During the early evening of Friday, May 31, 2013, a very large and powerful tornado[a] occurred over rural areas of Central Oklahoma. This rain-wrapped, multiple-vortex tornado was the widest tornado ever recorded and was part of a larger weather system that produced dozens of tornadoes over the preceding days. The tornado initially touched down at 6:03 p.m. Central Daylight Time (2303 UTC) about 8.3 miles (13.4 km) west-southwest of El Reno, rapidly growing in size and becoming more violent as it tracked through central portions of Canadian County. Remaining over mostly open terrain, the tornado did not impact many structures; however, measurements from mobile weather radars revealed extreme winds up to 302 mph (486 km/h) within the vortex; these are the highest observed wind speeds on Earth, ahead of the 1999 Bridge Creek–Moore tornado with slightly higher wind speeds. As it crossed U.S. Highway 81, it had grown to a record-breaking width of 2.6 miles (4.2 km). Turning northeastward, the tornado soon weakened. Upon crossing Interstate 40, the tornado dissipated around 6:43 p.m. CDT (2343 UTC), after tracking for 16.2 miles (26.1 km), it avoided affecting the more densely populated areas near and within the Oklahoma City metropolitan area.
The tornado killed four storm chasers, the first known deaths in the history of storm chasing. Although the tornado remained over mostly open terrain, dozens of storm chasers unaware of its immense size and erratic movement were caught off-guard. Near Highway 81, TWISTEX scientist and engineer Tim Samaras, along with his son Paul and research partner Carl Young, died in the tornado. Paul Samaras and Young were ejected from their Chevrolet Cobalt by the storm’s sub-vortex, while Tim was still buckled in the passenger’s seat. Local resident Richard Henderson, who decided to follow the storm, lost his life in that same area. He snapped a picture of the tornado from his cellular phone before it struck him. Other chasers, including Mike Bettes of The Weather Channel and Reed Timmer, were either injured or had their vehicles damaged. A Doppler on Wheels-based analysis of how the tornado impacted these teams revealed that they were hit by an intense internal sub-vortex. Overall, the tornado was responsible for eight fatalities and 151 injuries. Due to the ferocity and sheer size, as well as its irregular movement and the deaths linked with this tornado, it has become one of the most studied and infamous tornadoes ever. The National Weather Service referred to the tornado as “the most dangerous tornado in storm observing history.”
Alongside rush hour traffic, thousands of residents in Oklahoma City attempted to outrun the storm by taking to the roads in an attempt to drive out of the tornado’s projected path. By attempting to escape the storm by vehicle, in direct contrast to the recommended plan of action, residents put themselves at great risk from the storm; had the tornado maintained itself and passed over the congested freeways, more than 500 lives could have been lost.