Potential-Vorticity Bridge and Inner-Core Structural Change During Mature to Weakening Phases of Typhoon Neoguri (2025) Captured by Aircraft and Satellite Observations

Abstract Over two consecutive days in September 2025, a Japanese aircraft that reached the center of Typhoon Neoguri conducted observations during the typhoon’s mature and weakening phases. Dropsondes were launched at intervals of 5 min or less from approximately 14 km altitude to capture vertical profiles of the inner core and the environmental fields. In the mature phase, we observed a warm-core structure with warm-anomaly maxima in both the upper and lower troposphere in the eye, and a vertical shear of the tangential wind near the lower part of the warm-anomaly maxima. A combined analysis of the dropsondes and satellite-based atmospheric motion vectors in the low-level eye revealed a potential-vorticity bridge structure; this is the first time that such a structure is detected in tropical-cyclone observations over the western North Pacific. In the weakening phase, the lower part of the warm-anomaly maxima disappeared, the central pressure increased, and the profile of equivalent potential temperature in the eye was vertically uniform. The temporal changes of the inner-core structure during the aircraft observations are discussed. We highlight the importance of the synergetic utilization of data from aircraft and satellites for a better understanding of inner-core dynamics.