Unrated tornado, Arenzville to Philadelphia, Illinois, May 3, 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

May 3, 2021

Touchdown

4:57 PM CDT (21:57 UTC)

Lifted

4:59 PM CDT (21:59 UTC)

On the ground

2 minutes

Path length

0.5 miles (0.8 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Cass County

Touchdown point

39.885, -90.324

Lift-off point

39.882, -90.316

Record number

2105031557-01

2 damage points were recorded along this path by NWS ILX, in the Damage Assessment Toolkit the survey teams carry.

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

A Mesoscale Convective Vortex (MCV) generated by a large cluster of convection across Kansas during the pre-dawn hours tracked eastward into central Illinois by the late afternoon and evening of May 3rd. Despite weak instability and deep-layer synoptic shear, the MCV was able to enhance the low-level shear and trigger a broken line of convection. One of the cells on the east-southeast flank of the MCV became a supercell and tracked across central Illinois from Cass County southeastward to Coles County before dissipating after dark. That particular storm produced five brief tornado touchdowns and hail as large as half dollars along its path. Another thunderstorm cell further south dropped 2-inch diameter hail in southern Christian County.

A weak tornado touched down in a field about 2.5 miles east-northeast of Arenzville just north of Crum Road at 4:57 PM CDT. The tornado tracked southeastward near the intersection of Crum Road and Thornley Lane and quickly dissipated by 4:59 PM CDT. No damage occurred.

A weak tornado touched down in a field 3 miles south of Virginia just east of IL-78 at 5:05 PM CDT. The tornado tracked southeastward and crossed near the intersection of Hall Road and Conover Road before quickly dissipating by 5:08 PM CDT. No damage occurred.

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

7 minutes of warning. NWS ILX issued a tornado warning for this county at 21:50 UTC, 7 minutes before the tornado touched down, in force until 22:15 UTC.

The county was under a severe thunderstorm watch, issued at 19:48 UTC and running to 23:18 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 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:40 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.

Jacksonville (IJX), 14 km from the path, in the two hours either side.

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

The Lincoln radar (KILX), 89 km away, was scanning. The volume nearest the touchdown began at 22:00 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 IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

30 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.