F0 tornado, Gilbertville, Iowa, April 23, 2001

1. F040 to 72 mphthis tornado

   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 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

F0

Date

April 23, 2001

Touchdown

8:15 AM CDT (13:15 UTC)

Path length

0.3 miles (0.5 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Property damage

$40,000

County

Black Hawk County

Touchdown point

42.420, -92.250

Lift-off point

42.420, -92.250

Record number

49

An intense low pressure system lifted northeast out of the Rockies, across northwest Iowa and on into the upper Great Lakes during the afternoon of the 22nd into the 23rd. The dry slot lifted north ahead of the low and passed over Iowa during the early morning hours of the 23rd. Within the dry slot winds of 70 to 85 MPH were common just a few thousand feet above the surface. Shortly after sunrise, a narrow band of showers formed over northeast Iowa. As the showers moved through northeast they produced very gusty winds. In Black Hawk and Bremer Counties, winds were in the 65 to 70 MPH range. Damage was reported around the two counties. Three miles northwest of Washburn in Black Hawk County a farm shed was completely destroyed. In Bremer County, a farm shed was destroyed by the winds near Tripoli and damage to power poles was reported in the Readlyn area. At the onset of the high winds a very narrow squall line developed. Actually, forming near the cold core of the upper low pressure area, convective tops were very low with little if any lightning associated with them. A tornado touched down briefly in Black Hawk County near Gilbertville. One house was damaged and power was cut to three others. The tornado lifted quickly and didn't touch down again until it was east of the Des Moines CWA.

Brief touchdown with minor damage to buildings.

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 General Thunderstorms Risk. The outlook in force was issued at 12:41 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.

Waterloo (ALO), 19 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The live radar over the trackEvery 2001 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

1 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.