Tornadoes · United States · Tennessee · 2011

EF0 tornado, West Knoxville, Tennessee, June 23, 2011

This EF0 tornado ran 1.0 miles across Knox County on June 23, 2011, touching down at 1:20 AM EDT and reaching 100 yards wide. It killed nobody, and did $40,000 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
June 23, 2011
Touchdown
1:20 AM EDT (05:20 UTC)
Lifted
1:22 AM EDT (05:22 UTC)
On the ground
2 minutes
Path length
1.0 miles (1.6 km)
Path width
100 yards (91 m)
Deaths
0
Injuries
0
Property damage
$40,000
County
Knox County
Touchdown point
35.970, -83.950
Lift-off point
35.968, -83.948
Record number
1106232320-01

What the Weather Service recorded

Scattered thunderstorms developed along a boundary during the evening hours and even continued into the overnight hours. Storm reports were varied and ranged from two tornadoes as well damaging thunderstorm wind. Flooding was also reported.

A NWS storm surveyed reported an EF-0 tornado touched along Western Avenue in Knoxville. It had a path length of around 1 mile and a path width of 100 yards. The max wind of 80 mph downed several trees and powerlines along with causing slight roof damage on 2 homes.

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

The warnings

43 minutes of warning. NWS MRX issued a tornado warning for this county at 04:37 UTC, 43 minutes before the tornado touched down, in force until 05:45 UTC.

Issued (UTC)ExpiredProductOffice
23:28 UTC00:15 UTCSevere Thunderstorm WarningMRX
00:05 UTC00:30 UTCSevere Thunderstorm WarningMRX
00:24 UTC01:00 UTCSevere Thunderstorm WarningMRX
04:37 UTC05:45 UTCTornado WarningMRX
05:38 UTC06:45 UTCSevere Thunderstorm WarningMRX
05:56 UTC09:00 UTCFlood AdvisoryMRX
06:36 UTC09:30 UTCFlash Flood WarningMRX
07:24 UTC08:15 UTCSevere Thunderstorm WarningMRX
09:27 UTC12:30 UTCFlood 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 Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 00:59 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), 00:00Z

5.3 hours before the tornado, 239 km from the path. June 24, 2011.

Skew-T log-pSkew-T log-p diagram, Nashville Metro, TN at 00:00Z on 2011-06-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 1557 joules per kilogram, CIN -3, lifted condensation level 1430 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 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, Nashville Metro, TN at 00:00Z on 2011-06-24The 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 108 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
1557 J/kg
Mixed-layer CIN
-3 J/kg
Surface CAPE
2100 J/kg
Mixed-layer LCL
1430 m above ground
0-6 km bulk shear
36 kt
0-1 km bulk shear
20 kt
0-1 km storm-relative helicity
108 m²/s²
0-3 km storm-relative helicity
222 m²/s²
Significant tornado parameter
0.6
Supercell composite
6.5
0-3 km lapse rate
7.5 K/km

Open this sounding in Storm Lab

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

6.7 hours after it, 239 km from the path. June 24, 2011.

Skew-T log-pSkew-T log-p diagram, Nashville Metro, TN at 12:00Z on 2011-06-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 4 joules per kilogram, CIN -207, lifted condensation level 1220 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, Nashville Metro, TN at 12:00Z on 2011-06-24The 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 34 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
4 J/kg
Mixed-layer CIN
-207 J/kg
Surface CAPE
2 J/kg
Mixed-layer LCL
1220 m above ground
0-6 km bulk shear
34 kt
0-1 km bulk shear
22 kt
0-1 km storm-relative helicity
138 m²/s²
0-3 km storm-relative helicity
474 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1
0-3 km lapse rate
4.0 K/km

Open this sounding in Storm Lab

The radar

The Knoxville radar (KMRX), 54 km away, was scanning. The volume nearest the touchdown began at 05:18 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
04:50 UTCTORNADO5 E Oak RidgeKnox, TNPOSSIBLE TORNADO TOUCHDOWN IN THE EDGEMOOR ROAD AREAOFCLAXTON...NEAR THE BULL RUN STEAM PLANT. REPORTED BY WATE TV.
05:00 UTCTORNADO 16 E Oak RidgeKnox, TNEF1 TORNADO NEAR THE BULL RUN STEAM PLANT. MAX WINDS OF 90 MPH...PATH LENGHT OF 1.5 MILES AND WIDTH OF 80 YARDS.
05:20 UTCTORNADO 0KnoxvilleKnox, TNTORNADO ALONG WESTERN AVE. MAX WINDS OF 80 MPH...PATH LENGTH OF 1 MILE AND WIDTH OF 100 YARDS.
05:20 UTCTORNADOKnoxvilleKnox, TNPOSSIBLE TORNADO TOUCHDOWN NEAR WESTERN AVE/640.NUMEROUS DOWNED TREES AND POWERLINES.
06:05 UTCTSTM WND DMG5 Se DandridgeJefferson, TNSEVERAL TREES DOWN ACROSS THE SOUTHERN THIRD OF THE COUNTY. REPORTED BY DISPATCH.
07:10 UTCFLASH FLOOD4 Sw ClintonAnderson, TNWATER COMPLETELY COVERING THE ROAD ON BLOCKHOUSE VALLEY ROAD. REPORTED BY DISPATCH.
07:30 UTCFLASH FLOODKnoxvilleKnox, TNROADS FLOODED ACROSS THE COUNTY.
07:33 UTCTSTM WND DMG6 Nw SeviervilleSevier, TNPOWER LINES DOWN ON BOYDS CREEK HIGHWAY.
07:35 UTCTSTM WND DMG3 Se DandridgeJefferson, TNNUMEROUS TREES DOWN ACROSS THE SOUTHERN THIRD OF THE COUNTY. REPORTED BY DISPATCH.

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

This ground now

The live radar over the trackEvery 2011 tornado in TennesseeEvery tornado in Tennessee since 1950Warnings in force in Tennessee nowThe forecast where you are

The other tornadoes of June 23, 2011

2 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
June 236:50 PM MDTEF0Bingham, ID0.550$7,000
June 231:00 AM EDTEF1Anderson, TN1.580$50,000

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.