EF0 tornado, Armstrong, Iowa, August 10, 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

August 10, 2010

Touchdown

5:44 PM CDT (22:44 UTC)

Lifted

5:45 PM CDT (22:45 UTC)

On the ground

1 minutes

Path length

0.2 miles (0.3 km)

Path width

40 yards (37 m)

Deaths

0

Injuries

0

County

Emmet County

Touchdown point

43.498, -94.452

Lift-off point

43.500, -94.449

Record number

1008101644-01

Once again the atmosphere over Iowa became very unstable during the peak heating of the day. CAPE rose to 3500-4500 J/kg by the mid to late afternoon with lifted indices of -8 to -10 C. The moisture pooled over the state with precipitable water values approaching 2 inches by evening. High temperatures reached the upper 80s to low 90s, with dewpoints topping out in the upper 70s to low 80s. The atmosphere was fairly weakly sheared with 30 kts of available shear. Downdraft CAPE was between 1000 and 1800 J/kg. Available CAPE in the -10 to -30 C layer of the atmosphere was 800-1100 J/kg, but hail was limited by the high freezing level, 16,000 to 16,500 feet. Quarter size hail fell in Calhoun County as an intense storm passed though. The same storm cluster produced a funnel cloud in Sac County earlier. Scattered winds occurred with the storms. A 61 MPH wind gust was recorded in Eagle Grove for example and windows were blown out in Humboldt County south of Thor. One of the thunderstorms produced a tornado in Emmet County. The tornado touched down briefly over Lake Iowa. Thunderstorms became more organized during the evening and produced very heavy rainfall. In addition to the rainfall, scattered reports of high winds and some hail up to an inch and one quarter in size were received. Most of the wind reports were around 60 MPH. By far the most significant weather was the heavy rainfall. Three to 5 inches of rain fell on saturated ground, resulting in a very widespread flash flood event. Nearly half of the CWA was involved from parts of north central Iowa south to the Missouri border. Numerous roads were covered with flowing water of 1 to 2 feet in depth. Lightning struck a car at mile post 105 on Interstate 35 in Story County. No injuries were reported. Lightning also struck a house in Ankeny, causing a fire. The flash flooding claimed one life in central Iowa. Three vehicles were swept into the waters of Mud Creek near Altoona in Polk County. There were 11 people involved. A rescue call was made to save the occupants of the cars. One 16 year old female perished in the flood waters, the other 10 were rescued, though 4 were injured and received treatment at a local hospital. The flash flooding transitioned into widespread flooding as the night progressed into the day of the 11th. Flash flooding resulted in evacuations of apartments and trailer courts on the east side of Des Moines. Interstate 35 was covered by water due to flash flooding at mile post 97. Several cars spun out in the flood waters. Very intense rainfall in the Ames area resulted in a record crest on Squaw Creek. The creek crested 1.5 to 2.5 feet above the record high stage. Major flooding took place and the water treatment plant was inundated. Major damage was done to several buildings on the Iowa State Campus. Damage to Iowa State alone was between $40,000,000 and $50,000,000. Flooding from the Skunk River closed U.S. Highway 30. Thirty people were rescued at a Wal-Mart store in Ames as well. Following the severe flooding, several Iowa counties were added to the Presidential Disaster Declaration number 1930. The original 32 were: Adams, Appanoose, Audubon, Buena Vista, Butler, Cherokee, Clay, Davis, Decatur, Franklin, Howard, Humboldt, Iowa, Lee, Lyon, Madison, Marion, Mills, Monroe, Montgomery, O���Brien, Osceola, Palo Alto, Ringgold, Shelby, Union, Van Buren, Wapello, Warren, Wayne, Webster and Wright. Eighteen were added to the original, incuding: Black Hawk, Boone, Buchanan, Clayton, Delaware, Dickinson, Dubuque, Emmet, Fayette, Guthrie, Jackson, Jasper, Jones, Lucas, Mahaska, Polk, Sioux and Story. In addition, Governor Chet Culver had issued disaster proclamations for 50 Iowa counties due to inclement weather since June 1, 2010: Appanoose, Black Hawk, Boone, Buchanan, Buena Vista, Butler, Cherokee, Clay, Clayton, Davis, Decatur, Delaware, Dickinson, Dubuque, Emmet, Fayette, Franklin, Hamilton, Hancock, Howard, Humboldt, Jackson, Jasper, Jefferson, Johnson, Jones, Kossuth, Lee, Lucas, Lyon, Mahaska, Marion, Monona, Monroe, O'Brien, Osceola, Palo Alto, Polk, Ringgold, Shelby, Sioux, Story, Taylor, Union, Van Buren, Wapello, Warren, Washington, Webster and Wright.

A tornado formed and touched down briefly over Iowa Lake.

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 18:46 UTC and running to 01:00 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 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:07 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 Minneapolis radar (KMPX), 166 km away, was scanning. The volume nearest the touchdown began at 22:45 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.

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.