donsutherland1

The 12/15/2022 12z EPS clusters:

A complex storm will continue to bring a cold rain to coastal regions tomorrow. Some of the rain could be heavy. A general 0.50"-1.50" with locally higher amounts is likely. Interior sections could see some additional accumulating snow. An area of moderate to significant snowfall is likely across central Pennsylvania to central New York State. The latest EPS weeklies continue to suggest that near normal to below normal temperatures could prevail during the December 19-26 and December 27-January 2 periods. No severe cold is likely through at least the first three weeks of December. Afterward, as the PNA goes neutral, the prospect for snowfall and more significant cold could increase. Already, the guidance is showing an increased change of snow for the December 22-24 timeframe. The AO fell reached -4.000 on December 10th. Since 1950, there were 11 cases that saw the AO reach -4.000 or below during December. Mean snowfall for those cases was 9.0" (Median: 9.1"). 64% of such cases saw 6" or more of snowfall in December while 45% of such cases saw 10.0" or more snow. In contrast, during all other December cases, mean December snowfall was 3.5" (Median: 2.5"). 91% of those cases also saw a colder than normal December in the northern Middle Atlantic region. In terms of seasonal snowfall, 64% of those seasons saw 30" or more snowfall in New York City with 45% having 40" or more. Just 18% of such cases had less than 20" seasonal snowfall, both of which had less than 10" for the December-January period. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -1.0°C for the week centered around December 7. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.23°C and the ENSO Region 3.4 anomaly has averaged -0.95°C. La Niña conditions will likely persist through mid-winter. The SOI was +4.15 today. The preliminary Arctic Oscillation (AO) was -3.216 today. December 1-15 has experienced the strongest AO block on record for the first half of December. The AO averaged a preliminary -2.908 (old record: -2.138, 1985) with 8 days at or below -3.000 (old record: 6 days, 1966). On December 13 the MJO was in Phase 4 at an amplitude of 0.743 (RMM). The December 12-adjusted amplitude was 1.070 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 71% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 37.9° (1.2° below normal).

I use them all the time. There's also a 1000 mb cluster scenario. Here's what the two largest clusters look like for 12/23 (the first with 19 members has a Miller B-type scenario and probably comprises all 9 of the individual members showing 10" or more snow in the NYC-EWR areas; the second large group is very unfavorable for the coastal plain). I flipped the charts so it is easier to view North America.

Morning thoughts… Clouds will increase and a soaking rain will arrive. Snow changing to rain will overspread interior sections. High temperatures will reach the lower and perhaps middle 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 42° Newark: 44° Philadelphia: 47° The rain will continue tomorrow. Some interior sections could see additional snowfall. Normals: New York City: 30-Year: 44.3°; 15-Year: 45.1° Newark: 30-Year: 44.8°; 15-Year: 45.7° Philadelphia: 30-Year: 46.0°; 15-Year: 47.0°

Tomorrow, a complex storm will bring a cold rain to coastal regions into Friday. Some of the rain could be heavy. A general 0.50"-1.50" is likely. Interior sections could see accumulating snow before a changeover. The potential exists for a moderate to perhaps significant snowfall from central Pennsylvania across central New York State. The latest EPS weeklies continue to suggest that near normal to below normal temperatures could prevail during the December 19-26 and December 27-January 2 periods. No severe cold is likely through at least the first three weeks of December. Afterward, as the PNA goes neutral, the prospect for snowfall and more significant cold could increase. Reflecting the rising probability of snowfall, about 50% of the 12z EPS ensemble members currently show 1" or more snowfall for New York City during the December 23-24 period. The AO fell reached -4.000 on December 10th. Since 1950, there were 11 cases that saw the AO reach -4.000 or below during December. Mean snowfall for those cases was 9.0" (Median: 9.1"). 64% of such cases saw 6" or more of snowfall in December while 45% of such cases saw 10.0" or more snow. In contrast, during all other December cases, mean December snowfall was 3.5" (Median: 2.5"). 91% of those cases also saw a colder than normal December in the northern Middle Atlantic region. In terms of seasonal snowfall, 64% of those seasons saw 30" or more snowfall in New York City with 45% having 40" or more. Just 18% of such cases had less than 20" seasonal snowfall, both of which had less than 10" for the December-January period. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -1.0°C for the week centered around December 7. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.23°C and the ENSO Region 3.4 anomaly has averaged -0.95°C. La Niña conditions will likely persist through mid-winter. The SOI was +1.61 today. The preliminary Arctic Oscillation (AO) was -3.136 today. On December 12 the MJO was in Phase 4 at an amplitude of 1.066 (RMM). The December 11-adjusted amplitude was 1.307 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 62% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 38.3° (0.8° below normal).

The Block that "Disappointed" During December 13-29, 1950, a period of exceptionally strong Atlantic blocking coincided with a positive PNA. Although the number of measurable snowfall events wound up above historic climatology for the period, there were no major snowstorms in the Philadelphia to New York City area. There was a light to moderate event on December 26 as Arctic air poured into the region. There was a "near miss" on December 29, as a storm developed offshore but readings were too warm for snowfall. On January 7, 1951, Boston picked up 7.6" of snow. This period of strong blocking occurred during a La Niña. It offers a reminder that even patterns that are often associated with heavy snowfall can wind up with less snowy outcomes. The outcome of what lies ahead for December 2022 remains to be determined. This short analysis is not a prediction of any kind of how the current blocking episode will unfold as the PNA moves toward neutral and then positive levels during the closing 7-10 days of the month. Although, the December 15-16 storm won't deliver snowfall to the Philadelphia to Boston region, another storm could bring precipitation during the December 23-24 period. Below are some statistics from New York City and charts from the December 13-29, 1950 blocking episode.

Morning thoughts… Today will be mostly sunny but cold. High temperatures will reach the upper 30s and lower 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 40° Newark: 42° Philadelphia: 42° A soaking rain will develop tomorrow in the coastal plain. Interior sections will likely see snow changing to rain. Normals: New York City: 30-Year: 44.6°; 15-Year: 45.3° Newark: 30-Year: 45.1°; 15-Year: 46.0° Philadelphia: 30-Year: 46.3°; 15-Year: 47.2°

Tonight will be another fair and cold night. By Thursday, a complex storm could bring a cold rain or snow changing to rain to coastal regions into Friday. Interior sections could see accumulating snow before any changeover. The potential exists for a moderate to perhaps significant snowfall from central Pennsylvania across central New York State. The latest EPS weeklies continue to suggest that near normal to below normal temperatures could prevail during the December 19-26 and December 27-January 2 periods. No severe cold is likely through at least the first three weeks of December. Afterward, as the PNA goes neutral, the prospect for snowfall and more significant cold could increase. The AO fell reached -4.000 on December 10th. Since 1950, there were 11 cases that saw the AO reach -4.000 or below during December. Mean snowfall for those cases was 9.0" (Median: 9.1"). 64% of such cases saw 6" or more of snowfall in December while 45% of such cases saw 10.0" or more snow. In contrast, during all other December cases, mean December snowfall was 3.5" (Median: 2.5"). 91% of those cases also saw a colder than normal December in the northern Middle Atlantic region. In terms of seasonal snowfall, 64% of those seasons saw 30" or more snowfall in New York City with 45% having 40" or more. Just 18% of such cases had less than 20" seasonal snowfall, both of which had less than 10" for the December-January period. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -1.0°C for the week centered around December 7. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.23°C and the ENSO Region 3.4 anomaly has averaged -0.95°C. La Niña conditions will likely persist through mid-winter. The SOI was -0.58 today. The preliminary Arctic Oscillation (AO) was -3.854 today. On December 11 the MJO was in Phase 4 at an amplitude of 1.306 (RMM). The December 10-adjusted amplitude was 1.394 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 58% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 38.5° (0.6° below normal).

You can currently access it at chat.openai.com

The probability of snowfall (measurable and significant) is notably higher than climatology during strong blocking patterns, especially when the PNA is positive at this time of year (and all of January). Higher probabilities are not guarantees. While the extreme blocking during 2010-2011 led to a big December blizzard and very snowy 30 days albeit after a long wait from late November, there have been cases where strong blocking did not produce such an outcome. Winter 1958-1959 is one such example. That the AO is forecast to remain negative through much or all of the remainder of December and the PNA will slowly move to somewhat positive levels in the closing 7-10 days of December--a slow move illustrated by the statistical guidance--suggests at least a window of opportunity with increased potential. Certainly, the forecast pattern is much better than a warm EPO+/AO+ pattern that all but assures little or no meaningful prospects for snowfall. It is also noted that the EPS weeklies that came out yesterday continued to show colder than normal weather during December 19-26. They also flipped to a colder outcome for the following week, as well. The CFSv2 has now moved into general agreement with the EPS weeklies, after having shown unbroken warmth in the East through December. Finally, since ChatGPT, an AI language model has garnered significant press coverage in recent days, I asked it to construct a poem that captures the sentiments of some of us who are eagerly awaiting or hoping for a big snowfall. Here's what it produced: The snowstorm is coming, they say It's just a matter of time But as the days go by And the skies remain clear and blue I can't help but wonder If this storm will ever arrive I wait and watch As the world goes on around me People bustling, living their lives But I am stuck in this state of anticipation Hoping for the snow to fall I long to see the world blanketed in white To hear the gentle crunch of snow underfoot To feel the cold embrace of winter But it seems that it will never come And so I wait Patiently, restlessly Hoping that one day The storm will arrive And I can finally experience The joy of a big snowfall.

Morning thoughts… Today will be mostly sunny but cold. High temperatures will reach the upper 30s and lower 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 39° Newark: 41° Philadelphia: 42° The cool but dry weather will continue through midweek. Normals: New York City: 30-Year: 44.9°; 15-Year: 45.6° Newark: 30-Year: 45.4°; 15-Year: 46.2° Philadelphia: 30-Year: 46.6°; 15-Year: 47.5°

Tonight will be fair and cold. By Thursday, a complex storm could bring a cold rain or snow changing to rain to coastal regions into Friday. Interior sections could see accumulating snow before any changeover. The potential exists for a significant snowfall from central Pennsylvania across central New York State. The latest EPS weeklies continue to suggest that near normal to below normal temperatures could prevail during the December 19-26 and December 27-January 2 periods. No severe cold is likely through at least the first three weeks of December. Afterward, as the PNA goes neutral, the prospect for snowfall and more significant cold could increase. The AO fell reached -4.000 on December 10th. Since 1950, there were 11 cases that saw the AO reach -4.000 or below during December. Mean snowfall for those cases was 9.0" (Median: 9.1"). 64% of such cases saw 6" or more of snowfall in December while 45% of such cases saw 10.0" or more snow. In contrast, during all other December cases, mean December snowfall was 3.5" (Median: 2.5"). 91% of those cases also saw a colder than normal December in the northern Middle Atlantic region. In terms of seasonal snowfall, 64% of those seasons saw 30" or more snowfall in New York City with 45% having 40" or more. Just 18% of such cases had less than 20" seasonal snowfall, both of which had less than 10" for the December-January period. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -1.0°C for the week centered around December 7. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.23°C and the ENSO Region 3.4 anomaly has averaged -0.95°C. La Niña conditions will likely persist through mid-winter. The SOI was -7.11 today. The preliminary Arctic Oscillation (AO) was -3.854 today. On December 10 the MJO was in Phase 4 at an amplitude of 1.390 (RMM). The December 9-adjusted amplitude was 1.513 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 55% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 38.7° (0.4° below normal).

Yes. February 2010. On February 6, the AO fell to -5.205. Afterward, it rose to -4.266 on February 10. On February 14, it bottomed out again at -5.132.

227 NOUS41 KOKX 121321 PNSOKX CTZ005>012-NJZ002-004-006-103>108-NYZ067>075-078>081-176>179-130121- Public Information Statement National Weather Service New York NY 821 AM EST Mon Dec 12 2022 ...SNOWFALL REPORTS... Location Amount Time/Date Provider ...Connecticut... ...Fairfield County... 4 NNW New Fairfield 3.3 in 0430 AM 12/12 Trained Spotter Shelton 2.4 in 0755 PM 12/11 Cocorahs 3 E New Fairfield 2.2 in 0855 PM 12/11 Public Bethel 2.0 in 0700 PM 12/11 Public Ridgefield 1.5 in 0500 PM 12/11 Amateur Radio Bridgeport Airport 0.8 in 0700 AM 12/12 Official NWS Obs Norwalk 0.5 in 0720 PM 12/11 Broadcast Media ...Middlesex County... Clinton 1.7 in 0220 AM 12/12 Broadcast Media Westbrook 1.6 in 1140 PM 12/11 Trained Spotter ...New Haven County... Hamden 3.6 in 0700 AM 12/12 Trained Spotter 1 E North Haven 3.0 in 1115 PM 12/11 Trained Spotter North Haven 2.5 in 0730 PM 12/11 Trained Spotter Seymour 2.0 in 0751 PM 12/11 Trained Spotter Guilford 1.8 in 0800 PM 12/11 Trained Spotter 1 SW Branford 1.6 in 0700 AM 12/12 Trained Spotter ...New London County... Groton 2.3 in 0600 AM 12/12 Trained Spotter ...New Jersey... ...Bergen County... 2 NNE Franklin Lakes 2.8 in 1245 AM 12/12 Trained Spotter 1 WSW Washington Township 0.5 in 0600 PM 12/11 Trained Spotter Mahwah 0.3 in 0315 PM 12/11 Trained Spotter ...Essex County... North Caldwell 0.5 in 0540 PM 12/11 Trained Spotter ...Hudson County... Harrison 0.2 in 0230 AM 12/12 CO-OP Observer ...Passaic County... Wayne 0.7 in 0530 PM 12/11 Public ...Union County... Newark Airport 0.1 in 0700 AM 12/12 Official NWS Obs ...New York... ...Bronx County... 1 NW Fordham 0.9 in 0600 AM 12/12 Public ...Nassau County... Manhasset Hills 0.3 in 0800 AM 12/12 Public ...New York County... Central Park T in 0700 AM 12/12 Official NWS Obs ...Orange County... Walden 4.4 in 0940 PM 12/11 Public 2 WNW Monroe 4.0 in 1130 AM 12/11 Trained Spotter 2 SSW Stewart Airport 4.0 in 0155 AM 12/12 Public Monroe 3.5 in 0520 AM 12/12 Trained Spotter 3 NNE Unionville 3.2 in 0936 PM 12/11 Public Newburgh 3.0 in 0830 PM 12/11 Public 1 WNW Monroe 3.0 in 0920 PM 12/11 Trained Spotter Middletown 2.0 in 0400 PM 12/11 Trained Spotter Walden 1.9 in 0400 PM 12/11 CO-OP Observer ...Queens County... NYC/La Guardia 0.4 in 0700 AM 12/12 Official NWS Obs NYC/JFK T in 0700 AM 12/12 Official NWS Obs ...Rockland County... Chestnut Ridge 2.1 in 1245 AM 12/12 Public ...Suffolk County... North Babylon 0.4 in 0645 AM 12/12 Public Islip Airport 0.4 in 0700 AM 12/12 Official NWS Obs West Islip 0.3 in 0350 AM 12/12 Trained Spotter Upton 0.3 in 0700 AM 12/12 Official NWS Obs ...Westchester County... 1 SW White Plains Airport 2.0 in 1030 PM 12/11 Trained Spotter 1 NW New Rochelle 1.1 in 0700 AM 12/12 Public Mamaroneck 0.5 in 0920 PM 12/11 Trained Spotter &&

LaGuardia: 0.4" Newark: 0.1" Central Park and JFK: Trace

The morning after the snowfall:

Morning thoughts… Clouds will give way to partly sunny skies. It will be cool. High temperatures will reach the upper 30s and lower 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 40° Newark: 42° Philadelphia: 44° The cool but dry weather will continue through midweek. Normals: New York City: 30-Year: 45.2°; 15-Year: 45.8° Newark: 30-Year: 45.7°; 15-Year: 46.5° Philadelphia: 30-Year: 46.9°; 15-Year: 47.7°

Through 4 pm snowfall totals include: Albany: 3.9" Allentown: Trace Binghamton: 4.1" (tied record set in 1992) Bridgeport: Trace New York City: Trace Newark: Trace A system will continue to bring wet snow to parts of the region into early tomorrow. Areas to the north and west of New York City and Newark could see a coating of snow. Poughkeepsie could see 2"-4" of snow and Port Jervis could pick up 3"-6". A sustained colder pattern is currently developing. The latest EPS weeklies continue to suggest that near normal to below normal temperatures could prevail during the December 19-26 period. No severe cold is likely through at least the first three weeks of December. Afterward, as the PNA goes neutral, the prospect for snowfall and more significant cold could increase. The AO fell reached -4.000 on December 10th. Since 1950, there were 11 cases that saw the AO reach -4.000 or below during December. Mean snowfall for those cases was 9.0" (Median: 9.1"). 64% of such cases saw 6" or more of snowfall in December while 45% of such cases saw 10.0" or more snow. In contrast, during all other December cases, mean December snowfall was 3.5" (Median: 2.5"). 91% of those cases also saw a colder than normal December in the northern Middle Atlantic region. In terms of seasonal snowfall, 64% of those seasons saw 30" or more snowfall in New York City with 45% having 40" or more. Just 18% of such cases had less than 20" seasonal snowfall, both of which had less than 10" for the December-January period. The ENSO Region 1+2 anomaly was -0.5°C and the Region 3.4 anomaly was -1.0°C for the week centered around November 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.42°C and the ENSO Region 3.4 anomaly has averaged -0.95°C. La Niña conditions will likely persist through mid-winter. The SOI was -0.78 today. The preliminary Arctic Oscillation (AO) was -4.238 today. On December 9 the MJO was in Phase 4 at an amplitude of 1.511 (RMM). The December 8-adjusted amplitude was 1.417 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 55% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 38.8° (0.3° below normal).

From Goshen, NY:

First snow flurries of the season.

Morning thoughts… Today will be cloudy with a cold rain in coastal sections and wet snow inland. Poughkeepsie will likely see 2”-4 of snow into tomorrow morning. Port Jervis will likely see 3”-6”. High temperatures will reach the upper 30s and lower 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 41° Newark: 43° Philadelphia: 44° Precipitation will end tomorrow and the clouds will break. Normals: New York City: 30-Year: 45.5°; 15-Year: 46.1° Newark: 30-Year: 46.0°; 15-Year: 46.8° Philadelphia: 30-Year: 47.1°; 15-Year: 48.0°

The latest HREF guidance:

Uncertainty about the possible late next week event is unusually high. For perspective, the current 500 mb pattern for the AO-/PNA- setup resembles none of the patterns for the prior December AO -3.5 or below/PNA- cases.

A system could bring some rain or perhaps wet snow to parts of the region tomorrow into Monday. Areas to the north and west of New York City and Newark could see a coating of snow. Poughkeepsie could see 1"-3" of snow and Port Jervis could pick up 3"-6". As had been indicated with the development of the current EPO-/AO-/PNA- pattern, the potential for snowfall has begun to increase. The 500 mb pattern is highly anomalous for December cases with severe Atlantic blocking, so uncertainty remains higher than normal when it comes to snowfall potential. A sustained colder pattern is currently developing. The latest EPS weeklies continue to suggest that near normal to below normal temperatures could prevail during the December 19-26 period. No severe cold is likely through at least the first three weeks of December. The AO fell reached -4.000 on December 10th. Since 1950, there were 11 cases that saw the AO reach -4.000 or below during December. Mean snowfall for those cases was 9.0" (Median: 9.1"). 64% of such cases saw 6" or more of snowfall in December while 45% of such cases saw 10.0" or more snow. In contrast, during all other December cases, mean December snowfall was 3.5" (Median: 2.5"). 91% of those cases also saw a colder than normal December in the northern Middle Atlantic region. In terms of seasonal snowfall, 64% of those seasons saw 30" or more snowfall in New York City with 45% having 40" or more. Just 18% of such cases had less than 20" seasonal snowfall, both of which had less than 10" for the December-January period. The ENSO Region 1+2 anomaly was -0.5°C and the Region 3.4 anomaly was -1.0°C for the week centered around November 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.42°C and the ENSO Region 3.4 anomaly has averaged -0.95°C. La Niña conditions will likely persist through mid-winter. The SOI was +16.71 today. The preliminary Arctic Oscillation (AO) was -4.068 today. During December 1-10, the AO has averaged a preliminary -2.591. That is the lowest December 1-10 average on record. The prior mark was -2.297, which was set in 1985. On December 8 the MJO was in Phase 4 at an amplitude of 1.416 (RMM). The December 7-adjusted amplitude was 1.147 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 55% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 38.8° (0.3° below normal).

Morning thoughts… Today will be partly to mostly sunny and cool. High temperatures will reach the lower and middle 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 41° Newark: 43° Philadelphia: 45° A system will bring rain and snow to parts of the region late tomorrow into Monday. Some areas could see a light accumulation. Normals: New York City: 30-Year: 45.8°; 15-Year: 46.4° Newark: 30-Year: 46.3°; 15-Year: 47.1° Philadelphia: 30-Year: 47.4°; 15-Year: 48.3°