The El Reno tornado, which occurred on May 31, 2013, stands as a historically significant and exceptionally powerful weather event. This atmospheric phenomenon developed over rural areas of Central Oklahoma, gaining notoriety for its unusual characteristics and unprecedented scale. It emerged as part of a larger system that spawned multiple tornadoes. Its immense proportions and dynamic behavior prompted extensive research into its formation and progression. This tornado became a landmark event, reshaping understanding of severe weather.
Defining Tornado Size
Meteorologists employ several metrics to define a tornado’s size and intensity. One primary measurement is the maximum width, which indicates the broadest extent of the tornadic circulation. This is typically determined through ground surveys of damage paths or by using mobile Doppler radar systems that map the wind fields within the storm. Measuring width can be challenging if the tornado’s movement is erratic or if it is obscured by rain.
Another aspect of a tornado’s physical dimension is its track length, detailing the total distance it travels across the ground. This measurement quantifies the area impacted by the storm. Beyond physical dimensions, intensity is assessed using the Enhanced Fujita (EF) Scale, which rates tornadoes based on the damage they inflict on structures and vegetation. This scale correlates observed damage with estimated wind speeds, ranging from EF0 (weakest) to EF5 (strongest).
While the EF Scale primarily reflects a tornado’s intensity through its destructive potential, physical measurements of width and track length contribute to understanding its overall scale. A wider tornado, even if not rated EF5, can affect a much larger area, increasing the potential for widespread damage. Both physical size and estimated wind speeds from damage surveys are considered when describing a tornado’s overall magnitude.
The El Reno Tornado’s Unprecedented Scale
The El Reno tornado of May 31, 2013, set a new benchmark for tornado size, particularly in its maximum recorded width. As it crossed U.S. Highway 81, the tornado expanded to an unprecedented 2.6 miles (4.2 km) wide, making it the widest tornado ever recorded. This immense width significantly surpassed previous records, including the 2004 Hallam tornado, which peaked at 2.5 miles wide. The tornado’s rapid growth occurred within about 15 minutes of its formation.
Beyond its record-breaking width, the El Reno tornado also exhibited some of the highest wind speeds ever measured. Mobile Doppler radar units, specifically the RaXPol radar from the University of Oklahoma, detected extreme winds within its vortex. These measurements indicated wind speeds exceeding 295 mph (476 km/h), with some reports suggesting up to 302 mph (486 km/h).
These radar-estimated wind speeds are among the highest observed on Earth, second only to the 1999 Bridge Creek-Moore tornado. While the official damage survey rated the El Reno tornado as an EF3 due to the sparse structures in its path, radar data revealed a much more powerful circulation. The tornado’s path length was 16.2 miles (26.1 km), and it remained on the ground for approximately 40 minutes. This combination of record-setting width, extreme wind speeds, and substantial track length highlighted its exceptional scale compared to typical tornadoes, which are often much narrower and shorter-lived.
Unique Meteorological Features
The El Reno tornado’s massive size and unpredictable behavior were influenced by several unique meteorological characteristics. One significant feature was its “rain-wrapped” nature, meaning the tornado circulation was often obscured by heavy rainfall, making it difficult to see. This characteristic posed a challenge for visual confirmation and tracking by storm spotters and chasers. The rain-wrapping effect meant the visible funnel cloud did not accurately represent the true, much larger extent of the tornadic winds.
The tornado also featured multiple, rapidly rotating sub-vortices within its larger circulation. These smaller, intense whirls moved independently and erratically around the main tornado, creating highly localized areas of extreme wind speeds. The presence of these sub-vortices made the tornado’s movement and behavior erratic and unpredictable. This dynamic internal structure was a key factor in the tornado’s impact.
The El Reno tornado’s movement was notably erratic, changing speed and direction multiple times. Initially moving east to southeast at 30-40 mph, it later made a sudden turn to the north, accelerating to 50 mph, before slowing down again to 10 mph before dissipating. Such shifts in direction and speed made forecasting its exact path difficult, increasing risk for anyone in its vicinity. These complex features distinguished the El Reno tornado, highlighting challenges in understanding and predicting powerful atmospheric vortices.