EF2 tornado, Koszta, Iowa, May 22, 2011

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 mph

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

3. EF2111 to 135 mphthis tornado

   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

EF2

Date

May 22, 2011

Touchdown

2:40 PM CDT (19:40 UTC)

Lifted

2:45 PM CDT (19:45 UTC)

On the ground

5 minutes

Path length

3.9 miles (6.2 km)

Path width

75 yards (69 m)

Deaths

0

Injuries

0

Property damage

$250,000

County

Iowa County

Touchdown point

41.792, -92.206

Lift-off point

41.822, -92.142

Record number

1105221340-01

3 damage points were recorded along this path by NWS DVN, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF2. The highest wind the damage implies is 120 mph.

• A string of 12.power poles snapped, trees snapped off. Stop 2.
• Stop 1. Several outbuildings overturned. A few less sturdy buildings were destroyed. Debris tossed far into field to Northeast.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

A low pressure system over Minnesota pushed a cold front through eastern Iowa and northwest Illinois during the afternoon and night of May 22, sparking some showers and thunderstorms across the region. Some of the storms were severe, producing large hail, damaging winds, and a few tornadoes.

A National Weather Service storm damage survey team determined that a track of EF2 damage extended from 3 miles northwest of Ladora, IA to 6 miles northwest of Marengo, IA. This path is roughly 4 miles long and 75 yards wide. This damage occurred approximately between 240 pm and 245 pm CDT May 22. ||Along the path, trees were damages, portions of a house roof were blown off, and a string of 12 power poles were snapped. Based on the damage, wind speeds were estimated at 120 mph.

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

2 minutes of warning. NWS DVN issued a tornado warning for this county at 19:38 UTC, 2 minutes before the tornado touched down, in force until 20:45 UTC.

The county was under a tornado watch, issued at 17:55 UTC and running to 02:00 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 Slight Risk, with a 0.10 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 16:18 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.

Cedar Rapids (CID), 38 km from the path, in the two hours either side.

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

The Des Moines radar (KDMX), 129 km away, was scanning. The volume nearest the touchdown began at 19:38 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 2011 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

47 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.