Evaluation Of The HWRF Radius Of Maximum Wind Using Doppler Radar Analyses

The radius of maximum wind (RMW) is a key kinematic and dynamic metric of a tropical cyclone's structure. It is typically estimated by aircraft reconnaissance flights and used by forecasters to estimate impacts from wind and storm surge. Along with the estimated peak wind and central pressure the RMW is often used to initialize numerical hurricane models, including the operational HWRF model. Kinematically it is a key parameter in describing the size of a tropical cyclone vortex. Dynamically it typically represents the radius of maximum pressure and vorticity gradients in the vortex, and coupled with the peak axisymmetric mean wind it's inertial stability. Given the significance of the RMW as a metric for tropical cyclone structure and dynamics it is a key parameter, along with the peak wind to evaluate numerical forecasts of tropical cyclone structure. In this study we compare estimates of the RMW from three-dimensional Doppler radar analyses generated during 146 NOAA WP-3D missions into over 37 Atlantic and East Pacific tropical cyclones from 2008-2015 to those of the operational HWRF model forecasts of those same storms. Comparisons will be made of the observed to the numerical model derived probability distribution of RMW estimates to determine model RMW biases. We will also look at comparisons of the observed versus the model analyzed and forecast RMW probability distributions to determine whether the biases are caused by the model initialization or other factors.