EF1 tornado, Thornberry, Texas, August 18, 2007

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

August 18, 2007

Touchdown

7:53 PM CDT (00:53 UTC)

Lifted

7:57 PM CDT (00:57 UTC)

On the ground

4 minutes

Path length

1.0 miles (1.6 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

Property damage

$10,000

County

Clay County

Touchdown point

34.083, -98.373

Lift-off point

34.097, -98.367

Record number

0708181853-01

Tropical Storm Erin, the fifth named storm of the 2007 Atlantic Hurricane season, developed quickly over the northeast Gulf of Mexico on the 15th, before moving onshore during the morning hours of the 16th. Erin moved onshore near Lamar, TX as a weak tropical storm, but was quickly downgraded to a tropical depression as it moved over land. The tropical depression moved northwest over the Edwards Plateau toward west Texas. Erin maintained her depression status as it then began to move northeast toward western north Texas during the afternoon hours of Saturday, August 18th. A very tropical airmass was in place along and east of this feature, extending over the entire western north Texas area. Heavy rainfall developed along and east of the center, which moved slowly to the northeast. Low-level wind shear north and east of Erin increased throughout the evening, with one tornado reported in northwest Clay county. Minor damage was reported with this tornado, mainly to some pecan trees. Fortunately, no one was injured with the tornado. As the evening progressed, a strong low-level jet developed, with additional thunderstorms developing and moving over parts of northern Texas. Although very strong winds and tornadoes were reported farther north into Oklahoma during the early morning hours, heavy rain was the main impact in northern Texas. However, flooding was held in check through the morning. Monetary damages were estimated.

A tornado moved north near Thornberry, TX. Several large pecan trees were snapped and a number of birds were found dead. The largest pecan tree was 2 to 3 feet in diameter.

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

15 minutes of warning. NWS OUN issued a tornado warning for this county at 00:38 UTC, 15 minutes before the tornado touched down, in force until 01:15 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 General Thunderstorms Risk, with a 0.02 chance of a tornado within 25 miles. 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.

Wichita Falls/Shep (SPS), 17 km from the path, in the two hours either side.

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

The Altus AFB radar (KFDR), 63 km away, was scanning. The volume nearest the touchdown began at 00:55 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 2007 tornado in TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

4 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.