Three Body Scatter Signature producing uncertainties on Doppler radial velocity structures

The Romanian National Meteorological Administration (RNMA) radar network integrates five S-band and four C-band radars. The observation of convection in Romania through the Doppler radar network offered a new perspective in understanding the climatologic risk of certain regions and mesoscale environments. The highly organized convective systems, like supercells, are better observed and their subsequent threat can be better anticipated during nowcasting process using useful radar tools like mesocyclones (MESO) and tornadic vortex signature (TVS) detection algorithms. However, it is obvious that these tools can not be used without a subjective validation, due to the associated errors and limitations of radar observations. In this paper are presented several cases where the presence of large hail, producing a radar artifact named Three Body Scatter Siganture (TBSS), disturbed the velocity field detected by the radar; thus unreal mesocyclonic and tornadic vortex signatures were generated; in some of the cases large hail and weak tornado were reported, so the presence of TBSS was a challenge for the nowcasters. There are also presented characteristics of all TBSS detected in the last three years with the Romanian radar network and are described their different structures as seen with S and C band.