Unrated tornado, Lennox to Harrisburg, South Dakota, August 28, 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 mph

   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. Unratedthis tornado

   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

Unrated

Date

August 28, 2021

Touchdown

4:30 PM CDT (21:30 UTC)

Lifted

4:32 PM CDT (21:32 UTC)

On the ground

2 minutes

Path length

1.6 miles (2.6 km)

Path width

20 yards (18 m)

Deaths

0

Injuries

0

County

Lincoln County

Touchdown point

43.362, -96.783

Lift-off point

43.373, -96.756

Record number

2108281530-01

31 damage points were recorded along this path by NWS FSD, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 95 mph.

• Shed destroyed. Sill plate attached to concrete slab completely rotten.
• East side wall blown out after west facing door failed. Soybeans laying in similar direction.
• Looking southeast. Large corn field flattened. Stalks to the east.
• Debris laid out to the northeast.

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

An unstable warm sector with MUCAPE up to 2000-2500 J/kg developed during the afternoon between an advancing cold front across southeast South Dakota and a gangly warm front extending into southwest Minnesota. An approaching weak impulse spurred rapid development of multiple rounds of storms near the warm front, initially discrete, with upscale growth into short bowing segments. Secondary development occurred during the evening along the cold front, which evolved into a slow-moving linear system with hail, wind, and heavy rainfall with shear vectors increasingly parallel to the boundary.

Based on Sentinel satellite imagery, the tornado spun up in Turner County around 2 miles west southwest of Lennox in a field southwest of the intersection of 464th Avenue and 279th Street. The tornado tracked east-northeast for around one-half mile and crossed into Lincoln County just south of the intersection of 279th Street and 464th Avenue. After another half mile, the tornado uprooted seven large cottonwood trees and damaged numerous others at the Lenkota Country Club. The tornado continued into the western portions of Lennox north of the city park, with a majority of damage to large trees between 4th and 5th Avenue as the path turned more eastward and eventually a bit southeastward. The most significant damage occurred as the tornado approached State Highway 17, with a trampoline deposited high in a gnarled tree along South Cherry Street, and the complete destruction of a shed just east of Highway 17. The tornado lifted about a quarter mile east of Highway 17, just east of Lennox. Areas south of the path experienced strong rear-flank winds. While in Turner County, the tornado was rated EFU, while in Lincoln County it was rated EF1. The average path width for the tornado was 100 yards. Property damage costs are a rough estimate.

Based on Sentinel satellite imagery and confirmed with ground survey, a brief tornado spun up around 2 miles east of Lennox, just west of the Mount Olivet Cemetery. The tornado tracked east-northeast for less than one mile across open fields and wetlands, and dissipated 3 miles east-northeast of Lennox near the intersection of 278th Street and 468th Avenue. The average path width was 20 yards.

This tornado formed 2 miles north-northwest of Worthing, around one-half mile east of Interstate 29 and north of 278th Street. The tornado tracked northeast and then east-northeast for around one and one-half miles across open farmland and lifted 3 miles north-northeast of Worthing just south of 277th Street. The average path width, identified by crop damage in Sentinel satellite imagery, was 20 yards.

A tornado spun up 4 miles northeast of Worthing, one-half mile north of 278th Street just east of 475th Avenue. The tornado tracked northeast for a little over a mile before it lifted 4 miles south of Harrisburg, just southwest of the intersection of 277th Street and 476th Avenue. Damage was limited to crops with the path defined on Sentinel satellite imagery. The average path width was 20 yards.

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

7 minutes of warning. NWS FSD issued a tornado warning for this county at 21:23 UTC, 7 minutes before the tornado touched down, in force until 22:00 UTC.

The county was under a severe thunderstorm watch, issued at 21:00 UTC and running to 04:00 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 Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 19:51 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.

Sioux Falls (FSD), 23 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Sioux Falls radar (KFSD), 25 km away, was scanning. The volume nearest the touchdown began at 21:30 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 South DakotaEvery tornado in South Dakota since 1950Warnings in force in South Dakota nowThe forecast where you are

16 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.