The eyewall structure of Hurricane Alien is examined from analyses of multiple aircraft data on two days, 5 and 8 August 1980. These data sets are unique in that, for the first time, three instrumented aircraft executed coordinated radial penetrations of the eyewall at multiple levels. The data collected on 5 August illustrate the persistence of various features on horizontal scales > 10 km over several hours. Composite cross sections constructed from the 8 August data show similar structure, although the eye diameter had decreased to less than half that of 5 August. The convergence of air in the eyewall was highly two-dimensional. This convergence supported organized ascent that was along the inner edge of the high reflectivity region and displaced inward several kilometers from the radius of maximum wind (RMW). A mean eyewall updraft of 5–6 m s−1 is computed from integration of the two-dimensional continuity equation. Embedded within the two-dimensional eyewall were cores of high reflectivity t... Abstract The eyewall structure of Hurricane Alien is examined from analyses of multiple aircraft data on two days, 5 and 8 August 1980. These data sets are unique in that, for the first time, three instrumented aircraft executed coordinated radial penetrations of the eyewall at multiple levels. The data collected on 5 August illustrate the persistence of various features on horizontal scales > 10 km over several hours. Composite cross sections constructed from the 8 August data show similar structure, although the eye diameter had decreased to less than half that of 5 August. The convergence of air in the eyewall was highly two-dimensional. This convergence supported organized ascent that was along the inner edge of the high reflectivity region and displaced inward several kilometers from the radius of maximum wind (RMW). A mean eyewall updraft of 5–6 m s−1 is computed from integration of the two-dimensional continuity equation. Embedded within the two-dimensional eyewall were cores of high reflectivity t...