Winter 2024/2025 December Thread

[Daniel Boone]

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. 

[John1122]

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. 

[Daniel Boone]

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.

[John1122]

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. 

[Carvers Gap]

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.

[Carvers Gap]

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.

 

[Carvers Gap]

Just for kicks and giggles.  This is the CFSv2 seasonal control run for January.  Take a look at the cold analog package for January in the winter spec thread...and look at this.

[Carvers Gap]

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.

 

[matt9697]

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! 

[Carvers Gap]

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.

[nrgjeff]

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. 

[Carvers Gap]

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

[John1122]

In a less than usual situation, the GFS is actually warmer than the Euro and less snowy in the d7-11 range. But neither are particularly warm.