EF1 tornado, Allison Muni Arpt to Shell Rock, Iowa, June 16, 2014

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 mphthis tornado

   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

EF1

Date

June 16, 2014

Touchdown

7:52 PM CDT (00:52 UTC)

Lifted

7:55 PM CDT (00:55 UTC)

On the ground

3 minutes

Path length

2.1 miles (3.4 km)

Path width

120 yards (110 m)

Deaths

0

Injuries

0

Property damage

$200,000

Crop damage

$2,000

County

Butler County

Touchdown point

42.785, -92.632

Lift-off point

42.774, -92.593

Record number

1406161852-01

37 damage points were recorded along this path by NWS DMX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 115 mph.

• two story barn. top story blown off to the east southeast
• 200 yard wide swath of trees snapped to the south. Damage somewhat convergent.
• Structure collapsed to the southeast. Was pushed over. Looked old.
• Empty. Rolled about 75 yards from its foundation. Bin next to it untouched.

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

A very dynamic weather pattern was in place over over Iowa. A warm front lifted north into the state. Temperatures warmed in the 80s with dew point readings in the upper 60s to mid 70s. The atmosphere became very unstable with 3000 to 4000 J/kg of CAPE and downdraft CAPE of 1000 to 1500 J/kg. The shear was strong with 50 to 60 kts available. The freezing level was quite high, between 13,000 and 14,000 feet wtih CAPE in the -10 to -30 C layer of the atmosphere between 700 and 900 J/kg. The precipitable water value was a between 1.5 and 1.8 inches. The LCL was relatively low, around 1000 meters. Thunderstorms moved into western Iowa out of Nebraska. As the afternoon and evening progressed, the thunderstorm complex evolved into one that was more outflow dominated. The system raced southeast and produced high winds across the Des Moines metro area and to the east and south. Winds of 60 to 80 MPH caused considerable tree and power line damage. Power outages were reported by 27,000 customers in Des Moines at the height of the storm. As the storms moved through the heart of Des Moines, a homeless individual died when a large tree branch fell on him at a homeless settlement along the banks of the Raccoon River east of Fluer Blvd.

This is the first of three tornadoes that formed around the Clarksville area. This narrow tornado formed north of Allison and tracked just south of due east, hitting several farmsteads and causing primarily tree damage. The tornado strengthened to an EF1 as it passed over a farmstead towards the end of its track, completely destroying a barn and heavily damaging a shelter belt. The tornado dissipated shortly thereafter as the second tornado passed just to the south.

This second tornado near Clarksville formed just south of tornado #1 as it was in the latter stages of its life. It heavily damaged multiple shelter belts and destroyed several outbuildings on a farmstead before dissipating. It caused EF1 damage to both the shelter belts and the farmstead.

This short-lived tornado formed east of Clarksville and caused damage to multiple shelter belts. It strengthened to an EF1 as it passed over a house and removed part of its roof. The tornado damaged another house a mile further east before dissipating shortly thereafter.

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

17 minutes of warning. NWS DMX issued a tornado warning for this county at 00:35 UTC, 17 minutes before the tornado touched down, in force until 00:56 UTC.

The county was under a tornado watch, issued at 22:41 UTC and running to 05:00 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 Moderate 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 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), 148 km away, was scanning. The volume nearest the touchdown began at 00:50 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 2014 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

35 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.