Dr. Frank will conduct an investigation of the processes that lead to tropical cyclone development in the western Pacific. The study, which combines observational analyses and numerical modeling experiments, will focus on the earliest stages of cyclogenesis. Occasionally, a strong mesoscale vortex forms within a loosely organized tropical cloud cluster. Over the years, researchers have developed a fairly clear picture of the processes which cause some of these vortices to grow into mature tropical cyclones (the "intensification" phase of the hurricane/typhoon life cycle). By comparison, the "genesis" phase is very poorly understood. Dr. Frank will examine the large scale circulation patterns present during tropical cyclogenesis, the origins of these patterns, and the physical processes leading to vortex formation. Synoptic-scale surges of southwesterly flow into the West Pacific Monsoon Trough are frequently observed to precede cyclogenesis in this region. Particular attention will be given to their role in cyclogenesis. The observational analyses will be based on a five year global data set, and on high resolution data sets collected during the Tropical Cyclone Motion experiment of 1990, in which Frank participated. The modeling studies will employ the newly developed nonhydrostatic version of the PSU/NCAR mesoscale model to simulate vortex formation under a variety of conditions typical of the West Pacific. This research will be important for understanding, and ultimately predicting, the development of tropical cyclones.
