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February 2023 Medium/Long Range Pattern Discussion Thread.....Torch or Tundra???


Carvers Gap
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There is likely going to be some warmth during mid-month - and maybe extreme.  So, I am not starting this thread w/ any sugar coating.  That said, models are sniffing out a cold shot to start this month which wasn't seen on some modeling even 24 hours ago.  In life we go one day at a time.  Let us not borrow the troubles of tomorrow until they arrive.  12z Yesterday and 12z today of the GEFS.

Screen_Shot_2023-01-22_at_1.00.24_PM.png
Screen_Shot_2023-01-22_at_1.00.34_PM.png

 

 

 

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My gut instinct...a little bit of both. Raw memory applied...some of the most memorable February's were amplified and variable. 2003/2015*/2021...maybe not so much but certainly 1996/2011 for middle TN. Either way, I think most of us would take a solid two-week stretch at any point between now and March 15 after a lost January. As bad as 2015-16 was, all it took was Jonas to make up the difference...granted the ENSO was radically different. Bottom line: Our windows don't have to be large for us to capitalize. Fingers crossed, we'll get into a battle zone so we can score some threat threads at the very least. 

*Speaking of winter 2014-15, I remember thinking around 1/31/15 that winter was over for our area (actually snow chased up past Mount Vernon that day to scratch the snow withdrawal itch). Then the bottom fell out by mid-February for a couple rounds of snow/ice. Especially for northern middle TN/southern KY, February 2015 was a much bigger hit than February 2021. 

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Great comments, Flash.  @Holston_River_Rambler, I saw your post in Banter about Siberia.  I though, "I wonder if that air mass is going to move?"  Take a look at the 12z GEFS(yes, I know GEFS...), and look at the migration of cold into North America.  For those new to this, watch Canada at the beginning of the run, and look at the end.  Also, watch that bitter cold air flow across the North Pole into the Western Hemisphere.

gfs-ens_T2m_nhem_fh0-384.gif

 

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Here is the 12z GEPS.  That is remarkable similarity to the 12z GEFS in regards to the Siberian cold heading into Canada. When the GFS has a mega run like it did yesterday at 12z(a true outlier), sometimes that is a hint, and it just got ahead of itself...or it just blew a fuse or both.  Model mayhem is likely w/ this amount of cold on the table.   This change is not in the distant future.  The actual discharge of Siberian air into North America has begun.

gem-ens_T2m_nhem_fh0-384.gif

 

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3 minutes ago, Holston_River_Rambler said:

The above was from earlier in the winter. Here is a current graph for the same wave reflection phenomenon: 

so even though the waves aren’t destroying the SPV they could still be meaningfully reflected toward Canada if I’m reading that correctly and cause swings in modeling wrt the cold 

About half that goes over my head.  LOL.  I certainly looks like the SSW is having effects on modeling now.  It has been some time since I have seen that much cold pouring into Canada.  Cool thing is modeling has had this for some time.  What is not being handled well(understandably) is where the cold goes.  It is heading for the snow pack and less friction in the Mountain West...and I would think one or two waves of that make it at least to the Plateau.

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The interesting thing is the MJO for the Euro favors the cold coming west and the GFS does not...yet, the GFS brings the cold quicker than the Euro around Feb1.  Ensembles are probably the way to go here.  The MJO would favor cold being sent westward for sure.  That said, the cold shot is so strong...I am not sure the SER can hold it back forever.  This may be an instance where cold(for a time) overcomes the MJO forecast. 

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I’m thinking we are almost left with needing a wave to ride the cold front of a cutter. Obviously it’s not the only way but I believe the alternative has a very low probability of happening. It’s pretty amazing…. This is a pattern that we do not want and this is our 3rd winter in a row. On the flip side, we can’t get patterns that we can work with to hang around more than 7-10 days.


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The 12z EPS changes at 500mb are stark and cold.  If it was a run unique to that model, I would toss it as an outlier.  I do approach these changes cautiously as Jax mentioned in the Jan thread that Burger was having issues getting data into his site from the GFS...but this is the EPS. 

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Here's a thought. Strat stuff seems to give models problems. I think we can all agree on that. How do models visualize things like the wave reflection Furtado is describing? Is it just a storm driving poleward carrying heat that hits a stout SPV and gets shunted back down (in altitude and latitude) in the flow? What hPa level does that happen at? We normally look at H5 vort maps for storms, surface reflections, or the jet stream and 200 or 300mb to see a storm and we have all those atmospheric levels on all the models we look at so its pretty easy to see a storm forming, breaking, and eventually dissipating. Does it really disappear though? Does the energy flux up to like 100mb, 50 mb, and eventually 10mb and take heat from the mid latitudes with it? 

It just seems to me that there is this nether region of modeling (at least as I usually use them) above the jet levels and I have no clue how or if that gets modeled. We always look at models as 2D projections, but really those higher and lower heights are just that, bowls and hills in the atmosphere creating baroclinic zones. I wish there was some way to tilt the projection and get a 3rd dimension on a planetary scale, something besides a sounding or even one of those cool cross section soundings. 

I think I kind of answered my own question toward the end of that, but I guess what I'm getting at is this. As waves get "reflected" (whatever that actually means) could that cause some blind spots for modeling? 

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24 minutes ago, Carvers Gap said:

Was that the ice storm/overrrunning event...if so, yes.  I agree.

Yes.  We started with freezing rain in Nashville that flipped to heavy sleet.  After over an inch of sleet, we finally transitioned to and added about 4 inches of snow.

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Just from reading the intro to the paper Furtado cited, it seems to me this "wave reflection" activity is something we're still struggling with:

https://journals.ametsoc.org/configurable/content/journals$002fmwre$002f148$002f4$002fmwr-d-19-0339.1.xml?t:ac=journals%24002fmwre%24002f148%24002f4%24002fmwr-d-19-0339.1.xml 

Here is a key paragraph IMO:

"Second, the polar vortex can also act as a reflective surface, preventing the absorption of upward-propagating waves. Troposphere induced waves entering the stratosphere are then reflected downward, thereby influencing tropospheric circulation (Harnik 2009; Shaw et al. 2010; Perlwitz and Harnik 2004; Kodera et al. 2008, 2013). While the occurrence of wave reflection is well documented (Perlwitz and Harnik 2003; Shaw et al. 2010; Nath et al. 2014), its impacts on surface weather have been given less attention. Recently, Kretschmer et al. (2018a) showed that downward reflected waves over Canada favor North Pacific blocking, respectively, a negative phase of the Western Pacific Oscillation (WPO), and are associated with cold spells over Canada and the northeastern United States, consistent with earlier case studies (Kodera et al. 2008, 2013). Nevertheless, the exact role of wave reflection for North American cold spells, as well as the possibilities for subseasonal to seasonal (S2S) forecasting has not yet been comprehensively assessed." 

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2 minutes ago, Holston_River_Rambler said:

Just from reading the intro to the paper Furtado cited, it seems to me this "wave reflection" activity is something we're still struggling with:

https://journals.ametsoc.org/configurable/content/journals$002fmwre$002f148$002f4$002fmwr-d-19-0339.1.xml?t:ac=journals%24002fmwre%24002f148%24002f4%24002fmwr-d-19-0339.1.xml 

So many variables and so much chaos.  No wonder long term forecasting is hard.  When we think we have it figured out, Mother Nature throws us a knuckle-curve.

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1 hour ago, Holston_River_Rambler said:

Just from reading the intro to the paper Furtado cited, it seems to me this "wave reflection" activity is something we're still struggling with:

https://journals.ametsoc.org/configurable/content/journals$002fmwre$002f148$002f4$002fmwr-d-19-0339.1.xml?t:ac=journals%24002fmwre%24002f148%24002f4%24002fmwr-d-19-0339.1.xml 

Here is a key paragraph IMO:

"Second, the polar vortex can also act as a reflective surface, preventing the absorption of upward-propagating waves. Troposphere induced waves entering the stratosphere are then reflected downward, thereby influencing tropospheric circulation (Harnik 2009; Shaw et al. 2010; Perlwitz and Harnik 2004; Kodera et al. 2008, 2013). While the occurrence of wave reflection is well documented (Perlwitz and Harnik 2003; Shaw et al. 2010; Nath et al. 2014), its impacts on surface weather have been given less attention. Recently, Kretschmer et al. (2018a) showed that downward reflected waves over Canada favor North Pacific blocking, respectively, a negative phase of the Western Pacific Oscillation (WPO), and are associated with cold spells over Canada and the northeastern United States, consistent with earlier case studies (Kodera et al. 2008, 2013). Nevertheless, the exact role of wave reflection for North American cold spells, as well as the possibilities for subseasonal to seasonal (S2S) forecasting has not yet been comprehensively assessed." 

Good find.  That last sentence is about right.  I think SSWs are such a crapshoot.  They often send cold to the mid-latitudes.  That is one thing that is common.  Where is the question for me.  I think Boone noted that late season SSWs tend to go into the East.  I have little doubt that strat warming is wrecking havoc on model accuracy d7+.  

As for '89-90, the forum would not have survived that winter.  LOL.  Lots of great winters have warm spells during the early to mid parts of Jan after early starts....and there are winters where winter began early and struggled to return(last two winters are that for MBY).  Jury is still out on whether this winter will join that "quick start...then fade" analog package.  As February hasn't occurred yet, no way to know.   This winter for MBY is nearly an exact replica of the past two.  We didn't get the good stuff that middle and west TN had during the past two winters.  We are used to it, so no big deal here.  Uncertainty makes this process interesting for me....lots of exactly that coming up.

I will add that I am having a blast watching the Bills vs Bengals game - snow.  

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Quick update and then I am out of pocket for the AM.  The 0z Euro control is probably the coldest I have seen it at range.  The 6z GFS just slams middle and west TN with ice and snow.  Yes, it is 10 days out(sign the waiver), but the signal for winter is across the board this AM.  No idea if it verifies as this is at range.  This reminds me a bunch of the cold run-up in December.  Can-kick, can-kick, will it ever get cold, and then it arrived.  Again, the SSW(displaced and jostled...not a true reversal) I think is having a lot of impact in the LR.

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8 minutes ago, matt9697 said:

Getting a real uneasy feeling about an upcoming icing event next week; really really need the SER to relax just a little bit more please, according the the 6GFS run 

IMHO, we are seeing the signal for an overrunning event.  It could be the Ohio River.  It could be the mid-shot from Jackson, MS, to Atlanta, GA(see 0z GFS)...or it could be this forum area.  But a potential cold, Arctic boundary could be interesting w/ an active STJ.  That is about all we know right now.  It could all dump West, but modeling has been constantly pushing cold highs underneath that 500 SER, and you are right....that is the recipe for ice/snow in the upper south.

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2 minutes ago, Carvers Gap said:

IMHO, we are seeing the signal for an overrunning event.  It could be the Ohio River.  It could be the mid-shot from Jackson, MS, to Atlanta, GA(see 0z GFS)...or it could be this forum area.  But a potential cold, Arctic boundary could be interesting w/ an active STJ.  That is about all we know right now.  It could all dump West, but modeling has been constantly pushing cold highs underneath that 500 SER, and you are right....that is the recipe for ice/snow in the upper south.

Well, been stated before in the forum but at least we have something to track this year, many years it is just one rain storm after another.

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The 6z GEFS is coming in quite cold.  The run isn't over yet.  This is similar to the 12z run from Saturday, except this time it has support from both the EPS and GEPS.  Just a guess, but modeling is picking up on a decent cold shot right after Jan31.  It is almost like there is an MJO lag right now where the MJO effects are taking 7-10 days to impact our weather here.  I don't fully understand when it lags or when it doesn't.  Sometimes, the MJO is coupled to the point its effects here are almost lockstep.  Still about 8-10 days out there, but if we are still seeing this on modeling on Weds....then it might have some true merit.   I suspect the cold shot is legit.  Placement of the boundary will depend on the strength of the cold shot, its delivery mechanism, and the strength of the SER.  The ensembles do look like a skating rink IMO.

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