F0 tornado, Coon Rapids, Iowa, July 6, 1998

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 6, 1998

Touchdown

7:27 PM CDT (00:27 UTC)

Path length

0.2 miles (0.3 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

County

Carroll County

Touchdown point

41.870, -94.700

Lift-off point

41.870, -94.700

Record number

406

Very warm and humid air was in place over Iowa in advance of an approaching frontal system. Dew point temperatures were approaching 80 degrees F. over a large part of Iowa. Initially, a line of thunderstorms developed from southwest Minnesota, southwest into Nebraska. This line progressed southeast during the evening. A couple of things happened during the mid evening hours. The first was the formation of a line of thunderstorms from west central Iowa into central Iowa. The storms produced winds of up to 65 MPH as they moved across Audubon County during the initial development stage. The storms formed along a convergence zone and were slow moving. The second was an acceleration of the line moving in from the west as a speed max approached. During the mid and late evening hours, the portion of the northeast to southwest oriented line over northwest Iowa turned into a bow echo and raced southeast across the state. A small tornado touched down in Carroll County. The main severe weather feature with the storms was high winds as the bow echo advanced south and east across Iowa. Winds of 60 to 70 MPH were common along the line. Numerous trees and power lines were downed by the winds. The winds resulted in scattered power outages, the worst of which was in the Des Moines metropolitan area where 9000 were without power for several hours after the storms passed. The other problem was with flooding. The main problem was with the northwest to southeast oriented line since it was very slow moving. The airmass being fairly tropical in nature resulted in large amounts of rainfall over several counties. Flash flooding occurred in Dallas, Polk, and Guthrie Counties. Widespread rainfall of 2 to 3 inches occurred, with some areas receiving around 5 inches. Much of the rain fell in about an hour, causing very rapid rises in streams as the ground was saturated at the time it rained. In Guthrie County, evacuations took place in the Lake Panorama area as water overtopped the dam there. Rainfall of 2 to 5 inches occurred in Sac, Carroll, and Greene Counties. This resulted in fairly widespread urban flooding, however rainfall in these areas took several hours to fall and with soils there not as saturated, flooding was not as serious. As the storms moved through Black Hawk County, lightning struck a house in Cedar Falls. Though no serious damage occurred, appliances were damaged and the window frame of one window was blown out. Shreds of the frame flew across the room as the lightning struck.

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

5 minutes of warning. NWS DMX issued a tornado warning for this county at 00:22 UTC, 5 minutes before the tornado touched down, in force until 00:55 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 Moderate Risk. The outlook in force was issued at 10:58 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), 82 km away, was scanning. The volume nearest the touchdown began at 00:25 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 1998 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

10 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.