Observations of a Tornadic Storm with the Midlothian Dual-polarization X-BAND Radar

On April 24 2015 severe weather swept through the Dallas – Fort Worth area. A storm line with associated winds in excess of 100 km/h and an embedded tornado traveled along US67 towards the town of Midlothian. This storm and associated tornado were observed at close range and with high temporal resolution (less than 1 minute updates) by the dual-polarization X-band radar deployed in that town as part of the CASA-DFW radar network. This paper will present selected X-band dual-polarization radar measurements obtained during that storm event. Specifically, the paper will show extended Doppler velocity and storm relative Doppler velocity measurements showcasing the rotation signature, quantitative precipitation estimates obtained during the storm life, and enhanced-sensitivity, attenuation-corrected reflectivity measurements. The sensitivity enhancement is achieved using a combination of co-polar autocorrelation and cross-correlation derived reflectivity values prior to attenuation correction, as shown in the image below. The top row shows Doppler velocity and attenuation corrected reflectivity (threshold at 0 dB SNR, where SNR is obtained from the usual horizontal polarization co-polar autocorrelation function). The bottom row shows the corresponding Doppler velocity (now relative to storm motion to better showcase rotation) and sensitivity-enhanced, attenuation-corrected Reflectivity for the same case in the top row.