Interaction of an Idealized Cyclone With a Wavy Midlatitude Jet

Abstract

Numerical weather prediction model forecasts of the Rossby wave packets (RWP) initiated from the interaction of a tropical cyclone and a midlatitude jet stream are often characterized by decreased accuracy and lowered forecast skill. Factors influencing the level of interaction between a tropical cyclone (TC) and a midlatitude jet depend on the size, strength, and location of the TC relative to the jet, along with the meridional extent, wave pattern, and speed of the jet, especially when interacting with an upstream trough. This study uses a bare- bones (quasi-geostrophic) model to simulate and analyze the evolution of RWPs originating from the interaction of an idealized, constant-shape TC with a prescribed stationary wave pattern in a mid-latitude jet. The goal of this study is to map out the sensitivity of the TC’s downstream impacts on the jet to the TC’s initial position, the width and the degree of initial waviness of the jet, as well as the relative strength of the jet and the TC. Our model setup is based on earlier idealized studies of interactions of the midlatitude jet with topography which offer an explanation of the nonlinear dynamics behind zonal and blocked mid-latitude flow regimes. The TC is to be included in the overall system as a singular vortex (SV), which provides unambiguous separation of the vortex field from the ambient field and the separation between the background flow and RWPs generated by the SV, with RWPs created from this interaction leading both to the SV’s self-propagation and to the downstream perturbations of the jet.