Evaluation of Numerical Models surface wind field structure during rapid changes TC cases using H*Wind and HEDAS

Over the last few decades, forecasts of tropical cyclone (TC) tracks have improved significantly, largely as a result of the improvements in large-scale numerical forecast models and satellite observations, but relatively little progress has been made in our ability to predict hurricane intensity in terms of minimum sea level pressure, surface wind structure, or amount of precipitation. Important attributes of the surface wind structure consist of peak surface wind, radial and azimuthal distributions of the horizontal wind, and how they evolve over time. TCs that undergo rapid intensification (RI) or weakening (RW) are of great interest since rapid fluctuations in intensity are accompanied by rapid changes in the surface wind structure.

Intensity forecast models struggle to predict adequate TC surface wind fields. An evaluation of the model wind field evolution during rapid intensification cases will be presented. We compare the model wind field with the Hurricane Research Division's Hurricane Wind Analysis System (H*Wind) and HWRF Ensemble Data Assimilation System (HEDAS) to evaluate the performance of the model in predicting peak winds, important wind thresholds, such as 34- and 64-kt wind radii, and integrated kinetic energy. HEDAS assimilates hurricane inner-core observations for high-resolution vortex initialization. HEDAS is based on a serial implementation of the square root ensemble Kalman filter.