What Is a Hurricane?

A hurricane is an intense tropical cyclone that forms over warm ocean waters in the Atlantic basin or eastern Pacific, characterized by a sustained wind speed of at least 74 miles per hour (64 knots), a well-organized low-pressure center known as the eye, and spiral rainbands extending outward from the core. The term hurricane is regionally specific: the same storm type is called a typhoon in the western Pacific and a tropical cyclone in the Indian Ocean and South Pacific. Hurricane science draws on atmospheric physics, physical oceanography, remote sensing, and numerical modeling to understand storm genesis, intensification, and dissipation, and to produce the forecasts on which emergency management and coastal engineering depend.

Hurricanes derive their energy from the latent heat released when warm, moist air rises and water vapor condenses. Sea surface temperatures of at least 26–27 °C in the upper 50 meters of the ocean are generally required to sustain development, which is why hurricane season in the Atlantic spans June through November when warm water is most available.

Formation and Atmospheric Physics

Hurricane formation, or tropical cyclogenesis, begins with a pre-existing atmospheric disturbance, such as an easterly wave moving off the African coast, that provides organized convection. As warm, moist surface air converges and rises, it releases latent heat that warms the atmosphere above the center, reducing surface pressure. The Coriolis effect, absent near the equator and thus a limit on genesis below about 5° latitude, causes the inflow to spiral cyclonically. A developing storm passes through stages of tropical disturbance, tropical depression, and tropical storm before reaching hurricane intensity at 64 knots. Rapid intensification, defined as a wind speed increase of at least 35 knots in 24 hours, remains a critical forecasting challenge because it depends on the precise upper-ocean heat content, wind shear, and convective organization at the moment of intensification.

Ocean-Atmosphere Interaction and Oceanography

The ocean does not merely supply energy to hurricanes; it also responds dynamically to them. A passing hurricane mixes the upper ocean through wind-driven upwelling and turbulent entrainment, cooling sea surface temperatures in its wake and reducing the energy available to a following storm. Salinity stratification in the mixed layer affects how rapidly this cooling occurs. Operational oceanography tracks ocean heat content using Argo profiling floats, expendable bathythermographs deployed from aircraft, and satellite altimetry measurements of sea surface height, all of which inform coupled ocean-atmosphere hurricane intensity models. NOAA's Atlantic Oceanographic and Meteorological Laboratory maintains the primary U.S. research program on hurricane dynamics, including annual field campaigns using specially instrumented reconnaissance aircraft.

Remote Sensing and Monitoring

Remote sensing instruments carried by polar-orbiting and geostationary satellites provide the continuous, wide-area observations that underpin modern hurricane forecasting. Infrared and water-vapor imagery from geostationary platforms such as GOES-16 resolve cloud structure every ten minutes. Microwave sounders penetrate cloud cover to measure temperature and moisture profiles through the storm's vertical extent. Synthetic aperture radar (SAR) systems map ocean surface wind fields at fine spatial resolution, capturing wind speed and direction even inside a storm's core where conventional scatterometers saturate. Research on remote sensing and analysis of tropical cyclones surveys C-band SAR, scatterometers, and geostationary imagers being used operationally for track and intensity estimation. The NOAA National Hurricane Center integrates these data streams into five-day track forecasts, storm surge guidance, and wind probability products for the Atlantic and eastern Pacific basins.

Applications

Hurricane science and technology have applications in a wide range of fields, including:

• Emergency management and evacuation planning for coastal communities
• Storm surge modeling and coastal flood hazard mapping
• Maritime routing and shipping safety during active hurricane seasons
• Coastal infrastructure design including flood barriers and building codes
• Climate research examining trends in tropical cyclone frequency and intensity