December 2024

[Neblizzard]

3 hours ago, NEG NAO said:

Plenty of Blocking potential up north too.......

This could potentially produce . That’s a lot of blocking if the models are right 

[JerseyWx]

This has been a pretty cold month out this way, numerous nights in the teens and low 20's.  That's below normal, and it's not like our daytime highs have been scorching either.

7 inches so far, I think we're off to a fine start.  Way too much talk of torching and warmth imo.

[donsutherland1]

New York City received its first measurable snowfall of the year today after seeing only a trace yesterday.

Storm total snowfall amounts included:

Boston: 5.2"
Islip: 2.0"
New York City: 1.8"
Newark: 2.5"
Philadelphia: 0.1"

Last winter, New York City's first measurable snowfall occurred on January 6, 2024. The prior winter, it occurred on a record late February 1, 2023. The last earlier first measurable snowfall occurred on December 16, 2020. Normal is December 13th.

In the wake of the snowfall, the coldest air so far this season is pouring into the region. The temperature will fall into the teens for the first time this season in New York City and Philadelphia tomorrow morning and then again on Monday morning. Many areas outside those cities will likely experience single-digit lows. High temperatures tomorrow will range from the middle 20s in New York City to the upper 20s in Philadelphia.

The cold will begin to recede around the middle of next week.  December will likely close with above normal temperatures. The opening days of January will likely also begin with above normal temperatures, but it will start to turn colder. Snowfall prospects will remain limited through the end of December. However, the pattern could become more favorable for moderate or perhaps larger snowfalls as the cold returns during the first week of January.

On account of a lack of snowfall, 2023-2024 will likely set a new records for the lowest snowfall over a two-year period for Boston and New York City.

Boston: 2023-2024 Total to Date: 26.7"; Record: 38.2", 1979-1980
New York City: 2023-2024 Total to Date: 11.6"; Record: 17.4", 1997-1998

In past days, an occasional run of the operational GFS showed a significant snowstorm from Washington, DC to New York City. However, the pattern makes such an event very unlikely for this region. Since 1950, there were 5 December snowstorms that brought 6" or more snow to all three of these cities. Four (80%) occurred with a PNA+/NAO- pattern. The NAO is forecast to be positive. In addition, three (60%) occurred when the MJO was in Phase 8, which is not likely over the next 10 days. Only the December 23-25, 1966 event produced 6" or more snow in all three cities with a positive NAO, but the AO was strongly negative (< -2.000), which is not likely during the next 10 days. In sum, the interior sections will be far more favored for an appreciable or perhaps greater snowfall than the Washington-Baltimore-Philadelphia-New York City area over the next 10 days. A smaller snowfall remains plausible, as occurred during December 20-21.

The NAO fell to a preliminary -2.751 on September 24th (all-time September record: -2.371, September 12, 1971). That was the 9th lowest value on record. La Niña winters following September cases where the NAO fell to -1.900 or below featured a predominantly positive NAO. The most recent such winters were 2016-2017 and 2022-2023. The mean temperatures for those winters in New York City were 39.3° and 41.0° respectively. The 1991-2020 normal value is 36.2°. A warmer to much warmer than normal outcome is favored by the November run of the ECMWF for Winter 2024-2025.

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.6°C for the week centered around December 11. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.17°C and the ENSO Region 3.4 anomaly has averaged -0.27°C. Neutral ENSO conditions may still evolve into a La Niña event during the winter. Uncertainty as to whether a La Niña will actually develop continues to increase. Currently, 47% of dynamical models and 22% of the statistical models forecast the development of a La Niña.

The SOI was +12.92 today.

The preliminary Arctic Oscillation (AO) was +0.325 today.

Based on sensitivity analysis applied to the latest guidance, there is an implied 83% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 37.4° (1.7° below normal).

 

[LibertyBell]

20 minutes ago, donsutherland1 said:

New York City received its first measurable snowfall of the year today after seeing only a trace yesterday.

Storm total snowfall amounts included:

Boston: 5.2"
Islip: 2.0"
New York City: 1.8"
Newark: 2.5"
Philadelphia: 0.1"

Last winter, New York City's first measurable snowfall occurred on January 6, 2024. The prior winter, it occurred on a record late February 1, 2023. The last earlier first measurable snowfall occurred on December 16, 2020. Normal is December 13th.

In the wake of the snowfall, the coldest air so far this season is pouring into the region. The temperature will fall into the teens for the first time this season in New York City and Philadelphia tomorrow morning and then again on Monday morning. Many areas outside those cities will likely experience single-digit lows. High temperatures tomorrow will range from the middle 20s in New York City to the upper 20s in Philadelphia.

The cold will begin to recede around the middle of next week.  December will likely close with above normal temperatures. The opening days of January will likely also begin with above normal temperatures, but it will start to turn colder. Snowfall prospects will remain limited through the end of December. However, the pattern could become more favorable for moderate or perhaps larger snowfalls as the cold returns during the first week of January.

On account of a lack of snowfall, 2023-2024 will likely set a new records for the lowest snowfall over a two-year period for Boston and New York City.

Boston: 2023-2024 Total to Date: 26.7"; Record: 38.2", 1979-1980
New York City: 2023-2024 Total to Date: 11.6"; Record: 17.4", 1997-1998

In past days, an occasional run of the operational GFS showed a significant snowstorm from Washington, DC to New York City. However, the pattern makes such an event very unlikely for this region. Since 1950, there were 5 December snowstorms that brought 6" or more snow to all three of these cities. Four (80%) occurred with a PNA+/NAO- pattern. The NAO is forecast to be positive. In addition, three (60%) occurred when the MJO was in Phase 8, which is not likely over the next 10 days. Only the December 23-25, 1966 event produced 6" or more snow in all three cities with a positive NAO, but the AO was strongly negative (< -2.000), which is not likely during the next 10 days. In sum, the interior sections will be far more favored for an appreciable or perhaps greater snowfall than the Washington-Baltimore-Philadelphia-New York City area over the next 10 days. A smaller snowfall remains plausible, as occurred during December 20-21.

The NAO fell to a preliminary -2.751 on September 24th (all-time September record: -2.371, September 12, 1971). That was the 9th lowest value on record. La Niña winters following September cases where the NAO fell to -1.900 or below featured a predominantly positive NAO. The most recent such winters were 2016-2017 and 2022-2023. The mean temperatures for those winters in New York City were 39.3° and 41.0° respectively. The 1991-2020 normal value is 36.2°. A warmer to much warmer than normal outcome is favored by the November run of the ECMWF for Winter 2024-2025.

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.6°C for the week centered around December 11. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.17°C and the ENSO Region 3.4 anomaly has averaged -0.27°C. Neutral ENSO conditions may still evolve into a La Niña event during the winter. Uncertainty as to whether a La Niña will actually develop continues to increase. Currently, 47% of dynamical models and 22% of the statistical models forecast the development of a La Niña.

The SOI was +12.92 today.

The preliminary Arctic Oscillation (AO) was +0.325 today.

Based on sensitivity analysis applied to the latest guidance, there is an implied 83% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 37.4° (1.7° below normal).

 

1966-67 was an absolutely amazing winter, starting with that big Christmas snowstorm.  Don't see anything like that happening this winter, the only real resemblance is that 1966 was a drier than normal year and was also transitioning from an el nino to a la nina (or was it cold neutral?) if I remember correctly.

That 37.4 is considered 1.7 below normal for December is absolutely wild Don..... I remember when our December normal was around 36 degrees.  Does normal or average even mean anything anymore?

Also wild Don, before this storm the NYC two year snowfall was under 10 inches?

[steve392]

29 was the high at work, felt wayyy colder with the winds whipping up.  currently 24 degrees.

[Roger Smith]

2 hours ago, LibertyBell said:

that one on 11/22 in 2018 really stands out, was that one of the earliest ones on record, Chris?

 

I was interested in this too so I looked it up ...

only five years had an earlier sub-20F reading after 1905 hit 20F on Nov 14 and 1967 on Nov 15 (and 16). You could say only seven years if you counted those two, no other years hit 20F and no colder before 2018 joined the slowly expanding list. 1880 joined the club on the same date as 2018 but with lower (and still record) readings so that would add one more beating 2018 if the colder reading counts. 

These years below 20F in order of earliest dates are

1933 _ 17F on Nov 16, 19F on Nov 17

1924 _ 19F on Nov 17 (tied by 1933)

1936 _ 18F on Nov 18, 1924 another 19F

(1936 repeated 18F on 19th; Nov 20th has never been below record of 21F set in 1873)

1879 _ 16F on Nov 21, this was the earliest before 1924 despite the much less developed urban heat island

1987 _ 18F on Nov 21, first year to join sub-20F group not to set a daily record when doing so.

1880 _ 13F on Nov 22, prevented 2018 from setting a record with its 17F (also 1987 had 19F)

1880 _ 14F on Nov 23 also prevented 2018 from setting a record with 15F (also 1888 had 19F)

 

From Nov 24 to 30, the following years joined the sub-20F list: 

Nov 24_ no new members, 1880 hit 14F again

Nov 25_ 1938 became 9th year (19F)

Nov 26_ 1932 joined, 19F was not a record as 16F in 1880 later tied by 1938.

Nov 27_ 1903 and 1917 (tied 19F) joined, their record was broken by 12F in 1932.

Nov 28_ 1871 (16F), 1890 (19F), 1901 (19F), 1930 (15F) eventual record low, were years 13 to 16 joining sub-20 list. 

Nov 29_ 1875 (14F) after 1871,72 at 15F, 1891 at 17F, 1929 and 1930 at 18F, 1955 (15F) (five of seven new to list for total of 21 so far)

Nov 30_ 1875 (5F) is Nov record low, 1871 another 15F and 1872t91 (14F), new were 1887 (14F), 1958 (18F) and 1976 (17F) making it 24 years sub-20F by end of November. ... 1929 had 12F and 1936 17F (were already in list). 

 

Not only was 2018 a standout, 2017 and 2019 set early marks of 24F (11th 2017 tied 9th 1976 as second coldest so early), and 23F (13th 2019 was colder at that date than any previous year except for 23F on Nov 6, 1879). 

 

[CPcantmeasuresnow]

1 hour ago, donsutherland1 said:

New York City received its first measurable snowfall of the year today after seeing only a trace yesterday.

Storm total snowfall amounts included:

Boston: 5.2"
Islip: 2.0"
New York City: 1.8"
Newark: 2.5"
Philadelphia: 0.1"

Last winter, New York City's first measurable snowfall occurred on January 6, 2024. The prior winter, it occurred on a record late February 1, 2023. The last earlier first measurable snowfall occurred on December 16, 2020. Normal is December 13th.

In the wake of the snowfall, the coldest air so far this season is pouring into the region. The temperature will fall into the teens for the first time this season in New York City and Philadelphia tomorrow morning and then again on Monday morning. Many areas outside those cities will likely experience single-digit lows. High temperatures tomorrow will range from the middle 20s in New York City to the upper 20s in Philadelphia.

The cold will begin to recede around the middle of next week.  December will likely close with above normal temperatures. The opening days of January will likely also begin with above normal temperatures, but it will start to turn colder. Snowfall prospects will remain limited through the end of December. However, the pattern could become more favorable for moderate or perhaps larger snowfalls as the cold returns during the first week of January.

On account of a lack of snowfall, 2023-2024 will likely set a new records for the lowest snowfall over a two-year period for Boston and New York City.

Boston: 2023-2024 Total to Date: 26.7"; Record: 38.2", 1979-1980
New York City: 2023-2024 Total to Date: 11.6"; Record: 17.4", 1997-1998

In past days, an occasional run of the operational GFS showed a significant snowstorm from Washington, DC to New York City. However, the pattern makes such an event very unlikely for this region. Since 1950, there were 5 December snowstorms that brought 6" or more snow to all three of these cities. Four (80%) occurred with a PNA+/NAO- pattern. The NAO is forecast to be positive. In addition, three (60%) occurred when the MJO was in Phase 8, which is not likely over the next 10 days. Only the December 23-25, 1966 event produced 6" or more snow in all three cities with a positive NAO, but the AO was strongly negative (< -2.000), which is not likely during the next 10 days. In sum, the interior sections will be far more favored for an appreciable or perhaps greater snowfall than the Washington-Baltimore-Philadelphia-New York City area over the next 10 days. A smaller snowfall remains plausible, as occurred during December 20-21.

The NAO fell to a preliminary -2.751 on September 24th (all-time September record: -2.371, September 12, 1971). That was the 9th lowest value on record. La Niña winters following September cases where the NAO fell to -1.900 or below featured a predominantly positive NAO. The most recent such winters were 2016-2017 and 2022-2023. The mean temperatures for those winters in New York City were 39.3° and 41.0° respectively. The 1991-2020 normal value is 36.2°. A warmer to much warmer than normal outcome is favored by the November run of the ECMWF for Winter 2024-2025.

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.6°C for the week centered around December 11. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.17°C and the ENSO Region 3.4 anomaly has averaged -0.27°C. Neutral ENSO conditions may still evolve into a La Niña event during the winter. Uncertainty as to whether a La Niña will actually develop continues to increase. Currently, 47% of dynamical models and 22% of the statistical models forecast the development of a La Niña.

The SOI was +12.92 today.

The preliminary Arctic Oscillation (AO) was +0.325 today.

Based on sensitivity analysis applied to the latest guidance, there is an implied 83% probability that New York City will have a colder than normal December (1991-2020 normal). December will likely finish with a mean temperature near 37.4° (1.7° below normal).

 

Question Don, do you believe the Central Park measurement of 1.8 to be accurate? It is apparently low again, as it usually is.

They can't ever seem to get it straight, and the last several years it seems even worse. Not actually having an observer or office there really makes it a joke. They should either used trained spotters for snow  totals or just give LGA as the snow measurements.

Curious of your thoughts on that.

[LibertyBell]

16 minutes ago, Roger Smith said:

I was interested in this too so I looked it up ...

only five years had an earlier sub-20F reading after 1905 hit 20F on Nov 14 and 1967 on Nov 15 (and 16). You could say only seven years if you counted those two, no other years hit 20F and no colder before 2018 joined the slowly expanding list. 1880 joined the club on the same date as 2018 but with lower (and still record) readings so that would add one more beating 2018 if the colder reading counts. 

These years below 20F in order of earliest dates are

1933 _ 17F on Nov 16, 19F on Nov 17

1924 _ 19F on Nov 17 (tied by 1933)

1936 _ 18F on Nov 18, 1924 another 19F

(1936 repeated 18F on 19th; Nov 20th has never been below record of 21F set in 1873)

1879 _ 16F on Nov 21, this was the earliest before 1924 despite the much less developed urban heat island

1987 _ 18F on Nov 21, first year to join sub-20F group not to set a daily record when doing so.

1880 _ 13F on Nov 22, prevented 2018 from setting a record with its 17F (also 1987 had 19F)

1880 _ 14F on Nov 23 also prevented 2018 from setting a record with 15F (also 1888 had 19F)

 

From Nov 24 to 30, the following years joined the sub-20F list: 

Nov 24_ no new members, 1880 hit 14F again

Nov 25_ 1938 became 9th year (19F)

Nov 26_ 1932 joined, 19F was not a record as 16F in 1880 later tied by 1938.

Nov 27_ 1903 and 1917 (tied 19F) joined, their record was broken by 12F in 1932.

Nov 28_ 1871 (16F), 1890 (19F), 1901 (19F), 1930 (15F) eventual record low, were years 13 to 16 joining sub-20 list. 

Nov 29_ 1875 (14F) after 1871,72 at 15F, 1891 at 17F, 1929 and 1930 at 18F, 1955 (15F) (five of seven new to list for total of 21 so far)

Nov 30_ 1875 (5F) is Nov record low, 1871 another 15F and 1872t91 (14F), new were 1887 (14F), 1958 (18F) and 1976 (17F) making it 24 years sub-20F by end of November. ... 1929 had 12F and 1936 17F (were already in list). 

 

Not only was 2018 a standout, 2017 and 2019 set early marks of 24F (11th 2017 tied 9th 1976 as second coldest so early), and 23F (13th 2019 was colder at that date than any previous year except for 23F on Nov 6, 1879). 

 

Interesting Roger, so there's been no below 20 temps before November 15th?

Looks like 1987 was the only other year in this list in my lifetime, the same year we had the Veteran's Day snowstorm?

Surprised that 1976 isn't on this list since it was such a cold fall and early winter.

Nevermind  I just saw that 1976 made the list on the final day.

[donsutherland1]

3 minutes ago, CPcantmeasuresnow said:

Question Don, do you believe the Central Park measurement of 1.8 to be accurate? It is apparently low again, as it usually is.

They can't ever seem to get it straight, and the last several years it seems even worse. Not actually having an observer or office there really makes it a joke. They should either used trained spotters for snow  totals or just give LGA as the snow measurements.

Curious of your thoughts on that.

I thought that it would come in at 2” or a little above based on reports in the Bronx and Manhattan. I suspect that the measurements occurred at 7 am and again at 1 pm, which would miss the snow that fell after 7 am.

[donsutherland1]

5 minutes ago, LibertyBell said:

Interesting Roger, so there's been no below 20 temps before November 15th?

 

Yes. That’s correct for Central Park.

[wishcast_hater]

So a few days ago everyone was writing off winter and waiting for the “torch”. My how things have changed in the past day.


.

[SACRUS]

Down and down we go

 

[LibertyBell]

11 minutes ago, donsutherland1 said:

I thought that it would come in at 2” or a little above based on reports in the Bronx and Manhattan. I suspect that the measurements occurred at 7 am and again at 1 pm, which would miss the snow that fell after 7 am.

Don what were the final liquid equivalents for the three local airports plus the Park? Thanks!

[Blizzwalker]

The La Nina--"3 inches or more in December" rule for NYC. In above posts, it's mentioned that this rule has generally yielded correct predictions for remainder of winter snowfall in NYC.  

It's been mostly correct since 95-96.  So the LaNina winters over last 29 years. It's been some time since I took statistics, but a sample size of 14 seems quite small to use in claiming a strong correlation between La Nina December snow and winter total.  Sure, there is this small sample appearing to offer predictive power, but does it stand up if a bigger sample is used ? I know weather records only go back so far, but does anyone have data about this relationship for last 50 years ? 100 years ? My point is unless a bigger sample is used, maybe we should be cautious in how much we rely on this rule.

[donsutherland1]

1 hour ago, LibertyBell said:

Don what were the final liquid equivalents for the three local airports plus the Park? Thanks!

For today's measurable snowfall: JFK: 0.12"; LGA: 0.12"; NYC: 0.15"

[SnowGoose69]

1 hour ago, Blizzwalker said:

The La Nina--"3 inches or more in December" rule for NYC. In above posts, it's mentioned that this rule has generally yielded correct predictions for remainder of winter snowfall in NYC.  

It's been mostly correct since 95-96.  So the LaNina winters over last 29 years. It's been some time since I took statistics, but a sample size of 14 seems quite small to use in claiming a strong correlation between La Nina December snow and winter total.  Sure, there is this small sample appearing to offer predictive power, but does it stand up if a bigger sample is used ? I know weather records only go back so far, but does anyone have data about this relationship for last 50 years ? 100 years ? My point is unless a bigger sample is used, maybe we should be cautious in how much we rely on this rule.

Too much of it is luck though and the sample size is still small.  For example, everything imaginable went wrong in December 89, it almost happened again in 2000, but chances were there all month long both years.  2000-2001 would have averaged below normal without the 12/30 storm obviously, so I guess the predictive measure the winter finishes below normal is a good one.  But the rest of the winter being poor snow wise, not so much as if not for that remarkably lucky storm we'd still have had 23 inches of snow in Jan/Feb/Mar of 2001 which is darn good.

[Nibor]

January might be fun if the ensembles verify. 

[North and West]

So a few days ago everyone was writing off winter and waiting for the “torch”. My how things have changed in the past day.


.

.

[LoboLeader1]

Currently 6 here in the Berkshires as of 11PM. 

[the_other_guy]

Well if CPK under measured, and its closer to 2.5, that is close enough to 3 for me! Good winter ahead! haha

 

But seriously