2025-2026 ENSO

[mitchnick]

Updated Euro seasonal out. DJF cooler than last run fwiw.

[mitchnick]

Here's a link to all the seasonal Euro if interested. 

https://charts.ecmwf.int/?facets={"Product type"%3A["Experimental%3A AIFS"]%2C"Parameters"%3A[]%2C"Type"%3A[]%2C"Range"%3A["Seasonal"]}

[mitchnick]

Comparison to this year's 500mb anomaly forecast for DJF and last year (bottom)

[GaWx]

1 hour ago, mitchnick said:

Updated Euro seasonal out. DJF cooler than last run fwiw.

Thanks, Mitch.

 Of the 6 La Niña Nov forecasts for winter still available at the website, 2025-6 is the second coldest in the E US:

2025-6:

 

2024-5: significantly warmer than 2025-6 (verified much too warm in E US)

 

2022-3: moderately warmer than 2025-6 (verified not warm enough)

 

2021-2: slightly warmer than 2025-6 (verified slightly too warm)

 

2020-1: significantly warmer than 2025-6 (verified significantly too warm)

 

2017-8: significantly colder than 2025-6 (verified well)

So, regarding the 5 prior Nov Euro La Niña E US winter forecasts, 3 verified too warm, 1 verified well, and 1 verified too cold. In the aggregate, they averaged 1-1.5F too warm in the NE US and ~1F too warm in the SE US. That means that the bias-corrected Nov NE US forecast for winter would probably be near normal with the SE US being only ~1F warmer than normal.

[snowman19]

1 hour ago, 40/70 Benchmark said:

Second year Nina seasons don't necessarily have to be awful, though...71-72, 08-09...

I wasn’t insinuating that 2nd year Nina’s are bad. It’s 3rd year triple dip Nina’s that tend to be bad. As far as the IOD I would not say it’s voodoo. Definitely not voodoo like the October Siberian snowcover debacle at least 

[40/70 Benchmark]

Enter Bluewave with the modled Pac jet being the storngest of the past several on the Euro seasonal

"We'll have to see if the temp composites adjust to account for that as they have the last 7 years in this new, warmer climate".

[40/70 Benchmark]

12 minutes ago, snowman19 said:

I wasn’t insinuating that 2nd year Nina’s are bad. It’s 3rd year triple dip Nina’s that tend to be bad. As far as the IOD I would not say it’s voodoo. Definitely not voodoo like the October Siberian snowcover debacle at least 

2000-2001 was great for the interior NE, but yea....nothing is absolute.

[snowman19]

42 minutes ago, GaWx said:

Thanks, Mitch.

 Of the 6 La Niña Nov forecasts for winter still available at the website, 2025-6 is the second coldest in the E US:

2025-6:

 

2024-5: significantly warmer than 2025-6 (verified much too warm in E US)

 

2022-3: moderately warmer than 2025-6 (verified not warm enough)

 

2021-2: slightly warmer than 2025-6 (verified slightly too warm)

 

2020-1: significantly warmer than 2025-6 (verified significantly too warm)

 

2017-8: significantly colder than 2025-6 (verified well)

So, regarding the 5 prior Nov Euro La Niña E US winter forecasts, 3 verified too warm, 1 verified well, and 1 verified too cold. In the aggregate, they averaged 1-1.5F too warm in the NE US and ~1F too warm in the SE US. That means that the bias-corrected Nov NE US forecast for winter would probably be near normal with the SE US being only ~1F warmer than normal.

Verbatim it looks like a classic canonical “front-loaded” La Niña progression

[bluewave]

23 minutes ago, 40/70 Benchmark said:

Enter Bluewave with the modled Pac jet being the storngest of the past several on the Euro seasonal

"We'll have to see if the temp composites adjust to account for that as they have the last 7 years in this new, warmer climate".

The Euro seasonal tends to have more skill for its summer forecasts than during the winters. We have had several recent summer forecasts that did OK. But it doesn’t really do too well with the winter forecasts. Probably just too many interacting variables during the winter to figure out.

The EPS skill level falls off markedly between week 1 and week 2 at most points during the year. Occasionally, it does very well week 3 and beyond like the forecasts for March 2012.

Last winter the EPS exhibited several biases which it also has over the years. First, it completely missed the mid to late December EPO reversal from the forecasts near the start of December.

I was pointing out early on how the Pacific Jet was being underestimated which turned out to be correct. So it had to play catch up with the big jet extension in mid to late December which lead to the warm up and strong +EPO vortex.

Our recent pattern of the warm up between December 17th and 25th worked out like every December since 2011.

During February I was pointing out early on that it was probably underestimating the Southeast ridge which is another bias. So the heavy snowfall axis it was forecasting closer to NYC wound up further north than earlier in the month. Toronto would up to be the big winner as we got our first February Southeast ridge link up with a 5 sigma Greenland block. 

 

[40/70 Benchmark]

14 minutes ago, bluewave said:

The Euro seasonal tends to have more skill for its summer forecasts than during the winters. We have had several recent summer forecasts that did OK. But it doesn’t really do too well with the winter forecasts. Probably just too many interacting variables during the winter to figure out.

The EPS skill level falls off markedly between week 1 and week 2 at most points during the year. Occasionally, it does very well week 3 and beyond like the forecasts for March 2012.

Last winter the EPS exhibited several biases which it also has over the years. First, it completely missed the mid to late December EPO reversal from the forecasts near the start of December.

I was pointing out early on how the Pacific Jet was being underestimated which turned out to be correct. So it had to play catch up with the big jet extension in mid to late December which lead to the warm up and strong +EPO vortex.

Our recent pattern of the warm up between December 17th and 25th worked out like every December since 2011.

During February I was pointing out early on that it was probably underestimating the Southeast ridge which is another bias. So the heavy snowfall axis it was forecasting closer to NYC wound up further north than earlier in the month. Toronto would up to be the big winner as we got our first February Southeast ridge link up with a 5 sigma Greenland block. 

 

Just poking fun....I don't mean to imply there is no truth to it; I know you don't make stuff up.

[40/70 Benchmark]

18 minutes ago, snowman19 said:

Verbatim it looks like a classic canonical “front-loaded” La Niña progression

The back half will depend on the strat....look at al of the big 2nd half cool ENSO seasons...just about everyone was strat induced.

[snowman19]

17 minutes ago, 40/70 Benchmark said:

The back half will depend on the strat....look at al of the big 2nd half cool ENSO seasons...just about everyone was strat induced.

Agreed. Unless we see a major SSWE and SPV destruction or close to it, I don’t see how we avoid a canonical La Niña mid-late January and especially February and March

[40/70 Benchmark]

3 minutes ago, snowman19 said:

Agreed. Unless we see a major SSWE and SPV destruction or close to it, I don’t see how we avoid a canonical La Niña mid-late January and especially February and March

I think January will have a considerable period of +TNH, but likely outweighted by a Pac jet dominated torch prior.

[mitchnick]

18 minutes ago, 40/70 Benchmark said:

The back half will depend on the strat....look at al of the big 2nd half cool ENSO seasons...just about everyone was strat induced.

Yeah. I suspect the new forecast came in cooler thanks to what is showing up in the extended forecasts for December. Unless we get lucky with the strat as you said, the Niña totally collapses into something like a weak Niño, or just plain luck, I'm already brushing up on my 4-letter word vocabulary for February. 

[GaWx]

56 minutes ago, snowman19 said:

Verbatim it looks like a classic canonical “front-loaded” La Niña progression

 I agree. There’d be nothing bad about “front-loaded”. A “front-loaded” near normal DJF averaged out with colder than normal Dec-Jan 15th/warmer than normal Jan 16th-Feb would be much better than a “no-loaded” warmer than normal DJF. And Febs have been mild for awhile when averaged out (though with variations year to year) regardless…so mild Feb kind of expected in La Niña.

[40/70 Benchmark]

17 minutes ago, mitchnick said:

Yeah. I suspect the new forecast came in cooler thanks to what is showing up in the extended forecasts for December. Unless we get lucky with the strat as you said, the Niña totally collapses into something like a weak Niño, or just plain luck, I'm already brushing up on my 4-letter word vocabulary for February. 

Odds are the strat would only save New England for he second half, not the mid atl.

[jm1220]

59 minutes ago, 40/70 Benchmark said:

Just poking fun....I don't mean to imply there is no truth to it; I know you don't make stuff up.

I want for him to be wrong too but unfortunately the laws of physics and reality couldn’t care less about what we want. 

[stadiumwave]

2 hours ago, mitchnick said:

Comparison to this year's 500mb anomaly forecast for DJF and last year (bottom)

 

Similar on PAC side but 25-26 forecast has more Atlantic blocking. 

Last year Euro had blocking too far west & totally missed Atlantic side blocking 

[40/70 Benchmark]

14 minutes ago, jm1220 said:

I want for him to be wrong too but unfortunately the laws of physics and reality couldn’t care less about what we want. 

My honest opinion that he exagerates some of this stuff moving forwards, but to be fair to him, the jury is still out.

[snowman19]

36 minutes ago, stadiumwave said:

 

Similar on PAC side but 25-26 forecast has more Atlantic blocking. 

Last year Euro had blocking too far west & totally missed Atlantic side blocking 

It’s showing an east-based -NAO for December