Spatial and Temporal Distributions of Tropical Cyclone Rainfall Using Data from the Global Forecast System and Stage IV Precipitation

Heavy rainfall is one of several characteristics of tropical cyclones (TCs) that leads to death and destruction. Our ability to forecast the locations and amounts of TC related rainfall needs improvement. We have created a database of all Atlantic Basin tropical cyclones (TCs) that produced rainfall over the continental United States between 2004-2012. Each storm is categorized according to various environmental parameters (shear, instability, etc.) and storm attributes (intensity, storm motion, etc.). Stage IV 6-hour rainfall patterns and amounts for each storm then are analyzed statistically with respect to the storm's attributes to determine the factors influencing the intensity and location of the rainfall. Finally, Global Forecast System (GFS) 6-hour rainfall accumulations are compared to the Stage IV data to assess the spatial and temporal performance of the GFS rainfall forecasts and identify situations where the skill of the forecasts is good or poor. This paper will present preliminary results of this study as a first step toward improving TC precipitation forecasts.