F1 tornado, New Boston, 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

3:40 PM CDT (20:40 UTC)

Path length

1.0 miles (1.6 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Property damage

$10,000

County

Mercer County

Touchdown point

41.170, -91.000

Lift-off point

41.170, -91.000

Record number

1287

Supercell thunderstorms over Iowa intensified into a squall line which moved southeastward causing widespread damage across Eastern Iowa into Western Illinois. In Western Illinois the storms spun up at least three non-supercell tornadoes near New Boston, Keithsburg and Roseville. However, the majority of damage was caused by 60 to greater than 100 mph straightline winds. The strong winds flattened farm fields, damaged roofs, and blew over semitrailers. Numerous trees and power lines downed by the storm resulted in power and telephone outages lasting from a few hours, to several days at the most seriously damaged locations. In Hancock and Henderson counties 30 electrical poles were broken. Illinois utility companies reported that more than 58,000 homes and businesses were affected by outages. Some very large trees at Oquawaka and near the Big River State Forest were uprooted by winds estimated at 90 mph. Damage was heavy to homes, trees and outbuildings in Keithsburg, Blandinsville, Woodhull, Cordova, Little York, Macomb, Good Hope, Colchester, Wyanet, Spring Valley, Hennepin, and Hamilton. The Mercer Couty Fairgrounds at Aledo also reported heavy damage.

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

18 minutes of warning. NWS DVN issued a tornado warning for this county at 20:22 UTC, 18 minutes before the tornado touched down, in force until 21:25 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), 60 km away, was scanning. The volume nearest the touchdown began at 20:42 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.