The Center for Severe Weather Research (CSWR) deployed a Doppler On Wheels (DOW) radar and a Mobile Mesonet (MM) near the Elk City, Oklahoma tornado on 16 May 2017. The DOWs and MMs and deployable Pods are National Science Foundation (NSF) Lower Atmospheric Observing Facilities. DOW8 observed the tornado as it tracked from several miles southwest of Elk City, reaching maximum intensity about 1.5 miles west of Highway 6. Peak Doppler ground-relative winds about 600 feet above the surface were 195 mph at 00:08:07 UTC. (Current science doesn’t tell us whether winds were likely weaker or stronger than this at lower levels.) The delta-V across the tornado was 300 mph. The diameter (distance between maximum inbound and outbound winds) was 2750 feet. Peak winds of 195 mph occurred near the car lot between roads 33 and 34 about 2/3 mile north or road M. The tornado center was 0.78 miles west of Highway 6 at 00:09:35 UTC and still nearly as intense and with a similar diameter.. The tornado center crossed Highway 6 at 00:11:48. By 00:13:24 the tornado was 0.75 miles east of Highway 6 and had weakened. Delta-V was only 228 mph (peak ground-relative winds at this time have not yet been analyzed). At 00:16:12, peak ground-relative winds were approximately 170 mph, about 2.5 miles east of Highway 6. In the next few minutes the tornado weakened substantially, with delta-V only about 155 mph at 00:19:57 UTC, and only about 134 mph by 00:21 UTC. (remember, these are delta-V, not ground-relative velocity) The DOW was deployed on Highway 6 about 3600 feet north of road M. A MM measured winds of 30 m/s at that location at about 12 feet above the ground. This very preliminary next-day, we’re still in the field, analysis by Joshua Wurman and Karen Kosiba of CSWR. Navigation and wind values are approximate.

Elk City Tornado, 16 May 2017, at time of maximum DOW-measured winds of 195 mph between Roads 33 and 34 north of Road M, just after 00:08 UTC (17 May 2017 UTC). Peak Doppler: 195 mph Diameter of peak wind region about 2750 feet 2750 100 mph winds extend 3000 feet south of center 195 mph

Simplified schematic indication of location of tornado center and location of maximum Doppler Winds (195 mph), and very schematic approximate indication of 2750 diameter of maximum winds.

Elk City Tornado zoomed out view from DOW deployed on Highway 6 south of Elk City. Substantial precipitation surrounding tornado made it invisible to the eye. Much heavier precipitation here, but attenuated

Elk City, Oklahoma 16 May 2017. As measured by DOW deployed on Highway 6. Debris Ring, about 2000 feet diameter, in Elk City tornado about 2 minutes before peak wind intensity. Peak winds at this time 145 mph.