bluewave

The one bright spot with near record warm CONUS December patterns is lower heating bills.

It seems like the start of the more hostile Pacific pattern began in December 11. But it didn’t become more widespread through the winters until 18-19. So in the last 13 Decembers including this one, we only had 3 with a favorable enough Pacific for 6”+ snows in NYC. The years were 2013, 2017, and 2020. Allsnow gets credit for calling the December 2020 pattern potential pretty early.

That December 2000 to 2010 record was the first 11 year run with 5 double digit snowfall years since the 1880s. The 1940s were great also with 3 double digit years. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 8.9 8.9 2010 20.1 20.1 2009 12.4 12.4 2008 6.0 6.0 2007 2.9 2.9 2006 0.0 0.0 2005 9.7 9.7 2004 3.0 3.0 2003 19.8 19.8 2002 11.0 11.0 2001 T T 2000 13.4 13.4 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 7.5 7.5 1880 11.5 11.5 1881 1.3 1.3 1882 0.0 0.0 1883 22.6 22.6 1884 10.7 10.7 1885 T T 1886 10.3 10.3 1887 9.0 9.0 1888 T T 1889 6.0 6.0 1890 11.4 11.4 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 8.7 8.7 1940 3.0 3.0 1941 0.3 0.3 1942 8.5 8.5 1943 T T 1944 6.7 6.7 1945 15.6 15.6 1946 1.3 1.3 1947 30.2 30.2 1948 25.3 25.3 1949 1.3 1.3 1950 3.8 3.8

Double digit event on the 19-20th. Data for December 19, 2009 through December 20, 2009 Click column heading to sort ascending, click again to sort descending. State Name Station Type Total Snowfall NY SHOREHAM 1.8 SSE CoCoRaHS 29.0 NY ISLIP-LI MACARTHUR AP WBAN 23.9 NY EAST MORICHES 0.6 WNW CoCoRaHS 23.2 NY RIVERHEAD RESEARCH FARM COOP 20.0 NY JAMESPORT 0.6 SSW CoCoRaHS 20.0 NY BAITING HOLLOW COOP 19.0 NY ISLIP 0.2 NW CoCoRaHS 17.0 NY JFK INTERNATIONAL AIRPORT WBAN 14.5 NY OCEANSIDE COOP 14.2 CT NORWICH PUBLIC UTILITY PLANT COOP 14.0 NY NORTHPORT 1.6 NNE CoCoRaHS 13.8 NY LEVITTOWN 0.2 E CoCoRaHS 13.5 NY FLORAL PARK 0.4 W CoCoRaHS 13.5 NJ NEWARK LIBERTY INTL AP WBAN 11.2 NY CENTERPORT COOP 11.0 NY NY CITY CENTRAL PARK WBAN 10.9 NY MINEOLA COOP 10.2

It’s as if the Boxing Day Blizzard flipped the switch to very little snowfall from December 20th-31st. This has become one of our least snowy 10-11 day periods of winter. The most disruptive Christmas event of the last decade was the flood cutter in 2020 which wiped out the BGM 40” snowpack leading to all the flash flooding. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 20 to Dec 31 Missing Count 2022-12-31 T 0 2021-12-31 0.2 0 2020-12-31 T 0 2019-12-31 T 0 2018-12-31 T 0 2017-12-31 0.7 0 2016-12-31 T 0 2015-12-31 T 0 2014-12-31 T 0 2013-12-31 T 0 2012-12-31 0.4 0 2011-12-31 0.0 0 2010-12-31 20.0 0

Yeah, the warmth from MJO and El Niño induced Pacific Jet extension is going to be around for a while. When you see such a deep trough south of Alaska and strong ridge over Canada it keeps the Pacific Jet aimed at the West Coast. Plus we are going to lose the -AO and -NAO blocking. But this has been par for the course in December in recent years. So expectations have been lowered especially early on during El Niños. https://globalcryospherewatch.org/state_of_cryo/snow/

Whenever Canada gets this warm, the North American snow cover extent goes way down. https://globalcryospherewatch.org/state_of_cryo/snow/

While it’s tough to say exactly how far above +10° the departures finish in Canada, some of the warmth records so far have been pretty impressive.

Same for me. I originally had +2.5 to +5.0 range for the various NYC metro stations. I use a 2.5° scale. -2.5 to -5.0…0 to -2.5…0 to +2.5…+2.5 to 5.0. On my map the +2.5 line is just to our south this month. And the +5.0 is to our NW closer to the Great Lakes. There may also be a 10+ departure region this month in the Upper Midwest near International Falls. Currently +4.5 for EWR….NYC….+4.6…ISP….+4.1.

December during the 1870s and 1880s in NYC were very cold. The 1890s were significantly warmer. I started the groupings on the 1s since that is the first year for each new climate normals period. So December temperatures in NYC since 2011 have been similar to Novembers in the 1870s. NYC Dec Avg Temperature 1871-1880…31.9° 1881-1890…33.8° 1891-1900…36.1° 1901-1910…34.1° 1911-1920…34.8° 1921-1930…35.2° 1931-1940°…36.2° 1941-1950°…35.0° 1951-1960°….36.4° 1961-1970°….35.1° 1971-1980°….37.1° 1981-1990….37.5° 1991-2000…38.3° 2001-2010….37.9° 2011-2020….40.6° Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Nov Season Mean 41.4 41.4 1880 38.9 38.9 1879 42.9 42.9 1878 44.1 44.1 1877 44.2 44.2 1876 45.1 45.1 1875 38.9 38.9 1874 42.8 42.8 1873 37.2 37.2 1872 41.4 41.4 1871 38.8 38.8 Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 40.6 40.6 2020 39.2 39.2 2019 38.3 38.3 2018 40.1 40.1 2017 35.0 35.0 2016 38.3 38.3 2015 50.8 50.8 2014 40.5 40.5 2013 38.5 38.5 2012 41.5 41.5 2011 43.3 43.3

It was the cold in February which allowed the Southeast to cash in. https://www.weather.gov/ilm/Feb1973Snow One of the greatest snowstorms in Southeastern United States history occurred February 9-11, 1973. This storm dropped one to two feet of snow across a region that typically sees only an inch or two of snow per year. New all-time snowfall records were established in a number of locations including Rimini, SC with 24 inches; 18 inches in Darlington, SC; and 16.5 inches in Macon, GA. Snowfall in Wilmington, NC reached 12.5 inches with 7.1 inches recorded in Charleston, SC, both setting all-time records which were broken just 16 years later during the Christmas snowstorm of 1989. Measurable snow fell along the Gulf Coast from Texas to Florida and flurries were reported as far south as Lisbon and Clermont, Florida just outside of Orlando.

Yeah, but some on here won’t consider 50s that big a deal in later December since it’s much cooler than the low 70s reached in 2015 and +33 departure.

They also put out a separate 15 year climate normals but it’s not as widely used as the 30 years. The main challenge of using climate normals in a rapidly warming climate is that it masks the warming. With the new 39.1 average December temperature in NYC, they only need a +3.4 departure to enter the top 10 warmest of December average temperatures. And we hear the sentiment on here that a +3.4 really isn’t anything out of the ordinary since it’s much lower than the +13.3° and 50° December 2015. Plus we have had something like 20-30 top 10 warmest months of the year depending on the local station used to only one top 10 coldest since 2015. 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 2001 44.1 0 3 2021 43.8 0 4 1984 43.7 0 5 2006 43.6 0 6 2011 43.3 0 7 1998 43.1 0 8 1982 42.7 0 9 1990 42.6 0 10 1891 42.5 0

I scanned it very quickly and didn’t realize the data was missing. So the most recent decade at BTV is +5.9 warmer than than their earliest 30 year December average. It would probably be closer to +6.7 warmer if they had a complete record that started around 1870 like the NYC comparison which was in a colder era than the earliest available. Monthly Mean Avg Temperature for Burlington Area, VT (ThreadEx) Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 23.6 23.6 1921 20.3 20.3 1920 25.3 25.3 1919 17.2 17.2 1918 25.5 25.5 1917 12.2 12.2 1916 21.6 21.6 1915 25.1 25.1 1914 21.2 21.2 1913 27.0 27.0 1912 29.0 29.0 1911 31.0 31.0 1910 15.9 15.9 1909 21.3 21.3 1908 21.4 21.4 1907 27.0 27.0 1906 17.2 17.2 1905 28.3 28.3 1904 16.0 16.0 1903 20.7 20.7 1902 22.2 22.2 1901 26.1 26.1 1900 24.8 24.8 1899 30.9 30.9 1898 27.6 27.6 1897 27.3 27.3 1896 23.5 23.5 1895 29.0 29.0 1894 28.3 28.3 1893 22.1 22.1 1892 23.1 23.1 Monthly Mean Avg Temperature for Burlington Area, VT (ThreadEx) Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 29.5 29.5 2022 31.6 31.6 2021 31.8 31.8 2020 31.3 31.3 2019 27.4 27.4 2018 26.8 26.8 2017 22.3 22.3 2016 29.0 29.0 2015 39.2 39.2 2014 30.0 30.0 2013 23.5 23.5 2012 30.8 30.8 2011 30.6 30.6

The last decade has been about 6.6° warmer than the late 1800s in December. So we currently have the same December temperatures that used to be common in Virginia in the late 1800s. Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 34.1 34.1 1900 36.2 36.2 1899 38.1 38.1 1898 35.0 35.0 1897 38.6 38.6 1896 34.4 34.4 1895 38.4 38.4 1894 36.7 36.7 1893 34.9 34.9 1892 32.2 32.2 1891 42.5 42.5 1890 30.0 30.0 1889 39.7 39.7 1888 34.7 34.7 1887 33.4 33.4 1886 29.7 29.7 1885 35.3 35.3 1884 33.6 33.6 1883 31.6 31.6 1882 30.6 30.6 1881 39.0 39.0 1880 26.4 26.4 1879 36.8 36.8 1878 33.2 33.2 1877 37.4 37.4 1876 25.0 25.0 1875 33.4 33.4 1874 34.4 34.4 1873 36.7 36.7 1872 26.7 26.7 1871 29.0 29.0 Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 40.7 40.7 2022 38.5 38.5 2021 43.8 43.8 2020 39.2 39.2 2019 38.3 38.3 2018 40.1 40.1 2017 35.0 35.0 2016 38.3 38.3 2015 50.8 50.8 2014 40.5 40.5 2013 38.5 38.5 2012 41.5 41.5 2011 43.3 43.3

All that -AO did was trap mild Pacific air underneath.

It’s tough to use the guidance that far out for exact temperatures and departures. We mostly use it to guess where the areas of above and below normal will be. Like the charts that the CPC puts out each day. Plus we also use it to compare how that forecast period is changing in relation to previous runs. But we know that in the past when we had similar projected 500 mb patterns in late December with fast Pacific flow the warmer days in NYC had highs in the 50s and lows in the upper 30s to around 40. The average split in NYC for late December is 42/32. So that means the warmest days during the period can be over +10. And probably a string of other days near +3 to +5.

Yeah, December 1997 actually started out much cooler than this December. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Mean Avg Temperature Dec 1 to Dec 9 Missing Count 2023-12-09 45.4 0 2022-12-09 45.4 0 2021-12-09 43.2 0 2020-12-09 40.3 0 2019-12-09 37.5 0 2018-12-09 38.0 0 2017-12-09 43.9 0 2016-12-09 42.5 0 2015-12-09 47.4 0 2014-12-09 40.7 0 2013-12-09 42.8 0 2012-12-09 45.4 0 2011-12-09 47.6 0 2010-12-09 35.1 0 2009-12-09 43.0 0 2008-12-09 37.3 0 2007-12-09 32.8 0 2006-12-09 38.6 0 2005-12-09 33.2 0 2004-12-09 43.8 0 2003-12-09 30.9 0 2002-12-09 30.6 0 2001-12-09 53.1 0 2000-12-09 32.1 0 1999-12-09 45.8 0 1998-12-09 56.2 0 1997-12-09 39.2 0

At least 97-98 had a nice snowstorm at the end which NYC didn’t get last winter. So it lived up to a weaker version of the backloaded El Niño expectations. Data for March 22, 1998 through March 22, 1998 Click column heading to sort ascending, click again to sort descending. State Name Station Type Total Snowfall NJ GREENWOOD LAKE COOP 7.0 NY YORKTOWN HEIGHTS 1W COOP 7.0 NJ CHARLOTTEBURG RESERVOIR COOP 6.0 NY WEST POINT COOP 6.0 NY NY CITY CENTRAL PARK WBAN 5.0 NJ WANAQUE RAYMOND DAM COOP 4.8 NJ RINGWOOD COOP 4.8 NJ CANOE BROOK COOP 4.5 NY LAGUARDIA AIRPORT WBAN 4.5 NJ HARRISON COOP 4.5 NY WEST NYACK COOP 4.5 NY MINEOLA 1 NE COOP 4.2 NJ MIDLAND PARK COOP 4.0 NY PORT JERVIS COOP 3.7 NY DOBBS FERRY-ARDSLEY COOP 3.5 NY MINEOLA COOP 3.5 NJ NEWARK LIBERTY INTL AP WBAN 3.1 NY WALDEN 1 ESE COOP 3.0 NY JFK INTERNATIONAL AIRPORT WBAN 2.9 NY NEW YORK AVE V BROOKLYN COOP 2.8 NJ CRANFORD COOP 2.5 NJ WAYNE COOP 2.5 NJ PLAINFIELD COOP 2.3 NY RIVERHEAD RESEARCH FARM COOP 2.0 NY ISLIP-LI MACARTHUR AP WBAN 1.6

The 97-98 winter wasn’t really that warm compared to our recent warmest winters since 11-12. 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

We knew the models were going to go into full push back mode with the cooler temperatures in late December once they saw how strong this MJO and jet extension was going to be. Dec 25-Jan 1 New run Old run

That Pacific Trough will be off the charts for the 2nd half of December.

While our warmest December by far was during the 2015 super El Niño, Decembers have been warm regardless of El Niño or La Niña. 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 ENSO 1 2015 50.8 El Niño 2 2001 44.1 Neutral following 3 year La Niña 3 2021 43.8 La Niña 4 1984 43.7 La Niña 5 2006 43.6 El Niño 6 2011 43.3 La Niña 7 1998 43.1 La Niña 8 1982 42.7 El Niño 9 1990 42.6 Neutral 10 1891 42.5 Neutral 11 1994 42.2 El Niño 12 1923 42.0 El Niño 13 2012 41.5 Neutral 14 1996 41.3 Neutral - 1953 41.3 El Niño 15 1979 41.1 El Nino 16 1956 40.9 Neutral - 1931 40.9 Neutral 17 1971 40.8 La Niña 18 2014 40.5 El Niño - 1965 40.5 El Niño 19 1957 40.2 El Niño 20 2018 40.1 Uncoupled El Niño

The 5 day period around St. Patrick’s Day since 2011 has been much snowier in NYC than the five day period around Christmas. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Mar 12 to Mar 22 Missing Count 2022-03-22 T 0 2021-03-22 T 0 2020-03-22 0.0 0 2019-03-22 0.0 0 2018-03-22 8.4 0 2017-03-22 7.6 0 2016-03-22 0.5 0 2015-03-22 4.5 0 2014-03-22 0.0 0 2013-03-22 3.3 0 2012-03-22 0.0 0 2011-03-22 T 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 20 to Dec 30 Missing Count 2022-12-30 T 0 2021-12-30 0.2 0 2020-12-30 T 0 2019-12-30 T 0 2018-12-30 T 0 2017-12-30 0.7 0 2016-12-30 T 0 2015-12-30 T 0 2014-12-30 T 0 2013-12-30 T 0 2012-12-30 0.4 0 2011-12-30 0.0 0

Main issue is that trough in the Southeast is filled with mild Pacific air following the big jet extension.