Inter-Agency Consistency of Western North Pacific Tropical Cyclone Best-Track Data as a Function of Proximity to the Korean Peninsula and Intensity

Multiple agencies independently produce tropical cyclone best-track datasets for the western North Pacific, and these datasets are often regarded as interchangeable in coastal hazard applications. This study examined when this assumption holds. KMA, JMA, and JTWC data for 1977–2024 were matched by cyclone and observation time, and inter-agency differences were analyzed on a response surface defined by intensity and proximity to the Korean Peninsula. The mean absolute difference in maximum wind speed increased 4.6-fold, from 6.14 kt for tropical storms to 28.48 kt for the super-strong class, whereas center-position agreement within 0.1o increased from 16.6% to 68.1%. The relationship between distance and wind-speed difference also varied with intensity. The unadjusted slope was –0.27 kt per 1,000 km, whereas class-specific slopes increased from +0.02 to +3.35 kt per 1,000 km. Of 360 cyclones experiencing both intensity phases, 343 (95.3%) showed larger inter-agency differences during the stronger phase. Wind-speed ratios (JMA/JTWC) varied from 1.01 to 0.80 with intensity and also with distance within intensity classes, indicating that averaging-time conventions alone cannot explain the observed differences. These results suggest that inter-agency consistency varies conditionally with distance and intensity, both of which should be considered in best-track source selection.