donsutherland1

Morning thoughts... Today will be partly cloudy and a bit milder than yesterday. Temperatures will likely reach the lower and middle 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 41° Newark: 43° Philadelphia: 44° The dry weather will continue through much of the week.

https://public.tableau.com/profile/don.sutherland#!/vizhome/NYCArea6Snowstorms/Dashboard1

A relatively quiet weather pattern remains in place. The dry weather could last through much of this week. A strong flow of Pacific Air will push much milder air eastward. On Wednesday, high temperatures could approach or break records in the Northern Plains. The temperature could make a run at 50° on either Thursday or Friday in New York City before somewhat cooler air returns. The first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada overall. After January 10, the EPS continues to shows a transition during which a trough will move into the East. During the second half of January, there will be some potential for snow events in the Middle Atlantic and southern New England regions. Afterward, the evolution of the AO will determine whether such potential continues into February. Uncertainty about the long-range has increased. There is emerging ensemble guidance showing that the AO could go positive in the closing week of January. That outcome would likely lead to a warmup near the beginning of February. The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.1°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.77°C and the ENSO Region 3.4 anomaly has averaged -1.07°C. La Niña conditions will likely prevail at least through the winter. The SOI was +15.17 today. Today, the preliminary Arctic Oscillation (AO) figure was -1.056. On January 10 the MJO was in Phase 3 at an amplitude of 1.343 (RMM). The January 9-adjusted amplitude was 1.444. Following a significant stratospheric warming event, the stratosphere is now cooling. The mean zonal winds have reversed at 1 mb and 10 mb. They could still reverse at 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Blocking appears likely to continue through at least the first half of January. There is emerging ensemble guidance suggesting that blocking could fade during the last week of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.7°.

Morning thoughts... Today will be partly to mostly sunny and cool. Temperatures will likely reach the upper 30s and lower 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 39° Newark: 40° Philadelphia: 42° The dry weather will continue through mid-week.

A relatively quiet weather pattern remains in place. A seasonably cold but dry weekend lies ahead. The dry weather could last through at least the middle of week. The first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada overall. After January 10, the EPS continues to shows a transition during which a trough will move into the East. During the second half of January, there will be some potential for snow events in the Middle Atlantic and southern New England regions. Afterward, the evolution of the AO will determine whether such potential continues into February. However, uncertainty about the long-range has increased. There is emerging ensemble guidance showing that the AO could go positive in the closing week of January. The ENSO Region 1+2 anomaly was -1.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.80°C and the ENSO Region 3.4 anomaly has averaged -1.10°C. La Niña conditions will likely prevail at least through the winter. The SOI was +8.20 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.086. On January 9 the MJO was in Phase 3 at an amplitude of 1.443 (RMM). The January 8-adjusted amplitude was 1.618. Following a significant stratospheric warming event, the stratosphere is now cooling. The mean zonal winds have reversed at 1 mb and 10 mb. They could still reverse at 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. Blocking appears likely to continue through at least the first half of January. There is emerging ensemble guidance suggesting that blocking could fade during the last week of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.6°.

Morning thoughts... Today will be partly to mostly sunny and cool. Temperatures will likely reach the lower 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 42° Newark: 43° Philadelphia: 44° The dry weather will continue through mid-week.

A relatively quiet weather pattern remains in place. A seasonably cold but dry weekend lies ahead. The dry weather could last through at least the middle of week. The first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada overall. After January 10, the EPS continues to shows a transition during which a trough will move into the East. During the second half of January, there will be some potential for snow events in the Middle Atlantic and southern New England regions. Afterward, the evolution of the AO will determine whether such potential continues into February. The ENSO Region 1+2 anomaly was -1.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.80°C and the ENSO Region 3.4 anomaly has averaged -1.10°C. La Niña conditions will likely prevail at least through the winter. The SOI was +4.25 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.867. On January 8 the MJO was in Phase 3 at an amplitude of 1.617 (RMM). The January 7-adjusted amplitude was 1.595. Following a significant stratospheric warming event, the stratosphere is now cooling. The mean zonal winds have reversed at 1 mb and 10 mb. They could reverse at 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 80% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.3°.

A complex pattern evolution is underway. The SSW coupled with a reinvigorated moderate La Niña is a challenging environment where model skill scores are likely to be lower than typical. The weeklies beyond two weeks have little or no skill relative to climatology.

Gradient patterns can produce. But I don’t like this pattern currently shown at the end of the EPS for a number of reasons: 1. Gradient patterns that produce a lot of snow typically have a trough all across Canada 2. There is a lot of cold not marginal air available to be tapped in eastern Canada The February 1994 500 mb pattern provides a classic example of the kind of gradient patterns that work. The forecast one does not resemble that pattern.The North American trough is north-south oriented, not east-west oriented across Canada. The ridge in the southeast is more expansive and stronger. If the pattern does, in fact, evolve toward that, I don’t believe we’ll see much snow until it changes again. Earlier runs of the EPS were better. Let’s see what the 12z cycle shows.

That’s an important point about the sudden stratospheric warming event (SSW). With the polar vortex splitting, Eurasia was favored for the severe cold. That’s, by far, the most common case, as displacement events favor North America. The Twitter accounts reflexively proclaiming that the stratospheric warming meant that severe cold would pour into the region have little understanding of such events and their implications. That’s the fact. One sees their track record with stratospheric warmings over and over again, including forecasts for such events that never develop, because they focus solely on one specific layer of the stratosphere (either 30 mb or 10 mb) not all layers. There was potential for a snowy but not overly cold pattern here, but favorable 500 mb patterns don’t amount to much without surface features. That’s why potential isn’t always realized. We’ll have to see if this is the case again during the second half of January where there will be potential (somewhat favorable to favorable upper air pattern). I’m not ready to write things off for the second half of January just yet. But when the AO goes positive and/or the PNA goes negative, then the window of opportunity will close. For January, the AO-/PNA+ pattern is the most favorable for significant (6” or above) snowstorms for the Philadelphia and New York City areas.

Morning thoughts... Today will be partly to mostly sunny and cool. Temperatures will likely reach the middle and upper 30s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 36° Newark: 38° Philadelphia: 38° The dry weather will continue through the weekend.

A relatively quiet weather pattern remains in place. A seasonably cold but dry weekend lies ahead. The dry weather could last into early next week. The first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada overall. After January 10, the EPS continues to shows a transition during which a trough will move into the East. During the second half of January, there will be some potential for snow events in the Middle Atlantic and southern New England regions. Afterward, the evolution of the AO will determine whether such potential continues into February. The ENSO Region 1+2 anomaly was -1.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.80°C and the ENSO Region 3.4 anomaly has averaged -1.10°C. La Niña conditions will likely prevail at least through the winter. The SOI was +16.77 today. Today, the preliminary Arctic Oscillation (AO) figure was -2.893. On January 7 the MJO was in Phase 3 at an amplitude of 1.595 (RMM). The January 6-adjusted amplitude was 1.289. Following a significant stratospheric warming event, the stratosphere is now cooling. The mean zonal winds have reversed at 1 mb and 10 mb. They could reverse at 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 78% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.0°.

This is correct. The idea that the La Niña would collapse was incorrect. It should persist through the winter and that base case has not changed. There can be fluctuations in the anomalies and a temporary warming may have driven speculation that it was rapidly dissipating. Over the past two weeks, the temporary warming reversed (something the CFSv2 showed).

At some point, I may create one for ABE. That will require some research. However, the chart is as wide as Tableau Public permits. When I added ISP, the chart reached the edge of the permissible boundaries of the software.

Morning thoughts... Today will be partly to mostly sunny. Temperatures will likely reach the upper 30s and lower 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 40° Newark: 41° Philadelphia: 41° A dry and seasonably cold weekend lies ahead.

A relatively quiet weather pattern remains in place. Through Friday, partly sunny and somewhat milder than normal conditions will likely prevail. The likely continuation of Arctic blocking through at least January 15 would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPS continues to shows a transition during which a trough will move into the East. The operational ECMWF has persistently shown an opportunity for snowfall during or near the end of the transitional period. Arctic air will likely shift mainly to Eurasia. However, the evolving pattern could be sufficiently cold to afford opportunities for snowfall if the pattern evolves as currently shown on the EPS. It remains possible that the pattern evolution could lead to a multiweek period with higher than climatological potential for snowfall. The ENSO Region 1+2 anomaly was -1.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.80°C and the ENSO Region 3.4 anomaly has averaged -1.10°C. La Niña conditions will likely prevail at least through the winter. The SOI was +25.58 today. Today, the preliminary Arctic Oscillation (AO) figure was -3.245. On January 6 the MJO was in Phase 3 at an amplitude of 1.288 (RMM). The January 5-adjusted amplitude was 1.048. A significant stratospheric warming event is continuing to evolve. The temperature has now peaked at 1 mb, but was still rising at 10 mb and 30 mb. Temperatures at those levels of the stratosphere should peak and begin falling in coming days. The mean zonal winds have reversed at 1 mb and 10 mb. They could reverse 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January. Based on sensitivity analysis applied to the latest guidance, there is an implied 75% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.0°.

Morning thoughts... Today will be partly to mostly sunny. Temperatures will likely reach the lower and perhaps middle 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 44° Newark: 45° Philadelphia: 45° Mainly fair and somewhat milder than normal temperatures will prevail through much of the week.

A relatively quiet weather pattern remains in place. Through Friday, partly sunny and somewhat milder than normal conditions will likely prevail. The likely continuation of Arctic blocking through at least January 15 would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPS continues to shows a transition during which a trough will move into the East. The operational ECMWF has persistently shown an opportunity for snowfall during or near the end of the transitional period. Arctic air will likely shift mainly to Eurasia. However, the evolving pattern could be sufficiently cold to afford opportunities for snowfall if the pattern evolves as currently shown on the EPS. It remains possible that the pattern evolution could lead to a multiweek period with higher than climatological potential for snowfall. The ENSO Region 1+2 anomaly was -1.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.80°C and the ENSO Region 3.4 anomaly has averaged -1.10°C. La Niña conditions will likely prevail at least through the winter. The SOI was +26.62 today. Today, the preliminary Arctic Oscillation (AO) figure was -3.510. That is the lowest AO figure since November 26, 2018 when the AO was -3.629. On January 5 the MJO was in Phase 3 at an amplitude of 1.048 (RMM). The January 4-adjusted amplitude was 0.908. A significant stratospheric warming event is continuing to evolve. The temperature has now peaked at 1 mb, but was still rising at 10 mb and 30 mb. Temperatures at those levels of the stratosphere should peak and begin falling in coming days. The mean zonal winds have reversed at 1 mb and 10 mb. They could reverse 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January.

Perhaps the recent short-term strengthening of the La Nina has contributed to this modeled outcome this time around. A gradual weakening remains far more likely than a collapse. The canonical La Nina evolution has a lot to do with the tropical forcing. But there are numerous pieces that could impact the outcome this time around, including but not limited to the evolving stratospheric warming event.

That’s far enough away that there remain alternative scenarios. The ongoing stratospheric warming event provides additional long-range uncertainty.

It’s too soon to tell. The polar vortex should remain weak through much of the month. Nevertheless, the EPS weeklies are forecasting the development of an EPO+/AO+/PNA- pattern for late January. At this point, that’s beyond their skillful range.

Morning thoughts... Today will become partly to mostly sunny. Temperatures will likely reach the lower 40s in much of the region. Likely high temperatures around the region include: New York City (Central Park): 42° Newark: 43° Philadelphia: 43° Mainly fair and somewhat milder than normal temperatures will prevail through much of the week.

A relatively quiet weather pattern is in place. Through Friday, partly to mostly sunny and milder than normal conditions will likely prevail. The likely continuation of Arctic blocking through at least January 15 would typically provide a higher than climatological probability for above normal snowfall. Ideally, an expansive block would be anchored across the Baffin Bay or Greenland, not south of the Davis Strait. Blocks that are anchored near Newfoundland and Labrador can inhibit opportunities for snowfall and result in warmer to much warmer than normal conditions in the Middle Atlantic and southern New England regions. This is now the most likely scenario for much of the first half of January. Under this scenario, the first 10-15 days of January will likely be generally warmer to perhaps much warmer than normal across the northeastern United States, Quebec, and much of eastern Canada. After January 10, the EPS continues to shows a transition during which a trough will move into the East. Arctic air will likely shift mainly to Eurasia. However, the evolving pattern could be sufficiently cold to afford opportunities for snowfall if the pattern evolves as currently shown on the EPS. It remains possible that the pattern evolution could lead to a multiweek period with higher than climatological potential for snowfall. The ENSO Region 1+2 anomaly was -1.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.80°C and the ENSO Region 3.4 anomaly has averaged -1.10°C. La Niña conditions will likely prevail at least through the winter. The SOI was +20.07 today. Today, the preliminary Arctic Oscillation (AO) figure was -3.430. On January 4 the MJO was in Phase 3 at an amplitude of 0.910 (RMM). The January 3-adjusted amplitude was 0.762. A significant stratospheric warming event is underway. The mean zonal winds has reversed at 1 mb and will likely reverse at 10 mb and possibly 30 mb. In the wake of this warming event, the polar vortex will likely split. The dominant piece will, as is typical with such events, migrate to Eurasia. The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish. For now, blocking appears likely to continue through at least the first half of January.

That system has been in the ECMWF for 3 if the last 5 0z/12z runs. Details have differed, but there’s some potential.

The pattern transition should occur during January 10-15. It would be nice to get something during that timeframe, but it isn't assured. Then, there could be 2 to maybe 4 weeks where there is potential. Patterns with potential don't always produce, though, but we'll see how things unfold.