Simulations of Hurricane Katrina (2005) with the 0.125 degree finite-volume General Circulation Model on the NASA Columbia Supercomputer

Hurricane Katrina was the sixth most intense hurricane in the Atlantic with a minimum sea level pressure of 902 hPa. Katrina's forecast poses major challenges, the most important of which is its rapid intensification. Hurricane intensity forecast with General Circulation Models (GCMs) is very difficult because of their coarse resolution. With a breakthrough in computing power provided by the NASA Columbia supercomputer, Atlas et al. [2005] and Shen et al. [2005] have employed the ultra-high resolution finite-volume GCM (fvGCM), showing a remarkable impact on hurricane forecasts in 2004. The effects of increased resolution on intensity predictions of Katrina are shown in six 5-day forecasts at 0.25 ^o and 0.125^o resolutions. The 0.125^o track predictions are comparable to the 0.25^o, but the corresponding intensity forecasts are much better, bringing the center pressure much closer to observations with differences of only ± 12 hPa. Moreover, in the runs initialized at 1200 UTC 25 AUG, the 0.125^o produces a more realistic intensification rate. Simulated near-eye wind distributions are in better agreement with the AOML high-resolution (0.052^o) wind analysis data. In addition, the first 5-day global ultra-high resolution simulation with the convection parameterization (CP) disabled is successfully performed, representing the intensity evolution and near-eye wind structure better than the control run with CP.