EF4 tornado, Citico Beach to Lawson Xrds, 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 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 mphthis tornado

   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

EF4

Date

April 27, 2011

Touchdown

7:31 PM EDT (23:31 UTC)

Lifted

7:45 PM EDT (23:45 UTC)

On the ground

14 minutes

Path length

14.4 miles (23.3 km)

Path width

1,320 yards (1207 m)

Deaths

0

Injuries

0

Property damage

$1.1 million

Counties

Blount and Monroe counties

Touchdown point

35.532, -84.050

Lift-off point

35.663, -83.846

Record number

1104271731-01

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.

A massive EF-4 tornado quickly spun up just west of Chilhowee Lake in northern Monroe County that scoured the forest in the Cherokee National Forest. The tornado entered the Lake (at the Blount County line) and smashed a large steel transmission tower. The tornado then entered the Great Smoky Mountains National Park on the other side of the lake and again began to rip through heavy forest.

Chilhowee EF4 Tornado. An NWS survey team reported an EF4 tornado touched down west of Chilhowee Lake in northern Monroe County. The max wind of 170 mph smashed a TVA transmission tower in the Lake, and ground up miles of forest in both Cherokee National Forest, then in Great Smoky Mountains National Park. ||This tornado started in northern Monroe County in the Cherokee National Forest, then crossed Chilhowee Lake where it smash the tower, entering into Blount County. On the far shore of the lake (now in Blount County and also entering the Great Smoky Mountains National Park), it took a right turn at 33.5574/84.0061, traveled ENE deeper into the park, towards Cades Cove. Before getting to Cades Cove it took a left turn near 35.5794/83.9878 and headed to the NE. It finally dissipated about 4 miles north of Cades Cove, still in the Park. Its total path was 14.5 miles long.

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

52 minutes of warning. NWS MRX issued a tornado warning for this county at 22:39 UTC, 52 minutes before the tornado touched down, in force until 23:36 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 19:12 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.

Knoxville Municipal (TYS), 25 km from the path, in the two hours either side.

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

The Knoxville radar (KMRX), 80 km away, was scanning. The volume nearest the touchdown began at 23:30 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.