Weekly El Nino update, and a look at factors that could alter the winter pattern.

 

El Nino Southern Oscillation (ENSO) update.

This update will go into detail on the current El Nino; as well as try to go into differences in the global setup.  It will also be an important precursor to the start of the official winter outlook next month.

We already know we’re in a strong to very strong El Nino. I and most outlets have been talking about it for several months. Everyone is gushing over this El Nino.  They make it seem the world is doomed. I’ve been trying to stick to the facts about what’s going on and what it means. But as I’ve been saying El Nino isn’t the only game in town, when it comes to long term impacts.

We’re already seeing northern parts of the Northern Hemisphere changing as winter gets closer. When it comes to this El Nino we’re going to have to see how the stratosphere continues to evolve.  As I said in the Friday post, the El Nino has already had a profound impact on the Atlantic Hurricane Season, it is truly considerable and historic.  

Current Conditions.   

 

Nino region temperatures as of today

The Nino region SST departures were, Nino at 4 0.1 °C, Nino 3.4 at 2.0°C, Nino 3 at 2.8°C and Nino 1+2 was at 3.7°C.

 Last week's Nino region temperatures

The Nino region SST departures were, Nino at 4 0.1 °C, Nino 3 .4 at 1.8°C, Nino 3 at 2.7°C and Nino 1+2 was at 3.9°C.

 Subsurface water temperatures

 

There is a very deep pool of warmer-than-normal water down to around 500 feet of ocean depth.

The deep water is around 10 °C to 11°C warmer than the long-term average! This is one of the major reasons CPC has the El Nino projected to strengthen.

 Other Teleconnections

There are a number of atmospheric oscillations that are important drivers of week-to-week weather patterns across North America. The Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO) often get the most attention, but two other important pattern oscillations for North America are the Eastern Pacific Oscillation (EPO) and the Western Pacific Oscillation (WPO).

AO:

During the positive phase, the jet stream stays farther north, and mid-latitude winters are milder than usual. During the negative phase, the jet stream dips into the mid-latitudes, creating cold-air outbreaks.

NAO:

A positive NAO index favors mild winters in the eastern U.S. Negative values increased chances for stronger cold-air outbreaks and increased storminess in the eastern U.S.

EPO:

Positive EPO phase: Lower heights in the north and higher heights in the south, typically associated with warmer conditions across central and eastern North America.

Winter: Negative EPO phases are linked to cold outbreaks and Arctic air intrusions, while positive phases favor milder, warmer conditions

When the EPO is in a positive phase, mild Pacific air flows straight into the West Coast of North America. While such a pattern can bring significant rain and snow to the western portions of the country, the air flow warms and dries as it descends down the eastern slope of the Rockies. This results in a warmer than normal pattern across most of the central and eastern portions of the U.S. and southern Canada, particularly during the winter season.

Right now, the EPO is in its negative phase, which is influencing U.S. weather with warmer, drier conditions in the Southwest and more rain in the Northwest, while also creating conditions that can bring cold air outbreaks into the central and eastern U.S. in winter

WPO:

When the WPO is in a positive phase we tend to see warmer-than- average conditions in the North and East. This also results in cooler-than- average winters in the Rockies and West and warmer than average winters in the East, there is also increased precipitation in the Plains and East. When the WPO is in a negative phase we tend to see cooler-than-normal conditions in the North and East. This also results in warmer-than-average winters in the West and Southwest., there is also Reduced precipitation in the Plains and South

All of these teleconnections can transition between positive and negative phases within a few days or weeks, which means long range forecasting and projection is extremely difficult. But they have a big impact on seasonal variability, especially at the local level. So, they will be wild cards from week to week.

The next graphic shows CPC’s official forecast over the next year. The solid blue line in the middle is the current accepted forecast peaking at 2.7 degrees C around December. You can also see some ranges of possible outcomes. The color shading shows the forecast ranges, with the darkest color shading indicating that there is a 50% chance that the forecasted RONI values will remain between the RONI values displayed. There is a 90% chance that forecasted RONI values will remain between the upper and lower edges of the lightest color shading. The middle color shade provides the RONI forecast range with a 70% chance. If you look at the top temperature possibility, it’s now 3.3 °C above normal.

 

 The CPC says the El Nino looks to remain at 2.0 °C or higher through winter 2026-2027.

Low-level westerly wind anomalies and upper-level easterly wind anomalies extended from the western to the east-central equatorial Pacific. Enhanced convection and rainfall persisted from the central to the eastern Pacific, while anomalies remained suppressed over Indonesia.

  

The Southern Oscillation Index is the oldest ENSO measurement still in daily use — and the atmosphere's vote on what the ocean is doing. It compares surface air pressure at two stations that bracket the tropical Pacific: Tahiti in the east-central basin and Darwin on Australia's north coast. The standardized difference (Tahiti minus Darwin) is the SOI.

Sustained positive values of the SOI above +7 typically indicate La Nina and represent lower than average MSLP at Darwin and/or higher than average MSLP at Tahiti. Sustained negative values below −7 typically indicate El Nino, and higher than average MSLP at Darwin and/or lower than average MSLP at Tahiti.

 

The traditional and equatorial Southern Oscillation indices remained negative.

 

All of this is saying that the coupled ocean-atmosphere system reflects a strengthening El Nino.

  

Difference in the global setup!

There is no doubt that we’re in a strong east based El Nino, +Quasi-Biennial Oscillation (QBO), + Atlantic Multidecadal Oscillation (AMO) and a +Pacific Meridional Mode (PMM). Not only does this flood the CONUS with a lot of mild air. It also means the subtropical jet is going to be very strong and active this fall and winter. Storms coming ashore and running along the deep south, with big storms along the East and West Coasts

We also have a -Pacific Decadal Oscillation (PDO) with those warmer SST in the northwestern Pacific with the colder than average SST off the West Coast in the north Pacific.  The last 3 super El Nino’s had a +PDO so that could make for unpredictable conditions. 

Then we have those warmer than average SST just south of the Aleutian Islands into the Gulf of Alaska. Could this temperature contrast help make for a stronger northern Polar Jet.

In my post a couple of months ago I talked about how we’re in a negative Atlantic Nina. We know this is the case with those cooler than average SSTs in the eastern equatorial Atlantic. This has aided the El Nino helping with stronger than normal trade winds over the equatorial Atlantic, and dryer conditions in the Gulf. Which is why the season has been so quiet, in spite of being in a +AMO (which is typically associated with an active Atlantic hurricane season).

What about global temperatures. 

Currently, nearly the entire tropical and Northern Pacific Ocean is warmer than average. That could alter some of El Nino’s effects by influencing weather patterns.

We are in a warming climate, unlike past super El Ninos, which were driven purely by natural ocean-atmosphere dynamics, this one is occurring on a warmer baseline due to the warming climate. The oceans hold over 98% of the energy available to the atmosphere/ocean system. So, in theory the same SST anomalies produce stronger and more rapid atmospheric responses. In some respects, global warming makes this El Nino a wild card, since it will occur in a far warmer world than that of 2015-16 and 1997-98 — and especially 1982-83. A study published in January found that the typical impacts of El Nino in 2023-24 were offset by the profusion of warm water elsewhere in the global oceans. Each of the Super El Ninos set a new global baseline. So, the classic El Nino signal is riding on top of an ever-warmer world. That has to make a difference in El Nino impacts.

The study, published in Geophysical Research Letters, researchers put this to the test. They analyzed 13 state-of-the-art climate models that simulate intense eastern Pacific El Niño events well. Each model was run under different warming levels (for example, +2°C or +3.5°C), and the team identified extreme events caused by very large rainfall surges in the eastern tropical Pacific. They then averaged the surface and atmospheric patterns for moderate versus intense El Nino winters at each warming level. The models showed El Nino loses its punch in a warmer world.

In the simulations, the characteristic North American impacts of an extreme El Nino event shift significantly, moving 20–30 degrees farther east and weakening by roughly one-third with +3.5°C warming. This indicates that regions like California and Florida, typically accustomed to heavy rainfall during strong El Ninos, would experience considerably less of the usual deluge. Simultaneously, the northeastern US would lose much of its characteristic winter warmth.  The study showed that, Super El Nino teleconnections shift even farther eastward, weaken, and develop a negative North Atlantic Oscillation–like response, echoing the changes seen in moderate El Nino–Southern Oscillation phases." These profound shifts are consistent with climate model predictions of eastward migration in tropical convection and jet-stream patterns. This would mean an increase in storminess with the storms generally being weaker.  So, the bottom line is this current El Nino might not be the blockbuster weather event people expect. It will be interesting to see the results when the Current El Nino is over.

 Conclusion

El Nino has a chance of becoming one of the strongest since at least 1950. The data shows that we’re in a strong to very strong El Nino.  The tropical Pacific Ocean and the atmosphere are looking and acting like they are completely coupled El Nino the winds above the Pacific are shifting, the ocean is releasing stored-up heat, and a cascade of effects on rain, droughts and wildfires could be on its way. NOAA is giving this El Nino an over 90% chance of staying at least strong, over the course of winter 2026-2027.

This EL Nino has several things that are radically different than past strong to super El Ninos. This means the 2026–2027 Winter Could Look Very Different from what we’ve seen before. It will be highly unpredictable and could surprise a lot of people expecting a certain outcome.  Regions like the Northeast and Middle Atlantic very well could see conditions that are radically different from past strong El Ninos. The Northeast could end up cooler and wetter than is expected. All of this will make coming up with a winter outlook, very changeling.  

As I said in the beginning, this post will set the stage for the winter outlook coming out next month. I’ve tried to outline all the major points that will go into the outlook. If you learned something and liked what you read, let others know about it. 

That’s it for this week's El Nino update.