Tornadoes · United States · Iowa · 2018

EF0 tornado, Winfield, Iowa, September 25, 2018

This EF0 tornado ran 0.3 miles across Henry County on September 25, 2018, touching down at 1:26 PM CDT and reaching 20 yards wide. It killed nobody.

The rating scale

Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  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.

The record

Rating
EF0
Date
September 25, 2018
Touchdown
1:26 PM CDT (18:26 UTC)
Lifted
1:27 PM CDT (18:27 UTC)
On the ground
1 minutes
Path length
0.3 miles (0.4 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
County
Henry County
Touchdown point
41.144, -91.489
Lift-off point
41.145, -91.484
Record number
1809251226-01

The damage survey

10 damage points were recorded along this path by NWS DVN, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 107 mph.

  • Convergent damage to corn.

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

What the Weather Service recorded

A line of strong storms tracked east across eastern Iowa during the afternoon hours. These storms produced several tornadoes and damaging wind gusts around 60 mph.

A NWS storm survey team determined a stronger EF0 tornado touched down northwest of Winfield Iowa. Damage to trees and corn was noted along its over a quarter mile path. The max width was estimated to be 20 yards and strongest winds were estimated to be 85 mph.

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

The warnings

7 minutes of warning. NWS DVN issued a tornado warning for this county at 18:19 UTC, 7 minutes before the tornado touched down, in force until 18:31 UTC.

Issued (UTC)ExpiredProductOffice
18:17 UTC19:00 UTCSevere Thunderstorm WarningDVN
18:19 UTC18:31 UTCTornado WarningDVN
18:38 UTC20:51 UTCSevere Thunderstorm WatchDVN
19:12 UTC19:19 UTCTornado WarningDVN

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 forecast that day

The Storm Prediction Center had this point in a Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 16:25 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 air that afternoon

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.

Davenport, (KDVN), 12:00Z

6.4 hours before the tornado, 98 km from the path. September 25, 2018.

Skew-T log-pSkew-T log-p diagram, Davenport, at 12:00Z on 2018-09-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 47 joules per kilogram, CIN -108, lifted condensation level 703 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Davenport, at 12:00Z on 2018-09-25The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 4 square meters per square second, 0 to 6 km bulk shear 41 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
47 J/kg
Mixed-layer CIN
-108 J/kg
Surface CAPE
1 J/kg
Mixed-layer LCL
703 m above ground
0-6 km bulk shear
41 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
4 m²/s²
0-3 km storm-relative helicity
38 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
3.7 K/km

Open this sounding in Storm Lab

Davenport, (KDVN), 00:00Z

5.6 hours after it, 98 km from the path. September 26, 2018.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2018-09-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -97203, lifted condensation level 728 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Davenport, at 00:00Z on 2018-09-26The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity -92 square meters per square second, 0 to 6 km bulk shear 55 knots.1939587897117Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
-97203 J/kg
Surface CAPE
105 J/kg
Mixed-layer LCL
728 m above ground
0-6 km bulk shear
55 kt
0-1 km bulk shear
10 kt
0-1 km storm-relative helicity
-92 m²/s²
0-3 km storm-relative helicity
67 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.1
0-3 km lapse rate
5.3 K/km

Open this sounding in Storm Lab

The radar

The Quad Cities radar (KDVN), 92 km away, was scanning. The volume nearest the touchdown began at 18:28 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.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
18:26 UTCTORNADO3 Wnw WinfieldHenry, IASTRONGER EF0 TORNADO TOUCHED DOWN NORTHWEST OF WINFIELD IA. DAMAGE TO TREES AND CORN WERE NOTED ALONG ITS LITTLE OVER A QUARTER OF MILE PATH. THE MAX WIDTH WAS ESTIMATED TO BE 20 YARDS. THE STRONGEST WINDS WERE ESTIMATED
18:47 UTCTSTM WND GST 44Iowa City Municipal AirJohnson, IA
18:59 UTCTSTM WND DMG3 Sse NobleHenry, IALARGE TREE LIMB DOWN. NOTED FROM SURVEY.
19:14 UTCTORNADO2 Nnw WinfieldHenry, IAEF1 TORNADO TRAVELED A LITTLE OVER ONE MILE AND CAUSED DAMAGE TO TREES ALONG ITS PATH. SOME HOUSES WERE DAMAGED BY FALLING TREES. THE TORNADO AT ITS WIDEST WAS AROUND 200 YARDS. MAXIMUM WINDS WERE AROUND 95 MPH.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2018 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

The other tornadoes of September 25, 2018

7 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
September 251:30 PM CDTEF1Linn, IA0.120$1,000
September 251:53 PM CDTEF0Cedar, IA0.120$3,000
September 252:14 PM CDTEF1Henry, IA1.1200$2,000
September 258:23 PM EDTEF1Monroe, MI4.3520$500,000
September 258:45 PM EDTEF0Monroe, MI4.1250$300,000
September 258:55 PM EDTEF1Wayne, MI3.3200$500,000
September 2511:53 PM CDTEF1Fentress, TN0.550$15,000

What this means

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.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.