EF1 tornado, Proctor to Cincinnati, Oklahoma, May 20, 2013

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 20, 2013

Touchdown

6:40 PM CDT (23:40 UTC)

Lifted

6:47 PM CDT (23:47 UTC)

On the ground

7 minutes

Path length

8.0 miles (12.9 km)

Path width

500 yards (457 m)

Deaths

0

Injuries

0

Property damage

$225,000

Counties

Adair and Washington counties

Touchdown point

35.982, -94.614

Lift-off point

36.060, -94.511

Record number

1305201740-01

24 damage points were recorded along this path by NWS TSA, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 107 mph.

• Large limbs snapped in this area and barn damaged
• Apparent ending point of EF1 tornado
• Large limbs snapped off trees; trees split in this area.
• Several trees snapped or uprooted in this area

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

Severe thunderstorms developed along a nearly stationary frontal boundary over central Oklahoma during the early afternoon hours of the 20th. Very unstable air combined with strong low-level and deep-layer shear resulted in long-lived supercells forming over central Oklahoma and moving eastward into eastern Oklahoma. Several tornadoes occurred from these storms across Osage, Washington, and Nowata Counties. The storms organized into bow echos and line segments over eastern Oklahoma, from which several other tornadoes developed during the early evening hours across Ottawa, Adair, and Le Flore Counties. Damaging wind and large hail was also widespread across the region from these storms.

Severe thunderstorms developed along a nearly stationary frontal boundary over central Oklahoma during the early afternoon hours of the 20th. Very unstable air combined with strong low-level and deep-layer shear resulted in long-lived supercells forming over central Oklahoma and moving eastward into eastern Oklahoma. The storms organized into bow echos and line segments over eastern Oklahoma, from which several other tornadoes developed during the early evening hours. One such tornado moved into northwestern Arkansas dissipating north of Cincinnati in Washington County. Two other tornadoes developed in Benton County. Damaging wind and large hail was also widespread across the region from these storms.

This tornado uprooted trees and snapped a few other trees. Based on this damage, maximum estimated wind in the tornado was 95 to 105 mph.

This tornado snapped or uprooted a number of trees and damaged a barn. Based on this damage, maximum estimated wind in the tornado was 100 to 110 mph.

This is the first segment of a two segment tornado. In Adair County, this tornado destroyed two barns and damaged a third barn. It also snapped or uprooted numerous trees as it moved northeast. Based on this damage, maximum estimated wind in this segment of the tornado was 100 to 110 mph. The tornado continued into Washington County, Arkansas, where it dissipated north of the town of Cincinnati.

This is the second and final segment of this tornado. In Washington County, this tornado damaged a home, damaged several barns, and snapped or uprooted numerous trees. Based on this damage, maximum estimated wind in this tornado segment was 100 to 110 mph.

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

4 minutes of warning. NWS TSA issued a tornado warning for this county at 23:36 UTC, 4 minutes before the tornado touched down, in force until 00:05 UTC.

The county was under a tornado watch, issued at 18:10 UTC and running to 00:49 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, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 19:58 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.

Siloam Spring(Awos) (SLG), 20 km from the path, in the two hours either side.

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

The Western Arkansas radar (KSRX), 83 km away, was scanning. The volume nearest the touchdown began at 23:39 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 2013 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are

35 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.