F4 Loyal Valley tornado, Texas, May 11, 1999

1. F040 to 72 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. F173 to 112 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. F2113 to 157 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. F3158 to 206 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. F4207 to 260 mphthis tornado

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. F5261 to 318 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

F4

Date

May 11, 1999

Touchdown

6:05 PM CDT (23:05 UTC)

Path length

7.0 miles (11.3 km)

Path width

1,400 yards (1280 m)

Deaths

1

Injuries

6

Property damage

$750,000

County

Mason County

Touchdown point

30.680, -99.100

Lift-off point

30.650, -99.000

Record number

1075

A series of supercell thunderstorms ripped across the Heartland and Northwest Hill Country on the afternoon of the 11th. Three tornadoes would touch down, including a devastating F4 tornado north of Loyal Valley in eastern Mason County. One person was killed and 6 others injured as the three-quarters of a mile tornado tracked a 7 mile long path.

A large multiple-vortex tornado ripped through eastern Mason County during the late afternoon hours. The slow moving tornado first touched down near the Llano River 9 miles northwest of Loyal Valley and then travelled a 7-mile long path, finally dissipating 5 miles north of Loyal Valley. This tornado, whose width would reach three-quarters of a mile wide at times, caused widespread devastation. Two homes were completely destroyed, with debris scattered over great distances. Large pieces of a pick-up truck were located three-quarters of a mile away from the house where it had been left. Tragically, one person was killed and 5 others were injured when that same house was destroyed. The people had sought refuge in a car in a stone garage, but as the tornado tore across the garage, debris smashed through the car, killing one man and injuring the remaining occupants. Sixteen other houses were damaged, along with additional barns and outbuildings. Numerous head of cattle and deer were also killed as the tornado passed. When the tornado crossed Farm-to-Market Road 152, a stretch of asphalt 720 feet wide was ripped off of the road surface.

The deaths

1 direct deaths are recorded for this tornado, each with what Storm Data knows of it.

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. One was issued for the county at another hour that day.

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. The outlook in force was issued at 20:00 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.

Junction - Kimble County (JCT), 71 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), 145 km away, was scanning. The volume nearest the touchdown began at 23:07 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.

The live radar over the trackEvery 1999 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

7 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.