Tornadoes · United States · Illinois · 1991
F1 tornado, McLean County, Illinois, April 29, 1991
This F1 tornado ran 0.2 miles across McLean County on April 29, 1991, touching down at 8:00 PM CDT and reaching 200 yards wide. It killed nobody.
The rating scale
Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
F040 to 72 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mphthis tornado
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
F2113 to 157 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.
F3158 to 206 mph
Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
F5261 to 318 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.
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.
The record
- Rating
- F1
- Date
- April 29, 1991
- Touchdown
- 8:00 PM CDT (01:00 UTC)
- Path length
- 0.2 miles (0.3 km)
- Path width
- 200 yards (183 m)
- Deaths
- 0
- Injuries
- 0
- County
- McLean County
- Touchdown point
- 40.630, -88.980
- Record number
- 397
The warnings
27 minutes of warning. NWS ILX issued a tornado warning for this county at 00:33 UTC, 27 minutes before the tornado touched down, in force until 01:00 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 00:04 UTC | 00:30 UTC | Tornado Warning | ILX |
| 00:33 UTC | 01:00 UTC | Tornado Warning | ILX |
| 01:02 UTC | 02:00 UTC | Tornado Warning | ILX |
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 forecast that day
The Storm Prediction Center had this point in a Slight Risk. The outlook in force was issued at 06:55 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 air that afternoon
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.
Paducah/Barkley, KY (KPAH), 00:00Z
1.0 hours before the tornado, 397 km from the path. April 30, 1991.
- Mixed-layer CAPE
- 7 J/kg
- Mixed-layer CIN
- -127 J/kg
- Surface CAPE
- 38 J/kg
- Mixed-layer LCL
- 847 m above ground
- 0-6 km bulk shear
- 75 kt
- 0-1 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 176 m²/s²
- 0-3 km storm-relative helicity
- 135 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 5.5 K/km
Paducah/Barkley, KY (KPAH), 12:00Z
11.0 hours after it, 397 km from the path. April 30, 1991.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- 0 J/kg
- Surface CAPE
- 0 J/kg
- Mixed-layer LCL
- NaN m above ground
- 0-6 km bulk shear
- 71 kt
- 0-1 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 6 m²/s²
- 0-3 km storm-relative helicity
- 46 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 5.1 K/km
The surface observations
Bloomington/Norm (BMI), 18 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 23:00 UTC | 71.6 | 180° 32 kt | 1000.7 | |||
| 00:00 UTC | 73.4 | 180° 30 kt | 1001 | |||
| 01:00 UTC | 64.4 | 250° 17 kt | 1002.7 | |||
| 02:00 UTC | 62.6 | 260° 18 kt | 1004.1 |
From the Iowa Environmental Mesonet's archive of airport observations.
This ground now
The live radar over the trackEvery 1991 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are
The other tornadoes of April 29, 1991
22 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| April 29 | 8:00 AM CDT | F0 | Jefferson, AL | 0.3 | 33 | |||
| April 29 | 8:03 AM CDT | F0 | Cameron, TX | 0.2 | 10 | $500 to $5,000 | ||
| April 29 | 1:15 PM CDT | F0 | Douglas, NE | 0.1 | 33 | $500 to $5,000 | ||
| April 29 | 1:20 PM CDT | F1 | Pottawattamie, IA | 20.0 | 40 | $50,000 to $500,000 | ||
| April 29 | 2:21 PM CDT | F0 | Pottawattamie, IA | 0.2 | 17 | $500 to $5,000 | ||
| April 29 | 2:25 PM CDT | F0 | Isanti, MN | 1.1 | 10 | |||
| April 29 | 2:25 PM CDT | F1 | Hardin, IA | 3.0 | 40 | $50,000 to $500,000 | ||
| April 29 | 2:35 PM CDT | F1 | Humboldt, IA | 0.1 | 17 | $500 to $5,000 | ||
| April 29 | 2:50 PM CDT | F1 | Pocahontas, IA | 4.0 | 50 | $5,000 to $50,000 | ||
| April 29 | 2:55 PM CDT | F1 | Pocahontas, IA | 0.1 | 17 | $500 to $5,000 | ||
| April 29 | 3:02 PM CDT | F0 | Baldwin, AL | 0.3 | 13 | |||
| April 29 | 3:06 PM CDT | F0 | Baldwin, AL | 0.3 | 20 | $50,000 to $500,000 | ||
| April 29 | 4:20 PM CDT | F1 | Blue Earth, MN | 0.2 | 30 | $5,000 to $50,000 | ||
| April 29 | 4:30 PM CDT | F1 | Blue Earth, MN | 0.2 | 30 | $5,000 to $50,000 | ||
| April 29 | 4:50 PM CDT | F1 | Le Sueur, MN | 0.2 | 50 | 9 | $50,000 to $500,000 | |
| April 29 | 8:15 PM EDT | F0 | Greenwood, SC | 0.1 | 20 | $500 to $5,000 | ||
| April 29 | 7:20 PM CDT | F1 | LaSalle, IL | 10.0 | 100 | $5,000 to $50,000 | ||
| April 29 | 7:30 PM CDT | F0 | Boone, IL | 3.0 | 100 | $5,000 to $50,000 | ||
| April 29 | 7:45 PM CDT | F0 | Woodford, IL | 0.2 | 100 | |||
| April 29 | 7:55 PM CDT | F0 | Winnebago, IL | 0.1 | 100 | |||
| April 29 | 8:26 PM CDT | F0 | DeWitt, IL | 0.2 | 50 | |||
| April 29 | 8:30 PM CDT | F0 | McHenry, IL | 0.1 | 20 |
What this means
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.
Sources
NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.