bluewave

Coldest December day in 2 years. But not quite as cold as 2022. The timing was really close right before Christmas both years. 12-22-24…21/15….-19.0 12-24-22….15/7…..-25.9

You can see the ripple effect it having on the modeling going forward. The extended EPS runs from a week ago had stronger Pacific blocking and weaker Atlantic blocking. Now the Atlantic blocking is forecast to be stronger January 6th to 13th and the Pacific a little weaker. Notice the narrower ridge over Western North America and stronger and more expansive from Eastern Canada through Iceland. New EPS weekly run for January 6th to 13th Old run

NYC briefly got down to 3° in February 2023 but it was in a sea of warmth. Climatological Data for NY CITY CENTRAL PARK, NY - February 2023 Click column heading to sort ascending, click again to sort descending. Sum 1360 942 - - 665 0 1.28 2.2 - Average 48.6 33.6 41.1 5.2 - - - - 0.1 Normal 42.2 29.5 35.9 - 816 0 3.19 10.1 2023-02-01 38 26 32.0 -1.7 33 0 0.02 0.4 T 2023-02-02 40 29 34.5 0.7 30 0 0.00 0.0 0 2023-02-03 35 11 23.0 -10.9 42 0 0.00 0.0 0 2023-02-04 27 3 15.0 -19.0 50 0 0.00 0.0 0 2023-02-05 49 27 38.0 3.8 27 0 0.00 0.0 0 2023-02-06 52 34 43.0 8.7 22 0 0.00 0.0 0 2023-02-07 43 30 36.5 2.1 28 0 0.02 0.0 0 2023-02-08 53 39 46.0 11.4 19 0 T 0.0 0 2023-02-09 55 42 48.5 13.7 16 0 0.00 0.0 0 2023-02-10 61 45 53.0 18.1 12 0 0.00 0.0 0 2023-02-11 46 36 41.0 5.9 24 0 0.00 0.0 0 2023-02-12 48 38 43.0 7.7 22 0 0.01 0.0 0 2023-02-13 57 41 49.0 13.6 16 0 0.00 0.0 0 2023-02-14 54 40 47.0 11.4 18 0 0.00 0.0 0 2023-02-15 67 47 57.0 21.2 8 0 0.00 0.0 0 2023-02-16 70 56 63.0 27.0 2 0 0.07 0.0 0 2023-02-17 61 32 46.5 10.3 18 0 0.18 T 0 2023-02-18 43 27 35.0 -1.4 30 0 0.00 0.0 0 2023-02-19 50 37 43.5 6.9 21 0 0.00 0.0 0 2023-02-20 61 47 54.0 17.2 11 0 0.00 0.0 0 2023-02-21 50 37 43.5 6.5 21 0 0.27 0.0 0 2023-02-22 44 37 40.5 3.3 24 0 0.14 T 0 2023-02-23 44 38 41.0 3.6 24 0 0.02 0.0 0 2023-02-24 45 25 35.0 -2.6 30 0 0.00 0.0 0 2023-02-25 33 23 28.0 -9.9 37 0 T T 0 2023-02-26 50 30 40.0 1.9 25 0 0.00 0.0 0 2023-02-27 46 33 39.5 1.2 25 0 0.21 0.9 0 2023-02-28 38 32 35.0 -3.5 30 0 0.34 0.9 2

The biggest shift we have seen in recent days modeling is the much stronger 500 mb blocking forecast east of Hudson Bay. This feature wasn’t showing up on the older runs. You have to wonder if the record warmth that Hudson Bay absorbed during the summer leading to the current delayed free up is playing a role. A +500 meter anomaly would be one of the strongest on record for this time of year. Even before the record warmth for next week, the Hudson Bay Area has been much warmer than normal this month. https://nsidc.org/sea-ice-today/analyses/sluggish-freeze-warming-north

Yeah, November 2018 had impressive snow and cold for so early in the season. It was the 5th earliest date that NYC dropped under 20°. While the winter still averaged warmer than normal, NYC almost made it to 0° in late January. Frost/Freeze Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. 1933 03-11 (1933) 16 11-16 (1933) 17 249 1924 02-24 (1924) 14 11-17 (1924) 19 266 1936 03-07 (1936) 17 11-18 (1936) 18 255 1879 03-01 (1879) 18 11-21 (1879) 16 264 1987 03-11 (1987) 16 11-21 (1987) 18 254 1880 03-25 (1880) 14 11-22 (1880) 13 241 2018 02-03 (2018) 16 11-22 (2018) 17 291 1888 03-25 (1888) 16 11-23 (1888) 17 242 1938 03-04 (1938) 9 11-25 (1938) 19 265 1932 03-16 (1932) 19 11-26 (1932) 19 254 1903 02-21 (1903) 19 11-27 (1903) 19 278 1917 02-13 (1917) -0 11-27 (1917) 19 286 1871 02-23 (1871) 15 11-28 (1871) 16 277 1890 03-09 (1890) 18 11-28 (1890) 19 263 1901 03-07 (1901) 16 11-28 (1901) 19 265 1930 03-03 (1930) 18 11-28 (1930) 15 269 1872 03-22 (1872) 17 11-29 (1872) 15 251 1875 03-23 (1875) 13 11-29 (1875) 14 250 1891 03-17 (1891) 19 11-29 (1891) 17 256 1929 03-10 (1929) 12 11-29 (1929) 18 263 1955 03-08 (1955) 19 11-29 (1955) 16 265 1876 03-20 (1876) 15 11-30 (1876) 19 254 1887 03-30 (1887) 16 11-30 (1887) 17 244 1958 02-19 (1958) 12 11-30 (1958) 18 283 1976 03-18 (1976) 19 11-30 (1976) 17 256 NY WEST NYACK 1.3 WSW CoCoRaHS 6.7 NJ MAPLEWOOD TWP 0.9 SE CoCoRaHS 6.5 NJ WESTFIELD 0.6 NE CoCoRaHS 6.5 NJ OAKLAND 0.9 SSE CoCoRaHS 6.5 NJ HAWTHORNE 1.0 SSE CoCoRaHS 6.5 NY PEEKSKILL 0.4 N CoCoRaHS 6.5 CT WESTBROOK CENTER 1.5 NE CoCoRaHS 6.5 CT MADISON CENTER 4.1 N CoCoRaHS 6.5 CT NAUGATUCK 1.7 NNE CoCoRaHS 6.5 NJ NEWARK LIBERTY INTL AP WBAN 6.4 NY NY CITY CENTRAL PARK WBAN 6.4 CT NEW CANAAN 1.9 ENE CoCoRaHS 6.4 CT MADISON CENTER 1.6 W CoCoRaHS 6.4 CT MONROE 0.1 SE CoCoRaHS 6.3 NJ HAWTHORNE 0.4 S CoCoRaHS 6.2 NY ARMONK 0.4 E CoCoRaHS 6.2 NJ TETERBORO AIRPORT WBAN 6.0 NJ NORTH ARLINGTON 0.7 WNW CoCoRaHS 6.0 NJ WAYNE TWP 0.8 SSW CoCoRaHS 6.0 NJ MONTCLAIR 0.7 N CoCoRaHS 6.0 CT NORWALK 2.9 NNW CoCoRaHS 6.0 CT HIGGANUM 0.7 N CoCoRaHS 6.0 CT MYSTIC 0.9 W CoCoRaHS 6.0 CT NORWICH 2.5 NNE CoCoRaHS 6.0 NJ HARRISON COOP 5.8 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 5.8 CT RIDGEFIELD 1.9 SSE CoCoRaHS 5.8 NJ NEW PROVIDENCE 0.8 ESE CoCoRaHS 5.5 NY BRIGHTWATERS 0.7 NNW CoCoRaHS 5.5 CT DARIEN 2.8 NW CoCoRaHS 5.5 CT DURHAM 1.2 W CoCoRaHS 5.5 NY SYOSSET 2.0 SSW CoCoRaHS 5.4 CT PAWCATUCK 1.8 SSE CoCoRaHS 5.2 CT IVORYTON 0.9 WSW CoCoRaHS 5.1 NJ CANOE BROOK COOP 5.0 NJ WANAQUE RAYMOND DAM COOP 5.0 NY WANTAGH 0.3 ESE CoCoRaHS 5.0 CT STAMFORD 5 N COOP 5.0 NY NESCONSET 1.4 SSW CoCoRaHS 5.0 CT MONROE 0.8 W CoCoRaHS 5.0 CT KILLINGWORTH 2.6 ESE CoCoRaHS 5.0 CT WALLINGFORD CENTER 3.3 NNW CoCoRaHS 5.0 CT GROTON COOP 5.0 CT NEW LONDON 1.0 NNW CoCoRaHS 5.0 NY MIDDLE VILLAGE 0.5 SW CoCoRaHS 4.9 NY JFK INTERNATIONAL AIRPORT WBAN 4.8 NY LAGUARDIA AIRPORT WBAN 4.7 NY UPTON COOP - NWSFO NEW YORK COOP 4.6 NY WANTAGH 1.1 NNE CoCoRaHS 4.5 NJ HARRISON COOP 0 NJ CALDWELL ESSEX COUNTY AP WBAN 0 CT STAMFORD 5 N COOP 0 NY WESTCHESTER CO AP WBAN 0 NY SHRUB OAK COOP 0 NY MOUNT SINAI COOP 1 CT GROTON NEW LONDON AP WBAN 1 CT GROTON COOP 1 NJ NEWARK LIBERTY INTL AP WBAN 2 NJ CANOE BROOK COOP 2 NY NY CITY CENTRAL PARK WBAN 2 NJ TETERBORO AIRPORT WBAN 2 NY FARMINGDALE REPUBLIC AP WBAN 2 CT NEW HAVEN TWEED AP WBAN 2 NY WESTHAMPTON GABRESKI AP WBAN 2 CT NORWICH PUBLIC UTILITY PLANT COOP 2 NY LAGUARDIA AIRPORT WBAN 3 NY JFK INTERNATIONAL AIRPORT WBAN 3 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 3 NY CENTERPORT COOP 3 NY ISLIP-LI MACARTHUR AP WBAN 3 NY MATTITUCK COOP 3 NY BAITING HOLLOW COOP 3 NY UPTON COOP - NWSFO NEW YORK COOP 3 NY ORIENT POINT STATE PARK COOP 3

Yeah, I agree. That’s why my posts often take in regional, national, and global influences to add context. Since the local forecasts are heavily influenced by the larger patterns. Never understood why anyone would want to define the geographic range of this forum so narrowly as to ever state that your obs don’t matter. I appreciate what the people in your area of the forum add to the discussion. I like to think that anyone in the OKX, PHI, BGM, ALB, or even the bordering BOX NWS forecast zones should be able to feel at home in the forum and that their posts add value.

The reason I posted the original map last week was to highlight this very point. It’s a very big news story for North America at any time of the year when even a 1 week pattern is this anomalous. At no point did I mention the term torch for our area. Plus I didn’t even use that term to describe a month like December 2015 that went +13.3° or when we hit 80° in February 2018. I tend to stay away from emotionally charged terms even if they are warranted in cases like those months. In our immediate area I can think of several reasons why it’s pertinent to our discussion. Whether we top out in the 40s or 50s close to New Years isn’t really that important in the larger scene of things. But how much of a lingering effect the pattern has going forward could be critical at least last near and just after the New Years. It could have an influence early on for P-Types near the immediate coast. The pattern will not cool down instantly. The other issue that I highlighted yesterday was how much this will influence the blocking Northeast of Hudson Bay. This is a feature which could potentially work to our advantage for storm tracks once colder air makes it back into the pattern. So it could be a potential plus for us. But the Pacific pattern has still been a net minus for our snowfall. Hopefully, we can get some Atlantic side push back to help out some snowfall points on the board in January.

Yeah, the surface 2mTs have been running warmer than the 850mb Ts due to the very low snow cover extent in NA, warmer Great Lakes, and Hudson Bay still not frozen over yet.

The sample size is reflective of our warmer modern climate. But it even worked most La Niña years during our colder climate from the 1950s to 1980s. My guess is the reason it has worked for over 50 years is that La Ninas still tend to be frontloaded by nature. So if the winter isn’t really big right out of the gates, then it’s tough to make it up on the back half which tends to be warmer and less snowy than the front half. The 83-84 and 84-85 winter were probably similar due to how cold that era was in the U.S. same for 71-72 and 73-74. But outside those years the relationship was pretty reliable. 88-89…Dec…0.3….season…8.1 85-86…Dec….0.9…season…13.0 84-85…Dec….5.5…season…24.1 83-84…Dec….1.6….season…25.4 75-76…Dec…..2.3…season…17.3 74-75…Dec…..0.1….season…13.0 73-74…Dec…..2.8…season….23.5 71-72…Dec……T……season….22.9 70-71…Dec……2.4…season….15.5 66-67…Dec…..9.1…..season….51.5 64-65….Dec….3.1…..season….24.4 55-56….Dec….3.3…..season….33.5 54-55….Dec….0.1……season….11.5 49-50….Dec…1.3…….season…14.0

NYC should see its first below 20° readings of season next few days that which is earlier than the 12-29 average first date of the last decade. Frost/Freeze Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending first below 20° temperature Minimum 01-20 (2024) 11-22 (2018) 286 Mean 02-18 12-29 310 2024 01-20 (2024) 18 - - - 2023 02-04 (2023) 3 01-17 (2024) 17 346 2022 02-15 (2022) 16 12-23 (2022) 8 310 2021 02-08 (2021) 17 01-04 (2022) 19 329 2020 02-15 (2020) 14 01-29 (2021) 14 348 2019 03-07 (2019) 18 12-19 (2019) 16 286 2018 02-03 (2018) 16 11-22 (2018) 17 291 2017 03-12 (2017) 19 12-27 (2017) 17 289 2016 02-15 (2016) 13 12-15 (2016) 19 303 2015 03-07 (2015) 18 01-04 (2016) 14 302 2014 03-13 (2014) 18 01-06 (2015) 19 298

We didn’t get the great December snowfall response around NYC Metro like we got from past +PNA La Ninas in December 1995, 2000, 2005, 2017, and 2020. The Pacific Jet was much stronger this time around and the Atlantic side blocking was also much weaker. So it was a warmer and less snowy outcome than those years. Hopefully, we can at least put together a 4”+ event in early to mid-January in NYC. I know people get excited when they see cold on the maps since it has been a rarity recently, but there are many that would rather have snow to go along with the cold. So cold temperatures plus snow would make many happy in early to mid-January.

Models have been underestimating the 500mb heights near Hudson Bay all month. So that open water could be playing a role. Notice how the biggest model error recently has been underestimating the forecast ridge there next week. Could approach record levels for this time of year. New run Old run Possible record 500mb heights for this time of year

The blocking with the record warmth around Hudson Bay has exceeded earlier model forecasts. Models are forecasting record 500 mb heights there later in the month. So plenty of easterly flow here last week of December with the warmer mins driving the late month departures.That ridge is the feature to watch into January as it could help NYC break its under 4” snowfall losing streak.

While the global temperatures have shown a slight cooling relative to past El Niños, the actual levels are still far beyond what has happened before the last few years.

While the actual SSTs have been on the weaker side until the recent drop, the atmospheric La Niña response through the EQSOI and OLR has been similar to much stronger La Ninas. https://www.climate.gov/news-features/blogs/enso/december-2024-enso-update-party-time-excellent

Many of the statistical relationships we find are just markers for underlying weather patterns that exist.

I don’t t think that’s how it actually works. December La Niña snowfall probably acts as more of a marker of what the pattern is able to produce. It’s not a December snowfall causing later seasonal snowfall relationship.That being said, we have still had some nice snowstorms following Decembers in NYC with under 3” back to 1991. Like in 99-00, 07-08, and 21-22. The one early snowfall indicator which has worked for every La Niña winter in NYC going back to the 95-96 has been the December La Niña snowfall. Years with 3 or more inches December have gone on to above normal seasonal snowfall. Every December with under 3” has had a below average snowfall season. This is why December is so important with La Ninas around NYC. 22-23….Dec snow…..T……season….2.3 21-22…..Dec snow….0.2…season…..17.9 20-21…..Dec snow….10.5…season…38.6 17-18……Dec snow….7.7…..season…40.9 16-17…….Dec snow…3.2…..season…30.2 11-12…….Dec snow….0…….season….7.4 10-11…….Dec snow….20.1….season….61.9 08-09…..Dec snow….6.0……season….27.6 07-08…..Dec snow…..2.9…..season….11.9 05-06…..Dec snow…..9.7…….season…40.0 00-01……Dec snow….13.4……season….35.0 99-00…..Dec snow…..T……….season….16.3 98-99…..Dec snow…..2.0……..season….12.7 95-96…..Dec snow…..11.5……..season….75.6

This winter will be a big win in my book if NYC can end the under 4” daily snowfall streak and not surpass 1932. Number of Consecutive Days Snowfall < 4 for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 1394 1932-12-16 2 1063 1952-01-27 3 1056 2024-12-20 4 1051 1963-12-22

Hopefully, we can maximize any window we get in early to mid-January.

The biggest uncertainty going forward is how long we will be able to sustain the +PNA. Past December La Niña mismatches generally saw the +PNA reverse at some point in January. These were followed mostly by -PNA Februaries. But if there are other factors behind this +PNA that we haven’t detected, then not sure if we follow past events until we get more model data and verification further into the winter. The EPS weeklies are trying to show this shift in January. But not sure if they are just defaulting to La Niña climo. It’s possible that we still follow the La Niña progression even since this one was so weak. It will be interesting to see how things turn out.

January 2000 stands out as even more impressive a miss especially down in the Carolinas. Since many places that got the heavy snow didn’t even have a storm in the forecast the day before. I don’t think they ever figured out what happened with the models in that one.

Not really in terms of amounts since it was still within .2 spread. This happens all the time with rain. There is no way to narrow that margin down just because the precipitation is frozen rather than liquid. This was still good forecast. January 2015 was a significant model miss for snowfall here. Our greatest recent model error for snow was January 2000 when the storm was forecast to stay offshore and we got 6”+. They still may not know what lead to that model error. Back in the 1970s and 1980s it was more common for models to completely miss storm events. Jan 78 featured a NOAA weather radio forecast of rain heavy at times. Then the next morning we had 15” of snow on the ground. I believe February 1980 had forecasts for 3-6” and the storm missed to our south with nothing here. So while modeling has come a long way since then, a 0.2 error margin may be tough to overcome.

The difference between 0.1 and 2.0 is essentially noise as far as these models are concerned. All through the year we get rainfall events within this margin. But people only notice since it’s snow.

.5 of an inch here just east of HVN.

While it generally means below average seasonal snows, there have still been nice snowstorms following such Decembers. That’s why I am hoping we can maximize the potential January -AO +PNA window. We have seen decent snows following under 3” Decembers in January 2000 and February 2008 to name a few.