Flash floods are major meteorological disasters which occur around the globe. Understanding of this phenomenon is a challenging problem because it is necessary to understand both complex dynamic and microphysical processes at scales of motion that are smaller than typically measured by conventional weather networks. This scale of motion is termed storm-scale or mesoscale by meteorologists. The National Science Council of Taiwan established a Multiple Hazards Mitigation Project whose meteorological component focused on improving flash flood predictions. A major field project, entitled the Taiwan Area Mesoscale Experiement (TAMEX), was held in the Spring of 1987. The project was a joint effort of various Taiwanese agencies with participation from the National Oceanic and Atmospheric Administration and the National Science Foundation (NSF). The scientific goals were to study the mesoscale systems that form on a quasi-stationary and consistent feature known as the Mei-Yu front and cause the heavy rains known as the "plum rains". Under a previous award, the Principal Investigator used the special observations collected during the TAMEX in diagnostic studies that identified important factors for the formation of heavy rainfall. These studies have lead the Principal Investigator to concentrate on three topics -- the dynamics of the low level jet; the barrier jet which forms along the northwest windward coast of Taiwan under the prevailing southwesterlies; and the upper-level circulations. In addition to further analysis using the observational data, the Principal Investigator will utilize a numerical model to help identify the important dynamic factors for heavy rain production.
