Testing and evaluation of GSI-Hybrid 3DVAR for basin scale HWRF

Numerous studies have found that Hybrid-3DVAR tends to have positive impact on hurricane forecasting through incorporating flow dependent background error covariances from the ensemble perturbations to the 3DVAR static background errors. GSI (Gridpoint Statistical Interpolation)-Hybrid 3DVAR has been implemented in the global applications, showing improvement in the global forecast. Some positive impacts are also presented in some regional applications. At DTC, efforts are made to test the GSI-Hybrid in addition to code management / repository being setup for broader community usage. In this work, GSI-Hybrid is being tested for the basin scale HWRF, as part of the effort of building a GSI-Hybrid framework for operational HWRF implementations. In particular, cross-variances are being tested between different variables. Retrospective cases will be run and preliminary results will be presented.