EF1 tornado, Aurelia to Larrabee, Iowa, December 15, 2021

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 mphthis tornado

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

3. EF2111 to 135 mph

   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

EF1

Date

December 15, 2021

Touchdown

4:59 PM CST (22:59 UTC)

Lifted

5:07 PM CST (23:07 UTC)

On the ground

8 minutes

Path length

11.2 miles (18.0 km)

Path width

250 yards (229 m)

Deaths

0

Injuries

0

Property damage

$1.0 million

County

Cherokee County

Touchdown point

42.635, -95.489

Lift-off point

42.776, -95.388

Record number

2112151659-01

53 damage points were recorded along this path by NWS FSD, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF2. The highest wind the damage implies is 115 mph.

• Possible centerline through golf course.
• Failure of doors likely led to further damage to walls and roofing on south facing storage garage.
• Dryer unit blown off top of elevator toward the SE. Dented bins, sections of damaged roofing at grain elevator.
• Pictures via county EM. EM reports that the power poles were newer and thicker as they were installed for transmitting energy from wind turbines

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

An unprecedented storm system lifted across the central Plains from December 15 into the early hours of December 16. Kinematic fields were at the top of the climatological distributions, leading to extreme wind shear in the lowest levels. Ahead of the system, record high temperatures with surface dew point values into the 50s and lower 60s surged toward northwest Iowa and resulted in instability not typically found in December.||A serial derecho developed across Nebraska and Kansas during the early afternoon and raced to the northeast toward Iowa and Minnesota, with widespread damaging wind and a few tornadoes. The first Storm Prediction Center moderate risk, as well as severe thunderstorm and tornado warnings during December, were issued for the Sioux Falls warning area. There was even remaining snow cover in parts of northwest Iowa north of Highway 18 and into southwest Minnesota as the severe storms evolved during the afternoon and evening hours.||As the cold front swung through the area behind the convective line, 60 to 75 mph winds aloft were mixed to the surface and resulted in a few synoptic wind gusts up to hurricane force. Some light wintry precipitation also fell during the transition toward the much colder air, which led to flash freezing as temperatures fell as much as 40 degrees during the overnight hours.

The tornado spun up 7 miles south-southwest of Aurelia just west of the intersection of T Avenue and 610th Street. The tornado moved either northeast or north-northeast along its track and exited Cherokee County at 1707CST near the intersection of 510th Street and 10th Avenue. The tornado continued northeast and lifted one mile south of the Buena Vista County Conservation Park at 1712CST. ||Shortly after touchdown, the tornado partially collapsed the roof on a hog confinement which killed 13 hogs. Debris from this building was strewn for one to two miles to the northeast. On a northeastward track, another animal confinement farm was struck by the tornado after a couple minutes which resulted in loss of several roof panels on multiple buildings. At this point the tornado shifted path toward more of a north-northeast direction and moved into Aurelia. A drying unit was removed from the top of a grain elevator on the south edge of town. Most of the damage throughout the eastern half of Aurelia was snapped trees, which caused collateral damage to numerous roofs and windows along the path. The tornado moved through the golf course snapping and uprooting numerous trees. The tornado continued with a shift to a more northeast track, and destroyed a barn and three outbuildings along 535th Street northeast of Aurelia. Additional damage occurred to a machine shed and large trees along the Cherokee and Buena Vista County line. The tornado was rated EF1 in both Cherokee and Buena Vista Counties. The average path width was 150 yards in Cherokee County and the maximum estimated wind speed was 110 mph. Property damage costs are a rough estimate.

This is the second segment of a tornado which developed 2 miles north-northwest of Galva at 1658CST, and entered Cherokee County 4 miles north of Galva just east of Marshal Avenue at 1700CST. The tornado tracked over open farmland in extreme southeast Cherokee County with no damage indicators, before it entered Buena Vista County at 1701CST, where the tornado lifted one mile southwest of Alta at 1706CST. The tornado was rated EF0 in Ida County, EFU in Cherokee County, and EF1 in Buena Vista County. The average path width in Cherokee County was estimated at 50 yards.

This tornado formed on the southeast fringes of Larrabee, just south of 455th Street. As the tornado crossed 455th Street, it quickly destroyed four silos, a shed and a chicken barn. The tornado traveled northeast over open fields before a few trees were snapped and the east wall of a barn was pulled away along R Avenue just south of 430th Street. The tornado exited Cherokee County around 4 miles south of Sutherland, one-half mile east of the intersection of Tyler Avenue and 420th Street. The tornado continued in O'Brien County for almost 4 miles before dissipating two miles southeast of Sutherland at 1711CST. The tornado was rated EF1 while in both Cherokee County and O'Brien County. The average path width in Cherokee County was 50 yards and the maximum estimated wind speed was 105 mph. Property damage costs are a rough estimate.

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

17 minutes of warning. NWS FSD issued a tornado warning for this county at 22:42 UTC, 17 minutes before the tornado touched down, in force until 23:15 UTC.

The county was under a tornado watch, issued at 19:23 UTC and running to 23:39 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 0.10 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 19:28 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 Sioux Falls radar (KFSD), 143 km away, was scanning. The volume nearest the touchdown began at 23:01 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 2021 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

124 more were confirmed in the United States that day.

All 125 of them

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.