December 2025 OBS and Discussion

[uofmiami]

22 minutes ago, psv88 said:

I hope you married her!

The amount of dumb shit i did for gfs I didnt marry was insane. If i had only known better haha. What a waste!

I didn't marry her, LOL!  I concur, young & dumb back then.

[donsutherland1]

Winter beauty:

[Roger Smith]

Don, where does 2025-26 sit now in your winter severity index? 

[donsutherland1]

The wind will diminish overnight, but a cold regime will remain in place. Below normal temperatures will continue into at least the middle of the first week of January. Some flurries or snow showers are possible late Thursday into Friday in parts of the region. 

The first week of January will likely have a mean temperature below 30° in New York City. The last time that happened was in 2018. The only years since 2000 with a sub-30° mean temperature for the opening week of January were 2001, 2010, 2014 and 2018.

December 2025 will finish with a maximum monthly temperature of 58° in New York City. The last time December had a monthly maximum temperature below 60° was in 2019 when the monthly high was 58°. This will be only the fifth such occurrence since 2000 (2003, 2004, 2005, and 2019 are the cases since 2000).

The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was -0.7°C for the week centered around December 24. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.33°C and the ENSO Region 3.4 anomaly has averaged -0.68°C. La Niña conditions will likely continue into at least late winter.

The SOI was +6.49 today. 

The preliminary Arctic Oscillation (AO) was -1.580 today. 

Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a cooler than normal December (1991-2020 normal). December will likely finish with a mean temperature near 33.9° (5.2° below normal). That will make December 2025 the coldest December since 2010 when the monthly mean temperature was 32.8°. It would also make 2025 the third coldest December since 2000.

Supplemental Information: The projected mean would be 3.5° below the 1981-2010 normal monthly value.

[donsutherland1]

52 minutes ago, Roger Smith said:

Don, where does 2025-26 sit now in your winter severity index? 

I will check it when I get back home tomorrow evening.

[lee59]

Some snow showers that could leave a light accumulation  tomorrow evening. Could be the first time in years on New Years Eve.