F1 tornado, Williamsfield, Illinois, June 29, 1998

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

June 29, 1998

Touchdown

4:20 PM CDT (21:20 UTC)

Path length

3.0 miles (4.8 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

1

Property damage

$2.0 million

County

Knox County

Touchdown point

40.880, -90.070

Lift-off point

40.880, -90.000

Record number

1154

A large bow echo system developed over eastern Iowa and moved rapidly to the southeast into Illinois. It moved into Central Illinois's County Warning Area (CWA) around 4 pm in Knox County and exited the CWA (Lawrence County) around 830 pm. Damage was reported in all 35 counties with this system. The overall general area of wind damage was produced by the passage of the bow echo's "gust front" on the leading edge of the line of thunderstorms. Wind speeds were measured or estimated to be between 60 to 80 mph, blowing down or uprooting thousands of trees, tree limbs, power poles, and power lines. Hundreds of trees fell onto structures causing damage ranging from just torn guttering to major roof and structural damage. Also, hundreds of vehicles sustained damage from fallen trees and numerous outbuildings, sheds, and silos were either damaged or destroyed. Considerable crop damage was sustained in most areas. In some areas, more intense damage was observed, caused by stronger wind speeds. Speeds were measured or estimated in these areas at 100 to 110 mph. These areas of damage were apparently "microbursts" produced by a series of mesocyclones that formed on the forward edges of the bow echo. These microbursts, or swaths of more intense wind damage were generally about 1/2 a mile in width. In these areas significant structural damage occurred, such as peeling off roofs, blowing over freight railroad cars, bending steel power poles, and other structural damage. A third phenomena that occurred with this event were spin-up tornadoes along the leading edge of the bow echo structure. These tornadoes caused significant damage in narrow swaths along the bow echo's path and were often masked by the microburst damage occurring adjacent to them. Based on valid spotter observations and mesocyclone signatures on doppler radar, the existence of these tornadoes was validated. Overall, approximately twelve people sustained injuries and damage was estimated around $16 million.

A tornado touched down 3.5 miles southwest of Williamsfield. It destroyed a steel corn crib, blew down a large tree which damaged a home. Also, several windows were blown out on the home. As the tornado travelled east it caused major tree damage for a mile. Then it blew a large tree onto another home and destroyed an empty silo. Next it destroyed a barn and two outbuildings, knocked yet another tree onto a home, as well as, breaking several windows and blowing several 2x4s into the home. Further down the road, the roof and east walls of two homes were destroyed. Then for the last half of a mile, ten power poles were blown down, as well as, numerous trees and a barn sustained moderate damage. One woman sustained minor injuries from flying glass. Damage is estimated around $2 million.

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

33 minutes of warning. NWS ILX issued a tornado warning for this county at 20:47 UTC, 33 minutes before the tornado touched down, in force until 21:45 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 Moderate Risk. The outlook in force was issued at 10:58 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), 93 km away, was scanning. The volume nearest the touchdown began at 21:18 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 1998 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

26 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.