Forecasters predict another active 2025 Atlantic hurricane season » Yale Climate Connections

Once again, an unusually active Atlantic hurricane season is likely in 2025, the Colorado State University hurricane forecasting team said in its latest seasonal forecast, issued April 3. Led by Phil Klotzbach, with coauthors Michael Bell and Levi Silvers, the CSU team called for 17 named storms, nine hurricanes, four major hurricanes, and an Accumulated Cyclone Energy, or ACE, of 155 (26% above average). That’s higher than the long-term averages for the period 1991-2020 of 14.4 named storms, 7.2 hurricanes, 3.2 major hurricanes, and an ACE of 123. Last year, there were 18 named storms, 11 hurricanes, five major hurricanes, and an ACE of 162. Over the past decade, only two Atlantic seasons have ended up with ACE significantly below the 1991-2020 average: 2022 and 2015.

The CSU outlook predicted higher odds of a major hurricane hitting the U.S. than usual: 51% (long-term average: 43%). It gave a 26% chance for a major hurricane to hit the East Coast or Florida Peninsula (long-term average: 21%), and a 33% chance for the Gulf Coast (long-term average: 27%). The Caribbean was forecast to have a 56% chance of having at least one major hurricane pass through (long-term average: 47%).

The CSU forecast uses a statistical model honed from more than 40 years of past Atlantic hurricane statistics, plus dynamical model output from four groups: ECMWF (European model), UKMET, Japan Meteorological Agency, and Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC).

The CSU team cited two main reasons for their above-average 2025 forecast:

1) ENSO-neutral or weak La Niña conditions seem likely this fall 

La Niña conditions in the Eastern Pacific have been weak in recent months, and most models are either forecasting neutral or weak La Niña conditions for the peak of the Atlantic hurricane season. NOAA’s Climate Prediction Center, in its latest March 13 monthly advisory, predicted a 49% chance of neutral conditions, a 38% chance of La Niña, and a 13% chance of El Niño for the peak of the Atlantic hurricane season.

El Niño conditions favor a slower-than-usual Atlantic hurricane season as a result of an increase in the upper-level winds over the tropical Atlantic that can tear storms apart (higher vertical wind shear). In contrast, when neutral or La Niña conditions are present, an active hurricane season becomes more likely. Since 1950, U.S. landfalls by major hurricanes have been more than twice as likely during a La Niña year compared to an El Niño year (Fig. 2).

2) Ocean temperature patterns

Currently, sea surface temperatures are much warmer than average in the western and central Atlantic and eastern subtropical Atlantic and are near to slightly below average in the eastern tropical Atlantic (Fig. 1). Enhanced warmth in the eastern subtropical Atlantic and in the Caribbean correlates well with what is typically seen in April before active Atlantic hurricane seasons.

As is its practice, the CSU team included this standard disclaimer:

“Coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them. Thorough preparations should be made for every season, regardless of how much activity is predicted.”

Analog years

Five years with similar preseason January, February, and March atmospheric and oceanic conditions were selected as “analog” years that the 2025 hurricane season may resemble. These analog years occurred the second year after an El Niño event and had La Niña conditions during January-February of their current year. The analog years also had above-average sea surface temperatures in the tropical and subtropical Atlantic. The analog years were:

• 1996 (13 named storms, 9 hurricanes, and 6 major hurricanes)
• 1999 (12 named storms, 8 hurricanes, and 5 major hurricanes)
• 2006 (10 named storms, 5 hurricanes, and 2 major hurricanes)
• 2008 (16 named storms, 8 hurricanes, and 5 major hurricanes)
• 2011 (19 named storms, 7 hurricanes, and 4 major hurricanes)
• 2017 (17 named storms, 10 hurricanes, and 6 major hurricanes)

The average activity for these years was 14.5 named storms, 7.8 hurricanes, 4.7 major hurricanes, and an ACE of 154 – above-average levels of activity. Among the analog years, 2017 was a notorious one with three Category 4 hurricanes making a U.S. landfall: Harvey, Irma, and Maria. However, 2006 was quiet, with no landfalling hurricanes anywhere in the Atlantic.

A caveat: April hurricane season forecasts have little or no ‘skill’

On average, April forecasts of hurricane season activity have had no “skill,” or even negative skill, when computed using the Mean Square Skill Score. This does not mean a particular April forecast will be incorrect — just that, on average, a forecast simply using climatology would do as well or better. April forecasts must deal with the so-called spring predictability barrier. In April, the El Niño/La Niña phenomenon commonly undergoes a rapid change from one state to another, making it difficult to predict whether El Niño, La Niña, or neutral conditions will be in place for the coming hurricane season.

In April 2024, CSU predicted an extremely active season — 23 named storms, 11 hurricanes, five major hurricanes, and an ACE of 210. The forecast did well since the actual activity was 18 named storms, 11 hurricanes, five major hurricanes, and an ACE of 162. However, their April forecasts in 2023 and 2022 did not fare so well.

The next CSU forecast, due June 11, is worth close attention, as late May/early June forecasts have shown considerable skill over the years. Among other outlooks in the works:

• NOAA is set to issue its first seasonal hurricane forecast for 2025 in late May.
• The British private forecasting firm Tropical Storm Risk, Inc. will issue its next 2025 Atlantic hurricane season forecast on April 7. Its first forecast for the season, issued December 10, called for 15 named storms, seven hurricanes, three major hurricanes, and an ACE index of 129. The skill of a forecast made so far in advance was just 0-4%, they said.

Read: How to make an evacuation plan

Bob Henson contributed to this post.