donsutherland1

A cooler than normal November is concluding. New York City is finishing with a monthly mean temperature of 47.2°, which is 0.8° below normal (0.5° below the older 1981-2010 baseline). A cold front will bring showers tonight into early tomorrow. Afterward, a prolonged stretch of below normal temperatures will likely continue into or through the second week of December. December 1-10 will be a solidly colder than normal period. The potential exists for the coldest first days of December since at least 2010 (34.6°, 6th coldest December 1-10 since 2000). The five coldest December 1-10 periods since 2000 were: 1. 30.6°, 2002 2. 32.2°, 2003 3. 32.4°, 2000 4. 33.1°, 2005 5. 33.4°, 2007 All 5 of these cases had measurable snowfall in Central Park. A storm will affect the region on Tuesday into Wednesday, bringing 0.50"-1.50" precipitation to the region. There is a distinct possibility that New York City could see its first measurable snowfall of the season, even as the storm will be mainly a rain event. Interior sections have the highest probability of seeing accumulations of snow. The coldest air mass so far this season could move into the region late in the week. The temperature will likely tumble into the 20s Thursday night into Friday in New York City. Another system could bring some light precipitation to the region during the weekend. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -0.7°C for the week centered around November 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.16°C and the ENSO Region 3.4 anomaly has averaged -0.65°C. La Niña conditions will likely continue through at least mid-winter. The SOI was -2.04 today. The preliminary Arctic Oscillation (AO) was -0.064 today.

TEMP _________DCA _ NYC _ BOS __ ORD _ ATL _ IAH __ DEN _ PHX _ SEA -1.0 -2.0 -2.0 -3.3 2.5 1.6 1.4 1.1 0.1 SNOW _______ DCA _ NYC _ BOS ___ ORD ____DTW ___ BUF __ DEN _ SEA _ BTV 10.0" 20.0" 40.0" 37.5" 45.0" 92.0" 40.0" 6.5" 80.0"

For perspective, no industry comes close to the explicit and implicit subsidies received by the fossil fuel industry. From the IMF:

Some December Snowfall Statistics: For Philadelphia, the December date(s) with the highest frequency of each snowfall threshold is: Measurable snowfall: December 14 and December 29: 15 occurrences 1.0" or more snow: December 5 and December 26: 10 occurrences 6.0" or more snow: December 19 and December 26: 3 occurrences 10.0" or more snow: December 26: 2 occurrences

The 11/30 0z and 6z GEFS has returned to a warmer outlook for much of North America after December 10th. It offers a credible alternative scenario. I'm still going with the EPS/ECMWF weeklies, as the GEFS has shown inconsistency. Moreover, the size of the rebound in temperatures (December 11-20 vs. December 1-10) would be both extreme and rare. Nevertheless, a look at the alternative scenario is still in order as a muted variation is plausible. The GEFS's development of a fairly strong PNA- is the key variable differentiating it from the colder baseline idea shown on the EPS. The latest two cycles of the GEFS show the development of a WPO-/EPO+/AO-/PNA- pattern. The GEFS maps are consistent with the largest cluster for the December 5-15 period (39%) of cases. WPO-/EPO+/AO-/PNA- Maps (Largest December 5-15 cluster): 500 mb Height Anomalies: Temperature Anomalies: GEFS (11/30 6z cycle): Days 11-15: 500 mb Height Anomalies (5-day average): Temperature anomalies (5-day average):

Central Park's frequency of measurable snowfall in December and record daily snowfall. December 26 is New York City's snowiest December date. Frequency of select daily snowfall amounts (1869-2024): Measurable snowfall: 22 times 1" or more: 16 times 6" or more: 5 times 10" or more: 5 times

From Iowa:

So far, 5"-7" of snow has fallen in the greater Chicago area. Daily snowfall records for November 29th have fallen in both Rockford and Chicago. The snowstorm will continue to blanket parts of the Great Lakes Region tonight into early tomorrow. Chicago and Milwaukee will likey see 6"-12" of snow. Some locally higher amounts are possible. Detroit could pick up 4"-8". Toronto could see 3"-6". In the New York City area, tomorrow and Monday will be somewhat milder. Showers are possible on Monday as a cold front moves across the region. Generally colder than normal conditions could then continue into or through the second week of December. Severe cold appears unlikely through at least the first 10 days of December. Nevertheless, December 1-10 will be a solidly colder than normal period. Moreover, a storm could affect the region on Tuesday into Wednesday, bringing 0.50"-1.50" precipitation to the region. There is a distinct possibility that New York City could see its first measurable snowfall of the season. Interior sections have the highest probability of seeing accumulations of snow. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -0.7°C for the week centered around November 12. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.16°C and the ENSO Region 3.4 anomaly has averaged -0.65°C. La Niña conditions will likely continue through at least mid-winter. The SOI was -3.95 today. The preliminary Arctic Oscillation (AO) was -0.264 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 November (1991-2020 normal). November will likely finish with a mean temperature near 47.2° (0.8° below normal). Supplemental Information: The projected mean would be 0.5° below the 1981-2010 normal monthly value.

As of 1 pm CST, Chicago (3.2") and Rockford (3.2") had set new daily snowfall records for November 29. Chicago's old mark of 3.0" was set in 1942. Rockford's old record of 3.0" was set in 1925. Upstream, parts of Iowa had seen 12" of snow.

I'm in briefly. I checked. Here are the December composites (1980-2024) for EPO+/PNA+/AO-/NAO- 500 mb Height Anomalies: Temperature Anomalies: Precipitation Rate: n=121 dates I suspect that there's a lot of variability, though.

I will check when I get home this evening.

As of 7 am, Chicago had picked up 0.5" of snow. Rockford had received 1.0". The highest amounts were at Chatsworth (3.0") and Melvin (2.0").

Parts of the region saw some heavier snow showers yesterday. Binghamton wound up picking up 1.6". Even heavier snow fell in some of the lake effect areas. Syracuse picked up 10.3" of snow, breaking the daily record of 8.8" from 1958.

The snow is sticking in Chicago. Courtesy of EarthCam:

Central Park has recorded its first freeze of the 2025-2026 season. The 1991-2020 normal first date is November 21. The 1961-1990 baseline was November 11. Last winter's first freeze occurred on November 30.