EF1 tornado, Norge to Laverty, Oklahoma, 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

8:44 PM CDT (01:44 UTC)

Lifted

8:48 PM CDT (01:48 UTC)

On the ground

4 minutes

Path length

2.0 miles (3.2 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Property damage

$15,000

County

Grady County

Touchdown point

34.954, -98.013

Lift-off point

34.980, -98.039

Record number

0708181944-01

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 into southwest Oklahoma between Hollis and Erick during the afternoon hours of Saturday, August 18th. A very tropical airmass was in place along and east of this feature, extending into western and central Oklahoma. 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 several tornadoes reported in Kiowa, Washita, and Grady counties during the late afternoon and early evening hours. Damage was reported east of Hobart, and in Washita county south and east of Cordell. As the evening progressed, a strong low-level jet developed, with additional thunderstorms developing over southwest and central Oklahoma. Remarkably, the center of the tropical depression strengthened between 1 and 7 AM, with a compact area of sustained winds of 35 to 45 MPH concentrated around the center of the depression. Wind gusts of 50 to 80 mph were also reported over parts of central Oklahoma at this time. As with the wind speeds, thunderstorms intensities increased, with two additional tornadoes reported over central Oklahoma Sunday morning. In addition to tornadoes and very strong winds, rainfall rates of over three inches per hour were common, with significant flash flooding reported in numerous counties. Rainfall amounts exceeded five inches over a large area, with some locations receiving eight to ten inches. Rivers and creeks easily exceeded their banks, with water also rising quickly in many towns. Dozens of people were rescued by boat and helicopter as numerous homes and businesses quickly took on water. Unfortunately, six people lost their lives due to the flooding. Monetary values were estimated.

A tornado damaged a mobile home and several trees were snapped southwest of Norge. Monetary damages were estimated.

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 General Thunderstorms 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.

Chickasha Municipal Airport (CHK), 15 km from the path, in the two hours either side.

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

The Norman radar (KTLX), 79 km away, was scanning. The volume nearest the touchdown began at 01:45 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 OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma 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.