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The 2013 El Reno tornado was the widest tornado in recorded history. It occurred over rural areas of Central Oklahoma during the early evening of May 31, 2013. 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. CDT (2303 UTC) about west-southwest of El Reno. The storm rapidly grew in size and became more violent. Remaining over mostly open terrain, the tornado did not impact many structures; however, measurements from mobile Doppler weather radars revealed extreme winds in excess of within the tornado. As it crossed Highway 81, it had grown to a record-breaking width of . Turning northeastward, the tornado soon weakened. Upon crossing Interstate 40, the tornado dissipated around 6:43 p.m. CDT (2343 UTC), after tracking for , avoiding affecting 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 were caught off-guard. Along Highway 81, TWISTEX scientist and engineer Tim Samaras, along with his son Paul and research partner Carl Young, died near the Regional Airport. Paul and Young were ejected from their Chevrolet Cobalt by the storm's sub-vortex while Tim was still buckled in the passenger's seat next to Young's driving 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. 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 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.〔 ==Meteorological synopsis== 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 had 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 values ranging from 3500 to 5000 J/kg. Deep layer wind shear speeds of 45–55 kt would enhance storm organization and intensity.〔 These factors, along with CAPE values in excess of 4000 J/kg and an embedded speed maxima rotating around the southern periphery of the low, made the threat of significant severe thunderstorms increasingly likely. 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.〔 The most intense severe weather activity was expected across the southern Great Plains, specifically central and eastern Oklahoma, during the afternoon hours. As such, the Storm Prediction Center issued a moderate risk of severe thunderstorms during the early morning hours of May 31 from southeastern Missouri to southwestern Oklahoma. The degree of wind shear, moisture and instability within the warm sector favored the development of discrete supercells. Very large hail and tornadoes were expected with the supercells, with the possibility of a few strong to violent tornadoes.〔 A Particularly Dangerous Situation Tornado Watch was issued at 3:30 p.m. CDT early that afternoon from southwestern through northeastern Oklahoma, surrounding the Interstate 44 corridor. Thunderstorm activity across Oklahoma during the mid-afternoon hours was largely limited to far northern parts of the state due in part to a capping inversion that did not erode farther south until later in the day, aided by a shortwave trough that pushed into the region from the Texas Panhandle and a stronger trough located over Colorado. A quasi-linear complex of severe thunderstorms began developing near the Highway 81 corridor west of Oklahoma City between 4:00 and 4:45 p.m. CDT. At 5:33 p.m. CDT (2233 UTC), the southernmost supercell in this complex prompted a tornado warning for Canadian County as it exhibited tornadic circulation. At 6:03 p.m. CDT (2303 UTC), a large tornadic wall cloud formed and, after dropping several sub-vortices, touched down west-southwest of El Reno.〔 It ultimately attained EF3 intensity during its existence, according to ground surveys.〔 As the tornado passed south of El Reno along Highway 81, it reached an unprecedented width of , becoming the widest known tornado ever recorded worldwide. At 6:28 p.m. CDT (2328 UTC), the storm began moving into more densely populated areas while maintaining its intensity. This prompted a tornado emergency to be issued for Yukon, Richland, Wiley Post Airport, Bethany, The Village, and eastern El Reno. Within minutes, the tornado turned northeast and soon passed directly over Interstate 40 at around 6:42 p.m. CDT (2342 UTC). 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.〔 A strong anticyclonic multivortex satellite tornado also formed southeast of the primary tornado from approximately 6:28 pm CDT (2328 UTC) to 6:43 (2343 UTC). Such companion tornadoes tend to be observed with especially large and intense tornadoes although this was the first documented multiple-vortex anticyclonic tornado of this kind. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2013 El Reno tornado」の詳細全文を読む スポンサード リンク
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