EF0 tornado, Columbia, Iowa, June 7, 2007

1. EF065 to 85 mphthis tornado

   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 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

EF0

Date

June 7, 2007

Touchdown

12:48 PM CDT (17:48 UTC)

Path length

0.2 miles (0.3 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

County

Marion County

Touchdown point

41.240, -93.150

Lift-off point

41.240, -93.150

Record number

0706071148-01

A very intense low pressure moved from northeast North Dakota into northern Minnesota during the day on the 7th. Strong moisture transport took place during the previous night with a low level jet approaching 90 kts. The surface low fell below 980 mb, making this depth a sigma 5 event for June. During the afternoon, temperature warmed into the 80, while dew points recovered into the 65 to 70 degree range. Dew points at the 850 mb level reached the mid teens C. The atmosphere became unstable with the lifted index falling to the -5 to -8 C. range, and most unstable CAPES in the 2000 J/kg range. Although deep moisture was limited, there were sufficient dynamic forcing. Effective shear was in the 60 to 70 kt range over eastern Iowa with a 40 to 50 kt low level jet in place during the afternoon. LCL levels fell to 1000 to 1250 meters. There was a decent amount of CAPE in the -10 to -30 C. layer with 200 to 300 J/kg available. The freezing level was quite high however, between 14,500 and 15,500 feet. Thunderstorms erupted by the early afternoon as a strong dry line moved into the state. The contrast in dew points was nearly 30 degrees across the dry line with upper 30s to low 40s to the west, and upper 60s to the east. The thunderstorms formed into a scattered line with several discreet supercells along the line. Two tornadoes occurred, one in Marion County, the other in Appanoose. Both were brief touchdowns with little to no damage reported. The only other damage reported with the storms was some scattered wind damage reports. Winds from one of the thunderstorms sank a boat on Lake Redrock at the dock, and several other boats were damaged. With the freezing level quite high, there were few reports of hail and none that reached several levels.

Tornado touched down in open country with no damage reported.

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

20 minutes of warning. NWS DMX issued a tornado warning for this county at 17:28 UTC, 20 minutes before the tornado touched down, in force until 18:15 UTC.

The county was under a tornado watch, issued at 16:35 UTC and running to 00:52 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 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 16:45 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), 73 km away, was scanning. The volume nearest the touchdown began at 17:49 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

11 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.