EF1 tornado, Leola, Alabama, April 20, 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 20, 2011

Touchdown

4:58 AM CDT (09:58 UTC)

Lifted

5:02 AM CDT (10:02 UTC)

On the ground

4 minutes

Path length

2.6 miles (4.2 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

County

Lawrence County

Touchdown point

34.327, -87.374

Lift-off point

34.338, -87.330

Record number

1104200358-01

A long lived quasi-linear convective system (QLCS) developed in northern and central Mississippi and tracked eastward through northern Alabama during the early morning hours of the 20th. A bow echo with a strong meso-vortex produced a long swath of wind damage from southern Franklin across Lawrence, Morgan, Cullman and Marshall counties. Numerous trees were uprooted or snapped, indicating wind speeds of at least 70 mph or higher. Trees were toppled onto two homes in Morgan and Cullman counties resulting in two injuries. As the bow echo continued eastward, numerous reports of trees and damage to small structures were reported. Following the storms, a meteorological phenomenon known as a wake low developed which produced a short period of damaging non-thunderstorm winds in Marshall County. A wind gust of 60 mph was registered with this system at the Albertville, Alabama AWOS station (K8A0). Several power outages were reported through the event.||A mesoscale convective system rolled through northern and central Alabama during the late evening hours of the 20th, and exited shortly after midnight on the 21st. Prolific lightning was generated with mainly elevated thunderstorms within the anvil region of this system across northern Alabama. A line of strong to severe thunderstorms extended south from the upper level circulation center which tracked east from northwest and west central Alabama. The storms produced sporadic thunderstorm wind damage, knocking down several trees in Franklin County. Most of the damage further east were tree limbs that did cause isolated small power outages. Although most areas received one half to one inch of rainfall, there were local amounts of one to just over two inches. This resulted in mostly nuisance minor street flooding, although one road was closed in Franklin County due to more substantial runoff.

A brief EF-1 tornado (95 MPH max winds) touched down on the east side of the Sipsey Wilderness Area, along Forest Service Road (FSR) 208. Numerous trees were snapped and uprooted along a path that tracked nearly 3 miles northeast, corssing Highway 33 and ending around FSR 244 near Black Warrior. This tornado was embedded within a larger line of severe thunderstorms producing damaging straight-line winds. Additional sporadic areas of damage, mainly trees, were seen around the wilderness area.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

The county was under a severe thunderstorm watch, issued at 08:37 UTC and running to 11:30 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 Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 05:22 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.

Haleyville (1M4), 24 km from the path, in the two hours either side.

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

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 AlabamaEvery tornado in Alabama since 1950Warnings in force in Alabama nowThe forecast where you are

11 more were confirmed in the United States that day.

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.