Tornadoes · United States · Illinois · 2003
F0 tornado, Unity, Illinois, April 25, 2003
This F0 tornado ran 0.3 miles across Alexander County on April 25, 2003, touching down at 2:43 PM CDT and reaching 30 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 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mph
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
- F0
- Date
- April 25, 2003
- Touchdown
- 2:43 PM CDT (19:43 UTC)
- Path length
- 0.3 miles (0.5 km)
- Path width
- 30 yards (27 m)
- Deaths
- 0
- Injuries
- 0
- County
- Alexander County
- Touchdown point
- 37.180, -89.280
- Lift-off point
- 37.180, -89.270
- Record number
- 58
What the Weather Service recorded
A weak tornado, with peak winds estimated near 65 MPH, briefly touched down in woods and fields. The funnel cloud was observed and videotaped by a television news crew from the intersection of Highways 3 and 127, a distance of about 2 miles away. A witness reported that the funnel touched down in a field near the community of Olive Branch. Based on the video and the eyewitness account, it was determined that one or more brief touchdowns occurred. A few trees were blown down in the area of where the funnel appeared to have touched down. The thunderstorm that produced the apparent tornado formed underneath an upper level low and its associated cold pocket.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
No tornado warning for this county appears in the archive as in force at the moment the tornado touched down. One was issued for the county at another hour that day.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 19:32 UTC | 20:00 UTC | Severe Thunderstorm Warning | PAH |
| 20:03 UTC | 20:45 UTC | Tornado Warning | PAH |
| 20:43 UTC | 22:15 UTC | Flash Flood Warning | PAH |
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, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 12:48 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.
Nashville Metro, TN (KBNA), 12:00Z
7.7 hours before the tornado, 266 km from the path. April 25, 2003.
- Mixed-layer CAPE
- 3 J/kg
- Mixed-layer CIN
- -232 J/kg
- Surface CAPE
- 0 J/kg
- Mixed-layer LCL
- 656 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 279 m²/s²
- 0-3 km storm-relative helicity
- 296 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 4.9 K/km
Nashville Metro, TN (KBNA), 00:00Z
4.3 hours after it, 266 km from the path. April 26, 2003.
- Mixed-layer CAPE
- 349 J/kg
- Mixed-layer CIN
- -21 J/kg
- Surface CAPE
- 644 J/kg
- Mixed-layer LCL
- 1010 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km bulk shear
- 25 kt
- 0-1 km storm-relative helicity
- -88 m²/s²
- 0-3 km storm-relative helicity
- -30 m²/s²
- Significant tornado parameter
- -0.1
- Supercell composite
- -0.9
- 0-3 km lapse rate
- 6.7 K/km
The surface observations
Cape Girardeau (CGI), 27 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 17:53 UTC | 65 | 59 | 30° 7 kt | 998.3 | ||
| 18:53 UTC | 66 | 58 | 330° 9 kt | 998.6 | ||
| 19:01 UTC | 66.2 | 57.2 | 330° 6 kt | 998.6 | VCTS | |
| 19:18 UTC | 64.4 | 57.2 | 330° 16 kt | 998.6 | TS | |
| 19:53 UTC | 62 | 58 | 340° 7 kt | 999 | -TSRA | |
| 20:22 UTC | 62.6 | 57.2 | 310° 13 kt | 999.3 | VCTS | |
| 20:53 UTC | 62 | 57 | 310° 14 kt | 999.7 | VCTS | |
| 21:15 UTC | 60.8 | 57.2 | 300° 13 kt | 1000 | VCTS -RA BR | |
| 21:25 UTC | 60.8 | 57.2 | 320° 12 kt | 1000 | RA BR | |
| 21:32 UTC | 60.8 | 57.2 | 340° 10 kt | 1000.3 | RA BR |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The Paducah radar (KPAH), 46 km away, was scanning. The volume nearest the touchdown began at 19:40 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.
This ground now
The live radar over the trackEvery 2003 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are
The other tornadoes of April 25, 2003
14 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| April 25 | 4:55 AM CDT | F0 | Okaloosa, FL | 0.1 | 20 | $10,000 | ||
| April 25 | 5:10 AM CDT | F0 | Okaloosa, FL | 0.1 | 20 | $10,000 | ||
| April 25 | 5:20 AM CDT | F0 | Walton, FL | 0.2 | 75 | $100,000 | ||
| April 25 | 10:42 AM EDT | F0 | Orangeburg, SC | 5.0 | 60 | |||
| April 25 | 10:05 AM CDT | F0 | Gulf, FL | 0.2 | 50 | $250,000 | ||
| April 25 | 11:57 AM CDT | F1 | Pickens, AL | 0.1 | 50 | $100,000 | ||
| April 25 | 2:40 PM EDT | F0 | Alachua, FL | 0.1 | 10 | |||
| April 25 | 2:54 PM EDT | F0 | Glynn, GA | 0.1 | 10 | |||
| April 25 | 3:00 PM EDT | F0 | Suwannee, FL | 1.0 | 50 | |||
| April 25 | 3:05 PM EDT | F0 | Alachua, FL | 0.1 | 10 | |||
| April 25 | 2:25 PM CDT | F0 | Hale, AL | 4.4 | 50 | $103,000 | ||
| April 25 | 4:09 PM CDT | F1 | Marshall, KY | 1.5 | 100 | $30,000 | ||
| April 25 | 3:10 PM MDT | F0 | Fergus, MT | 2.0 | 25 | |||
| April 25 | 4:24 PM CDT | F0 | Elmore, AL | 0.6 | 50 | $40,000 |
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.