December 2020 General Discussions & Observations Thread

[donsutherland1]

Following the December 16-17 snowstorm, the temperature anomaly in New York City's Central Park swung to negative values (0.1° below normal). Following the push of dry air into the region, temperatures rose into the middle 40s. As a result, the monthly departure has moved back to slightly above normal levels.

Overnight, parts of the region could see some rain and snow showers. Overcast skies will yield to partly sunny conditions tomorrow.

A strong storm could pass to the west of the region on Thursday bringing a period of moderate to heavy rain, high winds, and unseasonably warm temperatures before colder air returns afterward.

In the wake of that storm, the unseasonably warm air will be driven into Atlantic Canada where record high temperatures are likely Friday and perhaps Saturday. Unseasonably cold air will push into Florida. Record low temperatures are possible in some parts of the state, especially along the Gulf Coast and southern portions of the Florida Peninsula, on Friday.

The likely continuation of Arctic blocking into at least the first week of January will provide a higher than climatological probability for above normal snowfall for the December 21-January 10 period. The AO- is particularly important for moderate or significant snowfalls in the New York City and Philadelphia areas.

For the December 15-January 15, 1950-2020 period, the following percentages of select snowstorms have occurred when the AO was negative:

New York City:
4" or more: 66%
6" or more: 80%
10" or more: 86%

Philadelphia:
4" or more: 81%
6" or more: 85%
10" or more: 100%   

The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 16. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.57°C and the ENSO Region 3.4 anomaly has averaged -1.17°C. La Niña conditions will likely prevail at least through the winter.

The SOI was +21.12 today.

Today, the preliminary Arctic Oscillation (AO) figure was -1.141.

On December 20 the MJO was in Phase 6 at an amplitude of 1.162 (RMM). The December 19-adjusted amplitude was 1.031.

Based on the latest guidance, no significant stratospheric warming event is into the final days of December. The highest levels of the stratosphere will warm.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. The large snowfall that just took place provides a strong contrary signal to the below normal snowfall idea. Should blocking continue, the probability of above normal snowfall would likely increase.

The recent 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 into the start of January.

Based on sensitivity analysis applied to the latest guidance, there is an implied 60% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 38.0°.

 

[the_other_guy]

Temps stubbornly in the mid 40s in the city this evening.

That should do in a lot of the snow cover by morning sadly

[CIK62]

The next 8 days are averaging 36degs.(29/42).        Making it 31degs., or -3.0.

Month to date is  39.1[+.02].        Should be 36.9[-0.7]] by the 30th.

Possible snows on all models, dates/amts. differ.       CMC is 15"! for the 29th, the EURO is a Trace, the GFS is zippo there but likes Jan.1-3 for 2".     That's the basis of my "Would you believe a White New Years", joke from last week..

39*(90%RH) here at 6am.      Low was 38* at 5am.       42* by 10am.        46* by Noon.        47* at 1pm.       45* by 3pm.   

[bluewave]

NYC is on track for its first Christmas with a morning high of 55-60 and an evening low in the 20s. Our new era of big temperature swings continues. The previous coldest temperature on Christmas with such a warm high was 33° in 2008.

Data for December 25 - NY CITY CENTRAL PARK, NY
Click column heading to sort ascending, click again to sort descending.

Date	Max Temperature	Min Temperature	Precipitation	Snowfall	Snow Depth
2015-12-25	66	57	0.01	0.0	0
1982-12-25	64	41	0.02	0.0	0
1889-12-25	64	43	0.00	0.0	M
2014-12-25	62	44	0.09	0.0	0
1940-12-25	62	38	0.00	0.0	0
1979-12-25	61	50	0.87	0.0	0
1964-12-25	60	49	T	0.0	0
1994-12-25	59	41	T	0.0	0
1965-12-25	59	47	0.65	0.0	0
1932-12-25	59	47	0.13	0.0	0
1893-12-25	58	45	0.00	0.0	M
2008-12-25	57	33	0.13	0.0	0
1936-12-25	56	40	0.00	0.0	0
1933-12-25	55	34	0.00	0.0	0
1915-12-25	55	38	0.01	0.0	0

 

[donsutherland1]

Morning thoughts...

Today will become  partly to mostly sunny. It will be mild. Temperatures will likely top out in the lower and middle 40s across most of the region. Likely high temperatures around the region include:

New York City (Central Park): 44°

Newark: 46°

Philadelphia: 45°

A strong storm will impact the region Thursday into Friday. Moderate to heavy rain, high winds, and unseasonably mild readings ahead of the frontal passage early Friday can be expected later Thursday and Thursday night.

[bluewave]

Another El Niño-like feature that we are experiencing this month is the mild average temperature  combined with the 10”+ snow in NYC . Since 1995 , all the 35.9° or warmer Decembers with 10”+ were warmer ENSO years. The snowy La Niña Decembers all had a monthly average around 32° degrees. This month is already 39.1° before the big coming solstice warm up. An interesting question to ask is how long can we keep this Niño-like pattern going? I looks like January will at least start out more Niño-like. So it will be interesting to see which ENSO type pattern shows up in February.

Warmest Decembers highlighted...NYC snowfall....average temperature....Niño 3.4 temperature....

Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec
Click column heading to sort ascending, click again to sort descending.

Rank	Year	Total Snowfall	Temp/ Niño 3.4
1	2010	20.1	32.8/-1.6
2	2003	19.8	37.6/+0.4
3	2000	13.4	31.1/-0.7
4	2009	12.4	35.9/+1.6
5	1995	11.5	32.4/-1.0
6	2002	11.0	36.0/+1.1
7	2020	10.5	39.1/-1.2

[LibertyBell]

4 minutes ago, bluewave said:

Another El Niño-like feature that we are experiencing this month is the mild temperatures combined with the 10”+ snow in NYC . Since 1995 , all the 35.9° or warmer Decembers with 10”+ were warmer ENSO years. The snowy La Niña Decembers all had a monthly average around 32° degrees. This month is already 39.1° before the big coming solstice warm up. An interesting question to ask is how long can we keep this Niño-like pattern going? I looks like January will at least start out more Niño-like. So it will be interesting to see which ENSO type pattern shows up in February.

Warmest Decembers highlighted...NYC snowfall....average temperature....Niño 3.4 temperature....

Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec
Click column heading to sort ascending, click again to sort descending.

Rank	Year	Total Snowfall	Temp/ Niño 3.4
1	2010	20.1	32.8/-1.6
2	2003	19.8	37.6/+0.4
3	2000	13.4	31.1/-0.7
4	2009	12.4	35.9/+1.6
5	1995	11.5	32.4/-1.0
6	2002	11.0	36.0/+1.1
7	2020	10.5	39.1/-1.2

this is part of our new climate so it's not surprising Chris.....milder winters with more snowfall (and more rainfall) has become the norm now.

Also it wouldn't be a shock for the pattern to break down as we approach February, patterns usually last from 4-8 weeks before they break, but I also wouldn't be surprised if it returned again later, a la 1995-96.  Even in 2010-11 we actually returned to a somewhat snowy pattern again in March.

 

[snowman19]

16 minutes ago, bluewave said:

Another El Niño-like feature that we are experiencing this month is the mild average temperature  combined with the 10”+ snow in NYC . Since 1995 , all the 35.9° or warmer Decembers with 10”+ were warmer ENSO years. The snowy La Niña Decembers all had a monthly average around 32° degrees. This month is already 39.1° before the big coming solstice warm up. An interesting question to ask is how long can we keep this Niño-like pattern going? I looks like January will at least start out more Niño-like. So it will be interesting to see which ENSO type pattern shows up in February.

Warmest Decembers highlighted...NYC snowfall....average temperature....Niño 3.4 temperature....

Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec
Click column heading to sort ascending, click again to sort descending.

Rank	Year	Total Snowfall	Temp/ Niño 3.4
1	2010	20.1	32.8/-1.6
2	2003	19.8	37.6/+0.4
3	2000	13.4	31.1/-0.7
4	2009	12.4	35.9/+1.6
5	1995	11.5	32.4/-1.0
6	2002	11.0	36.0/+1.1
7	2020	10.5	39.1/-1.2

@bluewave@donsutherland1 People who have written this La Niña off as dying may want to reconsider. A massive trade wind surge is coming. Region 3.4 is about to see an SST drop again. Maybe the CFS idea of a secondary peak in January isn’t so crazy after all: 

[LibertyBell]

16 minutes ago, bluewave said:

Another El Niño-like feature that we are experiencing this month is the mild average temperature  combined with the 10”+ snow in NYC . Since 1995 , all the 35.9° or warmer Decembers with 10”+ were warmer ENSO years. The snowy La Niña Decembers all had a monthly average around 32° degrees. This month is already 39.1° before the big coming solstice warm up. An interesting question to ask is how long can we keep this Niño-like pattern going? I looks like January will at least start out more Niño-like. So it will be interesting to see which ENSO type pattern shows up in February.

Warmest Decembers highlighted...NYC snowfall....average temperature....Niño 3.4 temperature....

Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec
Click column heading to sort ascending, click again to sort descending.

Rank	Year	Total Snowfall	Temp/ Niño 3.4
1	2010	20.1	32.8/-1.6
2	2003	19.8	37.6/+0.4
3	2000	13.4	31.1/-0.7
4	2009	12.4	35.9/+1.6
5	1995	11.5	32.4/-1.0
6	2002	11.0	36.0/+1.1
7	2020	10.5	39.1/-1.2

Chris, what's your opinion of the New Year's Day possible storm?  I see that as still being a bit too soon for a big wintry storm here, maybe more of a mix to rain scenario.  The "big one" (if it does occur) should be in early January, perhaps in the Jan 5-10 range.

 

[bluewave]

25 minutes ago, snowman19 said:

@bluewave@donsutherland1 People who have written this La Niña off as dying may want to reconsider. A massive trade wind surge is coming. Region 3.4 is about to see an SST drop again. Maybe the CFS idea of a secondary peak in January isn’t so crazy after all: 

 

We have seen these strong trade wind surges and Niño 3.4 dipping temperatures back to the fall. All the competing influences have resulted in a more Niño-like pattern. Notice how the PNA is forecast to stay positive right into January. Beyond early January, it will be interesting to see which type ENSO  pattern prevails.

 

[donsutherland1]

42 minutes ago, snowman19 said:

@bluewave@donsutherland1 People who have written this La Niña off as dying may want to reconsider. A massive trade wind surge is coming. Region 3.4 is about to see an SST drop again. Maybe the CFS idea of a secondary peak in January isn’t so crazy after all: 

I continue to believe that proclamations that the La Niña is near its demise are premature. The trade winds have been strong for some time now (the SOI was even +30 or above for three consecutive days for the first time since January 2012), and are forecast to strengthen further. One already saw a fairly sharp cooling in Region 1+2 over the past week. Through February, I believe a gradual fade is more likely than a collapse. Overall, the DJF tri-monthly period will likely have an ENSO anomaly consistent with La Niña.

[SnoSki14]

If the Nino state is maintained that would have vast repercussions on all those Feb torch forecasts. 

As of now it looks like the blockiness will carry on. We've seen months of blockiness in the spring/summer months...I wonder if it'll maintain through winter. 

[MJO812]

1 hour ago, snowman19 said:

@bluewave@donsutherland1 People who have written this La Niña off as dying may want to reconsider. A massive trade wind surge is coming. Region 3.4 is about to see an SST drop again. Maybe the CFS idea of a secondary peak in January isn’t so crazy after all: 

 

[MJO812]

17 minutes ago, donsutherland1 said:

I continue to believe that proclamations that the La Niña is near its demise are premature. The trade winds have been strong for some time now (the SOI was even +30 or above for three consecutive days for the first time since January 2012), and are forecast to strengthen further. One already saw a fairly sharp cooling in Region 1+2 over the past week. Through February, I believe a gradual fade is more likely than a collapse. Overall, the DJF tri-monthly period will likely have an ENSO anomaly consistent with La Niña.

Many people  including meteorologists  think La Nina is about to  die.

[MJO812]

Loving these 

[LibertyBell]

41 minutes ago, bluewave said:

We have seen these strong trade wind surges and Niño 3.4 dipping temperatures back to the fall. All the competing influences have resulted in a more Niño-like pattern. Notice how the PNA is forecast to stay positive right into January. Beyond early January, it will be interesting to see which type ENSO  pattern prevails.

 

right and these competing patterns end up being more important than ENSO itself.  I'd also be curious to see the impact of the background warming state, as the Pacific warms, we may see more of these so-called "nino type" patterns in other ENSO conditions also.  That's why it's a misnomer to consider them "ENSO type" patterns when other influences are obviously more important, especially the background warming state and the predilection of blocking.

 

[LibertyBell]

6 minutes ago, MJO812 said:

Loving these 

best indicators for this time of the year since 1995-96 and 2010-11

 

[LibertyBell]

24 minutes ago, donsutherland1 said:

I continue to believe that proclamations that the La Niña is near its demise are premature. The trade winds have been strong for some time now (the SOI was even +30 or above for three consecutive days for the first time since January 2012), and are forecast to strengthen further. One already saw a fairly sharp cooling in Region 1+2 over the past week. Through February, I believe a gradual fade is more likely than a collapse. Overall, the DJF tri-monthly period will likely have an ENSO anomaly consistent with La Niña.

keeping it more in the weak to low end moderate range would be far better for our wintry prospects, as some epic snowfall seasons have had that combo.  and as you yourself said, Don, AO/NAO impacts our winters far more than anything else does.

 

 

[bluewave]

17 minutes ago, LibertyBell said:

right and these competing patterns end up being more important than ENSO itself.  I'd also be curious to see the impact of the background warming state, as the Pacific warms, we may see more of these so-called "nino type" patterns in other ENSO conditions also.  That's why it's a misnomer to consider them "ENSO type" patterns when other influences are obviously more important, especially the background warming state and the predilection of blocking.

 

We started to see these ENSO disconnects when the 15-16 super El Niño California rainfall got delayed into the 16-17 La Niña. Then it was off to the races when the El Niño didn’t couple in 18-19. Last winter we saw weak El Niño conditions produce an 11-12 style La Niña pattern. So it’s no surprise we are getting an El Niño-like pattern with a moderate La Niña.

[LibertyBell]

8 minutes ago, bluewave said:

We started to see these ENSO disconnects when the 15-16 super El Niño California rainfall got delayed into the 16-17 La Niña. Then it was off to the races when the El Niño didn’t couple in 18-19. Last winter we saw weak El Niño conditions produce an 11-12 style La Niña pattern. So it’s no surprise we are getting an El Niño-like pattern with a moderate La Niña.

where does the warming state of the planet fit into this.....parts of the north pac have been scorching all season.

 

[donsutherland1]

31 minutes ago, MJO812 said:

Many people  including meteorologists  think La Nina is about to  die.

Yes, there are differences of opinion. My belief is that the La Niña is more likely to fade than collapse. The most recent ENSO anomalies and the trade wind forecast suggest that this line of thinking of a slower decay has merit. Ultimately, we'll see how things turn out.

[LibertyBell]

1 minute ago, donsutherland1 said:

Yes, there are differences of opinion. My belief is that the La Niña is more likely to fade than collapse. The most recent ENSO anomalies and the trade wind forecast suggest that this line of thinking of a slower decay has merit. Ultimately, we'll see how things turn out.

chances of this becoming a "strong" la nina though have greatly diminished.

[donsutherland1]

2 minutes ago, LibertyBell said:

chances of this becoming a "strong" la nina though have greatly diminished.

I agree. I believe it will be classified as a moderate event when all is said and done.

[Allsnow]

1 hour ago, snowman19 said:

@bluewave@donsutherland1 People who have written this La Niña off as dying may want to reconsider. A massive trade wind surge is coming. Region 3.4 is about to see an SST drop again. Maybe the CFS idea of a secondary peak in January isn’t so crazy after all: 

Niña is dead 

 

 

[bluewave]

11 minutes ago, LibertyBell said:

where does the warming state of the planet fit into this.....parts of the north pac have been scorching all season.

 

The warming state of the planet has been the ultimate competing influence.

 

[LibertyBell]

Yikes!

 

[LibertyBell]

that should be GOA though not GOM.

 

There's a guy in that thread named Jim Hughes, why does that name sound familiar?

 

[LibertyBell]

also this

 

[the_other_guy]

4 hours ago, LibertyBell said:

this is part of our new climate so it's not surprising Chris.....milder winters with more snowfall (and more rainfall) has become the norm now.

Also it wouldn't be a shock for the pattern to break down as we approach February, patterns usually last from 4-8 weeks before they break, but I also wouldn't be surprised if it returned again later, a la 1995-96.  Even in 2010-11 we actually returned to a somewhat snowy pattern again in March.

 

Agreed. If you get within a degree of normal, you have to consider that a cool departure 20 years ago. 

The whole baseline has been reset even if we are still waiting on new averages

[uncle W]

these are the years with at least one day having a -5sd AO...since 1950...

1959-60.....11/18...11/19...

1962-63.....01/21...

1965-66.....01/28...

1968-69.....02/13...02/15...

1969-70.....03/04...03/05...03/06...03/07...03/08...03/09...03/10...

1976-77.....12/28...12/29...01/11...01/12..01/13...01/14...01/15...01/16...01/17

1977-78.....02/05...02/06...

1984-85.....01/18...01/19...01/20...

2002-03.....10/18...

2009-10.....12/20...12/21...12/22...12/23...12/24...12/25...01/03...01/04...01/05...01/06...02/06...02/14...

2010-11.....12/18...

2012-13.....03/19...03/20...03/21...03/22...

.....................................................................

dates..................-AO

1...01/15/1977.....-7.433...

2...01/16/1977.....-7.331...

3...01/14/1977.....-7.311...

4...01/13/1977.....-6.520...

5...03/05/1970.....-6.365...

6...01/19/1985.....-6.226...

7...01/17/1977.....-6.168...

8...03/06/1970.....-6.114...

9...03/04/1970.....-5.918...

10 11/18/1959.....-5.896...

 

11 12/21/2009.....-5.821...

12 01/12/1977.....-5.802...

13 01/18/1985.....-5.693...

14 03/20/2013.....-5.688...

15 01/20/1985.....-5.581...

16 12/23/2009.....-5.577...

17 11/19/1959.....-5.545...

18 01/03/2010.....-5.533...

19 03/07/1970.....-5.525...

20 03/09/1970.....-5.519...

 

21 12/22/2009.....-5.508...

22 01/04/2010.....-5.403...

23 03/21/2013.....-5.399...

24 01/02/2010.....-5.384...

25 12/20/2009.....-5.341...

26 01/11/1977.....-5.333...

27 03/08/1970.....-5.320...

28 02/05/1978.....-5.291...

29 12/29/1976.....-5.287...

30 02/13/1969.....-5.282...

 

31 12/18/2010.....-5.265...

32 12/24/2009.....-5.256...

33 03/22/2013.....-5.240...

34 12/28/1976.....-5.206...

35 02/06/2010.....-5.205...

36 03/19/2013.....-5.193...

37 01/05/2010.....-5.180...

38 02/14/2010.....-5.132...

39 01/28/1966.....-5.130...

40 03/10/1970.....-5.115...

 

41 02/15/1969.....-5.102...

42 10/18/2002.....-5.098...

43 12/25/2009.....-5.052...

44 02/06/1978.....-5.026...

45 01/21/1963.....-5.010...