F0 tornado, Adel, Iowa, May 22, 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

May 22, 2004

Touchdown

7:45 PM CDT (00:45 UTC)

Path length

0.2 miles (0.3 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

County

Dallas County

Touchdown point

41.520, -94.150

Lift-off point

41.520, -94.150

Record number

909

The synoptic situation was very similar to what it was the previous day. A complex weather situation was in place due to the convection from the previous night. An outflow boundary extended east to west across northern Missouri. The synoptic frontal boundary extended from central Nebraska across northern Iowa. The air was clear over Iowa during the day, allowing for temperatures to recover. Dew point values also recovered quite rapidly with readings in the upper 60s to low 70s by the late afternoon hours. Lifted indices dropped into the -5 to -10 C. range by evening with CAPE values approaching 5000 J/kg. By the evening hours, the frontal boundary and outflow boundary had converged and were located along Interstate 80. Explosive thunderstorm development took place during the very late afternoon and evening hours in spite of the weak shear profile. Discrete supercells formed in a narrow line along Interstate 80 from near Des Moines on west. The storms became tornadic quickly. To add insult to injury, a strong thunderstorm complex formed over Nebraska and moved east along the line of convection over Iowa. As the event took shape, all modes of severe weather occurred. The storms developed so rapidly that there was little more than a half hour from the first hail and wind report to the first tornado touchdown. Hail and high wind reports were too numerous to mention individually here. Numerous reports of golf ball size hail were received. Boone and Story Counties reported some of the largest hail with the event as baseball size hail pelted the are. There was one report of very large hail northwest of Slater in Story County. Hail five and one half inches in diameter punched 8 holes through a steel roof. There was severe house siding and roof damage in the area. There were numerous tornadoes, especially in the central Iowa Iowa. At one point there were several supercells around the metropolitan Des Moines area. Two of the stronger tornadoes touched down west and south of Des Moines. Fortunately, most of the tornado tracks were over open areas and resulted in little damage. High winds became a problem, especially after sunset, as the complex from Nebraska moved in. The system became more of a derecho during the late night hours. Eighty plus MPH winds pelted southwest Iowa and downed barns and several buildings in Adams and Cass Counties. A beta bow element formed in central Iowa shortly before midnight. The bow echo produced a measured wind gust of 106 MPH in northern Warren County. The high winds continued to push east along Interstate 80 for the next hour or so before it started to weaken. The other major problem was with heavy rain. The convection from the previous night set the stage by saturating soils. The echos trained for several hours across central Iowa with very heavy rainfall. Rainfall rates of 4 to 5 inches per hour were common under the heavier cells. Several locations received 2 to 5 inch rainfalls in under two hours, resulting in widespread flash flooding. Reports of major highways being inundated by water were common. By the end of the night, a swath of 4 to 9 inch rainfall was evident north of Interstate 80. Longer term river flooding became a major problem by the morning of the 23rd. There were two lightning related injuries. Two people were injured when they were struck by lightning out of doors in Nevada. The lightning struck close by as they were carrying groceries into their home. The jolt caused them to fall, resulting in laceration to the head.

Tornado tracked through open fields for the most part. It also lifted from time to time.

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

35 minutes of warning. NWS DMX issued a tornado warning for this county at 00:10 UTC, 35 minutes before the tornado touched down, in force until 01:00 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 a Moderate Risk, with a 0.15 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 20:01 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), 43 km away, was scanning. The volume nearest the touchdown began at 00:46 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

64 more were confirmed in the United States that day.

All 65 of them

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.