EF1 tornado, Weldon to Woodburn, Iowa, May 25, 2008

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mphthis tornado

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 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. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 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

EF1

Date

May 25, 2008

Touchdown

6:25 PM CDT (23:25 UTC)

Lifted

6:37 PM CDT (23:37 UTC)

On the ground

12 minutes

Path length

6.8 miles (11.0 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Clarke County

Touchdown point

40.940, -93.690

Lift-off point

40.980, -93.570

Record number

0805251725-01

A very intense upper low was located over the southwest U.S. and lifted northeast during the weekend of the 24th into the morning of the 26th. The seasons first strong push of deep moisture moved into Iowa on the 25th with surface temperatures warming into the mid 80s and dew points surging into the upper 60s to low 70s. Precipitable water values were near 1.5 inches. The dry slot pushed north across the area the previous night as the warm front lifted north. The primary surface low was located over northern Minnesota. A cold front extended south from the low into northwest Iowa. The airmass became very unstable by the mid afternoon hours. MUCAPE rose to between 4000 and 5000 J/kg. Lifted indices fell to -8 to -11 C. There was a considerable amount of both DCAPE at 1000-1500 J/kg and cape in the -10 to-30 C. layer of the atmoshpere, between 400 and 600 J/kg. The freezing level was around 13,200 feet. The environment was quite sheared with effective shear in the 40 to 50 kt range. LCL values were between 1000 and 1500 meters. The airmass was initially capped. During the late afternoon hours, a small cluster of thunderstorms formed over north central into northeast Iowa. The storms became severe very quickly. Initially, the storms dropped hail up to golf ball in size. One became a strong super cell and produced a major tornado. This cell, in addition to being tornadic, also produced hail of baseball to softball in size and winds in excess of 90 MPH. The tornado track was from approximately 2 miles south of Aplington to Parkersburg, then continued to New Hartford and across northern Black Hawk County. The average path width ranged from 0.6 to 0.7 miles near Parkersburg to just north of New Hartford. The path constricted to near one quarter mile wide east of New Hartford to north of Waterloo. The width then increased to near 1.2 miles wide north of Dunkerton before dissipating near the Black Hawk and Buchanan County line. The tornado was on the ground for approximately 43 miles. In addition to the main tornado, a satellite tornado was observed by storm chasers and one off duty NWS employee. It was located south of the main tornado and was on the ground for a little over a mile in Grundy County. Initial reports indicated 9 fatalities with 7 in Parkersburg (pop 1889) and 2 in New Hartford (pop 637). There were at least 50 injuries, with 4 of those in critical condition. Two of the fatalities occurred a few days after the tornado from injuries sustained in the tornado. The last fatality occurred on 7 Nov. A 61 year old female sustained injuries in the stairwell of her home when a 2 x 4 was thrown through her right side lung. She was hospitalized and died several months later of complications. Significant structural damage occurred across the southern end of Parkersburg and along a path to just north of New Hartford. Numerous structures completely destroyed from Parkersburg to near New Hartford. The tornado continued eastward to just north of the Waterloo and Cedar Falls area. Significant damage also occurred north of Dunkerton where the tornado increased to its greatest path width. This storm also produced substantial straight line wind damage along the southern periphery of the storm just south of the tornado track. News accounts indicated that a receipt from Parkersburg was found around 1915 CST 3 miles north of Prairie du Chien, WI, 109 miles to the northeast. Receipits were also found in Clayton County at Elkader, and full scrapbook pages and photos were found in far northeast Bremer County at Sumner. Preliminary estimates that straight line winds of 90 to 100 MPH occurred with this storm. At 1637 CST, the Waterloo Airport recorded a 93 MPH wind gust. Survey results suggest that straight line wind damage was the cause of the severe damage at the recreational vehicle dealership north of Cedar Falls. At least 627 homes were damaged, including 288 homes destroyed in Parkersburg, 88 in New Hartford, 15 in Hazelton and another 50 in Black Hawk County. In addition, 58 had major damage, 33 had moderate damage, 2 were inaccessible, and 93 damaged but able to be occupied. There were also 21 businesses destroyed. Governor Chet Culver declared both Butler and Black Hawk disaster areas with both given the State Declaration. A Federal Disaster Declaration occurred two days later for both Butler and Black Hawk Counties. The tornado was rated a low end EF5 by a Quick Response Team (QRT) in portions of Parkersburg and north of New Hartford with peak winds estimated at 205 MPH. For historical reference, the last F5 tornado to hit Iowa was on 13 June 1976 in Boone and Story Counties in the town of Jordan, with a 21 mile path length. The last F4 tornado to hit Iowa was in Union, Madison, and Dallas Counties with a 56 mile path length on 8 April 1999. There was one other smaller tornado during the evening. A tornado touched down in Clarke County and was on the ground for a short time southeast of Osceola. After the initial thunderstorm area developed over north central and northeast Iowa, a large complex developed over southeast Nebraska. The two areas of storms filled in to form a squall line by the mid evening hours. The complex over Nebraska then pushed east and northeast along the squall line. A considerable amount of severe weather was generated during the evening as this occurred. Along the squall line, high winds and hail were common with the dominant mode of severe weather being hail of up to golf ball in size. As the MCS out of Nebraska advanced east, a tail extending south from the centroid took on a bow echo configuration and raced east across Iowa at 65 MPH. Very high winds occurred with this feature with numerous locations reporting winds of 65 to 85 MPH. Some of the higher winds included an 85 MPH wind gust in the Winterset area and numerous reports of 75 to 85 MPH winds from Madison, Dallas, Warren and Polk Counties. Lightning struck a house in Ankeny. The house was set on fire by the strike.

A relatively brief touchdown in fields, resulting in no damage.

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

13 minutes of warning. NWS DMX issued a tornado warning for this county at 23:12 UTC, 13 minutes before the tornado touched down, in force until 23:50 UTC.

The county was under a tornado watch, issued at 20:30 UTC and running to 00:57 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, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:34 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.

Chariton (CNC), 24 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

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 2008 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

31 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.