EF0 tornado, Henderson, Minnesota, September 17, 2021

1. EF065 to 85 mphthis tornado

   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. 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

EF0

Date

September 17, 2021

Touchdown

2:34 AM CDT (07:34 UTC)

Lifted

2:35 AM CDT (07:35 UTC)

On the ground

1 minutes

Path length

1.6 miles (2.6 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Property damage

$2,000

Crop damage

$10,000

County

Sibley County

Touchdown point

44.482, -93.952

Lift-off point

44.496, -93.926

Record number

2109170134-01

A line of thunderstorms that originally developed across South Dakota Thursday evening, September 16th, quickly moved eastward over southern Minnesota after midnight. A series of surges along this line caused localized severe wind gusts that produced numerous downed trees and power lines across southern Minnesota. One of the storms produced an EF0 tornado south of Henderson in far southeast Sibley County. ||As this line moved across the southern Metro of the Twin Cities, three tornadoes briefly spun-up leading to multiple power outages, plus major damage to Savage public works building and a large transformer for the city of Savage. In addition, the power outages caused local schools to close temporarily Friday morning. Another area of tornado damage occurred in Apple Valley and Burnsville. Most of this damage was due to trees falling on houses and vehicles.||A 64 mph wind gust was measured by the ASOS at Minneapolis-St. Paul International Airport. At MSP Airport, with the strong winds and possibly brakes not being applied and/or improper chocking, two Sun Country aircraft slid into each other and into jetways H3 and H4, causing fairly significant damage.||Outside the tornadic activity, several sources of private and public weather sensors measured wind speeds of 40 to 55 mph across a wide swath of southern Minnesota. These winds coupled with heavy rainfall, caused numerous downed small trees and large branches across a 25 to 50 mile wide area from Redwood Falls, to St James, then northeast to New Ulm, Shakopee, St. Paul, and into parts of west central Wisconsin.||In addition, near Mankato, MN around 0730 UTC, a 4-year old girl was killed when a tree branch fell on the tent where she and her family were camping. There were approximately 80,000 people without power during the peak of the severity that moved through the metro area.

An EFO tornado tracked through a corn field and knocked down a few large branches in a grove of trees toward the end of the path. The path length was 1.6 miles with a width of 50 yards. Maximum wind speeds were 70 mph.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

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 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.

Mankato (MKT), 30 km from the path, in the two hours either side.

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

The Minneapolis radar (KMPX), 50 km away, was scanning. The volume nearest the touchdown began at 07:32 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 2021 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

3 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.