bluewave

There are plenty of things that need to go just right for a location like NYC which has a long term snowfall average around 25” and is so close to the ocean. It’s much easier to get it to snow in Northern Maine which averages over 110”. So this is why snowfall forecasting is so challenging around NYC. It’s no surprise that sometimes even model forecasts issued the day before the event can be significantly off.

The historic winter warmth pattern since December 2015 continues. A record breaking 19 warmer winter months out of the last 25. These were the 3 warmest consecutive winter months for NYC beginning with last Janaury. NYC Dec 23..+5.5 Feb 23…+5.2 Jan 23…+9.8 Dec 22…-0.6 …………..+4.8 Feb 22….+1.4 Jan 22….-3.2 Dec 21….+4.7 ……………..+1.0 Feb 21….-1.7 Jan 21….+1.1 Dec 20…+1.7 …………..+0.4 Feb 20…+4.8 Jan 20….+6.5 Dec 19….+0.8 …………….+4.0 Feb 19….+0.9 Jan 19….-0.1 Dec 18…+2.6 …………….+1.1 Feb 18…+6.7 Jan 18….-0.9 Dec 17…..-2.5 …………….+1.1 Feb 17…..+6.3 Jan 17….+5.4 Dec 16….+0.8 …………….+4.2 Feb 16….+2.4 Jan 16….+1.9 Dec 15….+13.3 …………….+5.9

The last time NYC scored a 6” snowstorm with a deep trough digging into the West was 2-3-14. It’s rare for that set up to actually work for us. As we have seen numerous potentials beyond 5 days since then with a deep trough in the West fall apart once we got to within 72 hrs. That storm in 2014 was much weaker and strung out and was a true thread the needle. More like a SWFE. Just weak enough not to run too far north. But most of the models are really amped with this system. Which leads to concern about a too far north 0z CMC outcome. But if the system were to become weaker in future runs, then suppression would become a concern with the waves so close together in the fast flow.

I didn’t mean to make you sad. It just seems like 2010 to 2018 was the peak snowfall period for our area. But as we saw in 20-21 and Jan 22, we need the Pacific to relax if we want to see memorable snowstorms. My only regret from the 2010-2018 period was missing the Nemo 50 DBZ jackpot zone with 30”-40” and 6-8” per hour rates.

Almost like a grand finale at the end of a fireworks show.

The GEFS has stronger forcing near the Maritime Continent than the GEPS. So that’s probably why it has a more pronounced -PNA.

Yeah, Long Island has been in all or nothing snowfall mode since the early 90s. From the 60s to early 90s average seasons dominated. My guess is that the heightened volatility since the early 90s is related to the warming. At some point going forward the increasing warmth will probably give us a snowfall average closer to the Delmarva and Southern NJ. The good news for the Great Lakes region is that warmer waters and less ice should lead to increases in lake effect snows at several locations.

Even the most anemic winters of the 1950s finished with around 10” of snow or higher and we had 2 years under 5” since 19-20.

Those winters weren’t mild by todays standards. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Season Mean Avg Temperature Missing Count 1 2001-2002 41.5 0 2 2022-2023 41.0 0 - 2015-2016 41.0 0 3 2011-2012 40.5 0 4 1931-1932 40.1 0 5 1997-1998 39.6 0 6 2016-2017 39.3 0 7 2019-2020 39.2 0 8 1990-1991 39.1 0 9 1998-1999 38.6 0 10 1948-1949 38.5 0 11 1889-1890 38.4 0 12 1952-1953 38.1 0 13 1982-1983 37.9 0 - 1936-1937 37.9 0 14 1996-1997 37.8 0 - 1932-1933 37.8 0 15 1949-1950 37.6 2 16 1974-1975 37.5 0 - 1879-1880 37.5 2 17 1953-1954 37.4 0 18 2005-2006 37.3 0 19 1991-1992 37.2 0 - 1951-1952 37.2 2 20 2021-2022 37.1 0 - 1994-1995 37.1 0 - 1912-1913 37.1 0

The first 3 consecutive winter months with top 3 warmest finishes for NYC. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2015 50.8 0 2 2023 44.7 1 3 2001 44.1 0 4 2021 43.8 0 5 1984 43.7 0 6 2006 43.6 0 7 2011 43.3 0 8 1998 43.1 0 9 1982 42.7 0 10 1990 42.6 0 Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Feb Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2018 42.0 0 2 2017 41.6 0 3 2023 41.1 0 4 2012 40.9 0 5 2002 40.6 0 - 1998 40.6 0 - 1984 40.6 0 6 2020 40.1 0 - 1954 40.1 0 7 1997 40.0 0 8 1991 39.9 0 - 1976 39.9 0 9 1990 39.7 0 10 1981 39.3 0 Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Jan Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2023 43.5 0 2 1932 43.2 0 3 1950 41.8 2 4 1990 41.4 0 5 2006 40.9 0 6 1913 40.8 0 7 1933 40.3 0 8 1937 40.2 0 9 1998 40.0 0 10 2002 39.9 0

But even during that stretch NYC didn’t have the challenge of getting an inch or two of snow like today since it was much cooler back then. Number of Consecutive Days Snowfall < 2 for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Run Length Ending Date 1 699 2023-12-29 2 685 1974-01-08 3 521 1919-09-15 4 416 1914-02-13 5 406 1998-03-21 6 386 1992-03-18 - 386 1955-02-01 8 385 1932-12-16 9 377 1972-02-05 10 366 2007-02-13 11 365 1986-02-06

I think the reason the pattern changes since December 2015 have been so dramatic is possibly related to non-linear shifts. Many expect to see linear gradual changes over time. But it appears we have crossed a barrier where the record SSTs in the warmer MJO regions have lead to more of a jump rather than a gradual change. While it remains to be seen how this will play out in the future, I will continue to have an open mind and take a wait and see approach long term until we have more years of data to make a firm conclusion either way. But in the mean time, it has proven to be a useful forecast tool. This paper discusses non-linear shifts but still looks very general and I am not sure if it’s the authors intentions to apply more generally to stuck or repeating weather patterns. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL101499

The only reason I show that is due to the fact that the EPS weeklies now have a trough near the West and a ridge near the Northeast well into January. The EPS weeklies have had a cold bias longer range but the GEFS has been a little better but still too cold.

Yeah, the competing Maritime MJO forces in December actually enhanced the El Niño effect making it much warmer for the US than usual. So instead of the regular vanilla Canadian ridge, we got one of the strongest on record producing one of the warmest Decembers on record. The final composite for December was similar to a MJO 7 Nino composite that locked in due to the near record forcing over the WPAC near 7. Our last El Niño in December 2015 featured more record warmth centered further east due to the MJO 5 pattern getting stuck in place. Now the record westward forcing into the IO is producing more of a La Niña type pattern in January with a -PNA and Southeast ridge developing. The most recent extended GEFS keeps this pattern going well into January. While anything past 2 weeks is uncertain, we have seen these robust -PNAs in recent years last longer than expected.

NYC had fewer freezing or lower days this year than Raleigh, NC. Time Series Summary for NY CITY CENTRAL PARK, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature <= 32 Missing Count 1 2023 28 3 2 2012 38 0 3 1998 39 0 4 2020 41 0 5 1990 47 0 Time Series Summary for Raleigh Area, NC (ThreadEx) - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature <= 32 Missing Count 1 2023 35 3 2 1990 39 0 3 2012 44 0 4 2020 48 0 5 1994 50 0 - 1946 50 0

Pacific Decadal Ociillation.

Nearly all the analogs centered near January 8th are La Niña or -PDO.

Either the standing wave in P2 is so strong, or the base state is more Niña-like so p3 in the RMM forecasts is following the general composite instead of the El Niño one. All the guidance agrees on the big Western trough in early to mid January.

Even during a borderline super El Niño, we still find a way to get a Niña-like pattern in early to mid January.

LGA got close to its first 60/60 year. Time Series Summary for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2016 58.7 0 2 2020 58.6 0 3 2012 58.5 0 - 2006 58.5 0 4 2023 58.4 3 5 2021 58.3 0 Time Series Summary for LAGUARDIA AIRPORT, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Total Precipitation Missing Count 1 2011 65.34 0 2 1983 60.84 0 3 1975 60.79 0 4 2023 59.65 3

We can add December to the list with 3 stations reaching 10.00”+. Monthly Data for December 2023 for Upton NY NWS CWA Click column heading to sort ascending, click again to sort descending. State Name Station Type Total Precipitation CT ANSONIA 1 NE COOP 11.33 NJ WANAQUE RAYMOND DAM COOP 10.67 NJ CHARLOTTEBURG RESERVOIR COOP 10.25

We are going into January with the lowest snow extent on record for North America and the whole Northern Hemisphere. These readings are normal for mid-November. https://www.star.nesdis.noaa.gov/smcd/emb/snow/HTML/snow_extent_monitor.html

The west biased -AO block actually verified stronger and peaked around the 16th. Then we had the historic blizzard when the Pacific became favorable around the 22nd-23rd.

The sensible weather in late December into Janaury along with the forecasts were indicating a big turnaround. Following the low 70s leading up to Christmas, we quickly picked up a T of snow before New Years. Then a short Arctic outbreak with NYC dropping to 11° on Janaury 5th. I remember mentioning how impressive it was to have a+500 meter KB block. Once it built back across the pole, the rest was history. The weeklies started looking great in late December. https://fox12weather.wordpress.com/2015/12/28/ecmwf-monthly-run-10/

MJO 2 with an El Niño isn’t a favorable pattern for us in January. The trough dives into the West and it pumps the ridge over us. That’s why the Jan week 2 forecasts have been correcting warmer. My guess is that the 2nd week may see warmer departures than the first week. Remember the MJO effects can be lagged.