bluewave

It’s possible if the SSW can shift the MJO. Phases 6-7 would be more -EPO in February. Plenty of moving parts so we’ll just have to wait and see how things go. https://iopscience.iop.org/article/10.1088/1748-9326/ab98b5 4. Conclusions The intraseasonal variability in tropical heating related to the MJO can exert an impact on the stratospheric polar vortex (e.g. Garfinkel et al 2012, 2014). However, there has been little written about the propagation features and intensity of the MJO after SSW event occur. In the present study, it is expected that SSWs can affect the MJO based on the above findings. The dominant occurrence of MJO phases 6 and 7; the simultaneously enhanced convective activity over the equatorial Central and Western Pacific during 1 ~ 24 d after onset of SSW events; and then the coherent eastward propagation of tropical intraseasonal convection in the following days all indicate that the influence of SSWs on tropical intraseasonal convection related to the MJO cannot be ignored. Although the dynamic and physical mechanism(s) are unclear, this SSW–MJO link is consistent with the thermal stratification change in the tropical upper troposphere. Presumably, the SSW–MJO link is associated with multiple factors. The responses of static stability in the tropical upper troposphere and lower stratosphere (UTLS) to SSW event described above may not be the sole potential mechanism by which SSW affects the MJO. Other mechanisms, such as vertical wind shear (Ho et al 2009), absolute vorticity (Collimore et al 2003), and tropopause changes (Gray et al 1992), can also be adopted to explain the responses of tropical convection to the anomaly in the UTLS region. Thus, to identify the exact mechanism(s), further studies using both observations and numerical model simulations are necessary. The impacts from SSWs could affect tropical intraseasonal convection related to MJO on time scales exceeding 20 d. More importantly, this work demonstrated the complex relationship between the MJO and SSW. Previous studies have shown a strong impact of the MJO on the NH wintertime stratospheric polar vortex. However, the results of this study allude to the reverse route, i.e. alteration of the tropical intraseasonal convection related to the MJO due to the abrupt change in the extratropical stratosphere. Although the results need to be further confirmed by numerical models that resolve stratospheric processes, this study suggests that SSW is indispensable for the subseasonal-to-seasonal prediction of the evolution of MJO. In this regard, it is also anticipated that the statistical prediction of MJO could be improved by taking variability in the extratropical stratosphere into consideration as a potential predictor especially in boreal winter.

The retrograding block will also have a MJO 3-6 standing wave. We could very well go +EPO/+PNA/-AO/-NAO. So a high water content heavy wet snow for the storms that are cold enough. Maybe a continuation of the tree damage theme as branches could snap under the weight of the snow.

Yeah, we could easily finish with above normal January snowfall and a warm departure. Islip averaged 38.0° in March 2018 and finished with 31” of snow. The NYC average in January is 32.6°. So March 2018 temperatures in a January would have been +5.4. It really comes down to getting a favorable Pacific and storm track with just cold enough for snow. February 2017 was another example on Long Island. Islip recorded 14.7”of snow at an average temperature of 37.8. NYC was able to go to 10.4” in December with a 39.3 average temperature. That’s why I think that we’ll continue to experience great snowstorms even as the winters continue to warm. We showed a few winters ago that we could go 40/40.

Only the 2nd time out of 16 Decembers for NYC in the 39.0° range to reach 10” of snow. 23 1999 39.9 T 24 1889 39.7 6.0 25 1991 39.6 0.7 26 1987 39.5 2.6 - 1911 39.5 8.5 28 1949 39.4 1.3 - 1918 39.4 0.3 30 1974 39.3 0.1 - 1928 39.3 2.0 - 1912 39.3 11.4 33 2020 39.2 10.5 34 1951 39.1 3.3 - 1932 39.1 9.4 36 1986 39.0 0.6 - 1973 39.0 2.8 - 1881 39.0 1.3

31 06:58 SE 35 G 41 7.00 Overcast and Windy BKN006 OVC011 35 34 97% 21 NA 27.42 928.9 31 05:58 SE 39 G 52 5.00 Light Snow Fog/Mist and Windy SCT009 OVC015 35 34 97% 20 NA 27.48 930.9 31 04:58 SE 44 G 54 5.00 Light Snow Fog/Mist and Windy FEW011 OVC017 35 34 94% 19 NA 27.57 934.0 31 03:58 SE 44 G 52 7.00 Mostly Cloudy and Windy BKN024 BKN033 36 33 90% 21 NA 27.65 936.7 31 02:58 SE 44 G 51 7.00 Mostly Cloudy and Windy FEW027 SCT049 BKN055 BKN070 35 35 99% 19 NA 27.72 939.0 31 01:58 E 44 G 61 3.00 Light Snow Fog/Mist and Windy BKN007 OVC012 33 33 33 31 99% 17 NA 27.80 941.8 31 00:58 E 54 G 70 2.50 Light Snow Fog/Mist and Windy BKN008 32 32 99% 14 NA 27.93 946.2 30 23:58 E 60 G 74 2.00 Light Snow Fog/Mist and Windy FEW006 32 32 100% 13 NA 28.06 950.6 30 22:58 E 61 G 83 0.75 Rain Fog/Mist and Windy VV002 32 30 93% 13 NA 28.23 956.3 30 21:58 E 52 G 71 0.63 Rain Fog/Mist and Windy VV001 31 31 99% 13 NA 28.39 961.8 https://w1.weather.gov/obhistory/PASY.html

My favorite recent late season event was 3-22-18. Portions of the South shore of Suffolk came in at close to 20”. But you can see those mid 20s lows a few days before the storm. ISP 2018-03-17 47 25 36.0 -3.4 29 0 0.00 0.0 0 2018-03-18 40 25 32.5 -7.2 32 0 0.00 0.0 0 2018-03-19 43 24 33.5 -6.5 31 0 0.00 0.0 0 2018-03-20 37 26 31.5 -8.8 33 0 T T 0 2018-03-21 38 32 35.0 -5.6 30 0 1.70 14.9 0 2018-03-22 47 32 39.5 -1.5 25 0 0.26 3.5 18

It’s an interesting conversation about the right temperatures leading up to a 6”+ or 12”+ event in NYC in our warmer climate. The key seems to be what the low temperatures are doing in the days before or during the event. While we can have highs in the 50s or even 60s right before the storm, we need at least a few days with lows getting into at least the mid 20s or colder. I think getting the lows into at least the mid 20s before or during storm time tells us there is cold enough air supply nearby to be drawn into the developing low. This is when we get favorable storm day teleconnections and storm track and evolution. I added some of our milder events surrounding storms in recent years for illustration purposes in NYC. The cold for the December storm came with the arrival of the event. 2017-02-01 47 33 40.0 6.8 25 0 0.00 0.0 T 2017-02-02 45 32 38.5 5.2 26 0 0.00 0.0 0 2017-02-03 33 26 29.5 -3.9 35 0 0.00 0.0 0 2017-02-04 34 22 28.0 -5.5 37 0 0.00 0.0 0 2017-02-05 43 31 37.0 3.3 28 0 0.00 0.0 0 2017-02-06 49 36 42.5 8.7 22 0 0.00 0.0 0 2017-02-07 42 36 39.0 5.1 26 0 0.27 0.0 0 2017-02-08 62 38 50.0 15.9 15 0 0.03 0.0 0 2017-02-09 44 19 31.5 -2.7 33 0 1.16 9.4 2 2017-02-10 32 19 25.5 -8.9 39 0 T T 8 2017-02-11 48 30 39.0 4.5 26 0 0.00 0.0 5 2017-02-12 40 30 35.0 0.3 30 0 0.46 T 2 2017-01-04 52 34 43.0 10.0 22 0 0.00 0.0 0 2017-01-05 34 27 30.5 -2.4 34 0 0.00 0.0 0 2017-01-06 33 25 29.0 -3.8 36 0 0.05 1.2 1 2017-01-07 26 20 23.0 -9.7 42 0 0.32 5.1 T 2017-01-08 25 16 20.5 -12.1 44 0 0.00 0.0 4 2017-01-09 23 14 18.5 -14.0 46 0 0.00 0.0 3 2017-01-10 46 21 33.5 1.1 31 0 0.00 0.0 3 2017-01-11 52 42 47.0 14.6 18 0 0.52 0.0 0 2017-01-12 66 47 56.5 24.2 8 0 0.05 0.0 0 2017-01-13 62 32 47.0 14.7 18 0 0.00 0.0 0 2016-01-10 59 40 49.5 17.1 15 0 1.80 0.0 0 2016-01-11 40 26 33.0 0.6 32 0 0.00 0.0 0 2016-01-12 44 25 34.5 2.2 30 0 0.00 T 0 2016-01-13 30 22 26.0 -6.3 39 0 0.00 0.0 0 2016-01-14 38 22 30.0 -2.3 35 0 0.00 T 0 2016-01-15 51 34 42.5 10.2 22 0 T 0.0 0 2016-01-16 52 42 47.0 14.8 18 0 0.24 0.0 0 2016-01-17 42 30 36.0 3.8 29 0 0.05 0.4 0 2016-01-18 31 18 24.5 -7.8 40 0 T T T 2016-01-19 28 16 22.0 -10.3 43 0 0.00 0.0 T 2016-01-20 37 27 32.0 -0.3 33 0 0.00 0.0 T 2016-01-21 36 26 31.0 -1.3 34 0 0.00 0.0 0 2016-01-22 30 21 25.5 -6.9 39 0 0.01 0.2 0 2016-01-23 27 24 25.5 -6.9 39 0 2.31 27.3 6 2016-01-24 35 20 27.5 -5.0 37 0 T T 22 2018-03-17 48 27 37.5 -5.1 27 0 0.00 0.0 0 2018-03-18 43 28 35.5 -7.4 29 0 0.00 0.0 0 2018-03-19 47 33 40.0 -3.2 25 0 0.00 0.0 0 2018-03-20 39 30 34.5 -9.1 30 0 T 0.0 0 2018-03-21 39 31 35.0 -8.9 30 0 0.99 8.2 0 2018-03-22 50 32 41.0 -3.2 24 0 0.06 0.2 8 2020-12-13 62 47 54.5 16.3 10 0 0.00 0.0 0 2020-12-14 47 35 41.0 3.1 24 0 0.26 T 0 2020-12-15 39 30 34.5 -3.0 30 0 0.00 0.0 0 2020-12-16 31 24 27.5 -9.7 37 0 0.86 6.5 0 2020-12-17 33 24 28.5 -8.4 36 0 0.66 4.0 9

We will have to deal with a very mild start to January before we can get to the retrograding -AO block and Pacific improvement by mid-January. Looks like we are close to a new all-time lowest pressure near Alaska. So my guess is that the early part of January will represent the peak +EPO. The hope is that the -AO retrogression will allow the EPO to back off enough for more ridging to build over Western North America and more +PNA. Every model group shows this scenario so it looks like it could really happen. So we’ll just have to watch for the 11-15 means to make it to day 7 for verification and forecast purposes.

Something similar happened after the February 2018 SSW. The SPV wound up in Asia. But due to the improvement on the Pacific side, we got the record snows. So the key going forward will be the ability to get a successful NAO retrogression and Pacific improvement.

Yeah, looks just like the December pattern this year. https://advances.sciencemag.org/content/4/7/eaat6025 Previous studies have extensively investigated the impact of Arctic sea ice anomalies on the midlatitude circulation and associated surface climate in winter. However, there is an ongoing scientific debate regarding whether and how sea ice retreat results in the observed cold anomaly over the adjacent continents. We present a robust “cold Siberia” pattern in the winter following sea ice loss over the Barents-Kara seas in late autumn in an advanced atmospheric general circulation model, with a well-resolved stratosphere. Additional targeted experiments reveal that the stratospheric response to sea ice forcing is crucial in the development of cold conditions over Siberia, indicating the dominant role of the stratospheric pathway compared with the direct response within the troposphere. In particular, the downward influence of the stratospheric circulation anomaly significantly intensifies the ridge near the Ural Mountains and the trough over East Asia. The persistently intensified ridge and trough favor more frequent cold air outbreaks and colder winters over Siberia. This finding has important implications for improving seasonal climate prediction of midlatitude cold events. The results also suggest that the model performance in representing the stratosphere-troposphere coupling could be an important source of the discrepancy between recent studies.

The EPS gradually transitions the main NH blocking from the Kara-Barents regions of Europe over to the Davis Strait by the 2nd week of January. December featured a very strong block in this region and an intense East Asian Jet which carved out a deep trough over the North Pacific. This lead to the strong Pacific influence that we are experiencing from late December into early January. The shift in heights could allow the North Pacific Jet to buckle and allow a retrogression of the Greenland block. This would represent some improvement by mid-January in the EPO. Sometimes that’s all we need to get the ball rolling toward a MECS regime by mid to late January.

Several times since 1995 NYC has had a snowy December following an extremely high ACE hurricane season. Accumulated Cyclone Energy - Atlantic hide Season ACE TS HU MH NYC Dec Snowfall 2020 180.1015 30 13 6 10.5 2019 132.2025 18 6 3 2.5 2018 132.5825 15 8 2 T 2017 224.8775 17 10 6 7.7 2016 141.2525 15 7 4 3.2 2015 62.685 11 4 2 T 2014 66.725 8 6 2 1 2013 36.12 14 2 0 8.6 2012 132.6325 19 10 2 0.4 2011 126.3025 19 7 4 0 2010 165.4825 19 12 5 20.1 2009 52.58 9 3 2 12.4 2008 145.7175 16 8 5 6.0 2007 73.885 15 6 2 2.9 2006 78.535 10 5 2 0 2005 250.1275 28 15 7 9.7 2004 226.88 15 9 6 3.0 2003 176.84 16 7 3 19.8 2002 67.9925 12 4 2 11.0 2001 110.32 15 9 4 T 2000 119.1425 15 8 3 13.4 1999 176.5275 12 8 5 T 1998 181.7675 14 10 3 2.0 1997 40.9275 8 3 1 T 1996 166.1825 13 9 6 T 1995 227.1025 19 11 5 11.5

It will be interesting to see if the Bering Sea low can break the all-time record. The last January with a NW PAC low with a 932 mb pressure or lower was 2013. That also occurred around the time of a SSW. It will be interesting to see if the weeklies are correct about the -NAO retrogression and EPO improvement by mid-January. https://www.wunderground.com/blog/weatherhistorian/bering-sea-superstorm-bottoms-out-at-924-mb.html https://csl.noaa.gov/groups/csl8/sswcompendium/majorevents.html JAN 2013 7-Jan-13 6-Jan-13 7-Jan-13 6-Jan-13 N E

Makes sense that a really amped up solution would be warm at the coast with such an unfavorable Pacific. The closed low went north of us this run. We needed a perfect thread the needle UL track and storm spacing to get at least a change to snow after such a mild start to the storm.

Looks like the 12z UKMET is trying to show something like the 0z Euro. But it isn’t easy to see the exact details with these low resolution maps. https://www.meteociel.fr/modeles/ukmo2.php?carte=1021&ech=72&nh=1&archive=0

Maybe such an extreme North Pacific storm in early January means that we are nearing the peak of this +EPO cycle. If this is the case, then we would get some improvement on the Pacific side by mid-January. That could be what the weeklies are trying to show.

The timing is right for a coastal system around the 4th. Each -AO drop going back to early December has featured one. The first was on December 5th and the 2nd on the 16th. But we need the closing off of the upper low and storm separation following the New Years storm to work out. As Walt mentioned , the spacing issues could result in a scraper track if the New Years storm suppresses it. Exact storm tracks for the models are a challenge beyond 3-5 days. We just saw how the whole evolution of the New Years storm changed several days ago.

We continue to set records for warmth and snow together. This was only the 6th year with a 10”+ snowstorm in NYC from December 1st to the 20th. But it was the first December with an average temperature this warm. The warm up after the 20th was also a first to reach 60°. 2020.....39.3°......61° 2009.....35.9°......55° 2003.....37.6°......54° 1960.....30.9°......49° 1948.....38.3°......57° 1916.....34.0°......42° Record warmth to some type of snowfall record is becoming more frequent in recent years. November 2020 was the warmest on record in NYC at 53.0°...5th earliest seasonal 10.0”+ snowfall of 10.5” in December January to March 2020 was the 2nd warmest on record in NYC at 42.4°...trace of snow on May 9th tied with 1977 for latest on record after 7th coldest winter at 28.3° February 2018 was the warmest on record around the area with a first 80° at Newark .....NYC warmest February at 42.0°....ISP snowiest March at 31.9” of snow February 2017 featured 62° on 2-8 at ISP and 14.3” of snow on the 9th...2nd warmest February in NYC at 41.6° January 2017 produced 6.3” on the 7th in NYC and rose to 66° on the 12th..the month finished +5.4 December 2015 was warmest on record with a +13.3...50.3° in December....greatest snowstorm on record in NYC during January of 27.5” January 2006 was the 4th warmest in NYC at 40.9° followed by the 2nd biggest snowstorm in February of 26.9”

Every single model has a different storm evolution and solution for the 3-4th. Probably because it’s coming so soon behind the New Year’s Day storm. In general, models don’t handle storm details very well beyond 3-5 days out. Unless we are dealing with the Euro and Hurricane Sandy.

I think our best shot would be the upper low closing off like the Euro and GFS v16. Then we would need just the right amount of spacing between the New Years storm so the low doesn’t get suppressed. A perfect thread the needle would start warm and then transition colder. It would have to go off without a hitch due to the warmth after the New Years storm.

Pretty consistent pattern with the North American snow cover since October. Notice the big drops following the spikes back in October and mid-December. This tells us that it’s been a struggle to maintain the cold for more than brief periods.

If the past is any guide, then NYC may have to wait until later January or February for its next 6”+ snowstorm. There have been 9 years with a 6”+ event in NYC between December 1st and the 20th since 1930. The good news is that all of the 9 years did get at least one follow up warning level event. We would have to go back to 1926-1927 for the most recent year with no further 6”+ events in the season. NYC December 6”+ snowstorms before the solstice in December and the date of the next event 12-20-09......2-10-10 12-05-03.....1-27-04 12-5-02.......2-17-03 12-19-95.......1-7-96 12-11-60........1-19-61 12-3-57..........2-15-58 12-19-48.......2-28-49 12-19-45........2-20-46 12-18-32........2-11-33

2017 was the only cold December out of the last 10. That’s what it took to produce my favorite first week of January snowstorm over the last 10 years. That was the famous 950mb benchmark blizzard on 1-4-18. Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Departure Mean 40.6 +3.1 2020 40.0 ? 2019 38.3 +0.8 2018 40.1 +2.6 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

BGM may have experienced one of the quickest reductions in a 35”+ snow depth for the Northeast. It only took BGM 8 days to drop from 39” to 1”. The last time BGM had snow depth at 35” it lasted 16 days in March 1993. SNOW DEPTH RECORD SET AT BINGHAMTON NY... THE SNOW DEPTH THIS MORNING AT 7 AM WAS 39 INCHES. THE OLD RECORD WAS 35 INCHES ON MARCH 15 1993 AFTER A BLIZZARD. RECORDS HERE AT THE GREATER BINGHAMTON AIRPORT GO BACK TO 1951. 2020-12-17 22 15 18.5 -8.1 46 0 1.69 26.4 39 2020-12-18 22 8 15.0 -11.3 50 0 0.00 0.0 31 2020-12-19 24 3 13.5 -12.5 51 0 0.00 0.0 29 2020-12-20 31 21 26.0 0.2 39 0 0.14 1.8 26 2020-12-21 36 29 32.5 7.0 32 0 0.02 T 22 2020-12-22 34 27 30.5 5.3 34 0 0.01 0.1 22 2020-12-23 36 22 29.0 4.0 36 0 0.00 0.0 20 2020-12-24 50 34 42.0 17.2 23 0 1.55 0.0 19 2020-12-25 53 20 36.5 12.0 28 0 0.80 0.8 1 1993-03-15 21 0 10.5 -21.8 54 0 T T 35 1993-03-16 39 19 29.0 -3.6 36 0 0.00 0.0 32 1993-03-17 39 7 23.0 -10.0 42 0 0.21 1.0 26 1993-03-18 14 -3 5.5 -27.9 59 0 0.00 0.0 24 1993-03-19 31 -7 12.0 -21.7 53 0 0.00 0.0 24 1993-03-20 32 19 25.5 -8.6 39 0 0.04 0.7 20 1993-03-21 39 27 33.0 -1.5 32 0 0.28 3.9 25 1993-03-22 36 24 30.0 -4.9 35 0 T T 22 1993-03-23 37 18 27.5 -7.8 37 0 0.56 0.2 20 1993-03-24 40 32 36.0 0.3 29 0 0.10 0.0 18 1993-03-25 40 31 35.5 -0.6 29 0 T 0.0 16 1993-03-26 55 24 39.5 3.0 25 0 0.00 0.0 14 1993-03-27 58 30 44.0 7.1 21 0 0.00 0.0 12 1993-03-28 54 39 46.5 9.2 18 0 0.12 0.0 9 1993-03-29 47 42 44.5 6.8 20 0 0.40 0.0 6 1993-03-30 52 36 44.0 5.9 21 0 0.01 0.0 5 1993-03-31 60 31 45.5 6.9 19 0 0.01 0.0 3

Our warm up around the solstice has become the new normal for us. This is the first 10 consecutive years to reach 55° or warmer in NYC. It pushed the NYC December average temperature so far to 40° and +1.7. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Highest Max Temperature Dec 18 to Dec 25 Missing Count 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 2010-12-25 40 0 2009-12-25 39 0