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Tennessee Valley 2019 Fall Speculation/Forecasting

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21 minutes ago, Mr. Kevin said:

Hi carver. ISOTHERM'S forcast scares me too lol. I dont want him to be right if we have any chance this winter. Why do you think the epo/wpo are going positive? Is it the mjo moving to unfavorable phases? I am still clueless with that.

MJO is tricky right now because the phases that correspond to cold during fall are not the same as the ones that do so during winter.  Right now, we are just about two and a half weeks from met winter beginning.   So, it kind of has one foot in and one foot out in terms of...Do we use the fall phase correlations or the winter?  

Seems to me that outside of the GEFS, the western ridge is still a consistent ridge on LR modeling.  Probably has been more a PNA ridge thane EPO so far IMHO.  Either will work, though they do change precip amounts here.  Also, don't want those ridges so tall that a trough tucks into the NW under it.  

A good quote from a poster a few years back...we know we are in trouble if we are having to watch MJO phases.  Now, the MJO carries a ton of weight in my book.  What the poster was basically saying is that a good pattern will often override the MJO influence.  Right now the pattern is pretty good...and I haven't looked an MJO phase in about a week.  LOL.  

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1 minute ago, Carvers Gap said:

MJO is tricky right now because the phases that correspond to cold during fall are not the same as the ones that do so during winter.  Right now, we are just about two and a half weeks from met winter beginning.   So, it kind of has one foot in and one foot out in terms of...Do we use the fall phase correlations or the winter?  

Seems to me that outside of the GEFS, the western ridge is still a consistent ridge on modeling.  Probably has been more a PNA ridge thane EPO so far IMHO.  Either will work, though they do change precip amounts here.  Also, don't want those ridges so tall that a trough tucks into the NW under it.  

A good quote from a poster a few years back...we know we are in trouble if we are having to watch MJO phases.  Now, the MJO carries a ton of weight in my book.  What the poster was basically saying is that a good pattern will often override the MJO influence.  

It is tricky i guess. I just don't understand why people think we are in a modoki elniño. If we are, we should have a pretty cold winter, but not everytime. Its all confusing to me.

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7 minutes ago, Mr. Kevin said:

It is tricky i guess. I just don't understand why people think we are in a modoki elniño. If we are, we should have a pretty cold winter, but not everytime. Its all confusing to me.

It has a chance to be sort of a Modoki...the problem is the eastern equatorial Pacific has had some Nina-ish SSTs recently or at least have trended that way.  I haven't looked this week.  I do think that led to our dry and hot September and early October.  Also, Typhoon Tip in the NE subform I think has talked about that the Pacific is anomalously warm over most of the basin...that is actually causing the temperature gradient to be weak.  That means we really want El Nino patterns to have a sharp gradient to cool water which surround them.  Right now, there is just little gradient.  Due to this, the standard analog packages are not working very well.  

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Just glancing through the most recent ensembles....the 6z GEFS has backed-off the mega ridge and has joined the -NAO club that doesn't connect to an eastern ridge.  A -NAO is not a slam dunk for cold BTW.  The reason a lot of us like it is because the storm track gets suppressed and confluence is more favorable for our forum area.  Not sure it will supply enough cold for us to benefit from the potential block...but an interesting look.  IMHO, still a lot of uncertainty for the last week of November.  Some good signs...but not ready to pull the trigger yet on stating that I believe the elusive -NAO is going to pay a visit later this month and into early December.   Looks like the coldest air is setting up in Asia.   Need a mechanism to get it to this side of the planet.

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Agree with those who do not worry too much about the weekly forecasts. They've been awful past week 3 since the dinosaurs were around. Both have badly missed cold snaps. Rest of November probably will get back closer to normal for Thanksgiving. Works for me and Chattanooga's Holiday on the Landing.

December could start out colder than shown. WPO wants to go positive which is a warm signal, but perhaps more consequential for the Plains. Meanwhile the PNA wants to go positive, a cool signal here. Models are clueless and maybe too warm. It's a rare event when I lean colder than NWP, but this might be one of those times.

I'm still mild December, but not as warm as those weeklies.

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So, any thoughts on late Thursday night y'all? 

Euro been edging up awfully close over the past few runs:

giphy.gif

850 temps look marginal, but hey, what do we have to lose:

giphy.gif

And that's not an awful track for two dancing shortwaves:

giphy.gif

Still 48 hours out and room for a slight NW trend? 

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Takeaways from modeling this afternoon...-NAO is found on the three major global ensembles beginning mid-week next week.  The JMA has moved to a cooler January and February...but it was wrong all winter last year.  So buyer beware.  If that -NAO sets up shop, it becomes the driver IMHO.  Lots of good doors in terms of winter could open, especially with winter storms.  Some modeling is depicting some weak interaction between the PNA and the potential Greenland block.  Still need to be wary.  The solutions yesterday, though not desirable, are a possibility.  However, I like seeing the Greenland block showing up consistently across the board.  While modeling is tremendously sketchy outside of three weeks...many operational models began hinting at the big highs that produced todays snows...weeks ago.  So, there are some good signs out there in model land that might hint at an enduring block.  HM has been talking about the Aleutian low really making its presence felt - if I am speaking HM language correctly.  He is now alluding to December - early Feb as being cold.  Shocker - that is mid-winter...but that is not as easy of a prediction as one might think given last year's outcome.  Lastly, the MA forum was talking about how the winter Nino temp timeline might be moved up a bit.  I guess that means that the moderation of temps over the next couple of weeks would be the December thaw often seen during Ninos, and that January would be cold versus actually trending colder as the month progresses.  Hopefully, I gave credit where credit is due.  Man, it feels like the middle of winter out there today.  One of my kids said, "It's going to be 65 degrees colder this afternoon than it was to begin October."  I cannot imagine where they would hear such comparisons.  Now, if they start discussing 1954...  Seriously though, these fall athletes have endured record high temps and today...snow.  It has been a really interesting fall in hindsight.  

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EPS just went colder hour 360. Normally that's banter, but check out the buffet line of teleconnections Carvers mentions just above. Issue has been a raging +WPO (warm) vs everything else cold. If a true +PNA develops (with Hawaii ridge) that could be what breaks toward colder here in the Southeast. -NAO too of course; but, some +PNA could fight off the WPO.

Billiard ball meteorology, lol!

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3 hours ago, Carvers Gap said:

Jeff hit the high points of the 12z EPS run.  Really nice run in terms of potential for cold.  

Even a hint at maybe something to watch your and John's way

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On 10/14/2019 at 7:41 PM, raindancewx said:

My take on the very cold NW/very hot SE this October is that the PDO is going negative. Look at where the biggest anomalies v. the correlations are (granted, they are for winter, but with the NAO negative its a pseudo winter pattern now). Blending Nino 1.2 in October (currently under 20.0C on the weeklies) with the PDO in Mar-Aug (+0.83) to match 2019, you have to pick something like 1988-89 and 1996-97. I've hindcasted this method, it's remarkably strong as a predictor once Nino 1.2 is known in October. 

Analog PDO M-A Oct 1.2 PDO N-A
1988 0.86 19.81 -0.60
1996 1.06 20.31 0.38
Blend 0.96 20.06 -0.11
2019E 0.83 20.00

???

This was the blend I used to estimate the PDO last year.

Year Oct 1.2 PDO M-A PDO N-A
1963 20.96 -0.75 -0.88
2002 21.39 -0.24 1.69
2004 21.16 0.57 0.47
2004 21.16 0.57 0.47
Mean 21.17 0.03 0.44
2018 21.13 0.07 0.51


Image

Image

I had the right idea here - the PDO came in at the most negative level observed in six years in October: -0.45 on the JISAO / Nate Mantua method. Some bounce back maybe in November, but I don't think it is too too dramatic. Much warmer anomalies away from the coast then on it - that's the signal if the waters east of Japan are warm too.

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LR modeling working on its best version of the flip flop last night.  Will be interesting to see how quickly the -NAO can be knocked down.  Traditionally, once in place, it is a fairly stubborn feature.  That said, both the 6z GEFS and 0z EPS find a way to build a SER in the d10-15 range and place a trough out West.  Not a torch by any means...but let's see if the trend continues at 12z.

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The pattern reversal that occurred during the second week of October is still strongly in place.  Yesterday, it was -19F BN at TRI and is a whopping -7.4F for the month through November 13th.  The good thing, as John as noted often, is that there is a decent correlation between November wx patterns and winter wx patterns.  We have yet to have a single day above normal at TRI for the month of November.   We have had five double digit departure days BN.  On November 12, the airport reported one of the of earlier 1" or more snowfalls on record(as John noted, there were some earlier than this week).   Going to be interesting for the end of November as the GEFS and EPS definitely moved to end the current pattern.  That is not surprising as the current pattern would have run about six weeks by that time.  Nino climatology points towards warmer Decembers...so, we are basically trying to find a December that is one of the roughly 33% that are cold with this setup.  This is the departure map for the month of November so far.

148284205_ScreenShot2019-11-14at7_50_41AM.png.29e86e19df8cc7ec0e3d12fa7a9d1a60.png

This is the map for the last ten days...

329320341_ScreenShot2019-11-14at7_49_03AM.png.d80a8670d933761d5ed4dc27ab8b543a.png

 

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12z GEFS is not warm...really at any point.  As Bob Chill noted in the MA...really want to see this get into December.  

Great question, DB.  Many of the wx models that we use were likely built post 1980.  What would a truly blue northern winter look like on modeling?  Probably a mess before and during.  One area where the AI aspect of modeling has issues is with recognizing pattern changes.  People catch those changes in modeling because they will see glitches in the LR modeling.  It is what I actually look for.  Hiccups can mean nothing or they can mean everything.  Right now, the d10-15 ensemble runs are bouncing around in terms of putting the cold into the southwest or east or both.  I suspect the high latitude blocking is wrecking havoc on consistency much like a big, cold high coming out of Canada would.   Jeff said it earlier...not going to be an easy few months of professional or hobby forecasting.

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   My bad on the gefs. Actually saw on ma forum that it was mild too. May of been an earlier run they were referencing although last I had saw the eps was mild, gefs cold. 

  I'd bet models would be going with the warm-up back the in lr as well, only to of reverted at closer range. Also, makes u wonder how the MJO acted then.?. We know HL blocking was prevalent most of the time. 

I, like you Carvers, feel HLB is and will play havoc. Enough of it and even the MJO warm phases can be rather cool. 

Food for thought.

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The GEFS at 12z certainly isn't warmer than average toward the end of its run in late November around Thanksgiving.  No clue if it's onto something (or just ON something), but if it is............... it has a lot of puzzle pieces in good places. 

From the consistent Aleutian low presence and the +PNA with split flow underneath, to hints of Greenland blocking and confluence in the east it looks pretty good to me. 

If it wasn't a 300+ hour projection and was mid to late December and not November I"d be pretty stoked to see the broad WSW flow indicated.  Wouldn't take much of a shortwave to provide overrunning precip from that look....... would just be a matter of finding "cold enough" for something other than rain.  Kind of hard to find "cold enough" in November, but we did manage some snow already, so not impossible.

I put our chances at tracking before month end at 5%.  That's WAY higher than what I had it at just a couple of days ago..... lol

gfs-ens_z500a_hr312_valid11271019.png

gfs-ens_z500a_hr384_valid11302019.png

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Average temps for the month to date. Southeastern Valley areas (Knox to Chatt) aren't as cold as the rest of the area as far as their historical ranking but 11 of the years in their rankings are from before all the other places had weather stations besides Nashville and Memphis (pre-1920, mostly 1800s). Some of these don't have yesterday factored in yet as well.

MBY 39.5  4th coldest Nov

Crossville 39.5 5th coldest Nov

Nashville 43.6 5th coldest Nov

Murfreesboro 42.6 4th coldest Nov.

Tri 42.6 8th coldest Nov.

Chattanooga 47.6 18th coldest

Knox 44.6 17th coldest.

Morristown 44.1 4th coldest (only 21 years of records)

Oak Ridge 44.9 2nd coldest (21 years)

Tazewell 40.5 5th coldest

Oneida 39.6 2nd coldest.

Cookeville 44.6 17th coldest

Clarksville 39.9 2nd coldest on record.

Franklin 43 6th coldest.

Mem 45.1 2nd coldest

Tupelo 45.9 3rd coldest

Jackson, TN 41.9 coldest on record.

Jonesboro, AR 43.2 coldest on record.

Jackson Ky, 41.3 coldest on record.

London, Ky 40.9 3rd coldest

Abington, Va 40.2 5th coldest.

 

 

 

 

 

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1 hour ago, Daniel Boone said:

   My bad on the gefs. Actually saw on ma forum that it was mild too. May of been an earlier run they were referencing although last I had saw the eps was mild, gefs cold. 

  I'd bet models would be going with the warm-up back the in lr as well, only to of reverted at closer range. Also, makes u wonder how the MJO acted then.?. We know HL blocking was prevalent most of the time. 

I, like you Carvers, feel HLB is and will play havoc. Enough of it and even the MJO warm phases can be rather cool. 

Food for thought.

Sorry...wasn't trying to correct you.  It wasn't a response to yours, because I hadn't even read your previous post.  I think your comments actually fit really well based on where the GEFS was previously. I was just trying to be humorous.  My apologies that it read that way...it was just coincidence that my post seemed to correct yours.   I often say,  "Well, that was not a warm run!"  Pretty much in that context.  Just hyperbole. 

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12z EPS buries the trough in the southwest.  Might be real.  Might not.  That has been a trend on more than one model.  Suffice it to say, the EPS has flipped in its d10-15.  It may flip back, but that is a flip to a ridge in the East and a trough in the southwest.  It backed up the overnight run, and dug in even more.  Is it up to its old tricks?  Not sure, but the GEFS has a similar look, just cooler in the SE.  Not good trends, but still plenty of time to switch round.

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Actually after reading through the MA forum...the EPS solution might be in doubt at this point.  It has been pretty bad during the d10-15 range.  The GEFS has had a bit of a hot hand.  Need to watch the block over Greenland.  If it develops...we might be in good shape.  As Boone mentioned, the MJO might be causing some flip-flopping as well due to modeling trying to figure out how to handle the warm phases of the MJO while at the same time having to navigate early high-latitude blocking.  

Lastly, keep an eye on any weird, super-anomalous ridges over NA - especially the EC.  They have been precursors to strat splits.  I don't want one of those as they seem to have bad aim with cold air!  LOL.  

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If there isn’t a chance for snow during the holidays I’d rather it be cool than cold. It’s nice being able to go places without looking like.....giphy.gif


.

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Have to wait and see on the MJO, IMHO.The RMM'S are showing the progression again will slow down , thanks to the +IOD so seemingly the MJO is going to creep though Africa and then the Westen IO.The RMM's show today the MJO is going to get back into the Western IO then go back into COD.IF, it goes into the COD and stays more or less out of the Maritime,these are cold phases into Dec.But we'll have to wait and see right now,but i don't believe it's as progressive as the CFS is showing

CPC - Climate Weather Linkage  Madden - Julian Oscillation.png

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1 hour ago, jaxjagman said:

Have to wait and see on the MJO, IMHO.The RMM'S are showing the progression again will slow down , thanks to the +IOD so seemingly the MJO is going to creep though Africa and then the Westen IO.The RMM's show today the MJO is going to get back into the Western IO then go back into COD.IF, it goes into the COD and stays more or less out of the Maritime,these are cold phases into Dec.But we'll have to wait and see right now,but i don't believe it's as progressive as the CFS is showing

CPC - Climate Weather Linkage  Madden - Julian Oscillation.png

Hi jax. Do we want the mjo to stay in phases 8-2 as long as possible for this time of year or does it matter only for later on? Im not sure which one we want. 

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24 minutes ago, Mr. Kevin said:

Hi jax. Do we want the mjo to stay in phases 8-2 as long as possible for this time of year or does it matter only for later on? Im not sure which one we want. 

In Dec phases 3-6 are warm phases.Right now other than weak KW passing through  around the East Pac end of the month the MJO towards the end of the month is getting into the Westen IO but after this the signs weaken,more  likely into the COD,have to wait and see

Tropical Monitoring    North Carolina Institute for Climate Studies12.png

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The 0z EPS is much more in line with the GEFS now in the LR.  The run-to-run change corrected much more to a trough in the East for d10-15.   That was not a warm run!  Really not much more to add...we will see if that holds.  Models can and do flip in the LR...but the door is cracked for a cold "open" to December, especially if one believes the 6z GEFS.

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