A Comparison of Outer and Inner Rainband Mesocyclone Characteristics in Hurricane Georges

Hurricane Georges moved across Puerto Rico on 21 and 22 September 1998. A number of mesocyclones occurred in the rainbands. Previous research on mesocyclones in tropical cyclones focused mainly on characteristics in the outer rainbands. A comparison of differences between inner and outer rainband mesocyclone parameters in Hurricane Georges was performed.

Radar data was examined from the WSR-88D in Puerto Rico. Rainbands were classified as outer when located 60 n mi, or more from the center of the eye, and inner if less than 60 n mi. Averages of mesocyclone parameters for bases, tops, vertical depth, and azimuthal diameter were computed separately for outer rainbands, inner rainbands, and all rainbands. Outer rainband mesocyclones were found to have bases averaging 1.0 km lower and tops 2.2 km lower than for the inner rainband mesocyclones. Vertical depth of mesocyclones was less by 1.1 km for mesocyclones in the outer rainbands. Averages for all rainbands were bases at 2.1 km, tops at 4.3 km, and vertical depths at 2.2 km. Azimuthal diameters were found to average 1.2 n mi less in the outer rainbands. In all rainbands azimuthal diameters averaged 3.3 n mi.