Tornadoes · United States · Tennessee · 2018

EF0 tornado, Athens Arpt, Tennessee, March 17, 2018

This EF0 tornado ran 0.4 miles across McMinn County on March 17, 2018, touching down at 7:23 PM EDT and reaching 100 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
March 17, 2018
Touchdown
7:23 PM EDT (23:23 UTC)
Lifted
7:24 PM EDT (23:24 UTC)
On the ground
1 minutes
Path length
0.4 miles (0.6 km)
Path width
100 yards (91 m)
Deaths
0
Injuries
0
County
McMinn County
Touchdown point
35.374, -84.576
Lift-off point
35.373, -84.569
Record number
1803171723-01

The damage survey

3 damage points were recorded along this path by NWS MRX, in the Damage Assessment Toolkit the survey teams carry. The highest wind the damage implies is 85 mph.

  • combine this with the drone footage. RFD damage

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

Thunderstorms developed ahead of an upper level system and surface cold front during the evening hours. Several of these storms produced large hail and wind damage. Funnel clouds were reported as a discrete supercell thunderstorm developed over Southeast Tennessee and moved into Southwest North Carolina. As this supercell moved into Monroe County, Tennessee, a weak tornado developed downing several trees and producing minor structural damage.

The tornado probably started somewhere on the eastern side of the Ridgewood Golf Club and tracked eastward. It went through a patch of trees where many softwoods were uprooted or snapped in the upper part of the trunk. The tornado exited the trees and dissipated a short distance over a field where only a couple of trees were damaged.

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. One was issued for the county at another hour that day.

Issued (UTC)ExpiredProductOffice
22:38 UTC23:30 UTCSevere Thunderstorm WarningMRX
23:21 UTC00:00 UTCSevere Thunderstorm WarningMRX
23:24 UTC23:51 UTCSevere Thunderstorm WarningMRX
23:29 UTC23:50 UTCTornado WarningMRX
23:59 UTC00:24 UTCSevere Thunderstorm WarningMRX

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 19:56 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.

Nashville Metro, TN (KBNA), 12:00Z

11.4 hours before the tornado, 201 km from the path. March 17, 2018.

Skew-T log-pSkew-T log-p diagram, Nashville Metro, TN at 12:00Z on 2018-03-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 69 joules per kilogram, CIN -106, lifted condensation level 772 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°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, Nashville Metro, TN at 12:00Z on 2018-03-17The 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 138 square meters per square second, 0 to 6 km bulk shear 53 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
69 J/kg
Mixed-layer CIN
-106 J/kg
Surface CAPE
2 J/kg
Mixed-layer LCL
772 m above ground
0-6 km bulk shear
53 kt
0-1 km bulk shear
26 kt
0-1 km storm-relative helicity
138 m²/s²
0-3 km storm-relative helicity
118 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.2
0-3 km lapse rate
5.3 K/km

Open this sounding in Storm Lab

Nashville Metro, TN (KBNA), 00:00Z

0.6 hours after it, 201 km from the path. March 18, 2018.

Skew-T log-pSkew-T log-p diagram, Nashville Metro, TN at 00:00Z on 2018-03-18Temperature 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 -86133, lifted condensation level 2357 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°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, Nashville Metro, TN at 00:00Z on 2018-03-18The 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 59 square meters per square second, 0 to 6 km bulk shear 60 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
-86133 J/kg
Surface CAPE
1 J/kg
Mixed-layer LCL
2357 m above ground
0-6 km bulk shear
60 kt
0-1 km bulk shear
15 kt
0-1 km storm-relative helicity
59 m²/s²
0-3 km storm-relative helicity
175 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
8.1 K/km

Open this sounding in Storm Lab

The surface observations

Athens (MMI), 3 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
21:35 UTC73.455.4200° 6 kt1009.5
21:55 UTC73.453.6180° 7 kt1009.1
22:15 UTC71.655.4190° 7 kt1008.8
22:35 UTC69.855.4210° 7 kt1009.1
22:55 UTC69.853.6200° 7 kt1009.1
23:15 UTC66.257.2110° 5 kt1007.8
23:35 UTC62.659330° 21 kt311009.5
23:55 UTC60.857.20° 0 kt1009.5
00:15 UTC5957.20° 0 kt1009.5
00:35 UTC57.257.20° 0 kt1009.5
00:55 UTC60.857.20° 0 kt1009.1
01:15 UTC5957.20° 0 kt1009.1

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

The radar

The Knoxville radar (KMRX), 138 km away, was scanning. The volume nearest the touchdown began at 23:25 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
22:45 UTCHAIL 0.751 Wsw RockwoodRoane, TNREPORTED AT 325 NORTH FRONT STREET ROCKWOOD TN.
22:59 UTCHAIL 0.51 E RockwoodRoane, TNREPORTED AT 174 COUNTRY CLUB ROAD ROCKWOOD TN.
22:59 UTCHAIL 0.51 E RockwoodRoane, TN
23:05 UTCHAIL 1.752 S DecaturMeigs, TNREPORTED BY PUBLIC. HAIL OCCURRED FOR 10 MINUTES.
23:11 UTCHAIL 0.885 Ssw Clear WaterMcminn, TNREPORTED AT COUNTY ROAD 112 WEST OF ATHENS TN. ALSO ESTIMATED 50 MPH WINDS.
23:15 UTCHAIL 1Lenoir CityLoudon, TNQUARTER SIZE HAIL NEAR LENIOR CITY.
23:30 UTCHAIL 1AthensMcminn, TN
23:35 UTCHAIL 12 Se BirchwoodMeigs, TNREPORTED AT 787 RILEY LANE BIRCHWOOD TN.
23:35 UTCHAIL 1.53 N Mount VernonMonroe, TN
23:38 UTCFUNNEL CLOUD5 W EtowahMcminn, TNFUNNEL CLOUD FORMING AND MOVING EAST TOWARD ETOWAH. REPORTED AT COUNTY ROAD 750.
23:40 UTCFUNNEL CLOUD1 E EtowahMcminn, TNFUNNEL CLOUD REPORTED IN EAST ETOWAH.
23:48 UTCHAIL 1.752 N TassoBradley, TN
23:50 UTCHAIL 0.75CharlestonBradley, TN
00:00 UTCHAIL 0.752 Ne BentonPolk, TNREPORTED AT 7200 HWY 411.
00:20 UTCHAIL 1.75BentonPolk, TNSEVERAL REPORTS OF GOLFBALL SIZE HAIL ACROSS POLK COUNTY, TN
00:20 UTCHAIL 1.75BentonPolk, TNSEVERAL REPORTS OF GOLFBALL SIZE HAIL ACROSS POLK COUNTY, TN.
00:53 UTCHAIL 0.88Lenoir CityLoudon, TN

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 TennesseeEvery tornado in Tennessee since 1950Warnings in force in Tennessee nowThe forecast where you are

The other tornadoes of March 17, 2018

4 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
March 177:49 PM EDTEF0Monroe, TN1.2200
March 178:17 PM EDTEF0Cherokee, NC0.6100
March 178:32 PM EDTEF0Clay, NC1.5120
March 179:31 PM EDTEF1White, GA5.1630$500,000

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.