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donsutherland1

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  1. 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.
  2. 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.
  3. The PNA is forecast to be highly stable at slightly positive levels. No spike is forecast over the next two weeks.
  4. Since 1950, 28/39 (72%) of 6" or greater snowstorms that commenced during the January 1-February 15 period had a PNA+. That figure falls afterward as wave lengths begin to shorten.
  5. For those who are interested, these were the 500 mb height anomalies for the January 31-February 1, 1878 snowstorm, which brought 7.0" snow to New York City:
  6. 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°.
  7. 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.
  8. FYI, that's a single Ensemble member. It isn't the EPS ensemble mean.
  9. 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.
  10. 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°.
  11. Although some guidance appears to be showing the PNA's reaching +1.000 to +2.000 in the near-term, one likely needs to be cautious. That guidance appears to have initialized an incorrect PNA value for today (above +1.000). The preliminary figure today was +0.315 (down ever so slightly from yesterday's +0.417). Below is the GEFS forecast from the CPC site:
  12. I suspect that implementation of the FV3 (which had been delayed due to biases but then was operationalized even before the winter to see if the biases had been addressed effectively) contributed to the change in skill rankings. If I recall correctly, all of the major global models (ECMWF, UKMET, and GGEM) saw improved skill scores during 2019. The GFS experienced a slight drop in skill. In the past, critics had argued that failure to adopt the 4d-VAR initialization scheme had put the GFS at a disadvantage. After all, the ECMWF had adopted the 4d-VAR initialization scheme with good results: https://www.ecmwf.int/en/about/media-centre/news/2017/20-years-4d-var-better-forecasts-through-better-use-observations. The ECMWF, UKMET, and GGEM all use the 4d-VAR initialization scheme. At the time, in the U.S., the argument was essentially that technical challenges made the shift in initialization approaches difficult. Looking back at those debates during the mid-2010s, it is possible that the critics were right all along. Of course, "difficult" is not a valid rationale for avoiding the efforts needed to get better. My worry is that past decisions may have locked U.S. modeling into a long-term situation where a number of international peers will continue to offer better performance for the foreseeable future. The notions that the FV3, which have now evolved into the argument of building on the FV3 core, along with increases in computing power, will rapidly reduce the competitiveness gap may be flawed. Such assumptions may not fully reflect the reality that the ECMWF, UKMET, and GGEM will continue to improve. That means that closing the modeling competitiveness gap will likely require the U.S. to improve faster than its international peers. Certainly, if the last decade is representative, that idea is questionable.
  13. Interesting article. It should be noted that if one took PHL and the surrounding stations (clockwise: Wilmington, Wayne, Lower Makefield, Ewing, Burlington Twp., Mount Laurel, and Pitman), Wayne was statistically a much greater outlier than PHL. In fact, Wayne was nearly 2 sigma above the average for the surrounding region, which included PHL. Its altitude likely played a role in that outcome.
  14. Kruunuppy , Finland and Jyvaskyla, Finland have both set January record high temperatures at 48° and 46° respectively.
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