donsutherland1

On Saturday, January 5, I noted that the idea of a warmer than normal winter has verified quite well in most areas with some exceptions. The main focus of that message concerned the increased likelihood of reduced snowfall amounts in parts of the East relative to what had been forecast. Now, as January concludes and two-thirds of meteorological winter have concluded, it its useful to look more closely at the details concerning the temperatures. Although the general idea of widespread warmth is on track, the magnitude of the warmth in areas has greatly exceeded the ideas cited. That includes eastern Canada, New England, the Middle Atlantic region, and parts of the Great Lakes region. One key error was the assumption of AO variability. Instead, the AO has been positive on 76% days so far and strongly positive on more than two-thirds of days during meteorological winter to date. Such an outcome in combination with a positive EPO tends to favor excessive warmth in parts of eastern North America, as has occurred. In contrast parts of western Canada and Alaska were colder to much colder than normal despite my thinking of warmth there. In large part, the early tendency for an EPO+ (which I thought would become more likely as the winter progressed) played a key role in that outcome. Below are the North American temperature anomalies for December 1, 2019 through January 29, 2020: Overall, the idea of widespread warmth was a good one. But no meaningful skill was shown when it came to delineating the magnitude of the warmth. Barriers to seasonal forecasting at a level of detail exist, because some of the key variables (particularly select teleconnections) cannot yet be forecast reliably beyond two weeks. Additional variables such as the risk of sudden stratospheric warming (SSW) events (none have occurred so far this winter) that could have a large impact cannot be forecast very well, in part because the dynamics are not well-understood. While a connection between wave-breaking (particularly Wave 2 exists), most such waves neither displace nor split the polar vortex and most don't lead to dramatic warming events that propagate downward. In addition, SSW events can also be driven from bottom-up in response to sustained periods of strong Atlantic blocking. These barriers likely explain part of the reason that the C3S multi-system seasonal forecast also significantly missed the magnitude of the warmth, even as its outlook was warmer than normal across much of North America. The three-month CFSv2 forecast for December-February from November (November 1-10 initial conditions) was more in line with CONUS temperature anomalies, but showed widespread cold in Canada and warmth in western Canada/Alaska. However, the forecast from the November 21-30 initial conditions had significantly trimmed the CONUS warmth.

Morning thoughts... 1. The Arctic Oscillation is now rebounding. Today's preliminary value was +1.489. The ensembles are in strong agreement that the AO will rise above +3.000 by the end of the first week of February. 2. No significant snowfalls (6" or greater) appear likely through at least the first week of February and possibly the first half of the month. Despite model mirages of digital snow that may pop up from time to time in the extended range, the forecast pattern (and patterns associated with strong AO+/PNA- setups) is inconsistent with those associated with significant or major snowstorms in the northern Middle Atlantic region. 3. February is poised to be warmer to possibly much warmer than normal. On the table is the possibility that New York City's 9th warmest January will be followed by a February that also rank among the 10 warmest on record. Prior cases with such an outcome were 1990, 1998, and 2002. 4. February snowfall amounts for those three cases were 1.8", 0.0", and Trace respectively. That would represent a reasonable worst-case idea. Nevertheless, it is likely that the month will feature below to perhaps much below normal snowfall for the snow-starved Middle Atlantic region. 5. Things could be worse. In Europe, where winter has been largely absent, January was concluding with another round of record warmth. Daily records included: Bonn: 59° (old record: 55°); Dresden: 54° (old record: 48°); Lyon: 63° (old record: 57°); Tenerife, Spain: 79° (old record: 71°); and, Zurich: 57° (old record: 55°). February will very likely be much warmer than normal in Europe, particularly in eastern Europe and western Russia.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 3.5 3.2 2.7 1.5 1.6 0.7 0.2 0.3 -1.0

There's a big difference between pointing out that the impacts of greenhouse gas forcing are influencing the hemispheric circulation (as noted in a growing body of literature), along with other aspects of internal variability, and making the claim that the ultimate outcome will be the disappearance of the NAO- (no literature that I am aware of supports such a claim, though there is some literature suggesting a somewhat greater frequency of the NAO+ state due, in part, to ocean-cryosphere-atmosphere changes).

Despite a slightly colder than normal to near normal day across the region, what will very likely become the 9th warmest January on record in New York City is now concluding. February will start mild with the first week of the month winding up warmer to perhaps much warmer than normal in the Middle Atlantic and southern New England areas. In a taste of deja vu, the February 1-7 mean temperature could average 40.0° or higher, much as it did during the January 1-7 period. In addition, little or no snow is likely in New York City, Newark, Philadelphia, and Washington, DC into at least the middle of the first week of February. Much of the Middle Atlantic and southern New England regions have seen below or much below normal seasonal snowfall to date. Seasonal snowfall totals to date include: Albany: 35.3" (1.1" above normal) Baltimore: 1.8" (8.1" below normal) Boston: 14.6" (7.8" below normal) Bridgeport: 10.1" (3.1" below normal) Hartford: 25.3" (4.4" above normal) Islip: 6.8" (5.6" below normal) New York City: 4.8" (7.0" below normal) Newark: 6.9" (6.5" below normal) Philadelphia: 0.3" (9.6" below normal) Providence: 11.6" (7.0" below normal) Washington, DC: 0.6" (7.6" below normal) Somewhat colder air could return late in the first week of February or just afterward. However, Arctic air is unlikely. During the coming weekend, a storm moving offshore will likely intensify rapidly as it moves into the waters off New England. However, little or no snow is likely for the New York City area. There remains some possibility that a light accumulation could occur over parts of Cape Cod. Based on the latest guidance, the likely seasonal snowfall distribution through January 31, will be < 20" at Boston; < 6" at New York City; < 3" at Philadelphia; and, < 2" at Washington, DC. There were 5 prior cases that met the above criteria for seasonal snowfall through January 31: 1895-96, 1918-19, 1931-32, 1949-50, and 1972-73. The single case with a colder than normal January (1895-96) saw 43.0" snow in the February-April period in New York City. All of the remaining four cases, all of which had a warmer than normal January, had less than 12.0" (mean: 4.6"; median 2.8"). Should blocking largely fail to develop in February, the risk of the very low snowfall for the remainder of winter 2019-20 would increase. 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 +7.78 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.489. Upper stratospheric warming will commence near the beginning of February and continue through February 7. Strong Wave 2 activity will occur during the first week of February driving the warming of the upper stratosphere. Overall, most of the stratosphere is forecast to remain cold on the EPS through at least the first week of February. On January 29, the MJO was in Phase 6 at an amplitude of 1.090 (RMM). The January 28-adjusted amplitude was 0.807. 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 39.1° in New York City. That would surpass the 38.6° monthly temperature from 1949 to make 2020 the 9th warmest January on record. The evolution of ENSO in combination with an AO+/EPO+ base state suggests that February will wind up warmer than normal in the Middle Atlantic region. Below normal snowfall is increasingly likely during February.

I'm not sure what impact the fires had, but will be looking to read papers that may be published on the topic. On the latter point, there is literature that suggests that the MJO is starting to spend increasing time in Phases 4-6 in response to changing oceanic heat content and SSTAs. I suspect that we will see such outcomes grow more frequent as the underlying factors driving that situation are persisting, namely continuing greenhouse gas emission increases.

The impact of greenhouse gas forcing on internal variability is becoming an increasingly researched area. One example from recent research: https://ui.adsabs.harvard.edu/abs/2017AGUFMGC41A1002M/abstract

November 15, 2018: 6.4"

Internal variability is occurring within the context of increased greenhouse gas forcing and its consequences. Almost certainly this interaction is leading to changes in patterns, pattern tendencies, and pattern evolution.

Great find. IMO, those who assume a static climate put themselves at greater risk of error in extended range and subseasonal forecasting where the risk of error is already high. The paper to which you posted a link referencing a longer residence of the MJO in the Maritime Continent phases is but one example. Bamwx deserves a lot of credit for being open to what the evidence is suggesting, even if it means changing forecasting approaches and questioning the premises deployed in making forecasts.

The 0z ECMWF showed temperatures around 60° in parts of the area: Source: Pivotal Weather

Morning thoughts... There is strong model consensus that the weekend storm will develop rapidly intensify too far from the region to have an impact on the New York City-Newark area. Little or now snow remains the most likely outcome. A growing number of variables are suggesting that February will wind up warmer than normal in the Middle Atlantic and southern New England regions. It will be interesting to see if these developments are reflected on the EPS weeklies when they become available this afternoon. Historic data for years with warmth similar to what is expected during the February 1-7 period have overwhelmingly seen warmer than normal monthly temperatures for February. Monthly snowfall was typically below normal. The only cases with near normal or greater snowfall were 1991, 2006, and 2008. In the former two cases, the month's largest snowfall coincided with PNA values above +1.250. In the latter case, the PNA was above +0.500.

Thanks.

What is the ACATT syndicate?

What will very likely become the 9th warmest January on record in New York City is now concluding. February will start mild with the first week of the month winding up warmer than normal in the Middle Atlantic and southern New England areas. In addition, little or no snow is likely in New York City, Newark, Philadelphia, and Washington, DC into at least the middle of the first week of February. Colder air could return late in the first week of February or just afterward. However, Arctic air is unlikely. 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. During the coming weekend, a storm moving offshore will likely intensify rapidly as it moves into the waters off New England. However, little or no snow is likely for the New York City area. Based on the latest guidance, the likely seasonal snowfall distribution through January 31, will be < 20" at Boston; < 6" at New York City; < 3" at Philadelphia; and, < 2" at Washington, DC. There were 5 prior cases that met the above criteria for seasonal snowfall through January 31: 1895-96, 1918-19, 1931-32, 1949-50, and 1972-73. The single case with a colder than normal January (1895-96) saw 43.0" snow in the February-April period in New York City. All of the remaining four cases, all of which had a warmer than normal January, had less than 12.0" (mean: 4.6"; median 2.8"). Should blocking largely fail to develop in February, the risk of the very low snowfall for the remainder of winter 2019-20 would increase. 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 +11.78 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.014. Upper stratospheric warming will commence near the beginning of February and continue through February 6. Strong Wave 2 activity will occur during the first week of February driving the warming of the upper stratosphere. Overall, most of the stratosphere is forecast to remain cold on the EPS through at least late in the first week of February, but the strong Wave 2 activity has increased the risk of warming that could propagate downward. On January 28, the MJO was in Phase 6 at an amplitude of 0.800 (RMM). The January 27-adjusted amplitude was 0.568. 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 39.1° in New York City. That would surpass the 38.6° monthly temperature from 1949 to make 2020 the 9th warmest January on record. The evolution 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. Below normal snowfall is increasingly likely during February.

Afternoon thoughts... 1. New York City's 9th warmest January is now nearing an end. 2. Seasonal snowfall to date will be below to much below normal through the end of January from Washington, DC to New York City. The expected spatial distribution of seasonal snowfall is consistent with winters that typically wind up with below to much below normal snowfall in the Middle Atlantic region. 3. The weekend storm will have little or no wintry impact on the region. Eastern New England could still get grazed, but even there any snowfall amounts would likely be light. 4. Some of the teleconnections forecasts point to the development of another strongly positive AO. Cases during which a strongly positive AO coincides with a generally positive EPO during the February 1-15 outcome typically result in a warmer than normal February in the region and below normal February-March snowfall. 5. Until there is credible and consistent evidence of a more favorable hemispheric pattern for signficant snowfalls, Day 10 mirages of the kind seen on today's 12z ECMWF that cruelly tease snow lovers will likely disappear with the passage of time. Sometimes such mirages will disappear with the next model cycle. Occasionally, there can be storms like the February 3-4, 1995 snowstorm that occur in a generally bad pattern, but those are the exception, not the norm.

Slightly cooler air has now moved 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 into the start of February. 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. During the weekend, a storm moving offshore will likely intensify rapidly as it moves into the waters off New England. The area with the highest chance of receiving at least a light snowfall will be eastern New England. There remains some uncertainty about the storm's track. Based on the latest guidance, the likely seasonal snowfall distribution through January 31, will be < 20" at Boston; < 6" at New York City; < 3" at Philadelphia; and, < 2" at Washington, DC. There were 5 prior cases that met the above criteria for seasonal snowfall through January 31: 1895-96, 1918-19, 1931-32, 1949-50, and 1972-73. The single case with a colder than normal January (1895-96) saw 43.0" snow in the February-April period in New York City. All of the remaining four cases, all of which had a warmer than normal January, had less than 12.0" (mean: 4.6"; median 2.8"). Should blocking largely fail to develop in February, the risk of the very low snowfall for the remainder of winter 2019-20 would increase. 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 +8.72 today. Today, the preliminary Arctic Oscillation (AO) figure was +0.127. Upper stratospheric warming will commence near the beginning of February and continue through February 5. Strong Wave 2 activity will occur during the first week of February driving the 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 27, the MJO was in Phase 6 at an amplitude of 0.568 (RMM). The January 26-adjusted amplitude was 0.448. 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.

It's disappointing. Hopefully, things will change, sooner rather than later.

Quick morning thoughts... 1. New York City remains solidly on course for January 2020 to become the 9th warmest January on record with a monthly mean temperature near 39.0°. 2. A weekend storm will likely bring little or no snow to the immediate New York City Metro Area. Eastern New England has the greatest chance of seeing a light or perhaps moderate snowfall as the storm rapidly deepens over the New England waters. 3. Since 1981, there have been 11 snowstorms that brought 6" or more snow to New York City in the February 1-15 timeframe. None had 250 mb winds over the Pacific Northwest rivaling those forecast by the latest guidance.

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.