A long-lived line of severe thunderstorms resulted in a broad swath of damaging winds across the Midwest on 10 August 2020. There were hundreds of severe wind reports associated with this derecho, including dozens in excess of 75 mph (significant severe). GOES-East captured the evolution of the complex from initial thunderstorm development over Nebraska through convective decay over Ohio.

A long, 10-min IR animation captured the full evolution of the thunderstorm complex, from 0611 UTC with initial development of thunderstorms over Nebraska, through 0201 UTC with weakening over Ohio/Indiana (Fig 1). Persistent cold cloud tops of <60C were analyzed along the leading edge of the MCS and in association with the severe storms, with cloud tops as cold as -80C sampled in the GOES imagery. NWS convective warning polygons and Local Storm Reports are shown as an overlay on the imagery.

Corresponding GLM Flash Extent Density imagery is shown in Figure 2, and is used to infer the locations of strongest updrafts, and updraft trends, within the broader complex. Periodic long flashes are also observed extending into the thunderstorm anvils, representing a lightning threat well away from the strong thunderstorms.

Corresponding MRMS composite reflectivity is shown in Figure 3 for comparison, and aligns with the regions of notable/persistent GLM activity and coldest cloud tops.

GOES-East VIS-IR Sandwich image combo (every 5-minutes) is shown as feature following zoom for the during the daytime of the 10th, following the derecho (Fig 4). The evolution of features within the thunderstorm line is made more apparent in the feature relative animation. The combination of texture in the VIS and brightness temperature information in the IR allows for easy diagnosis cloud top health and trends, including that of overshooting tops, gravity waves, overall texture, and above anvil cirrus plumes. Toward the end of the animation, cloud tops begin to warm, and texture becomes less abundant, indicating weakening convection.

GOES-East mesoscale sectors were available over the region, providing 1-min imagery for forecasters (Fig 5 and 6). The high temporal resolution, low latency imagery allows forecasters to more effectively track individual updraft trends in real-time vs the 5-min imagery.

A long (5-hour) 1-min VIS-GLMFED Sandwich animation covers a period of some of the most intense thunderstorm wind gusts, and connects visual texture trends with lightning trends (Fig 7).

Bill Line, NESDIS/STAR