EF1 tornado, Oil City to Gilliam, Louisiana, May 11, 2017

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

May 11, 2017

Touchdown

8:31 PM CDT (01:31 UTC)

Lifted

8:34 PM CDT (01:34 UTC)

On the ground

3 minutes

Path length

0.8 miles (1.2 km)

Path width

110 yards (101 m)

Deaths

0

Injuries

0

County

Caddo Parish

Touchdown point

32.798, -93.888

Lift-off point

32.796, -93.875

Record number

1705111931-01

28 damage points were recorded along this path by NWS SHV, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 107 mph.

• Several snapped trees at the top of the ridge over looking 49. It appears that at least one of the trees fell on some powerlines.
• rectangular fence. 2 sides pushed in, 1 side pushed out.
• roof is gone, but siding looks fine. windows had to be replaced.
• several snapped and uprooted trees.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

Showers and thunderstorms developed over Eastcentral Texas and Southeast Oklahoma during the afternoon hours of May 11th, ahead of a positive tilt upper trough that shifted east across Northern Oklahoma and Southern Kansas. The dryline managed to mix east to near the I-35 corridor by late afternoon, before a cold front associated with the upper trough overtook the dryline and shifted southeast into Southeast Oklahoma an extreme Northeast Texas late. The air mass ahead of the front became moderately unstable by mid to late afternoon, with upper forcing ahead of the trough contributing to an increase in strong to severe thunderstorms across much of East Texas and North Louisiana. Damaging winds and hail were common with the stronger storms, with even isolated tornadoes also spawned across portions of East Texas and Northern Caddo Parish in Northwest Louisiana. These storms weakened by late evening with the loss of instability.

An EF-1 tornado with maximum estimated winds of 95-105 mph initially touched down as a waterspout on Caddo Lake before moving ashore as a tornado at the Earl G. Williamson Park on the south side of Oil City, where it sheared the tops off of several trees and uprooted a large hardwood tree near the shore. The tornado moved over the playground, where it tore a metal roof off of the metal office building at the park and carried portions of the roof into some nearby power lines. The tornado crossed Highway 1 snapping and uprooting severe more trees, and moved over heavily wooded areas near South Land Avenue where additional large branches were downed. The tornado crossed Highway 538 and Texaco Road where several pine trees were uprooted, before moving back over heavily wooded areas and lifting west of Hart Road.

An EF-1 tornado with maximum estimated winds between 95-105 mph touched down just west of a ridge on the west side of Interstate 49 just north of Black Bayou, where several trees were snapped, with one of the trees falling on power lines. The tornado crossed Interstate 49 snapping additional trees adjacent to the northbound lane, and moved over heavily wooded areas and Black Bayou before lifting along Gamm Road about one-third of a mile south of Herndon Magnet School.

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

14 minutes of warning. NWS SHV issued a tornado warning for this county at 01:17 UTC, 14 minutes before the tornado touched down, in force until 01:45 UTC.

The county was under a severe thunderstorm watch, issued at 19:46 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 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 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 Shreveport radar (KSHV), 39 km away, was scanning. The volume nearest the touchdown began at 01:32 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 2017 tornado in LouisianaEvery tornado in Louisiana since 1950Warnings in force in Louisiana nowThe forecast where you are

10 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.