Tornadoes · United States · Iowa · 2019

EF0 tornado, Grand Mound, Iowa, August 18, 2019

This EF0 tornado ran 0.1 miles across Clinton County on August 18, 2019, touching down at 5:40 AM 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
August 18, 2019
Touchdown
5:40 AM CDT (10:40 UTC)
Lifted
5:41 AM CDT (10:41 UTC)
On the ground
1 minutes
Path length
0.1 miles (0.2 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
County
Clinton County
Touchdown point
41.786, -90.663
Lift-off point
41.786, -90.661
Record number
1908180440-01

What the Weather Service recorded

A line of thunderstorms moved east across the area during the early morning hours of Sunday, August 18. Small hail and downed trees were seen in the Cedar Rapids area and in Cedar county. A brief tornado occurred near Grand Mound, IA around 5:30 am as the storms rolled through the region.

A brief tornado occurred at a farmstead. Numerous tree branches were down, with one tree uprooted. The home had trim and shingle damage, and a window broken. Grass was splattered on the garage and wind driven hail was also noted on west side of home and garage. Maximum 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

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

Issued (UTC)ExpiredProductOffice
10:22 UTC11:00 UTCSevere Thunderstorm WarningDVN
10:44 UTC11:15 UTCSevere Thunderstorm WarningDVN
11:06 UTC12:28 UTCSevere Thunderstorm WatchDVN

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 Marginal Risk. The outlook in force was issued at 06:00 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), 00:00Z

10.7 hours before the tornado, 23 km from the path. August 18, 2019.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2019-08-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 454 joules per kilogram, CIN -70, lifted condensation level 1225 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 2019-08-18The 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 7 square meters per square second, 0 to 6 km bulk shear 37 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
454 J/kg
Mixed-layer CIN
-70 J/kg
Surface CAPE
1999 J/kg
Mixed-layer LCL
1225 m above ground
0-6 km bulk shear
37 kt
0-1 km bulk shear
1 kt
0-1 km storm-relative helicity
7 m²/s²
0-3 km storm-relative helicity
147 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3
0-3 km lapse rate
7.0 K/km

Open this sounding in Storm Lab

Davenport, (KDVN), 12:00Z

1.3 hours after it, 23 km from the path. August 18, 2019.

Skew-T log-pSkew-T log-p diagram, Davenport, at 12:00Z on 2019-08-18Temperature 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 -292, lifted condensation level 1012 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 2019-08-18The 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 -247 square meters per square second, 0 to 6 km bulk shear 46 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
0 J/kg
Mixed-layer CIN
-292 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1012 m above ground
0-6 km bulk shear
46 kt
0-1 km bulk shear
28 kt
0-1 km storm-relative helicity
-247 m²/s²
0-3 km storm-relative helicity
-218 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.2 K/km

Open this sounding in Storm Lab

The radar

The Quad Cities radar (KDVN), 21 km away, was scanning. The volume nearest the touchdown began at 10:41 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
10:23 UTCTSTM WND DMGTiptonCedar, IASMALL TREES DOWN IN TIPTON.
10:30 UTCTSTM WND DMG2 Wnw SunburyCedar, IASPOTTER REPORTED 1 TO 2 INCH DIAMETER TREE LIMBS DOWN BETWEEN DURANT AND BENNET. THE TIME AND LOCATION WERE ESTIMATED.
10:36 UTCTSTM WND DMG1 Ne StocktonScott, IACORRECTS PREVIOUS TSTM WND DMG REPORT FROM 1 NE STOCKTON. CORRECTS PREVIOUS TSTM WND DMG REPORT FROM 1 NE STOCKTON. AT A FARM 7 TREES UPROOTED THAT WERE 30-50 YEARS OLD. TREES LAYING IN THE SAME DIRECTION TOWARDS THE NOR
10:40 UTCTORNADO3 Ssw Grand MoundClinton, IAA CONVERGENT DOWNBURST OCCURRED ON WEST END OF FARMSTEAD THAT CAUSED BRIEF SPIN UP TORNADO ON EASTERN EDGE OF PROPERTY. NUMEROUS TREE BRANCHES WERE DOWN WITH ONE TREE UPROOTED. THE HOME HAD TRIM, SHINGLE DAMAGE, AND A WI
11:00 UTCTSTM WND DMG2 Nne Park ViewScott, IACORRECTS PREVIOUS TSTM WND DMG REPORT FROM 2 NNE PARK VIEW. VIA SOCIAL MEDIA, NUMEROUS LIMBS DOWN IN SCOTT COUNTY PARK BETWEEN 2 TO ALMOST 8 INCHES IN DIAMETER. TIME OF THE EVENT WAS ESTIMATED USING RADAR.
11:00 UTCTSTM WND DMG2 Nne Park ViewScott, IAVIA SOCIAL MEDIA, NUMEROUS LIMBS DOWN IN SCOTT COUNTY PARK BETWEEN 2 TO ALMOST INCHES IN DIAMETER. TIME OF THE EVENT WAS ESTIMATED USING RADAR.

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

This ground now

The live radar over the trackEvery 2019 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.