Thursday, 6 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
This study presents an integrated damage, visual, and radar analysis of the EF5 Moore Oklahoma tornado that occurred on 20 May 2013. Characteristics of the damage path and low-level tornado wind field will be shown based on detailed ground and aerial surveys. Tree fall reveals highly convergent surface flow over the majority of the damage path. At times, the convergent flow is observed at radii less than that of the condensation funnel. A photogrammetric analysis of still photos and video shows that the damaging winds extend well beyond the condensation funnel location. The condensation funnel often coincides with the EF1, EF2, and EF3 isopleths. Observations of the tornado debris signature (TDS) by the Twin Lakes Weather Surveillance Radar (KTLX) 1988 Doppler (WSR-88D) will be presented. The TDS is not a good indicator of tornado intensity just after tornadogenesis. The spatial relationship between the TDS, condensation funnel, and damage path will be highlighted. An analysis of the area encompassed by the respective EF-scale isopleths will be shown to quantify damage risk. The area of successively weaker EF-scale categories exponentially increases. These results will be compared to other well-surveyed EF5 tornadoes. A comparison is made between independent ground and aerial surveys that rated 4039 structures along the entire damage path. The aerial survey produces a low bias in EF0 and EF1 ratings. No apparent bias is observed in the EF2-4 categories. It is not possible to draw definitive conclusions concerning the small number of EF5 rated structures. Based on these observations, recommendations for future aerial survey strategies will be discussed.
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