2025-2026 ENSO

[donsutherland1]

So far, things have gone pretty much as expected in December. The December 1-10 idea is verifying.

The big question concerning late December is whether the WPO- will weaken allowing unfavorable teleconnections to reshape the pattern. That is a possibility, but isn't certain. Other possibilities also exist. 

[MJO812]

The 12z model runs are once again trending away from a warmup in the long range.  Consistent theme.

[leo2000]

They are too you can see the EPO ridge in Alaska high heights where before there was low heights. This could a trend GEFS 12z shows this. 

[bluewave]

4 hours ago, stadiumwave said:

Some of the AI models are radically different on Day 10. It will be interesting to see which is modeled better.

Models usually don’t get exact timing for the relaxation of a pattern which has persisted for several weeks.

This is why I have been using the general recent climatology in December. Every year since 2011 from Philly to NYC there was at least 1 day reaching 55 or greater from the 17th to the 25th.

That period is still 9-17 days out which is beyond the reliable model skill. It doesn’t mean every day or even most days were this warm since 2011. Some years it was only a 1 day warm up with other years more than a day reaching these temperatures.

But the general December patterns over the years which have had a cold December 1-16th had moderated in the departures from the 17th through the 31st. The degree of this moderation has also been variable. 

 

[stadiumwave]

From Paul Roundy:

"Base state supports Bering Strait and Greenland blocking, with troughing in the eastern US. A fast component of the MJO signal moves through Indian basin to Maritime Continent 15-30 Dec offsetting the cold eastern US signal and potentially forcing a period of warm anomalies in the eastern US."

 

[bluewave]

3 hours ago, donsutherland1 said:

So far, things have gone pretty much as expected in December. The December 1-10 idea is verifying.

The big question concerning late December is whether the WPO- will weaken allowing unfavorable teleconnections to reshape the pattern. That is a possibility, but isn't certain. Other possibilities also exist. 

I suspect that the issues the models have been having long range are related to the much faster Northern Stream of the Pacifc Jet which continues. It’s not typical to get a strong -WPO +EPO couplet  at the the same time in December. So the shortwaves in the fast Pacific flow are lowering heights over Eastern Alaska while the -WPO ridge stands firm.

At least into mid December the +EPO and stronger Pacific are trying to have the ridge roll out into the Plains while the -WPO would have the ridge axis more in the West. So a tug of war between two competing influences that we normally don’t see at the same time.

My guess is that the ridge eventually comes east at some point during the 2nd half of December as the Pacific Jet eventually wins out in these situations. Notice how the 10 year December strong -WPO composite features a more -EPO and a relaxed Pacific Jet.
 

Much stronger Pacific Jet and unusual +EPO in mid-December for a very strong -WPO block

Past 10 strongest December 500 mb -WPO blocks didn’t have to compete with such a strong Pacific Jet and +EPO

 

 

 

[bncho]

11 minutes ago, Eskimo Joe said:

 

 

thoughts y'all? i'm not saying it'll happen or not i'm just curious and your takes

 

[GaWx]

Today’s Euro Weeklies for week 3+ are still lacking cold domination to return to most of the E US south of the N tier with a solid -PNA dominating through mid Jan along with no -NAO or -AO. If this verifies, it would likely be pretty mild in much of the E US and nothing like we’ve been experiencing the last 2 weeks. However, models the last 3 weeks have been too warm in the E US with too much SER and missing much of the -NAO and -AO. Also, Midwest snowcover is well above avg, there’s the potential lag effects from the 11/28/25 SSWE, and the MJO remains favorable for E US cold. Are the weeklies/models finally getting their act together or are they going to continue with the same errors? Opinions?

[LakePaste25]

30 minutes ago, bluewave said:

I suspect that the issues the models have been having long range are related to the much faster Northern Stream of the Pacifc Jet which continues. It’s not typical to get a strong -WPO +EPO couplet  at the the same time in December. So the shortwaves in the fast Pacific flow are lowering heights over Eastern Alaska while the -WPO ridge stands firm.

At least into mid December the +EPO and stronger Pacific are trying to have the ridge roll out into the Plains while the -WPO would have the ridge axis more in the West. So a tug of war between two competing influences that we normally don’t see at the same time.

My guess is that the ridge eventually comes east at some point during the 2nd half of December as the Pacific Jet eventually wins out in these situations. Notice how the 10 year December strong -WPO composite features a more -EPO and a relaxed Pacific Jet.
 

Much stronger Pacific Jet and unusual +EPO in mid-December for a very strong -WPO block

Past 10 strongest December 500 mb -WPO blocks didn’t have to compete with such a strong Pacific Jet and +EPO

 

 

 

Models have been placing the block too far west, which impacts how much it bleeds into the EPO domain. Take the 11th-14 for example. A week ago, the EPS had a positive EPO for this time period. Now, it has a deeply negative EPO.

 

[EasternLI]

1 hour ago, stadiumwave said:

From Paul Roundy:

"Base state supports Bering Strait and Greenland blocking, with troughing in the eastern US. A fast component of the MJO signal moves through Indian basin to Maritime Continent 15-30 Dec offsetting the cold eastern US signal and potentially forcing a period of warm anomalies in the eastern US."

 

Yeah, that makes sense actually. With the Kelvin wave already discussed constructively interfering with the MC region while it passes through. So a break in the pattern is plausible, potentially. Not set in stone. But I could see that happening. Interesting about the base state favoring -wpo and -nao episodes. Seems any break in the cold wouldn't be long lived under these circumstances. Really interesting year we have here. 

 

[Stormchaserchuck1]

28 minutes ago, bncho said:

thoughts y'all? i'm not saying it'll happen or not i'm just curious and your takes

 

I don't think a warm up will sustain. The Strat warming gives -NAO tendency the last week of Dec and 1st week of January, and I've mentioned this before, but we had some very low N. Hemisphere 500mb lows in the Summer and Fall. Since 2012, that has a really high correlation with following Winter -AO, primarily at 90N. A High pressure at 90N, which I'm going to say is this Winter's tendency, does cool the northern part of the US. 

On the other hand, the weak-negative-ENSO/strong -QBO matches that are working out really well (1989, 2005) did flip to a +EPO pattern in late Dec that lasted all of January. We are following those analogs closely right now, but I do think that 90N High pressure tendency may overcome the sustained warmth that those analogs saw going later into the Winter. It is interesting to see the long range models flip warm though, which happened in those years. 

[qg_omega]

3 hours ago, MJO812 said:

The 12z model runs are once again trending away from a warmup in the long range.  Consistent theme.

Just the opposite

[Cobalt]

9 minutes ago, qg_omega said:

Just the opposite

Still waiting for your very warm post-Thanksgiving pattern to start showing up..

On 11/15/2025 at 10:59 AM, qg_omega said:

Looks very warm in the East starting Thanksgiving week

 

[PhiEaglesfan712]

27 minutes ago, Stormchaserchuck1 said:

On the other hand, the weak-negative-ENSO/strong -QBO matches that are working out really well (1989, 2005) did flip to a +EPO pattern in late Dec that lasted all of January. We are following those analogs closely right now, but I do think that 90N High pressure tendency may overcome the sustained warmth that those analogs saw going later into the Winter. It is interesting to see the long range models flip warm though, which happened in those years. 

The big difference between the 1989 and 2005 analogs is that we got the flip back colder in February 2006. We even got a snowstorm on the 11th-12th. I can see this one happening again (you could even argue that we already did in 20-21).

With 1989, there was no going back to winter once the calendar flipped to 1990. Spring pretty much began in January that year. 89-90 is a once-in-a-lifetime analog that will never happen again. It should be retired.

[MJO812]

[GaWx]

22 minutes ago, MJO812 said:

The questions are whether or not and, if so, how long these same model misses will continue. It isn’t black and white. Nobody knows including you and me.