December 2025 Short/Medium Range Forecast Thread

[Carvers Gap]

I don’t buy the 12z EPS right now.  It has no support from its deterministic model and has been wrong for several weeks in trying to slide a permanent ridge into the east.  I think a ridge is coming but more likely around the 20th.  I can’t tell if it just rolls through or is a pattern change.   I could be wrong, but I think we are good through the 18th with possibly one more trough after that before we get a break. 

[John1122]

11 minutes ago, Carvers Gap said:

Interestingly, the Euro Weeklies control and ensemble are exactly opposite again.  Last time, the control won that battle.   The control is  30 day strong trough.

As for the MJO, there is some activity in 7-8-1-2.  This morning it began the anticipated loop/stall in 8.  I have little doubt the convection forecast for 1-2 will eventually propagate into 6.  It looks to me like that will happen sometime in the third or fourth week of December.  It could be earlier.   Currently the MJO plot is in 8 and the atmosphere reflects that with an eastern trough in place and eastern troughs forecast through roughly Dec 20.
 

Again, it is early December.  This is not snow climo for valley locations.  

Griteater was talking about the MJO, saying that while it's in Phase 8 per RMM, a KW/convection area flares in the Indo/Pacific and causes it to act like it's in Phase 6 through around December 12th-20th, before clearing and returning to a phase 8 look. That's likely the culprit behind the big warm up being modeled.

[Carvers Gap]

19 minutes ago, John1122 said:

Griteater was talking about the MJO, saying that while it's in Phase 8 per RMM, a KW/convection area flares in the Indo/Pacific and causes it to act like it's in Phase 6 through around December 12th-20th, before clearing and returning to a phase 8 look. That's likely the culprit behind the big warm up being modeled.

I just don’t see the evidence of it being in 6.  There is no ridge in the east at the moment.   Only the EPS is modeling a big warm up.  It could happen.   There were some overnight runs which support that.  But the EPS has struggled mightily.  All of these warmup have yet to verify.  I think after the 20th seems right.

[Carvers Gap]

I do think there will be a ridge which rolls through between the cold shot on the 14th and the next one on the 18th.  That has been strongly modeled,  Bastardi has noted the WPO has been erroneously modeled by the Euro/EPS suite for weeks.  He thinks there is a problem with its algorithm.  He noted the WPO appears to be driving the pattern.  When it weakens, other drivers take over. 

[Carvers Gap]

I think the bigger warmup comes between Dec 22 and mid Jan…that could be wrong, but that is what it appears to me.  Lots of precip in the MC at that time.

[Carvers Gap]

Currently snow is falling in west Kingsport. A little band has been set up.  Just barely missed today.