F1 tornado, Aledo to Viola, Illinois, April 30, 2003

1. F040 to 72 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. F173 to 112 mphthis tornado

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. 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.

4. 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.

5. F4207 to 260 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. 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.

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

F1

Date

April 30, 2003

Touchdown

7:08 PM CDT (00:08 UTC)

Path length

0.1 miles (0.2 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Property damage

$500,000

County

Mercer County

Touchdown point

41.180, -90.580

Lift-off point

41.180, -90.580

Record number

839

Supercell thunderstorms developed in the afternoon and evening north of a warm front that ran from Southern Iowa into Central Illinois. Three distinct supercells produced a majority of the wind, hail, and heavy rain reports from Jefferson County Iowa into Henry County Illinois. Mercer County Illinois was under tornado warnings on a continuous basis for 2 hours. Officials at a high school track meet in Aledo, Illinois ushered all students into the safety of the school resulting in no injuries. The training of the supercells from Louisa County Iowa to Henry County Illinois dumped heavy rain over the Edwards River and Pope Creek basins in Illinois with radar estimating 9 inches of rain. Actual amounts varied due to large amounts of hail with the storms. Cambridge Illinois estimated 7 to 8 inches of rain fell in the town. Illinois Route 17 was closed due to flooding between Aledo and Viola with Illinois Route 94 closed south of Aledo. In Andover Illinois, two thirds of the town had basements flooded. Toward the end of the event a bow echo developed in Henry County Illinois and raced east across Bureau and Putnam counties. The fire department in Standard, Illinois measured a 69 knot (80 mph) wind gust when the bow echo moved through. In Clinton, Iowa, a lightning strike started a warehouse fire at the Nestle Purnina Complex.

Damaged farm buildings

traveled through open country

Farm house damaged

House damaged

House pushed 6 feet off foundation

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. One was issued for the county at another hour that day.

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 Moderate Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:21 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.

The Quad Cities radar (KDVN), 48 km away, was scanning. The volume nearest the touchdown began at 00:08 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.

The live radar over the trackEvery 2003 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

21 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.