December 2025 Short/Medium Range Forecast Thread

[nrgjeff]

EPS followed the ECMWF warmer but it could be a one-off. AI version still has the back door front chances northeast Tenn. This is all for closer to the New Year. Basically we're looking for a little -NAO. Questions are mainly around whether the Pacific side will help, or just give us the Chinook finger. 

Of course Carvers I'm always down for mixing weather and basketball. Just like the Vols are back on track, perhaps the ECMWF will get colder again. The warm GEFS does not concern me.

PS that Vols game was about the only major vs major this week - a nice treat! 

[Carvers Gap]

@nrgjeff, are the new AI ensembles decent?  I notice the 12z GEPS and both AI ensembles (GFS/Euro) had a lot of cold members after 300.  

The Vols losing three straight was like looking at non-stop chinooks on modeling - same result, same set-up.  We needed that Louisville shake-up(red like an NAO! - it's a sign).

[Carvers Gap]

Cherry picking some stuff from the Euro Weeklies, though I didn't think the ensemble was half bad!

 

[Carvers Gap]

The one thing that makes the Weeklies(any brand) fallible is that they tend to perpetuate the week two pattern - true feedback. That is why it is important not to put to much stock in LR ext modeling unless IMHO they change from that two week pattern.  In other words, if the model doesn't continue in perpetuity...that is worth paying attention to.  I have seen cold patterns modeled for all six weeks...not even make it into week 3.  That also works for warm air masses.  So, that is why I like looking at the control which is basically just one big deterministic run.  

[Daniel Boone]

5 hours ago, Carvers Gap said:

Unfortunately, the Aleutian Ridge has been a staple of recent past Nina winters - the big red ball on 500 maps.  If forces a Rex block.

Models have a very difficult time "knowing" when it ends - much like the NAO.  I don't think there is a lot of data in that area, and that can be a problem.  It seems like the Aleutian Ridge has a tendency to disappear with little notice, and the trough kicks almost immediately eastward. Those ice and snow storms that middle and west Tenn have experienced occurred when that Aleutians Ridge pattern relaxed.  It seems to me that usually occurs between the first and third weeks of January.  

I know some think the trough retrogrades and does not come back.  If the NAO goes negative, that could balance things out.  We lacked the NAO w/ recent analogs where the trough pulled back, and wouldn't budge.  

There is a lot of uncertainty going forward.  I generally like uncertainty, because that leaves room for crazy weather.  In winter, that could be anything from severe (which I don't like) to winter storms.  

I think the key going forward is the NAO going negative.  It is the ingredient in many EC storms.  That doesn't necessarily help you all just to the west...but it can force sliders in addition to coastals.

Yeah, la nina augmented you might say. Nina actually strengthened a little recently after a steady weakening. Should see a rather fast weakening from here on. I think i'll go back and look at some NPAC Charts from 95-96 and see how or if the AR was prominent then. 

[Daniel Boone]

 This is this day in 1995 

Plymouth State Weather Center   Compare to Christmas then :  Plymouth State Weather Center

I know it just shows Site link but it goes directly to Map.

[Holston_River_Rambler]

We desperately need to fill up the thunder in the mountains index. There is hope tonight. 

[Holston_River_Rambler]

I got this one from the NCEP reanalysis site for todays date in 1995: