EF1 tornado, Vanoss to Ada, Oklahoma, May 21, 2011

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

May 21, 2011

Touchdown

8:41 PM CDT (01:41 UTC)

Lifted

8:47 PM CDT (01:47 UTC)

On the ground

6 minutes

Path length

3.3 miles (5.3 km)

Path width

150 yards (137 m)

Deaths

0

Injuries

0

County

Pontotoc County

Touchdown point

34.801, -96.820

Lift-off point

34.798, -96.761

Record number

1105211941-01

Supercell storms developed from Lincoln county, south into Murray county. The largest and most severe storm moved over Pontotoc county, with several reports of tornadoes. The tornadoes were generally brief, but some damage did occur west of Ada. The thunderstorms moved into eastern Oklahoma by mid evening.

A number of storm chasers observed a tornado northwest of Vanoss. No known damage occurred.

Spotters and storm chasers observed a relatively brief tornado north-northeast of Vanoss. No known damage occurred.

Spotters and storm chasers observed a tornado develop about 0.5 miles northwest of the community of Center which is located to the west-northwest of Ada. The tornado damaged a few homes in Center as it moved generally east. Monetary damage estimates were not available.

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

17 minutes of warning. NWS OUN issued a tornado warning for this county at 01:24 UTC, 17 minutes before the tornado touched down, in force until 02:15 UTC.

The county was under a tornado watch, issued at 00:10 UTC and running to 02:59 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 Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 01:03 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.

The Norman radar (KTLX), 74 km away, was scanning. The volume nearest the touchdown began at 01:42 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.