Some Considerations for the Use of High-Resolution Mobile Radar Data in EF-Scale Assessments

An ever-increasing number of mobile radar datasets of tornadoes presents some unique opportunities for those who survey tornadoes and are involved in the EF-scale rating process. Some of the issues involved with the direct use of high-resolution, near-ground mobile radar observations of tornadoes in the intensity determination process include uncertainties in the location of scatterers contributing most to the returned signal, inconsistencies in the time scales of the observations and EF-scale wind estimates, and statistical errors in the estimates calculated from the measurements; these issues result in radial velocity estimates that may over- or under-estimate the EF-scale-equivalent wind speeds. Several recent examples of close-range observations of violent tornadoes observed by a rapid-scan, polarimetric, X-band mobile radar (RaXPol) are used to illustrate these points. Polarimetric radars provide several advantages compared to single-polarization radars when estimating the wind field within tornadoes, including reduced radial velocity error variances in the tornado debris cloud and the calculation of differential radial velocity, the latter of which, given its tendency to be greater in magnitude in areas of low co-polar cross-correlation coefficient and high spectrum width, may have utility in identifying ongoing tornadoes.