"The DOW scanned over Greenfield at heights of about 30-50 m (100-160 feet) above the ground every 7 seconds, measuring Doppler velocities. The tornado was unusually small and was narrowing as it passed through town. It was moving very fast, at nearly 45 mph (20 m/s). The DOW directly measured Doppler velocities as high as 263-271 mph (118-121 m/s). DOW measurements are used to calculate peak tornado wind speeds using methods described in Wurman et al (2021a) and an upcoming American Society of Civil Engineering (ASCE) formal standard for determining tornado wind speeds from proximate radar measurements. DOW scientists calculate peak ground relative wind speeds, in a very narrow swath to the immediate east of the path of the center of the tornado circulation, as high as 309-318 mph (138-142 m/s). Since the tornado was very small and fast moving, these peak winds were likely experienced for less than a second at specific locations in town."