The re-intensification of Typhoon Sinlaku (2008)

Abstract

In September 2008, Typhoon Sinlaku re-intensified from a sheared, asymmetric, weak tropical storm to a typhoon southwest of Japan. The evolution of the tropical cyclone (TC) structure was observed by multiple aircraft as part of the TCS-08 and T-PARC field programs. Airborne dual-Doppler radar, dropwindsondes, and flight-level observations reveal critical interactions among the decaying TC and three mesoscale vortices that initiated the re-intensification of Sinlaku. The structural characteristics of the three vortices, which include a vigorously growing convective tower, a mesoscale convective vortex, and a low-level hybrid vortex, are defined with respect to representative precipitation processes. Following interaction with the mesoscale vortices, re-intensification proceeded via processes consistent with axisymmetrization as multiple convective bursts rotated cyclonically and inward while a region of older convection propagated outward to become a principal band. Subsequent aircraft observations revealed a warm-core, near-symmetric typhoon. The overall re-intensification scenario is examined with respect to interactions among a variety of processes that vary from synoptic scale to convective scale. Synoptic-scale southwest monsoon flow over elevated sea-surface temperatures and high ocean heat content preconditioned the region where the critical convective episodes began. Mesoscale processes then acted to produce and re-distribute positive vorticity that defined the re-intensification of TY Sinlaku.