Long-Range Fall & Winter Trends — El Niño News

Update on Wednesday, August 12th, 2026 @ 5 PM

El Niño continues to build, and some of the latest seasonal model guidance is forecasting extraordinary ocean temperature anomalies by late fall and early winter.

Both the ECMWF and CFSv2 ensembles are forecasting Niño 3.4 anomalies reaching around +4°C or higher near the peak of the event, with individual CFSv2 ensemble members approaching +4.5°C or higher.

Farther east in the tropical Pacific, some CFSv2 Niño 1+2 ensemble members are approaching +5°C during November and December. Those are extreme numbers, and if anything close to them verifies, this El Niño would be among the strongest we’ve seen.

An Eastern-Based El Niño

One thing that continues to stand out is how strong the warming is across the eastern equatorial Pacific.

The Niño 1+2 region, located closest to the South American coast, has already experienced exceptional warming, while the warming continues to expand westward through Niño 3 and Niño 3.4.

The latest EPS & CFSv2 forecasts continue to show tremendous warmth in the eastern tropical Pacific into late fall, supporting the idea that we’re dealing with a strongly eastern-based El Niño.

At the same time, we need to remember that today’s tropical oceans are warmer than they were during many of the historic El Niño events we use for comparison.

That makes it more complicated to directly compare the absolute Niño numbers from this event with those from past events.

While these model numbers are extraordinary, the ultimate question isn’t simply how warm Niño 3.4 becomes.

What matters for California and for our winter snow season in the Sierra is how the atmosphere responds to all that warm water. 

What Does This Mean for Mammoth over the next 3 months? 

I’m still expecting above-average precipitation across the region during August and September. That doesn’t necessarily mean large amounts of rain, but rather periods of precipitation from thunderstorms.

If an Eastern Pacific hurricane gets pulled north at some point, things could potentially get very wet, as we saw in late August of 2023.

Historically, El Niño hasn’t been much of a precipitation driver for us during October and November, and in some El Niño winters the more active California storm pattern doesn’t really get going until later in December.

There is, however, one wildcard I’ll be watching closely as we get into the second half of October and early November: a recurving western Pacific typhoon getting caught up in the mid-latitude flow.

A recurving typhoon can inject a tremendous amount of heat and moisture into the North Pacific pattern, helping amplify the downstream jet stream and ridge/trough pattern.

If the timing and positioning line up correctly, that energy can contribute to a significant pattern change downstream several days later, potentially opening the door for an early-season storm into California and the Sierra.

That doesn’t mean a typhoon recurving in the western Pacific automatically gives Mammoth a storm, far from it. The location of the recurvature, interaction with the jet stream, and subsequent evolution across the North Pacific all have to line up correctly.

During a year with this much going on across the tropical Pacific, a late October or early November recurving typhoon is one of the wildcards I’ll be watching for as a possible trigger for our first significant early-season Sierra storm.

Outside of something like that developing, I wouldn’t expect the main El Niño-driven winter pattern to necessarily show its hand during October or November.

That’s something Ted and I will be watching closely as we move through the fall.

The Winter Signal Is Getting Hard to Ignore

The bigger question is what this potentially historic El Niño will mean for California weather during the winter of 2026–2027.

This is where the latest data becomes particularly interesting.

The August ECMWF seasonal ensemble is showing an exceptionally strong wet signal across California for December, January, and February.

The model is not simply showing an increased chance of above-average precipitation.  It is showing 70–100% probabilities of above-average winter precipitation across much of California, with large portions of the state also showing a 70–100% probability of DJF precipitation finishing among the wettest 20% of ALL recorded winters.

>>> These images IMHO are an extraordinary seasonal signal.

They don’t guarantee that’s what will happen, but when a seasonal ensemble becomes that heavily weighted toward one side of the climatological distribution, it gets my attention and everybody else in the weather industry. 

For the Sierra Crest and Eastern Sierra, I’m continuing to lean toward well above average precipitation for the upcoming winter.

If California does get wave after wave of precipitation, the next big question is what will the snow levels end up being?

The reality is snow levels are going to be an issue at times. Of all the ski areas in California, Mammoth and its high elevation should do well at times.

Skiers, get yourself some fat powder skis as a lot of the snow is going to be heavy if this all pans out.  

With all that said, there is still a Bust Scenario

We’ve all seen promising long-range winter forecasts fall apart before, and I’m not ignoring that possibility. 

Even with everything I’m seeing right now, I’m leaving about a 30% chance that this does not work out the way the models are currently advertising.

The Pacific Ocean can give us all the right signals, but ultimately the atmosphere has to respond.

The location of the jet stream, blocking patterns across the North Pacific, storm trajectories, and the timing of individual atmospheric river events will ultimately determine what happens here in the Sierra.

We could get to spring wondering what happened.

But that also means I’m currently putting roughly a 70% chance on a wetter than average winter for the Sierra. That’s a pretty strong call this far out, and it’s based on how many different pieces of the puzzle are lining up in the same direction right now.

There is plenty of time for this forecast to change.

We’re still months away from winter, and these seasonal models will continue to evolve as we move through late summer and fall.

But I’ve never seen the models showing an El Niño signal quite like what we’re looking at right now.

I was telling my wife over coffee this morning that this could end up being the biggest winter ever — or the biggest bust ever.

We’re moving into largely uncharted waters, and it’s going to be fascinating watching how all of this unfolds over the next 6–8 months.

I’ll continue following the El Niño data, Pacific Ocean temperatures, seasonal model trends and, most importantly, signs that the atmosphere is actually beginning to respond to what is happening in the tropical Pacific.

We will have an updated El Nino / Winter Outlook post in about a month to see how things are progressing.

Steve Taylor — The Snowman