donsutherland1

Sleet has started falling in parts of southern Westchester County.

For now, I am. I will review tonight’s and tomorrow’s guidance for any changes given the differences that still exist among the models.

The 12/1/2019 0z RGEM:

That's the GGEM. The RGEM comes out earlier.

Another nice run by the RGEM. More model runs to come later this evening.

New York City finished November with a monthly mean temperature of 43.9°. That made 2019 the coldest November since 2012 when the average temperature was also 43.9°. A significant long-duration, two-part winter storm will impact the region Sunday into Tuesday morning. While some snow and sleet could fall in the New York City area on Sunday (with accumulating snow well to the north and west of the City), a larger-impact snowfall is possible Monday into late Monday night as the vigorous upper-level low associated with the system swings eastward and rapidly develops. The 18z GFS did not develop this low along the lines of the other guidance and is likely providing a bad solution for both coastal and interior regions of New York State and southern New England. New York City (Central Park) and Newark continue to appear in line for a general 3"-6" snowfall. While model solutions have varied widely for NYC, 40/51 (78%) EPS members show 3" or more snow for New York City. Therefore, the above range still appears reasonable. Locations such as Binghamton, Poughkeepsie and Albany could see 8"-16". Utqiagvik (formerly Barrow) experienced its warmest autumn on record by far with an estimated seasonal mean temperature of 28.7°. There remains a chance that the final figure could be 28.8° depending on today's minimum temperature, which could occur near midnight Alaska time. The previous record was 26.0°, which was set in 2016. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was +0.7°C for the week centered around November 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.63°C and the ENSO Region 3.4 anomaly has averaged +0.68°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was +0.38 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.491. Daily MJO data was unavailable. Outgoing long-wave radiation is currently unavailable according to Australia's Bureau of Meteorology (BOM). The BOM is working on the issue. Based on the consistently-modeled idea of a negative to strongly negative EPO (-2.000 to -1.000) to begin December, the first 7 days of December will likely average colder than normal in much of the eastern third to eastern half of the CONUS and southern Canada. However, the EPO will likely go positive and the AO could go strongly positive during the first week of December. As a result, warmer conditions will likely return after the first week in December. Overall, December will likely finish somewhat warmer than normal to warmer than normal across the region. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. During the second half of December, larger snowstorms have occurred with a negative PNA.

It will soon initialize.

Big differences in outcomes among the guidance illustrate the considerable uncertainty that still exists.

Here are some quick instructions. Also, the "Local" feature isn't available for all models.

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

The 0z NAM did little to undermine my initial thoughts posted earlier that New York City (Central Park) and Newark appear to be in line for a general 3"-6" snowfall. Locations such as Poughkeepsie and Albany could see 8"-16". The NAM exceeds those amounts, especially in and around Albany. The rest of the guidance will be interesting. It's still a high-risk storm as a relatively small shift in track and or evolution of the upper level low could make a large difference in and around NYC and probably in nearby Nassau County.

A significant long-duration, two-part winter storm will impact the region Sunday into Tuesday morning. While some snow and sleet could fall in the New York City area on Sunday (with accumulating snow well to the north and west of the City), a larger-impact snowfall is possible Monday into late Monday night as the vigorous upper-level low associated with the system swings eastward and rapidly develops. The forecast 500 mb pattern for December 2 bears similarities to that of December 24, 2002. The key difference is that the trough on the East Coast is forecast to be south of where it was in 2002. For now, New York City (Central Park) and Newark appear to be in line for a general 3"-6" snowfall. Locations such as Poughkeepsie and Albany could see 8"-16". In northern Alaska, Utqiagvik (formerly Barrow) is concluding its warmest autumn on record with what will likely be its second warmest November on record with a mean temperature near 16.0°. Based on the latest guidance, Utqiagvik will likely have a September-November mean temperature ranging of 28.6°. The current record is 26.0°, which was set in 2016. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was +0.7°C for the week centered around November 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.63°C and the ENSO Region 3.4 anomaly has averaged +0.68°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was -3.38 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.408. Daily MJO data was unavailable. Outgoing long-wave radiation is currently unavailable according to Australia's Bureau of Meteorology (BOM). The BOM is working on the issue. Based on the consistently-modeled idea of a negative to strongly negative EPO (-2.000 to -1.000) to begin December, the first 7 days of December will likely average colder than normal in much of the eastern third to eastern half of the CONUS and southern Canada. However, the EPO will likely go positive and the AO could go strongly positive during the first week of December. As a result, warmer conditions will likely return after the first week in December. At present, the warmth does not appear to be too impressive. Transient shots of cooler air will remain possible. Should the AO remain elevated at strongly positive levels, the probability of a warmer than normal second half of December would increase. Overall, the base case remains a somewhat warmer than normal December as a whole, though New England and the Great Lakes region could still wind up cooler than normal. With December likely to get off to a cool start, Newark, New York City, and Boston will likely see their first measurable snowfall of the season during December 1-3. Philadelphia could also pick up its first measurable snowfall. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. During the second half of December, larger snowstorms have occurred with a negative PNA. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of experiencing a colder than normal November. November 2019 will likely finish with a mean temperature near 43.9°. That would make this November the coldest November since 2012 when the monthly mean temperature also was 43.9°. There is a chance that the mean temperature could come in at 43.8°. If so, November 2019 would be the coldest November since 1996 when the monthly average temperature was 43.0°. 　

Albany also picked up 21”.

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

Prospects for an appreciable snowfall in and around the New York City Metro Area increased overnight. The single teleconnections fly in the ointment remains the forecast of a negative PNA. Most of the early December snowstorms that dumped 4" or more snow in the New York City area occurred when the PNA was positive. Nevertheless, such a snowfall remains among the plausible scenarios. The last time New York City received 2" or more snow was March 3-4, 2019 when 5.0" fell. Following the snowfall, several days of below to much below normal temperatures are likely before warmer air returns following the first week in December. Some of the latest guidance has grown warmer in the extended range.

Thanksgiving Day featured a bountiful harvest of winds that buffeted much of the Middle Atlantic and southern New England regions. The 12z ECMWF gave much of the region a lot to be thankful for with its forecast of a major snowfall early next week. While the ECMWF might be overdone, the pattern is conducive for at least some snowfall, even in the big cities, especially from late Monday into Tuesday morning. In northern Alaska, Utqiagvik (formerly Barrow) is concluding its warmest autumn on record with what will likely be its second warmest November on record. Through 5 pm Alaska time, Utqiagvik had a daily high temperature of 27°, which was just short of the daily record of 28° from 1995. Based on the latest guidance, Utqiagvik will likely have a September-November mean temperature ranging from 28.5°-28.6°. The current record is 26.0°, which was set in 2016. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was +0.7°C for the week centered around November 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.63°C and the ENSO Region 3.4 anomaly has averaged +0.68°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was -9.23 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.754. Daily MJO data was unavailable for November 27. Outgoing long-wave radiation is currently unavailable according to Australia's Bureau of Meteorology (BOM). The BOM is working on the issue. Based on the consistently-modeled idea of a negative to strongly negative EPO (-2.000 to -1.000) to begin December, the first 7 days of December will likely average colder than normal in much of the eastern third to eastern half of the CONUS and southern Canada. However, the EPO will likely go positive and the AO could go strongly positive during the first week of December. As a result, warmer conditions will likely return after the first week in December. At present, the warmth does not appear to be too impressive. Transient shots of cooler air will remain possible. Should the AO remain elevated at strongly positive levels, the probability of a warmer than normal second half of December would increase. Overall, the base case remains a somewhat warmer than normal December as a whole, though New England and the Great Lakes region could still wind up cooler than normal. With December likely to get off to a cool start, Newark, New York City, and Boston will likely see their first measurable snowfall of the season during December 1-3. Philadelphia could also pick up its first measurable snowfall. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of experiencing a colder than normal November. November 2019 will likely finish with a mean temperature near 44.0°. That would make this November the coldest November since 2012 when the monthly mean temperature was 43.9°.

For those who are interested, recent shifting forecasts on the CFSv2. First, November CFSv2 forecasts and the November 1-25 temperature anomalies: The December 2019 forecasts:

Overall, with last night's runs, I think Newark and New York City and their immediate suburbs remain on track for their first measurable snowfall of the season (likely a minor accumulation). A few individual EPS members are big hits (10" or more). The Hudson Valley, northwest New Jersey/northeastern Pennsylvania, and southeastern New York (e.g., Sullivan County) should do well.

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

During September, the ENSO Region 1+2 anomaly fell below -1.00°C for multiple weeks. Since 1950, only a single El Niño winter (2002-03) followed a September with one such week. Therefore, based on a combination of the current guidance and historical ENSO data, the underlying ENSO assumption for winter 2019-2020 is a neutral (warm) ENSO state. There could be periods where the ENSO Region 3.4 anomaly is somewhat above +0.5°C, but the winter average should be neutral. For much of the winter the Region 1+2 anomaly should be negative. The September-October ENSO Region 1+2 anomaly was -0.82°C. Since 1950, 12/16 (75%) cases when the Region 1+2 anomaly averaged -0.99°C to -0.50°C had a predominantly negative PDO. In fact, the PDO fell to -0.45 in October. The last time the PDO was negative for a month was November 2018 when it was -0.05. A negative PDO winter favors a negative PNA. Since 1950, there were five years that saw the AO average -1.000 or below in November and -1.500 or below during the second half of November. Out of the total of 15 months that followed, the AO averaged < 0 during 12 (80%) and -0.500 or below during 10 (67%). This data suggests at least somewhat above average frequency of AO blocking for winter 2019-2020. However, winters during which the AO rises to +3.000 or above in December typically have less frequent blocking. Therefore, the assumption is that there will be periods of blocking and periods where blocking is absent. The NAO appears to have transitioned to a predominantly positive state. A generally positive NAO has also been modeled on the seasonal guidance. The core assumption is a positive NAO. The large pool of warm SSTAs south of Alaska has been cooling gradually in recent weeks. Warm SSTAs in that region have often been a precursor of a predominantly negative Eastern Pacific Oscillation (EPO). Based on this trend, the first half of winter 2019-2020 may see more frequent EPO blocking than the second half. Key Assumptions: 1. Neutral-warm ENSO 2. Generally positive NAO 3. Negative to somewhat positive PDO 4. AO variability 5. EPO variability with a tendency toward more positive values later in the winter. A composite temperature anomaly map is below (DJF 1950-51 through DJF 2018-19): The multi-model (C3S)outlook is below: Additional factors to be considered include the observed ongoing warming occurring in the Arctic region. Based on all of the above factors (including some weight being placed on the seasonal climate models), my estimated December-February temperature thinking is: Colder than normal (1.0° to 2.0° below normal): Eastern Canada (eastern Ontario, Quebec, Labrador, New Brunswick, Newfoundland, Nova Scotia, PEI) Near Normal (0.5° below normal to 0.5° above normal): Desert Southwest, Great Lakes Region, New England Somewhat above normal (0.5° to 1.5° above normal): Middle Atlantic Region, Plains States, West Coast, Canada (except for Eastern Canada and Northwest Canada) Warmer than Normal (1.0° to 3.0° above normal): Southeast Much Warmer than Normal (More than 3.0° above normal): Alaska, Northwest Canada (Yukon) Select seasonal snowfall estimates are below: Albany: 60"-70” Atlanta: 0.5"-2.5" Baltimore: 10”-20” Binghamton: 80”-90” Boston: 30”-40” Buffalo: 100”-110” Burlington: 80”-90” Chicago: 25”-35” Detroit: 30”-40” Nashville: 5”-10” New York City: 20”-30” Newark: 20”-30” Philadelphia: 10”-20” Providence: 25”-35” Richmond: 5”-10” Scranton: 45”-55” Sterling: 10”-20” Washington, DC: 7”-17” 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 ENSO Region 3.4 anomaly falling to somewhat negative values as the winter progresses 4. A mainly negative NAO What could lead to lesser amounts: 1. The development of 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. Dramatic warming in ENSO Region 1+2

Despite clouds and some widely scattered showers, temperatures again rose into the upper 50s and lower 60s in the Middle Atlantic and southern New England regions. In the wake of a cold front, tomorrow will turn partly sunny, cooler with strong winds that could gust past 40 mph in much of the region. Some areas could experience gusts near 50 mph. Wind advisories may need to be extended to the New York City Metro Area tomorrow. In northern Alaska, Utqiagvik (formerly Barrow) is concluding its warmest autumn on record with what will likely be its second warmest November on record. Based on the latest guidance, Utqiagvik will likely have a September-November mean temperature ranging from 28.4°-28.6°. The current record is 26.0°, which was set in 2016. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was +0.7°C for the week centered around November 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.63°C and the ENSO Region 3.4 anomaly has averaged +0.68°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20. The SOI was -7.26 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.754. Daily MJO data was unavailable for November 26. Outgoing long-wave radiation is currently unavailable according to Australia's Bureau of Meteorology (BOM). The BOM is working on the issue. Based on the consistently-modeled idea of a negative to strongly negative EPO (-2.000 to -1.000) to begin December, the first 7 days of December will likely average colder than normal in much of the eastern third to eastern half of the CONUS and southern Canada. However, the EPO will likely go positive and the AO could go strongly positive during the first week of December. As a result, warmer conditions will likely return after the first week in December. At present, the warmth does not appear to be too impressive. Transient shots of cooler air will remain possible. As a milder pattern develops in the CONUS, Europe will likely see the cold give way to the pattern that has predominated in November where Scandinavia is colder than normal while much of Europe is warmer than normal. Overall, the base case remains a somewhat warmer than normal December as a whole, though New England and the Great Lakes region could still wind up cooler than normal. Should the AO have a sustained period of strongly positive levels, the risk of greater warmth than described above would increase. With December likely to get off to a cool start, the potential for at least some snowfall in the Philadelphia to Boston area could exist. The first such opportunity could occur during the December 1-3 timeframe. Although the season's first measurable snowfall is possible in New York City and Newark, amounts will likely be minor. When it comes to New York City's 4" or greater snowstorms the PNA is more important than the AO during the first half of December. Since 1950, December 1-15 has seen 10 storms bring 4.0" or more snow to New York City. 50% occurred with an AO- or AO+. However, 80% occurred when the PNA was positive. All 6" or greater snowstorms during this timeframe occurred when the PNA was positive. Based on sensitivity analysis applied to the latest guidance, New York City has an implied near 100% probability of experiencing a colder than normal November. November 2019 will likely finish with a mean temperature near 44.1°. That would make this November the coldest November since 2012 when the monthly mean temperature was 43.9°.

Mann was accused of manipulating data in an attack on his professional and personal integrity.

The Supreme Court declined to block Michael Mann’s defamation case from proceeding to trial. IMO, this is good news, as the defendants made harsh allegations for which they had no evidence. Debate is undermined when parties fabricate allegations aimed at diverting discussion from the merits, especially when character is attacked to intimidate others into silence. This latest legal development is good news, both from a legal and debate perspective.

The hemispheric meteorological situation is quite dynamic as November nears a conclusion. Some of the factors that contributed to what is all but certain to be a cold November outcome in the eastern half of the CONUS along with much of eastern Canada, are now abating. The EPO was negative to strongly negative for 14 of the first 15 (93%) days of November. The Arctic Oscillation (AO) was negative to strongly negative on 13/15 (92%) days of November and has been negative every day beginning November 3. However, the EPO has now been fluctuating between weakly negative and weakly positive. The AO is forecast to rise sharply perhaps to +3.000 or above in early December. Indeed, the recent changes in the CFSv2 December forecasts provide a hint of the changing conditions. The CFSv2 is now in the skillful part of its monthly forecasting range. CFSv2 Monthly Forecasts for December: 11/19-11/27: Through December 6, no significant stratospheric warming events are likely (EPS). The recent minor warming will have little impact on the polar vortex. While rumors have been flying on Social Media about an imminent significant or major stratospheric warming event, there remains little credible evidence for such an event through 240 hours. Not suprisingly, the idea that the much hyped event would occur during the opening of December now appears unlikely to verify. As noted in past winters, Social Media is a poor place to obtain stratospheric information. With a handful of exceptions, most of those commenting on such events simply read forecast 10 mb charts. However, the atmosphere is three-dimensional. What happens at 10 mb won't necessarily occur above or below. One needs to look at all the layers of the atmosphere before reaching conclusions. Not surprisingly, there are many more calls for such warmings on Social Media than typically verify. Usually, such events occur once or sometimes twice during an entire winter. They are less frequent early in the winter. Some winters also see none. These are important reminders that readers should be wary of such calls, especially as such events are not well-forecast at long timescales. The strong model consensus for the AO to go positive and then strongly positive is consistent with the state of stratosphere. Were the AO to rise to +4.000 as shown on a few ensemble members, December would be very likely to wind up warmer than normal in the Middle Atlantic region and perhaps much of the East. Such cases are uncommon. Since 1950, there have been three such cases: 1979, 2011, and 2013. Finally, the MJO's progression through Phases 6, 7, and 8 in November at high amplitude have often preceded a mild December in the East. All said, while the first week of December could wind up cooler than normal in the East, with perhaps the first measurable snow of the season in Boston, New York City, and Newark, but not a lot of snow, the idea that warmer conditions could develop after the first week to perhaps 10 days of December seems reasonable. Overall, given the forecast teleconnections, the probability of a somewhat warmer than normal December in the East (New England might be an exception, but that is not assured) has increased.

An update concerning the issue of extreme ideas being broadcast on Social Media. https://www.americanwx.com/bb/topic/52511-autumn-2019-banter-thread/page/5/?tab=comments#comment-5338034 The cold pattern that was supposed to lock into place after mid-month: The November 16-24 anomalies: Based on the latest guidance, Chicago will likely wind up just below 0.5° above normal for the second half of November and New York City will wind up perhaps a little below 2.0° below normal. In short, the extreme scenario does not appear likely to verify. The conclusion at that time (October 30): In sum, the coldest weather of the season so far is likely to develop beginning in early November with perhaps the strongest shot of cold reaching the East during the second week of the month. However, even allowing for uncertainty, there is little support for the idea that the notable cold shown at the end of the GEFS will lock in. For forecasting purposes, one should be wary of extreme calls without really strong supporting evidence. The teleconnection forecast at the time argued against such an outcome. The final conclusion will be posted following November (probably in early December as it takes a few days for the anomalies maps to be updated).