Evaluating the Impact of Dropwindsonde Observations from the Global Hawk UAS to Atlantic Hurricane Forecasts Using the Operational Hurricane WRF

An Observing System Experiment (OSE) is performed to evaluate the impact of targeted dropwindsonde observations from the Advanced Vertical Atmospheric Profiling System (AVAPS) instrument onboard the NASA Global Hawk aircraft to Atlantic hurricane forecasts using a version of the operational Hurricane Weather Research and Forecasting model. A total of 27 cases are investigated using observations taken from several flight campaigns into Atlantic hurricanes between 2012 and 2015, including Hurricanes Nadine (2012), Edouard (2014) and Cristobal (2014). Forecasts are also compared to near-identical experiments performed using the HWRF Ensemble Data Assimilation System (HEDAS), an ensemble-based data assimilation system developed by the Hurricane Research Division of the Atlantic Oceanographic and Meteorology Laboratory. The research is part of the Sensing Hazards with Operational Unmanned Aircraft Technology (SHOUT) program, which aims to test prototype Unmanned Aircraft Systems (UAS) concept of operations that could be used to mitigate the risk of high impact weather events, including hurricanes, through improved forecasting. It was found that when the model was run in fully cycling mode, observations led to modest improvements in track and MSLP intensity forecasts at later lead times, suggesting the importance of cycling using the operational HWRF model. It was also found that assimilating Global Hawk dropwindsonde observations did not lead to an improvement in the capturing of rapid intensity (RI) episodes or rate of weakening in the later stages of the forecasts.