EF0 tornado, Diagonal, Iowa, May 26, 2013

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

May 26, 2013

Touchdown

7:23 PM CDT (00:23 UTC)

Lifted

7:24 PM CDT (00:24 UTC)

On the ground

1 minutes

Path length

0.1 miles (0.2 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

County

Ringgold County

Touchdown point

40.790, -94.371

Lift-off point

40.788, -94.370

Record number

1305261823-01

1 damage points were recorded along this path by NWS DMX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF0. The highest wind the damage implies is 70 mph.

• Brief Touchdown in Rural Areas. No Damage Reported.

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

The continued series of thunderstorms moved across Iowa during the afternoon of the 26th and through the overnight hours of the 26th into the 27th. A stationary front remained in place from central Nebraska into northern Missouri. The front aloft remained over Iowa, setting the stage for repeated thunderstorm development. The parameters changed little from the previous event. A weakly sheared atmosphere was in place with 25 to 30 kts of shear available. CAPE values were slightly higher, in the 1000 to 2000 J/kg range. Downdraft CAPE ranged from under 400 J/kg over the east part of the CWA to 800 J/kg over the west. A substantial inversion was in place over most of the Des Moines CWA. CAPE in the -10 to -30 C layer of the atmosphere was relatively low, only 200 to 400 J/kg. Precipitable water values were in the 1.3 to 1.6 inch range, or over 2 standard deviations above normal. Thunderstorms from the previous night weakened, only to be replaced by a new round of thunderstorms that developed over northwest Iowa by mid day on the 26th. These storms moved southeast across the state, producing heavy rain across many of the areas that received heavy rainfall the night before. Highway closings were too numerous to mention with many small creeks overflowing their banks and causing flash flooding. There were several reports of road washouts and bridges being washed out. A man driving a SUV was swept away by swift flood waters Monday morning on Westbrook Street in Butler County west of Parkersburg. Severe weather was limited. The storms produced half dollar size hail in Taylor County. Hail also fell in Humboldt and Polk Counties. A funnel cloud was reported in Taylor County as well. One brief tornado touchdown was reported southwest Diagonal in Ringgold County. On the morning of the 27th, as the second MCS decayed, high winds occurred over a small part of north central into central Iowa as a wake low formed. Winds gusted to 58 MPH in Polk County at Ankeny. An RWIS site in Marshall County at Marshalltown recorded a 60 MPH wind gust. Wind damage occurred in Boone County and Hardin Counties. Sustained winds of 40 to 45 MPH were reported in Jasper and Story Counties. Scattered reports of outbuilding and tree damage were received.

A brief tornado touchdown occurred.

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

19 minutes of warning. NWS DMX issued a tornado warning for this county at 00:04 UTC, 19 minutes before the tornado touched down, in force until 00:30 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. 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.

Creston (CSQ), 26 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), 118 km away, was scanning. The volume nearest the touchdown began at 00:20 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 2013 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.