Tornadoes · United States · Iowa · 2018

EF1 tornado, Springbrook, Iowa, September 21, 2018

This EF1 tornado ran 0.3 miles across Jackson County on September 21, 2018, touching down at 1:27 AM CDT and reaching 20 yards wide. It killed nobody, and did $250,000 of property damage.

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 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.

The record

Rating
EF1
Date
September 21, 2018
Touchdown
1:27 AM CDT (06:27 UTC)
Lifted
1:28 AM CDT (06:28 UTC)
On the ground
1 minutes
Path length
0.3 miles (0.5 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
Property damage
$250,000
County
Jackson County
Touchdown point
42.204, -90.468
Lift-off point
42.205, -90.462
Record number
1809210027-01

The damage survey

5 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 100 mph.

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 cold front passed through the region in the evening and overnight hours with a line of showers and storms. One storm produced a brief tornado.

An EF-1 tornado damaged and uprooted trees, snapped a power pole, and caused roof damage. Maximum wind speed was estimated around 100 mph. The tornado was on the ground less than 1 minute and travelled a little more than a quarter mile.

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

The warnings

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

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 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), 00:00Z

6.5 hours before the tornado, 65 km from the path. September 21, 2018.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2018-09-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1221 joules per kilogram, CIN -53, lifted condensation level 1727 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 00:00Z on 2018-09-21The 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 195 square meters per square second, 0 to 6 km bulk shear 36 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
1221 J/kg
Mixed-layer CIN
-53 J/kg
Surface CAPE
1978 J/kg
Mixed-layer LCL
1727 m above ground
0-6 km bulk shear
36 kt
0-1 km bulk shear
27 kt
0-1 km storm-relative helicity
195 m²/s²
0-3 km storm-relative helicity
274 m²/s²
Significant tornado parameter
0.3
Supercell composite
8.9
0-3 km lapse rate
7.5 K/km

Open this sounding in Storm Lab

Davenport, (KDVN), 12:00Z

5.5 hours after it, 65 km from the path. September 21, 2018.

Skew-T log-pSkew-T log-p diagram, Davenport, at 12:00Z on 2018-09-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 5 joules per kilogram, CIN -208, lifted condensation level 644 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 2018-09-21The 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 -32 square meters per square second, 0 to 6 km bulk shear 48 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
5 J/kg
Mixed-layer CIN
-208 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
644 m above ground
0-6 km bulk shear
48 kt
0-1 km bulk shear
28 kt
0-1 km storm-relative helicity
-32 m²/s²
0-3 km storm-relative helicity
55 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.1 K/km

Open this sounding in Storm Lab

The surface observations

Dubuque (DBQ), 29 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
04:30 UTC200° 17 kt1006.8
04:35 UTC200° 18 kt1006.4
04:40 UTC200° 18 kt1006.4
04:45 UTC 18 kt251006.4
04:50 UTC200° 20 kt1006.4
04:53 UTC7969210° 18 kt261006.4
04:55 UTC 21 kt1006.1
05:00 UTC 19 kt1006.1
05:05 UTC200° 18 kt1006.1
05:10 UTC 21 kt1006.1
05:15 UTC 21 kt1005.8
05:20 UTC 19 kt1005.8
05:25 UTC 20 kt1005.8
05:30 UTC 23 kt1005.8
05:35 UTC 19 kt251005.4
05:40 UTC 21 kt281006.1
05:45 UTC 22 kt291007.1
05:50 UTC290° 17 kt1007.5
05:53 UTC7364300° 24 kt431007.1
05:55 UTC 15 kt1007.1
06:00 UTC7264280° 19 kt431007.5
06:05 UTC 15 kt221007.5
06:09 UTC7164270° 21 kt301008.5TS
06:10 UTC280° 22 kt1008.8HZ
06:13 UTC6965290° 22 kt331008.1+TSRA BR
06:15 UTC280° 20 kt1008.1+RA BR
06:19 UTC6866290° 20 kt331008.1+TSRA BR
06:20 UTC280° 19 kt1008.1+RA BR
06:23 UTC6866270° 18 kt301008.5+TSRA BR
06:25 UTC270° 19 kt1008.5RA BR
06:26 UTC6865270° 18 kt301008.5-TSRA BR
06:30 UTC270° 16 kt1008.1RA BR
06:35 UTC270° 14 kt1008.1-RA BR
06:36 UTC6865270° 14 kt281008.1-RA BR
06:40 UTC270° 13 kt201008.1-RA
06:45 UTC270° 12 kt191008.1
06:50 UTC270° 12 kt1008.1
06:53 UTC6765270° 10 kt201008.1
06:55 UTC260° 10 kt1008.1
07:00 UTC260° 9 kt1008.1
07:05 UTC250° 10 kt1008.1
07:10 UTC250° 11 kt1008.1
07:15 UTC250° 11 kt1008.1
07:20 UTC260° 12 kt1008.1
07:25 UTC260° 10 kt1007.8
07:30 UTC250° 10 kt1008.1
07:35 UTC250° 10 kt1008.1
07:40 UTC250° 9 kt1008.1
07:45 UTC240° 10 kt1008.1
07:50 UTC240° 10 kt151008.1
07:53 UTC6664230° 10 kt1008.5
07:55 UTC240° 9 kt1008.1
08:00 UTC240° 11 kt1008.1
08:05 UTC230° 8 kt1007.8-RA
08:10 UTC230° 11 kt1008.1-RA
08:15 UTC230° 10 kt1008.1-RA
08:20 UTC220° 9 kt1007.8-RA
08:25 UTC220° 9 kt1007.5-RA

From the Iowa Environmental Mesonet's archive of airport observations.

The radar

The Quad Cities radar (KDVN), 67 km away, was scanning. The volume nearest the touchdown began at 06:29 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
06:27 UTCTORNADO3 Nne SpringbrookJackson, IAAN EF-1 TORNADO DAMAGED AND UPROOTED TREES, SNAPPED A POWER POLE, AND CAUSED ROOF DAMAGE. MAXIMUM WIND SPEED WAS ESTIMATED AROUND 100 MPH. THE TORNADO WAS ON THE GROUND LESS THAN 1 MINUTE AND TRAVELED A LITTLE MORE THAN
06:30 UTCTSTM WND DMG2 Ne SpringbrookJackson, IAROOF BLOWN OFF HOME WITH TREES AND POWERLINES DOWN IN VICINITY. TIME APPROXIMATE. RELAYED BY ASSISTANT FIRE CHIEF.

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

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.