A Supercell thunderstorm brought accumulating hail to east-central Colorado on 14 May, just east of I-25 and north of Castle Rock. The hail on the ground was observed by GOES-16 products. The 0.5 km, 0.64 um VIS revealed the hail swath quite well as the storm advanced east (Fig 1). The Day Cloud Phase Distinction RGB, which utilizes the 0.64 um channel (green) in addition to the 1.6 um NIR channel (blue) and 10.3 um IRW channel (red), made the hail swath even more apparent (Fig 2). The ice is highly reflective in the VIS and lowly reflective in the 1.6 um channel, like the thunderstorm clouds. However, unlike the clouds, the hail swath is warm because it is being sensed at the surface. The result is a hail swath (dark green) that contrasts nicely with the surrounding clouds (yellows, reds).

Figure 1: 14 May 2018 GOES-16 5-min 0.64 um VIS. Hail swath is apparent north of Castle Rock. Full res

Figure 2: 14 May 2018 GOES-16 5-min Day Cloud Phase Distinction RGB. Hail swath is apparent north of Castle Rock (green). Full res

Bill Line, NWS