donsutherland1

The AO is particularly important for the Middle Atlantic region and the NAO also carries weight. New England does much better thanks to its higher latitude and has had significant snowstorms even when the AO was in excess of +2.000 in January. The following from my nearly daily discussion in the NYC forum holds true for the MD-DCA-VA areas: Based on the forecast strongly positive AO to start January, the probability of a significant (6" or greater snowstorm) for the major cities of the Middle Atlantic region during the first week of January is low. Since 1950, the biggest snowfall for that region when the AO was +2.000 or above during the January 1-15 period occurred during January 14-15, 1954 when Philadelphia received 3.0" snow and New York City picked up 2.0". Boston has had numerous 6" or greater snowstorms during such cases, including one 10" or greater snowstorm. Therefore, the risk of significant snow would likely be greatest over New England assuming this relationship holds (no significant offsetting variables). Some of the newer AO forecasts keep the AO at +2.000 or above through January 10. If so, that development could adversely impact Mid-Atlantic significant snowfall prospects beyond the first week of January.

That was merely an observation. The main point is that one should not use 1978 as an analogy for the forecast Phases 4-5 MJO in the extended range.

Two photos along the Long Island Sound from early this afternoon. The temperature was 41° with drizzle. The wind was gusting around 40 mph by the water.

During theJanuary storm, the MJO was moving from Phase 3 into Phase 4 at a super high amplitude. During the February blizzard, it was in Phase 7 and headed for Phase 8 with an exceptional AO block.

MJO forecast update: The GEFS now shows the MJO moving into the Maritime Continent phases at high amplitude. It was the last hold-out. The main caveat is that such MJO forecasts at the timescale involved are still low-skill forecasts. It remains to be seen whether the EPS weeklies will deliver a fresh dose of misery later in the day.

South and west of Manhattan picked up quite a bit more precipitation this year.

As of 8:30 pm, Allentown had picked up 0.10" rain for the day. That brought total precipitation for 2019 to 60.00". As a result, 2019 became the second consecutive year during which Allentown had picked up 60.00" or more annual precipitation. Last year's figure was 66.96". This is the first time on record that Allentown has had two consecutive years with 60.00" or more precipitation. Records go back to 1901.

As of 7:25 pm, New York City had picked up 0.12" rain. That brought the precipitation total for 2019 to 52.14". As a result, 2019 has moved ahead of 1979 when 52.13" precipitation was recorded to become New York City's 31st wettest year on record. Records go back to 1869.

The long-modeled sharp increase in the Arctic Oscillation (AO) is now underway. Over the past 2 days, the AO has risen 2.5 sigma. Over the past 3 days, it has risen more than 2.8 sigma. Since 1950, there were seven prior years when the AO rose 2.5 sigma or more over a two-day period during December 20-31. During the 2010s, there has been a cluster of such events: 2014, 2015, 2016, and now 2019. Four of the prior cases saw monthly snowfall in excess of 10" in New York City during the following January: 1963-64, 1977-78, 2014-15, and 2015-16. Two had less than 4" snowfall in January: 1967-68 and 1972-73. Widespread 0.50"-1.50" precipitation is likely in the region tonight into tomorrow. As a result, Allentown will very likely reach 60" precipitation for a record second consecutive year and Scranton could reach 50" for a record second consecutive year. 2019 will also rank among the 30 wettest years on record for New York City. Through December 28, monthly anomalies for select cities were: Baltimore: +2.0°, Boston: +1.6°, Islip: +0.6°, New York City: +0.2°, Newark: +0.3°, Philadelphia: +0.5°, and Washington, DC: +1.2°. A week ago, those anomalies were: Baltimore: +0.3°, Boston: -0.8°, Islip: -1.4°, New York City: -2.7°, Newark: -2.1°, Philadelphia: -1.3°, and Washington, DC: -0.4°. A short-duration cold shot is possible late in the first week of January into the second week of January. Nevertheless, there is a growing risk that New York City and Newark could have an average temperature near or even above 40° for the first week of January. A tendency for ridging could develop during the latter part of the second week of the month. The predominant state of the EPO will likely be crucial to the persistence of any colder patterns. Based on the forecast strongly positive AO to start January, the probability of a significant (6" or greater snowstorm) for the major cities of the Middle Atlantic region during the first week of January is low. Since 1950, the biggest snowfall for that region when the AO was +2.000 or above during the January 1-15 period occurred during January 14-15, 1954 when Philadelphia received 3.0" snow and New York City picked up 2.0". Boston has had numerous 6" or greater snowstorms during such cases, including one 10" or greater snowstorm. Therefore, the risk of significant snow would likely be greatest over New England assuming this relationship holds (no significant offsetting variables). Some of the newer AO forecasts keep the AO at +2.000 or above through January 10. If so, that development could adversely impact Mid-Atlantic significant snowfall prospects beyond the first week of January. Despite the development of a sustained colder than normal temperature regime, Utqiagvik (formerly Barrow) is nearing the end of its warmest year on record. 2019 will likely conclude with a mean temperature of 20.9°. The existing record is 18.9°, which was set in 2016. Currently, 2017 ranks as the second warmest year and 2018 ranks as the fourth warmest year. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.6°C for the week centered around December 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.12°C and the ENSO Region 3.4 anomaly has averaged +0.56°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. The SOI was -0.94 today. Today, the preliminary Arctic Oscillation (AO) figure was +0.120. No significant stratospheric warming event appears likely through January 7, but warming will likely develop in the upper stratosphere and approach or reach 5 mb toward the end of the first week of January. Wave 2 activity will remain relatively muted at 30 mb through most of the first week of January, but a moderate Wave 2 hit could occur at or above 10 mb leading to the upper stratospheric warming. Overall, most of the stratosphere is forecast to remain cold through the first week of January on the EPS. However, the upper stratospheric warming will need to be watched for downward propagation. On December 28, the MJO was in Phase 7 at an amplitude of 1.233 (RMM). The December 27-adjusted amplitude was 1.511. Since 1974, there were five cases when the MJO was in Phase 6 at an amplitude of 1.500 or above during the December 20-31 period, as has been the case this year. The temperature anomalies were closely tied to how much time the MJO spent in Phase 8 during that timeframe. The mean temperature for cases with more than 5 such days was 29.0° in New York City. The mean temperature for those with 5 or fewer such days was 36.1°. The overall 1981-2019 mean temperature for January 1-15 is 33.8°. Based on sensitivity analysis applied to the latest guidance, there is an implied >99% probability that December will wind up warmer than normal in New York City with a monthly mean temperature near 38.5°. At present, a warmer than normal January appears likely in the region.

Light rain was affecting parts of the Metro NYC region near 4 pm. Overall, things remain on track for a soaking precipitation event. Much of the northern Middle Atlantic and southern New England regions will likely pick up 0.50"-1.50" precipitation with some locally higher amounts from the upcoming system. Central New York State and upstate New York into central New England, especially higher elevations, could be in line for a significant freezing rain event. Some portions of the affected area could see 0.50" or more freezing rain. Small amounts of freezing rain could extent across extreme northeastern Pennsylvania and northwestern New Jersey. Following the storm, December 2019 should end on a mild note.

A report by Goldman Sachs on climate change: https://www.goldmansachs.com/insights/pages/gs-research/taking-the-heat/report.pdf

The tropical forcing from the MJO can impact the EPO. For example, during the January 1-31, 1981-2019 period, the following relationships existed: MJO in Maritime Continent Phases (4-5) at amplitude of 1.000 or above: EPO+ 61% dates (EPO of +1.000 or above: 28% dates); EPO- 39% dates (EPO of -1.000 or below: 17% dates) MJO in Phase 8 at an amplitude of 1.000 or above: EPO+ 28% dates (EPO of +1.000 or above: 11% dates); EPO- 72% dates (EPO of -1.000 or below: 35% dates) Put another way, when the MJO was in the Maritime Continent Phases, the likelihood of a strongly positive EPO (+1.000 or above) was essentially the same as that for a positive EPO when the MJO was in Phase 8. At the same time, when the MJO was in Phase 8, the likelihood of a strongly negative EPO (-1.000 or below) was similar to the likelihood of a negative EPO during times when the MJO was in the Maritime Continent Phases.

Yes. On the GEFS it does. Still, the one-day change is disconcerting. GEFS 12/28 forecast: GEFS 12/29 forecast:

The 12/29 MJO guidance has moved closer to the Euro. The Canadian and bias-corrected GEFS now takes the MJO into the Maritime Continent phases. The GEFS made a sizable move in that direction from yesterday. The ECMWF has held steady.

January Precipitation for JFK 2020: TBD 2015: 5.31" 2019: 4.01" 1987: 5.62" 2010: 1.67" 1970: 0.56" 1984: 1.60" 1975: 5.05" 1949: 5.77" 1997: 2.37"

Another wet year in much of the region is concluding. At 8 am, rain was falling in Detroit and Indianapolis. Rain was also pushing into western Pennsylvania and western Maryland. Following the rain, Chicago and Indianapolis could approach or exceed their daily record high temperatures. Those records are: Chicago: 63°, 1984 and Indianapolis: 66°, 1889. Chicago also has a high probability of surpassing its daily record high minimum temperature of 42°, which was set in 1884. In fitting fashion for what has been a wet year, much of the northern Middle Atlantic and southern New England regions will likely pick up 0.50"-1.50" precipitation with some locally higher amounts from the upcoming system. Central New York State into central New England, especially higher elevations, could be in line for a significant freezing rain event. Year-to-Date Precipitation Figures and Rankings Scenarios are posted below:

One final thought on the potentially major implications of the recent EPS MJO forecast... The forecast shows the MJO emerging into Phases 4 and then moving into Phase 5 at a high and increasing amplitude during the extended range: The composite temperature anomalies for December-February MJO phases are below: For New York City, the below table shows data for the January 10-20, 1981-2019 period for all dates and for dates when the MJO was in Phases 4 or 5 at an amplitude ranging from 1.000 to 2.000: One important caveat: At the current timescale, MJO forecasts have relatively low verification. Therefore, such a scenario is not cast in stone. Greater clarity should develop over the coming week.

Temperatures again rose into the 50s in the Middle Atlantic region. Parts of the region saw temperatures top out in the 60s. Baltimore had a high temperature of 65° and Washington, DC had a high temperature of 67°. December will close on a generally mild note. It will also see one last storm bring a widespread 0.50"-1.50" precipitation to the region. As a result, Allentown will very likely reach 60" precipitation for a record second consecutive year and Scranton could reach 50" for a record second consecutive year. 2019 will also rank among the 30 wettest years on record for New York City. Through December 27, monthly anomalies for select cities were: Baltimore: +1.5°, Boston: +1.4°, Islip: +0.3°, New York City: -0.3°, Newark: -0.1°, Philadelphia: +0.1°, and Washington, DC: +0.7°. A short-duration cold shot is possible late in the first week of January into the second week of January. Nevertheless, there is a growing risk that New York City and Newark could have an average temperature near or even above 40° for the first week of January. Afterward, the predominant state of the EPO will likely be crucial to the persistence of any colder patterns. The 18z GFS forecast the EPO to fall to an all-time record below -5.000 in the extended range. Neither the GEFS nor EPS show anything like that. Hence, the 18z GFS solution beyond 300 hours could be suspect. Based on the forecast strongly positive AO to start January, the probability of a significant (6" or greater snowstorm) for the major cities of the Middle Atlantic region during the first week of January is low. Since 1950, the biggest snowfall for that region when the AO was +2.000 or above during the January 1-15 period occurred during January 14-15, 1954 when Philadelphia received 3.0" snow and New York City picked up 2.0". Boston has had numerous 6" or greater snowstorms during such cases, including one 10" or greater snowstorm. Therefore, the risk of significant snow would likely be greatest over New England assuming this relationship holds (no significant offsetting variables). Despite the development of a sustained colder than normal temperature regime, Utqiagvik (formerly Barrow) is nearing the end of its warmest year on record. 2019 will likely conclude with a mean temperature of 20.9°. The existing record is 18.9°, which was set in 2016. Currently, 2017 ranks as the second warmest year and 2018 ranks as the fourth warmest year. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.6°C for the week centered around December 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.12°C and the ENSO Region 3.4 anomaly has averaged +0.56°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. The SOI was -12.04 today. Today, the preliminary Arctic Oscillation (AO) figure was -1.339. No significant stratospheric warming event appears likely through January 6, but warming will likely develop in the upper stratosphere and approach or reach 5 mb toward the end of the first week of January. Wave 2 activity will remain relatively muted at 30 mb through most of the first week of January, but a moderate Wave 2 hit could occur at or above 10 mb leading to the upper stratospheric warming. Overall, most of the stratosphere is forecast to remain cold through most of the first week of January on the EPS. On December 27, the MJO was in Phase 7 at an amplitude of 1.510 (RMM). The December 26-adjusted amplitude was 1.581. Since 1974, there were five cases when the MJO was in Phase 6 at an amplitude of 1.500 or above during the December 20-31 period, as has been the case this year. The temperature anomalies were closely tied to how much time the MJO spent in Phase 8 during that timeframe. The mean temperature for cases with more than 5 such days was 29.0° in New York City. The mean temperature for those with 5 or fewer such days was 36.1°. The overall 1981-2019 mean temperature for January 1-15 is 33.8°. Based on sensitivity analysis applied to the latest guidance, there is an implied 96% probability that December will wind up warmer than normal in New York City with a monthly mean temperature near 38.5°. At present, a warmer than normal January appears likely in the region. 　

A quick note on the 18z GFS: The model showed the EPO diving to historic levels toward or below -5.000 in the extended range. That was radically different from the 12z run and the 18z GEFS. It is an outlier with that teleconnection. Hence, its extended range depiction might be a low probability outcome.

Quick follow up on the discussion concerning possible East Coast ridging for the January 10-17 period: 1. The 12z EPS builds the ridging, especially from 300 hours to 360 hours 2. The 12z GEFS shows some ridging now, but it could be transient there. Still that's a pretty big change from 24-48 hours ago. 3. The ECMWF still shows the MJO briefing passing through Phases 7-8 and then entering the dreaded Maritime Continent at high and increasing amplitude in the extended range. So, at least for now, my concerns about the specified period above persist, namely that transient cold could give way to a period of milder conditions. Afterward, much will depend on the MJO's progression and the evolution of the teleconnections.

Noting that there will be a mild start should not be seen as giving up. Big flips have occurred in the past i.e., 2005 and 2007. Hopefully, we will see something similar this time around.

Bluewave has no "narrative" or "agenda." He posts a wide range of content about the weather--cold and warm, precipitation, etc.

Thanks Ottawa Blizzard. I hope all is well with you. I'm not sure what The Weather Network and Weatherbell saw or on which they based their forecasts. The composite temperature anomalies for neutral-warm/borderline weak El Nino cases didn't favor widespread cold in Canada (northern Canada was favored), especially in Ontario. The C3S multi-system guidance also favored warmth across a large part of Canada. Toronto will likely wind up having a warmer than normal winter. Unfortunately, snowfall appears to be in line for a below normal season.

An important paper concerning the impact of the stratospheric polar vortex... Abstract: The impact of the Arctic stratospheric polar vortex on persistent weather regimes over North America is so far underexplored. Here we show the relationship between four wintertime North American weather regimes and the stratospheric vortex strength using reanalysis data. We find that the strength of the vortex significantly affects the behavior of the regimes. While a regime associated with Greenland blocking is strongly favored following weak vortex events, it is not the primary regime associated with a widespread, elevated risk of extreme cold in North America. Instead, we find that the regime most strongly associated with widespread extremely cold weather does not show a strong dependency on the strength of the lower stratospheric zonal mean zonal winds. We also suggest that stratospheric vortex morphology may be particularly important for cold air outbreaks during this regime. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL085592

Despite mainly cloudy skies, unseasonably mild conditions continued to erase the cold anomalies that had built up through December 21 in the Middle Atlantic region. The closing days of December will generally be warmer to occasionally much warmer than normal. Based on the latest guidance, the warmth will likely be sufficient to ensure that most of the Middle Atlantic region will wind up somewhat warmer to warmer than normal for December. Through December 26, monthly anomalies for select cities were: Baltimore: +1.0°, Boston: +0.7°, Islip: -0.3°, New York City: -0.9°, Newark: -0.8°, Philadelphia: -0.4°, and Washington, DC: +0.3°. A short-duration cold shot is possible late in the first week of January into the second week of January. Nevertheless, there is a growing risk that New York City and Newark could have an average temperature near or even above 40° for the first week of January. Afterward, the predominant state of the EPO will likely be crucial to the persistence of any colder patterns. Based on the forecast strongly positive AO to start January, the probability of a significant (6" or greater snowstorm) for the major cities of the Middle Atlantic region during the first week of January is low. Since 1950, the biggest snowfall for that region when the AO was +2.000 or above during the January 1-15 period occurred during January 14-15, 1954 when Philadelphia received 3.0" snow and New York City picked up 2.0". Boston has had numerous 6" or greater snowstorms during such cases, including one 10" or greater snowstorm. Therefore, the risk of significant snow would likely be greatest over New England assuming this relationship holds (no significant offsetting variables). Despite the development of a sustained colder than normal temperature regime, Utqiagvik (formerly Barrow) is nearing the end of its warmest year on record. 2019 will likely conclude with a mean temperature of 20.8°. The existing record is 18.9°, which was set in 2016. Currently, 2017 ranks as the second warmest year and 2018 ranks as the fourth warmest year. The ENSO Region 1+2 anomaly was +0.4°C and the Region 3.4 anomaly was +0.6°C for the week centered around December 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.12°C and the ENSO Region 3.4 anomaly has averaged +0.56°C. The remainder of winter 2019-2020 will likely feature neutral-warm to weak El Niño conditions. The SOI was -17.49 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.389. No significant stratospheric warming event appears likely through January 5, but warming above 3 mb will likely commence in coming days. Wave 2 activity will remain relatively muted into the first week of January. Overall, most of the stratosphere is forecast to remain cold well into the first week of January on the EPS. On December 26, the MJO was in Phase 6 at an amplitude of 1.577 (RMM). The December 25-adjusted amplitude was 1.524. Since 1974, there were five cases when the MJO was in Phase 6 at an amplitude of 1.500 or above during the December 20-31 period, as has been the case this year. The temperature anomalies were closely tied to how much time the MJO spent in Phase 8 during that timeframe. The mean temperature for cases with more than 5 such days was 29.0° in New York City. The mean temperature for those with 5 or fewer such days was 36.1°. The overall 1981-2019 mean temperature for January 1-15 is 33.8°. Based on sensitivity analysis applied to the latest guidance, there is an implied 94% probability that December will wind up warmer than normal in New York City with a monthly mean temperature near 38.7°. At present, a warmer than normal January appears likely in the region.