bluewave

If we had slightly weaker blocking in 09-10, then NYC could have challenged 95-96. During 10-11 we had over 60” at Newark from 12-26 to 1-27. But the pattern quickly reversed on February putting 95-96 out of reach. I am really grateful that I got to experience 10-11 as my last full winter living in Long Beach.

NYC and LGA continue their record under 4” daily streak while BOS moves into 2nd place for longest daily streak under 6”. Philly is getting closer to their longest daily under 5” streak. DC is currently at their 3rd longest run with no daily 12” amounts. State College is only a few weeks away from their new longest daily under 6” streak. Number of Consecutive Days Snowfall < 4 for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 1405 0 2025-12-04 2 1394 0 1932-12-16 3 1063 0 1952-01-27 4 1051 0 1963-12-22 5 794 0 1956-03-15 Number of Consecutive Days Snowfall < 4 for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. 1 1405 1 2025-12-04 2 1051 0 1963-12-22 3 761 0 2020-12-15 4 746 0 1952-02-29 5 744 0 1981-03-04 Number of Consecutive Days Snowfall < 6 for Boston Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 1772 0 1992-12-11 2 1378 0 2025-12-04 3 1373 0 1981-12-05 4 1369 0 1987-12-28 5 1054 0 1909-12-25 Number of Consecutive Days Snowfall < 5 for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 1440 0 1987-01-21 2 1438 0 2000-01-24 3 1433 0 1896-12-15 4 1423 0 1970-12-31 5 1409 0 1945-01-15 6 1405 0 2025-12-04 Number of Consecutive Days Snowfall < 12 for Washington Area, DC (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 8383 0 1922-01-27 2 8043 0 1958-02-14 3 5829 0 2025-12-04 4 5122 0 1936-02-06 5 4768 0 1979-02-18 Number of Consecutive Days Snowfall < 6 for STATE COLLEGE, PA Click column heading to sort ascending, click again to sort descending. 1 1434 0 1990-12-27 2 1418 1 2025-12-05 3 997 0 2009-12-08 4 835 4 1932-03-27 5 816 4 1956-02-01

Some degree of moderation in the East after the 16th fits December climatology since 1991. But exactly how much of a relaxation remains to be seen. A 10 to 15 day lag following the current AAM reversal would indicate some degree of moderation by near or after the 20th.

It’s interesting that the rapid warming of the North Pacific could be contributing to the 2012 minimum not being surpassed due to a weakening of the AD since then. Article Open access Published: 18 November 2025 Decelerated Arctic Sea ice loss triggered by accelerated North Pacific warming over the past decade https://www.nature.com/articles/s43247-025-02882-1 This study offers fresh insights into the mechanisms behind the decelerating decline of Arctic sea ice from 2007 to 2024. We demonstrate that an SST trend in the North Pacific excites a Rossby wavetrain that propagates into the Arctic, driving a downward trend in the summertime Arctic Dipole (AD) index (−0.1 year⁻¹, p < 0.02). This shift induces anomalous surface wind patterns and colder air temperatures, fostering sea ice increases in the central Arctic Ocean near 180 °W (region 1) and the Canadian Arctic Archipelago (region 2), with trends of 0.4% year−¹ and 1.1% year−¹, respectively. These regional gains offset losses elsewhere, contributing to the observed slowdown in overall Arctic sea ice decline. Previous studies have documented the upward trend in September Arctic sea ice extent since 200734,35,36, yet its underlying cause remains unresolved. Our findings complement prior research on sea ice outflow11 and ocean heat transport13, while not diminishing their importance. For instance, southerly wind anomalies linked to increased sea ice in regions 1 and 2 (Fig. 2c, d) may reduce outflow through the Fram Strait, while northerly winds near the North Pole transport ice into region 1, enhancing its growth. Contrary to reports of an increasing AD index over the 2007–2024 period relative to the 1992–2006 period13, we attribute the deceleration to a declining summertime AD index, driven by North Pacific SST warming, which agrees with previous studies37,38. This warming, potentially tied to rising greenhouse gas emissions, merits further investigation to pinpoint its origins.

Colder start to December fits within the long term trend since 1991. NYC average temperatures have only risen +0.7° in NYC from December 1st to 16th. But the December 17th to 31st average temperatures over the same period have increased by +4.6°. This matches the streak of 55°+ days every year since 2011 around NYC from the 17th to 25th. So my guess is that the warmest departures we see this month will occur after the 16th. Time Series Summary for NY CITY CENTRAL PARK, NY highest temperature December 17th through 25th since 2011 Click column heading to sort ascending, click again to sort descending. 2024-12-25 59 0 2023-12-25 62 0 2022-12-25 58 0 2021-12-25 60 0 2020-12-25 61 0 2019-12-25 57 0 2018-12-25 61 0 2017-12-25 55 0 2016-12-25 58 0 2015-12-25 72 0 2014-12-25 62 0 2013-12-25 71 0 2012-12-25 56 0 2011-12-25 62 0

Yeah, the number of 1” snowcover days at ISP the last 7 seasons has been roughly half that of the colder and snowier 70s and 80s at 11 days vs 21 days. Monthly Number of Days Snow Depth >= 1 for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Mean 0 0 2 3 6 0 0 11 2024-2025 0 0 1 7 5 0 0 13 2023-2024 0 0 0 5 6 0 0 11 2022-2023 0 0 0 0 1 1 0 2 2021-2022 0 0 0 6 9 0 0 15 2020-2021 0 0 7 0 23 0 0 30 2019-2020 0 0 3 0 0 0 0 3 2018-2019 0 0 0 1 1 2 0 4 Monthly Number of Days Snow Depth >= 1 for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Mean 0 0 2 10 6 2 0 21 1988-1989 0 0 7 2 3 3 0 15 1987-1988 0 1 3 15 0 2 0 21 1986-1987 0 0 1 12 10 1 0 24 1985-1986 0 0 3 4 13 0 0 20 1984-1985 0 0 1 13 10 0 0 24 1983-1984 0 0 1 15 0 6 0 22 1982-1983 0 0 4 3 8 0 1 16 1981-1982 0 0 0 19 0 0 4 23 1980-1981 0 0 1 22 0 2 0 25 1979-1980 0 0 1 3 1 1 0 6 1978-1979 0 0 0 3 14 0 0 17 1977-1978 0 0 0 13 22 18 0 53 1976-1977 0 0 6 23 7 0 0 36 1975-1976 0 0 5 8 7 2 0 22 1974-1975 0 0 0 1 5 1 0 7 1973-1974 0 0 0 14 10 1 0 25 1972-1973 0 0 0 0 2 0 0 2 1971-1972 0 0 0 3 8 1 0 12 1970-1971 0 0 5 11 1 0 1 18 1969-1970 0 0 7 19 6 2 0 34

Earliest 20° reading in NYC since the 2007-2008 La Niña. But the snowfall outcome was lower this time around. We finally got some cold into Eastern Canada which has been lacking in recent years. Dec 5, 6:51 am 21 2 43 11 ENE 9 10.00 CLR 1027.20 30.18 30.35 24 20 Climatological Data for NY CITY CENTRAL PARK, NY - December 2007 Click column heading to sort ascending, click again to sort descending. 2007-12-01 38 25 31.5 -11.7 33 0 0.00 0.0 0 2007-12-02 36 20 28.0 -14.9 37 0 0.33 1.4 0 2007-12-03 47 32 39.5 -3.1 25 0 0.31 T 0 2007-12-04 34 28 31.0 -11.3 34 0 0.00 0.0 0 2007-12-05 33 28 30.5 -11.5 34 0 0.02 0.3 0 2007-12-06 33 21 27.0 -14.7 38 0 0.00 0.0 T 2007-12-07 35 28 31.5 -9.9 33 0 T T 0

This source shows the strongest tendency decline in months. Makes sense since we are seeing a big reversal from all the +PNA warmth last December which was a mismatch to the La Niña background state. The more robust La Niña background states can feature strong gradient patterns in December with a cold Canada and Northern Tier. Especially when the pattern matches up so closely with the December MJO 6 composite. The forcing in the MJO 6 region is driving the U.S. Western ridge and colder Eastern trough pattern which will dominate December 1st through the 16th. The stronger blocking near Greenland is a result of the other area of the forcing in the Western Hemisphere and the recent +AAM spike in late November. So a bit of a hybrid composite with the split forcing. Split forcing pattern

Strengthening La Niña background state with the falling AAM heading into mid-December leading to the very amplified Aleutian Ridge and -PNA trough in Western Canada.

During the 1970s and 1980s NYC averaged around 6.2”more of snow than we have over the last 7 seasons and ISP 8.0” more. We didn’t have to rely exclusively on KU NESIS events back then like we do now to get over 20” of snow on the season. We used to get snowy clippers and SWFEs. Plus the colder climate allowed for heavier snows on the front end before mixing became an issue. We never experienced a climate before that was so challenging to get over 20” from EWR to NYC and ISP. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 0.0 0.9 2.3 3.7 6.4 1.6 T 14.9 2024-2025 0.0 0.0 2.8 3.0 7.1 0.0 0.0 12.9 2023-2024 0.0 T T 2.3 5.2 T 0.0 7.5 2022-2023 0.0 0.0 T T 2.2 0.1 0.0 2.3 2021-2022 0.0 T 0.2 15.3 2.0 0.4 0.0 17.9 2020-2021 0.0 0.0 10.5 2.1 26.0 T 0.0 38.6 2019-2020 0.0 0.0 2.5 2.3 T T T 4.8 2018-2019 0.0 6.4 T 1.1 2.6 10.4 0.0 20.5 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean T 0.2 2.2 7.9 7.6 2.7 0.6 21.1 1988-1989 0.0 0.0 0.3 5.0 0.3 2.5 0.0 8.1 1987-1988 0.0 1.1 2.6 13.9 1.5 T 0.0 19.1 1986-1987 0.0 T 0.6 13.6 7.0 1.9 0.0 23.1 1985-1986 0.0 T 0.9 2.2 9.9 T T 13.0 1984-1985 0.0 T 5.5 8.4 10.0 0.2 T 24.1 1983-1984 0.0 T 1.6 11.7 0.2 11.9 0.0 25.4 1982-1983 0.0 0.0 3.0 1.9 21.5 T 0.8 27.2 1981-1982 0.0 0.0 2.1 11.8 0.4 0.7 9.6 24.6 1980-1981 0.0 T 2.8 8.0 T 8.6 0.0 19.4 1979-1980 T 0.0 3.5 2.0 2.7 4.6 T 12.8 1978-1979 0.0 2.2 0.5 6.6 20.1 T T 29.4 1977-1978 0.0 0.2 0.4 20.3 23.0 6.8 T 50.7 1976-1977 0.0 T 5.1 13.0 5.8 0.6 T 24.5 1975-1976 0.0 T 2.3 5.6 5.0 4.4 T 17.3 1974-1975 0.0 0.1 0.1 2.0 10.6 0.3 T 13.1 1973-1974 0.0 0.0 2.8 7.8 9.4 3.2 0.3 23.5 1972-1973 T T T 1.8 0.8 0.2 T 2.8 1971-1972 0.0 T T 2.8 17.8 2.3 T 22.9 1970-1971 0.0 0.0 2.4 11.4 T 1.3 0.4 15.5 1969-1970 0.0 T 6.8 8.4 6.4 4.0 T 25.6 Monthly Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Mean T 0.6 2.1 6.0 7.1 1.0 T 16.8 2024-2025 0.0 0.0 2.1 2.7 6.9 0.0 0.0 11.7 2023-2024 0.0 T T 3.1 7.8 0.0 0.0 10.9 2022-2023 0.0 0.0 0.4 T 3.0 1.6 0.0 5.0 2021-2022 0.0 T 0.3 31.8 3.3 1.6 0.0 37.0 2020-2021 T 0.0 7.5 1.1 24.9 T T 33.5 2019-2020 0.0 0.1 4.2 2.5 0.0 T T 6.8 2018-2019 0.0 4.3 T 0.9 3.5 4.1 T 12.8 Monthly Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Mean T 0.3 3.3 8.8 8.5 3.0 1.0 24.8 1988-1989 0.0 0.0 10.4 4.4 1.2 3.0 T 19.0 1987-1988 0.0 1.1 4.2 10.7 0.1 3.4 0.0 19.5 1986-1987 0.0 T 3.4 8.8 8.6 1.7 0.0 22.5 1985-1986 0.0 T 2.1 2.6 10.4 0.1 T 15.2 1984-1985 0.0 T 4.7 13.5 8.7 T T 26.9 1983-1984 0.0 T 2.6 11.9 T 13.0 0.0 27.5 1982-1983 0.0 0.0 3.2 1.5 26.1 T 1.1 31.9 1981-1982 0.0 0.0 1.0 18.1 0.3 T 16.0 35.4 1980-1981 0.0 T 0.5 13.2 T 7.1 0.0 20.8 1979-1980 T 0.0 1.5 4.0 1.5 2.0 0.0 9.0 1978-1979 0.0 4.0 T 6.9 17.2 T T 28.1 1977-1978 0.0 0.8 0.2 27.7 28.9 10.4 T 68.0 1976-1977 0.0 T 6.2 11.2 6.6 4.0 0.0 28.0 1975-1976 0.0 T 11.0 7.8 7.5 3.9 0.0 30.2 1974-1975 0.0 0.5 T 1.8 11.0 1.2 T 14.5 1973-1974 0.0 0.0 T 9.0 17.0 8.0 T 34.0 1972-1973 T 0.0 T 1.5 3.0 T T 4.5 1971-1972 0.0 T T 2.1 12.5 1.0 T 15.6 1970-1971 0.0 0.0 2.1 11.3 2.0 1.0 2.5 18.9 1969-1970 0.0 T 12.0 7.0 7.0 1.0 T 27.0

The fast Pacific flow and lack of blocking didn’t allow the cold high to stay anchored over New England. The WAR flexed just enough so the thermal gradient got pushed north of NYC. So these features negated the usual colder influence we see with lows tracking south of Long Island. Plus the low was strung out on a N-S axis without enough deepening near the benchmark to allow the cold air to wrap in behind the storm.

Continuation of the Great Lakes cutter, I 78 to I-84 hugger rain-snow line, and suppressed Southern Stream storm tracks since 2018-2019. Very persistent over-amped Northern Stream of the Pacific Jet. Makes you wonder what it’s going to take to shift this pattern?

Yeah, we have seen a record expansion of the Aleutian ridge since 1980. Some years the axis is further west near the Aleutians. Other years the ridge is displaced further east over the NE PAC and or Canada.

I am glad that my early October indicator pointing to a more -PNA worked out again this year. Was expecting a decline in the PNA from the record levels last year. But we always have to wait until December in order to get the specific value. This is why Canada into the Northern Tier are so much colder than last December.

That smaller part is a representative subset of the wider Atlantic part of the Arctic which is also at record lows for the date. You can see record daily lows extending over to Svalbard on the Atlantic side of the Arctic. Due to geography and season, the September records have been more Pacific focused like in September 2012. So the record lows on the Atlantic side caused the entire Arctic to have a record low Jaxa extent on December 2nd. The extent is the lowest on record for the date at -425K below the previous record set in 2016. Winter records are usually more on the Atlantic side over the years since it’s easier to have open water extending into the Barents and Kara seas due to Atlantification of the Arctic. There is a much narrower opening to the Arctic near Alaska so it’s easier for the area north of Alaska to freeze over by this time of year. Wider Arctic low matches regional lows across the Arctic.