The Spatial Area and other Attributes of Overshooting Tops as Indicators of Hail Size as Viewed by GOES16

Each year hail contributes to most of the aggregated loss from severe weather-induced property and crop damages in the U.S. Low-altitude radar coverage is also poor in some areas of the U.S., which frequently yields hail size overestimation. Prior work investigating overshooting tops (OTs) using satellite data has shown that overshooting top area (OTA) is correlated with tornado intensity. This work builds off the OT-tornado research to explore possible relationships between OT characteristics and hail size observed at the ground. This relationship could help to alleviate the deficiencies of current hail size estimation methods.

Hail reports are assigned to 0.5° x 0.5° latitude-longitude grid cells across the contiguous U.S., from which the largest hail report per hour per grid cell is selected. An OT detection algorithm is applied to the selected hail reports to find the nearest OT to the report. OT characteristics including OTA, brightness temperature difference (BTD), and overshooting top depth (OTD) are considered for relationships with observed hail size at the ground.

Results show that OTA decreases linearly and OTD increases linearly with increasing hail size. These findings are most pronounced from April-September (warm season) in the northern and southern Great Plains regions. These results could be helpful for forecasters issuing severe weather warnings and, more specifically, identifying the likelihood for severe hail when radar coverage is poor or not available. Future work will involve modeling using CM1 to delve into physical reasoning behind these findings.