Extended Abstract (180K)10A.6
June 29, 2000 STEPS Supercell Storm: Relationships Between Kinematics, Microphysics, and Lightning
Kyle C. Wiens, Colorado State University, Fort Collins, CO; and S. A. Tessendorf and S. A. Rutledge
On June 29, 2000, during the Severe Thunderstorm Electrification and Precipitation Study (STEPS), a tornadic supercell occurred in western Kansas. This storm was well-sampled by at least two Doppler and one multi-parameter radar from 21:30 through 01:00 UTC. In addition, the location and intensity of the lightning activity in this storm was measured by the National Lightning Detection Network (NLDN) and the New Mexico Tech Lightning Mapping Array (LMA). Total flash rates in this storm exceeded 300 per minute, the vast majority of which were intra-cloud (IC). Cloud to ground (CG) flashes were almost all positive.
The first 20 minutes of lightning in this storm was composed entirely of relatively infrequent (less than 5 per minute) intra-cloud (IC) flashes between a main negative charge layer at 7 km MSL and a lower positive charge near 5 km. During this first 20 minutes, maximum updraft did not exceed 10 m/s and volume of updraft exceeding 10 m/s did not exceed 100 km^3.
At 21:50 UTC, a presumed upper positive charge layer began participating in IC flashes, and flash rates surged to near 50 flashes/min. Maximum updrafts surged to 20 m/s, but volume of updraft exceeding 10 m/s remained below 100 km^3. Following this first surge, the storm experienced several more surges in total lightning rate. For the most part, each lightning surge was accompanied by a surge in updraft volume.
Up until 23:30 UTC, this storm produced only a couple CG flashes and its volume of updraft exceeding 10 m/s grew steadily to near 700 km^3. At 23:30, positive CG flashes began in earnest and total flash rates surged to over 300 per minute. Coincident with this lightning surge, the volume of updraft exceeding 10 m/s rapidly increased from 700 km^3 to over 1500 km^3, and the storm produced an F1 tornado.
Supplementary URL: http://radarmet.atmos.colostate.edu/~kwiens/rm3/kwiens/SLS_2002.html
Session 10A, Results from the Severe Thunderstorm Electrification and Precipitation Study (STEPS) Experiment
Wednesday, 14 August 2002, 1:30 PM-3:00 PM
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