1991 Andover tornado

1991 Andover tornado

The tornado, as seen at F4 intensity at the McConnell Air Force Base
Meteorological history
Formed	April 26, 1991, 5:49 p.m. CDT (UTC−05:00)
Dissipated	April 26, 1991, 7:14 p.m. CDT (UTC−05:00)
Duration	1 hour and 25 minutes
F5 tornado
on the Fujita scale
Highest winds	>261 mph (420 km/h)
Overall effects
Fatalities	17 (deadliest in 1991)
Injuries	225
Damage	~$300 million (1991 USD) (second-costliest of the 1990s)
Part of the 1991 Andover tornado outbreak and Tornadoes of 1991

In the afternoon hours of April 26, 1991, a large and devastating tornado moved 46 miles (74 km) through areas southeast of Wichita, located in the state of Kansas. The tornado killed seventeen, injured over two hundred others, and left an estimated $300 million (1991 USD) of damage in its wake. The tornado was one of the most powerful to ever strike Kansas; it received the highest rating on the Fujita scale.

The tornado first touched down near Clearwater, moving northeast while retaining EF0 and EF1 intensity. The tornado rapidly intensified as it approached Haysville, reaching F3 intensity at it directly impacted the town. After leaving Haysville in ruins, the tornado would strike several residential subdivions in eastern Wichita, where four people would be killed. The tornado would then track across the McConnell Air Force Base, becoming violent shortly before hitting the tarmac. At this location, the tornado narrowly avoided striking ten Rockwell B-1 Lancers, two of which were equipped with nuclear warheads. The tornado would then strengthen, reaching F5 intensity for the first time as it entered Andover. A mobile home park located in the town was obliterated, and thirteen people were killed; 165 more were injured as the park was torn apart in winds that were greater than 260 miles per hour (420 km/h). The tornado continued to heavily damage Andover before beginning to weaken after leaving the town. The tornado would strike an oil field, lofting a large oil tank over 0.8 miles (1.3 km) away. A short time later, the tornado would dissipate, tracking a total of 46 miles (74 km) over a period spanning almost an hour and a half.

On April 25, 1991, the National Weather Service issued a warning of an impending weather system, noting that computer models were "indicating this to be a very significant severe weather producer with tornadoes occurring across the Central/Southern Plains." On the morning of April 26, the organization delineated a High risk of severe weather across the Great Plains.^[1] A southeast-tilted trough existed across the Southwestern United States that morning, and a distinct jet streak, or a region of enhanced winds at the base of the trough, on the order of 75–85 kn (85–100 mph; 140–155 km/h) was progressing northeast toward the Plains.^[2][3] Through the morning hours, an 850 mb or approximately 5,000 ft (1,525 m) low-level jet of up to 60 kn (70 mph; 110 km/h) overspread regions from south-central Kansas northward into eastern Nebraska.^[4] A surface low-pressure area existed over southwestern Nebraska, supporting a dry line southward into Texas and a warm front southeastward across eastern sections of Kansas and Oklahoma.^[1]

In the unstable atmosphere between those two boundaries, surface dewpoints rose above 60 °F (15 °C). Abundant sunshine contributed to destabilization as lifted indices topped -12 from central Oklahoma into central Kansas and convective available potential energy reached 4,000 J/kg.^[1] A minimal capping inversion existed across Oklahoma even during the morning hours,^[2] and tornado-producing storms first developed across western Oklahoma around sunrise. These storms weakened as they moved northeast into Kansas.^[5] Back to the west, the dryline progressed rapidly eastward but began to slow precipitously during the afternoon hours. Attempts at thunderstorm development along this feature initially failed.^[1] At 17:10 UTC (12:20 p.m. CDT), the National Weather Service issued a particularly dangerous situation tornado watch, warning of the potential for multiple strong to violent tornadoes. This would be one of 24 convective watches issued during the day.^[2] Despite early failure at convective initiation, supercell thunderstorms rapidly erupted along the dryline during the afternoon hours as the jet streak propagated into the Great Plains, resulting in a regional outbreak of tornadoes stretching from Texas to Iowa. Violent tornadoes were concentrated in southern Kansas and Oklahoma, although intense tornadoes were also observed in Iowa, Texas, and Nebraska.^[5]

At 5:49 p.m. CDT (22:49 UTC), the storm which would become the Wichita–Andover tornado began southeast of Clearwater. At 6:05 p.m. CDT (23:05 UTC), the National Weather Service issued a statement urging residents in Haysville, Derby, and Mulvane to seek shelter. This was succeeded by a tornado warning four minutes later. Around 6:16 p.m. CDT (23:16 UTC), the intensifying tornado began to affect southeastern sections of Wichita and directly struck Haysville.^[6] It produced strong F2 to F3 damage in Haysville while growing to a width of about 220 yards (200 m) and acquiring multi-vortex characteristics. The tornado crossed the Kansas Turnpike about 0.5 miles (0.80 km) south of the South Wichita Interchange. In eastern Wichita, some well-built houses in the Greenwich Heights Subdivision were completely leveled, indicative of strong F3 to F4 damage. Four people were killed at this location.^[7] At 6:24 p.m. CDT (23:24 UTC), the violent tornado struck the McConnell Air Force Base, where it narrowly missed a lineup of 10 B-1B bombers each worth $280 million and 2 of which were equipped with nuclear warheads.^[6] Nine major facilities on the base were destroyed, including the officer's club, base hospital, library, and elementary school. In addition, 102 housing units were demolished. No fatalities were recorded there, though 16 people were injured and total losses reached $62 million. As the tornado continued to move toward U.S. Route 54 in Kansas in the direction of Andover,^[6] it prompted forecasters to issue a heightened tornado warning alerting residents in Augusta and Andover that a damaging tornado was approaching. Despite this warning, the single tornado siren that was located in Andover failed.^[8]

At 6:31 p.m. CDT (23:31 UTC), with the sirens not functional, the police drove through the Golden Spur Mobile Home Park and through the town warning residents to seek shelter. 10 minutes later, the now large wedge-stovepipe hybrid tornado entered southern Andover and began to impact the mobile home park, which ultimately sustained a direct hit.^[6] Of the 244 manufactured homes, 205, or about 84 percent of them, were destroyed. Post-storm interviews by health officials found that 339 residents were home during the tornado, of which 146 evacuated, 149 sought refuge in the community shelter, and 38 remained in their homes. No casualties occurred among individuals who fled or utilized the shelter.^[9] However, 13 people were killed,^[7] another 17 were hospitalized, and 9 sustained minor injuries among the group who remained in their structures.^[9] Additional homes were swept from their foundations to the west of this park, where the Andover tornado earned its F5 rating.^[7] Throughout the city, over 1,500 residences were devastated.^[10] The tornado continued northeast, affecting the outskirts of Towanda. Twenty minutes later, the violent tornado dissipated west of El Dorado and north of the Kansas Turnpike, though the parent supercell later produced additional tornadoes.^[6] Along the tornado's path, 84 frame houses and 14 businesses were leveled. A total of 225 people were injured.^[11]

Andover and surrounding areas were heavily damaged by the tornado, which carved a 46 miles (74 km) path through Sedgwick and Butler counties over a duration of one hour and twenty-five minutes. In Andover, the tornado directly impacted a mobile trailer park that had 244 homes in it; after the tornado only 39 of these homes could be recovered.^[12][13] Due to heavy damage, the Federal Emergency Management Agency (FEMA) designated much of the mobile home park and other areas as a federal disaster area.^[14]

The tornado produced heavy damage along its track, including significant damage to residential areas and a swath of F5 damage in a mobile trailer park located in Andover. In a National Weather Service post-event document released in December of 1991, the curators noted that "the mobile home devastation was some of the worst that this surveyor has ever seen".^[15] Most of the mobile homes located in the park were destroyed, many of which were swept away or were obliterated with only their metal frames still intact.^[15]

Near El Dorado, the tornado lofted a full oil tank 0.8 miles (1.3 km); the oil tank was never recovered, and two more tanks were obliterated by the tornado as it moved through the area.^[16]

As the tornado moved past the McConnell Air Force Base, it narrowly avoided striking ten B1-B bombers, who of which were actively armed with nuclear warheads as the tornado passed by.^[17] Each of these bombers were worth an estimated $280 million (1991 USD),^[18] and it is unknown if these bombs would have been detonated had the tornado hit the aircraft.^[19]

Seventeen people were killed by the tornado, the majority of which were located in the Golden Spur Mobile Home Park.^[20] Four deaths occurred in Sedgwick County, and the thirteen others were all living or residing in the park at the time the tornado hit. 200 people who lived at the park took refuge in an underground tornado shelter prior to the tornado hitting the area, and it is likely that many more people would have died had that shelter not existed.^[21][14] 225 people were further injured by the tornado, many located in mobile homes or other structures that were easily destroyed by the tornado.^[14]

• 1992 Chandler–Lake Wilson tornado, another F5 tornado that would strike Minnesota a year later
• 1999 Bridge Creek–Moore tornado, the costliest tornado of the 1990s

• Mosbacher, Robert A.; Knauss, John A.; Friday, Elbert W.; Damage Survey Team, NOAA (December 1991). "Wichita/Andover, Kansas, Tornado, April 26, 1991" (PDF). National Weather Service. Retrieved November 20, 2024.
• Moore, Cody (2016). "Infamous Andover tornado outbreak - April 26, 1991". University of Louisville. Retrieved November 20, 2024.
• Jen, Narramore (April 26, 2019). "The Wichita-Andover, KS F5 tornado - April 26, 1991". Tornado Talk. Retrieved November 20, 2024.
• Fischer, Henry W.; Schaeffer, Susan; Trowbridge, Marna L. (January 1992). "The impact of media blame assignation on the EOC response to disaster: A case study of the response to the April 26, 1991, Andover (Kansas) Tornado". University of South Florida. Retrieved November 20, 2024.