December 2020 General Discussions & Observations Thread

[SnoSki14]

32 minutes ago, snowman19 said:

No, if there’s really a full latitude trough out west it’s not “correcting” to anything 

I don't see any full latitude trough on the ensembles.

[HeadInTheClouds]

2 hours ago, CIK62 said:

GFS contains enough liquid for 55" inches of snow over the next 16 days-------but alas shows just a paltry 3".       Looks like a Cutter City Festival.

Yeah and we know how good the GFS has been. 

[White Gorilla]

48 minutes ago, JoshSnow said:

GFS looks pretty cold. It looks like heavy rain would change to heavy snow just around midnight Christmas Eve which sounds pretty special!

Old GFS or new one? 

[NorthShoreWx]

Weather Service doesn't seem to be hitting the idea very hard, but this is a textbook black ice scenario on the north shore right now.  0.4" snowfall today, current temp is 31 and its vaguely foggy.  Or is that foggily vague.  No, the first one.  Its icy out there.

[Neblizzard]

20 minutes ago, HeadInTheClouds said:

Yeah and we know how good the GFS has been. 

Exactly.  Why would anyone trust models 7-10 days out? 

[Wentzadelphia]

11 minutes ago, Neblizzard said:

Exactly.  Why would anyone trust models 7-10 days out? 

I don’t think anyone trusts them. This is the hobby. We track future storms. We root on the most destructive and intense solution, and on the side we root on post frontal snow showers haha. Anyone who has been in this hobby long enough knows the gfs has too much qpf in cold sector with fronts like this. It’s always too cold, but it’s fun. What’s the big deal? 

[NEG NAO]

1 hour ago, JoshSnow said:

GFS looks pretty cold. It looks like heavy rain would change to heavy snow just around midnight Christmas Eve which sounds pretty special!

GFS is out to lunch IMO - look what it just cooked up for a few days later:

[HeadInTheClouds]

Just now, NEG NAO said:

GFS is out to lunch IMO - look what it just cooked up for a few days later:

It's a POS model. Look what it did with the previous storm. 

[Allsnow]

6 hours ago, snowman19 said:

This progression is not shocking at all in a La Niña which is front end loaded. December through early to mid January typically are the colder/snowier period, then late January, February (especially) and March are when the classic La Niña torch pattern normally hits

Agree. But having this much blocking is not normal. We have not had the typical December Niña pattern. This has been acting more like a nino then a Niña. Where is the southeast ridge and cold in the upper Midwest? 

[NEG NAO]

Just now, Allsnow said:

Agree. But having this much blocking is not normal. We have not had the typical December Niña pattern. This has been acting more like a nino then a Niña. Where is the southeast ridge and cold in the upper Midwest? 

hopefully gone for the rest of the winter.........

[MJO812]

12 minutes ago, Allsnow said:

Agree. But having this much blocking is not normal. We have not had the typical December Niña pattern. This has been acting more like a nino then a Niña. Where is the southeast ridge and cold in the upper Midwest? 

Same thing happened in 2010-2011

Alot of blocking until February

 

[donsutherland1]

Tomorrow will be partly to mostly cloudy. A period of light snow or flurries is possible tomorrow night into Tuesday morning.

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

The likely continuation of Arctic blocking 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 -0.1°C and the Region 3.4 anomaly was -1.2°C for the week centered around December 9. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.62°C and the ENSO Region 3.4 anomaly has averaged -1.43°C. La Niña conditions will likely prevail at least through the winter.

The SOI was +10.02 today.

Today, the preliminary Arctic Oscillation (AO) figure was -1.001.

On December 19 the MJO was in Phase 5 at an amplitude of 1.031 (RMM). The December 18-adjusted amplitude was 0.864.

Based on the latest guidance, no significant stratospheric warming event is likely into the final week of December.

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 55% probability that New York City will have a warmer than normal December. December will likely finish with a mean temperature near 37.9°.

 

[NorthShoreWx]

30.9 with freezing fog here.  There's nothing vague about the fog anymore.  Visibility  is 1/4 mile or less but you can still make out the waxing crescent moon through the fog.  It is surreal out there.  Great night for a walk if you have traction aids for your feet and don't mind getting run over by a skidding car.

Be careful if driving.  

[BucksCO_PA]

This past WED-THURS (6.6") was the 25th 6" or > snow event on record at Philadelphia prior to JAN. On 16 occasions following the prior 24 events another 6" or > snowfall event was observed later that season. Since the NOV 1953 event the more recent trend is 10 out of the past 11 which includes a run of multiple follow-up events since 2002. 

Philadelphia has never recorded more than one 6" or > snow event in the same season prior to JAN. Philadelphia snowfall records date back to 1884.

Digger a little deeper here are the subsequent snowfall totals for the 24 seasons with the 6" or > snow event. Observed mean is 22.6" vs. the 18.1" long term period of record JAN-APR average.

[LibertyBell]

4 hours ago, NorthShoreWx said:

30.9 with freezing fog here.  There's nothing vague about the fog anymore.  Visibility  is 1/4 mile or less but you can still make out the waxing crescent moon through the fog.  It is surreal out there.  Great night for a walk if you have traction aids for your feet and don't mind getting run over by a skidding car.

Be careful if driving.  

did you see the super conjunction yet?  It peaks tomorrow night, I wonder how the sky condition will be then?

with all the technological innovations we've made, meteorology always lags behind....I still can't believe we haven't learned how to suck the clouds right out of the sky so we can see amazing celestial phenomena like this!

 

[LibertyBell]

5 hours ago, Allsnow said:

Agree. But having this much blocking is not normal. We have not had the typical December Niña pattern. This has been acting more like a nino then a Niña. Where is the southeast ridge and cold in the upper Midwest? 

I dont believe enso influences our weather as much as people think (or used to think), there are other factors that usurp it, like blocking, we probably shouldn't be concentrating on enso so much.

 

[LibertyBell]

11 hours ago, snowman19 said:

This progression is not shocking at all in a La Niña which is front end loaded. December through early to mid January typically are the colder/snowier period, then late January, February (especially) and March are when the classic La Niña torch pattern normally hits

we've had March be very snowy in this kind of ENSO....maybe we shouldnt be concentrating so much on ENSO, there are other factors which can be more important

 

[LibertyBell]

10 hours ago, CPcantmeasuresnow said:

It’s as ridiculous to use the 70s and 80s as examples as it is to use just the the last 20 years. The 70s and the 80s were the worst decades for snowfall in the city, both averaged 20-21 inches, in the 150 years of recordkeeping.

Maybe try the 152 year average in NYC which is 28.8 inches, or you can go with the 30 year average which NOAA calculates for every city and in New York City that average is 30.0 inches. Not much of a difference either way. 

snow measurement is the least scientific part of meteorology- look how much measurement methods have changed over the years and all these claims of undermeasuring, etc.  There are many specific storms that can be pointed to for undermeasurement of snow here, and even one of them would have brought us over the 30 inch average.

Exhibit A should be January 1996......

 

[LibertyBell]

8 hours ago, Isotherm said:

 

Additionally (supplement to your good points here) regarding the United States "average" snowfall, left unsaid is whether that average is derived via a population weighted calculation. The raw average may be somewhat deceptive. A comparison of moderately-highly populated cities rather than an incorporation of all towns in the entire United States would likely yield NYC well above the 50th percentile. 

Locally, I've calculated a 31.0" average snowfall for 1990-2020. It's been an excellent 20 year period in interior Monmouth County. Like portions of central LI, here, we tend to benefit from late developing Miller Bs, further mesoscale enhancement from the Sandy Hook Bay on NELY flow during winter storms, and proximity to the Atlantic Ocean, but not close enough to materially lower the snowfall average. Hence Monmouth County features a fairly interesting climate, and frequently steep snowfall gradient NW-SE/NNW/SSE in numerous storms. There's about a 9-10" differential in average snowfall across the county; 30-31" in the N/W and close to 20-21" in Manasquan. (My website here: https://www.lightinthestorm.com/nj-snowfall ).

Newark Airport also has a 31.1" 30-year running average 1990-2020 per latest data. My median 30-year snowfall is 29.0", which is not far from the mean, and it suggests the frequency of above and below normal snowfall winters aren't too dissimilar. Contrast to locations farther south (for example, DCA) wherein snowfall medians are quite a bit lower than means.

Also, possibly axiomatic, but the average for a given place is deceptive in how that average arrives. Most of the Mid-west outside of the Lakes region derives those 25-35" averages via frequently low end snowfall events (as you know). I think the region 39N-41N on the eastern side of North America has some of the most significant and fascinating variability in winter-time weather.

 

You also dont undermeasure like NYC has done in our biggest and smallest storms....31 or 32 may be closer to the true average.

 

[LibertyBell]

7 hours ago, bluewave said:

Yeah, having a much warmer than average NW Atlantic nearby makes a big difference. ISP has had 5 events of 17” or greater since the 09-10 winter. MSP recorded  one 17” snowstorm over the same period.

for ISLIP-LI MACARTHUR AP, NY

27.8	2013-02-09

24.9	2015-01-27

23.9	2009-12-20

23.7	2016-01-24

18.4	2018-03-22

for Minneapolis-St Paul Area, MN (ThreadEx)

17.3	2010-12-11

 

 

see there are some benefits to climate change

 

[LibertyBell]

11 hours ago, weatherpruf said:

Snow has always been a source of uplift for peoples' moods during winter. The most depressing thing in winter are short, overcast rainy days that come back to back. That is in fact how  winters are in many places where snow isn't common; England, Ireland a lot of the US....snow lifts people's moods because it brightens things up. Using the snow blower and having the dog leap into the air chasing the snow was the most fun I've had in a long time. It's back to overcast and damp today ( though it did snow a bit earlier ).

I think part of the reason is snow's albedo.  It reflects back what little light we get and lessens the effects of SAD.

It literally brightens things up!

[LibertyBell]

15 hours ago, bluewave said:

The Christmas storm wave break looks like it may be off the charts. The ridge just south of Greenland goes more than +5 SD. This could be one the strongest blocks in that region for this time of year. So we will be probably be looking at winter storm threats from the end of December right into January.
 

 

I have a strong feeling that you believe the coast will have to wait for January for the pattern to benefit us.

 

[LibertyBell]

13 hours ago, SnoSki14 said:

MJO will be moving towards favorable 8-2 phases as well though near the circle. 

I'd be shocked if we didn't see another major snowstorm by Jan 10. 

I think it will happen between Jan 5-10 with not much before then

 

[wdrag]

I am considering a new topic to post around 730AM this morning for a moderate or greater rain changing to snowstorm event for the I84 region, possibly down to the immediate NYC north and west suburbs for next Monday-Tuesday-Wednesday 28-29-30 (special emphasis Tue-29th).  I need more time to think it through. DT from yesterday or before and BlueWave and others in the previous several days have highlighted the potential.  I think it's on the more defined modeling board now for general awareness (EC first op, I think but please correct me if I'm wrong). Need to frame it reasonably, leaving options open because of thermal profiles/tracking. 

[snowman19]

9 hours ago, MJO812 said:

Same thing happened in 2010-2011

Alot of blocking until February

 

Yea, we may be singing a very different tune in just over 4 weeks (late January) 

[CIK62]

The next 8 days are averaging 35degs.(29/41).          Making it 30degs., or -4.0.

Month to date is  39.0[-0.1].         Should be about 36.5[-1.1] by the 29th.

Models are all rain for their durations,  except for a Trace of snow on the CMC(29th).     A parade of close calls.

GEFS Extended has brought back the Jan.6-7 15"er, after dropping it for a day.

40*(85%RH) here at 6am.    Low was 38* at 2am.         44* by Noon.       45* by 1pm.        47* by 3pm.

[jfklganyc]

Solid 33F all night long.

Lots of dripping outside.

[bluewave]

The timing of the Christmas cold front looks to be early Christmas morning. The EURO and new GFS V16 are pretty close. So the high for the day will be early with falling temperatures after. Another big temperature swing weather pattern.

 

[wdrag]

I've run of time with family considerations the priority.  I'll be back by 1030 and start a new snowstorm topic at that time.  As note by others...  The exceedingly strong block is favorable for to 1 to possibly events between the 28th-at least Jan 5.  Take what we get and enjoy.

 

I am considering a new topic to post this morning for a moderate or greater rain changing to snowstorm event for the I84 region, possibly down to the immediate NYC north and west suburbs for next Monday-Tuesday-Wednesday 28-29-30 (special emphasis Tue-29th).  I need more time to think it through. DT from yesterday or before and BlueWave and others in the previous several days have highlighted the potential.  I think it's on the more defined modeling board now for general awareness (EC first op, I think but please correct me if I'm wrong). Need to frame it reasonably, leaving options open because of thermal profiles/tracking. 

[donsutherland1]

Morning thoughts...

Today will be variably cloudy. Temperatures will likely top out in the upper 30s and lower 40s across most of the region. Likely high temperatures around the region include:

New York City (Central Park): 41°

Newark: 41°

Philadelphia: 43°

After some overnight rain or snow showers, tomorrow will become partly cloudy.