2013 El Reno tornado

On May 31, 2013, a prominent mid-to-upper level trough and closed mid-level low pressure area moved east-northeastward, with a lead upper low pivoting over the Dakotas and Upper Midwest region. A moderately strong polar jet moved east-northeastward over the southern Rocky Mountains to the southern Great Plains. With a broad influence of moderately strong cyclonic flow aloft, the air mass was expected to become unstable across much of the southern Great Plains, through the Upper Midwest and Mississippi Valley, by the afternoon. Dewpoint values ranged from the upper 60s °F (20 °C) to the lower 70s °F (20–22 °C), with temperatures in the low to mid-80s °F (27–30 °C), and CAPE (a meteorological concept used to predict the force and power of potential storms and tornadoes) predicting referring to values ranging from 3500 to 5000 J/kg. Deep layer wind shear speeds of would enhance storm organization and intensity. These ingredients were present ahead of a cold front extending from the low from the eastern Dakotas southwestward to western Oklahoma, and ahead of a dry line extending from western Oklahoma southward into western north and west-central Texas. Storm development and track radar (reflectivity; [//upload.wikimedia.org/wikipedia/commons/3/3a/May_31%2C_2013_Oklahoma_Phased_Array_Radar_Reflectivity.gif click to animate]) of the series of supercell thunderstorms that impacted the Oklahoma City metropolitan area on May 31. A quasi-linear complex of thunderstorms began developing near the Highway 81 corridor west of Oklahoma City between 4:00 and 4:45 p.m. CDT, and rapidly reached severe intensity. At 5:33 p.m. CDT (22:33 UTC), the National Weather Service Weather Forecast Office in Norman, Oklahoma issued a tornado warning for Canadian County, prompted by increasingly strong tornadic circulation exhibited in the southernmost supercell of this complex. At 6:03 p.m. CDT (23:03 UTC), a large wall cloud formed and produced a tornado, initially in the form of several smaller sub-vortices, west-southwest of El Reno. At 6:28 p.m. CDT (23:28 UTC), the storm began moving into more densely populated areas of Canadian County while maintaining its intensity. This prompted the National Weather Service office in Norman to issue a tornado emergency for Yukon, Richland, Wiley Post Airport, Bethany, The Village, and eastern El Reno, as the tornado was projected to track toward western portions of the Oklahoma City metropolitan area. Within minutes, the tornado turned northeast and soon passed directly over Interstate 40 at around 6:42 p.m. CDT (23:42 UTC), killing two people. Shortly thereafter, the tornado lifted off the ground as it neared Banner Road. Overall, the tornado was on the ground for 40 minutes along a path. Intensity The intensity of the tornado has been a subject of internal debate within the National Oceanic and Atmospheric Administration. The agency uses the Enhanced Fujita Scale to rate and assess tornado intensity based on the damage left behind. This excludes the use of supplementary measurements, such as those from mobile radar, in concluding a tornado's intensity. Revised RaXPol analysis found winds of well above ground level and ≥ below , with some subvortices moving at . The strongest winds occurred in small subvortices along the south side of the main vortex. The two most intense vortices occurred north and east of the intersection of 10th Street and Radio Road, about southeast of El Reno. The main funnel is believed to have had radar-estimated EF4 winds, with wind speeds around . Radar-estimated EF5 winds were only found aloft and in the smaller vortices that revolved around this funnel at . William Hooke, a senior policy fellow at the American Meteorological Society stated that, "[Oklahoma City] dodged a bullet...You lay that path over Oklahoma City, and you have devastation of biblical proportions." On August 30, 2013, the National Weather Service office in Norman once again revised the intensity of the El Reno tornado. Keli Pirtle, a Public Affairs worker at the National Oceanic and Atmospheric Administration, stated that, "despite the radar-measured wind speeds, the survey team did not find damage that would support a rating higher than EF3. While the wind measurements from the mobile radars are considered reliable, NWS policy for determining EF-ratings is based on surveys of ground damage." The lack of EF5 damage was likely a result of the rural nature of the area, as the sub-vortices that contained the EF5 wind speeds did not impact any structures. == Storm chaser incidents ==

near the intersection of Reuter and South Radio Roads, almost southeast of El Reno. The tornado's unusual behavior consisted of several simultaneous occurrences: abrupt changes in direction, rapid enlargement to a width of in diameter in about 30 seconds, swift increase in forward motion from about within a few minutes, multiple vortices within and around, and an expansive translucent outer circulation without a full condensation funnel while being surrounded and obscured by precipitation made it a worst-case scenario for storm chasers. Several professional and amateur chasers were caught off guard and impacted by the tornado. Many were located in a region northeast of the tornado, known as the "bear's cage". Chasers can generally get a clear view of the tornado from that area; however, it places them at great risk and with little time to react should the storm take a left turn. Normally, Tim drove a reinforced three-quarter ton truck optimized for hail protection and stability in high winds; however, Carl was driving an unmodified Chevrolet Cobalt, a subcompact vehicle with three 45-lb barometric probes in the trunk likened by one TWISTEX chaser to a "pizza delivery car", making it much less suited to high winds and rain-slicked backcountry dirt roads. It was also underpowered, which hampered their escape in the strong inflow winds. Tim's body was found still buckled in the passenger's seat. They were the first known tornado-related deaths of either recreational storm chasers or scientific researchers. Mike Bettes, a meteorologist for The Weather Channel, was also caught in the storm. His sport utility vehicle was severely damaged, having been thrown about ; the driver was left with a broken neck, fractured vertebrae, and several broken ribs while Bettes and the other passenger sustained minor injuries. Meteorologist Emily Sutton and storm chaser Kevin Josefy of Oklahoma City NBC affiliate KFOR-TV (channel 4) were also caught in the path of the storm; their vehicle was damaged by debris hurled by the tornado. University of Oklahoma student Billy Prater, along with his father and a friend, sought refuge under an overpass (an action strongly discouraged in these situations) when the tornado changed direction. Near Union City, debris from a barn destroyed by the tornado struck the vehicle of Brandon Sullivan and Brett Wright, breaking their windshield; they escaped without injury. The hood of Reed Timmer's Dominator 2, a vehicle designed for intercepting tornadoes, was torn off by lines that were down from the tornado. Storm chaser Dan Robinson received injuries after being enveloped within the outskirts of the tornadic circulation. He escaped a few hundred meters ahead of the TWISTEX crew on Reuter Road and is believed to be the last person to see the car occupied by Samaras, his son Paul and Young. A Doppler on Wheels-based analysis of how the tornado impacted these teams revealed that they were hit by an intense internal sub-vortex. This analysis showed that both the Weather Channel and TWISTEX vehicles entered the tornado through the less intense north/northwestern side, then were impacted by the internal sub-vortex, which contained radar-indicated winds approaching and was moving in a complex quasi-trochoidal pattern, sometimes nearly stationary, sometimes with forward speeds over . Entering the larger tornadic circulation without the ability to maintain situational awareness of the internal sub-vortex was likely a key contributing factor to the deaths and injuries. The Discovery Channel scheduled a special tribute episode of Storm Chasers titled Mile Wide Tornado: Oklahoma Disaster on June 5, both honoring the three chasers and covering the events of the EF5-rated tornado that struck Moore and portions of southern Oklahoma City eleven days earlier on May 20. The November 2013 issue of National Geographic, for its featured cover story, paid tribute to Tim Samaras, a National Geographic Explorer funded in part by the Society, and featured a detailed scientific analysis of the tornado itself. A team of scientists and veteran chasers embarked on a crowd-sourcing survey project to gather storm chaser information, including video and photographic recordings and GPS logs, to piece together precisely what happened. It was the largest such visual data set ever collected on a tornado. The chaser information is compiled with radar and lightning data and the project is intended to eventually expand to a standardized open access database covering future events. In association with the project, software was unveiled in 2015 allowing for the synchronization of maps, radar data, and storm chasers' footage of the storm. The tool was named "Tornado Environment Display" (TED) after Dr. Ted Fujita. Anton Seimon, one of the tool's architects, said that while the tool had only been used in relation to the El Reno tornado, it could potentially be applied to future tornadoes with sufficient footage as well. == Casualties and impact ==

Since the tornado remained over mostly open terrain, damage was relatively light—although still significant in isolated locations—in comparison to its extreme intensity. Surveys from the National Weather Service revealed that structures in its path sustained EF3-level damage at most. The Oklahoma City West Livestock Market was described as a "war zone", sustaining extensive damage. Several large steel-frame warehouse type buildings were destroyed at that location. Multiple large brick buildings at the nearby Canadian Valley Technology Center were heavily damaged or destroyed, and a large metal wind turbine prop blade was thrown into the side of a daycare building on the property. Damage totals at that location alone were estimated at up to $40 million. One farmstead, consisting of a large barn, a cattle barn, three machine sheds, granaries and the owner's home, was also completely destroyed. Several other rural homes were destroyed, and large amounts of gravel was blown off of gravel roads in the area, with only the dirt underneath left at some locations. On June 1, the American Red Cross set up a shelter at the Redlands Community College in El Reno for victims of the storm. The following day, Oklahoma Governor Mary Fallin toured damaged areas of El Reno. Due to the tornadoes that occurred previously on May 20, a state of emergency was already in place for the affected areas, allowing residents to quickly obtain emergency assistance. Residents left homeless were provided with temporary housing constructed from shipping containers. Each container was fitted with a kitchen, bedroom, living room, and bathroom. Overall, eight people lost their lives as a result of the tornado, all of whom were killed in vehicles. Local hospitals in Oklahoma City, including OU Medical Center and INTEGRIS Southwest Medical Center, and Mercy Hospital in El Reno, reported receiving at least 115 injured, including five critical patients. Overall, 151 injuries were attributed to the tornado. Residents reported the highways to be a scene of chaos, "people were going southbound in the northbound lanes. Everybody was running for their lives." Dr. Jeff Masters of Weather Underground stated that had the tornado tracked directly over one of the congested highways, the death toll could have easily exceeded 500. == See also ==