Portions of Lubbock, Texas, were struck by a powerful multiple-vortex tornado after nightfall on May 11, 1970, resulting in 26 fatalities and at least $135 million in damage. It was in its time the costliest tornado in U.S. history, damaging nearly 9,000 homes and inflicting widespread damage to businesses, high-rise buildings, and public infrastructure. The tornado's damage was surveyed by meteorologist Ted Fujita in what researcher Thomas P. Grazulis described as "the most detailed mapping ever done, up to that time, of the path of a single tornado." Originally, the most severe damage was assigned an F6 rating on the Fujita scale, making it one of only two tornadoes to receive the rating. Later, it was downgraded to an F5 rating after Fujita declared F6 damage was "inconceivable". The extremity of the damage and the force required to displace heavy objects as much as was observed indicated that winds produced by vortices within the tornado may have reached as high as .
Although skies were clear, dry, and sunny in Lubbock during the afternoon of May 11, the westward push of a dry line brought moist air into West Texas, providing suitable conditions for thunderstorm development. After 6:30 p.m., thunderstorms were in progress over the Lubbock area. At least two tornadoes developed prior to the main F5 tornado, including one that tracked across parts of eastern Lubbock near U.S. 87. The primary F5 tornado touched down in southwestern Lubbock at 9:35 p.m. and over the next half-hour carved a path of devastation encompassing roughly a quarter of the city, with the twister lifting near the Lubbock Municipal Airport shortly after 10 p.m. The tornado varied in size, spanning across when it first touched down before narrowing to around by the time it lifted. Severe damage was wrought to high-rises and other buildings in downtown Lubbock, including the 20-story Great Plains Life Building. The tornado briefly moved west and weakened, causing light damage to the campus of Texas Tech University before reintensifying and resuming a northward path. The tornado's most destructive impacts were observed in the Guadalupe barrio, north of 4th Street, along Texas State Highway Loop 289, and near the Lubbock County Club. In those locales, some homes were completely leveled and many others were irreparably damaged. Around 119 aircraft were damaged at the Lubbock airport where the Lubbock office of the United States Weather Bureau was located. As of 2023, this remains the westernmost F5/EF5 tornado recorded in the United States.
Synopsis
Developing storms (before 8 p.m.)
The Severe Local Storms Unit (SELS) within the National Severe Storms Forecast Center (NSSFC) of the United States Weather Bureautasked with issuing daily outlooks projecting possible severe weather over the U.S.did not initially highlight the possibility of severe weather over West Texas when the agency issued its daily outlook at 4 a.m. early on May 11, 1970. Six hours later, the SELS amended the outlook to indicate that "isolated thunderstorms with large hail" were "expected in High Plains of West Texas east of Pecos late afternoon and early evening." The afternoon was warm and dry in Lubbock with the temperature rising above and the dew point remaining at around . As the air mass over the region became increasingly unstable, the forecast agency later advised of the possibility that some of the isolated thunderstorms could become severe. However, the atmospheric conditions aloft were generally unsupportive of a tornado outbreak.