Optimization of Tropical Cyclone Data Assimilation for Combined WSR-88D and Aircraft Observations

The National Weather Service (NWS) operates over 150 WSR-88D (NEXRAD) radars across the United States. Studies such as Dong and Xue (2012) have shown positive impacts on tropical cyclone analyses and forecasts from assimilating these data into regional forecast models. This study will examine how assimilating WSR-88D data in addition to conventional observations impacts the 1800 UTC analysis of Hurricane Matthew (2016) on October 7 when Matthew was a Category 3 hurricane, 21 hours before it made landfall in Cape Romain, SC. Observations for this experiment include volume scans from the Jacksonville, FL (KJAX) WSR-88D radar and data from the NOAA WP-3D hurricane hunter aircraft. Data were assimilated into the Hurricane Weather Research and Forecasting (HWRF) model with NOAA/AOML/HRD’s Hurricane Ensemble Data Assimilation System (HEDAS), which uses tropical cyclone inner-core observations to initialize a high-resolution vortex. HEDAS is based on a serial implementation of the square root ensemble Kalman filter (EnKF). HWRF horizontal grid spacing of 9 (3) km in the outer (inner) domain is used for model advances while data are only assimilated in the inner domain. The impacts of assimilating WSR-88D data in addition to the standard aircraft data will be investigated for the analysis and forecast of Matthew.