| Basin: | atl |
| Fujita-Scale: | EF4 |
| Year: | 2024 |
| Deaths: | 5 |
| Injuries: | 35 |
| Damages: | $31,800,000[1] [2] |
| Affected: | Page, Taylor, Adams, and Adair, Iowa counties. |
Throughout the afternoon hours of May 21, 2024, a large, powerful, and destructive multi-vortex tornado struck the cities and communities of Villisca, Nodaway, Brooks, Corning, and Greenfield in southwestern Iowa, killing five people and injuring 35 others. The tornado was the strongest of the tornado outbreak sequence of May 19–27, 2024. The tornado reached peak intensity in the city of Greenfield, leading the National Weather Service in Des Moines, Iowa to assign a rating of mid-range EF4 on the Enhanced Fujita scale, with maximum wind speeds estimated at 185mph.[3]
This tornado was the fourth violent tornado of the 2024 season and the second one during the prolifically active month of May.
On May 21, the SPC issued a Moderate risk for severe weather in the states of Iowa, Missouri, Minnesota, Wisconsin, and Illinois, including a 15% risk for significant tornadoes.[4] Upper-air soundings observed steep lapse rates in the middle troposphere over parts of Kansas and Missouri on the morning of May 21. The SPC predicted that these conditions would spread into the primary severe weather risk area, overlapping with a moist airmass with dew points approaching and leading to strong potential atmospheric instability.[5] That morning, an organized cluster of thunderstorms moved into Iowa after having produced severe wind gusts in central and eastern Nebraska. This line of storms continued across central and eastern Iowa just north of a warm front, presenting a continued threat for damaging wind gusts.[6] Additional storms began to develop along the border between Kansas and Nebraska ahead of an approaching trough. The SPC anticipated that the atmospheric environment over eastern Nebraska and western Iowa would become increasingly conducive for further organization of these storms into supercells.[7] A tornado watch was issued by the SPC for areas near and along the Nebraska–Iowa border region at 11:10 a.m. CDT in anticipation of these changes.[8] At 1:10 p.m. CDT, the SPC issued a tornado watch flagged as a particularly dangerous situation for much of Iowa and parts of surrounding states, including an 80% likelihood of a significant tornado occurring within the watch area.[9] Supercells were active over southwestern Iowa by the mid-afternoon, approaching an environment favorable for tornadogenesis leading into the Des Moines area.[10]
The supercell that produced the Greenfield EF4 tornado initiated in Nemaha County, Nebraska. It matured and continued northeast for 45.8miles, where the first tornado warning was issued for the supercell in Page County, Iowa. Five minutes later, a large, long-track tornado touched down 10.5miles southwest of Villisca. The tornado continued northeast for 34.64miles, before finally lifting northwest of Carl. The tornado was rated as a high-end EF3 with wind speeds estimated at 155mph, reaching a peak width of 1300yd along a 34.64miles path, remaining on the ground for 38 minutes. As this tornado was ongoing, a separate circulation spawned the violent Greenfield tornado.[11]
This tornado first touched down south-southeast of the town of Villisca in Page County and moved northeastward at mid-range EF1 intensity, destroying all but one wall of an outbuilding and damaging the roof of a home. It then clipped the far northwestern tip of Taylor County, before moving into southwestern Adams County, inflicting EF0 damage to trees. Continuing northeastward, the tornado reached EF1 intensity again as it approached and passed southeast of Nodaway, snapping wooden utility poles, heavily damaging or destroying outbuildings, causing minor damage to homes, and snapping trees.[12] Continuing northeastward, the tornado passed just west of Brooks, destroying and throwing a grain bin and damaging trees. Crossing US 34 west of Corning and continuing northeastward, the tornado heavily damaged or destroyed outbuildings, inflicted roof damage to homes, and snapped trees. The first area of severe damage occurred north of Corning as the tornado crossed Iowa 148. An outbuilding was obliterated and swept away and a home had it's garage destroyed and suffered moderate roof damage. This damage was rated low-end EF2. A woman driving on Iowa 148 died when she was ejected from her car after it was lofted by the tornado.[13] The tornado continued northeastward over rural, open terrain, with the only damage being EF0-EF1 damage to the roofs of an outbuilding and a home along the outer edge of the circulation. The next area of concentrated damage was at the intersection of 150th Street and Notchwood Avenue. The tornado was at high-end EF3 intensity here as a cinderblock home was completely leveled with the debris collapsing into the basement. Outbuildings on the property were destroyed, a loaded grain bin had its top ripped off, a tractor-trailer was lofted and turned 360°, and trees were snapped. To the northeast of here, the tornado continued over open terrain. EF2 damage was inflicted to a large metal outbuilding that lost its roof with EF1 roof damage to a home along with a destroyed outbuilding. It also toppled at least five wind turbines along this portion of the track, including one turbine that caught on fire; an EF2 rating was given to this damage. The tornado exhibited violent motion and multiple vortices along this segment of the path as well.
The tornado then crossed into Adair County and continued northeastward through Richland Township, where it initially uprooted trees at EF1 intensity. A home further to the northeast suffered roof and siding damage and had a snapped tree fall on it. A silo was toppled, and an outbuilding was damaged as well. The tornado then began to cause EF2 damage, toppling another wind turbine, knocking down a metal transmission tower, and destroying an outbuilding. The tornado then quickly became violent and reached low-end EF4 intensity for the first time, leveling an outbuilding and a home each along Fontanelle Road and 310th Street. The tornado then moved back over open terrain with damage limited to an outbuilding, which was rated EF1. Low-end EF4 damage was observed again as the tornado crossed 290th Street where another home was leveled. Crossing Jordan Avenue, the violent tornado leveled another home. A nearby home was also mostly destroyed at EF3 intensity and trees were snapped, including some that had partial debarking. As the tornado approached Greenfield from the southwest, it inflicted EF1 roof damage to a home, destroyed an outbuilding and tossed vehicles at EF2 intensity, destroyed two homes at EF3 intensity with the first one being leveled, and inflicted EF1 roof damage to another home. Right before entering Greenfield, the tornado destroyed two outbuildings and inflicted severe roof damage to a home at EF2 intensity.
The tornado then turned east-northeastward, entered the southwest part of Greenfield, and became violent again reaching its peak intensity of mid-range EF4 as it entered the town. Dozens of homes were leveled with some homes being partially to completely swept away, and mobile homes and outbuildings were obliterated. The most intense damage occurred along SE 2nd Street, where a well-built home was obliterated and swept away; the estimated wind speed at this location was 185 mph (298 km/h). Many other homes suffered extensive roof and exterior wall damage, and many large trees were snapped and stubbed, including some that landed on and contributed to houses being leveled. The tornado then briefly weakened but remained at an intense high-end EF3 strength on the southeast side of town, continuing to heavily damage homes, including some that were leveled or shifted off their foundations, obliterating mobile homes, and snap large trees. The tornado then became violent again, reaching low-end EF4 intensity on the eastern side of town near the intersection of Iowa 92 and Iowa 25. More homes were leveled, shifted off their foundations, or suffered severe roof and exterior wall damage. It also heavily damaged or destroyed more outbuildings and stubbed additional trees. All throughout the town, vehicles were destroyed and wooden power poles were snapped as well.[14] Four fatalities and 35 injuries were reported in the town.[15] [16] An EF2 tornado developed to the northeast of Greenfield as the violent tornado moved through the town. After exiting Greenfield, this tornado moved east-northeastward, weakened, and dissipated over open terrain as the other tornado became the dominant circulation within the supercell.
On the day of the tornado, the DOW team made a very preliminary analysis, suggesting a Doppler on Wheels measured winds of at least 90m/s.[17] The next day, a further preliminary analysis by the DOW team determined that a Doppler on Wheels measured winds of at least >250mph, "possibly as high as 290mph" at 44m (144feet) above the surface, as the tornado moved through the town. Pieter Groenemeijer, the director of the European Severe Storms Laboratory noted that "on the IF-scale, 250 mph measured below 60 m above ground level is IF4 on the IF-scale, 290 mph is IF5."[18]
On June 24, after further analysis, the report was revised to winds of NaNmph near the surface, based on the measurement of at NaNm (-2,147,483,648feet) above the surface.[19] [20] This preliminary data suggests that the Greenfield, Iowa EF4 tornado had the third highest measured wind speeds recorded in a tornado and the third tornado to ever been recorded to be over 300 mph.
The tornado was rated as a mid-range EF4 with wind speeds estimated at 185mph, reaching a peak width of 1600yd along an 43.07miles path, remaining on the ground for 48 minutes. Five fatalities occurred, along with 35 injuries. Later on, the same supercell produced a large, long-track, high-end EF2 tornado east of Cambridge, Iowa. Several homes were severely damaged. A few other weaker tornadoes would touch down as well, none causing significant damage.
In the following hours of the tornado, emergency personnel as well as storm chasers rushed into Greenfield to provide aid. Surrounding communities such as Red Oak quickly responded in Greenfield.[21] The local St. John's Catholic Church parking lot was set up as a center for volunteers. Iowa state governor Kim Reynolds toured the damage the following day, describing the views as "horrific."[22] Due to timely response, 50% of the town's power was restored by Thursday morning.
A resident of Greenfield went viral after a news clip circulated of his distraught over losing golf clubs. In response, he received new golf clubs from Callaway and TaylorMade, and he also received an invitation to play in the John Deere Classic mini Pro-Am.[23]