High-Resolution TDWR Evolution of the Newcastle-Moore, Oklahoma Tornado of 20 May 2013

On the Monday afternoon of 20 May 2013, a tornado touched down west of Newcastle, Oklahoma at 19:56 UTC as an EF0, rapidly intensifying and attaining EF4 intensity within 10 minutes and 4 miles (6 km) of touchdown. The massive EF5 tornado stayed on the ground for 39 minutes over a 17-mile (27-km) path, tearing through a heavily populated section of Moore, killing 24 people and injuring 387. After moving to the east side of Moore, the tornado abruptly shrank in size, reducing to EF2 to EF3-strength before becoming a thin rope tornado and eventually dissipating about 4.8 miles (8 km) east of Moore around 20:35 UTC. The tornado followed a roughly similar track to the deadlier Bridge Creek-Moore tornado of 3 May 1999.

Primary interest is a tornado signature shown in high-resolution Doppler velocity data collected by the Oklahoma City (OKC) Terminal Doppler Weather Radar (TDWR) when the closest tornado was 3 miles (5 km) north-northwest of the TDWR. This signature is a rare vortex signature of extreme Doppler velocity values (of opposite sign) separated by at least several beamwidths in the azimuth direction, which arises when the tornado is within a few kilometers of the radar and the tornado is larger than the radar beam. The radar data were continuous for a substantial portion of the tornado's life and provided detailed information on the high-resolution velocity and reflectivity fields in and around the tornado. The data permit good estimates of tornado rotational velocity and diameter, and also allow comparison with tornado damage survey estimates of damage.0.8 on 8-13-2013-->