EF2 tornado, Rider to Zearing, Iowa, May 21, 2024

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mphthis tornado

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF2

Date

May 21, 2024

Touchdown

4:30 PM CDT (21:30 UTC)

Lifted

5:05 PM CDT (22:05 UTC)

On the ground

35 minutes

Path length

40.8 miles (65.7 km)

Path width

1,000 yards (914 m)

Deaths

0

Injuries

4

Property damage

$8.4 million

Counties

Polk and Story counties

Touchdown point

41.676, -93.762

Lift-off point

42.135, -93.262

Record number

2405211530-01

PLEASE NOTE, for hail, wind, heavy rain and flooding, please see separate Storm Data entry for May 20-22. ||Numerous tornadoes occurred on this day with numerous injuries and four fatalities at Greenfield in Adair County.||Multiple rounds of thunderstorms brought torrential rainfall, damaging winds, hail and destructive tornadoes to the state. These thunderstorms were the result of a low pressure system which lifted north into the area on the night of May 20th, 2024, producing slow moving storms that dropped 2 to 4 inches of rainfall. This resulted in flash flooding over portions of northern and central Iowa through the morning of May 21st, 2024.||Following the heavy rainfall through the morning, skies cleared out ahead of an approaching cold front. By the afternoon hours of May 21st, 2024, this cold front produced a line of strong thunderstorms which produced multiple strong tornadoes throughout the state, including one which led to significant damage in the town of Greenfield, IA, among other locations. This line of storms also produced damaging winds, leading to widespread tree damage and power outages throughout the forecast area.

This was a long track tornado which started just to the southwest of the Johnston High School with fascia and soffit damage to houses along Catalina Drive. The tornado blew windows out of the high school and continued to produce tree and minor roof damage through the Ashton Point neighborhood. The tornado crossed Camp Dodge and blew down a tree along NW Beaver Drive before crossing Saylorville Reservoir. The tornadoes path took it between Polk City and Ankeny with EF0 damage to trees and houses along Highway 415 and NW 44th Street. The damage began to intensify as the tornado moved northeast with EF1 damage becoming more prevelent in neighborhoods south of Alleman. The first EF2 damage was found on 142nd Avenue just west of Interstate 35 with additional EF2 damage to several houses near the intersection of NE 150th Avenue and NE 29th Street on the east side of the Interstate. The path continued to widen with additional damage near the border with Story County. This tornado moved into Story County near the intersection of NE 42nd Street and NE 166th Avenue. This tornado produced two injuries in Polk County.

This tornado moved into Story County from Polk County. The tornado was quite wide at this point nearing 1000 yards wide at times. Along Highway 210 southeast of Cambridge, 8 large wooden and relatively new higher voltage power poles were snapped. Trees were obliterated along 315th Street east of Cambridge. Additional EF2 damage occurred 620th Avenue where numerous outbuildings were destroyed. A house was completely removed from its foundation at the intersection of 270th Street and Woods Rd and was tossed across 270th Street. However, the house was undergoing a remodel at the time and had no anchorage to the pour concrete foundation, hence the EF2 rating at this location. Damage to a house along 250th Street southeast of Nevada was extensive with the house shifted off the foundation and much of the interior savaged by flying debris and mud. All the outbuildings at this location were destroyed with the debris strewn far downwind. Another brick house at the intersection of Highway 30 and 650th avenue had extensive damage with only the front of the house still intact. These last two houses had high end EF2 damage and it appears this is where the tornado was strongest. EF2 damage was still found downstream for several more miles but was not as extensive as what had been seen just southeast and east of Nevada. The last extensive damage with the tornado occurred along 160th Street between 710th and 720th Avenue where a house lost half of its roof and then hit a hog house about a half a mile later. The tornado then weakened and dissipated shortly before reaching 150th Street. Two additional injuries occurred in Story County with this tornado.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

11 minutes of warning. NWS DMX issued a tornado warning for this county at 21:19 UTC, 11 minutes before the tornado touched down, in force until 22:00 UTC.

The county was under a tornado watch, issued at 18:25 UTC and running to 22:53 UTC.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Moderate Risk, with a 0.15 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 19:57 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

The Des Moines radar (KDMX), 26 km away, was scanning. The volume nearest the touchdown began at 21:32 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2024 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

42 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.