Modeling interaction of a tropical cyclone with its cold wake

Abstract

This study first examines the tropical cyclone (TC) intensity response to its cold wake with time-invariant, stationary cold wakes and an uncoupled version of COAMPS-TC, and second with simulated cold wakes from the fully coupled version. The objective of the uncoupled simulations with the time-invariant cold wake is to fix the thermodynamic response and to isolate the dynamic response of the TC to the cold wake. While the stationary TC over a cold wake has an immediate intensity decrease, the intensity decrease with a long trailing wake from the moving TC was delayed. This time delay is attributed to a ‘‘wake jet’’ that leads to an enhanced inward transport of moist air that tends to offset the effect of decreasing enthalpy flux from the ocean. In the fully coupled version, the TC translating at ¯¹ generated a long trailing cold wake, and again the intensity decrease was delayed. Lagrangian trajectories released behind the TC center at four times illustrate the inward deflection and ascent and descent as the air parcels cross the trailing cold wake. The momentum budget analysis indicates large radial and tangential wind tendencies primarily due to imbalances among the pressure gradient force, the Coriolis, and the horizontal advection as the parcels pass over the cold wake. Nevertheless, a steadily increasing radial inflow (wake jet) is simulated in the region of a positive moisture anomaly that tends to offset the thermodynamic effect of decreasing enthalpy flux.