EF0 tornado, Okeene, Oklahoma, May 23, 2011

1. EF065 to 85 mphthis tornado

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

2. EF186 to 110 mph

   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

EF0

Date

May 23, 2011

Touchdown

4:26 PM CDT (21:26 UTC)

Lifted

4:28 PM CDT (21:28 UTC)

On the ground

2 minutes

Path length

0.3 miles (0.5 km)

Path width

15 yards (14 m)

Deaths

0

Injuries

0

County

Blaine County

Touchdown point

36.145, -98.344

Lift-off point

36.146, -98.339

Record number

1105231526-01

Widespread severe thunderstorms, including supercells, occurred over a large area of Oklahoma during the afternoon and evening hours of the 23rd. The thunderstorms were focused near two main boundaries. One was a dry line that was set up over the western third of Oklahoma. The other was a stationary front that was draped over northern Oklahoma. More numerous thunderstorms occurred over northern Oklahoma, with more scattered development to the south. A very unstable air-mass was in place, and a well-timed shortwave was rounding a trough in southwest flow toward Oklahoma and northern Texas. Storms began firing by mid afternoon over northwest Oklahoma, with several supercells developing and merging to the east. A short-lived, weak tornado occurred north of Okeene, but occurred over open terrain with no damage. Other supercell storms developed over western and southwest Oklahoma. Although strong mid-level rotation was present with the southern storms, strong low-level rotation was absent. Very large hail occurred with the storms. One supercell produced a six inch diameter hailstone, the largest in Oklahoma history. By early evening, many of the thunderstorms persisted, although with less intensity. A boundary left over from the northern Oklahoma storms was draped over central Oklahoma. The development of the low-level jet aided in the development of supercell thunderstorms with large hail. Hail around golf-ball size fell over parts of the Oklahoma City metro area, along with beneficial rainfall. By midnight, the storms had all weakened below severe limits as they moved into eastern Oklahoma.

Off-duty NWS meteorologists, storm chasers, and local broadcast media confirmed a tornado that lasted 1 to 2 minutes. No known damage occurred.

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

0 minutes of warning. NWS OUN issued a tornado warning for this county at 21:26 UTC, 0 minutes before the tornado touched down, in force until 22:05 UTC.

The county was under a tornado watch, issued at 19:30 UTC and running to 02:43 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 Moderate Risk, with a 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 19:39 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.

Watonga (JWG), 32 km from the path, in the two hours either side.

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

The Vance AFB radar (KVNX), 69 km away, was scanning. The volume nearest the touchdown began at 21:27 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 2011 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are

17 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.