Quantifying interagency differences in tropical cyclone best track wind speeds

Numerous agencies around the world perform post-season analysis of tropical cyclone position and intensity, a process described as “best tracking.” However, this process is temporally and spatially inhomogeneous because data availability, operational techniques and knowledge have changed over time and differ between agencies. The net result is that positions and intensities often vary for any given storm for different agencies. In light of these differences, it was imperative to analyze and document the interagency differences in tropical cyclone intensities. To that end, maximum sustained winds from different agencies were compared using data from the International Best Track Archive for Climate Stewardship (IBTrACS) global tropical cyclone dataset. Comparisons were made for a recent 5-year period to investigate the current differences, where linear systematic differences were evident. Time series of the comparisons also showed temporal changes in the systematic differences, which suggest changes in operational procedures. Lastly, initial attempts were made to normalize maximum sustained winds by correcting for known changes in operational procedures. The presentation will highlight the dataset used, methodology employed, and results that will ultimately demonstrate that a complete reanalysis of tropical cyclone intensities should be performed.