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Fall 2021 Thread (September, October, November)


Carvers Gap
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46 minutes ago, Carvers Gap said:

Man, that is a monster block over Greenland showing up on both the 18z GEFS and 12z EPS for the end of November - monster.  Euro Weeklies have it as well.  Weeklies are back to a cold look until late December when winter shifts back out West.  Huge grains of salt, folks.  I do think the blocking signal has merit.  The Euro picked up on this last week.  It has been really windy during the past week.  I usually notice this during the fall when their are nearly opposite air masses near each other - Captain Obvious I know.  That said, this means that we are not likely going to be in a zonal patter for long periods of time.  If we want cold, we don't want universally meh air masses UMAM.  My term.

The issue is the trough in GOA. I guess we should expect it in a -pdo. Hard to get real cold with that. The Greenland block is nice, but definitely too early in season for winter storms of any significance outside the higher elevations. End of eps had a ridge over Alaska but its 15 days out

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9 hours ago, Mr. Kevin said:

The issue is the trough in GOA. I guess we should expect it in a -pdo. Hard to get real cold with that. The Greenland block is nice, but definitely too early in season for winter storms of any significance outside the higher elevations. End of eps had a ridge over Alaska but its 15 days out

Oddly, in NE TN at lower elevations we have had multiple early season snows during the past decade.  I actually consider early season snows bad for winter.  Seems like what is required for early season snows is a very active, late hurricane season and early season cold.  That combo has a tendency to cause problems with the winter pattern IMHO.  So, I am perfectly happen with no early season snows.

Modeling has had conflicting teleconnections for weeks.  I think that is partly due to it being shoulder season.  Things are in transition, and signals are often in conflict with each other.  As noted earlier in the thread, modeling for a couple of years has had a bad bias between d10-16 of portraying cold shots into the EC, only to have them verify more westward.  

I do think we are on track for an early start to winter.  My biggest question is once the inevitable thaw hits during late December, does it come back?  Some Nina years this happens, and for some it leaves and is gone.  Time will tell.

Again, HUGE grains of salt as mentioned earlier...

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4 hours ago, Carvers Gap said:

Oddly, in NE TN at lower elevations we have had multiple early season snows during the past decade.  I actually consider early season snows bad for winter.  Seems like what is required for early season snows is a very active, late hurricane season and early season cold.  That combo has a tendency to cause problems with the winter pattern IMHO.  So, I am perfectly happen with no early season snows.

Modeling has had conflicting teleconnections for weeks.  I think that is partly due to it being shoulder season.  Things are in transition, and signals are often in conflict with each other.  As noted earlier in the thread, modeling for a couple of years has had a bad bias between d10-16 of portraying cold shots into the EC, only to have them verify more westward.  

I do think we are on track for an early start to winter.  My biggest question is once the inevitable thaw hits during late December, does it come back?  Some Nina years this happens, and for some it leaves and is gone.  Time will tell.

Again, HUGE grains of salt as mentioned earlier...

Agree, but I reserve this designation for October to early November snows, not late November and early December.  Glad to be looking and trying to find winter again.  Hope everyone has been doing well.

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This -NAO shown on the EPS(for the past several days) could be a tough feature to move if it actually forms at that intensity.  Something to watch.  Models may be playing a bit of catch-up in the LR.  Greenland blocks are notoriously stubborn features and models are often erroneous in breaking them down too quickly.  

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6 hours ago, Carvers Gap said:

This -NAO shown on the EPS(for the past several days) could be a tough feature to move if it actually forms at that intensity.  Something to watch.  Models may be playing a bit of catch-up in the LR.  Greenland blocks are notoriously stubborn features and models are often erroneous in breaking them down too quickly.  

I feel like when it breaks down, we are screwed lol. Pacific is in bad shape. People mention November 2010. I think the Pacific was in better shape than currently. Imo, if we donr get any winter storms in December, that may be it especially with everyone going front loaded winter 

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7 hours ago, Mr. Kevin said:

I feel like when it breaks down, we are screwed lol. Pacific is in bad shape. People mention November 2010. I think the Pacific was in better shape than currently. Imo, if we donr get any winter storms in December, that may be it especially with everyone going front loaded winter 

Generally, in the winter………. We are screwed. lol

At our latitude we typically look for the 2-3 day period in time where it all comes together just right.  Then when snow is probable, we over analyze each model run, looking for the level of the atmosphere which will screw us by being +1 and throwing ZR while those just north of us see most of the snow.   Such is life in the south.

I say all that to say this.  There’s always something that can screw us, but even bad winters will usually find a way to throw a bone or two.  Just have to get lucky when it does.

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7 hours ago, Mr. Kevin said:

I feel like when it breaks down, we are screwed lol. Pacific is in bad shape. People mention November 2010. I think the Pacific was in better shape than currently. Imo, if we donr get any winter storms in December, that may be it especially with everyone going front loaded winter 

1989 is the benchmark of winter leaving in December and never coming back.  Hopefully, we don't relive that.  That said, it will make those afternoon jogs much more tolerable.  Welcome to La Nina.  As tnweathernut notes, at this latitude we are just looking for windows when it can snow.  Of note, the Pacific will be in much better shape after the La Nina, but that won't help us this season.  Right now, it is the Indian Ocean which is actually wrecking havoc as the MJO gets stuck in warm phases due to the energy it is producing.  Also, we need a sharp gradient between pools of warm/cold water in the Pac which has been lacking for the past several years - that is not my concept but someone from another forums.  Of note, the QBO is strongly negative.  My initial forecast in June was for a front loaded winter in December.  Did I get lucky?  Time will tell.  My seasonal forecasts are based on recent temp trends and almost completely on the ENSO state.  That said, I didn't factor the QBO during June as it suddenly and unexpectedly flipped negative during early fall.  Second year La Ninas are tricky business.  As John notes, they are often weaker than year one.  Weak La Ninas have a tendency to produce a period of severe cold in somewhere in our forum region.  And sometimes, second year La Ninas do bring winter back for a second round - assuming there is a round one.  The great and worst thing about winter...there are nearly always twists which nobody saw coming.  If I had to pick one ENSO state which can deliver prolonged cold/snow, it is a weak La Nina.  That doesn't mean it always delivers, but that SST state can make for wild winters swings.  

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12 minutes ago, tnweathernut said:

Generally, in the winter………. We are screwed. lol

 

giphy.gif?cid=ecf05e47y54rbpmols1w52hfdx

 

________________________________________________________________________

________________________________________________________________________

 

I'm stealing the below observation from someone on Twitter yesterday, but no matter what happens with the storm early next week it will be interesting to see how that helps develop (or hurts) any sort of NAO block after next week. 

0z GFS pumps up the heights , but then scootches it all out to the east. If that were to roll back west, it could create some interesting scenarios:

giphy.gif?cid=790b7611c83f4586d8d05bed88

 

IMO, the Pac jet is partly why that scootches on east, so if I were betting, I would go with the scootch option right now, but the atmosphere is chaotic, so if the trajectory of the Pac jet is slightly different, I guess it could maybe help roll it back west. 

It's also interesting that there seems to be a tendency for storms to want to develop along the east coast and try to pump up those heights:

giphy.gif?cid=790b7611a0aead98e57180fcf9

[sorry for the different parameter, but weathermodels doesn't have PVU for the Euro and I used the Control since I can get "sort of" an operational run for the ECMWF past 240 hours. ]

 

Someone mentioned in the general weather sub forum, while they were talking about the idea of a 1981-82 analogue, that 1981's Dec had a honking -NAO and a -PNA. I suppose that is one possible iteration if these storm keep trying to scoop up positive heights and build them over Greenland. 

 

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Holston makes some great points....

The EPS has been adamant about the -NAO for some time.  The 6z GFS oddly seems to match the EPS more than the GEFS in regards to the NAO look.  Interestingly, the EPS appears to be about to score the coup regarding the early season -NAO.  I didn't believe it a few weeks ago, but that feature is now only about five days out on modeling.  I tend to lean EPS on this since it identified the NAO potential.  I think the GEFS is playing catch-up.  But again, we all know how tough it is for models to identify NAOs in advance - VERY difficult for them.  Last winter the NAO remained in place despite a terrible Pacific set-up.  All of that said, the LR looks blocky.  IF the NAO develops, always good to remember that modeling has a real problem with breaking it down too quickly.  

Anyone have the MJO forecast for later this month?

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8 hours ago, Carvers Gap said:

Holston makes some great points....

The EPS has been adamant about the -NAO for some time.  The 6z GFS oddly seems to match the EPS more than the GEFS in regards to the NAO look.  Interestingly, the EPS appears to be about to score the coup regarding the early season -NAO.  I didn't believe it a few weeks ago, but that feature is now only about five days out on modeling.  I tend to lean EPS on this since it identified the NAO potential.  I think the GEFS is playing catch-up.  But again, we all know how tough it is for models to identify NAOs in advance - VERY difficult for them.  Last winter the NAO remained in place despite a terrible Pacific set-up.  All of that said, the LR looks blocky.  IF the NAO develops, always good to remember that modeling has a real problem with breaking it down too quickly.  

Anyone have the MJO forecast for later this month?

If the mjo stays in 4, 5 and 6, which are warm phases, will the qbo be enough to keep the -nao going for a while? Pacific may have been bad last winter, but probably alot worse this winter so we would want alot of help from Atlantic to have a chance 

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10 hours ago, Carvers Gap said:

Anyone have the MJO forecast for later this month?

For one of the few times I can remember, the RMM plots looks pretty similar between the operational GFS and Euro:

Euro RMM:

aYG3u2M.png

 

GFS RMM:

Q3WPWPH.png

 

GEFS RMM:

JIxSuMo.png

 

In terms of atmospheric convection, there seems to be a pretty good spread all across the W Pac and Maritime Continent:

giphy.gif?cid=790b7611dc7981a3ea3f835b5b

 

Western Pac had petered out a bit for a couple of days (at least that's how it seemed to me), but looks sorta healthy again.

 

Michael Ventrice has a cool new way to visualize the way tropical convection helps modulate the Pac jet:

giphy.gif?cid=790b76114f811549b07918add1

source: http://www.atmos.albany.edu/student/ventrice/real_time/maps/mjo/global_analyses.html

You can watch the jet extend as the VP200 anomalies drift east.  To me, it looks like the MJO wave is trying to creep towards the western Pac, but weakening a bit as it does so. 

 

Last but not least we have the Paul Roundy Waves page:

giphy.gif?cid=790b76118e8869a41f842d6051

source: http://www.atmos.albany.edu/facstaff/roundy/waves/analogs/analogs.html

 

I think that animation is showing the heights at 300mb as they might evolve through mid December, given similar situations in the tropics (but I may be totally misusing or misinterpreting that data and animation). If someone has a better read on the Roundy data, please let me know so I can use it in a better way. 

 

 

 

 

 

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2 hours ago, Holston_River_Rambler said:

For one of the few times I can remember, the RMM plots looks pretty similar between the operational GFS and Euro:

Euro RMM:

aYG3u2M.png

 

GFS RMM:

Q3WPWPH.png

 

GEFS RMM:

JIxSuMo.png

 

In terms of atmospheric convection, there seems to be a pretty good spread all across the W Pac and Maritime Continent:

giphy.gif?cid=790b7611dc7981a3ea3f835b5b

 

Western Pac had petered out a bit for a couple of days (at least that's how it seemed to me), but looks sorta healthy again.

 

Michael Ventrice has a cool new way to visualize the way tropical convection helps modulate the Pac jet:

giphy.gif?cid=790b76114f811549b07918add1

source: http://www.atmos.albany.edu/student/ventrice/real_time/maps/mjo/global_analyses.html

You can watch the jet extend as the VP200 anomalies drift east.  To me, it looks like the MJO wave is trying to creep towards the western Pac, but weakening a bit as it does so. 

 

Last but not least we have the Paul Roundy Waves page:

giphy.gif?cid=790b76118e8869a41f842d6051

source: http://www.atmos.albany.edu/facstaff/roundy/waves/analogs/analogs.html

 

I think that animation is showing the heights at 300mb as they might evolve through mid December, given similar situations in the tropics (but I may be totally misusing or misinterpreting that data and animation). If someone has a better read on the Roundy data, please let me know so I can use it in a better way. 

 

 

 

 

 

The EMON(EMOM?), swings the MJO to colder phases late though.  The EPS/GEPS are just about opposite with 500 heights after d10 when compared to the GEFS.  Was kicking around with @tnweathernut on a sidebar if maybe the GEFS handles the IO a bit better?  I probably lean towards the EPS, but that model has flat burned me in November in the past!!!  Will be fun to watch.  

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EPS and GEPS double down on a continuation of BN heights in the d10-15.  GEFS now "toying" with the idea.  Modeling is now beginning to show ridging along the western coast of North America.  What we don't want to see is a strong ridge in the Aleutians IMHO.  Not seeing that consistently, but it has shown up on a few operational models.   I think the amplification next week is now highly likely.  Could be 1-2 shots of winter like air masses.  After that, that is the question mark.  The MJO certainly seems to be an opposite signal of what the EPS is signaling.  Though, as noted above, the EMON did show it moving out of warmer territory.  IMHO, the MJO becomes really important as we get deeper into December.  IO definitely has people skittish right now - as it should.

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1 hour ago, Carvers Gap said:

EPS and GEPS double down on a continuation of BN heights in the d10-15.  GEFS now "toying" with the idea.  Modeling is now beginning to show ridging along the western coast of North America.  What we don't want to see is a strong ridge in the Aleutians IMHO.  Not seeing that consistently, but it has shown up on a few operational models.   I think the amplification next week is now highly likely.  Could be 1-2 shots of winter like air masses.  After that, that is the question mark.  The MJO certainly seems to be an opposite signal of what the EPS is signaling.  Though, as noted above, the EMON did show it moving out of warmer territory.  IMHO, the MJO becomes really important as we get deeper into December.  IO definitely has people skittish right now - as it should.

As you know Carver, the MC isnt a colder phase, except early on that promotes a blocking signal. We would want to see the AO and NAO stay negative more times than not to give us a chance this winter imo because the troughing in GOA  will be a common occurrence this winter. I would like to see it shift but not sure how that can occur 

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More Invests in the Indian Ocean sap the convection. No wonder the MJO goes into the circle of death. -NAO can do heavy lifting, and it's negative enough to do so, but only temporary as Pacific influences cause undercutting. 

December 2005 is right up with with December 1989 for full winter than full cancel. Speaking of cancel all the weeklies have canceled December. I wouldn't worry about the 3-6 week forecasts though. 

Actually yeah I would. If anything can go wrong, it will.

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Some fairly massive differences this morning in the overall North American pattern between the EPS/GEPS and GEFS.  EPS/GEPS is a strong, early season shot of repetitive cold while the GEFS is a trough out West.  This has been a persistent difference for a couple of days.  I don't discount either camp on this.  I see sound reasoning for both portrayals. Something to watch.  

Weeklies looked a little bit more back and forth to me vs a December cancel.  Always a fight to get it to snow early IMBY, though recent years have bucked that trend.  More of a shift from a net cold(with warm intrusions) to a net warm(cold intrusions) look to me.

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2 hours ago, Carvers Gap said:

Some fairly massive differences this morning in the overall North American pattern between the EPS/GEPS and GEFS.  EPS/GEPS is a strong, early season shot of repetitive cold while the GEFS is a trough out West.  This has been a persistent difference for a couple of days.  I don't discount either camp on this.  I see sound reasoning for both portrayals. Something to watch.  

Weeklies looked a little bit more back and forth to me vs a December cancel.  Always a fight to get it to snow early IMBY, though recent years have bucked that trend.  More of a shift from a net cold(with warm intrusions) to a net warm(cold intrusions) look to me.

Think they're having trouble with the Greenland block...Gefs wants to basically go Pac driven and basically overpower the -NAO affect. 

    With that firehouse pac jet, it would sure halp to have a strong -AO in conjunction with the-NAO. Imo, that would help counter the terrible Pac setup.

    

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Yeah it looks volatile up and down temps. NAO may hang in there longer than progged on the weeklies. However the GOA low is likely, given the MJO pulse died an ugly death. IO Invests sapped it.

Big question is a West Coast ridge (USA not Canada). Models missed that for the Mon-Tue cold coming in. 10 days ago models were meh. Now we have a 90th percentile November cold shot coming. 

So while the Arctic and Pacific battle it out, the US West Coast may be a tie breaker. Do we torch, or are models missing another West Coast ridge?

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Very persistent and somewhat conflicting features still showing in the LR....BN heights over Alaska and the SE/EC of the US.  If taken verbatim, Alaskan cold would periodically break loose and head southeast under the persistent AN heights over Greenland, Davis Straits, or Hudson Bay.  Warmer air would intrude between cold shots.  Whether this can persist is another question altogether.  I tend to think an Alaska vortex wins most of the time.  However, we have discussed this on here many times...during the 70s and really early/mid 80s a cold Alaska was a good thing here.  At some point, it was heading southeast.  Was just a matter of time.  That has not been the case during the past couple of decades in general.  Right now the EPS, has handled the LR better IMHO.  GEFS is playing catch-up as evidenced by the cold coming this week.

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2 hours ago, Carvers Gap said:

Very persistent and somewhat conflicting features still showing in the LR....BN heights over Alaska and the SE/EC of the US.  If taken verbatim, Alaskan cold would periodically break loose and head southeast under the persistent AN heights over Greenland, Davis Straits, or Hudson Bay.  Warmer air would intrude between cold shots.  Whether this can persist is another question altogether.  I tend to think an Alaska vortex wins most of the time.  However, we have discussed this on here many times...during the 70s and really early/mid 80s a cold Alaska was a good thing here.  At some point, it was heading southeast.  Was just a matter of time.  That has not been the case during the past couple of decades in general.  Right now the EPS, has handled the LR better IMHO.  GEFS is playing catch-up as evidenced by the colds coming this week.

   Excellent post buddy ! Yeah, I remember those days of old... We've cashed in with decent snowfalls with that setup. I will note; the 60's also had that pattern rather often and as most know that Decade was basically cold/snowy. A -PDO and -NAO was dominate overall. 

      Many nowadays, particularly the younger crowd, including Mets, tend to go automatic mild in this area with the Alaskan vortex or trough(for obvious reasons). 

   A SW US Ridge and strong block in the areas portrayed can produce a pattern where we can cash in still with cold and snow.

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Think we will see a warm up into Dec.,maybe not that bad right now,GEFS might be to slow.Euro and CfS both show the MJO starting to strenghten into the WP into Dec.,think the question will be where it goes after.Typical NINA seemingly,cold front end,sucky after that

ecmwf_z500a_wpac_8.png

gfs-ens_z500a_us_65.png

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8 hours ago, jaxjagman said:

Think we will see a warm up into Dec.,maybe not that bad right now,GEFS might be to slow.Euro and CfS both show the MJO starting to strenghten into the WP into Dec.,think the question will be where it goes after.Typical NINA seemingly,cold front end,sucky after that

ecmwf_z500a_wpac_8.png

gfs-ens_z500a_us_65.png

Jax, I actually think it will be a back loaded winter imo. I know that's probably outlandish in a niña typically, but December looks to start and stay warm for a while. Especially since the niña looks to become more east based than originally thought and -qbo. I just feel like the Pacific being in bad shape will not allow a front loaded winter. We shall see 

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3 hours ago, Mr. Kevin said:

Jax, I actually think it will be a back loaded winter imo. I know that's probably outlandish in a niña typically, but December looks to start and stay warm for a while. Especially since the niña looks to become more east based than originally thought and -qbo. I just feel like the Pacific being in bad shape will not allow a front loaded winter. We shall see 

Could be but right now it don't really look that way.SOI still looks to be more NINA.MJO right now is being shown climbing out the COD into the WP into the first of Dec.,that should be more BN rather than AN.

IF the CFS were to be believed this far out it will weaken some into Dec then strenghten again into the WP into week3 of Dec.,that shouldn't be a warm signal as long as it's out of a COD..JMO

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2 hours ago, jaxjagman said:

Could be but right now it don't really look that way.SOI still looks to be more NINA.MJO right now is being shown climbing out the COD into the WP into the first of Dec.,that should be more BN rather than AN.

IF the CFS were to be believed this far out it will weaken some into Dec then strenghten again into the WP into week3 of Dec.,that shouldn't be a warm signal as long as it's out of a COD..JMO

I've heard into the the Maritime  continent with mjo but who knows this far out. Beginning of December looks warm regardless 

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We’ve got some good thunderstorms rolling across the state today.  Nice severe threat just south of brownsville, tn that should pass through around 3:45.  Half inch hail associated with this cell as well.  Interesting day weather wise in west TN,  looks like tomorrow will be a cold start to the week 

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Just now, AMZ8990 said:

We’ve got some good thunderstorms rolling across the state today.  Nice severe threat just south of brownsville, tn that should pass through around 3:45.  Half inch hail associated with this cell as well.  Interesting day weather wise in west TN,  looks like tomorrow will be a cold start to the week.  Had our first hard freeze Friday morning, Trees will be completely bald in 2-3 weeks if that 

 

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42 minutes ago, AMZ8990 said:

We’ve got some good thunderstorms rolling across the state today.  Nice severe threat just south of brownsville, tn that should pass through around 3:45.  Half inch hail associated with this cell as well.  Interesting day weather wise in west TN,  looks like tomorrow will be a cold start to the week 

We don't know what thunder sounds like here anymore,you got some convection

Weathernerds Sat.png

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15 hours ago, jaxjagman said:

We don't know what thunder sounds like here anymore,you got some convection

Weathernerds Sat.png

Had a couple nice rumbles yesterday for sure, that stinks it didn’t reach you in middle TN.  It Looked like a few cells were trying to hold together as they passed into the southern portion of middle Tn.  Ended up with around .68 in the rain gauge after everything cleared out 

 

 

 

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Looks like TRI will likely finish BN for November.  Right now we are at -2.1 and likely to strengthen that departure.  Will have to go back and look at which models actually got that right...  

Strong amplification this week.  Maybe some moderation next week, and then uncertainty persists.  I would urge caution(on way or the other) when viewing LR model output during November as verbatim.  Right now, I think Cosgrove is on to something with his most recent FB thoughts.  Basically, he says a warm start to December(2-3 weeks at least), but with the stage being set for a typical and possibly severe cold outbreak to end the month.  I am leaning in that direction, but not quite there yet.  Lots of understandable volatility in modeling right now.  The GEFS in particular seems a bit blind to trough amplification in the East.  Something to watch if it consistently misses those.

 

 

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