December 2025 Short/Medium Range Forecast Thread

[Carvers Gap]

OTH, if January and Feb go to pot....my winter forecast from June scores yet again.  LOL.  FTR, I hope it doesn't verify.  

I think Larry Cosgrove nailed this seasonal outlook with the exception of the first 2.5 weeks of December being cold.  I strongly encourage everyone to find him on FB and read that seasonal outlook.  He has been zigging while everyone else has been zagging.  If he is right, and I have no reason to think he isn't, we will all be happy by the end of Feb.  But as Larry noted, patience will be king this winter.

Just imagine this pattern, but with January cold forcing its way southeast.  What happens in November(and early December), the winter often remembers.

[Carvers Gap]

BTW, Larry's idea is that winter's worst is from late January into March...and rough at that.  Gotta run.   Sorry, I hadn't posted much this morning.  

Dear Facebook, as I was pulling out of the garage I ran over a can full of blue paint.  It exploded under my truck.  I didn't know it until I drove around my cul de sac - twice!  I got to scrub lots of asphalt and the garage floor.  Meanwhile, I had to do a NASCAR fast wash down of the truck in order to get it on the road for one of my kids.  Anyway, BN heights(aqua blue...don't even get me started on how that color wound up in paint storage) went all over the place!!!  Maybe it is some kind of sign.

Trust me, I would rather be looking at raging warm weather models.  Haha.  Don't have sympathy.  Just know if you are having that kind of day...you are not alone!!!

[Carvers Gap]

Now that I am back and things have settled down a bit, here are a thought or two...

1.  Recent Nina winters have followed a fairly predictable pattern.  Cold end to November, cold start December, flip to warm around Christmas. and cold returns for late Jan and Feb, especially middle and western areas of the forum.

2.  I don't trust models right now past ten days - if that.  There has been a lot of feedback in the usual places.  So, pivot back to point number one....

3.  To me, the real question is whether we get one final cold shot right before Christmas - 50/50 for me on that one.  I think the warm-up after Christmas has been well advertised.  We know how the last warm-up worked out - cold.  Let's see how this one goes.

4.  There are things to track prior to Christmas.  I see roughly (4) windows to monitor.   I will try to dig a bit deeper later.  I got 0z, 6z, and 12z to look back through.  Tomorrow is gonna be even crazier.  

[Daniel Boone]

2 hours ago, John1122 said:

The Pacific hates us. It seems to always find a way to screw up everything for us. 

Yep. That Aleutian HP is where we need the LP to be. Need that HP over Alaska and need that LP near the GOA to move to Aleutians. As is, that Pac Jet's going to roar between the Goa Low and the Epac and West Coast Ridge. if it comes in strong enough it'll flood the US with Pacific Air and downslope off the Rockies spreading warmth. If it were to blast in further North it could potentially flood western and central Canada scouring the cold out. Kentucky Post was right on with that post about needing that Ridge to link with the Alaskan HP. 

[John1122]

32 minutes ago, Daniel Boone said:

Yep. That Aleutian HP is where we need the LP to be. Need that HP over Alaska and need that LP near the GOA to move to Aleutians. As is, that Pac Jet's going to roar between the Goa Low and the Epac and West Coast Ridge. if it comes in strong enough it'll flood the US with Pacific Air and downslope off the Rockies spreading warmth. If it were to blast in further North it could potentially flood western and central Canada scouring the cold out. Kentucky Post was right on with that post about needing that Ridge to link with the Alaskan HP. 

We needed the Pac jet to help pop the PNA but it's not worked out that way. 

[jaxjagman]

We'll know more in the next couple days where the MJO is going,now is when its getting destructive interference from Rossby/Kelvin Waves

[jaxjagman]

GTH Outlook Discussion

Last Updated - 12/09/25

Valid - 12/17/25 - 12/30/25

Following a very high amplitude Madden Julian Oscillation (MJO) propagation across the Pacific at the end of November, the intraseasonal signal has rapidly weakened as it crossed the Americas and Atlantic in early December and now resides within the unit circle. The strong MJO event was the result of constructive interference between the MJO itself and Kelvin Wave (KW) activity which have become more decoupled in recent days. Long range dynamical model ensembles depict the RMM-based MJO signal generally remaining within the unit circle, with some re-emergence into the Western Hemisphere around the end of week-2. While the GEFS and ECMWF show this evolution to some degree, the CFS is the most robust in its depiction of a more coherent loop of the RMM-based signal which comes out of the unit circle in phases 7 and 8 later in December. Velocity potential filtering indicates a very fast moving enhanced convective signal circumnavigating the globe during the next 2 weeks, despite the lack of an RMM-based signal appearing over the Eastern Hemisphere. However, an experimental projection of objectively filtered KW activity in phase space reveals a continuously circumnavigating signal, which at times constructively and destructively interferes with lower frequency modes. This makes for a rather complex and low confidence Global Tropics Hazards Outlook and is based mainly on La Nina composites and some consideration of dynamical models.