Recent advancements in dynamical tropical cyclone track predictions

Summary

Considerable advancements have recently been made in understanding tropical cyclone motion. Based on these new understandings, the requirements for accurate tropical cyclone motion prediction with dynamical models can be specified. Four issues related to dynamical track prediction are the initial specifications of the environmental wind field, the symmetric vortex and the asymmetric vortex structure, as well as the adequacy of the models to predict the time evolution of each of these three 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 barotropic model to provide skillful track forecasts to 48 h retrospectively substantiates that tropical cyclones motion is governed by barotropic dynamics to first order. Limited-region baroclinic models are demonstrated to have many of the numerical characteristics, physical process representations, and initial condition specifications that will be required to properly predict tropical cyclone tracks. In particular, the semioperational Geophysical Fluid Dynamics Laboratory model most closely addresses all of the above issues, and has demonstrated potential for markedly improved tracks for a small sample of cases. Finally, the inclusion of some aspects of tropical cyclone structure in the initial conditions of global baroclinic models has improved their track predictions. Thus, the outlook is for a significant improvement in dynamical track predictions.