Particular emphasis will be on a unique assessment of three supercells which affected the densely populated suburbs north of Toronto where two tornadoes touched down causing F2-rated damage. Numerous eyewitness accounts provided conflicting information on which supercells spawned the tornadoes. The sequence of tornado touchdowns was resolved using a detailed analysis linking the eyewitness accounts, YouTube videos, Google Street View, and radar outputs (Toronto and Buffalo reflectivity and Doppler data, and Toronto dual-polarimetric data). The results were both unusual and surprising, in that they debunked several key eyewitness accounts. Many of these modern-day tools, such as Street View, can be helpful for post-event damage surveys.
The RhoHV scans from dual polarimetric radar are able to detect tornadic debris signatures by measuring irregularly shaped objects. The debris fields of the two tornadoes were indeed detected on some of the RhoHV scans, albeit weakly on one tornado. The timing and locations of the RhoHV debris fields were compared to the independent analysis and found to match very closely, to within a few hundred metres. This helped confirm the accuracy of the independent analysis.
Dual polarimetric radar also shows some promise in discriminating between tornadic and non-tornadic supercells, namely in their ability to reveal some of the microphysical differences between them. This was especially true of the Aug 20th tornadic outbreak using the Toronto dual polarimetric radar, although it will not be explored in this paper. This underscores the importance of the independent analysis' results of the tornadic supercells in north Toronto.