2025-2026 ENSO

[EastonSN+]

Seems the difference between the GEFS dumping the trough out west as opposed to the EPS is the handling of the MJO. While the EPS is essentially in the COD, GEFS is moving to phase 6.

[GaWx]

3 hours ago, EastonSN+ said:

Seems the difference between the GEFS dumping the trough out west as opposed to the EPS is the handling of the MJO. While the EPS is essentially in the COD, GEFS is moving to phase 6.

 
 Today’s EPS and CFS are also going to ph 6 mid Jan. BAMwx posted that phase 6 in -AAM during Jan has been very cold in the E US, with the most intense cold in the interior SE (see lower right in image just below), which to me was very counterintuitive. So, I needed to know the answer.

 

  Now it’s even more important to know as the move to ph 6 midmonth now has increasing model support. The following are results of my research done on Tue, which looked at GSP, a station in that coldest (pink) area, during La Niña:

 

Niña Year….# phase 6 days…avg anomaly

1975…3…-8 M

1976…13…-9 W-S

1989…3…+8 M

1999…3…+2 M

2000…3…-4 W

2006…6…+3 S

2008…3…+8 S

2009…6…+1 W-M

2011…12…-7 W-S

2012…19…+1 W-S

2017…2…0 W

2018…3…-2 S

2021…8…-1 M-S

2022…4…-9 W

2025…2…-5 W

W weak (mainly in or near circle), M mod., S strong

91 total days (big sample)

—————

So, 15 cases of ph 6 during Nina Jans:

3 MBN

3 BN

6 NN

1 AN

2 MAN

——————— 

- These La Nina Jan results weren’t at all what I would have expected for phase 6, one of the 3 mild Jan phases in the SE averaged out over all years:

 

- Though there’s not surprisingly lots of variability, GSP did average 2 BN. Before seeing BAMwx’s post I never would have expected this. However, it should also be noted that BAM’s -6 to -7 for GSP is at the same time significantly too cold. 

- Only 3 of the 15 Jan cases were AN to MAN: 1989, 2006, and 2008. These were all M to S intensity (intuitive).

- So, none of the last 8 were mild as there were 5 NN and 3 BN (2011, 2022, and 2025). These also averaged 2 BN. The weakest 3 averaged a solid cold 6 BN.

- Thus if phase 6 continues to look more likely for midmonth, it will be interesting to see whether or not the NN to cold dominance works out in the SE (and E overall by association), especially if the bulk of ph 6 turns out to be anywhere from inside the circle to near/just outside the circle.

@donsutherland1

[PhiEaglesfan712]

3 hours ago, bluewave said:

A large portion of the West had their warmest December on record. But none of the areas in the East that were cold approached their coldest December on record. This has been a common theme in recent years with the warm departures being more impressive than the cold departures on a month to month basis. 
 

 

 

Climatologist49

 

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December 2025 temperature ranking (since 1895). A lot of the West had their warmest December on record and nearly everywhere out west had a top 5 warmest December. 

 

10:26 PM · Jan 1, 2026

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Climatologist49

 

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The month-to-date temperature departure from normal for the Contiguous U.S. is +3.9F. If this is how the month ends, December 2025 would finish as the 4th warmest December on record (1895-present). 4 of the top 5 would include 2021, 2023, 2024, and 2025. It's as if something has changed.

11:47 AM · Dec 29, 2025

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lol, this looks more like an el nino or a +PDO than a typical -ENSO/-PDO.

[GaWx]

4 hours ago, bluewave said:

A large portion of the West had their warmest December on record. But none of the areas in the East that were cold approached their coldest December on record. This has been a common theme in recent years with the warm departures being more impressive than the cold departures on a month to month basis. 
 

 

 

Climatologist49

 

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December 2025 temperature ranking (since 1895). A lot of the West had their warmest December on record and nearly everywhere out west had a top 5 warmest December. 

 

10:26 PM · Jan 1, 2026

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Climatologist49

 

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The month-to-date temperature departure from normal for the Contiguous U.S. is +3.9F. If this is how the month ends, December 2025 would finish as the 4th warmest December on record (1895-present). 4 of the top 5 would include 2021, 2023, 2024, and 2025. It's as if something has changed.

11:47 AM · Dec 29, 2025

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Dec ‘25 will end up cooler than +3.9F once Dec 29-31 are added. Why? Because Dec 29-31 averaged NN to slightly BN vs 1991-2020 climo overall based on my rough est. That could be as cold as ~30 for those 3 days.

 So, the question isn’t if it will end up cooler because it has to based on the above. The question is how much will it bring down the +3.9. Roughly, you’d be adding a 10% weighting with as cold as ~-1 (based on 1991-2020 anomaly) to a 28 day of +3.9. That would come out to ~+3.4 IF the last 3 days were really -1. If it goes back down to ~+3.4, then it could also end up cooler than 1939, something @TheClimateChangerand I have been discussing. Even if Dec 29-31 averaged near 0 anomaly, that would still bring Dec as a whole down to +3.5, still quite possibly cooler than 1939.

 Also, 2015 may turn out warmer. So, 2025 could come in 6th or so.

 This chart only goes through 2021:

Edit: note that per this chart that 1939 was >+5.5 F vs its climo and 1957 was ~+3.9.

[SnowGoose69]

28 minutes ago, PhiEaglesfan712 said:

lol, this looks more like an el nino or a +PDO than a typical -ENSO/-PDO.

A strong El Nino December would rarely have those anomalies from ND into the Lakes, they'd normally  be above normal.  Sometimes the immediate EC can be below but El Nino Decembers, even weak to moderate ones often are not cold anywhere except the Deep South and SE and that is often just a relativity thing where a place like ATL/BNA might average -1 largely due to lots of overcast and rainy days but not exactly have a ton of days in the 40s or below or nights below 32.  An El Nino January or February can have that type of departure map though