F3 tornado, Riceville to Le Roy, Iowa, June 11, 2004

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 mph

   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 mphthis tornado

   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

F3

Date

June 11, 2004

Touchdown

5:56 PM CDT (22:56 UTC)

Path length

12.0 miles (19.3 km)

Path width

150 yards (137 m)

Deaths

0

Injuries

0

Property damage

$190,000

Counties

Howard and Mower counties

Touchdown point

43.400, -92.550

Lift-off point

43.550, -92.570

Record number

1336

A small but intense supercell thunderstorm produced three tornadoes in northeast Iowa. The first tornado touched down about 4 miles southeast of New Haven (Mitchell County), south of 320th Street and between Walnut and Windfall Avenue. It tracked north, primarily in open fields, and lifted between 350th and 360th Street east of New Haven, or just west of Windfall Avenue. The tornado was rated an F1.The second tornado touched down just east of the Mitchell-Howard County line, about 4 miles south of Riceville (Howard County), and also moved straight north. It downed a few trees, but primarily crossed open fields until it reached the southeast side of Riceville. It damaged a few sheds and buildings in Riceville, with mainly tin roofing material and siding blown off. The tornado lifted in Riceville and was rated an F0.The third and most significant tornado formed about 2 miles north of Riceville, again just east of the Mitchell-Howard County line. The tornado tracked north, just east of the county line or Addison Avenue. It grew in strength and at one point was approximately 150 yards wide, hitting several homes and farms (F2 damage). One home lost the roof and all buildings. The tornado was so close to the county line that debris was thrown across Addison Avenue into Mitchell County at times. The dirt and young crops were scoured by the tornado. The tornado crossed into Minnesota just southwest of Le Roy (Mower County), hitting a home directly on the state line. The home, which was built in1900, and several buildings on the lot, were completely demolished (F3 damage).

A tornado crossed the Minnesota-Iowa state line just southwest of Le Roy (Mower County) causing considerable damage. One home right on the state line was completely destroyed, but there were no injuries or deaths. The tornado was approximately 150 yards wide at times and apparently reached F3 damage intensity right on the state line around 6:05 p.m. The tornado then started to weaken, but did heavy damage to a grain company (Koch Industries)(F2 damage) about 2 miles west of Le Roy and continued north, crossing Highway 56 just before 6:10 p.m. The tornado lifted approximately 4 miles northwest of Le Roy in open fields. There were also brief tornado touch downs (all rated F0) near Dexter (Mower County) and Le Roy, as well as areas along the Mower-Fillmore County line west of Spring Valley (Fillmore County).

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

24 minutes of warning. NWS ARX issued a tornado warning for this county at 22:32 UTC, 24 minutes before the tornado touched down, in force until 23:15 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, with a 0.15 chance of a tornado within 25 miles. The outlook in force was issued at 16:31 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 La Crosse radar (KARX), 117 km away, was scanning. The volume nearest the touchdown began at 22:53 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.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2004 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

37 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.