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Tennessee Valley 2019 Fall Speculation/Forecasting

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Pretty solid move to the GEFS over the past two runs by the EPS.  Good to see.  Not a frigid pattern, but pretty much seasonal to BN.  If November has a good correlation to the winter base pattern...November needs to have cold and blocking.  

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6-10 and 8-14 are BN per the CPC and GEFS.

That should put 2019 high in the BN November rankings, maybe the coldest for some of us.  

Last year was cold as well for November, but not quite as cold as this year. That led to a cold start to December and a significant snowfall East of 75. 

Right now November 1976 is the only one colder in my area after the last few days of BN. Same with Crossville.

1976 had a BN December with several snowy days with around 4 inches falling in the month. It had one week of AN temps from the 10th to the 17th. 

Nov 1967 was also cold at a similar level to this one. It has a fairly warm December that turned cold on the 22nd. It snowed for 7 days of the last 9 and with around 9 total inches. 

Nov 1995 is in the top 5 coldest. December was -2.8 and it snowed a little over an inch but snow fell on 7 different days. 

December 1969 was frigid. -6 BN. Had 8 snowy days including a huge Christmas snowstorm with over 10 inches for the month. 

December 1955 is the final of the 5 coldest Novembers. It ended -3.5 with snow on 7 different  days with 2.5 inches falling. 

So of the 5 coldest Novembers,  4 of 5 Decembers ended BN temps and 4of them AN snowfall wise and 1 near normal snowfall wise. 

So the colder the November the higher the correlation to cold Decembers. Just based on that we should have a decent shot at a cold December with some snowy periods if this month continues its BN stretch as forecast. 

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Slowly the CFS  is catching  on each day,but it's not right still. Took a snip from the last oceans update 11-15

Last Updated: 11.15.19 Valid: 11.16.19 - 11.26.19
The MJO is now in RMM Phase 8. The ECMWF and GEFS forecast the MJO to weaken during the next week, but the CFS continues to forecast the MJO to propagate to the Indian Ocean with significant amplitude during the next two weeks. As stated in the original discussion Tuesday, it's likely that the CFS is influenced by the positive IOD event projecting on to the RMM Phase 1 structure and its MJO signal is therefore not real.

 

 

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/ghazards/

Madden Julian Oscillation12.png

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Fascinating look at the NAO.  I encourage to find and read all three tweets about the evolution of a -NAO(500 and surface) and its antecedent pattern.  Good stuff.  Here is my favorite.  Look at the patterns(be sure to read the labels and to click each pic...some have more photos than the Twitter thumbnail) and think about what the ensembles have been trying to work out for the end of the month.  Looks very similar to many runs.  

 

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Look at the pattern at hour 72 of the 18z GEFS.  Now, compare it to the pattern above in the first slide.  What appeared to be a problem in modeling is just the first step in the -NAO process.

1836176084_ScreenShot2019-11-16at11_46_20PM.png.67a6aa02a092dcbeb20f49add04aeea1.png

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1 hour ago, Carvers Gap said:

Look at the pattern at hour 72 of the 18z GEFS.  Now, compare it to the pattern above in the first slide.  What appeared to be a problem in modeling is just the first step in the -NAO process.

1836176084_ScreenShot2019-11-16at11_46_20PM.png.67a6aa02a092dcbeb20f49add04aeea1.png

Thanks for sharing, very cool.  

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Still some pretty textbook NAO looks on both the GEFS and EPS.  Ridge rolls through the East quickly and the trough deepens behind it.  The block may actually mute warm MJO phases and also mute what would have been a very warm pattern as our source regions for cold are pretty much on empty - cold is in Asia. Hopefully the block lasts long enough for the MJO to rotate into colder phases.  I think if this happens, colder air finds its way over the pole and into the East.  Interesting LR pattern for sure.  The GFS has some solutions yesterday where it appeared systems were beginning to feel the block and were partially suppressed.

edit:  There are systems in the 6z GFS already being forced south.  

edit:  0z Euro as well.

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Seeing some consternation on other sub-forums about the ridge around d10 that rolls through on the GEFS.  That is definitely a break in continuity.  Given the amount of change in the higher latitudes, not unsurprising.  We have seen this pop up on run in the past on several runs - I was complaining about this look last week as a matter of fact.  And this is my observation....this 500 setup has proceeded strat splits in the past.  Yeah, it is not the stratosphere...but when the WAR hooks into a Greenland block better look out.  All kinds of craziness bout to get unlocked if that holds into place for very long.  That is a crap ton of heat getting unleashed into a block.  Like winding up a top and then letting it loose.  Maybe we should call that a Tasmanian Devil Ridge(TDR), cause what happens next is going to be significant (in terms of cold) and nearly random in terms of where it goes.  I am going to go back and see if I can find a post on that WAR/Greenland Block ridge.

 

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And here is last year's discussion...I will see if I can go find the pic in my files.  When the SER or WAR hooks into a forming Greenland block..the PV (at the tropospheric and stratospheric level) has been split just after or during this event.  So, let's see if this actually happens again.  If it does, it would make three times this pattern of a mega-ridge(WAR/Greenland Block) presented itself and three times an SSW was occurring or about to occur.

 

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I keep seeing some of the long range models hinting at a big system into wk 3,Control last evening had a big Miller B in the NE,sure it will show something different tho like always this afternoon.Euro this afternoon is hinting at a trough that will go -ve tilt somewhere around the S/Plains,wouldn't trust the Euro tho right now towards 8-10 days

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So I went back and looked at the run-up to last year's PV split which occurred in early January I think.  I also looked at the time around the Feb 2018 split.

Here is the 500mb map from December 28, 2018.  This occurred right before the SSW last winter and is referenced in the referenced post above.  It is not in that post.  I have had to clear my memory cache since then.  But here is the actual reanalysis of that date....

1394262753_ScreenShot2019-11-17at3_33_43PM.png.dd0465d38be4cb4fe8d053c9a081f038.png

Here is the 500mb pattern about a week after the SSW which occurred in mid-Feb of 2018....

674919743_ScreenShot2019-11-17at3_43_07PM.png.3b4de32f51fb5cfb6d903f7b34b8bbdf.png

Here is the GEFS at 258....

228363393_ScreenShot2019-11-17at3_33_27PM.png.a18887884134934ecc0d544bd149f7e4.png

Here is the 12z EPS at 258

945200078_ScreenShot2019-11-17at3_47_27PM.png.8f6e90535c418ecad821baeeb5768da5.png

I wanted to show above that sometimes these big ridges that hook into Greenland block at 500mb seem to show up just before or just after a significant disruption of the stratospheric polar vortex higher-up in the atmosphere.  Their duration is relatively short in natured(edit).  I have been saving this in the back of my mind. We in the forum have kicked this around some,  I think Jeff included.  The big ridge along the EC has occurred just before or just after the last two strat splits.  It tends to feed a ton of warm air at lower-mid levels of the atmosphere into the higher latitudes.  Also, not sure I am a huge fan of the SSW.  It doesn't always equate to cold here.  This is just wx talk and not really so much about if it is going to get cold here...though the EPS would indicate as such.  So, let's see if the PV doesn't get bumped around pretty good here in 10-20 days.

(BTW...the 12z EPS is still a textbook -NAO evolution into an eastern trough.  The EPS dumps that trough into the East and flattens it a bit into a nice, stormy pattern typical of a Greenland block.)

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Amy Butler is my go to for SSW events(thanks to Jax for sharing about her expertise a while back).  She had this to say last Thursday.  Pretty interesting to see that big ridge along the EC at 500 sending a bunch of warm air northward in conjunction with potential polar vortex disturbance at the higher levels of the atmosphere.   Probably going to be some tropospheric disturbance at the least.  

 

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1 minute ago, Carvers Gap said:

Amy Butler is my go to for SSW events(thanks to Jax for sharing about her expertise a while back).  She had this to say last Thursday.  Pretty interesting to see that big ridge along the EC at 500 sending a bunch of warm air northward in conjunction with potential polar vortex disturbance at the higher levels of the atmosphere.   Probably going to be some tropospheric disturbance at the least.  

 

There is a workshop starting tomorrow,i'm not sure of the exact time frame for us but Amy Butler will be in it

Workshop: Stratospheric predictability and impact on the troposphere

https://www.ecmwf.int/en/learning/workshops/workshop-stratospheric-predictability-impact-troposphere

 

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1 minute ago, jaxjagman said:

There is a workshop starting tomorrow,i'm not sure of the exact time frame for us but Amy Butler will be in it

Workshop: Stratospheric predictability and impact on the troposphere

https://www.ecmwf.int/en/learning/workshops/workshop-stratospheric-predictability-impact-troposphere

 

Good find.  I hadn't read anything in detail, but I saw that it was mentioned.  If you get a time, let me know.  Hopefully, they will leave the video up.  Even better, maybe she will give us some current SSW snippets.

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Good graph there... would be interesting to see where it is in a couple of weeks.  The 12z Euro and GFS have some pretty strong warming between days 8-10 at 10mb, 30mb, and 50mb.  If the Euro/GFS combo is right, PV is going to take a decent beating - no idea if it results in a PV split.  Also, with the MJO flirting with phases 3-5, that does correlate to a pretty good jostling of the PV at all levels of the atmosphere.  Going to be fairly interesting.  I prefer for the PV to be weak...those SSWs are not always money.   That said, looks like some things are being set into motion which will rough it up pretty good.  

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I was actually just looking at the sunspot years and comparing those years with the strong +IOD event years which,these strong IOD events generally happened in the mid decade unlike this year is quite opposite,you can see my post on the ENSO thread about the IOD,but during this time in 1994 and 1997 there was no SSWE and 2006 which would be the 4th strongest IOD even since 1980 had a SSWE happened in Feb23,this seems odd to me because when you have the low min of the sun cycle you'd have a stronger PV and not weak seemingly

 

 

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31 minutes ago, Carvers Gap said:

18z GEFS has returned to form.  Pretty chilly run.

Euro shows a system coming off the Lee,no artic highs behind it but the storm does go -VE tilt into the plains which would cool us down after,by the Euro we could see the entrance of a 110-120kt jet with the 850's warming above 10C,so you can't rule out severe,but i'm looking at the Euro 9-10 days away,so you should know the drill by now..lol

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33 minutes ago, jaxjagman said:

Euro shows a system coming off the Lee,no artic highs behind it but the storm does go -VE tilt into the plains which would cool us down after,by the Euro we could see the entrance of a 110-120kt jet with the 850's warming above 10C,so you can't rule out severe,but i'm looking at the Euro 9-10 days away,so you should know the drill by now..lol

Jax, you and carver do a great job btw. The mjo charts on the cpc and dacula weather are so misleading because i dont know where it is now lol. I thought it was in phase 8 fixing to enter 1, which i thought were colder phases, especially in December. Is that correct or not? Sorry for the confusion. If those locations arent good, where is the best location for accurate mjo stuff?

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2 hours ago, Mr. Kevin said:

Jax, you and carver do a great job btw. The mjo charts on the cpc and dacula weather are so misleading because i dont know where it is now lol. I thought it was in phase 8 fixing to enter 1, which i thought were colder phases, especially in December. Is that correct or not? Sorry for the confusion. If those locations arent good, where is the best location for accurate mjo stuff?

It's in 8 now and looks like it will go low amplitude into 1 and possibly back into 8. 

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2 hours ago, Mr. Kevin said:

Jax, you and carver do a great job btw. The mjo charts on the cpc and dacula weather are so misleading because i dont know where it is now lol. I thought it was in phase 8 fixing to enter 1, which i thought were colder phases, especially in December. Is that correct or not? Sorry for the confusion. If those locations arent good, where is the best location for accurate mjo stuff?

Use this.When you use the MJO of various models make sure you look at the time stamp,some models don't run no more,But the Euro and GEFS does update regulary each day.

http://www.frontierweather.com/climateandtools.html 

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Pretty chilly next 16 days on the GFS.  Probably 3 AN days and 13 BN days on the 18z run. Always worry we will kick into a long thaw but when I look back over the years the odds are better that the cold is reoccurring than they are that it goes away. Getting burned last year has me wary. But 2014 worked out later in winter. 

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21 minutes ago, John1122 said:

Pretty chilly next 16 days on the GFS.  Probably 3 AN days and 13 BN days on the 18z run. Always worry we will kick into a long thaw but when I look back over the years the odds are better that the cold is reoccurring than they arSs away. Getting burned last year has me wary. But 2014 worked out later in winter. 

Guess the good news it's not winter yet,Euro now shows us warming up into next weekend mid week and as much as 10C "AN" Saturday then a front bumps us back down.Last year we didn't see the teens in Nov but on the 15th of Nov., we had some light snow hi was 37 low was 28

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