Do Tropical Cyclones Have a Steady Translation Under a Uniform Steering Flow?

Abstract

Changes in tropical cyclone (TC) movement are commonly attributed to those in the steering flow, beta effect, or topographic influences. However, a series of idealized simulations suggest that significant track deflections can still occur even under a steady steering flow on an f plane. TCs embedded in easterly flows of varying strength systematically deflect southward from the expected westward track when radiative effects are included. The resulting track deflection reaches approximately 200 km in some experiments over a 144-hr period, comparable to typical 72- to 96-hr forecast errors in global numerical weather prediction model. A potential vorticity tendency analysis reveals that the deflection primarily results from the diabatic heating and horizontal advection terms, each linked to asymmetries in the convection and wind fields, respectively. These asymmetries are initially triggered by vortex–flow interactions and further enhanced by radiative diurnal cycles. Our findings highlight the role of internal vortex asymmetries in modulating TC motion.