donsutherland1

Following yesterday's mild readings, today saw readings remain well below normal across the region. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.4°C for the week centered around November 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.62°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was +7.16 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.496. No significant stratospheric warming appears likely through December 16. Wave 2 activity is forecast to remain suppressed and the stratosphere is forecast to remain cold through mid-month on the EPS. According to NCEP, the correlation of 16-day 10 mb GFS temperature forecasts is near 0.25 (much worse than flipping a coin). 5 mb forecasts have an even lower correlation. On December 6, the MJO was in Phase 2 at an amplitude of 0.854 (RMM). The December 5-adjusted amplitude was 0.631. The first week of December saw readings average more than 4° below normal across the northern Mid-Atlantic and southern New England regions. A more variable pattern is now poised to develop. There is a chance that the coming week could see one or more days with much above normal readings topping out in the 50s and perhaps even near 60° in the northern Mid-Atlantic region. Nevertheless, cold shots will continue to occur on a periodic basis. By December 15, the anomaly will likely be 1°-2° below normal. The third week of the month could turn colder and possibly for a more sustained period of time, especially if the EPO goes negative. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. The December 1-3 storm occurred with a negative PNA and Central Park received 1.6" snow. During the second half of December, larger snowstorms have occurred with a negative PNA.

Despite bright sunshine and a cloudless sky during the mid- and late-afternoon, the temperature in New York City reached a maximum reading of 38°. The snow from earlier in the week had almost completely disappeared from the landscape. At the New York Botanical Garden, the annual train show was underway. At the show were replicas of present and past New York City-area landmarks constructed out of wood and other natural materials. Four photos (three from inside the show for a flavor).

It’s a strong Arctic front. Hopefully, the record will fall.

The week 2-3 forecast on the CFSv2 (-3.5 degree C average anomaly) could be overdone. It’s an outlier relative to the other guidance.

Back on October 30, Social Media contained a forecast for an exceptionally cold pattern to lock in. https://www.americanwx.com/bb/topic/52511-autumn-2019-banter-thread/?do=findComment&comment=5338034 While there is always high uncertainty in the extended range, the probability of extreme patterns locking in for weeks at a time is relatively low (not zero, but low). Some examples include the exceptionally cold February of 2015 and the historically warm December of 2015. In general, one needs strong evidence to make such forecasts. At the time, the forecast state of the teleconnections argued against the outcome. Here's the forecast and the actual outcome: 11/16-30 temperatures for two select sites: NYC: 43.0° (2.3° below normal); ORD: Actual: 38.3° (0.6° above normal).

Ahead of another push of colder air, the temperature reached 50° in Central Park. Over the next 7-10 days, temperatures will exhibit wide variability. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.4°C for the week centered around November 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.62°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was +4.00 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.967. No significant stratospheric warming appears likely through December 15. Wave 2 activity is forecast to remain suppressed and the stratosphere is forecast to remain cold through mid-month on the EPS. According to NCEP, the correlation of 16-day 10 mb GFS temperature forecasts is near 0.25 (much worse than flipping a coin). 5 mb forecasts have an even lower correlation. On December 5, the MJO was in Phase 2 at an amplitude of 0.630 (RMM). The December 4-adjusted amplitude was 0.485. After a generally cold first week of December, warmer conditions will likely return. There is a chance that the second week of December could see one or more days with much above normal readings topping out in the 50s and perhaps even near 60° in the northern Mid-Atlantic region. Nevertheless, cold shots will continue to occur on a periodic basis. Moreover, the third week of the month could turn colder and possibly for a more sustained period of time, especially if the EPO goes negative. Despite the periodic cold shots and possible longer-duration period of cold, no snowstorms appear likely through at least the next 7-14 days in much of the region. Lake effect regions, upstate New York, and northern New England could see additional accumulations. The possibility could also exist for rain to end as a period of snow or flurries as storms depart and colder air returns. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. The December 1-3 storm occurred with a negative PNA and Central Park received 1.6" snow. During the second half of December, larger snowstorms have occurred with a negative PNA.

He may have misspoke. Fortunately, the 1.6” figure is listed in the climate record.

From the ECMWF's Copernicus Program: Globally, November 2019 was one of the three warmest Novembers on record, differing only marginally from November 2015 and 2016. Most land areas saw above average temperatures, with the exception of much of the eastern USA and Canada and a central Asian region extending from Siberia to the Iranian coast. Europe saw an autumn (September-November) temperature 1.1°C above the 1981-2010 average, a value that since at least 1979 has been exceeded only in 2006, 2015 and 2018. https://climate.copernicus.eu/surface-air-temperature-november-2019

Despite partly sunny skies, readings remained below normal across the Middle Atlantic and southern New England regions today. A brisk breeze added to the chill. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.4°C for the week centered around November 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.62°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was -8.15 today. Today, the preliminary Arctic Oscillation (AO) figure was +2.366. Daily MJO data has continued to be unavailable. Model initializations can provide a general idea of the MJO's progression and amplitude. After a generally cold first week of December, warmer conditions will likely return. There is a chance that the second week of December could see one or more days with much above normal readings topping out in the 50s and perhaps even near 60° in the northern Mid-Atlantic region. Nevertheless, cold shots will continue to occur on a periodic basis. Moreover, the third week of the month could turn colder and possibly for a more sustained period of time, especially if the EPO goes negative. Despite the periodic cold shots and possible longer-duration period of cold, no snowstorms appear likely through at least the next 7-14 days in much of the region. Lake effect regions, upstate New York, and northern New England could see additional accumulations. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. The December 1-3 storm occurred with a negative PNA and Central Park received 1.6" snow. During the second half of December, larger snowstorms have occurred with a negative PNA.

Under cloudy skies readings remained in the upper 30s and lower 40s across much of the Mid-Atlantic region. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.4°C for the week centered around November 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.62°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was -3.95 today. Today, the preliminary Arctic Oscillation (AO) figure was +2.722. Stratospheric temperatures remain below normal at both 10 mb and 30 mb in the Arctic region. No significant warming event is likely through at least December 13. Daily MJO data has continued to be unavailable. Model initializations can provide a general idea of the MJO's progression and amplitude. After a generally cold first week of December, warmer conditions will likely return. There is a chance that the second week of December could see one or more days with much above normal readings topping out in the 50s and perhaps even near 60° in the northern Mid-Atlantic region. However, the third week of the month could turn colder. There has been growing consensus toward a return of colder air on the guidance. It remains uncertain whether the cold will be transient or sustained for a period of time. Should the AO stay mainly positive or strongly positive, such cold shots would have an increased likelihood of proving relatively short-lived. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. The December 1-3 storm occurred with a negative PNA and Central Park received 1.6" snow. During the second half of December, larger snowstorms have occurred with a negative PNA.

I saw that the figure was reduced from the 7.1” (preliminary data summary) to 5.9”. The storm was really impressive around the Albany area.

The daily climate report issued at 5:08 pm lists 1.6" for the December total snowfall.

Overall, my forecast for the recent storm was a bad one. The worst outcomes were in the southern and western edge of the snowfall (Allentown and Philadelphia). Later and farther east development of the upper-level low contributed to this outcome. The historic tendency related to the PNA held true for the greater New York City area with 4" or more snowfalls during the first half of December being uncommon when the PNA is negative, as was the case this time around. Snowfall estimates and verification: Albany: 12"-18"; Total snowfall: 20.1" Allentown: 4"-8"; Total snowfall: Trace Binghamton: 8"-16"; Total Snowfall: 10.7" (within range) Boston: 5"-10"; Total Snowfall: 7.1" (within range) Bridgeport: 2"-4" (high uncertainty); Total snowfall: 2.8" (within range) Hartford: 6"-12"; Total snowfall: 16.4" Islip: 1"-3"; Total snowfall: 1.9" (within range) New York City: 3"-6"; Total snowfall: 1.6" Newark: 3"-6"; Total snowfall: 2.4" Philadelphia: 3"-6" (high uncertainty); Total snowfall: Trace Providence: 4"-8"; Total Snowfall: 5.5" (within range) Worcester: 8"-16"; Total snowfall: 17.0" In the wake of yesterday's snowfall, brilliant sunshine accompanied by a cold breeze prevailed. Overnight and tomorrow, a weak disturbance could touch off a few snow flurries and snow showers. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.4°C for the week centered around November 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.62°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was +9.08 today. Today, the preliminary Arctic Oscillation (AO) figure was +3.059. That is the highest figure since March 29, 2019 when the AO was +3.149. Daily MJO data has continued to be unavailable. Model initializations can provide a general idea of the MJO's progression and amplitude. After a generally cold first week of December, warmer conditions will likely return. There is a chance that the second week of December could see one or more days with much above normal readings topping out in the 50s and perhaps even near 60° in the northern Mid-Atlantic region. However, the third week of the month could turn colder. There has been growing consensus toward a return of colder air on the guidance. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. The December 1-3 storm occurred with a negative PNA and Central Park received 1.3" snow. During the second half of December, larger snowstorms have occurred with a negative PNA.

The New York Botanical Garden following the early December snowfall:

December (4.1° below normal in NYC) and January (0.9° below normal in NYC) were colder than normal in the region. February was exceptionally warm (Central Park set a monthly mean temperature record of 42.0° which surpassed the 41.6° average set just a year earlier).

No. I believe there will be transient cold shots and perhaps one or more opportunities for snowfall. Whether the closing week of the month turns colder remains to be seen.

Heaviest snow of the evening in Larchmont near the Long Island Sound.

East Grenville had 25.2” as of the last PNS.

A storm continues to bring some snow to the region this evening. Storm total accumulations include: Albany: 17.3"; Binghamton: 10.6"; Bridgeport: 0.7"; East Glenville, NY: 25.2"; Hartford: 5.5"; Highland Lakes, NJ: 10.5"; Islip: 0.2"; New York City: 1.0"; and, Newark: 1.4". The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.4°C for the week centered around November 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.62°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was +6.80 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.749. The preliminary PNA value was -0.108. Daily MJO data was unavailable. Outgoing long-wave radiation is currently unavailable according to Australia's Bureau of Meteorology (BOM). The BOM is working on the issue. After a generally cold first week of December, warmer conditions will likely return. There is a chance that the second week of December could see one or more days with much above normal readings topping out in the 50s and perhaps even near 60° in the northern Mid-Atlantic region. Overall, December will likely finish somewhat warmer than normal to warmer than normal across the region. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. During the second half of December, larger snowstorms have occurred with a negative PNA.

Large flakes of snow are now falling in the Bronx.

A complex, long-duration, two-part winter storm is now affecting the region. Just outside New York City, the first snowfall of the season whitened the ground. Storm total snowfall amounts so far include: Albany: 2.8" Allentown: Trace Binghamton: 0.2" Bridgeport: Trace Hartford: 1.4" New York City: Trace Newark: 0.1" More significant snow could develop later tomorrow as the vigorous upper-level low associated with the system swings eastward and rapidly develops. The guidance has been in good agreement with the development of an intense band of snow. Model disagreement persists with the exact placement of the band. New York City (Central Park) and Newark continue to appear in line for a general 3"-6" snowfall. On account of the aforementioned band of intense snowfall, either or both locations could see notably less or notably more snow. The exact amounts might not become clear with a high degree of confidence until overnight. The following storm total amounts are likely for select cities in the Middle Atlantic and southern New England regions: Albany: 12"-18" Allentown: 4"-8" Binghamton: 8"-16" Boston: 5"-10" Bridgeport: 2"-4" (high uncertainty) Hartford: 6"-12" Islip: 1"-3" Philadelphia: 3"-6" (high uncertainty) Providence: 4"-8" Worcester: 8"-16"　 Following its warmest autumn by far, Utqiagvik (formerly Barrow) is currently on course to register its first annual mean temperature of 20.0° or above. That city's warmest year on record was 2016 with an annual average temperature of 18.9°. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was +0.7°C for the week centered around November 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.63°C and the ENSO Region 3.4 anomaly has averaged +0.68°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was +4.10 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.109. Daily MJO data was unavailable. Outgoing long-wave radiation is currently unavailable according to Australia's Bureau of Meteorology (BOM). The BOM is working on the issue. After a generally cold first week of December, warmer conditions will likely return. There is a chance that the second week of December could see one or more days with much above normal readings topping out in the 50s and perhaps even near 60° in the northern Mid-Atlantic region. Overall, December will likely finish somewhat warmer than normal to warmer than normal across the region. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. During the second half of December, larger snowstorms have occurred with a negative PNA.

This afternoon the sleet turned to a burst of snow in Larchmont, NY in southern Westchester County. As of 2:30 pm, the snow had yielded to sleet.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.5 0.8 0.5 1.5 2.0 2.2 1.2 0.5 0.2

I took regional snowfall to date as one piece of information for some context, which added a degree of confidence to my thinking. That suggested that the numbers could be plausible. The major assumptions largely drove the forecast.

I hope that they are low, too. Personally, I found the snowfall estimates that came up quite dissatisfying. I would prefer a notably snowier winter.