2025-2026 ENSO

[winter_warlock]

23 hours ago, 40/70 Benchmark said:

I'll be pretty suprised if we don't see at least one round of significant blocking.

Blocking would be nice but we've had  blocking many times with a perfect set up and still storms missed us.   Sometimes  a strong block can actually keep storms too far south.

[anthonymm]

1 hour ago, 40/70 Benchmark said:

I'm not sure how you interpret my composites in that manner. It's not a KU cookbook, no....ah, you live in Jersey, so maybe.

Any warm anomaly at all is extremely bad news for snow south of Connecticut.

[MJO812]

46 minutes ago, anthonymm said:

Any warm anomaly at all is extremely bad news for snow south of Connecticut.

I haven't seen one bad winter outlook yet for the east coast. Hopefully that holds.

[chris21]

1 hour ago, anthonymm said:

Any warm anomaly at all is extremely bad news for snow south of Connecticut.

For the coastal plain/piedmont that is true. At my location in extreme NW NC at 4000 feet, we have had many above normal snow years in warm winters. We average at least 45 inches and approximately 80 percent of that comes from upslope. We have never had a winter without at least 20 inches of snow here mostly due to the reliability of upslope even in total dud winters.

[anthonymm]

4 minutes ago, chris21 said:

For the coastal plain/piedmont that is true. At my location in extreme NW NC at 4000 feet, we have had many above normal snow years in warm winters. We average at least 45 inches and approximately 80 percent of that comes from upslope. We have never had a winter without at least 20 inches of snow here mostly due to the reliability of upslope even in total dud winters.

Elevation is cheating yes. 

[Maestrobjwa]

8 hours ago, snowman19 said:

The same can be said every year. If this board were around for the 95-96 and 97-98 winters, I’m sure you would have had people saying 95-96 was going to be a warm and snowless winter because of the Niña and on the flip side, I’m sure you would have had the weenies trying to force a cold and snowy winter for the 97-98 super El Niño. There are biases at play every year

And what would you say your bias is?

[bluewave]

8 hours ago, 40/70 Benchmark said:

There are some posters you just know are never going to deliver good news, and if they ever do, it will be measured and delivered with ample caveats. Seem them post....brace first, read later-

You are a very funny guy and appreciate the levity. But it’s been difficult to sustain any wall to wall DJF -EPO -WPO patterns since 2018-2019.

It was much easier to lock in the -EPOs and -WPOs from December to March in 2013 to 2015 when the WPAC was much colder and the jet stream weaker. This allowed the NEPAC blocking to extend through the season since the weaker jet wasn’t constantly lowering heights with repeated shortwaves eroding the ridge from the west.

As long as we have the enormous WPAC warm pool above and below the surface, the gradient between Siberia and the WPAC will drive these faster jet streams and frequent extensions.

So what we are beginning to see now with the big EPO reversal this month is just a microcosm of the larger pattern since 2018-2019. The EPO reversal last year from late November into December was much more impressive. 

It’s actually been easier to sustain the NEPAC blocking during the summers since 2018 than during the winters. My guess is that this is due to the gradient between Siberia and the WPAC being much weaker during the summer. 

November 2024 into December 2024 -EPO couldn’t lock in and the daily +EPO max in late December was more impressive than the -EPO min in late November. Major Jet max and extension sent multiple shortwaves into the EPO domain lowering heights.

2024 11 20 -168.33
2024 11 21 -243.29
2024 11 22 -258.96
2024 11 23 -229.99
2024 11 24 -222.98
2024 11 25 -212.57
2024 11 26 -174.73
2024 11 27 -153.02
2024 11 28 -130.16
2024 11 29 -105.10
2024 11 30  -81.63
2024 12 01  -43.78
2024 12 02  -14.50
2024 12 03  -35.60
2024 12 04  -34.12
2024 12 05  -14.08
2024 12 06   28.23
2024 12 07   49.16
2024 12 08  -27.22
2024 12 09 -137.55
2024 12 10 -149.44
2024 12 11  -49.79
2024 12 12   35.08
2024 12 13   64.11
2024 12 14   70.96
2024 12 15  -21.55
2024 12 16  -72.62
2024 12 17  -59.81
2024 12 18  -48.59
2024 12 19  -98.46
2024 12 20  -88.76
2024 12 21   -9.80
2024 12 22   99.09
2024 12 23  112.77
2024 12 24  186.45
2024 12 25  280.91
2024 12 26  310.29
2024 12 27  225.40
2024 12 28  135.47
2024 12 29   75.67
2024 12 30   11.94

[kazimirkai]

10 hours ago, donsutherland1 said:

With respect to the EPO, the swing from the minimum value during the first half of September to the maximum value (so far) for the second half of September is the fourth largest on record.

All of the prior 10 biggest such cases occurred during the evolution toward either La Niña or Neutral-Cool ENSO winters.

The composite temperature anomalies for the Neutral-Cool ENSO Winters:

The composite temperature anomalies for the La Niña Winters:

However, warmth is not a slam dunk for the Northeast/Great Lakes. Winters 1964-65 and 1970-71 were cold in the Northeast, Great Lakes, and Northern Plains. Winters 2007-08 and 2020-2021 were cold in the Central Plains.

Finally, the sample size is limited to 10 extreme EPO cases. 

 

How can the ENSO cool and La niña composites have completely opposing temperature anomalies in the eastern US? The temperature of the tropics can't have been that different in these two scenarios, why would its effect suddenly reverse? 

[donsutherland1]

4 minutes ago, kazimirkai said:

How can the ENSO cool and La niña composites have completely opposing temperature anomalies in the eastern US? The temperature of the tropics can't have been that different in these two scenarios, why would its effect suddenly reverse? 

Convection during neutral ENSO events is more evenly spread out; during La Niña it's farther west (often but not always in the vicinity of the Maritime Continent); during El Niño, it's located in the cental/eastern Pacific. Depending on how the atmosphere and ocean couple, these differences matter. MJO phases in the Maritime Continent often favor warmth in eastern North America. 

ENSO, of course, is but one variable that shapes seasonal outcomes. Other variables can outweigh it. 

[snowman19]

4 hours ago, Maestrobjwa said:

And what would your bias is?

My bias is not part of this conversation. I know you’re ready to start one of your 5th grade personal attacks 

[40/70 Benchmark]

4 hours ago, bluewave said:

You are a very funny guy and appreciate the levity. But it’s been difficult to sustain any wall to wall DJF -EPO -WPO patterns since 2018-2019.

It was much easier to lock in the -EPOs and -WPOs from December to March in 2013 to 2015 when the WPAC was much colder and the jet stream weaker. This allowed the NEPAC blocking to extend through the season since the weaker jet wasn’t constantly lowering heights with repeated shortwaves eroding the ridge from the west.

As long as we have the enormous WPAC warm pool above and below the surface, the gradient between Siberia and the WPAC will drive these faster jet streams and frequent extensions.

So what we are beginning to see now with the big EPO reversal this month is just a microcosm of the larger pattern since 2018-2019. The EPO reversal last year from late November into December was much more impressive. 

It’s actually been easier to sustain the NEPAC blocking during the summers since 2018 than during the winters. My guess is that this is due to the gradient between Siberia and the WPAC being much weaker during the summer. 

November 2024 into December 2024 -EPO couldn’t lock in and the daily +EPO max in late December was more impressive than the -EPO min in late November. Major Jet max and extension sent multiple shortwaves into the EPO domain lowering heights.

2024 11 20 -168.33
2024 11 21 -243.29
2024 11 22 -258.96
2024 11 23 -229.99
2024 11 24 -222.98
2024 11 25 -212.57
2024 11 26 -174.73
2024 11 27 -153.02
2024 11 28 -130.16
2024 11 29 -105.10
2024 11 30  -81.63
2024 12 01  -43.78
2024 12 02  -14.50
2024 12 03  -35.60
2024 12 04  -34.12
2024 12 05  -14.08
2024 12 06   28.23
2024 12 07   49.16
2024 12 08  -27.22
2024 12 09 -137.55
2024 12 10 -149.44
2024 12 11  -49.79
2024 12 12   35.08
2024 12 13   64.11
2024 12 14   70.96
2024 12 15  -21.55
2024 12 16  -72.62
2024 12 17  -59.81
2024 12 18  -48.59
2024 12 19  -98.46
2024 12 20  -88.76
2024 12 21   -9.80
2024 12 22   99.09
2024 12 23  112.77
2024 12 24  186.45
2024 12 25  280.91
2024 12 26  310.29
2024 12 27  225.40
2024 12 28  135.47
2024 12 29   75.67
2024 12 30   11.94

If you have been reading my blogs, you would know I expect neither wall-to-wall -WPO or -EPO...that said, show me on the doll where the negative modes of those respective teleconnections hurt you? It's okay to mention them....confront these traumatic thought patterns head-on.

[40/70 Benchmark]

7 hours ago, snowman19 said:

The same can be said every year. If this board were around for the 95-96 and 97-98 winters, I’m sure you would have had people saying 95-96 was going to be a warm and snowless winter because of the Niña and on the flip side, I’m sure you would have had the weenies trying to force a cold and snowy winter for the 97-98 super El Niño. There are biases at play every year

A good exercise I like to participate in is "opposite outcome"....give me a few examples of why this season could turn out more favorably from the perspective of snow/cold enthusiasts, than you envision....it helps to guard against preconceived thought processes, which is something we are all guilty of from time to time.

[40/70 Benchmark]

5 hours ago, MJO812 said:

I haven't seen one bad winter outlook yet for the east coast. Hopefully that holds.

Wait 3 weeks before winter and Chris will hook it up.

[brooklynwx99]

13 hours ago, bluewave said:

I think the record cold in Siberia creating the tight gradient between the record SSTs south of the Aleutians is helping this very strong shift to +EPO. This is following a similar pattern of recent years. Currently the Aleutians are experienceing a 4 sigma jet max helping to dig the +EPO trough and pump the warm ridge over North America. So as we have seen in recent years it tough to maintain a -EPO indefinitely. This EPO reversal was among the strongest we have seen from September into October.

in recent years? when has it ever not been tough to maintain a -EPO indefinitely?

[raindancewx]

I'm expecting another fairly shitty season for eastern snowfall overall. Recent culprits are not applicable this season though.

More generally, for those of you who swear by ONI, the Indian Ocean and Atlantic Ocean are relatively cold at the tropical latitudes, so subtracting out their heat as part of global warming doesn't 'enhance' the R portion of the RONI for La Nina strength as in prior recent years. The cold current by Japan looks it has woken up a bit, and the Atlantic and Indian Ocean are both colder relative to last year than the tropical Pacific. The North/South Pacific are moving toward a +PDO slowly as well with the warm C by the eastern side of the basin showing and the cold tongues showing to the west. Colder tropics overall should mean less MJO relevance in the warm and cold phases, less convection for thunderstorms. High solar is typically a modifier on MJO progression east to west/intensity if you look at it.

We also had pretty favorable patterns for sea ice this year, so there should be pretty substantial cold build early on. Last September was pretty cold in Northeast Russia and that cold kept sloshing around until it was forced out of the Arctic in January in a pretty severely cold national pattern for a few weeks. That part of Russia looks pretty cold again this September.

I don't consider the AMO/PDO to have flipped this year. But even 'moving' toward opposite phases should reduce the drought tendencies we've seen in the US over the blue areas. You can see last year was close to the exact opposite of figure A (+PDO/-AMO). We should see a much better/wetter winter nationally with the Atlantic much colder and the NE Pacific so much warmer, especially as the cold tongue begins to assert itself by Japan. In the months/seasons with most direct influence from AMO/PDO on precipitation you should see completely different rain/snow patterns to last year.

Colder AMO should alter Southeast ridge positioning, independent of the type of La Nina that shows. A lot of the storms that went to bring big rains/snows to KY/TN last year should be east/west of their positions last year, with the PDO hurting KY/TN moisture. My main issue for NE snow is that precip patterns nationally usually have specific signatures nationally in the Summer that have not really shown up for 2025. I think the subtropical jet will not cooperate for eastern storms, even though at times the Northern stream of the jet will go pretty far south this winter.

[GaWx]

On 9/21/2025 at 2:36 PM, GaWx said:

 Where is 2025 headed for pre-Oct? Through Gabrielle, the prog is for ~~55. Then there’s the current MDR orange. The consensus has this as TS Humberto by 9/26-7 and a H soon after. That would have a realistic potential of 10-15 ACE 9/26-30. So, that would get total 2025 pre-Oct ACE to as much as ~65-70. That compares to 94 for the 1991-2020 pre-Oct avg, which means 2025 pre-Oct will end up solidly BN just about regardless of what Gabrielle and Humberto do.

What does this tell me? With 2025 almost definitely headed for BN pre-Oct, the chance for a 50+ Oct-Dec is <50%. However, 2024, 2016, and 1963 as well as 3 of the most active 7 Oct-Dec on record having occurred just within the last 6 La Niña seasons also say don’t bet the farm on <50 for Oct-Dec at least as of yet.

Update:

-Season’s ACE is now up to 57.2.

-Gabrielle has exceeded earlier progs and is now on its own progged to get ACE to ~60.

-Humberto has been declared and is progged to add ACE of ~13 through Sept 30th though with lots of uncertainty, including upside to ~17-20.

-That would get ACE to ~73-80.

-But that’s not necessarily all as models are now significantly more bullish on still another TC by late this week from Invest 94L. A great level of uncertainty rests with 94L at this very early stage. The upside limit on that through Sept 30 is ~~10.

-So, current rough projections are significantly higher for ACE as of Sept 30th. In my quoted prog from 3 days ago, I had the upside at 65-70. That upside limit has since risen to ~83-90. That compares to the 1991-2020 average of 94 through Sept. 30. Thus, if this upside range of 83-90 were to verify, Sept 30th ACE could rise all the way to only a little below the active 30 year average!

-Oct-Dec 30 year avg is 28. So, if we were to get to 90 as of Sept 30th, getting to an end of season well over 100 would then be favored along with a reasonable upside of ~130-140 vs 1991-2020 avg of 122. That upside potential is extra realistic because of 

1. mainly favorable MJO progged for next few weeks

2. weak La Niña on RONI basis is correlated most to above avg ACE late season

3. Euro Weeklies are active

@snowman19@PhiEaglesfan712

[Maestrobjwa]

1 hour ago, snowman19 said:

My bias is not part of this conversation. I know you’re ready to start one of your 5th grade personal attacks 

Well you mentioned biases good sir--and believe it or not I'm genuinely curious  And have I ever attacked you personally? I mean me ribbing ya a bit on this isn't serious, I promise

[40/70 Benchmark]

1 hour ago, raindancewx said:

I'm expecting another fairly shitty season for eastern snowfall overall. Recent culprits are not applicable this season though.

More generally, for those of you who swear by ONI, the Indian Ocean and Atlantic Ocean are relatively cold at the tropical latitudes, so subtracting out their heat as part of global warming doesn't 'enhance' the R portion of the RONI for La Nina strength as in prior recent years. The cold current by Japan looks it has woken up a bit, and the Atlantic and Indian Ocean are both colder relative to last year than the tropical Pacific. The North/South Pacific are moving toward a +PDO slowly as well with the warm C by the eastern side of the basin showing and the cold tongues showing to the west. Colder tropics overall should mean less MJO relevance in the warm and cold phases, less convection for thunderstorms. High solar is typically a modifier on MJO progression east to west/intensity if you look at it.

We also had pretty favorable patterns for sea ice this year, so there should be pretty substantial cold build early on. Last September was pretty cold in Northeast Russia and that cold kept sloshing around until it was forced out of the Arctic in January in a pretty severely cold national pattern for a few weeks. That part of Russia looks pretty cold again this September.

I don't consider the AMO/PDO to have flipped this year. But even 'moving' toward opposite phases should reduce the drought tendencies we've seen in the US over the blue areas. You can see last year was close to the exact opposite of figure A (+PDO/-AMO). We should see a much better/wetter winter nationally with the Atlantic much colder and the NE Pacific so much warmer, especially as the cold tongue begins to assert itself by Japan. In the months/seasons with most direct influence from AMO/PDO on precipitation you should see completely different rain/snow patterns to last year.

Colder AMO should alter Southeast ridge positioning, independent of the type of La Nina that shows. A lot of the storms that went to bring big rains/snows to KY/TN last year should be east/west of their positions last year, with the PDO hurting KY/TN moisture. My main issue for NE snow is that precip patterns nationally usually have specific signatures nationally in the Summer that have not really shown up for 2025. I think the subtropical jet will not cooperate for eastern storms, even though at times the Northern stream of the jet will go pretty far south this winter.

I agree with you on the meager STJ and active N stream, but not sure why that necessarily hurts the NORTHeast??......Miller B redevelopments can be fine for New England and upstate NY. Last year was brutal here...all set the with STJ "cooperating" as much as it did last year. I'll take my chances with the N stream over watching Baton Rouge to Nashville getting hit.

[GaWx]

Big news from Australia’s BoM: their model progs have just switched from 3.4 to relative 3.4 (akin to RONI)!

Relative Niño indices

Traditional Niño index values were used at the Bureau of Meteorology until September 2025. From September 2025, the Bureau uses Relative Niño indices, which measure sea surface temperature anomalies in the tropical Pacific Ocean in the Niño regions, but calculated relative to the global tropical region temperature anomaly. This is to relate the indices more closely to the localised processes associated with ENSO, rather than larger-scale tropical SST features such as global warming. 

Example: The Relative Niño3.4 index calculation: 

Relative Niño3.4 = S x [(Niño3.4obs – Niño3.4clim) – (Tropical Meanobs – Tropical Meanclim)]

 Here’s the latest BoM relative 3.4 model prog for Relative 3.4, which has a low of -0.7C for OND:

 

http://www.bom.gov.au/climate/ocean/outlooks/index.shtml?index=nino34#region=NINO34

@snowman19