2025-2026 ENSO

[Terpeast]

It looks like GEFS is trying to loop back into 7/8 after its u-turn into 6. Hovmollers shows this as well.

[MJO812]

28 minutes ago, Terpeast said:

It looks like GEFS is trying to loop back into 7/8 after its u-turn into 6. Hovmollers shows this as well.

The EPS couldn't be more clear about phase 8. Expect the coldest part of December in the 2nd half.

 

[PhiEaglesfan712]

2 hours ago, EastonSN+ said:

Do we know exactly what is causing the warmer WPAC ocean temps (as opposed to any other region like CPAC or EPAC)?

I'm not sure exactly what is causing the warmer WPAC ocean temps. All I know is that something must have happened in between the 2009-10 strong el nino and the 2015-16 super el nino.

[anthonymm]

7 minutes ago, PhiEaglesfan712 said:

I'm not sure exactly what is causing the warmer WPAC ocean temps. All I know is that something must have happened in between the 2009-10 strong el nino and the 2015-16 super el nino.

2009-2010 strong la nina *

[donsutherland1]

6 minutes ago, anthonymm said:

2009-2010 strong la nina *

2009-10 was a strong El Niño. 2010-11 was a strong La Niña.

[EastonSN+]

18 minutes ago, PhiEaglesfan712 said:

I'm not sure exactly what is causing the warmer WPAC ocean temps. All I know is that something must have happened in between the 2009-10 strong el nino and the 2015-16 super el nino.

I don't think we can determine which factor will eventually cool the WPAC until we can pinpoint what is causing it (as opposed to other areas).

[michsnowfreak]

I know things are looking decent when we are seeing embedded tweets in French.

[LakePaste25]

10 minutes ago, EastonSN+ said:

I don't think we can determine which factor will eventually cool the WPAC until we can pinpoint what is causing it (as opposed to other areas).

It is due to climate change. The trade winds unevenly distribute the warmer water to the western pacific. This phenomenon only temporarily bounces back during El Niño years, and doesn’t even fully do this anymore. It’s here to stay. 

[GaWx]

 With the unfavorable changes in the MJO and AO/NAO, today’s 0Z GEFS is not surprisingly significantly warmer than yesterday’s run for the 2nd week in Dec. However, today’s 0Z EPS, which maintained its very long phase 8, is much colder than yesterday as well as the GEFS:

Yesterday’s 0Z EPS for 12/5-11 2m temps:

 

 Today’s 0Z EPS for 12/5-11: it’s pretty rare for a 7 day period of the EPS to have that much of a change within just 24 hours:

 As a result, the aggregate of today’s Euro Weeklies 12/1-7 and 12/8-14 2m temp anomaly maps will very likely be notably colder than yesterday’s.

[GaWx]

1 hour ago, donsutherland1 said:

Yesterday, I noted that the GEFS was trying to push an EPO+, but its forecast 500 mb pattern was profoundly different from any of the December WPO-/EPO+/AO-/PNA- clusters. That suggested that either the teleconnection idea was off or the pattern was off, rather than some novel outcome. 

Overnight and through today's 6z cycle, the GEFS has continued to evolve. It has added a WPO+ to its EPO+ idea and restored its earlier idea of a AO+. It has now joined the Canadian ensembles that keep the MJO out of Phase 8 through its forecast horizon. In short, its previously significant areas of "disconnect" have disappeared overnight. Its forecast pattern is now more consistent with what one would expect.  For now, the GEFS is trying to build a credible milder alternative scenario for the pattern/temperature evolution in North America toward mid-December. 

The EPS has not shifted toward that emerging GEFS idea. Therefore, the baseline idea remains that the northern tier of the U.S. and most of Canada should remain cold toward and probably beyond mid-December. The Southeast could still turn warm despite some shots of colder air.  

Mid-December and beyond is still in the low-skill distant realm. The big story through the weekend will be the significant snowstorm that will affect parts of the Midwest and Great Lakes Region. As a result, Chicago, Detroit, Milwaukee, and Toronto remain on track to experience their snowiest fall in five or more years. As an appetizer, Detroit added 0.1" snowfall yesterday and Toronto picked up 1.2 cm (0.5") yesterday.

Related to this, check out the differences in the means (green) between the +AO of the 0Z GEFS and the slight -AO of the EPS:

GEFS:

 

EPS:

 

[Terpeast]

1 hour ago, donsutherland1 said:

Yesterday, I noted that the GEFS was trying to push an EPO+, but its forecast 500 mb pattern was profoundly different from any of the December WPO-/EPO+/AO-/PNA- clusters. That suggested that either the teleconnection idea was off or the pattern was off, rather than some novel outcome. 

Overnight and through today's 6z cycle, the GEFS has continued to evolve. It has added a WPO+ to its EPO+ idea and restored its earlier idea of a AO+. It has now joined the Canadian ensembles that keep the MJO out of Phase 8 through its forecast horizon. In short, its previously significant areas of "disconnect" have disappeared overnight. Its forecast pattern is now more consistent with what one would expect.  For now, the GEFS is trying to build a credible milder alternative scenario for the pattern/temperature evolution in North America toward mid-December. 

The EPS has not shifted toward that emerging GEFS idea. Therefore, the baseline idea remains that the northern tier of the U.S. and most of Canada should remain cold toward and probably beyond mid-December. The Southeast could still turn warm despite some shots of colder air.  

Mid-December and beyond is still in the low-skill distant realm. The big story through the weekend will be the significant snowstorm that will affect parts of the Midwest and Great Lakes Region. As a result, Chicago, Detroit, Milwaukee, and Toronto remain on track to experience their snowiest fall in five or more years. As an appetizer, Detroit added 0.1" snowfall yesterday and Toronto picked up 1.2 cm (0.5") yesterday.

AIFS ensembles have also been performing well with the polar domain's 500mb patterns, and both it and EPS have been trending less positive with the AO in recent runs. Otoh, GEFS has been verifying better with the MJO. Something to watch for.

[EastonSN+]

39 minutes ago, LakePaste25 said:

It is due to climate change. The trade winds unevenly distribute the warmer water to the western pacific. This phenomenon only temporarily bounces back during El Niño years, and doesn’t even fully do this anymore. It’s here to stay. 

Maybe I need a visual, however, why are the trade winds distributing specifically to the WPAC? Also does that mean the EPAC will remain generally cooler than average due to upwelling?

[Terpeast]

10 minutes ago, Terpeast said:

AIFS ensembles have also been performing well with the polar domain's 500mb patterns, and both it and EPS have been trending less positive with the AO in recent runs. Otoh, GEFS has been verifying better with the MJO. Something to watch for.

Actually, EPS has been catching up with MJO verification in the last week or so. It did horribly when it was in phase 6, but much better once we crossed into 7.