F0 tornado, Dike, Iowa, April 18, 2002

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 18, 2002

Touchdown

6:30 PM CDT (23:30 UTC)

Path length

0.2 miles (0.3 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Property damage

$1,000

County

Grundy County

Touchdown point

42.480, -92.630

Lift-off point

42.480, -92.630

Record number

502

A strong southerly flow was well established over the central U.S. Temperatures pushed well into the 80s during the afternoon. Surface dew point temperatures rose into the mid 60s to low 70s across the state. Initially, the atmosphere was capped. By the late afternoon hours the cap broke as the cold front pushed into the state from the northwest. Thunderstorms developed rapidly into a scattered to broken line. Hail was widespread with the storms with sizes ranging up to 2 inches in diameter. Two inch hail was reported at Brooklyn in Poweshiek County as well as southwest of Bedford in Taylor County. There were numerous reports of golf ball size hail with the storms. Windows were shattered with some of the larger hail with a few reports of damage to vinyl siding on houses. A few of the storms produced high winds. Winds of 65 MPH were reported in Hardin County south of Hubbard. Winds were around 80 MPH in Madison County, toppling power poles. There were several tornadoes with the squall line. The first tornadoes touched down in the northeast part of the state. They did not cause much damage as one touched down briefly in Hardin County, another in Grundy County. A short time later a tornado made a brief touch down north of Altoona in Polk County. Another tornado touched down between Bondurant and Elkhart. This tornado was the strongest of the afternoon and tracked southeast toward the Mitchellville area. Damage was reported to power lines and out buildings along the path. Fortunately the track did not move through a populated area. The last tornado touched down near the Waterloo area southwest of Eagle Center. This was also a brief touch down.

Touched down briefly in open area north of town, causing little damage.

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

26 minutes of warning. NWS DMX issued a tornado warning for this county at 23:04 UTC, 26 minutes before the tornado touched down, in force until 00:00 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 no categorical risk area, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:17 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), 123 km away, was scanning. The volume nearest the touchdown began at 23:29 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 2002 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

13 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.