F1 tornado, Oskaloosa, Iowa, June 14, 2001

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 14, 2001

Touchdown

4:45 PM CDT (21:45 UTC)

Path length

0.1 miles (0.2 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

Property damage

$40,000

County

Mahaska County

Touchdown point

41.330, -92.620

Lift-off point

41.330, -92.620

Record number

163

The very unstable atmospheric condition over the central U.S. remained unchanged from what it had been during previous days. A strong cold front approached from the west as intense low pressure in the upper atmosphere lifted northeast into South Dakota during the day. Deep moisture was in place over the central U.S. with dew points at the 850 mb level at or approaching 20 degrees C. Numerous boundaries were in place across the state from the previous nights convection. Strong convection developed over Missouri during the early afternoon hours. This convection lifted north into Iowa during the afternoon. A line of severe thunderstorms moved into south central Iowa. This line moved northeast rapidly across the state along with an apparent gravity wave seen in satellite imagery. The main severe weather event was high winds. Though there were a few reports of large hail, most of the hail was no larger than marble size. Numerous reports of 60 to 70 MPH winds were received over south central into northeast Iowa. Tree and power line damage was widespread. As the storms moved through Black Hawk County, high winds swept into La Porte City. Trees were toppled in town. One fell on a police squad car, trapping the officer inside the car for a period of time. The echo pattern of the thunderstorms took on a LEWP (Line Echo Wave Pattern) by late afternoon. The mesoscale vorticity center was quite evident in the radar imagery as it passed over Mahaska County. A small tornado formed near the crest of the wave and touched down northeast of the town of Oskaloosa. Five buildings were damaged at a farm there and 2 x 4's were driven into a hog confinement building. The damage path was approximately one eighth mile long and 100 yards wide.

Brief touchdown on a farm northeast of Oskaloosa. Several buildings damaged.

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.

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 Slight Risk. The outlook in force was issued at 19:41 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 Des Moines radar (KDMX), 102 km away, was scanning. The volume nearest the touchdown began at 21:46 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 2001 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

3 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.