Acceleration of tropical cyclones as a proxy for extratropical interactions: synoptic-scale patterns and long-term trends

Abstract. It is well known that rapid changes in tropical-cyclone motion occur during interaction with extratropical waves. While the translation speed has received much attention published literature, acceleration not. Using a large data sample of Atlantic tropical cyclones, we formally examine composite synoptic-scale patterns associated tangential and curvature components their acceleration. During periods acceleration, cyclone moves poleward between an upstream trough downstream ridge developing wave packet. The two systems subsequently merge manner consistent transition. prominent promotes recurvature cyclone. In contrast, deceleration or near-zero located directly Locally, this arrangement takes form cyclone–anticyclone vortex pair. On average, peaks 18 h prior to transition, while at recurvature. These findings confirm cyclones mediated by baroclinic Furthermore, tails distribution show robust reduction over past 5 decades. We speculate these trends may reflect shift weakening Rossby