bluewave

The trough is more consolidated near the Four Corners. The GFS forecast sounding is likely underestimating the warming near the coast with such a strong easterly LLJ off the Ocean.

Stronger Southeast ridge this run leading to warmer storm track for the coast. This was expected with the trough in the West. New run Old run

You can see why the GEFS has a deeper trough in the West than the EPS. Much stronger MJO through 4. I know the EPS has issues with convection near the Maritime Continent related to the barrier effect. But this is the most extreme MJO divergence I have ever see between the two models.

If this is as amped as several models show, then a coastal hugger track like the CMC is possible.

First time NYC didn’t drop below 35° between Christmas and New Years. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Lowest Min Temperature Dec 25 to Jan 1 Missing Count 1 2024-01-01 35 0 2 2022-01-01 34 0 - 2016-01-01 34 0 - 1980-01-01 34 0 3 2007-01-01 33 0 - 1941-01-01 33 0 - 1908-01-01 33 0

If that tucked track verifies, then the CMC will be a degree or two warmer. It’s currently running 2° too cold for NYC this morning.

Warmest run of the UKMET so far and even warmer than the CMC.

Interior spots could see more frozen plus an eventual changeover to plain rain with the follow up cutter.

Just 1-2° too warm in an already marginal set up would be an issue. This storm may turn out as a be careful what you wish for if the interior spots get a significant snow. December has seen record rainfall and flooding in the Northeast. There is strong model support for a follow up system which would probably cut to the Lakes. Heavy rains + snowmelt would be really unwanted for interior spots. Even coastal areas could eventually see flooding with more follow up heavy rainstorms.

Concerning how close to us the track is at 144 hrs since amped systems like this often tick further west the closer in we get. Plus we have the cold bias with all the models running too cold this winter days 5-6. Then much of what the Euro shows is a mix along the coast but gets counted as SN in those 10:1 charts.

We would probably need a perfect thread the needle of the storm being not too amped but not too suppressed. Traditionally over amped or suppression have been the two risks with deep trough in the West. Either the trough in the West pumps the ridge near us too much or a low is too close behind this one and it leads to suppression.

The one interesting stat is that NYC avoided a complete shut out even with all the winter months in the calendar year over 40°. So in a much warmer future climate, the chances of not recording at least a T are probably pretty slim. But it does raise the prospect that some day we may see a season or calendar year under 1”. Just hopefully no time soon.

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