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Met Winter 20-21: Pattern Drivers & Evolution


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While there's reasonable agreement on a -AO and -NAO persisting into early January, there is some uncertainty WRT whether or not the Pacific side offers any help or not. The EPS develops a +EPO into e

I'm starting to get a little more excited for early-mid December. It looks like the Pacific jet will retract significantly, which is the real reason for the retrograding Alaskan LP. Upper level diverg

I think that we are going to see a pretty impeccable 500mb pattern after January 10th.    The -NAO originally forced by wave breaking (which is occurring in the very near future) will become

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4 minutes ago, uncle w said:

another Johnny come lately...or Joey in his case...

I don't blame him in this case.  You don't want to forecast something that anomalous in March without good evidence, especially late March.

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1 minute ago, Analog96 said:

I don't blame him in this case.  You don't want to forecast something that anomalous in March without good evidence, especially late March.

yeah I was just kidding...I liked the end of March and early April from the start...all analog driven...

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2 minutes ago, uncle w said:

late March has no major storms over 6" for NYC...some 3-5" but no higher...April had four 8" or greater storms and many more 4" plus storms...maybe this year fills the void in major snowstorms at the end of March...3-4" is a more realistic number if NYC gets a late season snowstorm...on Staten Island in April 2003 we got almost 7" during a daylight storm...2018 was another 6 incher on Staten Island...

 

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5 minutes ago, Allsnow said:

@Superstorm93 texted this to me so credit to him....

 

This was a real good winter for nyc and nnj 

2B9E5097-C1DE-4458-98ED-19842A31FD33.png

It was an incredible February.  We had a nice storm in December.  But it did not snow at all in January, save a few less than one inch events.

It was a good winter, perhaps very good.  Another significant snowstorm and I might rank it higher.

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6 minutes ago, Analog96 said:

It was an incredible February.  We had a nice storm in December.  But it did not snow at all in January, save a few less than one inch events.

It was a good winter, perhaps very good.  Another significant snowstorm and I might rank it higher.

Agree. The break in January was frustrating beyond belief 

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Tomorrow will be fair and continued cold. Sunday will be somewhat warmer and still dry.

 

Overall, the first week of March will see variable temperatures, even as the week will very likely average cooler than normal. Another short but sharp cold shot is possible Friday through the weekend. Afterward, a strong warming trend should commence. Parts of the region will likely see their warmest temperatures so far during the second week of March. The 60° DT could extend into southern and perhaps even central New England during the height of the warmth. Central Park will very likely see its first 60° reading since December 25 and perhaps its highest temperatures since late November.

 

Toward the latter part of the second week of the month or just after mid-month, temperatures could begin to cool as the AO falls sharply from its forecast peak.

 

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around February 24. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.60°C and the ENSO Region 3.4 anomaly has averaged -0.80°C. La Niña conditions will likely prevail at least through most of March.

 

The SOI was -6.94 today. The SOI has now been negative for six consecutive days. The last time that occurred was October 14-20, 2020 when the SOI was negative for seven consecutive days. This development could be an early indication that what has been a fairly stable La Niña regime throughout the winter could be moving closer to its end stages.

The preliminary Arctic Oscillation (AO) figure was -0.805 today.

 

On March 4 the MJO was in Phase 7 at an amplitude of 0.892 (RMM). The March 3-adjusted amplitude was 0.719 (RMM).

 

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. Since January 1, New York City has picked up 28.1" snow.

 

Winters that saw December receive 10" or more snow, less than 10" in January, and then 10" or more in February in New York City, saw measurable snowfall in March or April in 83% of cases. Winter 2009-2010 was the exception where only a trace of snow was recorded. This group of winters saw 6" or more snow during the March-April period in 50% of the cases. All said, it is more likely than not that there will be measurable snowfall after February.  

 

 

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12 hours ago, Allsnow said:

Agree. The break in January was frustrating beyond belief 

Not sure about up in your neck of the woods (due to Miller B's) but down in the mid-Atlantic,  January is typically an underperforming month. Which would seem to be counter intuitive considering it being statistically the coldest month of the year. But that is because that is typically when we see the NS at its strongest and the suppression that comes along with it. So many years our snow chances are limited to weak impulses in the NS (Clipper styled) and hoping to cash in a little on any Miller Bs, which rarely works out well for us.

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Tomorrow will be another cool day, capping a first week of March with temperature anomalies of 4°-6° below normal across the northern Middle Atlantic and southern New England areas.

 

Early next week, a strong warming trend should commence. Parts of the region will likely see their warmest temperatures so far this year. The 60° DT will likely extend into southern and perhaps even central New England during the height of the warmth. Central Park will very likely see its first 60° reading since December 25 and perhaps its highest temperatures since late November.

 

Toward the latter part of the week, near or just after mid-month, temperatures could begin to cool as the AO falls sharply from its forecast peak.

 

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around February 24. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.60°C and the ENSO Region 3.4 anomaly has averaged -0.80°C. La Niña conditions will likely prevail at least through most of March.

 

The SOI was -2.73 today. The SOI has now been negative for seven consecutive days. The last time that occurred was October 14-20, 2020 when the SOI was negative for seven consecutive days. This development could be an early indication that what has been a fairly stable La Niña regime throughout the winter could be moving closer to its end stages.

The preliminary Arctic Oscillation (AO) figure was +0.243 today.

 

On March 5 the MJO was in Phase 8 at an amplitude of 0.781 (RMM). The March 4-adjusted amplitude was 0.892 (RMM).

 

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. Since January 1, New York City has picked up 28.1" snow.

 

Winters that saw December receive 10" or more snow, less than 10" in January, and then 10" or more in February in New York City, saw measurable snowfall in March or April in 83% of cases. Winter 2009-2010 was the exception where only a trace of snow was recorded. This group of winters saw 6" or more snow during the March-April period in 50% of the cases. All said, it is more likely than not that there will be measurable snowfall after February.  

 

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Under bright sunshine, the temperature soared 40° or above in many parts of the region. Nevertheless, March 2021 became the 11th case since 1990 during which March 1-7 had a mean temperature below 35° in Central Park. The 10 prior cases were: 1990, 1996, 2001, 2003, 2006, 2007, 2009, 2014, 2015, and 2019. In seven (70%) of those cases, New York City saw measurable snow on or after March 15. Four of those cases saw 4" or more (1996, 2003, 2007, and 2015).

 

After a similar to perhaps somewhat milder day tomorrow, a strong warming trend will commence on Tuesday. Many parts of the region will likely see their warmest temperatures so far this year later this week. The 60° DT will likely extend into southern and perhaps even central New England during the height of the warmth. Central Park will very likely see its first 60° reading since December 25 and perhaps its highest temperatures since late November.

 

Toward the latter part of the week, near or just after mid-month, temperatures could begin to cool as the AO falls sharply from its forecast peak.  

 

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around February 24. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.60°C and the ENSO Region 3.4 anomaly has averaged -0.80°C. La Niña conditions will likely prevail at least through most of March.

 

The SOI was -3.40 today. The SOI has now been negative for eight consecutive days. The last time that occurred was June 14-21, 2020 when the SOI was negative for eight consecutive days. This development could be an early indication that what has been a fairly stable La Niña regime throughout the winter could be moving closer to its end stages.

The preliminary Arctic Oscillation (AO) figure was +1.038 today.

 

On March 6 the MJO was in Phase 8 at an amplitude of 0.715 (RMM). The March 5-adjusted amplitude was 0.784 (RMM).

 

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. Since January 1, New York City has picked up 28.1" snow.

 

Winters that saw December receive 10" or more snow, less than 10" in January, and then 10" or more in February in New York City, saw measurable snowfall in March or April in 83% of cases. Winter 2009-2010 was the exception where only a trace of snow was recorded. This group of winters saw 6" or more snow during the March-April period in 50% of the cases. All said, it is more likely than not that there will be measurable snowfall after February.  

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 52% probability that New York City will have a warmer than normal March. March will likely finish with a mean temperature near 43.0° (0.5° above normal).

 

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The temperature rose into the 40s across much of the region today. Not too far south in Baltimore and Washington, the temperature rose into the 50s. Tomorrow, that warmth will surge northward with much of the region seeing the temperature top out in the 50s with some 60s possible.

 

Wednesday could be a few degrees cooler and then the warmest air of the season will arrive for Thursday and Friday. The 60° DT will likely extend into southern and perhaps even central New England during the height of the warmth. Central Park will very likely see its first 60° reading since December 25 and likely its highest temperatures since late November.

Toward the latter part of the week, near or just after mid-month, temperatures could begin to cool as the AO falls sharply from its forecast peak. However, just as was the case during the historic February arctic outbreak, the core of the cold will likely remain west of the region on account of a fairly expansive western Atlantic ridge.  

 

The ENSO Region 1+2 anomaly was +0.2°C and the Region 3.4 anomaly was -0.7°C for the week centered around March 3. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged -0.87°C. La Niña conditions will likely prevail at least through most of March. Afterward, neutral-cool ENSO conditions will likely develop as the spring progresses.

 

The SOI was -4.12 today. The SOI has now been negative for nine consecutive days. The last time that occurred was March 16-31, 2020 when the SOI was negative for 16 consecutive days. This development could be an early indication that what has been a fairly stable La Niña regime throughout the winter could be moving closer to its end stages.

 

The preliminary Arctic Oscillation (AO) figure was +1.206 today. Over the next few days, the AO is forecast to rise sharply. The ensembles suggest that the AO could peak at or above +5.000. This would be a rare event in March. Since 1950, only March 7-8, 2015 saw the AO at or above +5.000. The March record is +5.588, which was set on March 8, 2015.

On March 7 the MJO was in Phase 8 at an amplitude of 0.764 (RMM). The March 6-adjusted amplitude was 0.713 (RMM).

 

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. Since January 1, New York City has picked up 28.1" snow.

 

Winters that saw December receive 10" or more snow, less than 10" in January, and then 10" or more in February in New York City, saw measurable snowfall in March or April in 83% of cases. Winter 2009-2010 was the exception where only a trace of snow was recorded. This group of winters saw 6" or more snow during the March-April period in 50% of the cases. All said, it is more likely than not that there will be measurable snowfall after February.  

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 52% probability that New York City will have a warmer than normal March. March will likely finish with a mean temperature near 43.0° (0.5° above normal).

 

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Under brilliant sunshine, the temperature soared into the 60s across much of the region. High temperatures included:

 

Allentown: 61° (warmest since December 25)
Boston: 61° (warmest since December 1)
Bridgeport: 64° (old record: 63°, 2020; warmest since November 30)
Islip: 63° (warmest since December 13)
New York City: 64° (warmest since November 26)
Newark: 66° (warmest since November 26)
Philadelphia: 69° (warmest since November 11)
Poughkeepsie: 61° (warmest since December 25)

 

Tomorrow will likely be a few degrees cooler and then the warmest air of the season will arrive for Thursday and Friday.

 

Afterward, temperatures could begin to cool. However, just as was the case during the historic February arctic outbreak, the core of the cold will likely remain west of the region on account of a fairly expansive western Atlantic ridge.  

 

The ENSO Region 1+2 anomaly was +0.2°C and the Region 3.4 anomaly was -0.7°C for the week centered around March 3. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged -0.87°C. La Niña conditions will likely prevail at least through most of March. Afterward, neutral-cool ENSO conditions will likely develop as the spring progresses.

 

The SOI was -8.09 today. The SOI has now been negative for 10 consecutive days. The last time that occurred was March 16-31, 2020 when the SOI was negative for 16 consecutive days. This development could be an early indication that what has been a fairly stable La Niña regime throughout the winter could be moving closer to its end stages.

 

The preliminary Arctic Oscillation (AO) figure was +2.094 today. Over the next few days, the AO is forecast to continue to rise sharply. The ensembles suggest that the AO could peak at or above +5.000. This would be a rare event in March. Since 1950, only March 7-8, 2015 saw the AO at or above +5.000. The March record is +5.588, which was set on March 8, 2015.

On March 8 the MJO was in Phase 8 at an amplitude of 1.022 (RMM). The March 7-adjusted amplitude was 0.758 (RMM).

 

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. Since January 1, New York City has picked up 28.1" snow.

 

Winters that saw December receive 10" or more snow, less than 10" in January, and then 10" or more in February in New York City, saw measurable snowfall in March or April in 83% of cases. Winter 2009-2010 was the exception where only a trace of snow was recorded. This group of winters saw 6" or more snow during the March-April period in 50% of the cases. All said, it is more likely than not that there will be measurable snowfall after February.  

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 53% probability that New York City will have a warmer than normal March. March will likely finish with a mean temperature near 43.0° (0.5° above normal).

 

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In much of the region, the temperature topped out in the upper 40s and lower 50s. However, from Philadelphia to Washington, DC, temperatures reached the upper 60s and lower 70s. That warm air will push northward tonight into tomorrow.

 

As a result, tomorrow and Friday will likely be the warmest days so far this year. Temperatures in the region will likely rise well into the 60s on both days. Some areas, including Philadelphia and Newark, will likely see temperatures top out in the 70s on one or both days.

 

Afterward, temperatures could begin to cool. However, just as was the case during the historic February arctic outbreak, the core of the cold will likely remain west of the region on account of a fairly expansive western Atlantic ridge.  

 

Further, since 1950, nearly 60% of days two weeks after the AO reached +3.000 or above in the March 1-15 period were warmer than when the AO reached +3.000 or above. The mean figure was 2.8°. This suggests that it is more likely than not that the closing week of March could see a return to warmer conditions.  

 

The ENSO Region 1+2 anomaly was +0.2°C and the Region 3.4 anomaly was -0.7°C for the week centered around March 3. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged -0.87°C. La Niña conditions will likely prevail at least through most of March. Afterward, neutral-cool ENSO conditions will likely develop as the spring progresses.

 

The SOI was +4.21 today. The SOI had been negative for 10 consecutive days. That development could be an early indication that what has been a fairly stable La Niña regime throughout the winter could be moving closer to its end stages.

 

The preliminary Arctic Oscillation (AO) figure was +3.476 today. Over the next few days, the AO is forecast to continue to rise sharply. The ensembles suggest that the AO could peak at or above +5.000. This would be a rare event in March. Since 1950, only March 7-8, 2015 saw the AO at or above +5.000. The March record is +5.588, which was set on March 8, 2015.

On March 9 the MJO was in Phase 1 at an amplitude of 1.092 (RMM). The March 8-adjusted amplitude was 1.010 (RMM).

 

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. Since January 1, New York City has picked up 28.1" snow.

 

Winters that saw December receive 10" or more snow, less than 10" in January, and then 10" or more in February in New York City, saw measurable snowfall in March or April in 83% of cases. Winter 2009-2010 was the exception where only a trace of snow was recorded. This group of winters saw 6" or more snow during the March-April period in 50% of the cases. All said, it is more likely than not that there will be measurable snowfall after February.  

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 50% probability that New York City will have a warmer than normal March. March will likely finish with a mean temperature near 43.0° (0.5° above normal).

 

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