Fall 2020 Discussion

[nrgjeff]

Maybe we can get some severe weather going around Veterans Day. Did somebody say record high temps? And also a West / Plains trough approaching. You'd think by November no odd closed low or TC would get in the way, but you never know in 2020.

Otherwise I do believe warm is our background weather pattern due to La Nina. Expect typical or greater La Nina volatility though. Warm water off the Pac NW Coast invites troughs over the Continental US. Plains trough and SER cage match smack down. Don't forget folding chairs and microphone stands.

[Carvers Gap]

3 hours ago, nrgjeff said:

Maybe we can get some severe weather going around Veterans Day. Did somebody say record high temps? And also a West / Plains trough approaching. You'd think by November no odd closed low or TC would get in the way, but you never know in 2020.

Otherwise I do believe warm is our background weather pattern due to La Nina. Expect typical or greater La Nina volatility though. Warm water off the Pac NW Coast invites troughs over the Continental US. Plains trough and SER cage match smack down. Don't forget folding chairs and microphone stands.

Jeff, do you think that warm water in the NW PAC holds on all winter?  I have read a few posts where some think it may cool off.  I think if we are going to have some cold at some point, we need it there....

[PowellVolz]

Maybe we can get some severe weather going around Veterans Day.

I remember 2002. Almost wiped Mossy Grove off the map.


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[Fred Gossage]

MJO seems to be headed toward a more favorable phase for severe weather threats as we approach mid November.  I also wouldn't be surprised if that acts to reset the pattern some and allow it to be not quite as favorable for tropical storms to come north into the Gulf.  I think it's going to take that next couple of weeks to do that, though.  I can't rule out a threat before then, but I think if a trough ejects out before the second week of November, it will probably have interference from the tropics.  I wouldn't be shocked at a significant severe weather threat after that in the mid and/or latter part of the month.

[jaxjagman]

CFS shows a KW around the IDL today which gets into the GOM and Caribbean into the long range.GFS shows a strong tropical system  and even the EURO shows a area of LP today in the GOM.Could get some tropical mischief upcoming.Where it goes and if anything does develop would seem to be a trough going through East Asia  the next couple days

[nrgjeff]

Veterans Day 2002: Now that's what I call Interesting! Though I can't find archived upper air charts.

I infer from the orientation of the front that the trough was positively tilted, and still produced a High Risk. 

Do we laugh at the Euro and GFS or take that a little more seriously? I'll opine for real later this week.

[Fred Gossage]

51 minutes ago, nrgjeff said:

Veterans Day 2002: Now that's what I call Interesting! Though I can't find archived upper air charts.

I infer from the orientation of the front that the trough was positively tilted, and still produced a High Risk. 

Do we laugh at the Euro and GFS or take that a little more seriously? I'll opine for real later this week.

Interestingly, quite a few of the strong/violent tornado events in the Tennessee Valley and the heart of Dixie Alley have happened with positive tilt troughs.  4/8/1998, 5/18/1995, 4/7/06 are three that stand out in memory, but there have been many more.  Even though the trough with 4/3/74 started out negative tilt that day, it evolved into a positive tilt trough before any of the F4-F5 damage happened that evening in Alabama.  We can never know for sure because of the lack of data, but based on the NCDC reanalysis that goes back as far, the 3/21/1932 outbreak was a blatant positive tilt trough, as was the system that produced the Tupelo, MS F5 in 1936, IF the reanalysis data is close to right.  Amplitude of the trough seems to be much more important than tilt, despite what we were trained to believe over the years... low amplitude troughs, regardless of tilt, are more dangerous.  History doesn't lie though.  I did a big article on this in 2010 before this forum was AmericanWx, looking at violent tornado outbreaks in Alabama based on trough tilt.  I looked at events from the Enigma 1884 event forward to 2010, assuming that the NCDC reanalysis data was not necessarily spot on, but was a good first guess.  The work showed that just over half of the F4-F5 events in Alabama during that period were from positive tilt troughs.

[Carvers Gap]

Really warm week next week shaping up.  Not many "low hanging fruit" record highs though.  Still, looks like Nov 11 with a high of 76 is our best shot at TRI.  But y'all, those are going to be about as warm as one can get for November....so other record highs cannot be ruled out.  Will take some time to get rid of that warmth once the pattern changes.  That type of heat just doesn't disappear.   Atmosphere is going to be supercharged with plenty of energy.  

Past that, not many hints that the pattern does anything but stay really warm in the East.  We all know in fall that can change swiftly, however.  I would guess this pattern might last into the early part of December.  As I noted earlier, maybe the silver lining is that we "might" be setting up for a switch to cooler around mid-Dec.  That said, if you like cool wx for fall...this pattern we are about to enter pretty much sucks.

[Carvers Gap]

I think I am going to have to update my winter forecast from over the summer to much AN for December, but going to wait a week or so before doing that.  Weeklies have 5-10 days which are seasonal in Dec, and pretty much AN to much AN for most of the run - goes out to the third week of December now.  Very little relaxation from the upcoming, very warm pattern...which sometimes that much continuity can be a red flag.  That said, I am seeing very little in the way of teleconnections which would support cold in the East - that big ridge in the Aleutians is pretty much locked in.  Impressive warmth upcoming for November and will feel much like early summer.   Let's hope it is wrong.  Looks very much like a strong La Nina pattern.

[Carvers Gap]

If there is one fly in the ointment of the really warm look, it is the tropics.  It is not out of the realm of possibility for a storm to shake-up the pattern.  I think Jeff mentioned this as a possibility.  What we would need is for one of those storms to go hybrid, and drive the trough deep into the East and force the PNA to pop.  That might back-up the pattern enough to force the ridge out of the Aleutians(that Aleutians ridge is there for nearly the entire 46 day run of the Weeklies).

[jaxjagman]

10 hours ago, nrgjeff said:

Veterans Day 2002: Now that's what I call Interesting! Though I can't find archived upper air charts.

I infer from the orientation of the front that the trough was positively tilted, and still produced a High Risk. 

Do we laugh at the Euro and GFS or take that a little more seriously? I'll opine for real later this week.

LOL... no doubt about that

[Holston_River_Rambler]

Not much of substance to add, but to note that the pattern seems to be shaping up to be sorta kinda the opposite of last year. We flipped around Halloween after a warm Oct. and then once we hit mid to late Dec, we went back to warm and didn't look back. Certainly could stay ridge-east/ trough-west throughout, but I also favor Carver's idea of an Ides of December change, even though how long it lasts is up for grabs.

I want to revisit the post I used to start the wold speculation thread, and may try to do that later this PM when I have s little more time. 

 

Also, I live in Mossy Grove now, so any 2002 redos are unwelcome, lol. 

[Carvers Gap]

The current pattern of a ridge in the East is about as "locked-in" as one can get on modeling.  Barely a hint of it breaking down during the next 4-6 weeks.  Summer is back.

[PowellVolz]

The current pattern of a ridge in the East is about as "locked-in" as one can get on modeling.  Barely a hint of it breaking down during the next 4-6 weeks.  Summer is back.

On the bright side, I’d rather take a chance with this pattern with the possibility of a flip during prime climatology. Seems like the last few years we went BN when climo was out of range.


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[Carvers Gap]

59 minutes ago, PowellVolz said:

On the bright side, I’d rather take a chance with this pattern with the possibility of a flip during prime climatology. Seems like the last few years we went BN when climo was out of range.


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Definitely.  Said as much a few weeks back.  My main concern is the pattern is showing next to no sign of flipping.  If anything, the high over the Aleutians is getting stronger...even on seasonal models.  We will have a chance or two, always do.  I am just not a fan of near record warm temps in Nov.  The ridges (in the East) which are being depicted are about as strong as I can remember.  One other concern is that the type of warmth being shown likely has staying power.  It might take 1-2 weeks of a new pattern just to scour this out.  When these attempted cold fronts come through from the NW, the warmth rebounds almot like it is summer.  Just crazy to see cold fronts gain headway into the East even during Nov.  Hoping the 4-6 week pattern rule wins the day.  Seems like we have been in this pattern for a majority of the past 3 years....meaning cold dumps in the front range of the northern Rockies and can’t push SE once we get deep into fall and into winter.  I do suspect that the atmosphere will balance things out with a western ridge at some point.  If we are going to have a La Niña, needs to be strong so as to bring the PAC Basin backing balance - been far to warm relative to norms. 

[Carvers Gap]

12z GFS after d10 is a significant break in continuity. Not worth much more discussion on my part.  More likely than not that is a hiccup.  Not even sure that is worth a mention in the main forecast thread, but sometimes the GFS can catch a pattern shift a bit early and often jumps the gun even.  But the 500 pattern is a lot different after d10 compared to other runs by the same model.

[Carvers Gap]

Temps next week are forecast at TRI to be 10-20 degrees AN.  Our normal highs begin in the mid 60s and lower into the upper 50s as the week goes on.  Highs are supposed to be in the mid-upper 70s.  Those are some pretty amazing highs considering that days are shorter, and the sun's angle is lower.  About a month ago, I thought we had avoided endless summer....wrong.  

[Holston_River_Rambler]

Euro looked a little more zonal late in its run too. Anything for more fire place weather! 

[Holston_River_Rambler]

Overnight the Euro went straight up trough east, ridge west day 10. Probably not a good sign though, since it is at day 10. Given the usual progression, will be a Rockies cut off in about 5 - 6 days on modeling. 

[Carvers Gap]

I like where the CFSv2 is the morning(it changes often...beware for those new to following wx modeling).  Warm rest of November which now looks like a really good call.  December begins to dial back the heat, and January w maybe a decent window of opportunity as Jeff alluded to with his excellent graphic on Euro clusters for Jan(really appreciate that share).  So, just reading between the lines, looks like we revert to normal(maybe BN) temps by mid-December.  I have no idea how long that holds, but would guess to week 2ish of Jan and maybe even week 3.  I could easily be wrong, but we may have a shot at cold weather over the holidays.  OTH, there is a very really scenario where we just stay ridiculously warm all winter.  Why?  The MJO regions in the equatorial western Pacific have not cooled as much with the La Nina.  If that holds, that is a perfect storm for a really warm winter when combined with moderate to strong La Nina.

[Carvers Gap]

Weeks 3-6....Just took a look at the Euro Weeklies.  BN heights in AK and a HB block.   Not sure how those two co-exist,  but I think I remember that happening just last winter.  End result would be storms in early to mid Dec being forced below our latitude and then they come up the EC.  Temp profile would be generally lousy, but not a terrible storm track if we could steal some cold at the right time.  GFS extended(new product out to 5 weeks) control and Euro Weeklies control show a similar set-up.  I use the control just to get an idea of what pattern might be getting washed-out in the ensemble.  So long way off, but the first couple of weeks of December look to have a series of cutters and coastals.    That does make some sense given the block shown over the Hudson Bay...cold source is lacking however.

[nrgjeff]

Canada has above normal precip. If it's snow then it's a decent North American signal. However the Asian side sux blowtorch just like here. 

[Mr. Kevin]

Carver, if we can somehow get a 2-3 week window for a cold pattern, that will feel like we hit the lottery lol. 

[Carvers Gap]

44 minutes ago, Mr. Kevin said:

Carver, if we can somehow get a 2-3 week window for a cold pattern, that will feel like we hit the lottery lol. 

I agree, with the ENSO state considered.  I think we possibly get a storm window in early-mid Dec.  We had a similar pattern last winter with no cold....might be a similar result if the models are even halfway correct.  Moderate to strong La Nina's are generally very hostile for snow IMBY...further west in the forum area, they can score with that ENSO pattern.

[Mr. Kevin]

47 minutes ago, Carvers Gap said:

I agree, with the ENSO state considered.  I think we possibly get a storm window in early-mid Dec.  We had a similar pattern last winter with no cold....might be a similar result if the models are even halfway correct.  Moderate to strong La Nina's are generally very hostile for snow IMBY...further west in the forum area, they can score with that ENSO pattern.

Last year was a elniño, I guess, even though the atmosphere had not coupled with the niño. It had the same west pacific warm pool as currently so it definitely makes it interesting imo.

[Carvers Gap]

9 hours ago, Mr. Kevin said:

Last year was a elniño, I guess, even though the atmosphere had not coupled with the niño. It had the same west pacific warm pool as currently so it definitely makes it interesting imo.

Yeah, I think as long as the equatorial western Pacific is warm....that is a problem here.  I think the overall Pac basin is warmer than normal and is "washing out" the usual ENSO analog stuff(Typhoon Tip has a lot of info on this) due to the gradient being weaker around each ENSO event.  That western Pac area is sending the MJO into 4-5 during winter at high amplitude multiple times.   But maybe a point could be made that the normal analogs don't actually work right now with SSTs AN in the Pac Basin.  I have certainly considered that.  I think there is a school of thought in our forum(which I agree with more and more with each passing season) that each year is its own analog.  I do think we see 1-2 really severe cold shots.  Nina's tend to have those (unless the Nina is really strong).  I also think we deal with a very persistent Southeast Ridge.  We have already seen some really severe cold in the West this fall.  What we need is for the jet to buckle in the East and have one of those shots head this way.  But really, we pretty much know that seasonal forecasting can be a crap shoot....so, I truly don't rule anything out.

[Holston_River_Rambler]

On 11/7/2020 at 6:52 AM, Holston_River_Rambler said:

Overnight the Euro went straight up trough east, ridge west day 10. Probably not a good sign though, since it is at day 10. Given the usual progression, will be a Rockies cut off in about 5 - 6 days on modeling. 

Hey, at least for once the Euro has underestimated the strength of cold push with a trough. Yea its a pretty quick swipe, but some decent fire weather looks likely early next week: First gif is a trend over the past 5 runs of the Euro's 850 mb temp anomaly and the second is a forecast of 2m temps.Monday morning through Wednesday PM. 

Sometimes, I guess, you have to reverse psychologizeify the models. 

[nrgjeff]

Numerical models are trying to go colder after Thanksgiving. This is after the seasonable front next week. I'm talking 16-30 day hints with the MJO.

MJO is going to be fickle for a few days though. Tropical Cyclones are active and or forecast in the Western Pacific and Indian Oceans. TCs typically create volatility in MJO forecasts. 

[Carvers Gap]

4 hours ago, nrgjeff said:

Numerical models are trying to go colder after Thanksgiving. This is after the seasonable front next week. I'm talking 16-30 day hints with the MJO.

MJO is going to be fickle for a few days though. Tropical Cyclones are active and or forecast in the Western Pacific and Indian Oceans. TCs typically create volatility in MJO forecasts. 

Euro Weeklies have your back on pretty much all of that.  Not a terrible look after Thanksgiving.  Thanks for keeping us updated.  How do the clusters look on the Euro Weeklies?

[Carvers Gap]

Seems to be a continued attempt at reshuffling the pattern later this month - just to echo what Jeff and others have stated.