A Convective Cell in a Hurricane Rainband

Abstract

On 10 October 1983 the two NOAA WP-3D aircraft completed a mission designed to provide airborne Doppler radar data for a convective cell embedded in a weak rainband on the trailing side of Hurricane Raymond. Comparisons of the wind field produced from the pseudo-dual-Doppler radar technique with in situ wind measurements suggest that the larger convective-scale feature may be resolved if the sampling time is kept to a minimum. The convective cell was found to move downband faster than any environmental winds but slightly slower than the winds found in the reflectivity core that delineates the cell. In the core of the cell the tangential wind is increased and the radial inflow turns to outflow with respect to the circulation center. The flow field demonstrates that the downband stratiform portion of a rainband is not from cells currently active since the updraft detrains upwind relative to the cell but rather it is due to the fallout from ice particles placed into the upper troposphere by clouds that have since dissipated. The mass flux of this cell is estimated to be 5%?10% of the mass flux accomplished by an eyewall of a moderate tropical cyclone. This finding supports the concept that large, convectively active rainbands have a major effect on the subcloud layer air flowing toward the eyewall.