Preprints
https://doi.org/10.5194/wcd-2021-4
https://doi.org/10.5194/wcd-2021-4

  19 Jan 2021

19 Jan 2021

Review status: this preprint is currently under review for the journal WCD.

Acceleration of Tropical Cyclones As a Proxy For Extratropical Interactions: Synoptic-Scale Patterns and Long-Term Trends

Anantha Aiyyer and Terrell Wade Anantha Aiyyer and Terrell Wade
  • Department of Marine, Earth and Atmospheric Sciences, North Carolina State University

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

Anantha Aiyyer and Terrell Wade

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2021-4', Anonymous Referee #1, 07 Feb 2021
  • CC1: 'Comment on wcd-2021-4', G. Zhang, 12 Feb 2021
  • RC2: 'Comment on wcd-2021-4', Anonymous Referee #2, 21 Feb 2021

Anantha Aiyyer and Terrell Wade

Anantha Aiyyer and Terrell Wade

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Short summary
Using a large sample of Atlantic tropical cyclone tracks, we diagnose the mean circulations in the extratropics that are associated with rapid changes in the storm speeds. We show that rapid accelerations and decelerations are associated with distinct phasing between the tropical cyclone and weather waves of the extratropics. We also show that over the past 5 decades, rapid acceleration and deceleration of tropical cyclones have reduced in magnitude.