Hurricanes are among the most costly and destructive weather events in the United States, making accurate forecasts essential for protecting lives, property and the economy. Producing these forecasts requires accurate information about a storm’s track, intensity and wind structure to assess hazards, identify communities at risk and issue timely watches and warnings. Satellites in low Earth orbit (LEO) help NOAA meet this challenge by providing critical observations over remote oceans, where most hurricanes form.
The Advanced Technology Microwave Sounder (ATMS) on board NOAA’s Joint Polar Satellite System (JPSS) satellites can see through clouds to gather information about temperature and moisture within hurricanes. These observations provide scientists with a clearer picture of a storm’s internal structure and help reveal conditions that could signal strengthening.
ATMS-derived cross-sections capture temperature anomalies associated with Hurricane Helene on September 25, 2024. A region of warm temperatures near the storm’s center is shown in red and orange and signals a strong, organized system. The presence of a warm core is a key indicator of hurricane intensity and serves as an important metric for tracking the storm development. Credit: NOAA NESDIS Center for Satellite Applications and Research (STAR).
Researchers at the Cooperative Institute for Research in the Atmosphere (CIRA) have transformed these microwave observations into operational tools for forecasters at the National Hurricane Center and the Joint Typhoon Warning Center. The Hurricane Intensity and Structure Algorithm (HISA) uses temperature and moisture profiles from NOAA’s Microwave Integrated Retrieval System (MiRS). MiRS combines data from ATMS and other LEO microwave sensors to estimate hurricane intensity and the extent of damaging winds. HISA provides objective information that complements traditional forecasting methods and helps forecasters better assess a storm’s potential impacts.
HISA intensity estimates for Hurricane Erin, which produced life-threatening surf and rip currents along much of the U.S. East Coast, illustrate the storm’s rapid intensification on August 16, 2025, when it strengthened to a Category 5 with maximum sustained winds of approximately 139 knots (160 miles per hour). The red line represents the hurricane intensity estimate produced by HISA, while colored dots indicate individual estimates derived from MiRS retrievals from multiple microwave sounders: ATMS onboard Suomi NPP (cyan), NOAA-20 (mustard yellow) and NOAA-21 (burgundy), and AMSU aboard MetOp-B (light blue) and MetOp-C (gray). Credit: Dr. John Knaff, CIRA/NOAA NESDIS.
One of HISA’s greatest strengths is its ability to estimate the wind structure of a storm, including how far tropical-storm-force and hurricane-force winds extend from the center. This information is critical because a hurricane’s most dangerous impacts can extend well beyond its eye and far from where it makes landfall. Even storms that remain offshore can produce coastal flooding, life-threatening surf and damaging winds across large areas.
HISA intensity estimates for Hurricane Erin, which produced life-threatening surf and rip currents along much of the U.S. East Coast, illustrate the storm’s rapid intensification on August 16, 2025, when it strengthened to a Category 5 with maximum sustained winds of approximately 139 knots (160 miles per hour). The red line represents the hurricane intensity estimate produced by HISA, while colored dots indicate individual estimates derived from MiRS retrievals from multiple microwave sounders: ATMS onboard Suomi NPP (cyan), NOAA-20 (mustard yellow) and NOAA-21 (burgundy), and AMSU aboard MetOp-B (light blue) and MetOp-C (gray). Credit: Dr. John Knaff, CIRA/NOAA NESDIS.
CIRA continues to enhance HISA by applying machine learning, evaluating observations from commercial small satellites (smallsats) and developing new ways to analyze storm structure. These efforts are helping advance the algorithm and prepare it for NOAA’s next generation of environmental satellites.
Looking ahead, NOAA’s Near Earth Orbit Network (NEON) is expected to introduce a next-generation hyperspectral microwave sounder designed to provide even more detailed atmospheric observations. Combined with advances in artificial intelligence and new satellite missions, these innovations promise to further improve hurricane monitoring and provide forecasters with more timely, accurate information to support critical decisions before and during dangerous storms.
Learn more about HISA in Feature 6 of the 2025 LEO Science Digest, Inside the Storm: Estimating Tropical Cyclone Intensity with LEO Microwave Soundings. Published each January, the Digest highlights real-world applications of LEO satellite observations, showcasing how they enhance weather forecasting, support disaster response and benefit the U.S. economy.
