more than minor events in DC goodbye. 

Blocking would be lovely, but as we all know, its pretty rare during winter lately. We could see something transient ofc, but if this winter is to feature a colder period, I am inclined to think it will probably require a favorable EPAC for a time, something like Jan of 2018. No one in DC area should expect more than a low end warning event or 2 at best, and hopefully a few 1-2" deals. That would be a major win after the debacle of last winter.

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It's like.. the pattern defaults, and the NAO is a sub-index at this point. It would be nice to see that change. I say that too about the 10mb PV, it just seems par for the course for the pattern of late and the Nina is weak around -0.7. 

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1 hour ago, CAPE said:

Blocking would be lovely, but as we all know, its pretty rare during winter lately. We could see something transient ofc, but if this winter is to feature a colder period, I am inclined to think it will probably require a favorable EPAC for a time, something like Jan of 2018. No one in DC area should expect more than a low end warming event or 2 at best, and hopefully a few 1-2" deals. That would be a major win after the debacle of last winter.

I don’t disagree, just pointing out the fact that in a Nina DC really needs some HL blocking to get a decent snow. It was shocking how much so. In all other enso conditions DC can luck their way to a warning event without blocking.  But in a Nina even cold periods absent blocking typically end up dry. No stj tends to be a big problem. Can’t luck into a progressive southern steam wave. Need a strong block to force the northern stream to dig under us and pick up some gulf moisture.   I’m not saying we get blocking.  And we don’t need long periods, we could cash in with transient blocking.  Just saying the Nina’s that featured a raging +NAO wall to wall like last year...well they ended up like last year.  We need to hope we get at least some favorable looks up top (even if only temporary) or the panic room will be very busy!

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@CAPE of course records are made to be broken. I’m sure there have been big snow in a Nina absent blocking if you go back far enough. I’m sure it’s possible. Just very unlikely. Kinda like 2010.  But maybe this year is the 1/100 fluke. But if you told me today the NAO behaves like last winter and is wall to wall positive I would bet DC ends up under 5” snowfall!  

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9 hours ago, psuhoffman said:

I don’t disagree, just pointing out the fact that in a Nina DC really needs some HL blocking to get a decent snow. It was shocking how much so. In all other enso conditions DC can luck their way to a warning event without blocking.  But in a Nina even cold periods absent blocking typically end up dry. No stj tends to be a big problem. Can’t luck into a progressive southern steam wave. Need a strong block to force the northern stream to dig under us and pick up some gulf moisture.   I’m not saying we get blocking.  And we don’t need long periods, we could cash in with transient blocking.  Just saying the Nina’s that featured a raging +NAO wall to wall like last year...well they ended up like last year.  We need to hope we get at least some favorable looks up top (even if only temporary) or the panic room will be very busy!

I know this is not DC- but I am basically on the same latitude and at low elevation- and I can think of 3 warning level events right off the top of my head in the last 2 Nina winters. The one in March I think did have some blocking, but the other 2 didn't. They were both coastal scrapers with 10" plus at the beaches, about 6 here, and little to nothing for DC. Just dumb luck I suppose.

eta- being further East/NE does help in  a Nina with catching the edge of a Miller B sometimes. Happened here in Dec 2010 (the storm never to be mentioned). Got 5" or so from that, and there was 10+ a few miles to my east, but that period did feature a -NAO IIRC.

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11 hours ago, CAPE said:

Odd how here- I know this is not DC, but basically on the same latitude and at low elevation- I can think of 3 warning level events right off the top of my head in the last 2 Nina winters. The one in March I think did have some blocking, but the other 2 didn't. They were both coastal scrapers with 10" plus at the beaches, about 6 here, and little to nothing for DC. Just dumb luck I suppose.

eta- being further East/NE does help in  a Nina with catching the edge of a Miller B sometimes. Happened here in Dec 2010 (the storm never to be mentioned). Got 5" or so from that, and that period did feature a -NAO IIRC.

You are actually in a better spot to try to luck into a warning level snow in a Nina without blocking. You can catch the west edge of some progressive late developing storms like are common in a Nina. DC is just too far west. Heck even with blocking they miss a lot but it at least gives them a chance. All the decent Nina snows in DC had blocking help.  March 18, January 2011, March 2009, February 2006, Jan 2000, March 99, and all the 96 storms featured at least some blocking leading up to them.  

 

 

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it has begun

URGENT - WINTER WEATHER MESSAGE
National Weather Service Missoula MT
1235 PM MDT Fri Sep 4 2020

MTZ007-043-051845-
/O.NEW.KMSO.WS.A.0008.200907T1800Z-200908T0400Z/
Butte/Blackfoot Region-Potomac/Seeley Lake Region-
1235 PM MDT Fri Sep 4 2020

...WINTER STORM WATCH IN EFFECT FROM MONDAY AFTERNOON THROUGH
MONDAY EVENING ABOVE 6000 FEET...

* WHAT...Heavy snow possible above 6000 feet. Total snow
  accumulations of 2 to 4 inches with up to 6 inches above 7000
  feet possible.

* WHERE...Higher terrain of the Butte/Blackfoot Region and
  Potomac/Seeley Lake Region.

* WHEN...From Monday afternoon through Monday evening.

* IMPACTS...Persons with plans to be in the mountains or
  backcountry will experience very cold, wet and windy weather
  which will produce exceptionally raw and potentially dangerous
  conditions.

--------------------------------------------

URGENT - WINTER WEATHER MESSAGE
National Weather Service Missoula MT
1235 PM MDT Fri Sep 4 2020

MTZ002-051845-
/O.NEW.KMSO.WS.A.0008.200907T1500Z-200908T0400Z/
West Glacier Region-
1235 PM MDT Fri Sep 4 2020

...WINTER STORM WATCH IN EFFECT FROM MONDAY MORNING THROUGH
MONDAY EVENING ABOVE 6000 FEET...

* WHAT...Heavy snow possible above 6000 feet. Total snow
  accumulations of 2 to 4 inches possible at Logan Pass. Up to 7
  inches are possible above 7000 feet.

* WHERE...Higher terrain of the West Glacier Region.

* WHEN...From Monday morning through Monday evening.

* IMPACTS...Persons with plans to be in the mountains or
  backcountry will experience very cold, wet and windy weather
  which will produce exceptionally raw and potentially dangerous
  conditions.
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This is a pretty healthy looking La Niña at the moment. It’s really becoming more of a basin-wide event....region 4 hasn’t stayed this consistently cool for quite a long time: nino4.pngcdas-sflux_ssta_global_1.png 

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