Comments on “A Multiscale Numerical Study of Hurricane Andrew (1992). Part I: Explicit Simulation and Verification”

Abstract

In this study, the inner-core structures of Hurricane Andrew (1992)are explicitly simulated using an improved version of the Penn State-NCARnonhydrostatic, two-way interactive, movable, triply nested gridmesoscale model (MM5). A modified Betts-Miller cumulus parameterizationscheme and an explicit microphysics scheme were used simultaneouslyto simulate the evolution of the larger-scale flows over the coarser-meshdomains. The intense storm itself is explicitly resolved over thefinest-mesh domain using a grid size of 6 km and an explicit microphysicspackage containing prognostic equations for cloud water, ice, rainwater,snow, and graupel. The model is initialized with the National Centersfor Environmental Prediction analysis enhanced by a modified moisturefield. A model-generated tropical-storm-like vortex was also incorporated.A 72-h integration was made, which covers the stages from the storm�fsinitial deepening to a near-category 5 hurricane intensity and thelandfall over Florida.As verified against various observations and the best analysis, themodel captures reasonably well the evolution and inner-core structuresof the storm. In particular, the model reproduces the track, theexplosive deepening rate (>1.5 hPa h�|1), the minimum surface pressureof 919 hPa preceding landfall, the strong surface wind (>65 m s�|1)near the shoreline, as well as the ring of maximum winds, the eye,the eyewall, the spiral rainbands, and other cloud features. Of particularsignificance is that many simulated kinematics, thermodynamics, andprecipitation structures in the core regions compare favorably toprevious observations of hurricanes.The results suggest that it may be possible to predict reasonablythe track, intensity, and inner-core structures of hurricanes fromthe tropical synoptic conditions if high grid resolution, realisticmodel physics, and proper initial vortices (depth, size, and intensity)in relation to their larger-scale conditions (e.g., SST, moisturecontent, and vertical shear in the lower troposphere) are incorporated.