bluewave

If we define winter as the number of days with the average temperature under 40°, then EWR to POU have lost about 3 weeks since 1950.

Yeah, the GFS skill dropped with the upgrade.

There were 29 seasons with over 35” and under 15.0” at Islip in roughly the last 30 years. Only 8 seasons with such extreme highs or lows during the previous roughly 30 interval. So it’s has been an all or nothing snowfall pattern at ISP since the early 1990s. Over 35” and under 15” years bolded Monthly Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 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 2017-2018 0.0 T 6.0 22.0 1.4 31.9 4.6 65.9 2016-2017 T T 3.2 14.0 14.7 7.4 T 39.3 2015-2016 0.0 0.0 T 24.8 13.2 3.2 0.2 41.4 2014-2015 0.0 T 0.4 30.2 13.4 19.7 0.0 63.7 2013-2014 0.0 0.3 8.1 25.2 24.5 5.4 0.2 63.7 2012-2013 0.0 4.2 0.6 3.3 31.4 7.4 0.0 46.9 2011-2012 0.3 0.0 T 3.8 0.6 T 0.0 4.7 2010-2011 0.0 T 14.9 34.4 3.9 2.1 T 55.3 2009-2010 0.0 0.0 25.3 6.4 21.7 0.4 0.0 53.8 2008-2009 0.0 T 10.4 8.9 3.3 13.6 T 36.2 2007-2008 0.0 0.0 2.6 0.8 7.3 T 0.0 10.7 2006-2007 0.0 T 0.0 1.0 4.2 3.8 T 9.0 2005-2006 0.0 0.5 7.6 4.7 19.9 3.2 0.1 36.0 2004-2005 0.0 T 7.0 21.5 17.0 13.3 0.0 58.8 2003-2004 0.0 0.0 15.5 19.1 1.1 5.7 0.0 41.4 2002-2003 0.0 1.0 16.0 2.6 26.3 3.7 5.0 54.6 2001-2002 0.0 0.0 0.0 3.7 T T 0.0 3.7 2000-2001 T 0.0 10.8 9.2 8.6 10.3 T 38.9 1999-2000 0.0 T 0.4 5.8 2.6 0.2 T 9.0 1998-1999 0.0 0.0 3.0 4.5 2.8 9.1 T 19.4 1997-1998 0.0 T 1.0 T T 1.6 T 2.6 1996-1997 0.0 T 1.2 3.3 2.2 3.7 2.0 12.4 1995-1996 0.0 3.0 13.3 20.2 19.0 12.0 9.6 77.1 1994-1995 0.0 T T T 5.1 T 0.0 5.1 1993-1994 0.0 T 3.3 8.8 20.0 5.0 0.0 37.1 1992-1993 0.0 0.0 2.1 2.3 10.9 13.3 0.0 28.6 1991-1992 0.0 0.0 2.0 2.3 1.5 7.6 T 13.4 1990-1991 0.0 0.0 4.0 3.6 4.3 1.9 0.0 13.8 Monthly Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 1989-1990 0.0 7.6 0.2 2.0 2.0 4.2 3.0 19.0 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 1968-1969 0.0 T 3.0 T 19.5 11.0 0.0 33.5 1967-1968 0.0 2.5 5.0 9.1 3.0 3.0 0.0 22.6 1966-1967 0.0 0.0 8.6 1.0 19.5 21.7 T 50.8 1965-1966 0.0 0.0 T 12.1 3.6 0.0 0.0 15.7 1964-1965 0.0 0.0 2.0 24.6 7.4 4.5 1.0 39.5 1963-1964 0.0 T 11.0 11.7 16.0 1.0 0.0 39.7

We appreciate all the different voices and levels of experience here. That’s what makes this such a unique forum. The one truth about all monthly analogs is that they aren’t revealed to us until the month is nearly over. When analogs are discussed, we are just presenting a range of possibilities that have happened in the recent past. Plus in our warmer climate, analogs older than 10 years or so seldom work out.

That’s why cold is so important this time of year. A marginal or warm airmass for the coast can be fine over the interior parts of the forum. The December average snowfall since the super El Niño in those areas is about double that of NYC. Monthly Total Snowfall for PORT JERVIS, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 7.4 7.4 2021 2.5 2.5 2020 12.8 12.8 2019 9.0 9.0 2018 1.0 1.0 2017 13.0 13.0 2016 13.5 13.5 2015 0.0 0.0 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 3.4 3.4 2021 0.2 0.2 2020 10.5 10.5 2019 2.5 2.5 2018 T T 2017 7.7 7.7 2016 3.2 3.2 2015 T T

We won’t know for sure unless one of these day 15 forecasts can make it to day 8-10. Notice how the EPS and GEFS keep underestimating the -PNA days 11-15. Now that the period is day 8-10 and the -AO ridge is building down into New England with a deeper -PNA trough over the Western US and Canada. Anytime the ensembles have a ridge axis day 15 in the Aleutians we can count on the -PNA verifying lower. New 204 hr Old 360 hr

NYC got only 0.2” in December 2012 and ISP 0.5”. There was one snow event on the 26th. There were a few inches just west of I-95 and more up in Orange County.

The BNL tower thermometer shows how shallow these radiational cooling inversions are. Near 40° at 50m and around 20° at 2m. So go up about 16 stories above the pine barrens and the temperature is similar to the heat island in NYC.

The answer for NYC snowfall is that a-3 to -4 SD AO in December depends on the Pacific. We had a 10”+ snowstorm in 2020 with the lowest monthly AO reaching -3.197. But that month featured a strong +PNA. NYC got under 1” in December 2012 with a -3.902 lowest AO reading. The Pacific stayed too hostile with a -PNA. Both years featured a SSW event in January and great February snowstorms. https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.ao.index.b500101.current.ascii 10.5 “ snow in NYC 0.3 snow in NYC

Stronger systems will tend to hug coast with coastal rains and potential interior higher elevation snows. Weaker systems will get suppressed or sheared due to the stronger -NAO and fast Pacific flow. So the actual storm track might not matter that much for snow near the coast. Not much in the way of cold air next 10 days on the EPS.

I will give the models credit for getting the -NAO and -AO pattern correct. But both the GEFS and EPS have been underestimating the strength of the -PNA trough days 11-15. So we could have another warmer than average December if the cooldown keeps getting pushed back. New 240 hr forecast for 12-14 Old 360 hr forecast 12-14

The RadarScope app has all the airport radars like TJFK and TEWR.

First half of December should be several degrees warmer than average as the fast Pacific flow and -PNA keep temperatures mild.

That’s the well known CFS cold bias with the blue line at the very bottom. It’s not meant to be a temperature forecasting tool. I am not sure why the CFS is even run anymore since the long range seasonal forecasts are very inaccurate. https://www.emc.ncep.noaa.gov/users/verification/global/gfs/ops/grid2grid_all_models/bias/

They are a great resource to show what is going on around the airports with a shorter range. I can remember one of NWS Mets commenting on using them during a severe storm outbreak to supplement the NWS radar. Since the radar echoes with snow were so intense during Nemo, they wrote a whole study on them. Maybe there was a location between spotter measurements that picked up 7-8” inches in one hour. But with all the drifting, we may never be able to know for sure. I have heard 6” per hour rates. But there are always gaps between observations. https://journals.ametsoc.org/view/journals/wefo/29/6/waf-d-14-00056_1.xml Abstract On 8–9 February 2013, the northeastern United States experienced a historic winter weather event ranking among the top five worst blizzards in the region. Heavy snowfall and blizzard conditions occurred from northern New Jersey, inland to New York, and northward through Maine. Storm-total snow accumulations of 30–61 cm were common, with maximum accumulations up to 102 cm and snowfall rates exceeding 15 cm h−1. Dual-polarization radar measurements collected for this winter event provide valuable insights into storm microphysical processes. In this study, polarimetric data from the Weather Surveillance Radar-1988 Doppler (WSR-88D) in Upton, New York (KOKX), are investigated alongside thermodynamic analyses from the 13-km Rapid Refresh model and surface precipitation type observations from both Meteorological Phenomena Identification Near the Ground (mPING) and the National Weather Service (NWS) Forecast Office in Upton, New York, for interpretation of polarimetric signatures. The storm exhibited unique polarimetric signatures, some of which have never before been documented for a winter system. Reflectivity values were unusually large, reaching magnitudes >50 dBZ in shallow regions of heavy wet snow near the surface. The 0°C transition line was exceptionally distinct in the polarimetric imagery, providing detail that was often unmatched by the numerical model output. Other features include differential attenuation of magnitudes typical of melting hail, depolarization streaks that provide evidence of electrification, nonuniform beamfilling, a “snow flare” signature, and localized downward excursions of the melting-layer bright band collocated with observed transitions in surface precipitation types. In agreement with previous studies, widespread elevated depositional growth layers, located at temperatures near the model-predicted −15°C isotherm, appear to be correlated with increased snowfall and large reflectivity factors ZH near the surface.

Nemo had an amazing coverage of 30”+ amounts around the region. But those amounts were restricted to east of NYC. It was one of the few times just getting 10”-20” was a disappointment. CONNECTICUT ...FAIRFIELD COUNTY... FAIRFIELD 35.0 1000 AM 2/09 PUBLIC STRATFORD 33.0 1030 AM 2/09 PUBLIC MONROE 30.0 900 AM 2/09 SKYWARN SPOTTER BRIDGEPORT 30.0 658 AM 2/09 COOP OBSERVER MIDDLESEX COUNTY... EAST HADDAM 35.5 845 AM 2/09 PUBLIC OLD SAYBROOK 30.0 1200 PM 2/09 CT DOT NEW HAVEN COUNTY... HAMDEN 40.0 100 PM 2/09 PUBLIC MILFORD 38.0 615 AM 2/09 PUBLIC CLINTONVILLE 37.0 1040 AM 2/09 SKYWARN SPOTTER OXFORD 36.2 600 AM 2/09 SKYWARN SPOTTER NORTH BRANFORD 36.0 1100 AM 2/09 PUBLIC MERIDEN 36.0 200 PM 2/09 PUBLIC YALESVILLE 35.0 909 AM 2/09 SKYWARN SPOTTER WALLINGFORD 35.0 700 AM 2/09 PUBLIC NEW HAVEN 34.3 600 AM 2/09 CT DOT WEST HAVEN 34.0 1040 AM 2/09 PUBLIC NORTHFORD 33.5 950 AM 2/09 SKYWARN SPOTTER WOLCOTT 33.0 457 AM 2/09 SKYWARN SPOTTER EAST HAVEN 33.0 1005 AM 2/09 SKYWARN SPOTTER GUILFORD 33.0 1113 AM 2/09 BROADCAST MEDIA NORTH GUILFORD 32.0 900 AM 2/09 SKYWARN SPOTTER WATERBURY 32.0 900 AM 2/09 PUBLIC MADISON 32.0 321 AM 2/09 PUBLIC NAUGATUCK 30.0 600 AM 2/09 PUBLIC NEW LONDON COUNTY... COLCHESTER 31.0 1200 PM 2/09 CT DOT

Nemo was the only snowstorm since the Doppler radars came out to have a 50 dbz snow band near our area. https://www.washingtonpost.com/blogs/capital-weather-gang/post/incredible-imagery-from-the-february-8-9-2013-new-england-blizzard/2013/02/11/b51df444-73f1-11e2-aa12-e6cf1d31106b_blog.html

A deep trough in the West can work for us later in the season. Nemo in February 2013 probably had the most unusual teleconnection set up for a 30”+ event in our area. But that involved a phase. So the trough kept the heaviest snows east of NYC.

It took close to 10 days for the retrogression to complete following the strongest global 500 mb block since 1950. https://blogs.agu.org/wildwildscience/2011/01/26/while-the-u-s-shivered-amazing-arctic-warmth/

Break out the snow shovels if a pattern like this starts showing up day 8-10. The composite below is the last 10 December 4”+ snowfalls in NYC since 2002. The two most important features are a -AO and Rockies Ridge. I am judging the +PNA by a ridge axis near the Rockies. The raw PNA numbers aren’t as important. But they are usually neutral -0.5 to +0.5 and higher with a ridge in the Rockies. A trough just off the West Coast or near Vancouver can be fine. We just don’t want a big digging trough over the Rockies. Last 10…4”+ December snows in NYC since 2002

The -PNA is more of a December issue. So we won’t get much snow this month if the Pacific pattern change keeps getting pushed back. But it’s less of an issue in JFM. So root for one of those day 11-15 forecast to finally verify.

It’s been tough to get colder patterns later in December since that period is warming more quickly than the early part of the month since 1981. The late December Arctic cold of 2017 was one of the greatest temperature outliers of recent times. This is also why we have seen so much warmth around the solstice to Christmas in recent years.

The reason we are seeing the models push things back is that the useful skill days 11-15 is often too low to detect a pattern change. A useful skill score is defined as 0.6 or greater. So the best that the EPS can do in most cases is about 10.5 days. The GEFS and GEPS are about a day behind at 9.5. So even the highest scoring EPS day 11-15 is still too low skill to detect a pattern change from 1-5 and 6-10 with certainty. So this is why a pattern change showing up day 11-15 needs to make it to 6-10 to be believable. It’s also why we start to see big jumps sometimes right around day 8-10. It’s just the way these models are constructed. But that isn’t to say that a pattern change on the Pacific side can’t eventually happen. Just that you want to see it survive to day 8-10 in order to lock in the specific date. https://www.emc.ncep.noaa.gov/users/verification/headlines/ Description: An Anomaly Correlation Coefficient (ACC) score of 1.0 indicates that the forecast was highly accurate (i.e., essentially perfect) across the Northern Hemisphere. A model is said to have "useful skill" when the ACC score is greater than or equal to 0.6. This plot shows the average forecast day (i.e., forecast length) when the ACC score falls below 0.6 and the GFS loses useful skill EPS in green and GEFS black and GEPS red

Over the last 10 years the average high for the whole month has been 64. There was a slow but steady rise from the 20s to the 80s. But a big jump in the last 10 years of December record warmth. Monthly Highest Max Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 64 64 2021 66 66 2020 62 62 2019 58 58 2018 61 61 2017 61 61 2016 60 60 2015 72 72 2014 65 65 2013 71 71 2012 62 62 2011 62 62 Monthly Highest Max Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 61 61 1980 64 64 1981 58 58 1982 72 72 1983 59 59 1984 70 70 1985 55 55 1986 59 59 1987 60 60 1988 60 60 1989 53 53 Monthly Highest Max Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 60 60 1959 57 57 1958 55 55 1957 59 59 1956 67 67 1955 53 53 1954 61 61 1953 63 63 1952 59 59 1951 64 64 1950 60 60 Monthly Highest Max Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 59 59 1929 56 56 1928 60 60 1927 68 68 1926 49 49 1925 58 58 1924 61 61 1923 64 64 1922 57 57 1921 59 59 1920 58 58

It was the only 30” one of our major stations. Maximum 2-Day Total Snowfall for JFK INTERNATIONAL AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 30.5 2016-01-23 0 Maximum 2-Day Total Snowfall for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 28.2 2016-01-24 Maximum 2-Day Total Snowfall for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 27.8 1996-01-08 0 Maximum 2-Day Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 27.5 2016-01-23 0 Maximum 2-Day Total Snowfall for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 27.8 2013-02-09 0 Maximum 2-Day Total Snowfall for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 30.7 1996-01-08 0 Maximum 2-Day Total Snowfall for Mount Pocono Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 32.5 1978-02-07 0 Maximum 2-Day Total Snowfall for ALLENTOWN LEHIGH VALLEY INTERNATIONAL AIRPORT, PA Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 31.9 2016-01-23 0 Maximum 2-Day Total Snowfall for Albany Area, NY (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 42.2 1888-03-13 0 Maximum 2-Day Total Snowfall for Binghamton Area, NY (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 40.0 2020-12-17 0 Maximum 2-Day Total Snowfall for Boston Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 27.6 2003-02-18 0 Maximum 2-Day Total Snowfall for Burlington Area, VT (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 35.3 2010-01-03 0 Maximum 2-Day Total Snowfall for Worcester Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 34.5 2015-01-27 0