donsutherland1

Slightly cooler air is moving into the region. Nevertheless, temperatures will generally run somewhat above normal through the remainder of January and into the start of February. Little or no snow is likely in New York City, Newark, Philadelphia, and Washington, DC through the rest of January. Colder air could return late in the first week in February or just afterward. Arctic air is unlikely. Moreover, the cold could be transient. As long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 such storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall will likely exist for central and upstate New York and central and northern New England. Boston would have a higher probability of receiving a moderate or significant snowfall than Baltimore, New York City, Newark, Philadelphia, and Washington, DC. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.3°C for the week centered around January 22. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.10°C and the ENSO Region 3.4 anomaly has averaged +0.48°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 Anomaly < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates); EPO+ subset: NYC: 40.5°; Philadelphia: 40.8° (n=57 dates) ENSO R1+2 Anomaly < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 Anomaly > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates); EPO+ subset: NYC: 41.2°; Philadelphia: 42.0° (n=18 dates) ENSO R1+2 Anomaly > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was -0.56 today. Today, the preliminary Arctic Oscillation (AO) figure was +0.700. Upper stratospheric warming will commence near the beginning of February and continue through February 4. Strong Wave 2 activity will occur during the first week of February. This activity will produce warming of the upper stratosphere. Overall, most of the stratosphere is forecast to remain cold on the EPS into the first days of February, but the strong Wave 2 activity has increased the risk of warming that could propagate downward. On January 26, the MJO was in Phase 6 at an amplitude of 0.448 (RMM). The January 25-adjusted amplitude was 0.724. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of a warmer than normal January. The monthly mean temperature could finish near 39.0° in New York City. That would surpass the 38.6° monthly temperature from 1949 to make 2020 the 9th warmest January on record. The combination of ENSO in combination with an AO+/EPO+ base state suggests that February will wind up warmer than normal in the northern Mid-Atlantic region.

I did, too. They're a great resource.

A "KU" snowstorm is a storm of the kind featured in Paul Kocin and Louis Uccellini's research on Northeast snowstorms. They wrote a two-volume work on the storms: https://www.amazon.com/Northeast-Snowstorms-1-2-Set/dp/1878220640

Temperatures again topped out in the middle and upper 40s across the region. Even as slightly cooler air is likely in coming days, temperatures will generally run above normal through the remainder of January and into the start of February. Little or no snow is likely in New York City, Newark, Philadelphia, and Washington, DC through the rest of January. Colder air could return late in the first week in February or just afterward. Arctic air is unlikely. Moreover, the cold could be transient. As long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 such storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall will likely exist for central and upstate New York and central and northern New England. Boston would have a higher probability of receiving a moderate or significant snowfall than Baltimore, New York City, Newark, Philadelphia, and Washington, DC. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.4°C for the week centered around January 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged +0.52°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 Anomaly < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates); EPO+ subset: NYC: 40.5°; Philadelphia: 40.8° (n=57 dates) ENSO R1+2 Anomaly < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 Anomaly > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates); EPO+ subset: NYC: 41.2°; Philadelphia: 42.0° (n=18 dates) ENSO R1+2 Anomaly > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was -1.50 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.165. No significant stratospheric warming event appears likely through February 3. Wave 2 activity will continue to increase during the first week of February, especially in the upper stratosphere. This activity will produce warming of the upper stratosphere. Overall, most of the stratosphere is forecast to remain cold on the EPS into the first days of February. On January 25, the MJO was in Phase 7 at an amplitude of 0.653 (RMM). The January 24-adjusted amplitude was 1.201. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of a warmer than normal January. The monthly mean temperature could finish near 39.0° in New York City. That would surpass the 38.6° monthly temperature from 1949 to make 2020 the 9th warmest January on record. The combination of ENSO in combination with an AO+/EPO+ base state suggests that February will wind up warmer than normal in the northern Mid-Atlantic region.

Winter forecast update... To date, the idea of a warmer than normal winter has verified quite well. Overall, in much of the CONUS, the warmth has been greater than suggested. Exceptions are eastern Canada where it has also been warmer than normal and Alaska where it has been colder than normal. One key scenario for lower seasonal snowfall, primarily for the Middle Atlantic and southern New England areas, was a predominantly positive to strongly positive Arctic Oscillation (AO). Through January 25, the AO had been positive on 75% days and +1.000 or above on 68% days. A second key scenario of lower seasonal snowfall was the MJO's staying disproportionately in Phases 4, 5, and 6. Of the 30 days this winter during which the MJO had an amplitude of 1.000 or above, the MJO was in Phases 4-6 57% of the time. That is well above the near 38% figure for equal frequency for each of the MJO's eight phases. Based on the guidance and expected pattern through January 31, New York City will likely have less than 6" seasonal snow by the end of January. Since 1869, there have been 34 such cases. In 24 (71%), seasonal snowfall finished under 20" in New York city. In just 4 (12%) cases, seasonal snowfall finished at or above 30". In 7 (21%) cases, seasonal snowfall finished under 10". The mean figure was 16.7". The mean February-April figure was 13.1". The January 16-31 AO is likely to finish at an average of +1.000 or above. Since 1950, there have been 10 such cases. Mean February-April snowfall in New York City was 13.0" (Median: 10.4"). Based on the outcomes, there would be an implied 70% probability that winter 2019-2020 would finish with less than 20" snow in Central Park, which is almost identical to the historic frequency for cases when seasonal snowfall through January 31 was less than 6". In addition, the likely seasonal snowfall distribution through January 31, was overwhelmingly associated with much less than average seasonal snowfall in the Middle Atlantic region. There were 5 prior cases that met the following criteria for seasonal snowfall through January 31: Boston: < 20"; New York City: < 6"; Philadelphia: < 3"; and Washington, DC: < 2": 1895-96, 1918-19, 1931-32, 1949-50, and 1972-73. Mean snowfall amounts for those cases were: Boston: 24.1"; New York City: 14.4"; Philadelphia: 5.9"; and, Washington, DC: 4.2". Winter 1895-96 saw much above normal snowfall in March in Boston leading to 38.7" seasonal snowfall and in New York City resulting in 46.3" seasonal snowfall. Winter 1895-96 was the only winter in the above set to have a colder than normal January in the East. Overall, the spatial distribution of snowfall to date is consistent with a lower snowfall scenario across much of the Middle Atlantic region. I have adjusted my snowfall amounts for the following cities: Atlanta: 0.5" or less (through 1/25: None) Baltimore: 4"-12" (through 1/25: 1.8") Binghamton: 65"-80" (through 1/25: 37.3") New York City: 12"-22" (through 1/25: 4.8") Newark: 14"-24" (through 1/25: 6.9") Philadelphia: 4"-12" (through 1/25: 0.3") Richmond: < 6" (through 1/25: 1.0") Scranton: 30"-45" (through 1/25: 18.2") Sterling: 4"-12" (through 1/25: 2.9") Washington, DC: 2"-8" (through 1/25: 0.6") What could lead to higher amounts: 1. Prolonged deep blocking (AO of -1.000 or below) 2. The MJO's persistently being in Phases 7, 8, 1, and 2 at a high amplitude 3. The borderline to weak El Niño would strengthen appreciably by the middle of February What could lead to lesser amounts: 1. A persistently positive AO coupled with a strongly negative SOI 2. The MJO's persistently being in Phases 4, 5, and 6 at a high amplitude 3. The MJO's reaching an amplitude of 2.500 or above for an extended period of time The amounts for all the other cities remain unchanged from the initial figures.

Rain from today's storm was moving into New England this evening. Through 6 pm, rainfall amounts included: Allentown: 1.40"; Atlantic City: 0.81"; Bridgeport: 0.85"; Harrisburg: 1.48"; Islip: 0.80"; New York City: 0.85"; Newark: 0.88"; Philadelphia: 1.60"; Scranton: 1.23"; and, White Plains: 1.20". Following the storm, readings will remain above normal for the season. Temperatures will generally run above normal through the remainder of January and into the start of February. Little or no snow is likely in New York City, Newark, Philadelphia, and Washington, DC through the rest of the month. Colder air could return late in the first week in February or just afterward. Arctic air is unlikely and the cold could be transient. As long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 such storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall will likely exist for central and upstate New York and central and northern New England. Boston would have a higher probability of receiving a moderate or significant snowfall than Baltimore, New York City, Newark, Philadelphia, and Washington, DC. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.4°C for the week centered around January 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged +0.52°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 Anomaly < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates); EPO+ subset: NYC: 40.5°; Philadelphia: 40.8° (n=57 dates) ENSO R1+2 Anomaly < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 Anomaly > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates); EPO+ subset: NYC: 41.2°; Philadelphia: 42.0° (n=18 dates) ENSO R1+2 Anomaly > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was +4.34 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.403. No significant stratospheric warming event appears likely through February 2. Wave 2 activity will likely increase near the end of January leading to at least some warming of the upper stratosphere. Overall, most of the stratosphere is forecast to remain cold on the EPS into the start of February. On January 24, the MJO was in Phase 7 at an amplitude of 1.120 (RMM). The January 23-adjusted amplitude was 1.813. The MJO had recently spent 9 consecutive days at an amplitude of 3.000 or above. There have been only 8 cases where the MJO had an amplitude of 3.000 or above for 7 or more consecutive days. The shortest period from the start of that stretch that saw the MJO's amplitude fall below 1.000 was 20 days. The mean period was 36 days. The longest period was 55 days. Based on this historic experience, the MJO likely won't reach low amplitude until near or after the end of January. Since 1974, there were 8 prior cases where the MJO reached Phase 4 at an amplitude of 1.500 or above in the January 5-20 period. In 7 or 88% of those cases, the MJO progressed into Phases 7 and 8. The MJO moved into Phase 7 on January 20. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of a warmer than normal January. The monthly mean temperature could finish near 39.0° in New York City. That would surpass the 38.6° monthly temperature from 1949 to make 2020 the 9th warmest January on record. The combination of ENSO in combination with an AO+/EPO+ base state suggests that February will wind up warmer than normal in the northern Mid-Atlantic region.

Four photos from today’s rainstorm during which White Plains received 0.61” in an hour and 1.20” through 5 pm:

30 year averages are rising. It has been exceptionally warm in Europe and the warmth is likely to continue for some time.

Morning thoughts... At 9 am, rain was moving into the New York City Metro Area. As of 9 am, rainfall totals included: Baltimore: 1.47"; Philadelphia: 0.59"; and, Washington, DC: 1.33". A widespread 0.50"-1.50" rainfall with some locally higher amounts remains on track for the region. Meanwhile, ENSO and teleconnections developments have continued to evolve toward a scenario where a milder February may now be more likely than a colder one. During February, the ENSO Region 3.4 anomaly will likely average 0.00°C to +0.75°C. The most recent 6-week moving average is +0.52°C. During February, both the AO and EPO will likely remain predominantly positive. The AO has been positive on 75% days this winter to date, including 68% during which it was +1.000 or above. This ENSO-teleconnections combination typically favors a warmer than normal February. Late yesterday (18z GEFS) and overnight (0z EPS/0z and 6z GEFS) now show the trough shifting to the west and potential ridge development in the East near the end of their timeframes. In addition, the CFSv2 has been steadily evolving toward a milder solution in the East. Most recent CFSv2 forecasts:

Temperatures will likely run above normal through the remainder of January and into the start of February. Little or no snow is likely in New York City, Newark, Philadelphia, and Washington, DC for the remainder of the month. Colder air could return late in the first week in February or just afterward. As long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 such storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall will likely exist for central and upstate New York and central and northern New England. Boston would have a higher probability of receiving a moderate or significant snowfall than Baltimore, New York City, Newark, Philadelphia, and Washington, DC. A storm will likely bring 0.50" to 1.50" rain to Washington, DC to Boston tomorrow into perhaps part of Sunday. A moderate snowfall with perhaps some locally significant amounts could occur across upstate New York, northern New England, and parts of southern Ontario (north and east of Toronto). The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.4°C for the week centered around January 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged +0.52°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 Anomaly < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates) ENSO R1+2 Anomaly < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 Anomaly > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates) ENSO R1+2 Anomaly > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was +10.32 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.237. No significant stratospheric warming event appears likely through February 1. Wave 2 activity could increase near the end of January leading to some warming of the upper stratosphere. Overall, most of the stratosphere is forecast to remain cold on the EPS into the start of February. On January 23, the MJO was in Phase 7 at an amplitude of 1.812 (RMM). The January 22-adjusted amplitude was 2.109. The MJO had recently spent 9 consecutive days at an amplitude of 3.000 or above. There have been only 8 cases where the MJO had an amplitude of 3.000 or above for 7 or more consecutive days. The shortest period from the start of that stretch that saw the MJO's amplitude fall below 1.000 was 20 days. The mean period was 36 days. The longest period was 55 days. Based on this historic experience, the MJO likely won't reach low amplitude until near or after the end of January. Since 1974, there were 8 prior cases where the MJO reached Phase 4 at an amplitude of 1.500 or above in the January 5-20 period. In 7 or 88% of those cases, the MJO progressed into Phases 7 and 8. The MJO moved into Phase 7 on January 20. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of a warmer than normal January. The monthly mean temperature could finish near 39.0° in New York City. That would surpass the 38.6° monthly temperature from 1949 to make 2020 the 9th warmest January on record.

That was the control. The control is, to be charitable, not the best guide for such forecasts.

Some evening thoughts... Based on the latest teleconnections forecasts, it continues to appear that the pattern will remain largely unfavorable for moderate or significant snowfalls in the Philadelphia to New York City area through the end of January. There is little uncertainty about Saturday's storm. That system will bring rain to the big cities of the Middle Atlantic region. The probability of widespread moderate or significant snowfall across central New York State and central New England has fallen. Moderate to locally significant amounts remain possible in parts of upstate New York and northern New England. The guidance is in good agreement about this outcome. Another storm could impact the region near the start of February. As the prospect of a more neutral AO has fallen over the past day, so has the probability of a moderate or significant snowfall on the Mid-Atlantic region's coastal plain. Given the latest ensemble forecast (+1.000 or above), a significant snowfall for such cities as Philadelphia and New York appears unlikely. During the January 15-February 15, 1950-2019 period New York City saw 56 storms bring 4" or more snow to New York City. Just 13% of such storms occurred when the AO was +1.000 or above and 9% occurred when the AO was +1.500 or above. For Philadelphia, there were 45 such storms. The respective percentage for an AO of +1.500 or above was 13%, and for an AO of +1.500 or above, it was 11%. The 12z ECMWF's outlook showing little or no snow for New York City and Philadelphia through the remainder of January is consistent with historic outcomes associated with the current strongly positive AO. All said, it still appears that seasonal snowfall through January will likely be less than 6" in New York City and less than 1" in Philadelphia. Current totals to date are 4.8" and 0.3" respectively. Today is also Atlanta's record 675th day without even a trace of snow. Colder air could arrive late in the first week of February or during the second week of the month as a trough develops in the East.

Under partly sunny skies, temperatures rebounded into the middle and upper 40s across the northern Mid-Atlantic region. Temperatures will likely run above normal through the remainder of January and into the start of February. Colder air could return late in the first week in February or just afterward. As long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 such storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall will likely exist for central and upstate New York and central and northern New England. The pattern could begin to grow more favorable for snow on the coastal plain during the beginning of February should the Arctic Oscillation (AO) fall toward neutral levels. Before then, a storm could bring 0.50" to 1.50" precipitation, mostly or all rain, to Washington, DC to Boston this weekend. A moderate snowfall with some locally significant amounts could occur across upstate New York, northern New England, and parts of southern Ontario (north and east of Toronto). The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.4°C for the week centered around January 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged +0.52°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 Anomaly < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates) ENSO R1+2 Anomaly < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 Anomaly > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates) ENSO R1+2 Anomaly > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was +0.05 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.494. Through January 23, the AO has averaged +1.467 for meteorological winter. That's the 5th highest average on record for the December 1-23 period. No significant stratospheric warming event appears likely through January 31. Wave 2 activity could increase near the end of January. Overall, most of the stratosphere is forecast to remain cold on the EPS. On January 22, the MJO was in Phase 7 at an amplitude of 2.108 (RMM). The January 21-adjusted amplitude was 2.045. The MJO had recently spent 9 consecutive days at an amplitude of 3.000 or above. There have been only 8 cases where the MJO had an amplitude of 3.000 or above for 7 or more consecutive days. The shortest period from the start of that stretch that saw the MJO's amplitude fall below 1.000 was 20 days. The mean period was 36 days. The longest period was 55 days. Based on this historic experience, the MJO likely won't reach low amplitude until near or after the end of January. Since 1974, there were 8 prior cases where the MJO reached Phase 4 at an amplitude of 1.500 or above in the January 5-20 period. In 7 or 88% of those cases, the MJO progressed into Phases 7 and 8. The MJO moved into Phase 7 on January 20. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of a warmer than normal January. The monthly mean temperature could finish near 39.0° in New York City. The probability that January 2020 will finish with among the 10 highest January average temperatures on record has increased to near 65%. The 10th warmest January occurred in 1906 with a monthly mean temperature of 38.4°. The 9th warmest January was January 1949 with an average temperature of 38.6°. Boston, which set a January record high temperature of 74° on January 12, has had an even warmer January relative to climatology. Boston could have among the five warmest Januaries on record. The 5th warmest January there was January 2002 with a mean temperature of 36.7°. The 4th warmest January was 37.4° in 1937.

After a cold start, especially outside the City where temperatures fell into the teens with some single digits (Danbury reported a 6° low and Poughkeespie had a minimum temperature of 7°), temperatures rose into the upper 30s in the region. Temperatures will likely run above normal through the remainder of January. However, a mild finish to a very warm January does not mean that February will likely be warmer than normal. The coefficient of determination for New York City between the January and February temperatures is just 0.07. Records go back to 1869. Colder air could return during or just after the first week in February. As long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 such storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall will likely exist for central and upstate New York and central and northern New England. The pattern could begin to grow more favorable for snow on the coastal plain during the beginning of February should the Arctic Oscillation (AO) fall toward neutral levels. Before then, a storm could bring 0.50" to 1.50" precipitation, mostly or all rain, to Washington, DC to Boston this weekend. A moderate snowfall with some locally significant amounts could occur across central and upstate New York, central and northern New England, and parts of southern Ontario. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.4°C for the week centered around January 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged +0.52°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 Anomaly < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates) ENSO R1+2 Anomaly < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 Anomaly > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates) ENSO R1+2 Anomaly > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was -6.17 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.544. No significant stratospheric warming event appears likely through January 30. Wave 2 activity will remain relatively suppressed. Overall, most of the stratosphere is forecast to remain cold on the EPS. On January 21, the MJO was in Phase 7 at an amplitude of 2.044 (RMM). The January 20-adjusted amplitude was 2.153. The MJO had recently spent 9 consecutive days at an amplitude of 3.000 or above. There have been only 8 cases where the MJO had an amplitude of 3.000 or above for 7 or more consecutive days. The shortest period from the start of that stretch that saw the MJO's amplitude fall below 1.000 was 20 days. The mean period was 36 days. The longest period was 55 days. Based on this historic experience, the MJO likely won't reach low amplitude until near or after the end of January. Since 1974, there were 8 prior cases where the MJO reached Phase 4 at an amplitude of 1.500 or above in the January 5-20 period. In 7 or 88% of those cases, the MJO progressed into Phases 7 and 8. The MJO moved into Phase 7 on January 20. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of a warmer than normal January. The monthly mean temperature could finish near 39.0° in New York City. The probability that January 2020 will finish with among the 10 highest January average temperatures on record has increased to just over 60%. The 10th warmest January occurred in 1906 with a monthly mean temperature of 38.4°. The 9th warmest January was January 1949 with an average temperature of 38.6°.

For early February reference, below are the 500 mb height anomalies for snowstorms that brought 6" or more snow to Boston, New York City, and Philadelphia (all 3 locations) during the February 1-15, 1950-2019 period. Storms that commenced prior to February 1 or continued after February 15 are excluded. One typically found a Greenland-Hudson Bay block and/or a PNA+ ridge coupled with a trough in the East. The variation on a case-by-case basis should also be noted.

Some quick morning thoughts... It has been a warm and dry January so far in the Mid-Atlantic region. Through January 21, precipitation in New York City is 1.06" (1.47" below normal) and in Philadelphia it is 1.00" (1.05" below normal). The combination of limited precipitation and limited cold has led to very low monthly snowfall amounts so far (2.3" in New York City and 0.2" in Philadelphia). A storm will likely bring a moderate to perhaps significant amount of precipitation (0.50" - 1.50") to the region this weekend, but the major cities of the Mid-Atlantic region will likely see little or no snow. Philadelphia will likely finish January with less than 1" snow for the season and New York City will likely finish with less than 6". As January nears an end, there remains no credible evidence of the kind of "shock" that could bring significant change to the hemispheric circulation. The Polar Vortex is likely to remain strong with a predominant positive AO. The EPO looks to remain positive. The stratosphere looks to remain cool. As a result, February could begin on a mild note. Cold could still arrive near the end of the first week of February or just afterward, but such cold likely won't be severe. At the same time, the risk that February as a whole could wind up on the warm side of normal has increased. That's not yet the most likely outcome, but it's a scenario that cannot be dismissed.

Warmer conditions will likely develop starting tomorrow. No exceptional warmth appears imminent, but readings will likely run above normal through the remainder of January. A mild finish to a very warm January does not mean that February will likely be warmer than normal. The coefficient of determination for New York City between the January and February temperatures is just 0.07. Records go back to 1869. Colder air could return during or just after the first week in February. As long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 such storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall will likely exist for central and upstate New York and central and northern New England. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.4°C for the week centered around January 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged +0.52°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 Anomaly < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates) ENSO R1+2 Anomaly < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 Anomaly > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates) ENSO R1+2 Anomaly > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was -3.62 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.483. No significant stratospheric warming event appears likely through January 29. Wave 2 activity will remain relatively suppressed. Overall, most of the stratosphere is forecast to remain cold on the EPS. On January 20, the MJO was in Phase 7 at an amplitude of 2.152 (RMM). The January 19-adjusted amplitude was 2.644. The MJO had recently spent 9 consecutive days at an amplitude of 3.000 or above. There have been only 8 cases where the MJO had an amplitude of 3.000 or above for 7 or more consecutive days. The shortest period from the start of that stretch that saw the MJO's amplitude fall below 1.000 was 20 days. The mean period was 36 days. The longest period was 55 days. Based on this historic experience, the MJO likely won't reach low amplitude until near or after the end of January. Since 1974, there were 8 prior cases where the MJO reached Phase 4 at an amplitude of 1.500 or above in the January 5-20 period. In 7 or 88% of those cases, the MJO progressed into Phases 7 and 8. The MJO moved into Phase 7 on January 20. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of a warmer than normal January. The monthly mean temperature could finish near 38.5° in New York City. The probability that January 2020 will finish with among the 10 highest January average temperatures on record has increased to just over 50%. The 10th warmest January occurred in 1906 with a monthly mean temperature of 38.4°. The 9th warmest January was January 1949 with an average temperature of 38.6°.

IMO, the boundaries you suggest are good. In fact, there are some people who live in Pike County but commute to NYC despite the distance. Also, I think a fuller discussion, even when New York City is likely to receive less than an inch of snow is better than a more limited one. I hope you continue posting as you currently post. The discussions are invaluable.

The March 2019 events were two separate ones.

6.4" fell on November 15, 2018 creating significant travel problems, as the City was caught unprepared for the snow.

It depends on the kind of ENSO event. A strong basin-wide event would likely lead to warmth absent strong blocking.

In general, an El Niño leads to a more active subtropical jet stream and a northward displacement of the polar jet stream. That's the general idea, but differences exist, because differences in anomalies in each of the El Niño Southern Oscillation (ENSO Regions) have an impact. Major ENSO Regions, from East to West, are Region 1+2, Region 3, Region 3.4, and Region 4. Often, when the El Niño is Central Pacific-based (Region 3.4 anomaly > Region 1+2 anomaly), the subtropical jet is active, but the polar jet is not displaced as far to the north as would be the case in an East-based or basin-wide El Niño event. Therefore, one often sees above average snowfall in the Northeast. Here's a useful link that explains El Niño: https://www.climate.gov/news-features/understanding-climate/el-niño-and-la-niña-frequently-asked-questions Here's a good link to take a look at El Niño impacts: https://www.climate.gov/news-features/understanding-climate/climategovs-most-requested-el-niño-and-la-niña-images One should keep in mind, other variables can interact with El Niño producing different outcomes. For example, extreme Atlantic blocking during a strong El Niño during winter 2009-10 led to a colder than normal winter overall with very high seasonal snowfall.

Beyond two weeks, they typically don't fare better than climatology.

For the second time this month, the temperature fell to 20° in New York City. Tonight, readings approach and possibly fall just below 20° in Central Park. Following another chilly day tomorrow, warmer conditions will likely develop. Somewhat colder air could return during the closing days of January, but the risk that January could end on a mild note has increased. A mild finish to a very warm January does not mean that February will likely be warmer than normal. The coefficient of determination for New York City between the January and February temperatures is just 0.07. Colder air could return during or just after the first week in February. In addition, so long as the Arctic Oscillation remains strongly positive, the risk of widespread significant snow (6" or greater) from Washington, DC to Boston remains low. Since 1950, there were 11 storms that brought 6" or more snow to 2 or more of the following cities: Boston, New York City, Philadelphia, and Washington, DC. Just 1 storm occurred when the AO was +1.000 or above. Therefore, through most of the remainder of January, the greatest risk of moderate or significant snowfall would likely exist for central and upstate New York and central and northern New England. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.4°C for the week centered around January 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.22°C and the ENSO Region 3.4 anomaly has averaged +0.52°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. For February 1981-2019, the following monthly temperature averages were recorded for cases when the ENSO Region 3.4 anomaly averaged 0.00°C to +0.75°C: ENSO R1+2 < 0: AO+: NYC: 36.9°; Philadelphia: 37.6° (n=101 dates) ENSO R1+2 < 0: AO-: NYC: 34.7°; Philadelphia: 34.9° (n=97 dates) ENSO R1+2 > 0: AO+: NYC: 35.7°; Philadelphia: 36.6° (n=82 dates) ENSO R1+2 > 0: AO-: NYC: 30.9°; Philadelphia: 31.6° (n=58 dates) February 1981-2019: NYC: 35.8°; Philadelphia: 36.0° The SOI was +2.93 today. Today, the preliminary Arctic Oscillation (AO) figure was +1.687. No significant stratospheric warming event appears likely through January 28. Wave 2 activity will remain relatively suppressed. Overall, most of the stratosphere is forecast to remain cold on the EPS. On January 19, the MJO was in Phase 6 at an amplitude of 2.646 (RMM). The January 18-adjusted amplitude was 2.909. The MJO had recently spent 9 consecutive days at an amplitude of 3.000 or above. There have been only 8 cases where the MJO had an amplitude of 3.000 or above for 7 or more consecutive days. The shortest period from the start of that stretch that saw the MJO's amplitude fall below 1.000 was 20 days. The mean period was 36 days. The longest period was 55 days. Based on this historic experience, the MJO likely won't reach low amplitude until near or after the end of January. Since 1974, there were 8 prior cases where the MJO reached Phase 4 at an amplitude of 1.500 or above in the January 5-20 period. In 7 or 88% of those cases, the MJO progressed into Phases 7 and 8. Based on sensitivity analysis applied to the latest guidance, New York City has an implied 99% probability of a warmer than normal January. The monthly mean temperature could finish near 38.0° in New York City. The probability that January 2020 will finish with among the 10 highest January average temperatures on record has increased to just over 40%.

Thanks for sharing this interesting research.