Initial and Boundary Condition Impacts on Hurricane Katrina Track and Intensity Forecasts

Impacts of initial and boundary conditions on tropical cyclone track and intensity forecasts are investigated using the 2-way Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS® ). The ocean component is the NRL Coastal Ocean Model (NCOM), and the 2-way coupling is through the Earth System Modeling Framework (ESMF). Three atmospheric nested grids (45 km, 15 km, and 5 km) and two ocean nested grids (5 km and 1.67 km) are used in COAMPS to simulate the 2005 Hurricane Katrina, with the atmospheric inner-most mesh following the cyclone center. The atmospheric initial and boundary conditions are from the Navy Operational Global Atmosphere Prediction System (NOGAPS) or the NCEP Global Forecast System (GFS). The ocean initial and boundary condition are from global NCOM. The results suggest the Katrina tracks and intensities are very sensitive to various choices of initial and boundary conditions. Significant differences are shown in the COAMPS track and intensity forecasts when the tropical cyclone bogus is turned off. Detailed results on the environmental flow patterns and structure near the storm center at the initial time and comparisons of different boundary conditions will be presented at the conference.