EF4 Chickasha tornado, Oklahoma, May 24, 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 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 mphthis tornado

   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

EF4

Date

May 24, 2011

Touchdown

5:06 PM CDT (22:06 UTC)

Lifted

6:02 PM CDT (23:02 UTC)

On the ground

56 minutes

Path length

33.3 miles (53.6 km)

Path width

880 yards (805 m)

Deaths

1

Injuries

48

Counties

Grady, McClain and Cleveland counties

Touchdown point

35.008, -97.961

Lift-off point

35.311, -97.571

Record number

1105241606-01

486 damage points were recorded along this path by NWS OUN, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF4. The highest wind the damage implies is 200 mph.

• rt of cntrline path , home with 8,ft bolts
• home completely destroyed. trees around home twisted in all directions.
• suburban down hill from the house several hundred feet completely destroyed.
• 4 cars tossed from shed w of home to ravone downwind,m hpome jas 3+p in rock and masonaruy walls with bolts on foundation.

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

A tornado outbreak occurred over parts of northern and central Oklahoma during the day on the 24th, with violent tornadoes devastating several communities. By the end of the day, one EF-5, two EF-4, and two EF-3 tornadoes destroyed buildings, ripped up trees and power poles, and unfortunately, resulted in 11 deaths. The day began with a strong upper level trough ejecting out of the southwest United States. The trough took on a negative tilt as it approached the southern Plains. A strong jet stream was located at both the middle and upper levels rotating around the upper trough. At the surface, a low pressure strengthened rapidly over northwest Oklahoma, keeping the low-level flow of warm, moist air to flow east of a dry line that had moved into western Oklahoma. Thunderstorms developed by early afternoon over western Oklahoma, and quickly became supercellular as they moved northeast. Strong low-level rotation developed early, with the first tornado occurring over Blaine county, and moved northeast into Major county. Another supercell rapidly gained low-level rotation as it moved from Caddo into Canadian County. This tornado became the strongest of them all as it moved north of El Reno, west of Piedmont, and to south of Guthrie in Logan county. Nine people died as a result of this tornado. Two more powerful supercells developed over Grady county, and they moved northeast into McClain and Cleveland counties. Finally, the final tornado occurred east of Norman into Pottawatomie county. The timing of this outbreak could not have come at a worse time, as rush hour was just unfolding as the tornadoes neared the Oklahoma City metro area.

This tornado is labeled C1 (Segment #1 of the Chickasha-Blanchard-Newcastle tornado). The tornado formed on the south side of Chickasha, quickly doing EF-2 damage. Mobile homes were damaged and destroyed, trees were uprooted/destroyed, outbuildings were destroyed, and many buildings lost significant portions of their roofs. One fatality occurred as a mobile home was destroyed in the south portion of Chickasha. As the tornado moved northeast of Chickasha, it gained significant strength, with several areas receiving EF-4 damage. Well-built homes were destroyed. Trees were debarked with only stumps remaining. Cars were thrown hundreds of feet. Almost continuous EF-3/occasional EF-4 damage occurred northeast until it crossed into McClain county 1.5 miles south of Highway 9. The tornado was probably at its strongest as it neared/crossed the McClain county line. Wind speeds there were estimated near 200 mph. Monetary damage estimates were not available.

This tornado is labeled D1 (Segment #1 of the Washington-Goldsby tornado). This tornado developed west of Bradley, downing tree limbs as it moved northeast. The tornado began to increase in intensity, producing EF-3 damage, as it approached McClain county. Although the damage was confined to trees, the severity of the damage became more intense. Trees were snapped at the bases, or debarked altogether. The tornado was several hundred yards wide as it neared the county line. Luckily, very few structures were in the path. This tornado continued into McClain County. Monetary damage estimates were not available.

This tornado is labeled D1 (Segment #2 of the Washington-Goldsby tornado). Widespread tree damage and ground scouring was ongoing as the tornado crossed into McClain county. As the tornado crossed Highway 76, even more intense damage occurred. EF-4 damage was surveyed at several locations. Several homes were reduced to a pile of rubble, or were wiped clean off of their foundations. Automobiles were mangled and almost unrecognizable. The tornado weakened and narrowed as it crossed CR 410. Even though the tornado had weakened, EF-2 to EF-3 damage was still occurring as it approached Highway 39. The tornado increased in intensity once again near the Highway, with EF-4 damage surveyed for the 2nd time. Well constructed homes were destroyed, with several wiped clean off of their foundations. This also began a longer streak of higher end damage, with EF-3 to EF-4 damage occurring until it crossed Highway 74B, west of High Avenue. Equally devastating destruction occurred over the areas of EF-4 damage. The tornado lifted west of Goldsby with still EF-3 damage occurring prior to lifting. It should be noted that this tornado had estimated winds up to 200 mph at times, falling just short of the damage indicator for an EF-5 tornado. Monetary damage estimates were not available.

This tornado is labeled C1 (Segment #2 of the Chickasha-Blanchard-Newcastle tornado). Significant damage continued as the violent tornado moved over the McClain county border. This may have been the strongest portion of this tornado, with wind speeds near 200 mph. Well-built homes were destroyed, with some cleaned off of their foundation. A concrete dome home was severely damage, mainly by the flying debris. Trees were debarked or destroyed. Very little was left standing for the first few miles into McClain county. Fairly consistent EF-3, with brief periods of EF-4 damage occurred as the tornado neared/crossed Highway 9, near the Highway 76 junction. The tornado began to weaken as it moved toward the Cleveland county border, with mainly trees and power poles/lines snapped. The tornado continued into Cleveland County. Monetary damage estimates were not available.

The deaths

1 direct deaths are recorded for this tornado, each with what Storm Data knows of it.

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

24 minutes of warning. NWS OUN issued a tornado warning for this county at 21:42 UTC, 24 minutes before the tornado touched down, in force until 22:45 UTC.

The county was under a tornado watch, issued at 17:47 UTC and running to 02:25 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 High Risk, with a 0.45 chance of a tornado within 25 miles, in the hatched area where significant tornadoes were expected. The outlook in force was issued at 20:44 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.

Chickasha Municipal Airport (CHK), 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), 48 km away, was scanning. The volume nearest the touchdown began at 22:05 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

47 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.