As one of the main drivers behind seasonal climate patterns, the El Niño-Southern Oscillation (ENSO) is inextricably linked with hurricanes. After last year’s La Niña surprises, this year’s concern focused on the (long-expected) arrival of La Niña conditions in 2025. This change raises new questions about how ENSO will affect what is expected to be a busy hurricane season. It further draws attention to the broader impacts of chronic climate change on these acute climate patterns.
ENSO is shorthand for enso, or El Niño-Southern Oscillation, a set of regular sea temperature and air pressure shifts across the Pacific. All of these alterations have massive effects on weather across the world, especially in winter when ENSO conditions usually develop. As spring comes nearer, these clues tend to disappear with them, rendering accurate predictions difficult.
Climate scientists look very carefully at shifts in global mean surface temperature (GMST). When these temperatures move by 0.9 degrees Fahrenheit (0.5 degrees Celsius) over five overlapping three-month periods, it indicates that either El Niño or La Niña is likely to begin. El Niño usually creates more vertical wind shear, a force that tears apart the storm infrastructure necessary for hurricanes to thrive. La Niña enhances the factors that lead to hurricane formation. It’s making the U.S. more vulnerable to wildfires, especially in the West.
Forecasting the Atlantic hurricane season is very much tied to our knowledge of ENSO conditions. Usually El Niño suppresses hurricane activity, and La Niña/neutral conditions contribute to more active seasons. ENSO’s impact goes well beyond hurricanes, extending its reach to rainfall, snowfall, temperature swings, and even the development of tornadoes.
The observational record of ENSO is less than 160 years, making it difficult for scientists to understand its behavior and evolution over the long term. At least through October, ENSO-neutral conditions are predicted, with perhaps a return toward negative PDO values by fall. Such lack of prevailing El Niño or La Niña patterns makes forecasting much more challenging.
In 2023, a strong El Niño year, meteorologists were already on alert for an atypical uptick in storms. “We had an El Niño in 2023 but still saw more storms than usual,” explained James Done, a climate scientist. This important and well-deserved observation underscores a debate within the scientific community that continues to rage on about the connection between ocean temperatures and hurricane activity.
“So, there’s a big debate: Does El Niño still kill off hurricanes, or are oceans now so warm that it changes the relationship? It’s an open question.” – James Done
The complexity of these relationships is underscored by the fact that without clear El Niño or La Niña signals, other factors significantly influence seasonal weather patterns. “Without an El Niño or a La Niña, a range of other factors drive seasonal weather,” Done noted.
Researchers are now working to understand why the Atlantic cooled so drastically from February to March of this year. Some meteorologists think this could be a precursor to a quieter hurricane season, too. The unpredictability that comes hand-in-hand with neutral ENSO conditions makes forecast conditions even more precarious.
Di Liberto, a meteorologist, acknowledged the current situation’s ambiguity: “All signs pointed toward a horrible hurricane season, but it wasn’t the worst-case scenario it could have been.” This sentiment sums up the plight of forecasters who are attempting to forecast enhanced or reduced storm activity with changing climate conditions.
Long-term climate change will likely affect El Niño and La Niña too. As climate change continues to raise ocean temperatures, scientists have become more concerned about how these changes will affect atmospheric weather patterns around the globe. Getting a handle on these dynamics will be key for future production forecasts and to better prepare for growing extreme weather events.
