bluewave

This is one of the most extreme December patterns that we have experienced in terms of temperature and precipitation volatility across the CONUS.

Made it to 49° here with the MOS and raw guidance forecast for low 40s. Noticed the MOS from several days ago was around 50° but it shifted colder. Models often underestimate highs with sunny and windy downslope flow and the cold air lagging frontal passage.

Big guidance beat today with some spots sneaking in a 50° high so far. MacArthur/ISP PTSUNNY 50 21 32 W18G29

You are correct. The recently added Newark snowfall back to 1843-1844 shows a 30 year snowfall average of 43.7”. So areas just west of the present I-95 corridor were probably closer to 50”. The winter average temperature then was 30.7° which is 7° colder than the most recent 10 year average. Monthly Total Snowfall for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Mean 0.1 0.8 9.1 12.1 12.6 7.3 1.8 43.7 1843-1844 0.0 1.3 9.5 5.5 13.5 1.8 0.0 31.6 1844-1845 0.0 0.5 6.5 5.5 20.5 5.5 T 38.5 1845-1846 0.0 T 8.5 16.5 28.0 T T 53.0 1846-1847 0.0 1.5 12.0 10.0 21.0 4.3 0.5 49.3 1847-1848 0.0 T 6.0 T 8.0 5.0 T 19.0 1848-1849 0.0 1.3 24.0 T 13.0 6.0 0.0 44.3 1849-1850 0.0 0.0 11.0 3.0 T 9.0 8.0 31.0 1850-1851 0.0 0.0 6.0 2.5 3.5 10.5 2.0 24.5 1851-1852 0.0 2.0 7.0 20.0 14.0 16.0 4.3 63.3 1852-1853 0.0 T T 15.5 2.3 7.0 T 24.8 1853-1854 0.0 M 6.0 15.0 23.5 2.8 13.5 60.8 1854-1855 0.0 T 8.0 18.5 16.0 2.5 T 45.0 1855-1856 0.0 T 9.0 32.8 5.0 11.0 0.0 57.8 1856-1857 0.0 0.5 4.3 28.1 2.1 17.0 0.0 52.0 1857-1858 0.0 T 4.5 1.8 10.5 10.5 T 27.3 1858-1859 0.0 5.5 6.5 12.3 15.8 6.0 T 46.1 1859-1860 3.0 0.0 5.1 11.3 25.0 2.5 T 46.9 1860-1861 0.0 T 7.0 20.6 1.3 17.0 2.0 47.9 1861-1862 0.0 1.0 1.0 12.0 25.5 4.6 6.0 50.1 1862-1863 0.0 6.5 8.0 10.0 13.0 10.9 1.8 50.2 1863-1864 0.0 T 4.3 7.0 1.0 7.0 T 19.3 1864-1865 0.0 0.3 26.0 10.5 12.5 T 0.0 49.3 1865-1866 0.0 0.0 13.1 11.8 8.0 1.5 T 34.4 1866-1867 0.0 T 7.0 23.5 15.5 17.5 T 63.5 1867-1868 0.0 T 15.5 23.3 14.0 15.0 7.0 74.8 1868-1869 T 0.0 9.5 11.0 12.0 5.0 0.6 38.1 1869-1870 T T 8.1 1.8 8.5 11.0 3.0 32.4 1870-1871 0.0 T 5.0 16.0 16.1 1.3 2.0 40.4 1871-1872 0.0 T 8.5 2.0 5.0 8.5 T 24.0 1872-1873 0.0 4.0 25.1 14.1 23.3 2.2 3.0 71.7 Monthly Mean Avg Temperature for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Mean 32.2 29.1 30.7 30.7 1843-1844 33.4 25.5 31.5 30.1 1844-1845 32.5 33.4 32.7 32.9 1845-1846 27.7 30.7 27.2 28.5 1846-1847 30.8 31.7 29.5 30.7 1847-1848 35.1 33.7 30.5 33.1 1848-1849 40.5 24.5 24.9 30.0 1849-1850 33.4 33.5 35.4 34.1 1850-1851 33.2 33.9 36.6 34.6 1851-1852 27.7 25.9 30.9 28.2 1852-1853 39.9 31.9 35.1 35.6 1853-1854 32.4 28.4 30.6 30.5 1854-1855 29.7 32.4 26.9 29.7 1855-1856 33.7 22.3 25.2 27.1 1856-1857 30.8 21.1 35.2 29.0 1857-1858 37.4 35.1 26.4 33.0 1858-1859 34.1 31.5 33.2 32.9 1859-1860 28.6 29.0 29.3 29.0 1860-1861 29.1 28.9 35.7 31.2 1861-1862 35.1 27.1 30.3 30.8 1862-1863 33.4 32.8 31.9 32.7 1863-1864 30.8 29.6 33.4 31.3 1864-1865 32.6 21.7 30.0 28.1 1865-1866 35.6 28.3 30.6 31.5 1866-1867 31.4 22.9 36.4 30.2 1867-1868 27.5 25.4 21.3 24.7 1868-1869 28.3 33.1 33.8 31.7 1869-1870 33.0 36.2 30.6 33.3 1870-1871 33.7 26.4 29.7 29.9 1871-1872 29.6 29.7 29.9 29.7 1872-1873 24.8 24.9 27.5 25.7

Really extreme swings in terms of snowfall and temperatures across the CONUS this month with California being a prime example.

This has to be the most extreme -WPO +EPO dipole that we have seen in December. Lead to the unusually strong ridge out West with the -PNA for such a strong -WPO. Record Pacific Jet and historic flooding in the Pacific Northwest. Strong December -WPO 500 mb composite more -EPO snd weaker Western U.S. ridge

Yeah, Christmas 2020 was very rough for the ski resorts with the fastest loss of a near 40”+snowpack around BGM on record for late December. Climatological Data for BINGHAMTON (GREATER AP), NY - December 2020 2020-12-17 22 15 18.5 -9.2 46 0 1.69 26.4 39 2020-12-18 22 8 15.0 -12.4 50 0 0.00 0.0 31 2020-12-19 24 3 13.5 -13.6 51 0 0.00 0.0 29 2020-12-20 31 21 26.0 -0.9 39 0 0.14 1.8 26 2020-12-21 36 29 32.5 5.9 32 0 0.02 T 25 2020-12-22 34 27 30.5 4.1 34 0 0.01 0.1 22 2020-12-23 36 22 29.0 2.8 36 0 0.00 0.0 20 2020-12-24 50 34 42.0 16.1 23 0 1.55 0.0 19 2020-12-25 53 20 36.5 10.8 28 0 0.80 0.8 1 Data for Binghamton Area, NY (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1969-12-25 18 -8 0.16 2.4 14 1969-12-26 25 16 0.93 13.6 18 1969-12-27 21 16 0.14 4.9 32 1969-12-28 24 20 0.01 1.0 33 1969-12-29 26 16 0.00 0.0 29 1969-12-30 29 24 T T 24 1969-12-31 27 9 0.31 2.5 20 1970-01-01 19 5 0.00 0.0 19 1970-01-02 17 1 T T 18 1970-01-03 26 13 0.09 1.7 18 1970-01-04 20 9 0.01 0.3 18 1970-01-05 27 8 0.01 0.3 17 1970-01-06 24 17 T 0.1 18 1970-01-07 20 12 T T 18 1970-01-08 12 -1 T 0.3 18 1970-01-09 5 -7 T T 18 1970-01-10 17 5 0.06 2.1 19 1970-01-11 23 13 0.01 0.2 20 1970-01-12 22 14 0.15 2.3 21 1970-01-13 24 15 0.05 2.0 23 1970-01-14 15 7 0.02 0.6 24 1970-01-15 12 2 T T 24 1970-01-16 35 7 0.00 0.0 23

Don’t be so hard on yourself as you are one of the best forecasters on here. When I saw how extreme the December2015 forcing for an El Niño in the WPAC was leading to the +13.3 in NYC, it caused me to gain a ton of respect for what has been occurring in the WPAC. https://phys.org/news/2021-04-distinctive-mjo-super-el-nino.html A research group, led by Dr. Wenjun Zhang from the Nanjing University of Information Science and Technology analyzed MJO activity of the super El Niño event during the Northern Hemisphere winter of 2015/16. Observations show that the western Pacific MJO activity was strongly suppressed during the peak phase of the 1982/83 and 1997/98 super El Niño events. However, during the crest of the 2015/16 super El Niño event, western Pacific MJO-related convection was enhanced. "It is apparent that the enhanced western Pacific MJO is mainly related to its sea surface temperature (SST) anomaly distribution and the associated background thermodynamic conditions." said Dr. Zhang. His team's complete research and data are published in Advances in Atmospheric Sciences. When compared to the previous super El Niño events, the warm SST anomaly, or change from average, of the 2015/16 El Niño was located more westward than during the other two extreme seasons. Additionally, no significant cold SST anomaly was detected in the western Pacific. Accordingly, the moisture and air temperature tended to increase in the central-western Pacific during the winter of 2015/16 unlike the previous super El Niño events. This research highlights that climatologists should consider the SST anomaly distribution of super El Niño events for future MJO activity studies.

Our annual warm up over 55° between 12-17 and 12-25 was right on schedule. This pattern has become more pronounced over the years. While the general pattern did exist prior to 2011, this is the first 15 year run with no interruption. The last time we didn’t see this warm up was back in 2009 and 2010. Data for December 19, 2025 through December 19, 2025 Click column heading to sort ascending, click again to sort descending. CT DANBURY MUNICIPAL AP WBAN 60 NJ NEWARK LIBERTY INTL AP WBAN 59 NJ TETERBORO AIRPORT WBAN 59 NJ CALDWELL ESSEX COUNTY AP WBAN 59 NY ISLIP-LI MACARTHUR AP WBAN 59 NY RIVERHEAD RESEARCH FARM COOP 59 NY LAGUARDIA AIRPORT WBAN 58 NY NY CITY CENTRAL PARK WBAN 58 NY MONTGOMERY ORANGE COUNTY AP WBAN 58 CT NEW HAVEN TWEED AP WBAN 58 CT MERIDEN MARKHAM MUNICIPAL AP WBAN 58 NY FARMINGDALE REPUBLIC AP WBAN 57 NY JFK INTERNATIONAL AIRPORT WBAN 57 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 57 NY WESTCHESTER CO AP WBAN 57 NY SHIRLEY BROOKHAVEN AIRPORT WBAN 57 NY BAITING HOLLOW COOP 57 NY UPTON COOP - NWSFO NEW YORK COOP 57 CT NORWICH PUBLIC UTILITY PLANT COOP 57 NJ HARRISON COOP 56 NJ TETERBORO AIRPORT COOP 56 NY ST. JAMES COOP 56 CT GROTON NEW LONDON AP WBAN 56 NY CENTERPORT COOP 55

This will be a good test for the AIFS EPS coming up since it matches the composite more than the EPS with the further east ridge axis.

Very nice job. Can’t say I remember seeing this accumulation pattern before from a clipper. I didn’t notice any available models showing the NW heavy snow band from Sussex into Orange and surrounding areas.

Yeah, we would want the ridge in a similar position to what we got with the recent clipper to make things interesting. I am just not sure yet whether the Pacific Jet can relax enough to allow for sufficient retrogression. The time to watch would probably be early in January.

This is going to be one of the strongest -WPO blocks that we have seen for the month of December. But it’s a different configuration of other factors that we have previously seen with December -WPOs in the past. This one has a much more amplified Pacific Jet into the PACNW and BC than we have seen before with the historic flooding in those areas. Plus we have an out of phase +EPO and very strong ridge onto the Western US. The ridge that was out West is shifting further east leading to the moderation in temperatures across the CONUS. Unique December 2025 500 mb and Pacific Jet stream pattern compared to previous very strong -WPO patterns

This is the first 20 day below normal streak for the new 1991-2020 climate normals era. xmACIS2 reset all the prior period departures to the 1991-2020 climate normals. So we don’t have the earlier departures based on 1981-2010, 1971-2000, 1961-1990, 1951-1980..etc.

2010-2011 was some of the biggest snow piles my whole time in Long Beach where the old amusement park used to be.