Detection of the Presence of Tornadoes at the Center of Mesocyclones: A Simulated Doppler Velocity Study

Simulations are conducted to investigate the detection of the Doppler velocity tornado signature (TS) and tornadic vortex signature (TVS) when a tornado is located at the center of the parent mesocyclone. If the tornado's signature is a TS or TVS depends on whether the tornado's core diameter is broader or narrower than the radar's effective beamwidth, respectively. The investigation includes three radar effective beamwidths, two different-sized mesocyclones, and six different-sized tornadoes. Each tornado size has 10 different maximum tangential velocities assigned to it to represent a variety of strengths. The tornado/mesocyclone centers are positioned from 10 to 150 km from the radar. The results indicate that (1) azimuthal shear at the center of the mesocyclone increases as the associated tornado gains strength before a TS or TVS appears, (2) smaller tornadoes need to be much stronger than larger tornadoes at a given range for a signature to appear within the mesocyclone (as expected), and (3) when the tornado diameter is wider than about one quarter of the mesocyclone diameter, the TS or TVS associated with a given mesocyclone appears when the tornado has attained about the same strength regardless of range.