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Countdown to Winter 20-21: Pattern Drivers & Evolution


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I'm starting to get a little more excited for early-mid December. It looks like the Pacific jet will retract significantly, which is the real reason for the retrograding Alaskan LP. Upper level diverg

Hey all!   I apologize for my absence as i'm currently in the "heat" of finishing up my undergrad, working on some side projects, and working with my advisor regarding, well grad school; tha

Really big shift on the 00z GEFS in the 8-10 day range.      This doesn't look like a huge deal, but the more amplified +PNA allows for much more northern stream interaction. This

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2 hours ago, griteater said:

Hello @donsutherland1, I wanted to offer a few thoughts on the stat where you indicated that "9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO"

 

The QBO is utilized in various ways with respect to seasonal forecasting, but IMO, it's best use with winter forecasting is not so much with the AO/NAO, but rather, with the configuration of the North Pacific High/Ridge that is common during La Nina winters.  A North Pacific ridge is almost certain to be present in the mean pattern during Cool ENSO / La Nina winters when the Jul-Oct averaged AAM is negative (which has been the case thus far for Jul-early Sep).

 

Anthony Masiello's findings from 2012 showed that more poleward north pacific ridges were favored during +QBO winters, while north pacific ridges that were suppressed to the south were more favored during -QBO winters.  A key element here is that the designation of the QBO for this purpose was in the lower stratosphere (roughly Nov-Feb averaged at 45mb) as opposed to the typical level used with QBO analysis which is at 30mb. 

 

While the QBO began to behave much more erratic than normal at the first part of 2020, it appears to have resumed with a more typical progression as the positive QBO has more firmly established itself in recent months in the middle stratosphere and descending into the lower stratosphere.  For the upcoming winter, I would anticipate the QBO to average positive for Nov-Feb averaged at 45mb - most similar to the winter of 2010-2011 when compared to other cool ENSO winters. 

 

See QBO Charts:

NASA QBO Chart

Free Univ of Berlin QBO Chart

 

Below is a list of what I have for the last 11 La Nina winters that followed El Nino, along with the Nov-Feb avg 45mb QBO, then the placement of the north pacific ridge averaged for Dec-Mar.

 

La Nina Winter That Followed El Nino Winter / Jan-Feb avg QBO at 45mb / Placement of North Pacific Ridge avg for Dec-Mar

2010-2011 / Positive QBO / north/poleward north pacific ridge (specifically, displaced to the NW)

2007-2008 / Negative QBO / south/suppressed north pacific ridge (specifically, displaced to the SW)

2005-2006 / Negative QBO / south/suppressed north pacific ridge (specifically, displaced to the SW)

1998-1999 / Negative QBO / south/suppressed north pacific ridge (specifically, displaced to the SW)

1995-1996 / Positive QBO / north/poleward north pacific ridge (specifically, displaced to the NW)

1988-1989 / Positive QBO / north/poleward north pacific ridge (specifically, displaced to the NE)

1983-1984 / Neutral QBO / no clear distinction overall in the north pacific

1973-1974 / Positive QBO / north/poleward north pacific ridge (specifically, displaced to the NW)

1970-1971 / Negative QBO / north/poleward north pacific ridge (specifically, displaced to the NW)

1964-1965 / Positive QBO / north/poleward north pacific ridge (specifically, displaced to the NW)

1954-1955 / Negative QBO / south/suppressed north pacific ridge (specifically, displaced to the SW)

 

Of the 11 winters, the only one that didn't follow the QBO/North Pacific Ridge placement theory was the winter of 1970-1971.

 

Here are 500mb Height / U.S. Temperature composites of the Positive QBO winters from the list: 

 

543070605_Sep9NinaPosQBO.png.b08d595893ad92d0f7876bd96c35464e.png

 

 

And here are 500mb Height / U.S. Temperature composites of the Negative QBO winters from the list (I left off the 70-71 winter):

 

795617113_Sep9NinaNegQBO.png.8098135465eea56fc7a9085a93bad00f.png

 

Clearly, the Positive QBO composite with the more poleward north pacific ridge offers more potential for cold air intrusion into the lower 48 east of the Rockies compared with the Negative QBO composite.

 

One other thing to look for is the Oct-Nov 500mb pattern over the NE Pacific / Alaska / NW Canada.  Winters with a more poleward north pacific ridge tend to be absent of negative height anomalies in the Bering Sea, Alaska, and NW Canada during Oct-Nov....while, winters with a more southward displaced north pacific ridge tend to contain solid negative height anomalies in the eastern Gulf of Alaska extending up into portions of the Bering Sea, Alaska, and/or NW Canada.

 

Bottom Line: I would expect the upcoming winter to exhibit a more poleward north pacific ridge in the mean pattern as long as: 1) the QBO progression continues in a more typical manner as seen in the past few months, and 2) the Oct-Nov averaged 500mb pattern doesn't contain negative height anomalies in the eastern Gulf of Alaska extending up into portions of the Bering Sea, Alaska, and/or NW Canada  

Outstanding post.

 

When it comes to a future winter forecast, I will most definitely look beyond ENSO. ENSO is just used for a starting point in this near daily discussion. There are more pieces to the proverbial puzzle. I also agree about a QBO+ being more likely than not this winter.

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9 minutes ago, Allsnow said:

I have zero expectations this winter. It’s probably better that way, then going in expecting a good winter. 
 

The tropical forcing currently is textbook Niña and that’s not a good sign. We won’t know How that  looks and the Pv until December but I’m leaning towards a clunker.

Would agree but never know, 10-11 was forecast as a clunker and we lucked out for 30-40 days....

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5 hours ago, Brian5671 said:

Would agree but never know, 10-11 was forecast as a clunker and we lucked out for 30-40 days....


Yeah, there are quite a few conflicting signals showing up for the winter.

 

La Nina, but looks like more East-Based La Niña at this point. 

+EPO/NAO don’t look nearly as likely based on current SSTA 
QBO looks like it’s just outside the +/- 10mps, but not so strong that Blocking is unlikely.

 

my current thoughts are cold and dry with quite a few 1-3, 2-4” events from clippers. Below snowfall, but not a nada winter. There will be things to track, just think it’s either going to be way west, or way East. 

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7 hours ago, PB GFI said:

I like the Neg in Alaska idea

 

Pumps the ridge in the east, break out the shorts 

 

ps2png-gorax-green-007-6fe5cac1a363ec1525f54343b6cc9fd8-LA0b7N.png

The DJF ensemble mean anomaly is 1-2 degrees C above normal. Warm anomalies stretch almost unbroken from sea to shining sea on the September run of the seasonal European guidance. 

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On 9/6/2020 at 1:24 AM, Snowy Hibbo said:

G’day everyone,

 

My first seasonal prediction for the NH this season:

https://longrangesnowcenter.net/2020/09/06/early-september-seasonal-2020-21-winter-preliminary-outlook/
 

Western & Central US and the Northern Alps to benefit from a Canadian Vortex/Aleutian High and +NAO driven weather outlook for the winter ahead from the preliminary look of factors (still got more to loom at in coming weeks...).


Not looking as great for the Eastern US, could be okay for New England, will get more specific closer to winter.


- Zac

Here a good report on the upcoming winter from @Snowy Hibbo. Meant to include in the original. Have a read!

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  • 33andrain changed the title to Countdown to Winter 20-21: Pattern Drivers & Evolution

we jst got a nice cool airmass with a positive ao and nao...maybe we will have a cooler winter than whats being forecast by some...seeing a storm exit stage right and missing us is not a great sign if you are looking for a snowy winter...all signs aside its still to early to get exicited or pessimistic...

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5 minutes ago, uncle w said:

we jst got a nice cool airmass with a positive ao and nao...maybe we will have a cooler winter than whats being forecast by some...seeing a storm exit stage right and missing us is not a great sign if you are looking for a snowy winter...all signs aside its still to early to get exicited or pessimistic...

Yeah, way too early, even a month from now may be a bit too early.  If today were November 19 rather than September 19, I would be leaning cold and dry, probably close to average snowfall, but it isn't November 19. lol.

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On 9/18/2020 at 11:05 AM, Allsnow said:

I have zero expectations this winter. It’s probably better that way, then going in expecting a good winter. 
 

The tropical forcing currently is textbook Niña and that’s not a good sign. We won’t know How that  looks and the Pv until December but I’m leaning towards a clunker.

Strongly agree with the first sentence.

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the two best winters of my life have been la nina's...1995-96 and 2010-11...the two worst winters were el nino's...1972-73 and 1997-98...a typical horrid winter like last winter was an el nino winter...la nina has seen its share of clunkers but were colder on average and clunkers were around 12" for a season while el nino clunkers averaged under 10"...

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52 minutes ago, uncle w said:

the two best winters of my life have been la nina's...1995-96 and 2010-11...the two worst winters were el nino's...1972-73 and 1997-98...a typical horrid winter like last winter was an el nino winter...la nina has seen its share of clunkers but were colder on average and clunkers were around 12" for a season while el nino clunkers averaged under 10"...

I thought 1993-94 was a bit better than 2010-11 because it was a longer duration.  2010-11 pretty much shut down after the early Feb ice storm.  Then again, from the boxing day blizzard to the late January 4 hour thunder snow blizzard that produced nearly 20 inches, makes this one memorable.  I wasn't born until March 1973 and have faint memories of the late 1970's winters but I would think 1976-77 and 1977-78 were at the top of your best list as well.  2002-03 is probably #3 for me following 1995-96 and 1993-94.

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37 minutes ago, MR FREEZE said:

I thought 1993-94 was a bit better than 2010-11 because it was a longer duration.  2010-11 pretty much shut down after the early Feb ice storm.  Then again, from the boxing day blizzard to the late January 4 hour thunder snow blizzard that produced nearly 20 inches, makes this one memorable.  I wasn't born until March 1973 and have faint memories of the late 1970's winters but I would think 1976-77 and 1977-78 were at the top of your best list as well.  2002-03 is probably #3 for me following 1995-96 and 1993-94.

1993-94 was dead nuts neutral, if anything a bit positive 

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1 hour ago, MR FREEZE said:

I thought 1993-94 was a bit better than 2010-11 because it was a longer duration.  2010-11 pretty much shut down after the early Feb ice storm.  Then again, from the boxing day blizzard to the late January 4 hour thunder snow blizzard that produced nearly 20 inches, makes this one memorable.  I wasn't born until March 1973 and have faint memories of the late 1970's winters but I would think 1976-77 and 1977-78 were at the top of your best list as well.  2002-03 is probably #3 for me following 1995-96 and 1993-94.

1995-96 and 2010-11 are the top two snowiest winters since I was born...1960-61 is my boyhood winter and that shut off after the first week in Feb like 2011...77-78 lacks a good December...the rest was great...1993-94 is right up there but to many storms ended as a mix or rain and did not have a 20" storm...

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1 hour ago, uncle w said:

1995-96 and 2010-11 are the top two snowiest winters since I was born...1960-61 is my boyhood winter and that shut off after the first week in Feb like 2011...77-78 lacks a good December...the rest was great...1993-94 is right up there but to many storms ended as a mix or rain and did not have a 20" storm...

1993-94 was very high impact.  All of those ice events and intense cold... I believe I had more snow days in 1994 than any year in my life.

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It's been a long wait, but the GEFSv12 upgrade is set for next week - including 31 (vs 21) members and daily subseasonal output to 35 days. Today's parallel GEFSv12 supports the operational GEFS with cold lingering in Europe to the end of the month - unlike ECMWF's +NAO forecast
 

 

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