F0 tornado, Rockwell City, Iowa, July 5, 2004

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

July 5, 2004

Touchdown

3:50 PM CDT (20:50 UTC)

Path length

0.2 miles (0.3 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

County

Calhoun County

Touchdown point

42.450, -94.630

Lift-off point

42.450, -94.630

Record number

303

Moderately unstable air was in place over Iowa as an upper level low pressure area lifted northeast across the area. At the surface, low pressure moved into west central Iowa by the early afternoon hours. A warm front extended east from the low across central Iowa. Temperatures warmed into the low to mid 80s south of the front with dew point readings around 70 degrees. CAPE values by late afternoon were in the 2200 J/kg range with lifted indices in the -4 to -5 degree range. Thunderstorms developed by the early afternoon hours. Most of the storms remained well below severe limits. There were a couple exceptions. One storm produced a microburst southwest of Adel in Dallas County. IT downed a narrow area of two to three foot diameter trees. Another storm in Calhoun produced a small tornado north of Rockwell City. The tornado touched down in open country and did not cause any damage to speak of. The main threat with the thunderstorms through the afternoon and evening hours was the heavy rainfall north of the warm front. Rainfall of 2 to 5 inches was reported across the north quarter of the state. Heavy rainfall caused flash flooding in Cerro Gordo County in the Mason City area. Widespread 2 to 3 inch amounts were reported in the city on top of already saturated ground, resulting in flash flooding. In the Rudd area of nearby Floyd County, reports were received of 7.5 inches of rain falling, most of it within just one hour.

Brief tornado touchdown in open fields north of Rockwell City

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 20:21 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), 110 km away, was scanning. The volume nearest the touchdown began at 20:48 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

8 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.