EF1 tornado, Mt Harmony to Calderwood Dam, Tennessee, April 27, 2011

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.

Rating

EF1

Date

April 27, 2011

Touchdown

9:25 PM EDT (01:25 UTC)

Lifted

9:36 PM EDT (01:36 UTC)

On the ground

11 minutes

Path length

12.5 miles (20.1 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

1

Property damage

$300,000

Counties

McMinn and Monroe counties

Touchdown point

35.450, -84.460

Lift-off point

35.530, -84.260

Record number

1104271925-01

Favorable atmospheric conditions resulted in a deadly tornado outbreak across east Tennessee on the 27th. The thunderstorms produced more than 50 tornadoes across the east Tennessee area with 32 deaths and more than 200 injured. The tornadoes produced from light to heavy damage to hundreds of homes and businesses. Hail as large as baseballs was also reported.

Gamble Gap-North Tornado. A NWS storm survey reported an EF0 touched down northwest of Tellico Plains. It formed near Gamble Gap Road near Highway 68 then tracked to near TD Farm Road near Highway 68 where it dissipated. The wind speed at 70 mph downed a few trees.

Sleepy Valley Tornado. A NWS storm survey reported an EF1 tornado touched down south of Madisonville. It formed near Sleepy Valley Road and tracked to near Tellico Lake near Corn Tassel Road then dissipated. The 100 mph wind downed numerous trees.

Gamble Gap-South Tornado. A NWS storm survey reported an EF0 touched down near Tellico Plains. It formed near Gamble Gap Road and Henry Mayfield Road then tracked to near north of Highway 68 where it dissipated. It had a path width of 50 yards and path length of 2 miles. The wind speed at 70 mph downed a few trees.

Englewood-S. Madisonville Tornado. A NWS storm survey reported an EF1 tornado touched down northeast of Englewood. It formed near Carl Lee Road in McMinn County and tracked into Monroe County before dissipating. It had a path width of 200 yards. The 100 mph wind damaged several homes and downed numerous trees and powerlines.

Englewood-S. Madisonville Tornado. A NWS storm survey indicated an EF1 tornado touched down northeast of Englewood in McMinn County and continued into Monroe County. It tracked to near Hopewell Spring Road near Madisonville before dissipating. The 100 mph wind damaged several homes and downed numerous trees and powerlines. One person was injured.

Dog Gap Tornado. The Cherokee National Forest reported this tornado path that was less than a mile south of the EF4 Chilhowee track from two hours earlier. Aerial photographs from this tornado showed heavy tree damage in the heart of the path. The tornado dissipated just before getting to Chilhowee Lake.

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

43 minutes of warning. NWS MRX issued a tornado warning for this county at 00:42 UTC, 43 minutes before the tornado touched down, in force until 01:29 UTC.

The county was under a tornado watch, issued at 20:36 UTC and running to 05:00 UTC.

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 Storm Prediction Center had this point in a Moderate Risk, with a 0.15 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 00:50 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 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.

The Knoxville radar (KMRX), 115 km away, was scanning. The volume nearest the touchdown began at 01:24 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.

Local storm reports within 60 km of the path, in the three hours either side.

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

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

209 more were confirmed in the United States that day.

All 210 of them

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.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.