F1 tornado, Jacksonville to Prentice, Illinois, April 8, 1999

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 8, 1999

Touchdown

8:27 PM CDT (01:27 UTC)

Path length

9.5 miles (15.3 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

0

County

Morgan County

Touchdown point

39.730, -90.330

Lift-off point

39.830, -90.250

Record number

830

The tornado first touched down half a mile northeast of Sinclair (Morgan County). As it travelled to the northeast, it flipped over a mobile home and destroyed a barn near Yatesville. Nearby two outbuildings and a hog shelter were destroyed. As it approached Prentice, the tornado destroyed a small shed and carried parts of the shed over a nearby house then across the road to a field beyond, about 300 yards away. Windows on the house were blown out. As it continued to the northeast scouring marks could be seen in a field 1 mile southwest of Ashland (Cass County). The tornado entered Ashland on the southwest side of town around 851 PM CDT. It hit a trailer park, destroying 17 trailers and damaging 20. One woman was trapped under her mobile home for several hours. However, she died before they could pull her out. Six other people sustained injuries. As it travelled northeast through town, it destroyed one home, as well as, a city garage, and severely damaged 16 homes, a church, laundromat, and several brick buildings downtown. As it exited town it hit a grain elevator. However, the elevator appears to have broken up the tornado's circulation and no damage was reported to the elevator. North of Highway 125, it appears that the circulation became organized again, but much weaker. Plenty of debris from town was found in the field north of the highway. During a helicopter survey, scouring was evident in the field with the scouring marks splitting into two separate circulations, one going north northeast and the other more east northeast. After a short distance, about half a mile, both of the circulations dissipated. Damage in Ashland was estimated around $1,750,000.

A tornado touched down 5.5 miles west of Jacksonville. It threw a boat off its trailer a quarter of a mile into a neighbor's pond. A house nearby sustained some shingle and window damage and a truck was damaged. As the tornado travelled to the northeast, it blew down dozens of trees and destroyed a barn. Nearby the roof of an airplane hanger was peeled back with the sheet metal thrown into trees. A 2x4 was driven into the southwest side of a house. After the tornado crossed Route 67, it continued to the northeast knocking down trees and power poles. In Arcadia, a barn was severely damaged, several outbuildings were destroyed, a garage was damaged, and roof damage was reported to several homes before the tornado lifted and dissipated. No injuries were reported.

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

11 minutes of warning. NWS ILX issued a tornado warning for this county at 01:16 UTC, 11 minutes before the tornado touched down, in force until 02:00 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 High Risk. The outlook in force was issued at 00:56 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 Lincoln radar (KILX), 91 km away, was scanning. The volume nearest the touchdown began at 01:27 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 1999 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

46 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.