December 2020 General Discussions & Observations Thread

[MJO812]

27 minutes ago, LibertyBell said:

maybe it'll hold off until Groundhog day, a la Jan 2011.

 

April would be better

[MJO812]

31 minutes ago, LibertyBell said:

when will that big rain and wind storm end that we're supposed to get?  right before the cold comes charging in?  so no precip on Christmas day?

 

Yes

Overnight Christmas Eve into early morning 

Temps will tumble  after that

[snowman19]

55 minutes ago, MJO812 said:

April would be better

If the tropical convective forcing moves to the Maritime Continent in late January, as is the typical canonical La Niña progression, people won’t be asking “where is the La Niña pattern?” anymore come February 

[mikem81]

Anyone in here have the links to the Euro tellies? I only have the GFS based ones.

[LibertyBell]

1 hour ago, donsutherland1 said:

Unfortunately, it will likely be mostly cloudy to completely overcast.

Now you see why I want geo-engineering so bad, imagine if we had the power to suck clouds right out of the air to see magnificent spectacles like this.

[LibertyBell]

34 minutes ago, snowman19 said:

If the tropical convective forcing moves to the Maritime Continent in late January, as is the typical canonical La Niña progression, people won’t be asking “where is the La Niña pattern?” anymore come February 

there is no such thing as "el nino" or "la nina" patterns, it's all about blocking or lack thereof

[MJO812]

3 minutes ago, LibertyBell said:

there is no such thing as "el nino" or "la nina" patterns, it's all about blocking or lack thereof

Agree

[LibertyBell]

1 minute ago, MJO812 said:

Agree

we've seen way too many el ninos produce very little snow and some of our biggest snowfall seasons of all time have been la ninas, some of them are front loaded, some are backloaded and some are both.  You cant cookie cutter our snowfall patterns into specific ENSO scenarios, if you could long range forecasting would be a lot easier.

 

[MJO812]

Gfs is pretty stormy at the end of this month into January. If blocking develops then watch out.

[Heisy]

For coastal plain I’d be more interested in the second wave length event. I think the redeveloping clipper could change to snow for nyc if you get a closed ULL at the right spot, but the hp source is better after 

[bluewave]

2 hours ago, mikem81 said:

Anyone in here have the links to the Euro tellies? I only have the GFS based ones.

The Euro has one of the strongest south based blocks that we have seen this time of year. It has a whopping +6 SD 500 mb height anomaly just south of Greenland. A 584 dm ridge east of Newfoundland should be very close to the record in late December.

[Stormlover74]

42. The melting has commenced 

45 now

[donsutherland1]

Some drier air has worked in, so there may be several hours of partly to mostly sunny skies in parts of the region. That should leader to temperatures running several degrees above modeled highs. 

[Brian5671]

32 minutes ago, bluewave said:

The Euro has one of the strongest south based blocks that we have seen this time of year. It has a whopping +6 SD 500 mb height anomaly just south of Greenland. A 584 dm ridge east of Newfoundland should be very close to the record in late December.

that could suppress the storm track way south-like 09-10

[Brian5671]

up to 41 here-warmest it's been in since a week ago Sunday

[MJO812]

22 minutes ago, Brian5671 said:

up to 41 here-warmest it's been in since a week ago Sunday

45 here

[North and West]

1 hour ago, donsutherland1 said:

Some drier air has worked in, so there may be several hours of partly to mostly sunny skies in parts of the region. That should leader to temperatures running several degrees above modeled highs. 

Thank goodness. A nice, slow, reasonable melt the next few days can only help with whatever rain we get Thursday. 

[NEG NAO]

2 hours ago, MJO812 said:

Gfs is pretty stormy at the end of this month into January. If blocking develops then watch out.

There is a new thread created by Walt for next weeks potential

[SnoSki14]

1 hour ago, Brian5671 said:

that could suppress the storm track way south-like 09-10

Somehow I doubt that. 

I see the late Dec storm but it looks too warm right now. Climo is more favorable so can't rule out snows even to NYC though.

I think 1st week of Jan will offer better potential for this regions as pacific improves and blocking gets more established. 

I noticed the GEFS seemed to capture the Arctic blocking better than EPS in the long range. EPS has been playing catch-up these past few days.

[Eduardo]

4 hours ago, LibertyBell said:

there is no such thing as "el nino" or "la nina" patterns, it's all about blocking or lack thereof

I don't know if I'd go that far.  Certainly, blocking can overwhelm ENSO's influence and, in that respect, might be a greater determinant of sensible weather here (especially in the last few years of atmospheric coupling weirdness).  But that all doesn't mean there's "no such thing as 'el nino' or 'la nina' patterns[.]"

[White Gorilla]

27 minutes ago, Eduardo said:

I don't know if I'd go that far.  Certainly, blocking can overwhelm ENSO's influence and, in that respect, might be a greater determinant of sensible weather here (especially in the last few years of atmospheric coupling weirdness).  But that all doesn't mean there's "no such thing as 'el nino' or 'la nina' patterns[.]"

I think there are Nino and Nina correlations in temp and precip distribution as evidenced by analogue data, but specific patterns from one nino or nina year to the next are varied, depending on the phase of the ENSO cycle, strength and other factors. 

[snowman19]

5 hours ago, LibertyBell said:

there is no such thing as "el nino" or "la nina" patterns, it's all about blocking or lack thereof

To say that ENSO is totally meaningless and that there’s no such thing as El Niño or La Niña patterns is completely and totally absurd. That’s ludicrous 

[gmendevils8204]

2 hours ago, donsutherland1 said:

Some drier air has worked in, so there may be several hours of partly to mostly sunny skies in parts of the region. That should leader to temperatures running several degrees above modeled highs. 

Warmed up nicely.  46 in Little Falls right now.  There was a lot of melting today. 

[bluewave]

53 minutes ago, Eduardo said:

I don't know if I'd go that far.  Certainly, blocking can overwhelm ENSO's influence and, in that respect, might be a greater determinant of sensible weather here (especially in the last few years of atmospheric coupling weirdness).  But that all doesn't mean there's "no such thing as 'el nino' or 'la nina' patterns[.]"

Yeah, this month looks like a continuation of the atmospheric coupling weirdness of recent years. The 500 mb pattern is much more El Niño-like. Especially the deep Aleutian Low and +PNA. I guess that this makes up for the last 2 winters which were technically El Niño with La Niña-like 500 mb patterns. 
 

 

[SnoSki14]

1 hour ago, snowman19 said:

To say that ENSO is totally meaningless and that there’s no such thing as El Niño or La Niña patterns is completely and totally absurd. That’s ludicrous 

Is it though? There's something to be said about how decoupled the atmospheric pattern seems to be from the ENSO state. 

And then there's that whole Hadley Cell argument which is addressed well on the SNE forum. 

[snowman19]

1 hour ago, SnoSki14 said:

Is it though? There's something to be said about how decoupled the atmospheric pattern seems to be from the ENSO state. 

And then there's that whole Hadley Cell argument which is addressed well on the SNE forum. 

The argument that ENSO is completely meaningless and that there is no such thing as La Niña or El Niño patterns is asinine, nonsensical. It’s not even worthy of a debate 

[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