NWC REU 2001
May 28 - August 3



Radar Signatures Associated with Atypical Tornado-Producing Thunderstorms in Oklahoma

Kristen Delack, Dave Andra, Mike Foster, and Dan Miller



During the early morning hours of 11 April 2001 a mini outbreak of tornadoes occurred across central and southern Oklahoma. The storms that affected the area were not as strong or as organized as traditional tornadic supercell thunderstorms, nor were they low-topped like tornadic mini-supercell thunderstorms. Most of the tornadoes produced that morning, however, were rated F1 or F2 on the Fujita scale and were responsible for one fatality, five injuries, and over $3.1 million in damage. This case and two similar cases were examined to determine radar characteristics of these atypical tornadic storms. Analysis of Doppler radar-retrieved data, such as mesocyclone rotational velocity, mesocyclone diameter, height of maximum rotational velocity, and height of storm top was performed. Results indicated that these storms do not fit the conceptual model for classic, LP, HP, or mini-supercells. Rather, they reflected characteristics of both mini- and traditional supercells. The strength and diameter of the mesocyclones were similar to those of mini-supercells, however, the storm top heights were substantially higher than those of mini-supercells. The height of maximum rotational velocity was much lower than that of both mini- and traditional supercells. Although this is a limited data set, the conclusion can be made that these storms represent another region of the tornadic storm spectrum that is not well documented.

Paper available upon request.