RECENT ADVANCEMENTS IN DYNAMICAL TROPICAL CYCLONE TRACK PREDICTIONS

Considerable advancements have recently been made in understanding tro pical cyclone motion. Based on these new understandings, the requireme nts for accurate tropical cyclone motion prediction with dynamical mod els can be specified. Four issues related to dynamical track predictio n are the initial specifications of the environmental wind field, the symmetric vortex and the asymmetric vortex structure, as well as the a dequacy of the models to predict the time evolution of each of these t hree components of the total wind field. Recently developed barotropic and limited-region or global baroclinic models are examined in terms of these issues. The capability of the Hurricane Research Division bar otropic model to provide skillful track forecasts to 48 h retrospectiv ely substantiates that tropical cyclones motion is governed by barotro pic dynamics to first order. Limited-region baroclinic models are demo nstrated to have many of the numerical characteristics, physical proce ss representations, and initial condition specifications that will be required to properly predict tropical cyclone tracks. In particular, t he semioperational Geophysical Fluid Dynamics Laboratory model most cl osely addresses all of the above issues, and has demonstrated potentia l for markedly improved tracks for a small sample of cases. Finally, t he inclusion of some aspects of tropical cyclone structure in the init ial conditions of global baroclinic models has improved their track pr edictions. Thus, the outlook is for a significant improvement in dynam ical track predictions.