EF1 tornado, Swiss Alp to Ammansville, Texas, May 18, 2021

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 18, 2021

Touchdown

6:42 PM CDT (23:42 UTC)

Lifted

6:52 PM CDT (23:52 UTC)

On the ground

10 minutes

Path length

3.3 miles (5.3 km)

Path width

400 yards (366 m)

Deaths

0

Injuries

0

Property damage

$100,000

County

Fayette County

Touchdown point

29.759, -96.919

Lift-off point

29.790, -96.877

Record number

2105181742-01

14 damage points were recorded along this path by NWS EWX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 100 mph.

• Chaser video showed power poles down on Highway 77.
• Multiple tree branches snapped in the grove of trees off the dirt road.
• South side of building roof structure destroyed, steel piping bent, welds broken, puncture holes from debris on the portion of roof that survived.
• Multiple Cattle shades loss all of the metal roofing panels.

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

An upper level low moved slowly across the southwestern US and generated several rounds of thunderstorms over South Central Texas. Storms during this period produced two tornadoes, damaging winds, large hail, and heavy rain that led to flash flooding. Most of the severe weather occurred in two periods on May 18: the early morning and the late afternoon and evening.

The combination of an NWS damage survey and storm chaser video and documentation has concluded that an EF1 tornado occurred during the early evening hours of May 18th near Swiss Alp, TX in Fayette County. The tornado occurred in a large cluster of storms that were generally moving east across Fayette County. There were multiple mid-level circulations evident on radar during this event. So while a single tornado path has been created, there may have been other smaller satellite tornadoes or vortices that caused minor wind damage in other areas of Fayette County that evening. Storm Chaser video|showed a multi-vortex tornado on the ground near Swiss Alp and this discussion is the best conclusion we have on the path, width and strength of that tornado. Based on video, storm reports, and tree damage, it appears the tornado first touched down around 6:42 PM CDT just west of Hwy 77near the intersection of Hwy 77 and CR 956. Some minor tree damage was found in this area as well as power poles snapped on Hwy 77. As the tornado crossed Hwy 77, it became larger and multi-vortex as it moved northeast across open pasture and farmland. At approximately 6:48 PM CDT it caused significant damage to a cattle farm approximately one mile south of FM 1383. Metal roofing was removed from multiple cattle shade shelters, there was roof damage to|the business office, and partial structure collapse and roof damage to the main covered building, and cattle working area. Several trees had significant trunk and branch damage on the property as well. Metal roofing material was found several hundred yards away. The tornado continued to move northeast and eventually crossed Berger|Rd. Several trees were snapped along Berger Rd. and adjacent properties. It is not totally clear where the tornado dissipated as some sporadic minor tree damage was found farther NE by about a mile. Due to the weak nature of the damage, we elected to end the track just east of Berger Rd. at 6:52 PM CDT. Based on the damage seen on the ground, it is estimated that peak winds were near 100 mph (EF1) and the tornado was several hundred yards wide when it was multi-vortex. It was on the ground for a little over 3 miles.

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

28 minutes of warning. NWS EWX issued a tornado warning for this county at 23:14 UTC, 28 minutes before the tornado touched down, in force until 23:45 UTC.

The county was under a tornado watch, issued at 19:29 UTC and running to 01:59 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 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:54 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.

La Grange/Fayette Regional (3T5), 16 km from the path, in the two hours either side.

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

The Austin/San Antonio radar (KEWX), 109 km away, was scanning. The volume nearest the touchdown began at 23:44 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 2021 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

9 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.