Convective structure in rapidly intensifying tropical cyclones as depicted by passive microwave measurements

Abstract

Microwave remote sensing of tropical cyclones undergoing rapid intensification (RI; δV ≥ 30 kt/24 h) reveals structural differences from storms of lesser intensification rates; with 85 GHz signatures depicting a moderately intense convective ring surrounding the storm center. Overpass composites binned by wind shear magnitude show the ring is consistent for low shear RI storms, forming approximately 6 h before RI begins, then contracting and intensifying over the following 24 h. High shear RI events make up a smaller portion of all cases, with little evidence of a convective ring. With the majority of RI cases occurring in low shear, microwave observations of convective axisymmetry prior to RI onset may hold promise for its forecast, with an observed lag between the structural and heating modification and resultant intensification. Given the potential for destruction to vulnerable coastal interests and the current poor predictability of RI, any increase in RI forecast skill would be of great benefit to society. Copyright 2011 by the American Geophysical Union.