2025-2026 ENSO

[40/70 Benchmark]

50 minutes ago, EastonSN+ said:

2000-2001 central park had 35 inches. I believe the 30 year average at that time was approx 27 so  slightly above average.

2008-2009 central park had 27.6, which at that time I believe that average was approx 28 so basically average. 

2007-2008 was only 11.9 so a dude.

So IF we only took those three examples an equal chance of above, average and below snowfall.

I went 19-29" for you guys, so kind of the middle of those years.

[EastonSN+]

1 minute ago, 40/70 Benchmark said:

I went 19-29" for you guys, so kind of the middle of those years.

I technically live in New England. However my climate is much closer to central park than Boston.

[bluewave]

2 hours ago, snowman19 said:

So far since November, we’ve seen -WPO (Aleutian ridge regime) driven cold. This is in contrast to the -EPO (Alaskan ridge regime) driven cold we saw last winter….. @SnowGoose69 @donsutherland1 @bluewave
 

Strengthening La Niña background state with the falling AAM heading into mid-December leading to the very amplified Aleutian Ridge and -PNA trough.

 

[Terpeast]

26 minutes ago, bluewave said:

Strengthening La Niña background state with the falling AAM heading into mid-December leading to the very amplified Aleutian Ridge and -PNA trough.

 

Trending down, yes, but the thing is AAM forecasts have been biased too negative over the past 30 days. When correcting for that, AAM may be closer to neutral. 

[roardog]

2 hours ago, EasternLI said:

That's a frigid look just starting at the end of the eps last night... -WPO loading Canada with cold air. With SW US ridging is going to relay that SE... I'll roll the dice with that anytime. 

I would think air that cold will drain south and east and cause wintry chances even if you aren't under the blue negative height anomalies.

[GaWx]

2 hours ago, PhiEaglesfan712 said:

After that, do you think the winter returns, or are we going to torch in January and February, like in 2016-17 and 2022-23?

 Or will Jan be cold like in 1984, 1985, 2009, 2011, 2014, and 2022?

Or will Jan be within a few degrees of normal (in the NE at least) like 1997, 1999, and 2013?

 So, Jan has had 3 times as many cold vs warm for the analogs since 1983-4 that I’m looking at.

 OTOH, Feb has a better chance to torch in the NE imho as only 2014 of the analogs I’m looking at was solidly cold there vs 6 being cold in Jan. In Feb, these were mild: 1984, 1997, 1999, 2009, 2017, and 2023.

 So, in Feb, 6 times as many were mild vs cold. That compares to 3 times as many cold vs mild in Jan. Two very different months on average.

[donsutherland1]

3 hours ago, snowman19 said:

If that’s correct, a cold look for sure. A coastal storm pattern, not so much (++NAO/flat PNA). Maybe fast moving, progressive clippers? 
 

EDIT: @EastonSN+ Snowfall in -WPO patterns vs -EPO patterns is a good question. @donsutherland1 is the man to ask about that

Here's the data for New York City:

Below are the composite 500 mb anomalies for WPO<0 December cases for 4" or more daily snowfall. To date, the guidance does not suggest the kind of pattern shown below.

 

It should also be noted that snowfalls tend to be light during the first half of December when the AO/NAO/PNA are all negative. 

[GaWx]

 Just like yesterday, the GEFS and EPS disagree on how long the MJO will stay in phase 8:

GEFS: only 6 days though it returns for rd 2 on 12/18:

But the EPS, which recently has been much steadier and has been verifying better than GEFS since phase 7, once again is going with a very long phase 8 (16+ days, longest in 50 years): you can’t place an MJO better than this in Dec for E US cold lovers (and it looks to be cold the next 10 days per models though one must remember that there are always other factors to consider due to the complexity of the atmosphere):

[stadiumwave]

I think we are going to see plenty of cold but the pattern is going to be overall dry...maybe clippers...etc. I think the 12z CMC has a better handle on the next 10 days over the GFS. It's not a great winter storm pattern by any means.

[stadiumwave]

[jconsor]

On 12/3/2025 at 2:17 PM, donsutherland1 said:

IMO, this oversimplifies the PNA. A PNA- is not only possible, but is likely to be the predominant state this month based on broad consensus of the guidance. There's a lot more that contributes to the PNA.

So far, December has seen PNA values of +0.022 on December 1st and -0.149 on December 2nd. 

Yesterday's GEFS forecast:

Here's the EPS 46-Day forecast:

Last winter provides a good example of how one can reach incorrect conclusions from oversimplifying things. Despite the La Niña, the PNA was positive on almost 96% of days. It was also +1.000 or above on 34% of days. ENSO-PNA mismatches can occur. These mismatches are a product of a more complex ocean-atmosphere system than would be suggested by simpler rules. In short, even as there is a tendency for the PNA to be negative during La Niña/positive during El Niño (same direct relationship with regard to the PDO), that tendency is far from iron-clad.

All said, I see little at this time to suggest that the base scenario of a PNA- December has grown less likely. The continued persistence of the guidance has, if anything, reinforced the base scenario of a predominant PNA- overall.

I hear your point about the dangers of oversimplying ENSO-PNA relationships, Don, and wholeheartedly agree.  However, from my perspective there is increasing evidence the PNA will average neutral overall (with some periods of slightly positive PNA, especially Dec 7-9 and Dec 14-20) the second and third weeks of Dec.  

True, the EPS pattern days 3-7 and 11-15 is not fully in line with a canonical +PNA (the positive anomalies are shifted south and west vs. the typical position over western Canada and the NW US, the negative anomalies are concentrated over SE Canada and the NE US vs. the mid-Atlantic and SE US, and the upstream negative anomalies are in the e. Gulf of Alaska vs. the typical position further SW in the north-central Pacific). 

However, both the EPS and GEPS have been trending toward a more neutral PNA in most of the next two weeks (e.g. Dec 7-10 and Dec 14 and beyond).   The charts you showed were from the GEFS, which has the most -PNA (and SE US ridge) biased of all the models recently.  

Also, looking at the EPS individual members it is evident that a few members with a highly negative PNA are skewing the mean downward Dec 14 onward.  A slightly majority of members (about 55-60%) actually show a +PNA during that timeframe!
The GEPS is not as aggressive, but still has about 40-50% of members showing a +PNA in the same timeframe.

Regarding the last third of Dec, there is too much uncertainty to comment much on that period.  While I favor the SE US ridge returning to a degree, I am skeptical of the strength of the NW/N-central US trough and SE US/W Atlantic ridge shown in the past two EPS long-range runs.

[snowman19]

40 minutes ago, stadiumwave said:

At this point I don’t think the question is “will December be cold?”. Very likely to average cold. I think the bigger, million dollar question will be snow. As of right now, the pattern does not look conducive at all for east coast, I-95 corridor snowstorms. I agree with your take in the post you made earlier in that regard. If December ends up colder than normal with below average snow, I think most on here would consider that a loss

[jconsor]

7 hours ago, donsutherland1 said:

It also looks likely to persist through at least mid-December, if not longer.

I agree that the -WPO will remain the most dominant influence on the cold through mid-Dec.  However, there are increasing indications that in the 10-15 day period (Dec 13 and beyond), the center of the most anomalous ridging will shift significantly NE from the Kamchatka Peninsula/western Bering Sea to the Bering Strait, with the eastern extent of positive anomalous also shifting notably eastward into AK and even parts of the Northwest Territories.  Combined with the increased negative anomalies north/NE of Hawaii and below normal heights over the NE US, that suggests a -EPO. 

This more eastward position of the ridging could theoretically allow the most anomalous cold air to be directed toward the NE US beyond Dec 15, though the lack of ridging over Greenland and the relatively northward position of the polar vortex indicated by the guidance e.g. north of Hudson Bay (I am mainly speaking about EPS and GEPS) would counteract this. 
 

[jconsor]

3 hours ago, stadiumwave said:

I think we are going to see plenty of cold but the pattern is going to be overall dry...maybe clippers...etc. I think the 12z CMC has a better handle on the next 10 days over the GFS. It's not a great winter storm pattern by any means.

I agree with you in general.  However, there is a timeframe that I think has more potential for a negative tilt, digging trough late next week into next weekend (Dec 11-14).  This is the timeframe that both operational models and ensembles show the blocking retrograding from western Greenland to near Baffin Island and then into central Canada, and possibly linking up with western US ridging.  The period when blocks retrograde and decay into Central Canada and then link up with western US ridging is the one when significant snowstorms are most likely in the coastal parts of the NE US. 

Now to clarify, I don't see the potential for a significant (6"+ snowstorm) for the I-95 corridor from NYC to BOS.  But my point is that the pattern does match periods which are more favorable for significant coastal storms along with sufficient cold air for snow.

Given the northern stream/clipper dominated pattern and the troughs turning negative tilt relatively late, snowfall would be most favored across far northern NY and northern New England, but eastern Long Island to SE New England also climatologically can do well in these types of events if they dig far enough south.  

The ECMWF and (to a degree) the GEM both show the above-mentioned blocking and negative tilt/digging trough trends late next week into next weekend.