Tornadoes · United States · Arkansas · 2018

EF0 tornado, Marmaduke, Arkansas, August 20, 2018

This EF0 tornado ran 0.7 miles across Greene County on August 20, 2018, touching down at 5:51 PM CDT and reaching 50 yards wide. It killed nobody, and did $50,000 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 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 20, 2018
Touchdown
5:51 PM CDT (22:51 UTC)
Lifted
5:53 PM CDT (22:53 UTC)
On the ground
2 minutes
Path length
0.7 miles (1.1 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
Property damage
$50,000
County
Greene County
Touchdown point
36.187, -90.343
Lift-off point
36.188, -90.332
Record number
1808201651-01

The damage survey

3 damage points were recorded along this path by NWS MEG, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF0. The highest wind the damage implies is 70 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 passing cold interacted with an unstable airmass to produce severe thunderstorms that spawned weak tornadoes and damaging winds during the late afternoon and early evening hours of August 20th.

This tornado developed along Highway 34 east of Marmaduke. The tornado damaged a few trees and overturned and dragged a semi-trailer designed for carrying grain.

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

The warnings

21 minutes of warning. NWS MEG issued a tornado warning for this county at 22:30 UTC, 21 minutes before the tornado touched down, in force until 23:04 UTC.

The county was under a severe thunderstorm watch, issued at 17:46 UTC and running to 01:00 UTC.

Issued (UTC)ExpiredProductOffice
17:46 UTC01:00 UTCSevere Thunderstorm WatchMEG
22:30 UTC23:04 UTCTornado WarningMEG

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 Enhanced Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:45 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.

Little Rock, AR (KBYH), 12:00Z

10.9 hours before the tornado, 155 km from the path. August 20, 2018.

Skew-T log-pSkew-T log-p diagram, Little Rock, AR at 12:00Z on 2018-08-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 904 joules per kilogram, CIN -46, lifted condensation level 737 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, Little Rock, AR at 12:00Z on 2018-08-20The 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 81 square meters per square second, 0 to 6 km bulk shear 39 knots.193958Sfc1 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
904 J/kg
Mixed-layer CIN
-46 J/kg
Surface CAPE
357 J/kg
Mixed-layer LCL
737 m above ground
0-6 km bulk shear
39 kt
0-1 km bulk shear
13 kt
0-1 km storm-relative helicity
81 m²/s²
0-3 km storm-relative helicity
133 m²/s²
Significant tornado parameter
0.5
Supercell composite
3.7
0-3 km lapse rate
5.0 K/km

Open this sounding in Storm Lab

Little Rock, AR (KBYH), 00:00Z

1.1 hours after it, 155 km from the path. August 21, 2018.

Skew-T log-pSkew-T log-p diagram, Little Rock, AR at 00:00Z on 2018-08-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 72 joules per kilogram, CIN -89, lifted condensation level 1310 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, Little Rock, AR at 00:00Z on 2018-08-21The 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 28 square meters per square second, 0 to 6 km bulk shear 29 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
72 J/kg
Mixed-layer CIN
-89 J/kg
Surface CAPE
672 J/kg
Mixed-layer LCL
1310 m above ground
0-6 km bulk shear
29 kt
0-1 km bulk shear
23 kt
0-1 km storm-relative helicity
28 m²/s²
0-3 km storm-relative helicity
69 m²/s²
Significant tornado parameter
-0.0
Supercell composite
-0.1
0-3 km lapse rate
6.2 K/km

Open this sounding in Storm Lab

The radar

The Memphis radar (KNQA), 103 km away, was scanning. The volume nearest the touchdown began at 22:49 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
22:15 UTCTSTM WND DMGW ParagouldGreene, ARSEVERAL TREES DOWN AROUND PARAGOULD.
22:23 UTCFUNNEL CLOUDWalcottGreene, ARPOSSIBLE TORNADO AROUND WALCOTT AND LIGHT.
22:25 UTCTSTM WND DMG2 W ParagouldGreene, ARLARGE TREE DOWN ON HOUSE ON 707 ROAD.
22:25 UTCTSTM WND DMGE MarmadukeGreene, ARSEMI TRUCK GRAIN HAULER OVERTURNED. OVERTURNED TRAILER HOME AND SEVERAL TREES DOWN AND FARM SHOP DAMAGED MAINLY AROUND THE 700 SERIES OF R0ADS.
22:25 UTCTSTM WND DMGE MarmadukeGreene, ARWIND PICKED UP GRAIN TRAILER AND MOVED IT ABOUT 100 YARDS.
22:25 UTCTORNADOWalcottGreene, ARTORNADO ON GROUND AROUND WALCOTT.
22:25 UTCTORNADOWalcottGreene, ARTORNADO REPORTED NEAR WALCOTT.
22:30 UTCTSTM WND DMG2 W ParagouldGreene, ARLARGE TREE DOWN ON HOUSE ON 707 ROAD.
22:30 UTCTSTM WND DMG3 Ene Crowleys Ridge StGreene, ARSEMI TRUCK GRAIN HAULER OVERTURNED. OVERTURNED TRAILER HOME AND SEVERAL TREES DOWN. MOST DAMAGE OCCURRED ALONG 707 RD.
22:30 UTCTSTM WND DMG3 Ene Crowleys Ridge StGreene, ARWIND PICKED UP GRAIN TRAILER AND MOVED IT ABOUT 100 YARDS.
22:35 UTCTSTM WND DMGParagouldGreene, ARSEVERAL TREES DOWN AROUND PARAGOULD.
22:51 UTCTSTM WND DMG5 E MarmadukeGreene, ARWIND PICKED UP GRAIN TRAILER AND MOVED IT ABOUT 100 YARDS. ALSO DAMGED TO SEVERAL TREES.
23:03 UTCTORNADO5 E MarmadukeGreene, ARBRIEF TORNADO NEAR THE INTERSECTION OF HWY 34 AND GREENE 806 RD. DAMAGE REPORTED TO A FARM SHOP EAST OF MARMADUKE.

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 ArkansasEvery tornado in Arkansas since 1950Warnings in force in Arkansas nowThe forecast where you are

The other tornadoes of August 20, 2018

5 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 203:49 PM CDTEF0Clinton, IA0.515
August 205:27 PM CDTEF1Greene, AR2.4120$500,000
August 206:31 PM CDTEF0Will, IL0.3100
August 205:38 PM MDTEF0Beaverhead, MT0.83
August 208:01 PM CDTEF0Walworth, WI0.7150$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.