MESOSCALE AND CONVECTIVE-SCALE CHARACTERISTICS OF MATURE HURRICANES

Analysis of instrumented aircraft data taken during radial penetrations of four recent intense hurricanes reveals common mesoscale and convective scale features of the inner core region. The structure and organization of the convection, wind, and vertical motion are studied by combining the data from the aircraft's state parameter instrumentation with quantitative radar measurements.; The major new findings of this study are (1) the eyewall vertical motion was highly organized and was located several kilometers inward from the maximum winds and highest rainfall, (2) the eyewall sloped outward substantially with height, (3) the range of vertical velocities and rainfall rates were much weaker than those typically found in continental thunderstorms, (4) storms with symmetric wind distributions were found to have circular and contracting eyewalls, and (5) vertical motions in rainbands were not as highly organized as the eyewall.; The highly two-dimensional convergence of air into the eyewall resulted in an updraft of 5-6 m s('-1) that was organized around the entire eyewall. Embedded within this convergence region were cores of 42-47 dBZ that were 2-5 km in diameter, more three dimensional, and generally short lived. Maximum velocities in updraft cores were 9-12 m s('-1). The region of maximum rainfall and downdrafts were located under the sloping updraft. A schematic cross section of the cloud, precipitation, and airflow of a mature hurricane eyewall is shown. Implications of the observations to weather modification are also discussed.