2025-2026 ENSO

[GaWx]

Euro Weeklies 46 day 2m temp anomalies:

11/25 run: NYC and Chicago -3F

 

11/29 run: NYC -6F, Chicago -8F (would be coldest in many years for that period)

 

Euro seasonal winter fcast issued Nov 1st: huge warm bust potential increasing, which could end up like last winter or even worse:

[SnoSki14]

GEFS still the outlier with trough out west leading to much warmer conditions east & ridging. 

Bet snowman loves that 

[GaWx]

11/30 MJO 2 week runs 

11/30 EPS: steady as can be (4th day in a row very similar) phase 8 12/3-14+, which would be the longest phase 8 in 50 years for any winter month!

 

To show how consistent it has been, the EPS had this on 11/27 run, phase 8 12/3-11+:

—————

GEFS 11/30 (not as consistent as EPS, which has been doing better with phase 7 than GEFS): also has phase 8 start Dec 3rd:

 

 

JMA 11/30: phase 8 12/3-10+

[bluewave]

A new tropical oscillation called the TWISO has been recently discovered. So maybe the reason we are getting a strong MJO 6 gradient pattern in early December is somehow related to it being out of phase with the MJO. Plus the split forcing between the Maritime Continent and the Western Hemisphere could also be creating an interference pattern. 
 

Models showing a MJO 6 interference gradient pattern in early December 

 

 

 

 

 

https://www.pnas.org/doi/10.1073/pnas.2511549122

The tropical climate variability is characterized by various oscillations across a range of timescales. Oscillations that imprint the tropical mean state are generally attributed to slow processes, such as the seasonal cycle or interannual variability. Here, we identify a pronounced tropics-wide intraseasonal oscillation (TWISO) in satellite observations and reanalyses. This oscillation, with a period of 30 to 60 d, is evident across multiple variables and involves interactions between convection, radiation, surface fluxes, and large-scale circulation. It is primarily manifested as convective perturbations in the tropical Indo-Pacific warm pool accompanied by oscillations in the large-scale tropical overturning circulation. Here, we examine the relationship between TWISO, the Madden–Julian Oscillation (MJO), and the instability of radiative-convective equilibrium. Certain phases of TWISO coincide with specific phases of the MJO, suggesting a potential connection between the two. However, although the MJO can amplify the oscillation amplitude of TWISO, it is not essential for TWISO to occur. Finally, due to its broad manifestation across the tropics, TWISO potentially exerts widespread influence on tropical weather and climate at regional scales.

 

[donsutherland1]

The 11/30 0z and 6z GEFS has returned to a warmer outlook for much of North America after December 10th. It offers a credible alternative scenario.

I'm still going with the EPS/ECMWF weeklies, as the GEFS has shown inconsistency. Moreover, the size of the rebound in temperatures (December 11-20 vs. December 1-10) would be both extreme and rare. 

Nevertheless, a look at the alternative scenario is still in order as a muted variation is plausible. The GEFS's development of a fairly strong PNA- is the key variable differentiating it from the colder baseline idea shown on the EPS. The latest two cycles of the GEFS show the development of a WPO-/EPO+/AO-/PNA- pattern. The GEFS maps are consistent with the largest cluster for the December 5-15 period (39%) of cases.

WPO-/EPO+/AO-/PNA- Maps (Largest December 5-15 cluster):

500 mb Height Anomalies:

Temperature Anomalies:

GEFS (11/30 6z cycle): Days 11-15:

500 mb Height Anomalies (5-day average):

Temperature anomalies (5-day average):

 

[MJO812]

9 minutes ago, donsutherland1 said:

The 11/30 0z and 6z GEFS has returned to a warmer outlook for much of North America after December 10th. It offers a credible alternative scenario.

I'm still going with the EPS/ECMWF weeklies, as the GEFS has shown inconsistency. Moreover, the size of the rebound in temperatures (December 11-20 vs. December 1-10) would be both extreme and rare. 

Nevertheless, a look at the alternative scenario is still in order as a muted variation is plausible. The GEFS's development of a fairly strong PNA- is the key variable differentiating it from the colder baseline idea shown on the EPS. The latest two cycles of the GEFS show the development of a WPO-/EPO+/AO-/PNA- pattern. The GEFS maps are consistent with the largest cluster for the December 5-15 period (39%) of cases.

WPO-/EPO+/AO-/PNA- Maps (Largest December 5-15 cluster):

500 mb Height Anomalies:

Temperature Anomalies:

GEFS (11/30 6z cycle): Days 11-15:

500 mb Height Anomalies (5-day average):

Temperature anomalies (5-day average):

 

Yep the gefs has been awful

[MJO812]

33 minutes ago, GaWx said:

11/30 MJO 2 week runs 

11/30 EPS: steady as can be (4th day in a row very similar) phase 8 12/3-14+, which would be the longest phase 8 in 50 years for any winter month!

 

To show how consistent it has been, the EPS had this on 11/27 run, phase 8 12/3-11+:

—————

GEFS 11/30 (not as consistent as EPS, which has been doing better with phase 7 than GEFS): also has phase 8 start Dec 3rd:

 

 

JMA 11/30: phase 8 12/3-10+

Looks like we will be in phase 8 all December. Paul Roundy thinks we will be cold through January .

[Terpeast]

5 minutes ago, MJO812 said:

Yep the gefs has been awful

GEFS did well a month ago when the MJO was still in 6. But EPS is now catching up in forecast performance since we went into 7. And don’t sleep on the AIFS ensembles for mid-latitude 500mb at 6-15 days out. It’s been wiping the floor lately. 

[MJO812]

4 minutes ago, Terpeast said:

GEFS did well a month ago when the MJO was still in 6. But EPS is now catching up in forecast performance since we went into 7. And don’t sleep on the AIFS ensembles for mid-latitude 500mb at 6-15 days out. It’s been wiping the floor lately. 

AI is still a work in progress but it has been doing well.