F0 tornado, Montezuma, Iowa, June 12, 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

June 12, 2001

Touchdown

11:25 AM CDT (16:25 UTC)

Path length

0.2 miles (0.3 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

County

Poweshiek County

Touchdown point

41.580, -92.630

Lift-off point

41.580, -92.630

Record number

162

The supercell that moved across northern Iowa during the early morning hours left behind a strong outflow boundary. This outflow boundary became established east to west across central Iowa. At the same time a complex of thunderstorms that was generated by a short wave moving across Nebraska advanced toward western Iowa just before sunrise. Though upper level jet divergence was in place, a strong mid level cap was in place through most of the night and the outflow boundary never produced any thunderstorm activity. Temperatures in the mid levels fall significantly around sunrise. The outflow boundary "lit up like a Christmas tree" around sunrise. The thunderstorms became severe quickly and were large hail producers. The storms moved east along the east to west line and also produced copious amounts of rainfall. Initially the threat was the large hail. Numerous reports of one to two inch diameter hail were received through central Iowa. Some of the greatest damage occurred in the Des Moines metropolitan area as golf ball size hail pelted the city. Damage was significant to both roofs as well as cars. Several large car dealerships were hit on the west side of town with significant damage reported. Estimates of damage were in the area of $250,000 to $500,000 each. One off duty NWS employee on the west side has his back window broken out by hail with numerous hail pocks in the car. Initial estimates of damage on the west side of town indicate about 5000 insurance claims for cars at $900 to $1500 each, plus 3000 insurance claims for damages house roofs. Golf ball size hail and 4 inches of rain fell near Grinnell in Poweshiek County. Hail drifted to a depth of 2 to 3 feet deep in places. Crops were totally destroyed as the hail fell for 25 minutes. One farmer in the area reported 1000 acres of crops destroyed. Wind was not a major factor with most of these storms. One high wind report was received in Jasper County south of Prairie City. Several trees were blown down there. In addition, one tornado touched down briefly in the county. The touchdown was in open country west of the town of Montezuma. The tornado did little damage and lifted in a very short time. Focus then shifted to the heavy rainfall. The storms trained along the east west line for several hours. A band of very heavy rain was reported from Greene County, east into Boone, Story, Dallas, and Polk Counties. Rainfall of three to four inches was common in these areas. Numerous roads were closed due to the high water. Water was standing in fields everywhere. Some of the worst damage occurred in Story County as the densely populated area of Ames and Iowa State University was affected. By the mid afternoon hours, the thunderstorms weakened and began to lift north slowly. During the early afternoon hours as the thunderstorms moved through Sac County, lightning struck a tree in the town of Schaller. The tree was split and landed on the house causing several thousand dollars damage.

Brief touchdown in open country.

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

8 minutes of warning. NWS DMX issued a tornado warning for this county at 16:17 UTC, 8 minutes before the tornado touched down, in force until 16:45 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 Slight Risk. The outlook in force was issued at 13:06 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), 92 km away, was scanning. The volume nearest the touchdown began at 16:26 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

35 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.