Impact of the Assimilation of Targeted HAB-Launched Dropsondes on Operational Tropical Cyclone Forecasts

The assimilation of atmospheric soundings collected by dropsondes released from reconnaissance aircraft have been shown to increase the accuracy of tropical cyclone intensity and track forecasts. These observations are expensive, however, and so are limited in number and region. StratoSolutions is developing two dropsonde delivery methods that are far more affordable to operate than existing aircraft platforms, even in remote areas: high altitude balloon (HAB) and high-altitude uncrewed aircraft. We will present research exploring the impact of HAB dropsonde observations over the eastern and central Atlantic toward improving tropical cyclone model forecasts there. This data is assimilated into MPAS-atmosphere model runs using a 3d-var scheme and compared to otherwise identical runs using no added observations. Model runs are initialized with raw GDAS analysis and cover an 80x80 degree regional domain centered on the Atlantic basin.

The predicted impact of dropsondes is calculated using Dr. Ryan Torn’s ensemble sensitivity method, and forecast improvement is evaluated across 7 days of model output. It is expected that reductions in forecast error could occur for model forecasts when this additional dropsonde data happens to coincide with ensemble-sensitive areas, but it remains to be seen whether these limited observations, possibly occurring hundreds of km away from active storms, will have as much impact as more targeted methods.