Role of large scale forcing and parameterizations on the modeling of Hurricane Karl genesis

Rapid intensification processes and genesis in the context of tropical systems is one of the most challenging topics in the current field of numerical modeling of tropical cyclones. Within this area of research, the problem of parameterizing microphysical processes and cumulus convection becomes of critical importance for the success of numerical forecasts, especially concerning trajectory and intensity of tropical disturbances. Furthermore, reliable and sufficiently accurate initial (IC) and boundary conditions (BC) from global models are a crucial ingredient for the quality and accuracy of the NWP results. This paper, therefore, aims to tackle those topics with regard to the genesis of hurricane Karl, its evolution and rapid intensification phases (September 2010) as they were observed during the PREDICT-GRIP-IFEX field campaigns. Two distinct IC and BC datasets (ERA-Interim and ECMWF Integrated Forecast System), as well as various convective and microphysics parameterization are used for high-resolution simulations with the Weather Research and Forecasting model. Their impact on the spatio-temporal structure of predicted convective fields is compared to Karl observations from a geostationary imager, airborne precipitation radar, CloudSat data, and dropsondes. Results are presented and discussed.