2025-2026 ENSO

[stadiumwave]

4 hours ago, PhiEaglesfan712 said:

Previous years with similar ENSO/IOD/PDO patterns. They tend to have cool Decembers, but torch in January and February.

Actually not the -QBO years with anykind of early strat warming. JAN is the coldest in that analog package. Will not be this year but just saying. 

[BlizzardWx]

1 minute ago, GaWx said:

 The 12/13/25 WPO of -348 is the most negative WPO on any day in December since 12/25/1996!

 The only Decembers since 1948 with at least one day lower than -348 are:

1996, 1989, 1983, 1977, 1966, 1955

I've been trying to think about what is "going wrong" with such a prolific -WPO to be talking about record warmth down my way. Do you know if a -WPO is typically good for the southern Plains? Is it perhaps atypical to have a -WPO paired with a -PNA or is that typical? I know when I look at the current pattern it seems reasonable to have a west coast trough downstream of that high but maybe sometimes ridging extends further southeast? 

Mostly just trying to build my understanding for this index. 

[GaWx]

 Well, as of Dec 13th, the MJO still hasn’t returned to phase 8! It was in 8 only Dec 3rd-7th. Dec 8th-13th have all been in very weak (essentially neutral) phases 5-7. I still think it has a good chance to get back into 8 very soon, but we’ll see:

[PhiEaglesfan712]

3 hours ago, bncho said:

Genuinely curious--could you provide some examples?

The most obvious ones are the most recent: 2016-17 and 2022-23.

2 hours ago, MJO812 said:

Nothing

I have a hard time seeing a torch in January and February with a neutral enso going into el nino.

In case you forgot, here's what happened the last time a dissipating la nina led into an el nino:

[GaWx]

1 hour ago, BlizzardWx said:

I've been trying to think about what is "going wrong" with such a prolific -WPO to be talking about record warmth down my way. Do you know if a -WPO is typically good for the southern Plains? Is it perhaps atypical to have a -WPO paired with a -PNA or is that typical? I know when I look at the current pattern it seems reasonable to have a west coast trough downstream of that high but maybe sometimes ridging extends further southeast? 

Mostly just trying to build my understanding for this index. 

 I’ll check now for December. These 9 were solidly -WPO Decembers dominating throughout the entire month:

2013, 2010, 2009, 2005, 1995, 1989, 1980, 1961, and 1956. Of these:

 

1) Cold in the S Plains?

2013, 2009, 2005, 1989, 1961

 

2) Near normal S Plains?

2010, 1995

 

3) Mild S Plains?

1980, 1956

 

 So, strong -WPO Decembers leaned somewhat to the cold side in the S Plains, but only 5 of 9 averaged cold. It looks like this year may end up averaging near normal based on a cold 1st half and mild 2nd half. But we’ll see.

 

PNA for these 9 Decembers:

2013: moderate -PNA

2010: strong -PNA

2009: weak +PNA

2005: strong +PNA

1995: moderate +PNA

1989: moderate +PNA

1980: weak -PNA

1961: strong -PNA

1956: weak -PNA

 

 So, PNA for these solidly -WPO Decembers is very mixed.

[snowman19]

7 hours ago, GaWx said:

 The 12/13/25 WPO of -3.48 is the most negative WPO on any day in December since 12/25/1996!

 The only Decembers since 1948 with at least one day lower than -3.48 are:

1996, 1989, 1983, 1977, 1966, 1955

The 1989-90 winter saw what was probably the biggest complete pattern flip in the last 50+ years. We went from a record cold arctic ice box from November through the end of December, then there was a big cutter on New Year’s Eve and a light switch flip to a full on torch for all of January and February 

[EasternLI]

Two clusters on eps cluster analysis in the long range last night. -NAO of unknown impact the general idea. There is a road in some analogs where we start January with a -NAO and as we lose that, the PNA goes positive. Could we take that road this year?

[40/70 Benchmark]

8 hours ago, GaWx said:

 The 12/13/25 WPO of -3.48 is the most negative WPO on any day in December since 12/25/1996!

 The only Decembers since 1948 with at least one day lower than -3.48 are:

1996, 1989, 1983, 1977, 1966, 1955

All 6 of those seasons finished with a mean DM -WPO, so this season should, too....though we could have a month or two average +WPO, as was the case in 1990. Looks like I am going to be off on the WPO again...it's so tough to forecast. At least I didn't go strongly positive....

[40/70 Benchmark]

7 hours ago, PhiEaglesfan712 said:

The most obvious ones are the most recent: 2016-17 and 2022-23.

In case you forgot, here's what happened the last time a dissipating la nina led into an el nino:

2016-2017 lead into another La Nina...not an El Nino.

I don't think that really has any value here, aside from the fact that February will often bias the Jan-Feb period warm in the east in a La Nina. 2022-2023 was a deeply +WPO/-PNA season, and I'm quite certain that won't be the case this season. Doesn't mean the second half will necessarily be great, but I don't think much can be gleaned from that particular composite.

[40/70 Benchmark]

8 hours ago, stadiumwave said:

Actually not the -QBO years with anykind of early strat warming. JAN is the coldest in that analog package. Will not be this year but just saying. 

I will be surprised if we don't see a major SSW and full reversal later this season.

[EastonSN+]

9 hours ago, GaWx said:

 The 12/13/25 WPO of -3.48 is the most negative WPO on any day in December since 12/25/1996!

 The only Decembers since 1948 with at least one day lower than -3.48 are:

1996, 1989, 1983, 1977, 1966, 1955

3 good and 3 bad winters snowfall wise. Nice even split.

[40/70 Benchmark]

34 minutes ago, EastonSN+ said:

3 good and 3 bad winters snowfall wise. Nice even split.

I would take 1996 and run relative to what I have had recently...December was nice, and had an early April event for the ages.

[GaWx]

1 hour ago, 40/70 Benchmark said:

All 6 of those seasons finished with a mean DM -WPO, so this season should, too....though we could have a month or two average +WPO, as was the case in 1990. Looks like I am going to be off on the WPO again...it's so tough to forecast. At least I didn't go strongly positive....

 

57 minutes ago, EastonSN+ said:

3 good and 3 bad winters snowfall wise. Nice even split.

 Thanks. That’s based on my 1st list, which is of those Decembers that had 1+ days dipping lower than -3.48. But those Decembers didn’t necessarily have a solid -WPO dominating through the entire month. One of those Decembers, 1996, actually averaged a +WPO overall. Also, 1983 and 1977 didn’t average a negative enough WPO. And there were a bunch of Decs left out of that 1st list that had a very -WPO with it dominating throughout but that didn’t have at least one day dip below -3.48 like 2013, 2010, 2009, 1995, 1980, 1961, and 1956 that make them good -WPO Dec analogs.

 OTOH, the 2nd list included some that weren’t -ENSO through the winter or at all like 2009, 1989, 1980, and 1956. In addition, 2005 and 1995 had a moderate or strong +PNA in Dec.

 So, what are we left with for the best analogs based on solid -WPO throughout Dec, -ENSO through the winter, and a moderate to strong -PNA in Dec? 2013, 2010, and 1961. Of these three, the PNA flipped to positive in Jan in 2014 and 2011 and to neutral in Jan of 1962.

  So, the closest -ENSO/Dec -WPO/Dec -PNA analogs are 2013, 2010, and 1961.

[EastonSN+]

26 minutes ago, GaWx said:

 

 Thanks. That’s based on my 1st list, which is of those Decembers that had 1+ days dipping lower than -3.48. But those Decembers didn’t necessarily have a solid -WPO dominating through the entire month. One of those Decembers, 1996, actually averaged a +WPO overall. Also, 1983 and 1977 didn’t average a negative enough WPO. And there were a bunch of Decs left out of that 1st list that had a very -WPO with it dominating throughout but that didn’t have at least one day dip below -3.48 like 2013, 2010, 2009, 1995, 1980, 1961, and 1956 that make them good -WPO Dec analogs.

 OTOH, the 2nd list included some that weren’t -ENSO through the winter or at all like 2009, 1989, 1980, and 1956. In addition, 2005 and 1995 had a moderate or strong +PNA in Dec.

 So, what are we left with for the best analogs based on solid -WPO throughout Dec, -ENSO through the winter, and a moderate to strong -PNA in Dec? 2013, 2010, and 1961. Of these three, the PNA flipped to positive in Jan in 2014 and 2011 and to neutral in Jan of 1962.

  So, the closest -ENSO/Dec -WPO/Dec -PNA analogs are 2013, 2010, and 1961.

Such a small dataset. 1961/1962 was the only dud.

All three years embedded in the 2 epic snowfall periods (1955 to 1969 and 2000 to 2018).

 

[JenkinsJinkies]

1 hour ago, 40/70 Benchmark said:

2016-2017 lead into another La Nina...not an El Nino.

I don't think that really has any value here, aside from the fact that February will often bias the Jan-Feb period warm in the east in a La Nina. 2022-2023 was a deeply +WPO/-PNA season, and I'm quite certain that won't be the case this season. Doesn't mean the second half will necessarily be great, but I don't think much can be gleaned from that particular composite.

Also 16-17, 22-23 had no measurable December snow in the DC and Baltimore area airports. Very much not the case this year.

[GaWx]

7 minutes ago, JenkinsJinkies said:

Also 16-17, 22-23 had no measurable December snow in the DC and Baltimore area airports. Very much not the case this year.

Also, Dec of 2016 had a +WPO and Dec of 2022 had a neutral WPO unlike the -WPO of Dec of 2025 fwiw.

[Krs4Lfe]

9 hours ago, PhiEaglesfan712 said:

The most obvious ones are the most recent: 2016-17 and 2022-23.

In case you forgot, here's what happened the last time a dissipating la nina led into an el nino:

That has been my fear for most of this month. Fortunately, unlike December 2022 all of us actually saw snow this month and some of us saw significant snow. And this month has actually been much colder overall. However, I remember all the great model prognostications about what will be waiting for us in January only for January to come, and the rest of winter was a torch with only a few inches of snowfall. We should not discount the ability for nature to switch up a good pattern on a dime. What looks to be a very cold month this month could easily be the opposite next month.

[40/70 Benchmark]

15 minutes ago, JenkinsJinkies said:

Also 16-17, 22-23 had no measurable December snow in the DC and Baltimore area airports. Very much not the case this year.

 

11 minutes ago, GaWx said:

Also, Dec of 2016 had a +WPO and Dec of 2022 had a neutral WPO unlike the -WPO of Dec of 2025 fwiw.

Yea, 2022-2023 has some utility as an analog, but it won't be as mild as those seasons in the east.

[GaWx]

6 minutes ago, 40/70 Benchmark said:

Does anyone have the link to the historical ERA5 10hPa 60N zonal wind data? For some reason my link no longer takes me to it....

Ray,

 If you mean the link to the site that produces the graphs of 10 hPa/60N mean zonal wind back to 1978-9, those could be produced by going in here:

https://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html#ncep_clim_stats_nh

 

 

[Terpeast]

Quick check on the ensembles today looks like a solid -pna pattern for at least the next two weeks with no credible snow threats for the MA. Perhaps some cold shots over the NE and MA. But we’re gonna have to wait this out a bit before the scand ridge retros into a GL block around new years. 

[MJO812]

6 minutes ago, Terpeast said:

Quick check on the ensembles today looks like a solid -pna pattern for at least the next two weeks with no credible snow threats for the MA. Perhaps some cold shots over the NE and MA. But we’re gonna have to wait this out a bit before the scand ridge retros into a GL block around new years. 

I do like that the NAO and AO are going down. I think around Christmas to New years will be our next threat in the east 

[40/70 Benchmark]

1 hour ago, GaWx said:

Ray,

 If you mean the link to the site that produces the graphs of 10 hPa/60N mean zonal wind back to 1978-9, those could be produced by going in here:

https://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html#ncep_clim_stats_nh

 

 

Yea, I had found it...you're quick!
Thanks.

[brooklynwx99]

30 minutes ago, Terpeast said:

Quick check on the ensembles today looks like a solid -pna pattern for at least the next two weeks with no credible snow threats for the MA. Perhaps some cold shots over the NE and MA. But we’re gonna have to wait this out a bit before the scand ridge retros into a GL block around new years. 

yeah, i'm pretty confident that we're going to see the NAO drop rather significantly as the Scandi / N ATL trough retrogrades... the WH MJO forcing is a strong precursor to that, as it helps wavebreaking occur in the N ATL

[Terpeast]

7 minutes ago, brooklynwx99 said:

yeah, i'm pretty confident that we're going to see the NAO drop rather significantly as the Scandi / N ATL trough retrogrades... the WH MJO forcing is a strong precursor to that, as it helps wavebreaking occur in the N ATL

Yep I see WH forcing in the hovmoller's forecasts, of which GFS is performing well lately. It's trying to go into phases 1 and 2, with a bit of ensemble support.

[michsnowfreak]

First half of December was very impressive in its persistence of cold. The depth of cold was more impressive in the Great Lakes than the northeast, but even then, the widespread magnitude of well below normal temperatures was impressive over a huge area. The entire first half of December is almost ironic given the numerous posts in this very thread about volcanoes, cold being brief and not widespread, etc.

First half of December rankings:
Flint: 3rd coldest in 105 years
Ann Arbor: 4th coldest in 145 years***
Detroit: 5th coldest in 152 years
Grand Rapids: 5th coldest in 133 years
Green Bay: 6th coldest in 140 years
Toledo: 7th coldest in 153 years
Cleveland: 8th coldest in 155 years
Pittsburgh: 8th coldest in 151 years
Baltimore: 10th coldest in 154 years
Lansing: 12th coldest in 163 years
Chicago: 13th coldest in 154 years
Milwaukee: 13th coldest in 155 years
Washington DC: 19th coldest in 154 years
New York City: 25th coldest in 157 years

For Detroit, going back to 1906 (as far as I have records), 2025 is officially only the 2nd December to have 1”+ snowcover every day for the first half of December. The only other time was 1910. To be fair, we should include 1974, as a massive snowstorm hit on Dec 1st but the snow depth at 7am was just a T. Even then, only 1910, 1974, and 2025 were nonstop blanketed in snow the entire first half of December. This shows just how early it REALLY is, but we just have to hope that the entire load of cold wasnt blown before the Winter Solstice.

*** I included Ann Arbor as even though it isnt a first order station, it is one of the few stations you will find whos location has never moved (Univ of Mich campus).

[Terpeast]

 

1 hour ago, michsnowfreak said:

we just have to hope that the entire load of cold wasnt blown before the Winter Solstice.

I don't think so.

Today:

2 weeks from now:

 

Still on our side of the globe and not too far from a widespread cold snap that could extend at least a couple of weeks down this way in January.

Yes, it's one ensemble run, but the source/placement of cold air hasn't really changed all that much from run to run.

[snowman19]

The Niña is going to reach its peak soon. This is the coldest reading in region 3.4 we’ve seen for this entire event

[donsutherland1]

13 hours ago, BlizzardWx said:

I've been trying to think about what is "going wrong" with such a prolific -WPO to be talking about record warmth down my way. Do you know if a -WPO is typically good for the southern Plains? Is it perhaps atypical to have a -WPO paired with a -PNA or is that typical? I know when I look at the current pattern it seems reasonable to have a west coast trough downstream of that high but maybe sometimes ridging extends further southeast? 

Mostly just trying to build my understanding for this index. 

Since 1980, for December cases with a WPO of -2 or below: PNA<0: 84.1%; PNA>0: 15.9%.

[TheClimateChanger]

3 hours ago, michsnowfreak said:

First half of December was very impressive in its persistence of cold. The depth of cold was more impressive in the Great Lakes than the northeast, but even then, the widespread magnitude of well below normal temperatures was impressive over a huge area. The entire first half of December is almost ironic given the numerous posts in this very thread about volcanoes, cold being brief and not widespread, etc.

First half of December rankings:
Flint: 3rd coldest in 105 years
Ann Arbor: 4th coldest in 145 years***
Detroit: 5th coldest in 152 years
Grand Rapids: 5th coldest in 133 years
Green Bay: 6th coldest in 140 years
Toledo: 7th coldest in 153 years
Cleveland: 8th coldest in 155 years
Pittsburgh: 8th coldest in 151 years
Baltimore: 10th coldest in 154 years
Lansing: 12th coldest in 163 years
Chicago: 13th coldest in 154 years
Milwaukee: 13th coldest in 155 years
Washington DC: 19th coldest in 154 years
New York City: 25th coldest in 157 years

For Detroit, going back to 1906 (as far as I have records), 2025 is officially only the 2nd December to have 1”+ snowcover every day for the first half of December. The only other time was 1910. To be fair, we should include 1974, as a massive snowstorm hit on Dec 1st but the snow depth at 7am was just a T. Even then, only 1910, 1974, and 2025 were nonstop blanketed in snow the entire first half of December. This shows just how early it REALLY is, but we just have to hope that the entire load of cold wasnt blown before the Winter Solstice.

*** I included Ann Arbor as even though it isnt a first order station, it is one of the few stations you will find whos location has never moved (Univ of Mich campus).

Looks like the "high water mark" for the cold, so to speak. With upcoming pattern change, final December numbers should be rather ho-hum.

[michsnowfreak]

Just now, TheClimateChanger said:

Looks like the "high water mark" for the cold, so to speak. With upcoming pattern change, final December numbers should be rather ho-hum.

The month will nearly certainly finish colder than avg, though the extent of the upcoming thaw (and how much of the near record warmth in the southern plains makes it north) will dictate just how much.