December 2025 OBS and Discussion

[bluewave]

2 hours ago, NorthShoreWx said:

We spiked to 48.4 at 9:40 am and are down 2 degrees since. That's been happening a lot recently with the max, or at least a secondary max before 10am.  I have no explanation for why.  I noticed the same on a couple of other local sensors.

Made it to 49° here with the MOS and raw guidance forecast for low 40s. Noticed the MOS from several days ago was around 50° but it shifted colder. Models often underestimate highs with sunny and windy downslope flow and the cold air lagging frontal passage.

[MJO812]

Eps again was too torchy in the long range.  Take the long range with a grain of salt. 

 

 

 

New run is colder

[North and West]

Eps again was too torchy in the long range.  Take the long range with a grain of salt. 
 
 
 
New run is colder

Honest question, why does everyone lose their minds with long range models (no matter that they show), when they’re just going to change anyway? It’s a seasonal tradition.


.

[MJO812]

8 minutes ago, North and West said:

Honest question, why does everyone lose their minds with long range models (no matter that they show), when they’re just going to change anyway? It’s a seasonal tradition.


.

Yep

[steve392]

I'm really really getting sick of this wind every single dam day.  

[donsutherland1]

Tomorrow will be a bit cooler with temperatures returning to the upper 30s. A weak system will bring some light snow or snow showers to the region on Tuesday. There is a chance that New York City could pick up a coating but a measurable snowfall is not a guaranteed outcome for the City. A 1"-2" snowfall is possible in the distant northern and western suburbs where it will be colder.

The temperature will likely remain above freezing throughout the day on Tuesday. In New York City, only 25.6% of storms have seen measurable snowfall with a daily low of 33° or above with just 9.2% seeing 1" or more snowfall. Almost three-quarters (74.4%) of such events have seen only a trace of snowfall.

No exceptionally cold or warm weather appears likely for the first week of astronomical winter.

The closing week of December could experience periodic warmer and cooler days. 

The probability that December 2025 will have a maximum monthly temperature below 60° has increased further. The last time that happened was in 2019 when the monthly high was 58°. If 2025 has a monthly high below 60°, that would 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 10. 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 -0.67°C. La Niña conditions will likely continue through at least mid-winter.

The SOI was +13.96 today. 

The preliminary Arctic Oscillation (AO) was +1.100 today. The PNA was -1.604. That is the lowest winter value since January 8, 2023 when the PNA stood at -1.618.

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 34.6° (4.5° below normal). 

Supplemental Information: The projected mean would be 2.8° below the 1981-2010 normal monthly value.