bluewave

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

We will probably make a run on 60° this week which has become the norm in recent years.

The average first 1” in NYC since the super El Niño has been 12-17. But the spread is very wide between 11-15 and 1-23. First/Last 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. Year Last Value First Value Difference Minimum 01-18 (2020) 11-15 (2018) 226 Mean 03-01 12-17 290 Maximum 04-02 (2018) 01-23 (2016) 332 2021 02-19 (2021) 1.2 01-07 (2022) 5.8 321 2020 01-18 (2020) 2.1 12-16 (2020) 6.5 332 2019 03-04 (2019) 2.0 12-02 (2019) 1.3 272 2018 04-02 (2018) 5.5 11-15 (2018) 6.4 226 2017 03-14 (2017) 7.6 12-09 (2017) 4.6 269 2016 02-15 (2016) 1.4 12-17 (2016) 2.8 305 2015 03-20 (2015) 4.5 01-23 (2016) 27.3 308

The primary low looks to cut around the 12th. The models pushed the more favorable pattern back by a few days. So it often takes time to see PNA improvement in a La Niña pattern. New run Old day 11-15 run

Another GFS upgrade that’s actually a downgrade.

Yeah, getting a favorable Pacific isn’t that important for snowfall in Northern New England like it is for us. Some of their snowiest seasons have been out least snowy. They can do great with teleconnections that don’t work for us. Top 10 snowiest seasons in CAR and NYC snowfall Time Series Summary for Caribou Area, ME (ThreadEx) - Oct through Sep Click column heading to sort ascending, click again to sort descending. Rank Season Total Snowfall NYC Snowfall 1 2007-2008 197.8 11.9 2 1954-1955 181.1 11.5 3 2018-2019 165.4 20.5 4 1981-1982 159.8 24.6 5 1972-1973 153.0 2.8 6 2019-2020 151.9 4.8 7 1968-1969 151.6 30.2 8 2013-2014 150.7 57.4 9 1962-1963 147.5 16.3 10 1976-1977 145.9 24.5

December and February have been the toughest winter months to get a cold departure since the super El Niño. NYC Feb 22….+1.4 Jan 22….-3.2 Dec 21….+4.7 Feb 21….-1.1 Jan 21….+2.2 Dec 20…+1.7 Feb 20…+4.8 Jan 20….+6.5 Dec 19….+0.8 Feb 19….+0.9 Jan 19….-0.1 Dec 18…+2.6 Feb 18…+6.7 Jan 18….-0.9 Dec 17…..-2.5 Feb 17…..+6.3 Jan 17….+5.4 Dec 16….+0.8 Feb 16….+2.4 Jan 16….+1.9 Dec 15….+13.3

We have had only 1 colder than average December since 2011. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Year Mean Avg Temperature Departure 2021 43.8 +4.7 2020 39.2 +1.7 2019 38.3 +0.8 2018 40.1 +2.5 2017 35.0 -2.5 2016 38.3 +0.8 2015 50.8 +13.3 2014 40.5 +3.0 2013 38.5 +1.0 2012 41.5 +4.0 2011 43.3 +5.8 2010 32.8 -4.5

The hope is that the longer we sustain a -AO-NAO, the better a chance that we start to get a coastal storm track instead of a cutter. But we’ll probably have to be patient. The signal of the pattern change is when the 11-15 day colder forecast survives to the 6-10.

We didn’t have the record warm pool off the East Coast in 2010 so the SE Ridge wasn’t an issue back then. Notice how models haven’t been able to see the SE Ridge day 11-15 recently. So the colder pattern keeps getting pushed back. I think there is more going on here than the typical errors handling the Pacific Jet. It’s an potential underestimation of warm water feedback process off the East Coast in the long range. SSTs much warmer than 2010 to our east New 6-10 colder gets pushed back Old 11-15 missed the SE Ridge

This may be the first time we get a 6 sigma Greenland Block with a Southeast Ridge. I believe this is the only one since December 16,2010. That one was the all-time blocking record for the Northern Hemisphere. The big difference in 2010 was that there was no SE Ridge and it was much colder. So it follows the trend of warmer -NAO patterns.

Yeah, quite a bit of Pacific variability days 11-15 among the big 3. But I guess this is to be expected. Getting the Pacific Jet right that far out isn’t a model strength.