EF1 tornado, Delaware to Garber, Iowa, March 31, 2007

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

March 31, 2007

Touchdown

5:29 PM CDT (22:29 UTC)

Lifted

5:41 PM CDT (22:41 UTC)

On the ground

12 minutes

Path length

11.8 miles (19.1 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

0

Property damage

$202,000

Counties

Delaware and Clayton counties

Touchdown point

42.548, -91.350

Lift-off point

42.672, -91.270

Record number

0703311629-01

A seasonally strong low pressure system lifted northeast from northern Kansas to extreme western Iowa, on March 31, 2007. A warm front moved northward into northeast Iowa followed by a cold front sweeping across eastern Iowa into Illinois. These frontal boundaries triggered thunderstorms, and with sufficient low level wind shear, allowed for many to rotate. Most of the thunderstorms produced large hail and damaging wind. However, one storm in particular that crossed over the warm front, produced an EF1 tornado in Delaware county, in northeast Iowa, at about 429 pm CST. The tornado tracked NNE for a total of about 10 miles (part of this track was in Clayton county) and was 200 yards wide, striking eight farmsteads in Delaware county. No one was killed or injured, however 24 cows were killed when a dairy barn collapsed.

The first two tornadoes of 2007 in northeast Iowa hit a couple of farms, damaging buildings and trees. In addition, the public and law enforcement officials reported hail the size of quarters, along with thunderstorm wind gusts estimated between 60 to 65 mph.

This tornado began 5.4 miles north of Delaware, in Delaware county, at about 429 pm CST, and crossed into Clayton county 6 miles east of Edgewood at approximately 437 pm CST. The tornado was rated EF1 (NWS storm survey team), moved north-northeast at 50 mph, and had a total path length of 10 miles and was 200 yards wide. The tornado struck eight farmsteads in Delaware county, producing mostly minor damage to outbuildings and trees. However, at a farm southeast of Greeley, EF1 damage occurred with winds estimated at 81 mph. A dairy barn collapsed, trapping two people that were milking cows under the debris. They were rescued unharmed, but 24 cows were killed. A two-car garage was completely blown off its foundation, but the house next to it had little damage. An eyewitness just southwest of this farmstead reported seeing rotation in the clouds as it descended and struck the dairy barn. Near the Delaware-Clayton county line, a narrow swath of considerable tree damage was noted, with debris carried up a hillside and spread across a road. Path length in Delaware county was more than 7 miles, and damage was estimated at $162,000.|

A tornado, that originally started in Delaware County, Iowa, moved into Clayton County east of Edgewood, and continued northward toward Garber before lifting. This tornado hit a farm and destroyed a machine shed and snapped off trees. Debris was blown into a nearby field, which included boards being stabbed into the ground.

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.

The county was under a tornado watch, issued at 18:47 UTC and running to 23:41 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 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 19:44 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), 126 km away, was scanning. The volume nearest the touchdown began at 22:28 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 2007 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

6 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.