The El Reno, Oklahoma, tornado of May 31, 2013, reached a maximum width of roughly 2.6 miles (about 4.3 kilometers), making it the widest tornado ever recorded in the United States. Mobile Doppler radar measured winds near 300 miles per hour inside the vortex, yet the storm was officially rated only EF3 on the Enhanced Fujita scale. That gap between what instruments detected and what the official rating reflects tells a story that reshaped how meteorologists, storm chasers, and emergency managers think about large tornadoes.
Putting 2.6 Miles in Perspective
Most tornadoes are far smaller. A typical tornado’s damage path might span a few hundred yards. Even violent tornadoes rated EF4 or EF5 rarely exceed a mile in width. El Reno’s footprint was wide enough to swallow a mid-size city. At its peak, the funnel stretched across an area larger than many downtowns, and anyone standing at one edge of the tornado would not have been able to see the other side even on a clear day. Published analyses describe the tornado’s diameter at approximately 4.3 kilometers, with peak winds estimated around 135 meters per second.1American Meteorological Society. Crowdsourcing the El Reno 2013 Tornado: A New Approach for Collation and Display of Storm Chaser Imagery for Scientific Applications Converting those figures, the width comes to about 2.6 miles and the winds to roughly 302 miles per hour.
That width record matters beyond bragging rights. A tornado this broad behaves differently from a narrow one. The visible funnel may not correspond to where the worst winds are. The tornado’s center can shift unpredictably, and smaller satellite vortices embedded within the larger circulation can sweep across areas that appear to be safely outside the main funnel. People who thought they were watching the storm from a safe distance found themselves inside it.
Why an EF3 Rating Understates What Actually Happened
The Enhanced Fujita scale rates tornadoes based on the worst damage they produce to structures, vegetation, and other indicators. El Reno carved most of its path across open farmland west of Oklahoma City, where there simply were not many buildings to destroy. The structures it did hit sustained damage consistent with EF3 winds, roughly 136 to 165 miles per hour. So the official rating landed at EF3.
But mobile radar units deployed by research teams that day told a different story. Their instruments detected wind speeds far above the EF3 threshold, with the highest values approaching or exceeding what would merit an EF5 rating under the scale’s framework. The roughly 135 m/s figure measured by radar corresponds to over 300 mph, well into the theoretical EF5 range.1American Meteorological Society. Crowdsourcing the El Reno 2013 Tornado: A New Approach for Collation and Display of Storm Chaser Imagery for Scientific Applications The disconnect highlights a limitation of damage-based rating systems: a tornado in a cornfield with 300 mph winds will always be “rated” lower than one that hits a suburb with 170 mph winds, because there is nothing to damage. El Reno is the clearest example of a tornado whose true intensity far outstripped its official rating.
This was not a new problem. Meteorologists had long understood that EF ratings depend on what the tornado hits, not on the tornado itself. But El Reno sharpened the debate about whether radar-measured winds should play a formal role in tornado ratings. As of now, they still do not. The Enhanced Fujita scale remains a damage survey tool, meaning that every tornado that churns across open ground will carry an asterisk for anyone who knows the full story.
Subvortices Inside the Giant
El Reno was not a single column of spinning air. It was a massive circulation housing at least two dozen identifiable smaller vortices that formed, orbited, and dissipated within the larger funnel. Rapid-scan radar documented these subvortices over a span of about 132 seconds, with some moving at translational speeds exceeding 75 meters per second, or roughly 170 miles per hour.2SHAREOK. Rapid-scan, polarimetric, mobile, Doppler-radar observations of the formation, evolution, and structure of the El Reno tornado of 31 May 2013
Those numbers are staggering when you unpack them. A subvortex racing along at 170 mph inside a parent tornado that itself is moving across the ground means localized wind speeds at the overlap point can be far higher than either circulation alone. This is where the radar-measured winds near 300 mph came from: the combination of the parent tornado’s rotation, the subvortex’s own spin, and the translational motion of the subvortex around the broader circulation. In a narrow tornado, what you see is largely what you get. In a massive multi-vortex tornado, the most extreme winds can be concentrated in small, rapidly moving pockets that are almost impossible to predict or even detect visually.
For storm chasers on the ground that day, the subvortices were lethal. The tornado killed eight people, including veteran storm researcher Tim Samaras, his son Paul Samaras, and colleague Carl Young. Their vehicle was found over half a mile from the road. Other chasers survived only by making split-second decisions to change direction. The subvortices moved so quickly and unpredictably that traditional chasing strategies, which rely on identifying the tornado’s track and staying to its south or southeast, broke down entirely. A subvortex could swing outward from the parent tornado’s visible edge and reach a position that had looked safe seconds earlier.
How Researchers Measured a Tornado This Large
No single instrument captured El Reno’s full scope. The picture came together from multiple data streams. Mobile X-band polarimetric radar units, driven into position by research teams from several universities, provided the wind speed and structural data. These rapid-scan systems can complete a full sweep in seconds rather than the minutes required by fixed National Weather Service radars, making them far better at resolving fast-changing features like subvortices.3Monthly Weather Review. Photogrammetric Analysis of the 2013 El Reno Tornado Combined with Mobile X-Band Polarimetric Radar Data
Photogrammetry filled in what radar could not see. Dozens of storm chasers and local residents recorded video of the tornado from multiple angles. By calibrating the timing of these videos (researchers used lightning flashes visible in multiple recordings to synchronize them) and then geolocating the camera positions, scientists could reconstruct the tornado’s visual width, shape, and structure at specific moments. This “crowdsourced” photogrammetric approach was somewhat novel for tornado research and yielded a remarkably detailed visual timeline of the storm’s evolution.1American Meteorological Society. Crowdsourcing the El Reno 2013 Tornado: A New Approach for Collation and Display of Storm Chaser Imagery for Scientific Applications
Together, these datasets produced something unusual in tornado science: a comprehensive portrait of an extreme tornado’s internal structure, external appearance, and wind field all at the same time. Most tornadoes are either well-observed by radar or well-documented on video, rarely both in such detail. El Reno became one of the most studied tornadoes in history precisely because so many instruments and cameras happened to be pointed at it.
The Atmospheric Setup
El Reno did not appear out of nowhere. The supercell that produced it formed near the intersection of a cold front and a dryline, which is a boundary separating moist Gulf air from dry desert air common across the southern Plains. The atmosphere that day featured moderately strong vertical wind shear and high instability, creating the kind of environment that can sustain rotating thunderstorms for hours.4Weather and Forecasting. A Multiscale Overview of the El Reno, Oklahoma, Tornadic Supercell of 31 May 2013 The storm developed at the southern end of a line of multicell convective storms, giving it room to ingest moisture-laden air without competing with neighboring cells.
What made this setup particularly dangerous was its timing and location. The El Reno tornado struck just eleven days after the devastating EF5 tornado that hit Moore, Oklahoma, on May 20, 2013, killing 24 people. The Oklahoma City metropolitan area was on edge. When tornado warnings were issued on May 31, residents who remembered Moore’s destruction were primed to act, and many of them tried to flee by car.
The Evacuation That Nearly Turned Catastrophic
As the El Reno tornado developed and moved generally east-northeast toward the western fringes of the Oklahoma City metro, something unusual happened: a large-scale vehicular evacuation. Tens of thousands of people got in their cars and tried to drive south or east away from the storm’s projected path. Interstates and highways quickly became gridlocked. Research on this evacuation found that the resulting traffic jams could have caused casualties in the hundreds if the tornado had not weakened and dissipated before reaching the densely packed roadways.5Weather, Climate, and Society. A Spatiotemporal Perspective on the 31 May 2013 Tornado Evacuation in the Oklahoma City Metropolitan Area
The near-miss forced a difficult public conversation. For years, some local television meteorologists had encouraged viewers to get in their cars and drive away from approaching tornadoes, advice that works when roads are clear and the storm’s path is predictable. El Reno demonstrated how that advice scales catastrophically in a metropolitan area. When everyone flees at once, nobody can move. Vehicles caught in gridlock are among the worst places to be during a tornado: they offer almost no protection from debris and can themselves become projectiles. After the event, the National Weather Service and many broadcast meteorologists shifted their messaging to emphasize sheltering in place in a sturdy structure rather than attempting to outrun a tornado in a car.
The evacuation crisis also underscored the unique danger of wide tornadoes. A narrow tornado might cross a highway in seconds, affecting a small stretch of road. A 2.6-mile-wide tornado covers a swath that can encompass multiple highway interchanges simultaneously. Drivers who thought they were heading to safety by taking a different exit could still have been in the damage path. The width of El Reno meant there was no quick lateral escape for vehicles caught in its vicinity.
A Tornado and a Flood at the Same Time
The May 31 event was not just a tornado. The same storm system produced extreme rainfall and flash flooding across the Oklahoma City area. This combination of a tornado and a flash flood occurring simultaneously, sometimes called a TORFF event, creates a communication nightmare for emergency managers and broadcast meteorologists. Research into how these compound hazards are communicated found that television coverage struggled to address both threats at once, with stations differing in how they balanced tornado warnings against flood warnings during the El Reno event.6Journal of Operational Meteorology. A Tale of Two Hazards: Studying Broadcast Meteorologist Communication of Simultaneous Tornado and Flash Flood (TORFF) Events
For people on the ground, the dual hazard compounded the danger. Motorists fleeing the tornado encountered flooded roadways. Some of the fatalities that evening were flood-related rather than tornado-related. The flash flooding also hampered search-and-rescue operations in the tornado’s aftermath. Compound weather events like this one are increasingly studied because they require the public to process and act on multiple, sometimes conflicting, sets of emergency instructions at the same time. The El Reno event became a case study in how easily public messaging can be overwhelmed when nature throws more than one threat at a community simultaneously.
What El Reno Changed for Storm Chasers
The deaths of Tim Samaras and his team marked a turning point in the storm-chasing community. Samaras was not a thrill-seeker; he was a highly respected engineer and researcher whose instrument deployments had contributed real data to tornado science. If a veteran with his experience and caution could be killed, the message was clear: traditional chasing heuristics did not account for a tornado this large and erratic.
Before El Reno, many chasers operated on the assumption that a tornado’s path was broadly predictable based on the parent storm’s motion, and that staying a mile or two to the south provided a safe buffer. El Reno’s rapid changes in direction, its extreme width, and the outward-sweeping subvortices invalidated those assumptions. In the years since, chaser safety discussions have placed much greater emphasis on maintaining larger standoff distances, having multiple escape routes, and recognizing that a wide, rain-wrapped tornado may not be visible until it is too late to maneuver.
The event also intensified debate about road congestion caused by recreational chasers. On May 31, 2013, hundreds of chase vehicles crowded the rural highways west of Oklahoma City. When the tornado shifted direction, some of those chasers found themselves trapped by a combination of the storm’s movement and bumper-to-bumper traffic on narrow two-lane roads. While no formal regulations on storm chasing resulted, several counties and the state of Oklahoma explored credentialing systems and road-closure protocols in the following years. The tension between the scientific value of field observations and the safety risks of crowded roads during tornado events remains unresolved.
Rain-Wrapped and Hard to See
One of the most treacherous features of the El Reno tornado was its visibility, or lack thereof. For much of its life, the tornado was partially or fully wrapped in rain, making it difficult to see from the ground. A narrow tornado on dry ground is usually visible as a distinct funnel, giving chasers and residents at least some visual reference. El Reno’s enormous width combined with the heavy precipitation from its parent supercell meant that the boundary between “inside the tornado” and “in heavy rain nearby” was not always obvious.
This matters because people make life-or-death decisions based on what they can see. Motorists on Interstate 40 that evening reported driving into what they thought was simply heavy rain, only to experience extreme winds and debris. Some storm chasers who had been tracking the tornado visually lost sight of it when rain curtains shifted, then discovered the tornado had changed direction and was closer than expected. Radar was the only reliable tool for tracking the tornado’s position in real time, and most people on the road did not have access to real-time radar in 2013 the way they might today through smartphone apps.
The rain-wrapped nature of El Reno also complicated the post-event damage survey. National Weather Service teams who walked the damage path had to distinguish between tornado damage and straight-line wind damage from the broader storm, a process that is harder when the tornado is embedded within an area of generally severe weather rather than standing out as an isolated funnel on an open plain. This ambiguity is another reason the official EF3 rating may underrepresent what the tornado was capable of in its most intense moments.