EF0 tornado, St Charles, Iowa, June 18, 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 18, 2010

Touchdown

4:55 PM CDT (21:55 UTC)

Lifted

4:56 PM CDT (21:56 UTC)

On the ground

1 minutes

Path length

0.6 miles (0.9 km)

Path width

25 yards (23 m)

Deaths

0

Injuries

0

County

Madison County

Touchdown point

41.318, -93.807

Lift-off point

41.321, -93.796

Record number

1006181555-01

The frontal boundary that moved through the state during the previous night retreated northwest and allowed the atmosphere to reload. CAPE rose to 2000 to 3000 J/kg by mid morning with downdraft CAPE values in the 1400 to 1600 J/kg range and available CAPE in the -10 to -30 layer of the atmosphere around 500 J/kg. The freezing level fell slightly from the previous night and was around 13,500 to 14,000 feet. Lifted indices were only in the -1 to -3 C range. The shear was about the same as the previous night, in the 20 to 35 kt range, however precipitable water values fell to 1.1 to 1.5 inches. As the warm air returned, thunderstorms developed before dawn. They increased in strength as a weak shortwave approached the area. The thunderstorms formed into a cluster over northeast Nebraska into western Iowa after sunrise. The small MCS took on a mini bow type configuration. Though there were a few reports of hail of up to an inch in diameter, the primary mode of severe weather was high winds from the bowing system. Wind speeds of 60 to 80 MPH were common along the leading edge of the storm. Tree damage was widespread over a several county wide area. Some property damage was done by the winds as well due to flying debris. The thunderstorms continued southeast into southeast Iowa during the late morning and early afternoon and weakened slowly. Another line of thunderstorms formed over northwest Iowa by late morning and continued into the mid afternoon hours. These storms produced high winds, heavy rainfall, and hail. The hail was generally around an inch in diameter, with the largest being golf ball size in Webster County. Golf ball size hail also fell in Warren County at Milo. Wind speeds were in the 60 to 65 MPH range for the most part, resulting in tree and power line damage. A tornado touched down in open fields in Madison county north of St Charles. The heavy rainfall resulted in some flash flooding as well. Soil conditions across the state were nearly saturated, so a quick 1 to 2 inches of rainfall caused local flash flooding in Black Hawk, Marion, and Tama Counties.

Brief tornado touchdown.

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. One was issued for the county at another hour that day.

The county was under a tornado watch, issued at 19:50 UTC and running to 01:32 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 19:59 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), 46 km away, was scanning. The volume nearest the touchdown began at 21:56 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

1 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.