An Expanded VVP Technique to Resolve Primary and Environmental Circulations in Hurricanes

Abstract

Abstract An expansion of the volume velocity processing (VVP) single-Doppler radar analysis method is presented for use with hurricanes. The so-called hurricane VVP (HVVP) method connects the estimated coefficients of a second-order Taylor series expansion of the wind field to the kinematic properties of a wind model that assumes axisymmetry of the tangential and radial wind and a vertically varying environmental flow. HVVP extracts the average radial profiles of these wind components between 1.0- and 3.5-km altitudes along with two parametric indicators of axisymmetry. A new method is thus provided to simultaneously monitor the trends in lower-tropospheric hurricane and environmental winds near landfall. In addition, novel kinematic approximations between the radial variations of the tangential and radial winds developed for HVVP will be of interest to the hurricane research community. Estimates of bias caused by expected average deviations of the true wind from the assumed wind model suggest that the HVVP method is capable of estimating the maximum wind magnitude of the primary circulation and the environmental wind components to within ~10% and ~2 m s−1 accuracy, respectively, while the radar is located beyond a distance of 2.5 times the radius of maximum wind from the circulation center. An application of the HVVP method to a case study of Hurricane Bret (1999) shows good agreement between the results from two WSR-88D radars located on opposite sides of the storm and a pseudo triple-Doppler radar wind analysis that included NOAA airborne Doppler radar observations.