EF1 tornado, Hobarton, Iowa, September 4, 2018

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

September 4, 2018

Touchdown

3:35 PM CDT (20:35 UTC)

Lifted

3:37 PM CDT (20:37 UTC)

On the ground

2 minutes

Path length

1.2 miles (2.0 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Property damage

$8,000

County

Kossuth County

Touchdown point

43.043, -94.337

Lift-off point

43.057, -94.323

Record number

1809041435-01

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 EF1. The highest wind the damage implies is 90 mph.

• Hog building collapsed when tornado passed over site.

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

Wet conditions continued across the state with yet another round of moderate to heavy rainfall on top of already mostly saturated conditions. A shortwave moving through the upper level flow out of the southwest, a surface front situated to the west and northwest of the state, and strong 850 mb flow were the main contributors to showers and storms. ||Conditions were certainly conducive for heavy rainfall, including MUCAPE of at least 1000 J/kg and ranging up to 2000+ J/kg, precipitable water values near and in excess of 2.0 inches, and strong moisture advection into and through the state throughout the event. Additionally, conditions were relatively favorable for a funnel cloud or brief spin up or two with lifted condensation levels predominantly under 750 m, 0-3 km CAPE values around 175-200 J/kg, and 0-1 km storm relative helicity values around 100-150 m2/s2. ||In the end, a couple of funnel cloud and brief tornado reports were seen across the most favorable areas in northwest Iowa, followed up by nearly exclusively heavy rainfall and flash flooding reports from southwest Iowa into central Iowa and even parts of northern Iowa. Greatest reports included multiple 3+ inch reports across northern and northwest Iowa and 2 day totals in excess of 6 inches into parts of central Iowa.

Brief tornado occurred to the west of Algona producing roof damage to a hog confinement building. The remainder of the path was in rural agricultural land.

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 20:35 UTC and running to 23:33 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 19:52 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), 155 km away, was scanning. The volume nearest the touchdown began at 20:33 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

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.