Simulated WSR-88D measurements of low-reflectivity eyes associated with tornadoes

In the last several years, proximity radar observations of tornadoes by mobile Doppler radars have revealed details about the three-dimensional structures of tornado vortex, including spiral bands of reflectivity surrounding a low-reflectivity eye coincident with the center of the vortex. The low-reflectivity eye typically is not visible in WSR-88D observations because the radars are much farther away from tornadoes than are the mobile radars. Current-resolution reflectivity data collected by the WSR-88Ds have an azimuthal spacing of 1.0 deg and range spacing of 1.0 km for reflectivity.

The presence of the low-reflectivity eye would be more apparent if WSR-88Ds displayed finer-resolution data. To investigate this possibility, we use the high-resolution tornado numerical model of Dowell et al. (2005) and a simulated WSR-88D. Our approach involves decreasing (a) the azimuthal sampling interval from the conventional 1.0 deg to 0.5 deg, and (b) the range sampling interval from the conventional 1.0 km to 0.25 km. Simulations show that the reflectivity minimum inside the tornado core is more pronounced when WSR-88D data are collected at 0.5 deg azimuthal and 0.25-km range increments. At all ranges up to 100 km, fine-resolution data provide better depiction of the low-reflectivity eye in the tornado region than do current-resolution data.