December 2021

[donsutherland1]

IMO, @bluewave's posting top 10 outcomes is useful. It provides historic climate context. For example, if one looks at the 10 warmest first weeks in December at Islip, one finds that 7 of the 12 years (some ties lead to a n>10) have occurred 2000 or later. This information is especially valuable when one is dealing with stations with long periods of record. That such warmth is becoming a "new normal" is a different issue.

Looking in greater detail, ISP saw 6/7 days above normal during the first week of December. 2 days had anomalies of +5 or above (1 of which had an anomaly > +10).

By any measure, the first week of December was a warm one. Such warmth is becoming more frequent. It is no surprise that the 1991-2020 climate normals are warmer than the 1981-2010 ones given these developments.

[donsutherland1]

NWS Boulder: Denver: 0.3” snow

[Rjay]

39 minutes ago, bluewave said:

I don’t understand what you mean by running around like chicken little. Putting our temperatures in perspective is very important otherwise we just normalize everything away in a few years. That was what the study that I posted earlier discussed. New baselines are deceptive since a +2 to +3 in December today is getting near the top ten warmest. So it could lead some to say that such a small warm departure really isn’t out of the ordinary. 

Feel free to toss a weenie every now and then

[bluewave]

12 minutes ago, Rjay said:

Feel free to toss a weenie every now and then

I try to stay away from that since it reminds me of the poster from out of town that used to drop in here and weenie all the posts.

[forkyfork]

3 hours ago, Allsnow said:

Last three days at the park have been below normal with yesterday having the largest departure of -6. Didn’t get out of the 30’s yesterday. 

bye bye

 

[MJO812]

32 minutes ago, forkyfork said:

bye bye

 

We know

[SnoSki14]

38 minutes ago, forkyfork said:

bye bye

 

We'll get another tornado before we see more snow

[Brian5671]

if it's not going to snow let it torch.   Still waiting for any kind of decent synoptic storm-last one was 10/25 give or take.

[bluewave]

All-time December highest temperatures in the source region for the record warmth headed for our area .

 

[snowman19]

4 hours ago, donsutherland1 said:

With regard to the MJO, forecasting uncertainty beyond a week notwithstanding, there have been exceptions to what one would typically expect. In December 2001, the MJO moved into Phase 8. The EPO went negative late in the month and then reverted back to predominantly positive values in early January. At present, I still believe the base case is that it will turn cooler during the closing 10 days of the month. Severe cold may not occur in the Middle Atlantic region this month.

Afterwards, there will be a risk that the cooler pattern breaks down after two weeks or so, as the predominant EPO+/AO+/PNA- pattern tries to reassert itself. The Gulf of Alaska SSTs and PDO- may make it difficult to sustain a persistently cold pattern. Hopefully, my concerns will prove incorrect.

Overall, I still don’t think this will be a variation of the 2001-02 winter. But it will likely be mild (DJF anomaly) and the AO-seasonal snowfall data speaks for itself.

Allan Huffman shares your concerns:  

 

 

 

[MJO812]

58 minutes ago, Brian5671 said:

if it's not going to snow let it torch.   Still waiting for any kind of decent synoptic storm-last one was 10/25 give or take.

It's December 10

[snowman19]

@bluewave @donsutherland1 This would also question how long any end of month change lasts….if the models are correct about IO convection firing by the middle of next month:  

 

[MJO812]

All the models have a storm lurking at 240. Pattern is progressing nicely as we head into mid to late December. 

[snowman19]

5 minutes ago, MJO812 said:

All the models have a storm lurking at 240. Pattern is progressing nicely as we head into mid to late December. 

Mid December looks good? Long range, the GEFS just caved to the EPS and shows a massive -PNA and SE ridge going into late month 

[MJO812]

5 minutes ago, snowman19 said:

Mid December looks good? Long range, the GEFS just caved to the EPS and shows a massive -PNA and SE ridge going into late month 

How about the EPO? NAO?

[JustinRP37]

We haven't had many 'cold' winters in the past decade. Snowy yes, cold no. The two big exceptions were 2013-2014 and 2014-2015. Otherwise we have largely been warmer than average. Next week is mid December, we are going to want to see models continuing to show closer to average temperatures if we are to have a seasonable Christmas. And for the last time, people saying the warm up looks muted, you MUST take a look at low temperatures too! Our low temperatures are and have been warming more than our high temperatures. 

[MJO812]

7 minutes ago, snowman19 said:

They ARE going to bust bad? How could you possibly know exactly what is going to happen the end of this month for sure, 100% on December 10th? The only thing that has busted bad is the cold and snowy end of November through mid-December forecasts 

You are right on that part but you can't deny a better pattern  is looking likely after this brief warmup.  The length of the cold pattern is in question .

[EasternLI]

20 minutes ago, snowman19 said:

The tail end of the month into early January may be the time period to get the first “something” winter weather wise. The models are showing IO convection firing by mid-January, which would support GOA troughing/+EPO. It may be a window if a couple weeks or so assuming everything works out 

 

I don't have any thoughts yet about that far out. Any modeling beyond ensembles range I put very little faith in. 

[psv88]

13 minutes ago, MJO812 said:

You are right on that part but you can't deny a better pattern  is looking likely after this brief warmup.  The length of the cold pattern is in question .

Better pattern? I cannot get any worse, so sure.

[Great Snow 1717]

41 minutes ago, MJO812 said:

How about the EPO? NAO?

You are setting yourself up to be disappointed.

[Great Snow 1717]

21 minutes ago, psv88 said:

Better pattern? I cannot get any worse, so sure.

The only worse pattern...

[bluewave]

1 hour ago, snowman19 said:

This would also question how long any end of month change lasts….if the models are correct about IO convection firing by the middle of next month:  

We would need any potential MJO 8 near the end of December to be accompanied by a SSW for any possible improvements to last.  There have  plenty of hostile Pacific patterns in recent years. But this one has raised the bar on extremes of the +EPO, -PNA, and Pacific Jet.

 

 

[WeatherFox]

La Niña graphic for northeast weather. Unfortunately, not conducive to snow in the NYC area at this time.  You can hope things change in time, this winter..

[Nibor]

40 minutes ago, Great Snow 1717 said:

The only worse pattern...

[the_other_guy]

15 minutes ago, Nibor said:

 

[Brian5671]

most interesting this map has looked in 6 weeks

[CIK62]

The next 30 Days..........    Comes with less than 5" of snow on the EURO.       CFS a little better w/o being very different.      Snow unknown

 

[Brian5671]

7 minutes ago, CIK62 said:

The next 30 Days..........    Comes with less than 5" of snow on the EURO.       CFS a little better w/o being very different.      Snow unknown

 

looks like a -PNA there and raging SE ridge

[donsutherland1]

Temperatures will likely soar to near record and record levels tomorrow in the Middle Atlantic region in advance of another cold front. The air mass that will send temperatures reaching for records resulted in numerous records including:

Greenville, MS: 84° (old record: 82°, 1918) ***2nd highest December temperature***
Little Rock: 78° (tied record set in 1889)
Shreveport: 84° (old record: 78°, 2020) ***Tied December Record***

Passage of the front could be marked by strong winds and strong to perhaps severe thunderstorms. The front will bring a transient shot of somewhat cooler air to the region. A significant warmup is possible beginning after the middle of next week.

No Arctic blasts appear likely for the foreseeable future. Overall, through December 20th, temperatures will likely be warmer than normal in the means with some short-lived cool shots. Afterward, the AO could go negative, increasing the opportunity for colder outcomes.

Out West, Denver finally picked up its first measurable snowfall of the season. The previous record latest first measurable snowfall occurred on November 21, 1934. The progression of Denver's latest first measurable snowfall of the season is as follows:

November 11, 1882
November 16, 1894
November 19, 1931
November 21, 1934
December 10, 2021

The base case is that the closing 10 days of December could turn cooler, though not necessarily cold. Since 1950, there have been 7 cases where the AO averaged +2.000 or above during the first week in December, as has been the case this year. The mean December 21-31 temperature in New York City was 40.2°. The median temperature was 41.5°. The coldest was 35.3° (1951) and the warmest was 44.0° (1979). In short, this historic experience would suggest that there will be no severe Arctic outbreaks in the East this month. It also suggests that New York City will likely have an average temperature of 40° or above this month.

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 1. 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 -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +9.13 today.

The preliminary Arctic Oscillation (AO) figure was +1.143 today

On December 8 the MJO was in Phase 6 at an amplitude of 2.189 (RMM). The December 7-adjusted amplitude was 2.014 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 42.3° (3.2° above normal).

 

[Dan76]

Record highs are possible on Saturday, December 11.  Here are
current records for December 11.

EWR: 65/1971*
BDR: 65/1971
NYC: 64/1879
LGA: 62/1971
JFK: 67/1971
ISP: 65/1971