December 2020 General Discussions & Observations Thread

[psv88]

1 hour ago, gravitylover said:

I've had off and on flurries all morning but over in the Catskills it's more significant https://www.plattekill.com/webcams/  

Pretty bad for December

[bluewave]

I guess model mayhem is the end result when the pattern tries to shift from more Niño-like to more Niña-like in the same month. 
 

 

 

[leo2000]

13 minutes ago, bluewave said:

I guess model mayhem is the end result when the pattern tries to shift from more Niño-like to more Niña-like in the same month. 
 

 

 

Maybe or could have been because of the Polar Vortex taking hits and being stretched. 

MAJOR trend from 49% to 70% of the 103 global ensembles in 12 hrs for a -AO from 12-13-20 and beyond.

Colder risks mid month drastically increasing. 

Details in my video coming in http://Bamwx.com video here soon. 

#natgas #oott #energy

 

 

[bluewave]

1 hour ago, leo2000 said:

Maybe or could have been because of the Polar Vortex taking hits and being stretched. 

MAJOR trend from 49% to 70% of the 103 global ensembles in 12 hrs for a -AO from 12-13-20 and beyond.

Colder risks mid month drastically increasing. 

Details in my video coming in http://Bamwx.com video here soon. 

#natgas #oott #energy

 

 

 

A different day and another set of solutions.

 

[gravitylover]

2 hours ago, psv88 said:

Pretty bad for December

Well yeah, there is that. Gotta start somewhere I guess.

[Allsnow]

2 hours ago, FPizz said:

Pretty crazy differences.  Something is going to be off big time.  

 

2 hours ago, Brian5671 said:

Go with warmth, you'll rarely be wrong these days....

 

2 hours ago, Stormlover74 said:

Will probably end up somewhere in between 40s/50s and boring. Though 50s is pretty torchy in mid December 

As the pac reshuffles we are probably going to warm next weekend. The eps went towards the gefs today with dumping energy into the west. It doesn’t break off a piece into the trough in the east. 
 

IMO the 11th into the 20th will be our best shot for snow. We will get a cold dump into the east because of the wave 1 hit on the strat. We will loose the Aleutian low so this will allow lower hgts into Canada. 

[DTWXRISK]

 

[Allsnow]

Some really nice tweets from Simon Lee today about the vortex. The second half of December will be the key to how the rest of winter ends up. In 2019 we had some Weakening of the vortex (cold November and early December) then it went crazy at the end of the month. This was basically the nail in the coffin last winter. It’s very important not to see it gain strength at the end of December. 
 

 

 

[DTWXRISK]

simon   lee   ...good   met

[Allsnow]

2 minutes ago, DTWXRISK said:

simon   lee   ...good   met

I hope all is well @DT_WXRISK. Great to hear from you. 

[bluewave]

On 12/2/2020 at 9:50 AM, LibertyBell said:

It reminds me of summer lol.

How much do the high temps in the Atlantic have to do with this, Chris?

 

The ridge verifying stronger to our south and east than longer range model guidance has been our new normal in recent years.  There have been so many week 2 forecasts that suddenly correct stronger within the day 7-10 range. It would be nice if we had bias corrected model maps to deal with this. Maybe this will be the next step in long range model forecasting. The exception to the rule is strong -AO and -NAO blocking.

 

https://www.ecmwf.int/en/about/media-centre/science-blog/2019/will-machine-learning-replace-conventional-weather

How could machine learning be used in numerical weather prediction?

There are a large number of possible application areas for machine learning throughout the workflow of numerical weather prediction. Here, the “system” could be a tool to pick and bias-correct observations that are used within data assimilation; a tool to project real-world observations into a representation of variables as they are used within models; or a part of the numerical forecast model – such as the radiation scheme which predicts the heating of the atmosphere given surface temperature, cloud patterns and incoming radiation from the sun. It could also be a tool that is used in post-processing of the output of a weather forecast model, for example to detect extreme weather events in forecasts or to bias-correct forecasts for a specific location.

 

 

[Allsnow]

 

[Allsnow]

Keeping the vortex weak is important because it allows us a mechanism to get cold without the help of the mjo. If the mjo (which I expect this winter) remains in unfavorable phases it is very important the vortex stay weak. Last winter strong mjo and vortex was a death sentence.  
 

Im not referring to a SSW, just a weak enough vortex for strat hits. 

[donsutherland1]

A sustained period of cooler than normal to near normal temperatures is poised to develop. Initially readings will run somewhat above normal, but the colder regime could move into place near or during the coming weekend following a storm that could bring significant precipitation to the region. The storm could end as snow north and west of New York City and Newark. The 12z ECMWF was even more aggressive in pushing the snow into both cities.

A fairly sharp cold shot is possible during the second week of December. There remains considerable uncertainty about the timing of the next change toward milder conditions. The development of a AO-/PNA+ pattern has shifted the outlook toward colder temperatures during the first half of December (consistent with statistical guidance). Exceptional cold is unlikely through mid-December. The duration of the AO-/PNA+ pattern will be key to how long the colder pattern persists.

Meanwhile, an extended duration much warmer than normal regime has now developed in western Canada. Record high temperatures included:

Dawson, Yukon Territory: 35° (old record: 25°, 1978)
Faro, Yukon Territory: 47° (old record: 44°, 1997)
Juneau: 52° (old record: 51°, 1929)
Seattle: 60° (tied record set in 1939)
Teslin, Yukon Territory: 44° (old record: 41°, 1963)
Watson Lake, Yukon Territory: 45° (old record: 39°, 1963 and 2004)

Tomorrow through Friday could see additional record high temperatures in that region.

Statistical guidance based on the ENSO state and teleconnections would typically favor a colder regime for the first half of December in the Middle Atlantic and southern New England regions. Both historic experience following exceptionally warm November cases suggest that a warmer than normal December remains the base case even if the first half of the month winds up colder than normal. 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 ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around November 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.87°C and the ENSO Region 3.4 anomaly has averaged -1.40°C. La Niña conditions will likely prevail at least through the winter.

The SOI was +15.78.

Today, the preliminary Arctic Oscillation (AO) figure was +0.160.

On December 1 the MJO was in Phase 4 at an amplitude of 0.951 (RMM). The November 30-adjusted amplitude was 0.850.

Based on the latest guidance, no significant stratospheric warming event is likely through the middle of the second week of December. Some warming above 2 mb is likely toward the latter part of the first week of December on account of Wave 1 activity. However, gradual cooling should commence afterward.  

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.

 

[snowman19]

The GEFS and GEPS have completely lost all of the high latitude blocking (-EPO, -NAO, -AO) in the long range, I strongly suspect the EPS will be next. This is shades of last winter when the EPS would insist on high latitude blocking mirages in the long range, run after run, only for them to completely disappear as you move forward in time

[CIK62]

The next 8 days are averaging 41degs.(36/45).      Making it 36degs., or about -3.0.

GFS with some snow on the 13th.

36*(65%RH) here at 6am.      44* by Noon.    46* by 12:30pm.      49* by 3pm.       48* by 8pm.

[Allsnow]

The ensembles did a good job of predicting the ridge in west and trough in the east this weekend. It’s just small details that we won’t know until closer in. This weekend we have a nice 50/50 Feature that wasn’t their earlier. 

[LibertyBell]

17 minutes ago, bluewave said:

It’s a challenge to sustain a higher latitude blocking pattern with such a strong PV. Notice the much lower heights showing up south of Greenland now with that persistent cold pool out there. That cold over warm SST anomaly  may also help to reinforce the pattern.

New run

 

Old run

 

We place way too much focus on ENSO, I have a feeling this would have been the case even without a La Nina.  In a neutral phase for example.  We might need a really strong El Nino to break this pattern (maybe next year lol).  I wouldn't mind another 2015-16.  Sacrifice December for a whopper come January/February.

 

 

[LibertyBell]

8 minutes ago, Allsnow said:

The ensembles did a good job of predicting the ridge in west and trough in the east this weekend. It’s just small details that we won’t know until closer in. This weekend we have a nice 50/50 Feature that wasn’t their earlier. 

Yeah those things seem to be just as unpredictable as they were 30 years ago hence why noreasters are so hard to forecast 3 days out.

 

[donsutherland1]

Morning thoughts...

Today will be partly to mostly sunny and milder. Temperatures will likely reach the upper 40s and lower 50s in most of the region. Likely high temperatures around the region include:

New York City (Central Park): 49°

Newark: 52°

Philadelphia: 52°

A storm could bring a significant rainfall to coastal areas and at least some accumulating snow inland early this weekend followed by colder weather. The rain could even end as some snow or flurries in the I-95 Corridor.

[MJO812]

21 minutes ago, Allsnow said:

The ensembles did a good job of predicting the ridge in west and trough in the east this weekend. It’s just small details that we won’t know until closer in. This weekend we have a nice 50/50 Feature that wasn’t their earlier. 

This is why we should take long range forecasts with a grain of salt. I mean even the forecast for this weekend especially in New England isn't set in stone just yet.

[Neblizzard]

5 hours ago, snowman19 said:

The GEFS and GEPS have completely lost all of the high latitude blocking (-EPO, -NAO, -AO) in the long range, I strongly suspect the EPS will be next. This is shades of last winter when the EPS would insist on high latitude blocking mirages in the long range, run after run, only for them to completely disappear as you move forward in time

Models can’t be trusted 24 hours out let alone 15 days out.  It’s amazing you always post when they show an unfavorable solution for snow.  The models are finally predicting warming closing in on the polar stratosphere .  If the PV stretches then cold air can plunge south mid-late December into January for the east. 

[the_other_guy]

32F as a sea of warmth with transient cold shots and warm rain continues.

Very consistent pattern through several years of shifting blocking, pac jet, mjo, nina, nino, and month.

I predict it will continue...without ever looking at Day 10 on a LR forecast

[SnoSki14]

1 hour ago, jfklganyc said:

32F as a sea of warmth with transient cold shots and warm rain continues.

Very consistent pattern through several years of shifting blocking, pac jet, mjo, nina, nino, and month.

I predict it will continue...without ever looking at Day 10 on a LR forecast

The only thing consistent is that warmth will always win out. 

2000-2018 will be the best snow period we'll ever experience and it's all downhill from there. 

[KEITH L.I]

2 minutes ago, SnoSki14 said:

The only thing consistent is that warmth will always win out. 

2000-2018 will be the best snow period we'll ever experience and it's all downhill from there. 

the greatest 3 year snow droughts in my life

1989-1992

1997-2000

2018-2021?..I really believe we will see over 20 inches this year to avoid putting this in the top 3

 

[Stormlover74]

27 minutes ago, KEITH L.I said:

the greatest 3 year snow droughts in my life

1989-1992

1997-2000

2018-2021?..I really believe we will see over 20 inches this year to avoid putting this in the top 3

 

90-91 was fairly close to average at least in NYC 

[FPizz]

52 minutes ago, KEITH L.I said:

the greatest 3 year snow droughts in my life

1989-1992

1997-2000

2018-2021?..I really believe we will see over 20 inches this year to avoid putting this in the top 3

 

If 2018 means 17/18 winter, then we were above average.  

18/19 at my location here we were only about 3" under normal, so not bad.

Last year was a bottom 3 winter since I've been alive.  Hopefully this year we can reach over 20

[MJO812]

2 hours ago, Neblizzard said:

Models can’t be trusted 24 hours out let alone 15 days out.  It’s amazing you always post when they show an unfavorable solution for snow.  The models are finally predicting warming closing in on the polar stratosphere .  If the PV stretches then cold air can plunge south mid-late December into January for the east. 

Exactly 

[uncle W]

1 hour ago, KEITH L.I said:

the greatest 3 year snow droughts in my life

1989-1992

1997-2000

2018-2021?..I really believe we will see over 20 inches this year to avoid putting this in the top 3

 

after 1995-96 the winter of 1996-97 felt the worse for me...the following year was the worst or one of them...98-99 was very bad too...

[romba]

3 hours ago, Neblizzard said:

Models can’t be trusted 24 hours out let alone 15 days out.  It’s amazing you always post when they show an unfavorable solution for snow.  The models are finally predicting warming closing in on the polar stratosphere .  If the PV stretches then cold air can plunge south mid-late December into January for the east. 

True, but a bit hyperbolic. 48 hours you tend to get a solid picture of even the more complex systems. At 72 hrs most models are close enough to each other to know a real risk or not. But anything more than that is just popcorn fodder.