December 2025 regional war/obs/disco thread

[Torch Tiger]

Winter has arrived and we're all very excited to see what Santa brings us this year. A snowy SWFE? Killer cutter?  We'll soon find out.

Also there are growing rumors of a latitudinal winter which could lead to a major regional war. Stay tuned!

[40/70 Benchmark]

I'm pretty confident on an above average snowfall month north of the pike, at least.

 

Here is my analysis from a couple of weeks ago, which is largely on track IMO...but the risk is colder.

 

Expect this sale style of deviation from the MC forcing during the early portion of the season.

 

December 2017-January 2018:

December 2024-January 2025:

 

 

An official SSW as defined by the reversal of the mean H85mb zonal westerly winds is unlikely, however, there is a low probability of one as suggested both by the minority of guidance, and the December 4, 1981 analog. Should there be a reversal of the H85mb zonal winds, December 4th is a good estimation of the when the PV will reach its weakest point before the split, and subsequent recovery begins.

 

As per the expectation of a significantly weakened vortex resulting from bonafide warming that will fall short of a full zonal wind reversal, the December 2000 event is the preferred analog.

This is appropriate since 2000-2001 is also the top analog from the seasonal composite.

Accordingly, the polar vortex should have consolidated back to at least something approaching climatological levels prior to Christmas (18th-24th). It will then continue to strengthen with moderating temperatures in the east, per research conducted Lee et al (2019), which indicates that the arctic high regime is favored for less than 20 days following a weak PV. This is also consistent with the onset of a reflection event on December 21,1981, just over two weeks after the December 4th SSW.  There is a slight chance of Ku event between the first and 15th of the month.  The PNA should average negative during what will be active month, with numerous SWFE and overrunning events commencing by approximately the 10th. The probability for a White Christmas is above climatological levels given the active pattern and at least seasonable cold throughout the first half of the month, but it remains dubious for the coastal plane given the milder turn prior to the holidays. In fact, the proverbial "Grinch Storm" is more likely than not. A Pacific trough should begin to evolve towards the end of the month in conjunction with a rather stout PV, as a mild pattern ensues to ring in 2026.

 

The month of December will average anywhere near normal, anywhere to -1F to +2F, except near normal to +2F across the middle Atlantic.