El Reno Tornado Rated EF3, Widest on Record

A Record-Breaking Tornado

Although the National Weather Service in Norman, Okla. rated the tornado an EF5 on June 4, 2013 based on wind measurements from mobile Doppler radar, it was re-evaluated by NOAA in late-August 2013. Despite the radar-measured wind speeds, the tornado has officially been rated an EF3 since damage higher than this intensity was not found by the survey team.

NOAA says that while wind measurements from mobile radar are considered reliable, the current policy for determining the EF rating of a tornado is based on surveys of the damage. NOAA is exploring whether this policy should change in the future to allow the use of experimental radar data for rating tornadoes.

To find out how tornadoes are rated based on the damage they produce, click here to read about the Enhanced Fujita Scale.

The width of the tornado has been given a "conservative" estimate of 2.6 miles. This is a new official record for the widest U.S. tornado, beating the previous record of 2.5 miles near Hallam, Neb. on May 22, 2004.

(However, research conducted by Joshua Wurman of the Center for Severe Weather Research suggests that similar radar-based measurement techniques would have justified a tornado width in excess of 4 miles for a tornado that struck Mulhall, Okla., on May 3, 1999. The official width of that tornado is listed as one mile, based on observed damage.)

The El Reno tornado is the same one that killed three storm chasers and injured the crew of our own Tornado Hunt team.

"This Was An Incredible Storm"

In a web conference discussing the tornado, Rick Smith, warning coordination meteorologist at the National Weather Service in Norman, Okla., noted that this tornado was exceptional in many ways.

The massive tornado contained several powerful "subvortices," areas of extremely rapid rotation that swirled within the larger tornadic circulation. These subvortices contained the strongest wind speeds measured by radar within the tornado, greater than 295 miles per hour in several different instances.

Not only did these subvortices contain almost unfathomable winds, but they were moving forward at incredible speeds, making them impossible to outrun.

"Think of the average size of an Oklahoma tornado you'd see on a typical afternoon - three or four of those things moving along the ground at a speed of 170 to 180 miles per hour, crossing each other with all kinds of violent motions going on," Smith remarked. "So this is going to be studied for a long time."

Smith later noted that a few of these vortices may have been moving along the ground at a jaw-dropping forward speed of 185 miles per hour, even as the parent tornado lumbered along at a forward speed of about 24 miles per hour.

"This was an incredible storm," Smith said. "The storm that produced this tornado was doing some phenomenal things."

"It Would Have Been Catastrophic"

Smith noted that the extreme winds associated with the subvortices affected a relatively small area compared to the tornado as a whole. None of the subvortices hit any structures, which is why mobile radar data from the University of Oklahoma were needed to assess the true strength of tornado; based on damage alone, survey crews could only find visual evidence of EF3 winds.

"They were relatively small -- some were very very small," Smith said of the intense subvortices. "It's quite possible that in a subdivision where you have big big lots that these could have passed between houses."

However, Smith noted that if any structures had been struck by this portion of the tornado, the result would have been "complete devastation."

Acknowledging the tragic toll on storm chasers and motorists caught in the erratic path of the tornado, Smith said, "The impacts were horrible ... but we were fortunate that this did not hit a densely populated area. I don't want to imagine ... but it would have been catastrophic."

Researchers Killed -- Stroke of Bad Luck?

The NWS report indicated that the two most intense subvortices with the highest wind speeds occurred "north and east of the intersection of 10th and Radio Road," approximately 3 miles south-southeast of downtown El Reno.

This location corresponds very closely to the last known location of Tim and Paul Samaras and Carl Young, the storm chasers and researchers who died while actively pursuing the tornado.

Smith did not address questions about "storm chaser issues" in the conference, except to note that "a two-and-a-half-mile-wide tornado would not look like a tornado." As to whether any of the violent vortices within the tornado would have been visible, he added, "I could not begin to speculate."

On the next page, we go back to the events leading up to the El Reno tornado and step you through the evolution of this monster storm as it happened.

Thunderstorms Explode

Let's step through the minute-by-minute timeline of this event near El Reno.  All times below are CDT.

3:30 p.m.:  A "PDS" tornado watch is issued by the Storm Prediction Center for much of central and eastern Oklahoma.  PDS means "particularly dangerous situation", reserved for only those rare situations when long-track, violent tornadoes are possible.

5:36 p.m.:  First tornado warning issued for Canadian County, including El Reno.

5:56 p.m.:  Spotters confirm a tornado seven miles south of Calumet.  Lead time of initial warning before first tornado report:  19-20 minutes.

6:06 p.m.:  Large, multi-vortex tornado confirmed near El Reno.

Next, the massive tornadic supercell rolled into Oklahoma City.

Oklahoma City Chaos

In a word, it was "chaos".  A tornadic supercell moving into a large metro area during Friday evening rush.  Let's resume the minute-by-minute account.

6:56 p.m.:  Tornado EMERGENCY posted by the National Weather Service (NWS) office in Norman, Okla. for Will Rogers World Airport, Downtown Oklahoma City and north Moore.

7:05 p.m.:  Wind gusts to 70 mph would last for 16 minutes at Will Rogers World Airport.  

7:07 p.m.:  Reports of power flashes near I-40 and Meridian Avenue on Oklahoma City's west side.  

7:10 p.m.:  Local media chopper cams show jammed traffic on Interstate 35 in Oklahoma City.  NWS-Norman tweets out this urgent plea:

7:38 p.m.:  Tornado reported in the observation at Tinker Air Force Base on Oklahoma City's southeast side.  Thirty-six minutes later, a gust to 87 mph would be measured, there.

An NWS-Norman survey the following day found EF1 damage along the 10.4 mile path in southwest Oklahoma City, including a track across Will Rogers Airport.  A separate EF0 tornado was found on the north side of Moore, not far from the Moore Medical Center, destroyed in the May 20 EF5 tornado.

Then, the concern turned to flooding rain!

8:00 p.m.:  Reports of pedestrian tunnels flooding in downtown Oklahoma City.

9:00 p.m.:  Numerous water rescues of motorists in flooded vehicles in the city.

Will Rogers Airport measured a storm total of 6.76" of rain in roughly 12 hours Friday evening into Saturday morning.  This rain not only shattered a May rainfall record, but added to a staggering turnaround in precipitation in 2013, compared to a drought-plagued 2012.

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