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.

Tornado in ADAIR, OKLAHOMA
From 20-MAY-13 17:40:00 to 20-MAY-13 17:45:00 (CST-6)
Location: ADDIELEE
Tornado F-scale: EF1
Property damage: 125.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

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.

Thunderstorm Wind in SEQUOYAH, OKLAHOMA
From 20-MAY-13 18:21:00 to 20-MAY-13 18:21:00 (CST-6)
Location: VIAN
Magnitude: 70.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Public

Strong thunderstorm wind blew down trees onto homes and cars.

Thunderstorm Wind in LE FLORE, OKLAHOMA
From 20-MAY-13 20:08:00 to 20-MAY-13 20:08:00 (CST-6)
Location: ARKOMA
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Large tree limbs were blown down by strong thunderstorm wind.

Hail in OSAGE, OKLAHOMA
From 20-MAY-13 14:15:00 to 20-MAY-13 14:15:00 (CST-6)
Location: BIGHEART
Magnitude: 4.25 
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Public

Hail in OSAGE, OKLAHOMA
From 20-MAY-13 15:50:00 to 20-MAY-13 15:50:00 (CST-6)
Location: AVANT
Magnitude: 2.75 
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Post Office

Tornado in ROGERS, OKLAHOMA
From 20-MAY-13 15:34:00 to 20-MAY-13 15:47:00 (CST-6)
Location: TALALA
Tornado F-scale: EF1
Property damage: 30.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is the second and final segment of this tornado. In Rogers County, this tornado remained over open country for much of its life cycle but an NWS damage survey team did find a home that received roof damage and a barn that had two doors blown out by the tornado. A cattle trailer was also thrown across a field. Several trees were also damaged. Based on this damage, maximum estimated wind in the tornado was 95 to 105 mph but video of this tornado indicates that it may have been stronger over open country before it hit the home and barn. Multiple storm spotters and storm chasers photographed the tornado until it dissipated.

Thunderstorm Wind in WASHINGTON, OKLAHOMA
From 20-MAY-13 15:59:00 to 20-MAY-13 15:59:00 (CST-6)
Location: COPAN
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Post Office

Strong thunderstorm wind blew down large tree limbs.

Thunderstorm Wind in LE FLORE, OKLAHOMA
From 20-MAY-13 19:41:00 to 20-MAY-13 19:41:00 (CST-6)
Location: POTEAU
Magnitude: 70.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A building had portions of its roof blown off and several other buildings had windows blown out by strong thunderstorm wind. Numerous trees and power lines were blown down.

Thunderstorm Wind in LE FLORE, OKLAHOMA
From 20-MAY-13 19:14:00 to 20-MAY-13 19:14:00 (CST-6)
Location: TALIHINA
Magnitude: 65.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Strong thunderstorm wind blew down a few trees and power lines.

Thunderstorm Wind in SEQUOYAH, OKLAHOMA
From 20-MAY-13 19:41:00 to 20-MAY-13 19:41:00 (CST-6)
Location: AKINS
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Strong thunderstorm wind blew down trees along Highway 101.

Thunderstorm Wind in MCINTOSH, OKLAHOMA
From 20-MAY-13 16:49:00 to 20-MAY-13 16:49:00 (CST-6)
Location: CHECOTAH
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A police officer reported thunderstorm wind gusts estimated to 65 mph.

Thunderstorm Wind in CRAIG, OKLAHOMA
From 20-MAY-13 17:00:00 to 20-MAY-13 17:00:00 (CST-6)
Location: PYRAMID CORNERS
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Oklahoma Mesonet station near Vinita measured 66 mph thunderstorm wind gusts.

Thunderstorm Wind in PUSHMATAHA, OKLAHOMA
From 20-MAY-13 20:00:00 to 20-MAY-13 20:00:00 (CST-6)
Location: CLAYTON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Several trees at Clayton State Park were damaged by strong thunderstorm winds.

Thunderstorm Wind in OTTAWA, OKLAHOMA
From 20-MAY-13 17:30:00 to 20-MAY-13 17:30:00 (CST-6)
Location: FAIRLAND
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Strong thunderstorm wind blew in west-facing garage doors, damaged privacy fences, and snapped large tree limbs along Highway 125.

Thunderstorm Wind in PUSHMATAHA, OKLAHOMA
From 20-MAY-13 18:55:00 to 20-MAY-13 18:55:00 (CST-6)
Location: TUSKAHOMA
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Oklahoma Mesonet station near Clayton measured 66 mph thunderstorm wind gusts.

Tornado in ADAIR, OKLAHOMA
From 20-MAY-13 17:35:00 to 20-MAY-13 17:37:00 (CST-6)
Location: CHRISTIE
Tornado F-scale: EF1
Property damage: 15.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

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.

Hail in MUSKOGEE, OKLAHOMA
From 20-MAY-13 16:52:00 to 20-MAY-13 16:52:00 (CST-6)
Location: WAINWRIGHT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Tornado in OSAGE, OKLAHOMA
From 20-MAY-13 14:51:00 to 20-MAY-13 15:01:00 (CST-6)
Location: AVANT
Tornado F-scale: EF1
Property damage: 5.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is the first segment of a two segment tornado. In Osage County, the tornado snapped or uprooted a number of hardwood trees. Large tree limbs were snapped, one of which fell onto the roof of a home. Based on this damage, estimated maximum wind in the tornado was 100 to 110 mph. It was photographed by a number of storm spotters and storm chasers. This tornado continued into Washington County, Oklahoma.

Tornado in LE FLORE, OKLAHOMA
From 20-MAY-13 19:33:00 to 20-MAY-13 19:34:00 (CST-6)
Location: MILTON
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado damaged trees. Maximum estimated wind in the tornado based on this damage was 70 to 80 mph.

High Wind in PITTSBURG, OKLAHOMA
From 20-MAY-13 20:00:00 to 20-MAY-13 20:15:00 (CST-6)
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A heat burst resulted in 65 mph wind gusts.

High Wind in MCINTOSH, OKLAHOMA
From 20-MAY-13 20:10:00 to 20-MAY-13 20:25:00 (CST-6)
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Eufaula mesonet station measured 65 mph wind gusts from a heat burst.

Tornado in WASHINGTON, OKLAHOMA
From 20-MAY-13 15:33:00 to 20-MAY-13 15:34:00 (CST-6)
Location: RAMONA
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

This is the first segment of a two segment tornado. Several storm spotters and storm chasers photographed this tornado. An NWS damage survey team could find no damage in the Washington County segment as it remained over open country during this portion of its life cycle.

Tornado in WASHINGTON, OKLAHOMA
From 20-MAY-13 15:01:00 to 20-MAY-13 15:05:00 (CST-6)
Location: VERA
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is the second and final segment of this tornado. In Washington County, the tornado snapped or uprooted numerous trees. Based on this damage, maximum estimated wind in the tornado was 100 to 110 mph. Numerous storm spotters and storm chasers photographed this tornado.

Tornado in ADAIR, OKLAHOMA
From 20-MAY-13 17:32:00 to 20-MAY-13 17:34:00 (CST-6)
Location: PROCTOR
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

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.

Tornado in LE FLORE, OKLAHOMA
From 20-MAY-13 19:44:00 to 20-MAY-13 19:55:00 (CST-6)
Location: NEFF
Tornado F-scale: EF1
Property damage: 5.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado damaged the roof of a home, uprooted several trees, and snapped a number of large tree limbs. Based on this damage, maximum estimated wind in the tornado was 90 to 100 mph.

Tornado in OTTAWA, OKLAHOMA
From 20-MAY-13 17:32:00 to 20-MAY-13 17:41:00 (CST-6)
Location: WYANDOTTE
Tornado F-scale: EF1
Property damage: 150.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is the first segment of a two segment tornado. In Ottawa County, Oklahoma, this tornado damaged several houses, damaged barns and outbuildings, and snapped or uprooted a number of trees. Based on this damage, maximum estimated wind in the tornado was 100 to 110 mph. The tornado moved in an easterly direction for much of its life cycle but turned more to the northeast as it approached the state line. It continued into Newton County, Missouri, and dissipated on the south side of the town of Seneca.

Tornado in WASHINGTON, OKLAHOMA
From 20-MAY-13 15:21:00 to 20-MAY-13 15:30:00 (CST-6)
Location: RAMONA
Tornado F-scale: EF1
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado damaged the roofs of two homes and damaged the siding of another. It also snapped or uprooted several hardwood trees. Based on this damage, maximum estimated wind in the tornado was 95 to 105 mph. Multiple storm spotters and storm chasers photographed this tornado.

Tornado in OTTAWA, OKLAHOMA
From 20-MAY-13 17:25:00 to 20-MAY-13 17:40:00 (CST-6)
Location: OTTAWA
Tornado F-scale: EF2
Property damage: 1.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado snapped or uprooted numerous trees and damaged numerous homes. It moved east-northeast for several miles but turned more easterly after crossing the Neosho River. The most significant damage occurred as the tornado crossed Highway 137, where a metal building and several homes were severely damaged. Many hardwood trees were also snapped above the ground in that area. Based on this damage, maximum estimated wind in the tornado was 115 to 125 mph.

Hail in PAWNEE, OKLAHOMA
From 20-MAY-13 14:15:00 to 20-MAY-13 14:15:00 (CST-6)
Location: CLEVELAND
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Post Office