2025-2026 ENSO

[snowman19]

17 minutes ago, Stormchaserchuck1 said:

You don't do well in ++NAO/-PNA either

We may have to wait until the 2nd half of December for snowfall. 

If Paul Roundy is correct, the 2nd half of December is going to have more -PNA/RNA than the 1st half

[bluewave]

On 11/21/2025 at 11:43 AM, 40/70 Benchmark said:

This probably ties into the rule concerning the higher amplitude MJO waves in October preceding colder winters that @bluewavehas referenced, though I know that is a more recent phenomenon. I do wonder if those seasons were higher amplitude in October. Looks like 2010 would fit the mold...not so much 2005 and 2000. 

It’s good that all of us using different methods had a weaker PNA for this December than the record +PNA La Niña mismatch last December following the stronger amplitude MJO 5 over +2.70 in October 2024. 

[snowman19]

5 hours ago, 40/70 Benchmark said:

Yea, I said back to approaching climo by Xmas week, and that run reflects that.

Yes. You went against the grain and said weeks ago that you thought the November stratospheric warming was going to be a weaker wave reflection event and the SPV was going to rebound and strengthen quickly again mid-late December. If that works out, then it will have been a very impressive call

[MJO812]

1 hour ago, bluewave said:

The more +NAO following the wave reflection in concert with the stronger Maritime Continent forcing will both act to enhance the Southeast ridge as we had into December. Remember, the original forecasts for the first week of December didn’t have any Southeast ridge. Models regularly underestimate the Southeast ridge influence in the long range. Either through the 5 day means or with the storm track which amplifies the Southeast ridge on the days of the storms. 
 

New EPS December 1-8 forecast

Old EPS December 1-8 EPS forecast

 

 

The models are really struggling. Thanksgiving and its weekend warmup went poof so is the week 1 warmup which consists of plus 20 day skewing the entire week 

Here's another warm bust in the making 

 

[MJO812]

The 1st week of December does look mild though.  Delayed but not denied ?

Im going to remain patient. The Nina is dying and the MJO is going to go into 7/8 and most likely 1.

[EastonSN+]

2 hours ago, Stormchaserchuck1 said:

You don't do well in ++NAO/-PNA either

We may have to wait until the 2nd half of December for snowfall. 

Yeah unfortunately the RNA creates a SE ridge, and without blocking can facilitate cutters. 

This really feels like the old fashioned warm wet, cold dry years of the past. Last year we had plenty of cold but remained dry.

 

 

[EastonSN+]

2000 through 2018 was dominated by a positive PNA pattern which created troughing in the east the majority of the time. 

Unfortunately this has flipped to predominantly negative since 2018, hence more east coast ridge. We will get back to a positive PNA multi year pattern at some point. Just have to be patient.

[donsutherland1]

The CFSv2 has now moved into the early stages of its skillful range. Its monthly forecast for December is below. 

I assessed this idea against the currently expected state of the teleconnections. ENSO was omitted, as the sample size became so small that is was useless (n=2).

Based on the expected predominant state of the teleconnections for December (WPO-/EPO-/PNA- and AO neutral) it appears reasonable. The AO should start negative but could go positive as December progresses based on the current guidance. The second half outcome will depend on whether or not the stratospheric warming event propagates to the troposphere to  promote a redevelopment or persistence of AO blocking. So, for purposes of conservatism, I treated the AO as neutral (monthly average above -0.50 but below +0.50)  for looking at the monthly CFSv2 idea.

Should an AO+ regime develop (SSW fails to propagate in a fashion that promotes AO blocking), warm anomalies could cover much of the Eastern Seaboard with the exception of central or northern New England and have the risk of spreading into at least the Ohio Valley and perhaps farther westward depending on the strength of the AO+. For now, this is an identified risk, but not the most likely outcome.

On the other hand, should strong AO blocking develop, most of the eastern half of the U.S. would likely see cold anomalies. This scenario would also have the highest probability of seeing a strong Arctic outbreak reach the East Coast. Given the present guidance, this seems to be less likely than an earlier breakdown of the AO-. But the stratospheric warming event is a wildcard and how such events ultimately play out over long timeframes is not a high-skill undertaking.

It should also be noted that teleconnections cannot be forecast skillfully beyond 10-14 days. 

All in all, the combination of the CFSv2 and teleconnections highlights the Great Lakes Region and Upper Midwest as having the greatest probability of experiencing cold anomalies. They also highlight the Great Lakes Region as having the highest probability of above normal monthly snowfall. 

As for my thinking using the framework I illustrated yesterday, I've highlighted what has changed in my thinking overnight in blue. The emergence of a neutral AO on the guidance was noted (there's a very large spread among the ensemble members).

No changes were made beyond December 10 as signals remain mixed and there remains no clear signal for a change. 

[MJO812]

36 minutes ago, EastonSN+ said:

Yeah unfortunately the RNA creates a SE ridge, and without blocking can facilitate cutters. 

This really feels like the old fashioned warm wet, cold dry years of the past. Last year we had plenty of cold but remained dry.

 

 

All the ensembles bring down the cold after the first week.  No clue what the panic is right now.

[michsnowfreak]

44 minutes ago, MJO812 said:

All the ensembles bring down the cold after the first week.  No clue what the panic is right now.

People post from different regions so different effects are expected. Plus the select group of posters who always/only look for warm will be looking and scouring social media for whatever they need to to mitigate any cold. But overall appears that in typical nina fashion, the already cold north will have colder anomalies and the already warm south warmer ones. In other words big temp gradients, at least at times.

[stadiumwave]

https://x.com/judah47/status/1992608265507946858?t=ykLy8c-MkGuGLusD9eZevQ&s=19