EF0 tornado, Ames, Iowa, May 29, 2018

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 29, 2018

Touchdown

3:58 PM CDT (20:58 UTC)

Lifted

4:01 PM CDT (21:01 UTC)

On the ground

3 minutes

Path length

0.3 miles (0.5 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Crop damage

$100

County

Story County

Touchdown point

42.053, -93.553

Lift-off point

42.058, -93.554

Record number

1805291458-01

General surface high pressure remained in the region, keeping the area hot. With moisture off the from remnants of Alberto and general southerly flow down to the Gulf of Mexico, moisture was fairly plentiful with surface dew points in the mid to upper 60s. Support for sustained severe weather was fairly lackluster, with limited hail CAPE, negligible effective shear, but overall SBCAPE values did exceed 3000 to 4000 J/kg. DCAPE values were relatively high in excess of 1000 to 1200 J/kg, raising concern for strong downdrafts/microbursts. ||Lingering convection from western Kansas the day before slowly worked towards western Iowa in the morning hours as waves ejected from a western upper level trough. Additionally, weak warm air advection aided initial storm initiation across the western half of Iowa ahead of the larger wave moving off the Rockies. Initially, numerous storms were seen by early afternoon with most being sub-severe. Outflows form early storms also proceeded to initiate subsequent storms, eventually congealing briefly into a linear looking structure. Nearly all severe reports received were wind related from microbursts and collapsing storms as well as one landspout near Ames. Power outages occurred with the storms with at over 9,000 customers without power at one time or another between Ames and Des Moines.

Video of the landspout was obtained via social media. A well-formed landspout occurred in open agricultural fields just east of Interstate 35 near Ames. The landspout remained in ag fields with the only damage to emerging crops as it drifted just west of due north under developing thunderstorms.

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 severe thunderstorm watch, issued at 18:44 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. The outlook in force was issued at 19:58 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.

Ames (AMW), 9 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), 39 km away, was scanning. The volume nearest the touchdown began at 20:57 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 2018 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

6 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.