2024 Greenfield tornado

2024 Greenfield tornado

Top: A photo of the EF4 tornado taken east of Carl, Iowa. Middle: High-resolution radar data of the EF4 tornado caught by DOW6. Bottom: Multiple radar imagery as the tornado enters Greenfield, Iowa at peak intensity.
Meteorological history
Formed	May 21, 2024, 2:57 p.m. CDT (UTC−05:00)
Dissipated	May 21, 2024, 3:45 pm. CDT (UTC−05:00)
Duration	48 minutes
EF4 tornado
on the Enhanced Fujita scale
Highest winds	Official intensity: 185 mph (298 km/h) Unofficial intensity: 309–318 mph (497–512 km/h) (Doppler on Wheels (DOW) estimate)
Overall effects
Fatalities	5
Injuries	35
Damage	$31,800,000[1][2]
Areas affected	Page, Taylor, Adams, and Adair, Iowa counties.
Part of the Tornado outbreak sequence of May 19–27, 2024 and Tornadoes of 2024

On the afternoon of May 21, 2024, a violent, destructive and powerful multi-vortex tornado struck the communities of Villisca, Nodaway, Brooks, Corning, and Greenfield in southwestern Iowa, killing five people and injuring 35 others. The tornado was the strongest of a large widespread tornado outbreak that occurred from May 19-27, 2024 in the central United States. 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 185 mph (298 km/h). However, winds of 309–318 mph (497–512 km/h) were measured in a sub-vortex of the tornado by a DOW (Doppler on Wheels), placing it among the strongest tornadoes ever measured.^[3]

This tornado was the fourth violent tornado of the 2024 season and the second one to occur during the prolifically active month of May.

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The Storm Prediction Center forecast for May 21

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 70 °F (21 °C) 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 45.8-mile (73.7 km), where the first tornado warning was issued for the supercell in Page County, Iowa. Five minutes later, a large, long-track tornado touched down 10.5-mile (16.9 km) southwest of Villisca. The tornado continued northeast for 34.64-mile (55.75 km), before finally lifting northwest of Carl. The tornado was rated as a high-end EF3 with wind speeds estimated at 155 mph (249 km/h), reaching a peak width of 1,300 yards (1,200 m) along a 34.64-mile (55.75 km) path, remaining on the ground for 38 minutes.^[11] As this tornado was ongoing, a separate circulation spawned the violent Greenfield tornado.^[12]

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The National Weather Service's finalized damage survey and analysis on the tornado

Low-end EF2 tornado damage to a toppled wind turbine that caught fire east of Carl, Iowa.

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 (this segment was rated EFU because no damage occurred), 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 its garage destroyed and suffered moderate roof damage. This damage was rated low-end EF2.^[12] 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 an unanchored cinderblock home was slid off its foundation and completely leveled with the debris collapsing into the basement. All the 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, with the blades being thrown hundreds of feet; an EF2 rating was given to this damage.^[12] Mechanical engineer Ethan Moriarty calculated that winds of approximately 116 mph (187 km/h) were needed to topple the wind turbines, which was only 1 mph (1.6 km/h) less than the official rating given by the National Weather Service.^[14] The tornado exhibited violent motion and multiple vortices along this segment of the path and was at its widest point as well.^[15]

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.^[12] 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. Along Fontanelle Road, a well-anchored home was demolished and swept away with the debris left in a large pile next to the foundation. An outbuilding on the property was completely obliterated, although the farm equipment was mostly unmoved and not severely damaged, and trees were shredded. Northeast of there on 310th Street, a nailed down cinderblock foundation home and an outbuilding were obliterated and swept away; vehicles inside the garage of the home were damaged, but not tossed, while debris from the structures and vehicles within it were left straddling along the sides of the foundation. The tornado then moved back over open terrain, inflicting damage to an outbuilding, which was rated EF1, and downing more wind turbines. 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, and overturned a vehicle and threw into a tree line. A nearby home was also mostly destroyed at EF3 intensity, and more trees were snapped, including some that had partial debarking. The tornado then moved through another wind farm, collapsing additional wind turbines. 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 passed over Nodaway Park Ponds and destroyed two outbuildings and inflicted severe roof damage to a home at EF2 intensity.^[12]

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 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; however, other homes that were leveled nearby were not completely swept away although debris was scattered throughout the area. The estimated wind speed at this location was 185 mph (298 km/h) as a result. 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.^[12][16] Four fatalities and 35 injuries were reported in the town.^[17][18][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, damaged a few more homes, and dissipated over open terrain as the other tornado became the dominant circulation within the supercell.^[12]

On the day of the tornado, the DOW team made a very preliminary analysis, suggesting a Doppler on Wheels measured winds of at least 90 m/s (200 mph).^[19] The next day, a further preliminary analysis by the DOW team determined that a Doppler on Wheels measured winds of at least >250 mph (400 km/h), "possibly as high as 290 mph (470 km/h)" at 48 yards (44 m) 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."^[20]

On June 24, after further analysis, the report was revised to winds of 308–319 mph (496–513 km/h) in a brief 1 second gust, based on the measurement of 263–271 mph (423–436 km/h) at 36–38 yards (33–35 m) above the surface.^[21][22] This preliminary data suggests that the Greenfield, Iowa EF4 tornado had the third highest measured wind speeds recorded in a tornado and was the third tornado to ever been recorded to be over 300 mph.

Across the street from the Adair County Memorial Hospital, the tornado ripped new concrete parking lot stop blocks from the ground, which were installed sometime after August 2023. Mechanical engineer Ethan Moriarty calculated that winds of at least 247 miles per hour (398 km/h) was needed to rip the concrete stop blocks out of the ground if they were cracked prior to being pulled up, or 283 miles per hour (455 km/h) if they were uncracked prior to being ripped out of the ground. The tornado, once nearly a mile wide at one point, had reduced in size signifcantly before impacting Greenfield, with the conservation of angular momentum potentially being responsible for the tornado's intensity near the end of its life. In the conclusion of his analysis, Moriarty stated that he believed the tornado was "without question a tornado capable of EF5 damage", while stating that, had the tornado been rated on a scale other than the Enhanced Fujita scale, it may have received a higher rating.^[14]

The tornado was rated as a mid-range EF4 with wind speeds estimated at 185 mph (298 km/h), reaching a peak width of 1,300 yards (1,200 m) along an 42.38-mile (68.20 km) path, remaining on the ground for 48 minutes. Five fatalities occurred, along with 35 injuries.^[15] 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.^[12]

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.^[23] The local St. John's Catholic Church parking lot was set up as a center for volunteers.^[23] Iowa state governor Kim Reynolds toured the damage the following day, describing the views as "horrific."^[24] Due to timely response, 50% of the town's power was restored by Thursday morning.^[23]

A resident of Greenfield went viral after a news clip circulated of him being 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.^[25]

Wikimedia Commons has media related to 2024 Greenfield tornado.

• Weather of 2024
• List of tornadoes in the tornado outbreak sequence of May 19–27, 2024
• Tornado records
• List of F4 and EF4 tornadoes (2020–present)
• Mobile radar observation of tornadoes
• Research on tornadoes in 2024

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