14.3
The 11 April 2001 Oklahoma tornado outbreak
PAPER WITHDRAWN
Kenneth A. James, NOAA/NWS, Norman, OK
During the early morning of 11 April 2001, several tornadoes, three that were rated F2, developed across southern Oklahoma and north Texas, resulting in one fatality, five injuries, and three million dollars in damage. Storm-scale features, such as rotational velocity, azimuthal shear, and mesocyclone diameter, associated with five of the tornadoes, were examined using Twin Lakes (KTLX) WSR-88D to determine the evolutionary characteristics and forecast value. Preliminary review of data showed that, these storms displayed atypical characteristics. Rotational velocity and azimuthal shear were strongest at 0.5 degrees and decreased upwards, while mesocyclone diameter increased. Also at 0.5 degrees, increases in azimuthal shear and decreases in mesocyclone diameter were more dramatic and better associated with the time leading up to, and during the beginning, of the tornadoes, than increases in rotational velocity, suggesting that these quantities need to be monitored closely by the warning forecaster, in addition to rotational velocity. Lastly, although more typical, considerable decreases in rotational velocity and azimuthal shear, along with increases in mesocyclone diameter, observed at 0.5 degrees, occurred in the middle of two of the five tornadoes, with the tornadoes continuing for another 15 minutes.
Session 14, Supercell and Tornadic Storms
Thursday, 15 August 2002, 1:30 PM-2:59 PM
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