donsutherland1

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.

The first half of January =/= the remainder of winter. As noted in the past, one has to be wary of Social Media. Exaggeration is commonplace (big snowstorms, extreme cold, stratospheric warming events, and now claims about an impending demise of winter) on Social Media. Even as January appears likely to be warmer than normal on average, that does not mean that sustained cold with opportunities for snowfall can't develop later in the month or that February could not feature above normal snowfall.

With regard to the Week 3 (January 10-17) Ridging in the East: There is a wide range of thought concerning this potential ridging (the "missing piece" I alluded to yesterday on a GEFS map). Unfortunately, a day later, the EPS, GEFS, and Canadian ensembles have all "found" this piece. That raises the question as to whether it is a realistic model depiction in a timeframe where skill scores are low. I believe it is. This does not, of course, mean that I expect it to persist through much or all of the remainder of January. It's far too soon to make such a call. I do believe it is a crucial development that will likely lead to a warmer than normal month as a whole in much or all of the East (I'm currently thinking somewhere in the vicinity of 1.5° above normal but haven't finalized the number). My reasoning concerning the development of the ridging is as follows: 1. The latest EPS (and GEFS) forecasts the MJO to move into Phase 5 toward January 10 (the start of the period in question). Model guidance has grown firmer on this idea in recent days, though such forecasts are still in a time range with low skill (and a wider turn that takes it through an alternative path that includes Phases 7-8-1 rather than 4-5 can't be ruled out). The fading IOD+ may also still be constructively interfering with the MJO. Rossby wave activity may also have an impact. The 200 mb height anomaly (DJF with no lag) for Phase 5 produces a map that is quite similar to the forecast 500 mb anoamlies shown on the latest ensemble guidance (including the 6z GEFS) in the extended range: Any time one of the composite maps fits modeled output suggests one should give at least some consideration to that output. 2. The 12/27 0z EPS and 12/27 6z GEFS show the development of ridging in the East in the extended range (present from hour 336 and afterward on the EPS and from hour 354 and afterward on the GEFS). The CFSv2 week 3 forecast also shows such ridging. 3. The pattern fits the January 500 mb pattern with a monthly AO of +1.000 or above and an EPO > 0 (1950-2019). 4. The ensemble forecasts call for a strong polar vortex to be present through at least January 10. 5. No significant stratospheric warming events are likely through at least the middle of the first week of January according to the EPS. Overall, there is a body of evidence that argues for ridging to develop in the East around January 10 +/- a few days. Whether such ridging persists will depend on the progression of the MJO (will it spend appreciable time in the Maritime Continent before progressing through Phases 6 and 7 and 8 should the EPS forecast verify?) and the state of the teleconnections (persistence of AO+/EPO+). Some of the new guidance shows the EPO falling to neutral late in the first week of January or just afterward, so that's a positive development that will need to be watched. At the same time, some of the recent guidance shows the development of a PNA- in the extended range, a development that would also favor ridging in the East. As always, it should be noted that such forecasts have low skill and may change considerably over a week or two. Moreover, I could be wrong. The main point was that there is a body of evidence to suggest that the forecast development of ridging is plausible. The picture should become clearer over the next week.

Record high temperatures were recorded in parts of the Great Lakes region today. Record highs included: Chicago: 61° (old record: 55°, 1971); Detroit: 58° (old record: 57°, 2016); Milwaukee: 58° (old record: 51°, 1936 and 2018); and, Toledo: 63° (old record: 62°, 1888). 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 much of the Middle Atlantic region will wind up somewhat warmer to warmer than normal for December. Through today, New York City's highest temperature this December is 58°, which occurred on December 10. The last December to have a monthly maximum temperature below 60° was December 2005 when the temperature peaked at 55° on December 24. However, the potential exists for the temperature to approach or reach 60° in New York City during the December 29-30 period. Through December 25, monthly anomalies for select cities were: Baltimore: +0.8°, Boston: +0.5°, Islip: -0.5°, New York City: -1.2°, Newark: -1.0°, Philadelphia: -0.5°, and Washington, DC: +0.1°. Colder air could return during the first week of January. The progression of the MJO in concert with the teleconnections could be crucial in determining whether most of North America's cold air stays bottled up north of the Canada-U.S. border beyond the first week of January or it comes southward into the region shortly after the start of 2020. Transient shots of cold would be possible under the former scenario, which currently appears to be somewhat more likely than not through the first week of January. Afterward, the predominant state of the EPO will likely be crucial to the persistence of the cold. 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 Philadephia 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 -28.39 today. That is the lowest SOI value since November 5 when the SOI was -34.49. Today, the preliminary Arctic Oscillation (AO) figure was -2.748. No significant stratospheric warming event appears likely through January 4, but some 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 into the start of January on the EPS. On December 25, the MJO was in Phase 6 at an amplitude of 1.528 (RMM). The December 24-adjusted amplitude was 1.121. Based on sensitivity analysis applied to the latest guidance, there is an implied 87% probability that December will wind up warmer than normal in New York City with a monthly mean temperature near 38.5°.

We agree about the possible day 9-13 cold shot. I believe the modeled idea is legitimate. I am concerned how things might evolve should Atlantic and Pacific blocking fail to develop: namely the risk of a multi-week warm regime. I think we'll get some opportunities for snowfall, but am less certain about the monthly anomaly. I'm looking at a lot of data, but the forecast teleconnections argue that a mild January is not implausible.

Just before sunrise today: