The IOOS-led Hurricane Glider Collaboration celebrated its 8th successful coordinated field campaign in 2025. During the season, NOAA, the U.S. Navy, IOOS Regional Associations and academic partners flew 79 glider missions. If each glider’s time in the water in 2025 was added up, it would total 3,932 days, nearly 11 years. Gliders were deployed across coastal waters of the Atlantic and Pacific Oceans, Caribbean Sea, and Gulf of America.

There are two primary elements of hurricane forecasting: the track — where the storm is going — and the intensity — how it will strengthen and weaken along the way. A thorough picture of the conditions a storm will encounter above, at, and below the water is vital for forecasting intensity. Below the surface, data gathered by gliders can tell us, for instance, if there is a deep patch of warm water, which can lead to a storm growing stronger, or a pool of cold water near the surface, which can lead to weakening.

All gliders measure water temperature, salinity, and pressure to depths of 3,300 ft — a little over half a mile. They monitor and track ocean features linked to hurricane intensity changes, such as the Loop Current, Gulf Stream, Mid-Atlantic cold pool, freshwater barrier layers, Atlantic warm pool, and eddies and rings. Glider data are transmitted to IOOS’ Glider Data Assembly Center (GDAC). The GDAC sends the data to NOAA’s National Data Buoy Center (NDBC) for use in NOAA’s models, where it helps refine intensity forecasts. In 2025, gliders collected and transmitted over 90,000 temperature and salinity data profiles to the GDAC and NDBC.

Hurricane Glider Coordination

Numerous partners work together each year to coordinate hurricane glider operations and data delivery. In 2025, this partnership included 17 institutions, spanning NOAA programs, academic institutions, IOOS Regional Associations, private companies, Federal agencies, and international partner programs.

Since 2018, the U.S. Navy Commander, Naval Meteorology and Oceanography Command, and its operational command, the Naval Oceanographic Office, have contributed Navy Littoral Battlespace Sensing gliders to NOAA for hurricane glider missions. Navy gliders make up around 20% of all the Atlantic hurricane glider profiles gathered each season. In 2025, the Navy deployed 9 hurricane gliders in the Atlantic basin, which flew for a total of 954 days and transmitted 9,459 glider profiles to the GDAC.

Figure 1. Glider tracks during the 2025 Atlantic hurricane season. Image credit: NOAA/IOOS

Figure 2. Glider tracks during the 2025 Pacific hurricane season. Image credit: NOAA/IOOS

Storms
During the 2025 hurricane season, there were 13 named storms in the Atlantic, five of which became hurricanes. Of those five, three became Category 5 hurricanes, tying for the second-most on record in a single season in the Atlantic basin. In the Central and Eastern Pacific there were 20 named storms, 12 of which became hurricanes and five of those strengthened to Category 3 or higher. And, for the first time in a decade, not a single hurricane made landfall in the U.S.

Hurricane Erin was a significant storm in the 2025 season, rapidly intensifying from a tropical storm to a Category 5 hurricane in approximately 24 hours. Three gliders collected observations near the eye of Erin when it passed north of the Virgin Islands and Puerto Rico (Figure 3). The data collected by these gliders were fed into NOAA’s Environmental Modeling Center (EMC) models that feed the hurricane models, and were also used by NOAA’s National Hurricane Center (NHC) to inform their forecasts.

Figure 3. Hurricane Erin rapidly intensified in approximately 24 hours, going from a tropical storm to a Category 5 hurricane. Three gliders collected observations near the eye of Erin when it passed north of the Virgin Islands and Puerto Rico, following its rapid intensification. Image credits: NOAA/IOOS (left) and NOAA/AOML (right)

Innovations in modeling
Model comparisons done by the Rutgers University Model Evaluation Team demonstrated the importance of glider subsurface data in keeping NOAA’s Real-Time Ocean Forecast System (RTOFS) ocean model on track (Figure 4). Gliders provided near-real time ocean conditions that improved model temperature and salinity results. Including ocean observations, such as glider data, in hurricane prediction models has been shown to enhance the accuracy of model intensity predictions by up to 30-50% (Glenn et al. 2016, Le Hénaff et al. 2021, Domingues et al. 2021).

Figure 4. Assimilation of subsurface glider data resulted in NOAA’s RTOFS 2.3 model showing warmer ocean temperatures. (A) RTOFS 2.3 ocean temperature outputs before glider data assimilation. (B) RTOFS 2.3 ocean temperature outputs after glider data assimilation; the oval highlights an area showing increased ocean temperatures, adding to the motivation for the upgrade to RTOFS 2.5. Image credit: Scott Glenn, Rutgers University

Broader Observing System Coordination

Continued refinement of NOAA’s hurricane intensity forecasts calls for closing gaps in oceanic and atmospheric observations. NOAA works with numerous partners to deploy systems that capture data below the ocean surface, at the surface where air and water meet, and in the atmosphere above the water to gain a full understanding of the primary factors affecting hurricane intensity and movement. Some of these observations improve today’s forecasts, while others capture information needed to better understand and improve future weather and ocean models.

Gliders are a component of NOAA’s Coordinated Hurricane Atmosphere-Ocean Sampling (CHAOS) Experiment, led by the Global Ocean Monitoring and Observing Program (GOMO) with NOAA’s Oceanic and Atmospheric Research. CHAOS is a coordinated multi-platform, multi-institutional approach utilizing a diverse suite of observing platforms focused on targeted observations through the atmosphere and into the ocean as it relates to hurricane predictions and modeling.

CHAOS helps NOAA improve the collocation of measurements across the air-sea interface during storms. For example, several observing platforms were coordinated along the path of the Category 5 storm Hurricane Erin, including NOAA P-3 aircraft, dropsondes, drifters, ocean gliders, and moorings (Figure 5).

Figure 5. Coordinated observing platforms coordinated across the eye of Hurricane Erin. Image credit: Edo Mazza (UW CICOES/PMEL) and Lev Looney (U Miami CIMAS/AOML)

The Global Ocean Observing System (GOOS) Co-Design Programme’s Tropical Cyclone (TC) Exemplar, co-chaired by GOMO and Rutgers University, is supporting efforts to enhance collaborations with international partners to increase the availability of ocean profile data that includes deploying gliders internationally and observing ocean conditions where tropical cyclones rapidly intensify, such as the Caribbean, necessitating specific marine scientific research permissions. In 2025, several international partners joined the IOOS-led hurricane glider collaboration to fly gliders in the coastal waters of Bermuda, the Dominican Republic, the Bahamas, Mexico, and Barbados (including Trinidad and Tobago and Guyana). U.S. and Mexican gliders and profiling floats were supported by the U.S. National Academies Understanding Gulf Ocean Systems (UGOS) Program.