EF0 tornado, St Marys, Iowa, June 5, 2010

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 5, 2010

Touchdown

6:11 PM CDT (23:11 UTC)

Lifted

6:12 PM CDT (23:12 UTC)

On the ground

1 minutes

Path length

1.1 miles (1.8 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

County

Warren County

Touchdown point

41.300, -93.789

Lift-off point

41.296, -93.768

Record number

1006051711-01

A cold front moved southeast into Iowa during the afternoon hours. The airmass remained quite unstable in spite of the convection that took place during the morning. CAPE by mid afternoon was in the 3000 to 4000 J/kg range with lifted indices in the -5 to -8 C range. Shear values were quite high, in the 50 to 70 kt range. The freezing level increased during the day and was around 14,500 feet by the afternoon. Available CAPE in the -10 to -30 C layer of the atmosphere was in the 500 to 700 J/kg range. Significant downdraft CAPE was present in the 700 to 900 J/kg range. Storms formed along the cold front and raced east quite rapidly. Though there was 1.75 inches of precipitable water, the narrowness of the line and the speed of movement limited the rainfall totals. Most of the storms produced wind gusts of 30 to 40 MPH and pea size hail. One storm east of Boone produced high winds, which moved a vehicle that was in park about 10 feet. A narrow line became more cohesive by early evening. A brief spin-up tornado touched down in Warren County east of St. Charles. VORTEX-2 observed the tornado as it crossed the Interstate just south of Highway 92. As the line of storms progressed they turned into a forward propagating system and produced high winds as they crossed Appanoose County.

VORTEX 2 member reported a tornado crossing Interstate 35 south of Highway 92. Tornado dissappeared in the rain east of the interstate.

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 20:51 UTC and running to 23:50 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 20:00 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.

Des Moines (DSM), 28 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), 48 km away, was scanning. The volume nearest the touchdown began at 23:11 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 2010 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

42 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.