Thursday, 9 November 2006: 4:45 PM
St. Louis AB (Adam's Mark Hotel)
High-resolution dual- and single-Doppler mobile radar observations collected by the Doppler on Wheels (DOW) radars within several supercells are analyzed to determine the dynamic processes responsible for maintaining tornadic rotation at low levels. The circulation/vorticity budgets surrounding two tornadoes lasting 20 and 47 minutes (according to NCDC survey records) are compared to those of two other tornadoes with lifetimes under 5 minutes in order to assess the processes promoting or disrupting the continuous convergence of angular momentum.
Storm morphology at the time of tornado dissipation is also examined. Both of the long-lived tornadoes and their associated mesocyclones dissipate after a forward surge of the rear-flank gust front and cyclic low-level mesocyclogenesis occur. Both of the short-lived tornadoes dissipate within well-developed low-level mesocyclones that persist much longer than the tornadoes themselves, and the dissipation occurs in the absence of a significant rear-flank gust front surge or cycling mesocyclone.
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