Analysis of Dual Polarization Radar Detection of Tornado Typhoon Rainband in Danzhou and Tunchang in Hainan Province
The radar data of Haikou dual polarization Doppler during the tornado processes in Tunchang County and Danzhou City of Hainan on 29 August 2019 are analyzed. The tornadoes occurred in a convective storm in the typhoon rain belt about 370 km to the right of Typhoon Podul. Both tornado occurrences were related to the mergering of the storms. One occurred at 12 min before the mergering of the storm cells, and another occurred at 5 min after the storm cells merged. The merger of the cell led to enhancement of the storm reflectivity with the storm height increasing, and the cyclone in the storm strengthened rapidly. Tornadic vortex signature (TVS) was detected during two tornadoes, and the time of detection of TVS was 27 min and 5 min earlier than the time of the tornadoes. Corresponding to the position of the TVS before the tornado occurred, the correlation coefficient (CC) value did not change. When the tornado occurred, the CC value of the position of the TVS suddenly decreased to below 0.8, and the low-value of the CC continued for more than 20 min after the tornado occurred. Both tornadoes had the rear storm cells merged. The tornado occurred at the rear of the main storm cells at the junction where the two storm cells merged.