Study of The Impact of NASA Global Hawk Unmanned Aircraft Dropwindsonde Observations on Tropical Cyclone Track, Intensity and Structure

The NOAA Sensing Hazards with Operational Unmanned Technology (SHOUT) program aims to demonstrate and test a prototype Unmanned Aircraft Systems (UAS) concept of operations that could be used to mitigate the risk of high impact weather and the potential of observing gaps in satellite data. As part of the SHOUT program, NOAA and NASA are collaborating to deploy NASA's Global Hawk unmanned aircraft to investigate how to maximize the impact of UAS observations for the analysis and prediction of tropical and extratropical weather systems in global and regional numerical models. The current study focuses on tropical cyclones (TCs) and utilizes NOAA's Hurricane Ensemble Data Assimilation System (HEDAS) and Hurricane Weather Research and Forecasting (HWRF) modeling system.

HEDAS was developed as a research tool to assimilate high-resolution observations in TCs. It combines a state-of-the-art square-root ensemble Kalman filter, NOAA's HWRF modeling system, and a storm-relative processing capability for a variety of observation types. Since 2010, HEDAS has been run in near real time on the NOAA Hurricane Forecast Improvement Project's Jet supercomputer to assimilate observations from NOAA and Air Force Reserve research and reconnaissance flights (GPS dropwindsondes, flight level data, Stepped-Frequency Microwave Radiometer winds, and Doppler radar data), satellite atmospheric motion vectors, retrieved thermodynamic profiles from the Atmospheric InfraRed Sounder (AIRS) on NASA's Aqua satellite and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Positioning System Radio Occultation (GPSRO), nearby rawinsondes, and Aircraft Communications Addressing and Reporting System (ACARS) on commercial aircraft.

In addition to the standard observation platforms assimilated in HEDAS mentioned above, the impact of GPS dropwindsonde observations from the Global Hawk aircraft is investigated here. Preliminary results from experiments conducted with cases from 2013 and 2014 will be presented to illustrate the potential impact of these additional observations on model forecasts of TC track, intensity and structure. Some potential ideas for optimizing their assimilation for TCs will also be discussed.