EF1 tornado, Petersburg to Dyersville, 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

7:31 PM CDT (00:31 UTC)

Lifted

7:43 PM CDT (00:43 UTC)

On the ground

12 minutes

Path length

8.5 miles (13.6 km)

Path width

250 yards (229 m)

Deaths

0

Injuries

0

Property damage

$350,000

Counties

Delaware and Dubuque counties

Touchdown point

42.536, -91.270

Lift-off point

42.513, -91.112

Record number

0805251831-01

Heavy rain-producing showers and thunderstorms moved across much of eastern Iowa and northwest and west central Illinois from the evening of May 25th to the early morning of May 26th. Some of the stronger storms also produced tornadoes, damaging winds, and large hail. Buchanan, Delaware, and Dubuque counties in Iowa were hardest hit with the heavy rains, where rainfall totals of 3 to 8 inches fell resulting in flash flooding.

A tornado touched down southwest of Petersburg and moved east for approximately 7 miles to the Delaware-Dubuque county line. Along its path, trees, power poles, and numerous farm outbuildings were damaged. It continued to track into Dubuque County.

Tornado moved from Delaware County into Dubuque County. The tornado moved southeast across New Wine Park, damaging over 1,000 trees. It also damaged a barn and hay shelter before lifting near the intersection of Highway 136 and Floyd Road.

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

48 minutes of warning. NWS DVN issued a tornado warning for this county at 23:43 UTC, 48 minutes before the tornado touched down, in force until 00:45 UTC.

The county was under a tornado watch, issued at 20:33 UTC and running to 01:01 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.

The Quad Cities radar (KDVN), 113 km away, was scanning. The volume nearest the touchdown began at 00:31 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 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.