Impact of Global Hawk Dropsondes on Tropical Cyclone Analyses and Forecasts

The impacts of Global Hawk (GH) dropsonde data on tropical cyclone (TC) analyses and forecasts are examined over a composite sample of missions flown during the NASA Hurricane and Severe Storm Sentinel (HS3) and the NOAA Sensing Hazards with Operational Unmanned Technology (SHOUT) field campaigns. An ensemble Kalman filter is employed to assimilate the dropsonde observations at the vortex scale. With the assimilation of GH dropwindsondes, storms generally exhibit less position and intensity errors, a better wind-pressure relationship, and better structure in the analyses. The resulting track and intensity forecasts with all the cases generally show positive impact when GH dropsondes are assimilated. The impact of GH dropsondes is further explored with cases stratified for intensity change and presence of manned aircraft data. GH dropsondes demonstrate larger impact for non-steady-state TCs (non-SS; 24-h intensity change larger than 20 kt) than for steady state (SS) TCs. The relative skill from assimilating GH dropsondes ranges between 25-35% for either the position or intensity improvement in the final analyses overall, but only up to 10% for SS cases alone. The resulting forecasts for non-SS show higher skill for both track and intensity than SS cases. Additionally, GH dropsonde impact on TC forecasts varies in the presence of manned aircraft data. An increased intensity improvement at long lead times is seen when manned aircraft data are absent. This demonstrates the importance of designing flight patterns to strategically exploit the sampling strengths of the GH and manned aircraft in order to maximize data impact on TC prediction.