Dyllan Furness, Director of Communications
In the late 1800s, Peruvian sailors noticed an unusual warming pattern in the waters of the eastern Pacific that would occur around Christmas and bring heavy rains to the region. They named the pattern El Niño, Spanish for The Boy, to honor Jesus.
Today, El Niño is known around the world as an influential climate phenomenon that can lead to droughts in Australia, extreme rainfall in South America, and warm weather on the West Coast of the United States. It also been found to reduce the strength of tropical storms in the Atlantic.
On the heels of a relatively quiet 2025 hurricane season for Florida and the U.S. mainland, attention is turning to what’s ahead. Early indicators point to a strong El Niño starting in summer 2026, which could temper storm activity.
Patrick A. Rafter, Assistant Professor
Patrick Rafter is an oceanographer in the College of Marine Science at the 51. Here he discusses the science behind El Niño, why it’s so difficult to predict, and how it impacts global climate systems, including hurricanes in the Gulf and Atlantic.
Q. To start, what is El Niño-Southern Oscillation (ENSO)?
A. ENSO describes an interannual change in the equatorial Pacific Ocean and atmosphere that occurs every two to seven years.
In so-called “normal” or “neutral” conditions, the trade winds, blowing from east to west, cause upwelling and keep the waters of the eastern equatorial Pacific relatively cool. These cool waters of the eastern equatorial Pacific contrast with the western equatorial Pacific, which is commonly referred to as the “West Pacific Warm Pool,” where upwelling is much weaker and surface waters are very warm. These warm waters exchange their heat with the atmosphere and, through standard atmospheric thermodynamics, ultimately result in a lot more rainfall in the west than in the eastern equatorial Pacific.
The change from neutral conditions to El Niño conditions begins with a reversal of the normal trade wind direction. Instead of the easterly trade winds, there begins to be westerly winds. This change in the normal equatorial Pacific air-sea conditions is called an El Niño event and results in the reversal the east-west surface ocean conditions, in some cases greatly warming the eastern surface ocean. This is a big adjustment to the tropical atmosphere and ENSO variability influences other parts of the planet. This influence is called a “teleconnection.”
Q. El Niño events are notoriously difficult to predict. Why is that?
A. First, while we understand the sequence of events that leads to an El Niño event — beginning with the trade wind reversal in the west Pacific Warm Pool — we don’t understand the precursors to this wind anomaly. This is one of the fundamental outstanding mysteries about ENSO, along with how ENSO will change with increasing greenhouse gases and global warming. So, that is the core reason why they are difficult to predict.
With respect to predicting ENSO conditions for the rest of 2026, even though there are a few signs that an El Niño is likely to occur later this year, we also must consider “The Spring Predictability Barrier” (Lai et al. 2018). In short, our ENSO predicting skills are reduced from March-May. That said, we are seeing some signs of the trade winds reversing in the West Pacific Warm Pool.
Q. Recognizing that this phenomenon occurs over the Pacific Ocean, how does it impact weather and climate in other parts of the world?
A. This is very region specific, but El Niño events have the most dramatic and straight-forward impacts on lands near the tropical Pacific Ocean, because of the shift in precipitation like I mentioned for Peru, but also for the islands in the western tropical Pacific. NOAA has some simple cartoons that make broad brush global predictions about impacts from a given ENSO-state, but I personally think it’s much more complicated than that!
Q. What influence does an El Niño have on the development of hurricanes in the Gulf and Atlantic?
A. One of the global predictions about El Nino events is that, through atmospheric teleconnections, they are able to influence winds and weather in other parts of the world. For example, it’s been widely found that El Nino events drives stronger upper level “vertical wind shear” in the tropical North Atlantic. Hurricanes need very specific conditions to grow and these upper-level winds largely inhibit the formation of tropical Atlantic hurricanes. Statistically, if there is an El Niño event this summer, the expectation is that there will be fewer named storms. But you never know how it will all play out. I’m not in the prediction business!
Q. Headlines have stated that we may see the emergence of an exceptionally strong, “super” El Niño this summer. What factors are driving this prediction?
A. The data and observations being put into the predictive models have given a wide range of possible events, from ENSO-neutral to strong El Niño conditions starting summer 2026. The possibility for El Niño comes from observations that include the appearance of westerly winds in the furthest western West Pacific Warm Pool at 165°E on the equator. We are also observing warming in the subsurface equatorial Pacific that often is a precursor for the eastern surface warming.
These are important observations that suggest there might be an El Niño and given that these values are slightly higher than usual, the El Niño might also be stronger than usual. But there are a lot of “buts” here!
First, while there are some westerly wind bursts at 165°E in the West Pacific Warm Pool, we are not seeing as much immediately to the east (at 180°E). It could be in the process of ramping up, but we don’t know yet. Second, the historical data tells us that March-May are the least skillful times for predicting ENSO conditions later in the year — that is, the “Spring Barrier” for skillful predictions has not been overcome — so I am personally waiting until we move into June before getting too excited about an El Niño event this year, weak or strong.