PGLM, Lightning Jump, and Quarter size hail


Example lightning jumps from just east of Denver CO at 2251 UTC. The image above shows the lightning jump feature (shaded purple), flash initiation density (FID; pink boxes) and the meteogram output information.  The top two panels are the sigma levels at which lightning jump occurs, and the bottom panel is the total flash rate from the PGLM.   The Tracking meteogram outline is the white circles encompassing the storm.  Two lightning jumps occur at 2249 and 2251 UTC.  The first jump occurs as the total flash rate from the PGLM reaches 10 flashes per minute (4 sigma level; anything above 2 sigma indicates a lightning jump according to Schultz et al. 2011), and the second jump occurs with the larger increase in total lightning from 5 flashes a minute to 15 flashes per minute (6 sigma).  The jumps are indicating increases in updraft strength and volume,and can be used as a metric in storm intensification.  Quarter size hail was reported approximately 20 minutes later at 2310 UTC.

*note the flash rates are likely higher with this storm because the LMA used in this case only had 5-8 sensors active at any given time.*