donsutherland1

I also used Bufkit. Its numbers for EWR were absurdly low. One can get a good picture of the snow growth and insight into ratios from its soundings. The focus for me was the NYC region given the subforum involved. The NAM did not do well in this subforum. I don’t always disregard it, but in this case I did. It was an outlier even against the vast majority of individual EPS and GEFS ensemble members. That’s what led me to dismiss it. It is quite rare where the ensembles don’t capture the cluster of reasonable solutions, one of which ultimately verifies. The GFS was overdone. For several days, it was clear that the NYC area was in line for a 3”-6”/4”-8” snowfall regardless of the earlier RRFS A runs and the NAM’s solutions. The only real drama was for areas south and west of NYC and areas in parts of New England.

On Pivotal, the numbers don't count sleet. On Tropical Tidbits, they do, but sleet is treated the same as snowfall, which inflates the totals. Both approaches lead to inaccuracy, since snowfall figures are the sum of snow and sleet.

Here you go:

New York City's largest snowstorm since January 28-29, 2022 has now departed. Even as precipitation dried up for several hours last evening, Central Park still wound up with 4.3" of snow while JFK Airport, LaGuardia Airport, and Newark all saw 4" or more of snow. Many parts of southwestern Connecticut and Long Island saw 6" or more. Tomorrow will turn somewhat milder as a storm heads for the Great Lakes. Showers and possibly periods of rain will develop late tomorrow and continue into early Monday. The temperature will likely reach the upper 40s to perhaps lower 50s on Monday before colder air moves in behind the departing system. The remainder of December will see cooler than normal days. Below normal temperatures will continue into at least the middle of the first week of January. Some flurries or snow showers are possible late on January 1 into January 2. December 2025 will very likely finish with a maximum monthly temperature below 60° in New York City. 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 -0.6°C and the Region 3.4 anomaly was -0.8°C for the week centered around December 17. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.40°C and the ENSO Region 3.4 anomaly has averaged -0.68°C. La Niña conditions will likely continue through at least mid-winter. The SOI was +14.69 today. The preliminary Arctic Oscillation (AO) was -1.006 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.

Against the NWS? I will run them when I get back in this evening. This wasn’t the NWS’s finest forecast.

1917 also had a mean temperature of 25.0° for December Corrected Table: Note: The initial table was constructed from summing daily snowfall amounts. Not all daily amounts are in the NYC climate record. Thus, doing so understates the monthly figures. Here's the correct table using the monthly figures.

Yes, the La Niña cases were snowier.

January records for the New York City area:

With preliminary PNA values of -1.000 or below both yesterday and today, the snowstorm that just brought 4.3" to Central Park could become New York City's largest December snowfall with PNA values of -1.000 or below for all days during which the snow fell.

December 2025 will finish with a mean temperature below 35.0°C (coldest since 2010) and more than 6" of monthly snowfall. Below is how January fared in terms of snowfall following cold and snowy Decembers.

As forecasting accuracy requires, among other things, an objective assessment of the guidance, I've expanded the comparison of the 12/26 18z NAM and 12/26 18z HRRR. The major point of contention had been whether the NAM was providing a realistic forecast for the New York City area. It did not fare well. But what over a larger area? Again, the HRRR outperformed the NAM, but its forecasting edge was less decisive. The HRRR was better in assessing where the 4" or above snows would fall from New York City southward. The NAM confined such snows to the north and east of New York City. However, the HRRR was too aggressive in pushing 2"+ snows past Allentown and into Philadelphia. The HRRR also did better in such locations as Albany and Boston. 12/26 18z NAM: 12/26 18z HRRR: Outcomes for 12 Cities:

January 29, 2022.

The streak without a 4" or above snowstorm ended; the streak with less than 4" daily snowfall continues.

I believe it's a good measurement. Every site in Brooklyn, Queens, Manhattan, and the Bronx listed on the NWS PNS had 3" or more. JFK, LGA, and NYC all had somewhat over 4".

Five photos from this morning.