The first summer of observations for the UPLIGHTS campaign took place from May – Aug 2012. Drought conditions limited the total number of storms in the area as well as the type of storms favorable for upward lightning. Only two upward flashes were captured. However, the operations team aggressively pursued storms throughout the region to obtain captures of normal downward cloud-to-ground flashes and cloud flashes. A total of 282 flashes were captured on high-speed video, including the two upward flashes.
Preliminary analysis of the two upward flashes indicates that a nearby +CG flash triggered each. The first upward flash occurred on 7 Jun 2012 at 21:58:35 UT. The image below shows the flash as captured by a digital still camera. The triggering +CG flash is visible in the left side of the image and a weak upward leader from Tower 7 is visible on the right side of the image. NLDN data indicated a +70.6 estimated peak current +CG return stroke occurred 13 km north of Tower 7 at 21:58:35.071.
The second upward flash occurred on 10 Jun 2012 at 03:33:03 UT. The image below shows the flash as captured by a digital still camera. The triggering +CG flash attached to Tower 1 in the left side of the image and an upward positive leader then developed from Tower 8 in the right side of the image. NLDN data indicated a +124 kA estimated peak current +CG return stroke occurred 6.3 km north-northwest of Tower 8 at 03:33:03.109. However, since the +CG attached to Tower 1, the exact location is known and was actually 5 km north of Tower 8. This is the first case that I am aware of in which a downward +CG triggering flash attached to a tower.