One of the most difficult forecast challenges is associated with landfalling and transitioning tropical cyclones because the potential for a major natural disaster associated with high winds, significant storm surges, and coastal and inland flooding is a major concern. The forecast challenge is increased because the distribution of precipitation in a tropical cyclone is highly variable from one storm to another with respect to intensity, maximum amount, areal distribution, and duration. Some cases exhibit along-track precipitation, while others show right or left of track rainfall patterns. The goal of this study is to determine the causes of this rainfall variability through composite and case study analyses.

To build these composites, tropical cyclones have been chosen with observed precipitation distributions that are representative of characteristic rainfall signatures in the overall sample of storms. The Unified Precipitation Dataset (UPD), the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, and observed data and conditions have been utilized. Individual case studies will also be prepared to further refine the results from the composites and to diagnose the reasons for the observed rainfall distribution within a given storm (e.g. coastal front and orographic influences).