December 2020 General Discussions & Observations Thread

[snowman19]

1 hour ago, bluewave said:

The latest EPS weeklies are on the MJO progression east across the Maritime Continent train. First week of December temperatures averaging slightly above normal in the Northeast. Second week closer to normal. As others have mentioned, maybe we can put some snow points on the board during the second week. This is followed by our annual warm up approaching the solstice and through the holiday period.

 

 

 

 

It’s uncanny how closely we have been following 1988 up to this point.  I know several mets had mentioned it as an analog back in September.  If this is indeed how it plays out, ‘88 also had the +PNA spike the first 2 weeks of December then progressed into what the EPS weeklies show the 2nd half of the month 

[snowman19]

51 minutes ago, Allsnow said:

Yep. Niña look comes back week 4. Week 3 looks great with pna and -nao. 

A classic canonical La Niña response is bound to happen this winter. We have a strong Niña. Anytime there is a strong ENSO event, the pattern will eventually respond to the forcing, when there is a weak/moderate ENSO event, other atmospheric factors can “override” it all winter, as has been the case in the past, this event is too strong to not have a profound impact on the pattern

[qg_omega]

1 hour ago, bluewave said:

I only posted the temperature progression since it matches the the NYC pattern since 1980. Relatively flat early December temperatures followed by rapid warming mid to late month. The MJO moving east across the Maritime continent would also match the pattern. 

 

That seems heavily skewed to that 50 degree year

[NEG NAO]

5 hours ago, snowman19 said:

A classic canonical La Niña response is bound to happen this winter. We have a strong Niña. Anytime there is a strong ENSO event, the pattern will eventually respond to the forcing, when there is a weak/moderate ENSO event, other atmospheric factors can “override” it all winter, as has been the case in the past, this event is too strong to not have a profound impact on the pattern

Keep in mind that there is only one other winter since 1950 that a SL winter followed  a WE winter and that year is 2007 -08 and there have only been 7 SL's since 1950 thats only 10 % of the winters since 1950. A very small sample size which means making any assumptions about what might happen this year is very risky. Also keep in mind that 2010 - 2011 winter was a SL winter and NYC recorded 61 inches of snow that winter ...........

 

[BucksCO_PA]

5 hours ago, bluewave said:

Since the Boxing Day Blizzard in 2010, the 2nd week of December has been the snowiest of the month in NYC.

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

Ending Date	Total Snowfall Dec 1 to Dec 7	Missing Count
2019-12-07	1.6	0
2018-12-07	0.0	0
2017-12-07	0.0	0
2016-12-07	0.0	0
2015-12-07	0.0	0
2014-12-07	0.0	0
2013-12-07	T	0
2012-12-07	0.0	0
2011-12-07	0.0	0

 

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

Ending Date	Total Snowfall Dec 8 to Dec 14	Missing Count
2019-12-14	0.2	0
2018-12-14	T	0
2017-12-14	5.8	0
2016-12-14	0.4	0
2015-12-14	0.0	0
2014-12-14	1.0	0
2013-12-14	7.1	0
2012-12-14	0.0	0
2011-12-14	0.0	0

 

 

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

Ending Date	Total Snowfall Dec 15 to Dec 21	Missing Count
2019-12-21	0.7	0
2018-12-21	T	0
2017-12-21	1.2	0
2016-12-21	2.8	0
2015-12-21	0.0	0
2014-12-21	T	0
2013-12-21	1.5	0
2012-12-21	0.0	0
2011-12-21	0.0	0

 

 

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

Ending Date	Total Snowfall Dec 22 to Dec 31	Missing Count
2019-12-31	T	0
2018-12-31	T	0
2017-12-31	0.7	0
2016-12-31	T	0
2015-12-31	T	0
2014-12-31	0.0	0
2013-12-31	T	0
2012-12-31	0.4	0
2011-12-31	0.0	0

Earlier on another forum I put together the DEC daily snowfall climo for Philly. The focus was the unique 12/5 snowfall legacy but you can see using a recent trend back to 2000 the frequency of days with 1" or > snow is significantly higher during the beginning third of DEC as opposed to the middle & later part of the month.

Like NYC there hasn't been a late DEC day with an 1" of snow since Boxing Day 2010.

There's always DEC 5th for your early season hopes:

In terms of total snowfall 12/5 is the 3rd snowiest of any DEC day

12/5 is tied with 12/26 for the most # of 1"or > events during any DEC day

It is also tied with 12/26 for the 2nd most measurable snow events during DEC

Regarding recent trends over the past 20 yrs. 12/5 has recorded more 1" & total measurable snow events than any DEC day 

Philadelphia snowfall records date back to 1884

Expanding on recent trends there have been significantly more 1" snowfall events during the beginning of DEC since 2000.

8 - 12/1-12/10

4 - 12/11-12/20

3 - 12/21-12/31

 

[MJO812]

DT is going snowier and colder than the majority of the forecasts for the east.

[NEG NAO]

Storm potential next weekend 4th through 6th according to 0Z CMC - 850's cold enough BUT storm is too intense too close to coast and sst's too warm because its early in the season

[SnoSki14]

I wouldn't be quick to assume the 2nd half goes all warm for us. I'm not sure many had the current developments in their forecast. 

It's difficult to compare this year to 80s analogs given how much has changed over that time. 2nd week of December looks interesting for sure.

[wdrag]

First,  I want to thank all the posters insights on modeling from LR to climate stats.  Very helpful perspectives and I learn from this. Thank you!

On Dec 4-6: No topic since considerable uncertainty ranges from 00z-06z OP runs of major snowstorms from the the Missouri Valley to the northeast USA and/or all rain. And the 850MB  inflow is not as strong as that of this coming Monday, but broader and longer-which serves well for heavy precip event.  I root for the 06z GFS op... but... its D9-10, not in my window of confidence. GEFS RMOP has a positive tilt trough over the eastern USA with uncertainty, while it is categorically confident of the 500MB ridge axised n-s ~115W.

The one change in my thinking from previous days... a decent storm event is coming between Dec 4-6. What it is?  

[SnowGoose69]

1 hour ago, SnoSki14 said:

I wouldn't be quick to assume the 2nd half goes all warm for us. I'm not sure many had the current developments in their forecast. 

It's difficult to compare this year to 80s analogs given how much has changed over that time. 2nd week of December looks interesting for sure.

We are pretty much due for a winter where everyone forecasts wall to wall torch and it ends up like 93-94.  I don’t see much reason to assume that happens this year but it’s going to be hard to duplicate last winter.  This is sort of the opposite of going cold and snowy in 94-95 or 01-02 after the preceding winters sort of had a ton of things break in a favorable way.  It’ll be hard to get the ratter this winter we had last year again 

[NEG NAO]

1 hour ago, wdrag said:

First,  I want to thank all the posters insights on modeling from LR to climate stats.  Very helpful perspectives and I learn from this. Thank you!

On Dec 4-6: No topic since considerable uncertainty ranges from 00z-06z OP runs of major snowstorms from the the Missouri Valley to the northeast USA and/or all rain. And the 850MB  inflow is not as strong as that of this coming Monday, but broader and longer-which serves well for heavy precip event.  I root for the 06z GFS op... but... its D9-10, not in my window of confidence. GEFS RMOP has a positive tilt trough over the eastern USA with uncertainty, while it is categorically confident of the 500MB ridge axised n-s ~115W.

The one change in my thinking from previous days... a decent storm event is coming between Dec 4-6. What it is?  

Need to move this storm further east for most of the NYC metro to have any chance of a snow and or rain to snow scenario - at least with the 0Z Canadian which I posted earlier the storm was just off the coast and the 850's were below 32 but was still rain here - during the first week in December we need cold enough air already in place at all levels before the storm arrives and also a close to perfect storm track which keeps the onshore winds from developing because the water temps are still quite warm - (most of us know this already )the 06Z GFS op is good for central and western PA - like you said still 9-10 days out so the setup can change and the models have been all over the place so far with no definite solution.

[Allsnow]

On 11/25/2020 at 3:59 PM, snowman19 said:

If this is correct, then mid-late December turns mild. I believe December, 1988 (also a strong La Niña) had a +PNA run from 12/1 - 12/15 before it flipped. The late November strengthening period for this Niña has begun in earnest, the easterlies are really ripping right now and are projected to continue to do so well into December. Regions 3.4 and 4 are about to see another big SST drop from the upwelling. This is going to really limit how far MJO waves can propagate before they get sheared apart by the very strong easterlies and run into the colder waters....which is why MJO phases 3-6 are favored this winter

The Niña will not make it to strong status and it looks like we are near peak

[NEG NAO]

27 minutes ago, Allsnow said:

The Niña will not make it to strong status and it looks like we are near peak

Going to be very difficult to determine how much snowfall we might get this winter if the La Nina is moderate since there have been only 4 moderate  La Nina's since 1950. And 2 of them were complete opposites - 2011-12 with a total of 7.4 inches of snow at the park and 1995 -96 with the most snow on record with 75.6 inches. The other 2 are much different also 1955-56 had 33.5 and 1970-71 had 15.5. So in other words since a moderate La Nina hasn't happened very often its going to be difficult using it to try and determine total snowfall.....

[Allsnow]

29 minutes ago, NEG NAO said:

Going to be very difficult to determine how much snowfall we might get this winter if the La Nina is moderate since there have been only 4 moderate  La Nina's since 1950. And 2 of them were complete opposites - 2011-12 with a total of 7.4 inches of snow at the park and 1995 -96 with the most snow on record with 75.6 inches. The other 2 are much different also 1955-56 had 33.5 and 1970-71 had 15.5. So in other words since a moderate La Nina hasn't happened very often its going to be difficult using it to try and determine total snowfall.....

Nice post. Overall I’m more positive for this winter then I was a month ago. I don’t think 95/96 is walking into the door but 11/12 isn’t either 

[Allsnow]

 

[Allsnow]

 

[Allsnow]

Just now, Allsnow said:

 

 

[MJO812]

Latest Tellies

[NEG NAO]

This is extreme - this pattern will continue to deliver colder and colder air as we get into mid month if this is even right - 540 line all the way down into south FLA. Also an active storm track of both Miller A's and B's - chances are one of those SHOULD deliver for us IMO. 

[MJO812]

13 minutes ago, NEG NAO said:

This is extreme - this pattern will continue to deliver colder and colder air as we get into mid month if this is even right - 540 line all the way down into south FLA. Also an active storm track of both Miller A's and B's - chances are one of those SHOULD deliver for us IMO. 

Nice cold pattern on the gfs and cmc in the long range

[LongBeachSurfFreak]

2 hours ago, MJO812 said:

Nice cold pattern on the gfs and cmc in the long range

Fits a Niña look under normal circumstances. But what’s normal now? I’ll keep expectations low for now and hope for the best!

[CIK62]

Some BN T's YES----but accumulating snow NO.

All the Ensembles are basically barren.        GEFS leads the trio with a 20% chance of at least 2" in the next 15 days, or a 60% chance of seeing anything that can be measured.        The EURO and CMC Ensembles are just 20% to 30% of seeing anything.           I will keep checking to detect an improvement.

Dec. 10-12 could have our first sub-32 degree High T.

[qg_omega]

That first storm just verified a bit north but heck of a 174 hr forecast

[Allsnow]

26 minutes ago, CIK62 said:

Some BN T's YES----but accumulating snow NO.

All the Ensembles are basically barren.        GEFS leads the trio with a 20% chance of at least 2" in the next 15 days, or a 60% chance of seeing anything that can be measured.        The EURO and CMC Ensembles are just 20% to 30% of seeing anything.           I will keep checking to detect an improvement.

Dec. 10-12 could have our first sub-32 degree High T.

So you’re saying no snowfall for the entire month of December? 

[White Gorilla]

1 hour ago, CIK62 said:

Some BN T's YES----but accumulating snow NO.

All the Ensembles are basically barren.        GEFS leads the trio with a 20% chance of at least 2" in the next 15 days, or a 60% chance of seeing anything that can be measured.        The EURO and CMC Ensembles are just 20% to 30% of seeing anything.           I will keep checking to detect an improvement.

Dec. 10-12 could have our first sub-32 degree High T.

Would rather have low probs in the long term than high.  Case in point last year at this time as shown 

[TriPol]

7 hours ago, bluewave said:

This is the first late November in a few years without any virtual snow showing up in the models. 
 

 

 

 

Agh. I nearly had a heart attack looking at those pictures. Then I saw "2019." That was a bigger let down than March 2001.

[SnowGoose69]

The GFS pattern really looks 1980s like with the cold shots that keep ejecting south out of eastern Canada 

[MJO812]

7 hours ago, TriPol said:

Agh. I nearly had a heart attack looking at those pictures. Then I saw "2019." That was a bigger let down than March 2001.

No way

March 2001 was the worst

[MJO812]

51 minutes ago, SnowGoose69 said:

The GFS pattern really looks 1980s like with the cold shots that keep ejecting south out of eastern Canada 

Need snow

Cold without snow is useless

[SnoSki14]

1 hour ago, bluewave said:

The most impressive ridge during early December won’t be the +PNA. The models are indicating a +4.5 SD ridge to the east of New England. A 588 dm ridge in that area may be close to the early December record. This would be a continuation of the record ridges that we have been seeing out there recently. So early December should start like the last few winters  with the dominant  cutter and hugger storm tracks that pump the ridge in this location. Since the polar vortex is so strong, the wave breaks probably won’t be able to turn the NAO negative for longer than a brief period. By mid-December, both the EPS and GEPS retrograde that ridge back to New England. We have seen this retrogression numerous times in recent years. A very persistent pattern.

Best chance for snow will be during the retrogression or the Dec 6-13 period.