EF2 tornado, Lake Carl Blackwell Dam to Stillwater, 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 mphthis tornado

   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

EF2

Date

May 24, 2011

Touchdown

5:50 PM CDT (22:50 UTC)

Lifted

6:05 PM CDT (23:05 UTC)

On the ground

15 minutes

Path length

10.4 miles (16.7 km)

Path width

880 yards (805 m)

Deaths

0

Injuries

18

County

Payne County

Touchdown point

36.034, -97.163

Lift-off point

36.108, -97.013

Record number

1105241650-01

71 damage points were recorded along this path by NWS OUN, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF2. The highest wind the damage implies is 132 mph.

• Closer look at the foundaton of the house.
• Tree twisted to the ground.
• Photos look west towards main road...looking at the back of the structure.
• Snapped telephone pole located nearby.

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 was labeled B4 (Stillwater tornado). This tornado developed with mainly tree and power pole/line damage. The tree damage was significant, with several homes impacted as the tornado traveled northeast. Significant roof and siding damage occurred to the homes, with several barns and outbuildings sustaining significant damage or were destroyed altogether. EF-2 damage continued as the tornado moved south of Stillwater, with additional structures sustaining roof damage. A couple of the homes also had collapsed chimneys. The damage lessened in severity over the latter half of the tornado path, with mostly tree damage and minor structural damage. 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 22:33 UTC, 17 minutes before the tornado touched down, in force until 23:30 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.

The Norman radar (KTLX), 84 km away, was scanning. The volume nearest the touchdown began at 22:48 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.