Recent Advances in Vortex-Scale Data Assimilation using NOAA/AOML/HRD's HWRF Ensemble Data Assimilation System (HEDAS)

The HWRF (Hurricane Weather Research and Forecast) Ensemble Data Assimilation System (HEDAS) has been developed at the Atlantic Oceanographic and Meteorological Laboratory's Hurricane Research Division within National Oceanic and Atmospheric Administration to address the vortex initialization problem for regional tropical cyclone modeling by assimilating high-resolution inner-core aircraft observations such as Doppler radar wind, dropwindsonde and flight level, and Stepped Frequency Microwave Radiometer (SFMR) surface wind speed data. The system has been run in real time for the 2010 and 2011, and retrospectively for the 2008 and 2009 hurricane seasons. Diagnostics from more than 70 cases demonstrate that aircraft observations can result in realistic vortex structures as well as well-represented wavenumber-0 and 1 components of the primary circulation. Deterministic forecasts initialized with these vortex analyses systematically outperform forecasts with similar model characteristics but with the operationally derived vortex.

In this talk, the overall performance of HEDAS for the 2008-2011 seasons will be briefly summarized. Following this summary, results from some ongoing research that addresses several issues relevant to vortex-scale data assimilation will be presented. Specifically, issues that are currently being investigated include impacts of storm-relative aircraft observations, optimal assimilation of thermodynamic observations, modifications to the radar super-observation processing to obtain high vertical data resolution in the boundary layer, and optimal vertical localization in the ensemble Kalman filter of HEDAS.