December 2020 General Discussions & Observations Thread

[MJO812]

Monday's  wave is more amplified so far on the gfs 

[NEG NAO]

40 minutes ago, MJO812 said:

Monday's  wave is more amplified so far on the gfs 

rain showers coast snow showers inland on this run

[MJO812]

7 minutes ago, NEG NAO said:

rain showers coast snow showers inland 

More amplified than 18z. Tellies still look good.

Maybe another threat?

Slim chance 

[Northof78]

Keep an eye on that one...interesting 

[donsutherland1]

In the wake of a snowstorm that brought widespread 10" or above amounts from New York City into New England with several areas of excessive amounts of 30" or more, tomorrow will be fair and unseasonably cold.

With the persistence of Arctic blocking, uncertainty about the closing days of December has increased. A possible piece of an Arctic air mass could even push into parts of the region on or just after December 25.

Historic experience following exceptionally warm November cases suggests that a warmer than normal December remains the base case. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park (2020 saw the temperature average a record 52.9° in November) went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above. The probability of December's having a 40.0° or above mean temperature has fallen sharply with the development of strong AO blocking.  

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 +34.10. That is the highest figure since March 17, 2018 when the SOI reached +35.90.

Today, the preliminary Arctic Oscillation (AO) figure was -2.620.

On December 16 the MJO was in Phase 5 at an amplitude of 0.839 (RMM). The December 15-adjusted amplitude was 0.880.

Based on the latest guidance, no significant stratospheric warming event is 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.

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 38.1°.

 

[weatherpruf]

3 hours ago, CPcantmeasuresnow said:

Someone may have already posted this but the 1:00pm update in Central Park was 10.5 inches for the storm.

 

The city now needs only  0.8 inches by the end of the month to reach a 30 inch average, when the new 30 year averages are calculated next month.

Amazing when it looked like that was a lock 2 and half years ago and it's coming right down to the wire.

 

I was watching a tv show recently filmed in Toronto, Orphan Black, and seeing the scenes of snow piles in the suburbs i decided to look up their average. It isn't as snowy as some might think; they average around 47 inches ( wrong side of the lake for lake effect ) and then looked up Detroit ( 33 inches ) and Chicago ( 35 inches ) and Boston ( 48 ). So really NYC at 28-30 is fairly snowy. But once you go south it starts dropping a lot. Boston is about on par with Toronto. Montreal however, averages around 83 inches, Quebec City 150...at that point its too cold a place for me; was there in July and stayed in a ski resort that functioned as a hotel in the summer; there was no AC. They told me don't worry open a window at night you'll be fine. They were correct.

[CPcantmeasuresnow]

44 minutes ago, weatherpruf said:

I was watching a tv show recently filmed in Toronto, Orphan Black, and seeing the scenes of snow piles in the suburbs i decided to look up their average. It isn't as snowy as some might think; they average around 47 inches ( wrong side of the lake for lake effect ) and then looked up Detroit ( 33 inches ) and Chicago ( 35 inches ) and Boston ( 48 ). So really NYC at 28-30 is fairly snowy. But once you go south it starts dropping a lot. Boston is about on par with Toronto. Montreal however, averages around 83 inches, Quebec City 150...at that point its too cold a place for me; was there in July and stayed in a ski resort that functioned as a hotel in the summer; there was no AC. They told me don't worry open a window at night you'll be fine. They were correct.

I lived in Madison Wisconsin for several years and people never believe me when I tell them it snows a lot more here in the Hudson Valley then it does there. It's colder there, but cold and dry. A big storm to them is 6-8 inches, but of course it does stay on the ground longer than places in and close to NYC.

Big storms are a rarity in the Midwest, the perfect example is Minneapolis. They have been keeping weather records almost as long as NYC, since the 1880's. They average about  50 inches of snow per season, similar to Toronto, but In that time they have had 5 storms with more than 17 inches of snow, New York City has had 16 storms over 17 inches in the same time span.

I wish I could remember the exact length of time because I heard it in the last year, but the gap for 10 inch snowfalls in Toronto is incredibly long right now. I forget how many years but maybe Bluewave, Don, Uncle W or someone of that ilk knows.

[weatherpruf]

21 minutes ago, CPcantmeasuresnow said:

I lived in Madison Wisconsin for several years and people never believe me when I tell them it snows a lot more here in the Hudson Valley then it does there. It's colder there, but cold and dry. A big storm to them is 6-8 inches, but of course it does stay on the ground longer than places in and close to NYC.

Big storms are a rarity in the Midwest, the perfect example is Minneapolis. They have been keeping weather records almost as long as NYC, since the 1880's. They average about  50 inches of snow per season, similar to Toronto, but In that time they have had 5 storms with more than 17 inches of snow, New York City has had 16 storms over 17 inches in the same time span.

I wish I could remember the exact length of time because I heard it in the last year, but the gap for 10 inch snowfalls in Toronto is incredibly long right now. I forget how many years but maybe Bluewave, Don, Uncle W or someone of that ilk knows.

I actually read something to that effect about Toronto as well, that they were behind Chicago or something in that regard. So again, it's not really a snow mecca.  A little more on average than NYC ( 17 inches more ) due more to its being colder with smaller events that are typically rain or mix messes here. Montreal is in its own class for a big city. 

[wdrag]

Good Friday morning everyone,  I hope this is a snow satiated group this morning.  I think more snow is coming for NYC this December. 

I posted event options for the I84 area in our nw - ne suburbs thread. I am thinking of a storm thread for Christmas eve-Christmas morning- but think it best to wait until all the 12z/18 guidance (ensembles too) is in.  Even the 21st looks interesting to me for NYC/CT.  

The thread for the 24th-25th would be along the model lines you see now. Big snowmelt (virtually all melted se of I84) by rain and a brief southerly flow warmup. Damaging wind potential e Li (already ~40% prob of 50 MPH gusts from the 00z/18 GEFS), then cap it off with a 1-4" backside CAA snow the morning of the 25th.  These backside snows are not easy to attain and uncommon (long shot in the coastal plain). Temperatures will dictate remaining snowmelt on the 24th, but if it's rapid and we get 1" of rainfall on top of the 1" snowmelt water equivalent in 12 hours, we might have minor flood problem??  Again, a long shot per current guidance with so many variables to consider.

The main thing, we continue in a highly amplified pattern with 'overall' near normal temps the rest of the month. Have a good day. 

[CIK62]

The next 8 days are averaging 31degs.(24/38).      Making it 26degs., or -10degs.

Month to date is missing.     Calculated to date is +1.4.      Should be -2.3 by the 26th.

27*(69%RH) here at 6am, partial thin overcast.     31* by Noon.        32* by 12:30pm.

Oddly enough, only Christmas and New Years Day look warm over the next 15 days. 

GEFS T's look OK till the 5-Day period centered on Jan. 10th.       CFS hopefully takes over for Feb./Mar. with the super cold it is showing.     SD thinks if the La Nina kicks the bucket more rapidly, this could happen.

[donsutherland1]

Morning thoughts...

Today will become partly to mostly sunny in much of the region. It will remain unseasonably cold. Temperatures will likely top out in the lower and middle 30s across most of the region. Likely high temperatures around the region include:

New York City (Central Park): 33°

Newark: 34°

Philadelphia: 36°

Temperatures will moderate during the weekend.

[bluewave]

Record warmth to some type of snowfall record is becoming more frequent in recent years. 
 

November 2020 was the warmest on record in NYC at 53.0°...5th earliest seasonal 10.0”+ snowfall of 10.5” in December

January to March  2020 was the 2nd warmest on record in NYC at 42.4°...trace of snow on May 9th tied with 1977 for latest on record after 7th coldest winter at 28.3°

February 2018 was the warmest on record around the area with a first 80° at Newark .....NYC warmest February at 42.0°....ISP snowiest March at 31.9” of snow

December 2015 was warmest on record with a +13.3...50.3° in December....greatest snowstorm on record in NYC during January of 27.5”

January 2006 was the 4th warmest in NYC at 40.9° followed by the 2nd biggest snowstorm in February of 26.9”

 

 

[NEG NAO]

1 hour ago, wdrag said:

Good Friday morning everyone,  I hope this is a snow satiated group this morning.  I think more snow is coming for NYC this December. 

I posted event options for the I84 area in our nw - ne suburbs thread. I am thinking of a storm thread for Christmas eve-Christmas morning- but think it best to wait until all the 12z/18 guidance (ensembles too) is in.  Even the 21st looks interesting to me for NYC/CT.  

The thread for the 24th-25th would be along the model lines you see now. Big snowmelt (virtually all melted se of I84) by rain and a brief southerly flow warmup. Damaging wind potential e Li (already ~40% prob of 50 MPH gusts from the 00z/18 GEFS), then cap it off with a 1-4" backside CAA snow the morning of the 25th.  These backside snows are not easy to attain and uncommon (long shot in the coastal plain). Temperatures will dictate remaining snowmelt on the 24th, but if it's rapid and we get 1" of rainfall on top of the 1" snowmelt water equivalent in 12 hours, we might have minor flood problem??  Again, a long shot per current guidance with so many variables to consider.

The main thing, we continue in a highly amplified pattern with 'overall' near normal temps the rest of the month. Have a good day. 

The 6Z GFS looks very interesting for next Friday as a wave is developing along the front on next Thursday and then rides up along the front through Friday - this is all about timing IMO and the exact location of the front and cold enough air as the wave rides up along the front - according to this it is a complex situation still a week away it is beginning to remind me of Christmas 2002 when rain developed earlier and then changed to snow across the region as the day wore on and by night several inches were on the ground

[bluewave]

The storm around Christmas may turn into another wave breaker event like near the start of December. Notice the extreme block the models are moving to following the storm east of Newfoundland. That is very similar to what happened back in early December. This early December block east of the Maritimes came before the blocking built into the Arctic like we just saw. So maybe the Christmas storm will set the table for another -AO drop into January followed by the next major snowstorm potential.

 

[wdrag]

Posts on p38 (This one)  are helpful for me and it is an interesting time. Not to go against anyone,  but I'm thinking we are tending to expand the database with more extreme weather the past couple of decades here in our forum. I might be wrong on this and will listen to counter science.  This could be related to the warming (cycle) planet.  

Have appended several graphics to ensure everyone has seen this and has an idea in advance what is ahead (flooding? but if we're lucky, some spring snowmelt for the reservoirs in April).  Also, there is anecdotal evidence (unsure of the science research on this) that the southern edge of the snowpack tends to set up the warm fronts and future low pressure development (easier in warmer air with northward advance of warm fronts often slowed by the colder denser surface air associated with snow cover).  

Didn't add snow density because I don't understand  the numbers and how they relate to  impacts but I think it may have to do with difficulty passing through (walk, transportation)and/or removal. If there is a link--- please add on. Thank you. 

[LibertyBell]

2 hours ago, bluewave said:

Record warmth to some type of snowfall record is becoming more frequent in recent years. 
 

November 2020 was the warmest on record in NYC at 53.0°...5th earliest seasonal 10.0”+ snowfall of 10.5” in December

January to March  2020 was the 2nd warmest on record in NYC at 42.4°...trace of snow on May 9th tied with 1977 for latest on record after 7th coldest winter at 28.3°

February 2018 was the warmest on record around the area with a first 80° at Newark .....NYC warmest February at 42.0°....ISP snowiest March at 31.9” of snow

December 2015 was warmest on record with a +13.3...50.3° in December....greatest snowstorm on record in NYC during January of 27.5”

January 2006 was the 4th warmest in NYC at 40.9° followed by the 2nd biggest snowstorm in February of 26.9”

 

 

Not to mention that 2020 has a chance to be the warmest year on record globally.

By the way, now you're going to be hardpressed to find anyone who doesn't agree that a snowless October-November is good for December snows (and perhaps winter as a whole), you and I have been discussing a possible mechanism for this and a reason why this may be and I tend to agree with your theory that the pattern needs some time to "recover and reload" after a wintry event so perhaps a late October or November event portends badly for December and perhaps for winter as a whole because of this.  Remember it took us until mid February to recover enough from A11072012 to get to  N02082013 on the east coast.

https://en.wikipedia.org/wiki/November_2012_nor'easter

A mid-level shortwave over the Midwestern United States was moving eastward on November 6, just four days after Hurricane Sandy dissipated, toward a trough over the Southeastern United States, and into an area with abundant moisture and favorable conditions from the jet stream. The combination was favorable for a nor'easter to form,^[3] and on November 7, a strong low pressure area developed along the coast of North Carolina.^[4] At the time, there was an area of cold air inland the Mid-Atlantic States and New England that would allow the precipitation to fall as snow.^[5] By November 8, the system drifting to the northeast, located about 90 mi (140 km) south-southeast of Boston, Massachusetts, with a front extending northeastward to Nova Scotia. Its large circulation dropped rain and snow across the northeastern United States.^[6] Some areas within NYC, got close to a foot of snow across Western Long Island, including Eastern Queens County in a narrow snow band that set up because of the coastal front.

https://en.wikipedia.org/wiki/Early_February_2013_North_American_blizzard

The Early February 2013 North American blizzard was a powerful blizzard that developed from the combination of two areas of low pressure,^[5] primarily affecting the Northeastern United States and parts of Canada, causing heavy snowfall and hurricane-force winds. The storm crossed the Atlantic Ocean, affecting Ireland and the United Kingdom.^[6] The nor'easter's effects in the United States received a Category 3 rank on the Northeast Snowfall Impact Scale, classifying it as a "Major" Winter Storm.

[LibertyBell]

21 hours ago, Brian5671 said:

Was crazy up here too in Jan 94 -there was one, not sure which but it jumped into the 40's briefly then flash froze down to 0.   Roads were a mess for days

in Jan 94 we had two arctic outbreaks that went to 0 or below, I remember there was one where we went from 0 for the low to 32 for the high at the next midnight and then a 55 high the next day as a screaming sou'easter blew through.....

 

[LibertyBell]

13 hours ago, CPcantmeasuresnow said:

I lived in Madison Wisconsin for several years and people never believe me when I tell them it snows a lot more here in the Hudson Valley then it does there. It's colder there, but cold and dry. A big storm to them is 6-8 inches, but of course it does stay on the ground longer than places in and close to NYC.

Big storms are a rarity in the Midwest, the perfect example is Minneapolis. They have been keeping weather records almost as long as NYC, since the 1880's. They average about  50 inches of snow per season, similar to Toronto, but In that time they have had 5 storms with more than 17 inches of snow, New York City has had 16 storms over 17 inches in the same time span.

I wish I could remember the exact length of time because I heard it in the last year, but the gap for 10 inch snowfalls in Toronto is incredibly long right now. I forget how many years but maybe Bluewave, Don, Uncle W or someone of that ilk knows.

are they experiencing a snow drought in Toronto like Seattle has been?

[CPcantmeasuresnow]

7 minutes ago, LibertyBell said:

are they experiencing a snow drought in Toronto like Seattle has been?

I'm not sure, but Toronto averages 47 inches of snow a season and Seattle averages about 5 inches a season. I'm assuming long periods between 10 inch snowfalls in Seattle are pretty common.

[SACRUS]

I have been watching the Christmas eve warmth to artctic front rain, temps crash to heavy snow for a period on Christmas early morning threat and believe it is time to track.  Could be a wild swing.  60 on the eve and lows in the teens Christmas and boxing day, possible

[SACRUS]

ECM has 850 temps peaking of >9c on a southerly flow Christmas eve then -10C by Christmas late evening.

 

http://img.meteocentre.com/models/ecmwf_amer_qc_00/TT_UU_VV_168_0850.gif

http://img.meteocentre.com/models/ecmwf_amer_qc_00/TT_UU_VV_192_0850.gif

 

[CPcantmeasuresnow]

3 minutes ago, SACRUS said:

ECM has 850 temps peaking of >9c on a southerly flow Christmas eve then -10C by Christmas late evening.

 

http://img.meteocentre.com/models/ecmwf_amer_qc_00/TT_UU_VV_168_0850.gif

http://img.meteocentre.com/models/ecmwf_amer_qc_00/TT_UU_VV_192_0850.gif

 

That could really kill a lot, it not all of the snowpack on Christmas Eve. Boy would that suck.

[Brian5671]

1 minute ago, CPcantmeasuresnow said:

That could really kill a lot, it not all of the snowpack on Christmas Eve. Boy would that suck.

it might  be down to  not much by then anyway if it's sunny and in the 30's to near 40 early next week....

[CPcantmeasuresnow]

16 minutes ago, Brian5671 said:

it might  be down to  not much by then anyway if it's sunny and in the 30's to near 40 early next week....

This time of year I find 30's have very little impact on snow pack, even when sunny. Add to it that the current snow pack wich is 12 inches here, Orange County, has a LE of 1.5 inches. The late December sun, even in the 30's will do very little damage to that. It's a different story of course in urban areas with all of the blacktop, higher daytime highs, traffic etc.

However rain and high 40's to low 50's on strong southerly winds, that would be a snow killer on Christmas Eve if it happens as currently depicted.

[Allsnow]

3 hours ago, CIK62 said:

The next 8 days are averaging 31degs.(24/38).      Making it 26degs., or -10degs.

Month to date is missing.     Calculated to date is +1.4.      Should be -2.3 by the 26th.

27*(69%RH) here at 6am.

Oddly enough, only Christmas and New Years Day look warm over the next 15 days. 

GEFS T's look OK till the 5-Day period centered on Jan. 10th.       CFS hopefully takes over for Feb./Mar. with the super cold it is showing.     SD thinks if the La Nina kicks the bucket more rapidly, this could happen.

Do you remember all the post you made about 10 inches of snow in nyc yesterday

[NorthShoreWx]

The Grinch usually isn't denied, but this snowcover won't dissapear from a few 40 degree days in December sun.

Our 6.7 inches of snow here (now 6" snowdepth) contains 1.61" of water.  I melted the catch in the rain gage and it was only 0.64" so I took a core which melted to 1.61".

 

 

[Brian5671]

2 minutes ago, NorthShoreWx said:

The Grinch usually isn't denied, but this snowcover won't dissapear from a few 40 degree days in December sun.

Our 6.7 inches of snow here (now 6" snowdepth) contains 1.61" of water.  I melted the catch in the rain gage and it was only 0.64" so I took a core which melted to 1.61".

 

 

won't disappear but a dent will be put into it...especially in areas that are urbanized etc...

[uncle W]

4 minutes ago, NorthShoreWx said:

The Grinch usually isn't denied, but this snowcover won't dissapear from a few 40 degree days in December sun.

Our 6.7 inches of snow here (now 6" snowdepth) contains 1.61" of water.  I melted the catch in the rain gage and it was only 0.64" so I took a core which melted to 1.61".

 

 

I did that for the blizzard of 96...my core sample was like 9 to 1 and the catch was 11 to 1 ratio...

[uncle W]

December 1955, 1964,  1979 and 2008 had snowfalls within a week of Christmas but melted Christmas eve in a torch...

[SnoSki14]

41 minutes ago, SACRUS said:

I have been watching the Christmas eve warmth to artctic front rain, temps crash to heavy snow for a period on Christmas early morning threat and believe it is time to track.  Could be a wild swing.  60 on the eve and lows in the teens Christmas and boxing day, possible

Let's hope so that'd be a blast. Very strong wind gusts too, gfs shows legit HWW conditions. 

Fingers crossed for a flash freeze event Xmas eve