Tropical cyclone inner-core data assimilation study using the GSI-based hybrid data assimilation system

In collaboration with research and operational centers, the Developmental Testbed Center (DTC) works toward the improvement of tropical cyclone forecasts through testing and evaluating the current operational and developmental techniques for tropical cyclone initialization. Recent work has been performed in the framework of the 2014 operational Hurricane Weather Research and Forecast (HWRF) model. This system uses the one-way hybrid data assimilation technique in its Gridpoint Statistical Interpolation (GSI) data assimilation system by ingesting coarse resolution global ensembles. First, the DTC examined various aspects of this HWRF system, with a focus on data assimilation for tropical cyclone forecasts. Experiments have been performed for multiple tropical storm cases to study the impact of numerous configurations on hurricane forecasts, including the benefit of applying a high-resolution regional HWRF ensemble for the vortex scale data assimilation and the individual impacts of vortex initialization and data assimilation on forecasts. The DTC then advanced the study by applying the two-way hybrid data technique into the inner core data assimilation. Data impacts were evaluated by comparing data assimilation runs using the one-way hybrid and two hybrid techniques. This paper will present results from these tests. The potential of and issues related to tropical cyclone data assimilation for the inner core area will also be discussed.