F1 tornado, Maud, Oklahoma, April 11, 2001

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 mphthis tornado

   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 mph

   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

F1

Date

April 11, 2001

Touchdown

3:00 AM CDT (08:00 UTC)

Path length

5.0 miles (8.0 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Property damage

$40,000

County

Pottawatomie County

Touchdown point

35.170, -96.830

Lift-off point

35.230, -96.850

Record number

610

Six tornadoes across southern Oklahoma and one tornado across western north Texas developed during the overnight hours of the 11th. The most notable tornado formed across Coal County in Oklahoma and resulted in one fatality and one injury as it destroyed a mobile home. In addition to damage produced by severe thunderstorms, sustained winds of 40 to 50 mph with gusts as high as 73 mph developed just ahead of the most frequent period of severe weather and persisted for several hours. In Tillman County, at 2330 CST on the 10th, a barn roof was damaged 3 miles east of Frederick. A barn roof was blown off, and a fence was downed 4 miles east of Frederick, and a house roof sustained minor damage 4 miles north of Frederick. Trees and power lines were downed in Ponca City in Kay County, while in Garfield County, minor but widespread damage, was sustained to trees, power poles, and numerous other structures.

This tornado caused structural damage to oil pumping and storage equipment approximately 2 miles southwest of Harjo and structural damage to trailer homes 1 mile west of Harjo. The beginning and ending times of this tornado were listed incorrectly in the original version of storm data. The beginning time should be 0200 CST, while the ending time should be 0206 CST.

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

4 minutes of warning. NWS OUN issued a tornado warning for this county at 07:56 UTC, 4 minutes before the tornado touched down, in force until 08:30 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. The outlook in force was issued at 05:29 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.

Shawnee Municipal Airport (SNL), 20 km from the path, in the two hours either side.

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

The Norman radar (KTLX), 42 km away, was scanning. The volume nearest the touchdown began at 07:57 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 2001 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are

49 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.