A Preliminary Modeling Analysis of Long-Distance Debris Transport by Tornadic Thunderstorms


Michael A. Magsig* Operational Support Facility
*2300 Marshall Ave, Suite 202, Norman Oklahoma, 73072
email: mmagsig@osf.noaa.gov, phone:(405) 366-6560 ext. 4268, fax: (405) 366-6557
John T. Snow College of Geosciences
Norman, Oklahoma
Louis J. Wicker Texas A&M University
College Station, TX


On 7 May 1995, debris items lofted by a tornado in north Texas and southern Oklahoma were transported distances of up to 190 km by a tornadic thunderstorm. As part of the VORTEX field project, Magsig and Snow (1998) used eyewitness accounts, radar data, and the debris deposition patterns to diagnose three modes of debris deposition in this event: 1) rear-flank deposition of debris leaving the rear flank of the storm in low-level storm-relative outflow associated with debris transport of ~ 25 km; 2) left-flank deposition in a reflectivity plume that descended from storm top around the left flank associated with debris transport of ~ 75 km; and 3) forward-flank deposition in a reflectivity plume that descended from storm top on the front flank associated with debris transport of ~ 150 km. The detailed observations of the 7 May 1995 event are used in the present study along with a high-resolution numerical simulation of a "generic" supercell to further investigate the possible debris trajectories within a supercell storm. Simulated debris trajectories through the model thunderstorm further supports the three modes of debris deposition documented in Magsig and Snow (1998). In the model storm, the main limiting factor of long-distance debris transport is whether the debris enters strong low-level updrafts (> 5 ms-1). Light debris that does not enter strong low-level updraft tends to circulate around the mesocyclone and leave the storm in the low-level storm-relative outflow after traveling relatively short distances. Light debris that enters strong low-level updraft travels to the top of the storm where it travels farther distances. While the preliminary modeling does not fully address all the complexities of debris transport, it will help direct future, more in depth, modeling studies.