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Winter 2024/2025 December Thread


AMZ8990
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35 minutes ago, John1122 said:

Got 1/4th inch or so down but coverage is breaking up some. There's another good slug of moisture in Kentucky that hopefully makes it here. 

About an inch here . Rather surprising considering the small flakes although, quarter inch diameter flakes came down thick for awhile so, apparently why. Hopefully, Snow fills back in. 

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2 minutes ago, Daniel Boone said:

About an inch here . Rather surprising considering the small flakes although, quarter inch diameter flakes came down thick for awhile so, apparently why. Hopefully, Snow fills back in. 

We had big quarter or bigger sized flakes but it was 34/33 then after I hit 32 it snowed about 15 minutes and slacked off. 

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Just now, John1122 said:

We had big quarter or bigger sized flakes but it was 34/33 then after I hit 32 it snowed about 15 minutes and slacked off. 

That's sad man. We had flakes like that this Afternoon in the Snow Shower's but was above freezing so didn't stick. A dusting from those in the heavier ones but melted quickly.

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2 minutes ago, Daniel Boone said:

That's sad man. We had flakes like that this Afternoon in the Snow Shower's but was above freezing so didn't stick. A dusting from those in the heavier ones but melted quickly.

I'm happy with seeing it fall at this time of year. My cousins there only live about 5 minutes away. So I can drive a little and see a couple inches, if nothing else. 

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The ensembles have a very cold pattern to start December.  We are going to see a lot of variation in modeling.  Last night's snow was lost between d7-10, and then very slowly came back on modeling.  I don't see a ton of snow on modeling this morning, but let's see how this begins to looks as it gets into range.  A rough window is November 30-Dec14.  Big questions after that whose answers mighta allow us to squeeze a couple more weeks of less extreme cold out of that pattern.  One warning(and I don't see this yet...if anything quite the opposite), sometimes modeling will be too quick in bringing the strongest cold.  Right now, ensembles are about as robust as one can get at 500.

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This is what I look at when I am looking at modeling in the long range...

Image 1:  Euro Weeklies Control 30d 500map...What could go wrong, but what I don't think will happen.  Referring to previous winters and not this set of model runs....the trough tucks out west after several dozen runs on LR ext modeling of it being in the East.  There is precedent or that during past winters.  Basically, we have followed severe cold for weeks on the weeklies, and at the last minute it dives west of the Rockies.  Again, I don't see that right now and the ensemble for the same model doesn't depict that at this time.

Image2:  Euro Weeklies ensembles 30d 500map....Looks about right.  EPO ridge dominates and then retrogrades westward.  How far it retrogrades to the West will be a big factor in how long it stays cold here. 

Image 3:  GEFS ext 30d 500map....Please note it doesn't go out as far as the Euro, but still....not bad.

Image 4:  That is the CFSv2 from this morning for December, January, and March.  It probably is dealing with a bit of feedback - meaning keeping the trough in the East too long.  However, some of the analogs in my winter forecast have exactly that, so I can't discount that.  Big EPO ridge during Dec-Jan.  NAO pops in Feb.

I noticed Cosgrove mentioned that his winter forecast has been cooled down a bit to reflect the early pattern of winter and more cold intrusions than originally thought.  Right now, January is(and has been) a bit of a mystery for me.  What we are seeing could just be classic Nina climatology even though we aren't at Nina thresholds.  We could still(and I think we are) seeing Nina climatology reflected at the North American surface as evidenced by the warm fall and flip to cold during late November.  If the CFSv2 is even half right, we take that and run.  If Nina climatology is in play, we should see LR ext modeling warm for much of the rest of winter.   Remember, LR ext modeling had December as warm before it flipped cold...Nina climatology won out.  That said, and I sound like a broken record, there are two very different paths in analog packages for January.  Either fits climatology.  That sounds like a cop out, but that is the lay of the land.

I still tend to think Jan-Feb are going to be warm.  But if you look at my winter forecast ideas, I noted that January is sketchy and that gave me pause for that month.  I have two sets of analogs built or that month, and they are very, very different.  Even Mark Reynolds on the WJHL11 winter forecast noted that there are two different analog packages for Nina winters.  If this goes to a weak La Nina, that is a significant development towards having a colder winter forecast than I have listed.  Technically, I can still change my seasonal forecast as it isn't meteorological winter.  However, I generally go with the idea that first ideas are often correct, and only change if certain you are wrong.  What I think I potentially have correct is that the pattern would flip cold during late November, and that winter starts cold for December.....So, that is tough for me to change since those ideas "seem" correct so far.  To be fair, December hasn't occurred, and there are no certainties in weather forecasting at this range. But those cold looks for January could flip warm IF the warm set of analogs turns out to be right.  My lean towards a warm Jan-Feb is diminishing though with each passing day. 

Part of me wonders if the base pattern is the trough in the East???  That said, you can see the SER fight the cold over the southeast, so I think the SER will be a player.

More later.

5e458e84-5c69-4c3d-8fa8-b1472b5c1e8b.png
f951beda-f467-4d60-8725-9c2b80acf43b.png
7de655df-3f5f-483e-99a1-19acbfdba39b.png
90f45bdc-034b-4ada-aede-68311d63d649.png

 

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And this is why January gives me great pause.  This is from my winter forecast.  I haven't looked, but I bet the PDO this go around is less optimal.  However, this is part of the reason that I am less confident than I have been the past two winters.....Again, I lean warm for January, but there is precedent for a much different outcome.

I am going to go ahead and add these.  And I am far, far deeper into this than intended...Sorry, this is kind of a "stream of thought" post, and maybe not as scientific as it should be.  I also want to add 16-17 into the mix at it was a first year La Nina and should be weighted equally or more to 17-18.  But here is why I am far less confident this winter.  See the 94-95 moderate Nino listed in the graphic at the very bottom of this post.  This past winter reminded me of that type of winter - blah and not a lot of chances.  Now, what came after 94-95?  The winter that shall not be named, because I just won't invoke a winter that is a benchmark winter of my lifetime, and it was true winter.  It was a weak La Nina following a moderate El Nino.  It is also a winter that maybe doesn't fit the current warm basin look of the Pac which is why I haven't used it.  That said, it might deserve some weight though I haven't given it any.  Just beware.

 

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5 minutes ago, Carvers Gap said:

And this is why January gives me great pause.  This is from my winter forecast.  I haven't looked, but I bet the PDO this go around is less optimal.  However, this is part of the reason that I am less confident than I have been the past two winters.....Again, I lean warm for January, but there is precedent for a much different outcome.

I am going to go ahead and add these.  And I am far, far deeper into this than intended...Sorry, this is kind of a "stream of thought" post, and maybe not as scientific as it should be.  I also want to add 16-17 into the mix at it was a first year La Nina and should be weighted equally or more to 17-18.  But here is why I am far less confident this winter.  See the 94-95 moderate Nino listed in the graphic at the very bottom of this post.  This past winter reminded me of that type of winter - blah and not a lot of chances.  Now, what came after 94-95?  The winter that shall not be named, because I just won't invoke a winter that is a benchmark winter of my lifetime, and it was true winter.  It was a weak La Nina following a moderate El Nino.  It is also a winter that maybe doesn't fit the current warm basin look of the Pac which is why I haven't used it.  That said, it might deserve some weight though I haven't given it any.  Just beware.

 

Good information, so, what you are saying is that, essentially, we could have two stark contrasting results at the end of the winter. Course, there are stark contrasts in an ordinary winter depending what part of the state one is in, I know that is the case simply in Middle TN! 

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19 minutes ago, matt9697 said:

Good information, so, what you are saying is that, essentially, we could have two stark contrasting results at the end of the winter. Course, there are stark contrasts in an ordinary winter depending what part of the state one is in, I know that is the case simply in Middle TN! 

Nina climatology often supports a cold end to November and cold December.  Then, it warms with diminishing chances for cold in the western forum areas.  That is the bulk of climatology.  

However, there is a group of analogs for weak La Nina years which produce very cold winters for almost all of the forum areas.  They make-up about 1/3 of weak La Nina analogs and most of those years are the benchmark winters for the Tennessee Valley.  I am not saying those are in play right now, but I can't rule it out.  I suspect modeling is falsely perpetuating the eastern trough past Christmas, but there is is about a 1/3 chance that this winter could be "base cold."  To quote Ben Kenobi, "Now that is a term I haven't heard in a long, long time."

It should be noted that the collapse(or lack of occurrence at all) of the La Nina was poorly forecasted.  ENSO forecasting at range can be bust city.  So, with the ENSO state being a bust for this winter...that opens the door every so slightly for a colder winter due to weak La Nina climatology coming into play.  Again, 1/3 is the ratio to remember.

Many of us have noted that we are a bit uneasy about this winter's forecast, because those analogs are the opposite of the other 2/3.

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Four typhoons in three weeks raked the Philippines and then dissipated in the vicinity of China. All that energy is maintained - somewhere. 

My going thinking is that this time of year that's not a ridge over China. Instead it amped up the East Asia pattern. Trough is in China under Siberia ridge. Reflection downstream is the same for the US and Canada. It's probably temporary. 

I remain quite mild for the winter. Caution is that La Nina seems to have stalled or even reversed. La Nina failures would not surprise me with the warmer background state. Still, reverting to a stubborn SER is my prognosis. 

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Day 8-14 CPC analogs from yesterday.  Triple weighted '89.  Interesting to see an 09-10 analog show up in there - not a La Nina nor a La Nada analog, but a great winter nonetheless.  I would be interested to learn how that made its way into that analog set.

19891218
19631213
19581210
19891213
19551129
19891208
19561201
19581205
20091208
19761202
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Modeling continues to show a storm in the under D10 range. Rainer on the Euro for areas outside the Plateau/Mountains, NETn/SWVA, suppressed and frigid on the GFS with a bit of snow in South Carolina as things develop too late. Canadian is a Tennessee special, especially south of 40. Euro/Canadian are close on depiction, just a little colder on the Canadian and about 12-24 hours later.

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Still not a lot of changes to earlier thinking.  If anything the 500 maps of all three major ensembles continue to advertise a very strong EPO.  I have to think that breaks down at some point, but modeling has it through d16.  Even though Nina is still technically a Nada...The potential cold start to winter is very classic Nina climatology.  It does look like the NAO is trying to fire.  That is not surprising given that it has been more active during winter after going a couple of decades without much activity.  

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2 hours ago, Carvers Gap said:

Still not a lot of changes to earlier thinking.  If anything the 500 maps of all three major ensembles continue to advertise a very strong EPO.  I have to think that breaks down at some point, but modeling has it through d16.  Even though Nina is still technically a Nada...The potential cold start to winter is very classic Nina climatology.  It does look like the NAO is trying to fire.  That is not surprising given that it has been more active during winter after going a couple of decades without much activity.  

We have better SSTS around Newfoundland this go around too allowing for the desired 50-50 Low setup. 

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Still very cold ensembles.  The 12z GEPS is very cold.  It makes me nervous, because it often catches the cold before other ensembles.  If that verifies, we could be looking at severe cold incoming.  The 12z Euro and CMC both at varying times have incoming winter storms.  It is possible that the pattern is dry as the EPO ridge is so, so tall.  That combination often forces us to rely on northwest flow events.  Either way, buckle up.  Wild pattern looks to be on tap if you like winter.  I tend to think the Euro/CMC model group(once they "see" the cold) are formidable.  The Euro was crazy, crazy cold at the end of its run.  I am not so sure that isn't record breaking.  I haven't looked.

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1 hour ago, Carvers Gap said:

Still very cold ensembles.  The 12z GEPS is very cold.  It makes me nervous, because it often catches the cold before other ensembles.  If that verifies, we could be looking at severe cold incoming.  The 12z Euro and CMC both at varying times have incoming winter storms.  It is possible that the pattern is dry as the EPO ridge is so, so tall.  That combination often forces us to rely on northwest flow events.  Either way, buckle up.  Wild pattern looks to be on tap if you like winter.  I tend to think the Euro/CMC model group(once they "see" the cold) are formidable.  The Euro was crazy, crazy cold at the end of its run.  I am not so sure that isn't record breaking.  I haven't looked.

Yeah, shades of Dec 89 with a touch of January 2014 and Feb 2015 with those looks.

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2 hours ago, Daniel Boone said:

Yeah, shades of Dec 89 with a touch of January 2014 and Feb 2015 with those looks.

Here are the d8-14 analogs for today from CPC:

19561129
19851221
19881208
20081130
19581212
20021128
19891221
19561124
19761124
19881213

Any thoughts on these?

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3 hours ago, Carvers Gap said:

Still very cold ensembles.  The 12z GEPS is very cold.  It makes me nervous, because it often catches the cold before other ensembles.  If that verifies, we could be looking at severe cold incoming.  The 12z Euro and CMC both at varying times have incoming winter storms.  It is possible that the pattern is dry as the EPO ridge is so, so tall.  That combination often forces us to rely on northwest flow events.  Either way, buckle up.  Wild pattern looks to be on tap if you like winter.  I tend to think the Euro/CMC model group(once they "see" the cold) are formidable.  The Euro was crazy, crazy cold at the end of its run.  I am not so sure that isn't record breaking.  I haven't looked.

It would not surprise me to see crazy cold.  The last 2 winters we have had crazy cold for a week.  Though that was really the only cold both winters.  It was cold enough to kill alot of vegetation & landscaping.  Many of the shrubs are still trying to come back on my neighbors house.  I removed mine.  I even lost new shrubs last winter & had to replace.  I’d prefer not to have to do it again.  Though I did go with landscaping that supposed to survive down to -10/15.

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35 minutes ago, Carvers Gap said:

Here are the d8-14 analogs for today from CPC:

19561129
19851221
19881208
20081130
19581212
20021128
19891221
19561124
19761124
19881213

Any thoughts on these?

19891221 (bolded) was when there was a very rare/historic SE coastal heavy snowstorm along with extreme cold for a deep SE snow (temperatures in the lower 20s with lots of wind).

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16 minutes ago, GaWx said:

19891221 (bolded) was when there was a very rare/historic SE coastal heavy snowstorm along with extreme cold for a deep SE snow (temperatures in the lower 20s with lots of wind).

Sorry.  I should have specified the non ‘89 winters.  I was at UT at the time.  We missed on a massive snowstorm.  

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3 hours ago, Carvers Gap said:

Here are the d8-14 analogs for today from CPC:

19561129
19851221
19881208
20081130
19581212
20021128
19891221
19561124
19761124
19881213

Any thoughts on these?

December 56 warmest on Record. Jan 57 near normal, Feb much above average.

December 85 cool with a white Christmas with above average Winter Snow. All 3 Months Colder than Avg. 

December 88 near normal January 89 mild , February normal. Slightly below average Snowfall. 

08-9 near normal winter below avg snow.

  02-03 cold and snowy December thru Feb.

Dec and January 58 cold snowy. Slightly mild February.

Dec 89 record cold slightly above average Snow here. Ktri I think was below on Snowfall. Rest of Winter very mild.

Dec. 76 very cold above avg Snow. Went on to be one of coldest Winter's on Record with above average Snowfall.

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12 hours ago, Daniel Boone said:

December 56 warmest on Record. Jan 57 near normal, Feb much above average.

December 85 cool with a white Christmas with above average Winter Snow. All 3 Months Colder than Avg. 

December 88 near normal January 89 mild , February normal. Slightly below average Snowfall. 

08-9 near normal winter below avg snow.

  02-03 cold and snowy December thru Feb.

Dec and January 58 cold snowy. Slightly mild February.

Dec 89 record cold slightly above average Snow here. Ktri I think was below on Snowfall. Rest of Winter very mild.

Dec. 76 very cold above avg Snow. Went on to be one of coldest Winter's on Record with above average Snowfall.

Awesome.  And that is what I was thinking that might be....it is all over the place.  That means IMHO that there is above normal uncertainty for this winter.  I "think" we probably can get rid of the warm Decembers...at least through Christmas anyway.  After Christmas, maybe a switch to warm pattern or a brief warm-up.  I can't tell at this range.  It is interesting that we aren't seeing a lot o 2000s analogs with that, and that is interesting.  Either they try to factor out recency bias with their analogs, or there is a thought process that this winter is not fitting recent analogs.  I don't know the answer to that.  The potentially cold start reminds me of 09-10, but I don't think it matches the ENSO state.  I will post the CFSv2 from this morning(likely suffering from feedback for Jan-Feb), and if it isn't actually suffering from feedback...that is not like many 2000s winters.  Maybe 14-15?  Maybe 09-10?  Could be something and could be nothing.  The CFSv2 is a flavor of the month model for me....changes a ton.  However, American modeling does well enough at very long range that I do pay attention, especially during early winter.

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1 hour ago, Carvers Gap said:

The seasonal CFSv2 from this morning...EPO and AO driven it appears to me.

8e0ee7d1-e3e4-484f-bc21-010253f2cca5.png

+TNH. Looks like heading the way Webber's research showed. There'll probably be short periods of Greenland blocking but not likely sustainable due to westerly QBO.

The tendency for LP wanting to hang out off the NE Coast and around Nova Scotia and South of Newfoundland should be there due to the SST'S and that will work to act to pump up blocking or pseudo block occasionally. If we recall in the great Feb 2015 Cold Snowy Pattern we had a positive NAO but continual LP development that would keep CPF and the Trough pulled down over the Eastern US in tandem with the +TNH and resultant+PNA. 

     IF that were to be the main Pattern, it would turn out rather harsh as we all know.

     I'm still not sure even at this juncture. It looked clear-cut couple months ago but, not now.

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