Tornadoes · United States · Alabama · 2017
EF0 tornado, Dickert to Roanoke, Alabama, December 20, 2017
From Dickert to Roanoke, this EF0 tornado ran 3.2 miles across Randolph County on December 20, 2017, touching down at 10:40 AM CST and reaching 16 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.
EF065 to 85 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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
- December 20, 2017
- Touchdown
- 10:40 AM CST (16:40 UTC)
- Lifted
- 10:45 AM CST (16:45 UTC)
- On the ground
- 5 minutes
- Path length
- 3.2 miles (5.1 km)
- Path width
- 16 yards (15 m)
- Deaths
- 0
- Injuries
- 0
- County
- Randolph County
- Touchdown point
- 33.169, -85.427
- Lift-off point
- 33.160, -85.373
- Record number
- 1712201040-01
The damage survey
4 damage points were recorded along this path by NWS BMX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF0. The highest wind the damage implies is 65 mph.
- Lower DoD used due to split/possible middle rot.
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
A line of thunderstorms pushed eastward through central Alabama during the morning hours on December 20th. Wind shear values were favorable for rotating storms with 0-6km Bulk Shear values near 50 knots and 0-3km Storm Relative Helicity values near 350 m2/s2. Surface based instability also increased during the morning hours, reaching values near 500 j/kg by the time the tornado formed.
NWS meteorologists surveyed damage in eastern Randolph County and determined that the damage was consistent with an EF0 tornado. The weak tornado touched near County Road 865 just north of Highway 22. Several metal roof panels were blown off a barn on County Road 865, with a few instances of snapped tree branches and snapped, slender pine trees noted downstream. A snapped tree was noted within the city limits of Roanoke.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
2 minutes of warning. NWS BMX issued a tornado warning for this county at 16:38 UTC, 2 minutes before the tornado touched down, in force until 16:52 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 00:37 UTC | 10:08 UTC | Dense Fog Advisory | BMX |
| 14:36 UTC | 17:30 UTC | Flood Advisory | BMX |
| 16:38 UTC | 16:52 UTC | Tornado Warning | BMX |
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, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 16:32 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.
Peachtre/Fal Fld, GA (KFFC), 12:00Z
4.7 hours before the tornado, 87 km from the path. December 20, 2017.
- Mixed-layer CAPE
- 11 J/kg
- Mixed-layer CIN
- -31 J/kg
- Surface CAPE
- 218 J/kg
- Mixed-layer LCL
- 572 m above ground
- 0-6 km bulk shear
- 76 kt
- 0-1 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 242 m²/s²
- 0-3 km storm-relative helicity
- 276 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.2
- 0-3 km lapse rate
- 5.5 K/km
Peachtre/Fal Fld, GA (KFFC), 00:00Z
7.3 hours after it, 87 km from the path. December 21, 2017.
- Mixed-layer CAPE
- 506 J/kg
- Mixed-layer CIN
- -8 J/kg
- Surface CAPE
- 293 J/kg
- Mixed-layer LCL
- 457 m above ground
- 0-6 km bulk shear
- 84 kt
- 0-1 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 403 m²/s²
- 0-3 km storm-relative helicity
- 403 m²/s²
- Significant tornado parameter
- 1.4
- Supercell composite
- 7.0
- 0-3 km lapse rate
- 5.5 K/km
The radar
The Maxwell AFB radar (KMXX), 79 km away, was scanning. The volume nearest the touchdown began at 16:39 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) | Report | Where | County | Remark |
|---|---|---|---|---|
| 16:40 UTC | TORNADO | 2 Sw Crystal Lake | Randolph, AL | A BRIEF, BOTTOM-OF-THE-BARREL EF-0 TORNADO MOVED ALONG AN EASTWARD TRACK JUST NORTH OF COUNTY ROAD 22 IN SOUTHERN RANDOLPH COUNTY, RESULTING IN ROOFING DAMAGE TO A BARN AND LIMITED TREE DAMAGE (SNAPPED BRANCHES AND SNAPP |
| 16:43 UTC | TSTM WND DMG | 1 Ese Crystal Lake | Randolph, AL | TREE DAMAGE REPORTED ALONG U.S. HIGHWAY 431 NORTH OF ROANOKE. POSSIBLE TORNADO. |
| 16:45 UTC | TSTM WND DMG | 2 E Crystal Lake | Randolph, AL | DAMAGE TO AT LEAST ONE TREE ALONG COUNTY ROAD 59 NORTH OF ROANOKE. POSSIBLE TORNADO. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2017 tornado in AlabamaEvery tornado in Alabama since 1950Warnings in force in Alabama nowThe forecast where you are
The other tornadoes of December 20, 2017
6 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| December 20 | 1:02 AM CST | EF1 | Jackson Parish, LA | 0.9 | 110 | $75,000 | ||
| December 20 | 1:37 AM CST | EF1 | Jasper, TX | 4.0 | 250 | $30,000 | ||
| December 20 | 1:59 AM CST | EF1 | Calcasieu Parish, LA | 3.0 | 600 | $15,000 | ||
| December 20 | 2:17 AM CST | EF1 | Calcasieu Parish, LA | 4.7 | 600 | $250,000 | ||
| December 20 | 6:35 AM CST | EF1 | Walthall, MS | 9.9 | 80 | |||
| December 20 | 1:15 PM EST | EF0 | Meriwether, GA | 3.2 | 125 | $30,000 |
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.