Multiple-Scale Interactions Affecting Tropical Cyclone Track Changes

Abstract

Tropical Cyclone (TC) track changes associated with Rossby wave energy dispersion are simulated in a shallow water primitive equation model with an initial field where a TC is located south of a subtropical high. An anticyclone east of the TC appears because of Rossby wave energy dispersion. The connection of the anticyclone with the subtropical high leads to a poleward TC track deflection. The TC eventually moves across the axis of the subtropical ridge. The formation of the track may be attributed to the nonlinear interaction between the subtropical high and the TC. This work validates the conceptual model proposed by previous observational research. The scenario of the nonlinear interaction between the TC and the subtropical high may also be modified through the influence of mesoscale vortices. The main modifications are (1) the anticyclone induced by energy dispersion of the TC weakens, (2) the connection between the anticyclone and the subtropical high is delayed, and (3) the TC shifts more westward and does not move across the ridge axis. We propose that some of the mesoscale vortices are axisymmetrized by the TC and results in an increase in TC size which modifies the properties of the energy dispersion. The phase and group speeds decrease and produce a simulated track deflection to the left compared to the simulation without mesoscale vortices. Our numerical results demonstrate that multiple scale nonlinear interactions have an essential role in influencing TC track changes.