El Niño dampens Atlantic hurricane risk, but increases it in Pacific

Atlantic hurricane season forecasting this year has turned on one major climate signal: El Niño is expected to curb storm development in the Atlantic even as it raises the odds of more activity in parts of the Pacific, according to forecasters speaking as NOAA released its seasonal outlook on Thursday.

The National Oceanic and Atmospheric Administration forecast a below-average Atlantic hurricane season with eight to 14 named storms. NOAA predicted three to six of those systems would strengthen to hurricane status, and one to three would become major hurricanes, a category defined as storms reaching wind speeds above 110 mph (177 kph). NOAA also said there is a 55% chance that the season overall will be below average.

Meteorologists pointed to the broader historical backdrop against which this forecast is being made. Colorado State University, which has helped pioneer seasonal hurricane forecasting, predicted “the lowest overall activity since 2015,” which Colorado State linked to the strongest El Niño in the last 75 years. Colorado State’s hurricane expert Phil Klotzbach said the university’s forecast is likely to be revised to even lower numbers in June, and he tied the expectation to a shift away from the recent pattern in which nine of the last 10 Atlantic hurricane seasons were above normal or hyperactive.

Several researchers cautioned that “less active” does not mean “safe.” University at Albany atmospheric scientist Kristen Corbosiero said forecasters should expect a less active year than what meteorologists have seen recently and perhaps significantly so below average, but she stressed that “it only takes one to cause real devastation and destruction in the mainland U.S. or even in Hawaii.” Corbosiero described El Niño as “the elephant in the room,” explaining that scientists have long found correlations between El Niño conditions and lower Atlantic hurricane activity as well as stronger and more storms over the central and eastern Pacific.

NOAA’s seasonal outlook also described the probability of El Niño conditions persisting into the Northern Hemisphere summer. NOAA Administrator Neil Jacobs said Thursday there is a 98% chance that there will be an El Niño this summer and an 80% chance it will be moderate or strong. In a season where El Niño reaches strong or very strong conditions, NOAA-referenced analysis cited by The Associated Press found that the odds skew toward fewer storms and fewer hurricanes than the 1991-2020 average.

Forecasters said El Niño works against Atlantic hurricane development through changes in the atmosphere that can hinder storm organization. Corbosiero said El Niño can produce cross winds in the atmosphere roughly 1 mile to 7 miles above the surface that “can basically blow apart the thunderstorms that make up” a hurricane. Brian Tang, an atmospheric scientist at the University at Albany, described how a “stronger than normal wind shear tends to tilt storms,” pushes dry air into developing systems, and prevents storm development and intensification in the first place. Matthew Rosencrans, lead hurricane season forecaster with NOAA’s National Weather Service, said that while El Niño reduces the number and intensity of weaker storms, storms that reach hurricane strength with 74 mph winds can become more self-reinforcing and less susceptible to being dampened by the shear.

Even with the Atlantic forecast being weaker, forecasters said the seasonal outlook is a global picture, not a single-basin tradeoff. The same climate pattern that suppresses hurricanes in the Atlantic is expected to increase the likelihood of storms forming farther west in the Pacific, where the atmosphere and ocean conditions tend to support storm development. Jacobs said there is a 70% chance that the eastern Pacific will have an above normal season, with NOAA forecasting 15 to 22 named storms there and nine to 14 becoming hurricanes, including five to nine major hurricanes, compared with averages of 15 named storms, eight hurricanes and four major hurricanes.

Rosencrans said the main development area in the central Pacific tends to shift closer to Hawaii during El Niños, while Corbosiero described how eastern Pacific storms near Baja Mexico often head west and affect relatively limited areas, even though some can still turn east or north and bring heavy damage. She cited Hurricane Otis in 2023, which smashed into Mexico, and the 1992 Hurricane Lester, which brought heavy rains to parts of the U.S. Southwest. Corbosiero also noted that Hawaii has been threatened in El Niño years, pointing to Hurricane Iniki in 1992.

The forecast comes as Hawaii officials look ahead amid recent impacts. Gov. Josh Green said the state is preparing for hurricanes even as parts of Hawaii are still reeling from back-to-back storms that caused catastrophic flooding.

The Atlantic hurricane season runs from June 1 through Nov. 30, while the eastern Pacific hurricane season begins May 15 and also ends Nov. 30. Forecasters said El Niños can make hurricane seasons longer, and John Bravender, a weather service meteorologist in Honolulu, said warmer waters across the region can allow hurricanes to maintain their strength at higher latitudes and longer through the year.

In addition to El Niño, Rosencrans said dry conditions in Africa and sea-surface conditions in the Atlantic that are only slightly warmer than normal also contribute to the forecast for a weaker Atlantic season. Forecasters also noted that hurricane activity is influenced by multiple atmospheric and ocean conditions even when a dominant signal like El Niño sets the overall tone.

Sources cited in the Associated Press report include contributions from writer Jennifer Sinco Kelleher in Honolulu.