2b.6 Relating Tropical Cyclone Rainfall Patterns to Storm Size

During the period 1970-1999, Rappaport (2000) found that almost 60% of TC-related deaths in the U.S. were due to fresh water floods caused by heavy rainfall. To reduce this statistic, it is important to improve the accuracy of TC rainfall forecasts by examining the spatial distribution of the rain shield about the criculation center of the storm. Previous researchers have investigated TC rainfall patterns by placing a grid over each storm and determining the rainfall amounts within each grid cell. The spatial resolution of these grid cells has ranged from 15 – 111 km (Cerveny and Newman 2000; Rao and Macarthur 1994; Rodgers et al. 1994). Within each study, the same grid was utilized to analyze all of the TCs. However, utilizing a “one size fits all” grid does not allow for a relationship between a TC’s size and the spatial extent of its rain shield to be established. This study investigated whether a relationship exists between TC size and the spatial distribution of TC rainfall by utilizing sets of annular rings spaced according to each storm’s size, and by investigating asymmetries in the extent of the rain shield and wind radii in each quadrant of the storm. Merrill (1984) found that TCs are largest as they migrate into subtropical latitudes where they begin to encounter sources of angular momentum such as mid-latitude troughs, and that the majority of U.S. landfalling TCs have reached their maximum size. If TC rainfall patterns are related to their size, changes in storm size prior to landfall could help forecast the location of postlandfall TC precipitation.