Development of an Ensemble-Based Sensitivity Metric for Tropical Cyclone Hazard Forecasts

Since 1997, the National Hurricane Center (NHC) has conducted operational synoptic surveillance missions in the near-storm environments of TCs using the Gulfstream IV-SP jet aircraft (G-IV), with the goal of reducing track forecast errors and uncertainty for landfalling storms. Numerous targeting strategies have been utilized to identify where to deploy dropwindsondes that would produce the greatest reduction in error and/or uncertainty in subsequent forecasts (i.e., targeted observations). The current operational targeting is designed to reduce uncertainty in the steering wind, rather than identify where additional dropwindsonde observations will lead to improvements in specific aspects of the TC forecast, such as track, intensity, and other hazards. Recently, a new method has been developed to identify locations where supplemental observations would have the largest impact on TC track forecasts based on the ensemble-based sensitivity technique and has been used in the flight planning process by NHC since 2018. This research aims to expand the application of the ensemble-based sensitivity technique to TC intensity, maximum wind, and precipitation. Two case studies will be used to demonstrate the application of these new forecast metrics on forecasts of Hurricane Henri (2021) and Hurricane Ida (2021) initialized 2-3 days prior to landfall. Further, the chosen case studies have been sampled by a NOAA G-IV synoptic surveillance mission; thus, allowing for a comparison between the sensitive regions for these new metrics compared to the sensitive regions for the track metrics and the dropwindsonde deployment locations.