1. PECAN CSWR interest IOP 20 5/6 July 2015 MCS in SE South Dakota

2. Overview Map * Dows are blue disks * Dual lobes are 30 o min crossing: Green Blue: D8-D7 Dark Blue: D7-D6 * Light green polygons are where CI occurred and moved ENE. * Darker green polygons are where CI started. * Low-level blockage is shown as grey sectors for each radar. Dow7 blockage is by cab. D6 D7 D8

3. Dual Map for Gust Front and Kink Gust fronts (pink at 04:35, brown at 04:50) showing occluded structure and kink. The kink (path shown as red arrow) developed vortices, shown later. Dow7 elevations malfunctioned after 04:50, remaining above ~20 deg until 05:51. The EF-0 tornado was obscured by attenuation. D6 D7 D8 04:35 04:54 04:50 04:35 EF-0 tornado ~ 05:37

4. DOW views of CI Simultaneous (03:58) views of the result of three different CI events ahead of gust front (DBM top, VEL bottom) for each radar at about the same time at elevation 1 o. Each is centered at about the same geographic location. The E-W line through center progressively initiated from W to E. DOW-8 DOW-6 DOW-7

5. DOW views of Gust Front approaching Simultaneous view of gust front (DBM top, VEL bottom) for each radar at about the same time at elevation 1 o. All are centered at about the same geographic location. DOW-8 DOW-6 DOW-7

6. DOW views of Gust Front near D8, D7 DOW-8 DOW-6 DOW-7 Simultaneous view of gust front (DBM top, VEL bottom) for each radar at about the same time at elevation 1 o. All are centered at about the same geographic location. D6 is severely attenuated. Small spinups may be present within kink just W of D7.

7. Maximum low-level wind at each radar Wind maxes listed below are circled in black on sweeps. Note different speed scale for D7. Dow-8: -26 at Z = 56m (05:05), then +30 m/s at Z=40m (05:10) both apparently caused by same translating feature. Dow-7: -27 m/s at Z=13 m. Dow-6: No significant winds. DOW-8DOW-7

8. Gust Front Kink with small vortices Kink with small vortices just within dual lobe for D8 and D7. Note that staggered unfolding in D8 at first time not well done on outbound side. DOW-8DOW-7 04:45 04:49

9. IOP20 good points 1.Occluded gust front 2.Kinks evolving 3.Main kink/occlusion may have caused tornado 4.Good CI events IOP20 bad points 1.Attenuation hurt dual and obscured tornado 2.Dow7 elevation malfunction