1970 F5 tornado in Texas
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Portions of Lubbock, Texas, were struck by a powerful multiple-vortex tornado after nightfall on May 11, 1970, resulting in 26 fatalities and an estimated $250 million in damage (equivalent to $ billion in 2023). 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 a preliminary F6 rating on the Fujita scale, making it one of only two tornadoes to receive the rating, alongside the 1974 Xenia tornado. Later, it was downgraded to an F5 rating. 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 exceeded .
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 2024, 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 Bureau – tasked 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.
The skies over Lubbock were initially clear on May 11, with the ambient moisture too low to support severe convective storms on its own. However, moist air from the Gulf of Mexico spread north-northwest into the area during the day, providing sufficient buoyancy for convective development. Cumulus clouds began to proliferate over the region by around 4 p.m. and towering cumulus clouds began to develop over West Texas, darkening the skies over Lubbock. The WSR-57 weather radar site in Amarillo, Texas, began detecting radar echoes south of Lubbock at 6:30 p.m. Lubbock radar later picked up on a thunderstorm with a diameter of approximately forming near Woodrow, Texas, south of the Lubbock Municipal Airport. Satellite imagery from the ATS-3 satellite showed that the storm emerged about behind the leading edge of the advancing mass of moist air originating from the Gulf. Although the westward retreat of this boundary – known as a dry line – would typically coincide with nightfall and a stabilizing of the atmosphere, it did not move far from Lubbock during the evening, maintaining a local area of converging winds and moist rising air supportive of thunderstorm growth. These conducive conditions were also bolstered by the approach of a shortwave trough in the mid-levels of the troposphere, serving as another contributor to rising air. By 7 p.m. the northern fringes of the storm were near the Lubbock city limits. A radiosonde launched from Amarillo concurrently showed that the tropopause had risen by to over the preceding 12 hours. The Amarillo weather radar also suggested that the thunderstorm's cloud tops were rising to at least .
Ironically, at the time the storm was developing, the Lubbock Civil Defense was holding a meeting to discuss disaster preparation plans, highlighted by showing the documentary film "Tornado!" (1966). The Lubbock Tornado itself became the subject of another documentary, "Twister", with a subtle emphasis on a bumper sticker: "Lucky Me! I Live in Lubbock!"
With the storm approaching and threatening to become severe, Alan Johnson of the Weather Bureau called Bill Payne, the director of Lubbock Civil Defense, to provide notice of the inclement weather. The emergency operations center (EOC) at the basement of the Lubbock city hall was activated at 7:45 p.m. Following discussion between forecasters at the local Weather Bureau office in Lubbock (Lubbock WBO, located at the Lubbock airport) and the radar operator in Amarillo, a severe thunderstorm warning was issued by the Lubbock WBO for Crosby, Floyd, Lubbock, and Hale counties at 7:50 p.m. with an expiration time set to 9:00 p.m. This warning was disseminated via the Emergency Action Notification Signal and through local radio and television stations such as KFYO. KFYO continuously ran without commercials after this time until 7:30 a.m. on May 14. Despite the increasingly conducive atmospheric conditions for the formation of severe thunderstorms, the NSSFC did not issue a severe thunderstorm watch or tornado watch for the region before storms developed. The Environmental Science Services Administration (ESSA) wrote in a service assessment of the weather event that the lack of such of a watch from the NSSFC demanded "some explanation," but also noted that their absence did not affect the operations of the Lubbock WBO.
Precursor tornadoes develop (8–9 p.m.).
Large hail the size of grapefruits were reported in the thunderstorm south of Lubbock at around 8 p.m., with baseball-sized hail reaching southeastern Lubbock by 8:13 p.m. Severe Weather Statements were transmitted by the Lubbock WBO over the Weather Wire Service to relay the hail reports as the storm neared Lubbock. Radar data indicated that the thunderstorm's cloud tops had increased to by 8:10 p.m. At around the same time, an off-duty policeman reported a funnel cloud southeast of the Lubbock airport and east of the city limits. This, along with the detection of a hook echo on radar, prompted the Lubbock Weather Bureau office to issue a tornado warning for Crosby, eastern Floyd, western Hale, and Lubbock counties at 8:15 p.m. with an expiration time of 9:00 p.m. At 8:30 p.m., a tornado – the first of two to strike the Lubbock area – touched down near the intersection of Broadway and Quint Avenue in eastern Lubbock. Described by tornado researcher Ted Fujita as a "small forerunner" to the main Lubbock tornado, this first twister produced a damage path roughly across and caused structural damage indicative of wind gusts reaching around . The most severe damage occurred near the interchange between U.S. 82 and Parkway Drive, which was under construction at the time. There, 13 concrete beams weighing each and doubly weighted with chains were blown down from a partially-built overpass by the tornado.
At 8:40 p.m., the NSSFC issued a severe thunderstorm watch for the entirety of the Southern Plains. Concurrently, two thunderstorms quickly developed southwest of the Lubbock airport and moved northeast at ; their formation was noted on a Severe Weather Statement issued by the Lubbock WBO at 8:42 p.m. At 8:59 p.m., the office issued a bulletin that extended the preexisting tornado warning to 10 p.m. The bulletin also advised people to prepare to seek shelter with radar imagery and reports continuing to indicate that a tornado was in progress roughly south-southeast of the Lubbock airport. At around 9:00 p.m., a separate tornado – listed as an F1 tornado in the National Centers for Environmental Information's "Storm Events" database – unroofed a barn approximately north of Crosbyton, shearing the sheet metal roof over a nearby pasture.
 ;templatestyles src="Template:Blockquote/styles.css" / ;TORNADO WARNING REMAINS IN EFFECT FOR LUBBOCK...WESTERN CROSBY...FLOYD...AND SOUTHERN HALE COUNTIES UNTIL 10 PM TONIGHT...SEVERE THUNDERSTORMS WITH LARGE HAIL...DAMAGING WINDS AND POSSIBLY A TORNADO IN THESE AREAS UNTIL 10 PM...RADAR STILL INDICATES GOOD HOOK FORMATION ABOUT 6 MILES SOUTH SOUTHEAST OF THE LUBBOCK AIRPORT...AND THIS LOCATION WOULD BE ON THE BUFFALO SPRINGS LAKE ROAD ABOUT 3 MILES EAST OF THE CITY OF LUBBOCK...IDALOU SHOULD BE ON THE ALERT IN PARTICULAR FOR THIS SEVERE STORM AND POSSIBLE TORNADO...
The main Lubbock tornado (after 9 p.m.).
Large hail continued to fall throughout Lubbock, with reports indicating hail the size of golf balls and baseballs. After around 9 p.m., the radar echoes associated with the storms in the Lubbock area began to congeal, resulting in a singular, larger echo. This coalescence had been previously observed in connection with tornadogenesis. By 9:14 p.m., the severe thunderstorm was in diameter based on radar data. At 9:35 p.m., the main Lubbock tornado, much larger and more destructive than the previous tornadoes, touched down near the intersection of 19th Street and University Avenue and began to track towards the north-northeast. The WSR-1 radar site in Lubbock simultaneously observed a hook echo in the thunderstorm coincident with the newly formed tornado. This prompted the Lubbock WBO to alert the Lubbock Civil Defense EOC, which, in combination with a spotter report of a funnel cloud in the area, resulted in the activation of tornado warning sirens. However, the tornado's winds had already severed the power lines that serviced many of the sirens, rendering them inoperable and causing their failure to activate. Although police cruisers also sounded their sirens to alert those nearby of the imminent tornado, many ultimately did not hear either signal and thus likely received no warning.
Communications were brought down as the tornado tore through Lubbock and triggered widespread power outages. At 9:43 p.m., Bud Andrews, the radio announcer on KFYO, directed listeners to take shelter shortly before the AM station stopped transmitting. The Lubbock Civil Defense headquarters lost commercial power and communications at 9:46 p.m. with the exception of a single telephone line. The Lubbock WBO was able to reach the EOC at 9:47 p.m. to relay that the hook echo observed on radar was in the vicinity of 4th Street and Avenue U. This was the last communication transmitted by the Lubbock WBO as all communications went offline at 9:49 p.m. The WSR-1 radar also went offline around the same time following the downing of its emergency generator. The personnel at the office abandoned their post and took shelter at 9:55 p.m. shortly before the tornado passed over the Lubbock WBO. With the Lubbock WBO no longer fully operational, dissemination of subsequent tornado warnings were carried out by the agency using the VHF-FM radio of the Lubbock Fire Department; this was ultimately the only line of communication between the Lubbock WBO and the surrounding area and allowed tornado warnings to be communicated to the Abernathy, New Deal, and Petersburg areas at 10:10 p.m. Wind gusts at the nearby airport reached at 10:03 p.m., likely coinciding with the tornado's passage over the airport and the Weather Bureau office. The tornado lifted near the airport shortly thereafter. All weather warnings were called off by the Lubbock WBO at 11:30 p.m. once thunderstorms had lessened to a more moderate intensity around Lorenzo, Texas.
Impact.
The primary Lubbock tornado – the second of two tornadoes that struck the city on May 11 – produced a damage path long and extending across of ground, beginning at 9:35 p.m. in southwestern Lubbock, tracking through downtown Lubbock, and lifting shortly after 10 p.m. near the Lubbock Municipal Airport This damage path covered nearly a quarter of the city. The tornado was wide when it formed and when it tracked