The most prolific tornado outbreak tore grass out of the ground
April 27, 2011, was one of the worst days in recorded weather history
The twister’s winds grew so strong that it scoured asphalt and grass right out of the ground.
Packing estimated winds as high as 330 km/h, the scale-topping EF-5 tornado killed three people as it tore through central Mississippi, leaving catastrophic damage in its wake.
The storm that devastated Philadelphia, Mississippi, on April 27, 2011, was one of more than 300 tornadoes that touched down during what would become the most prolific tornado outbreak ever recorded.
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All the ingredients for a historic tornado outbreak
Canada’s largest tornado outbreak on record unfolded on August 20, 2009, when a total of 19 confirmed tornadoes touched down across portions of southern Ontario. The country has only ever seen one twister rated an F5—that storm hit the town of Elie, Manitoba, back in 2007.
Compared with Canada's largest outbreak, it's tough to imagine hundreds of tornadoes dotting the landscape in under 100 hours, much less four scale-topping twisters in a single day.
That's the reality millions of people faced during the largest tornado outbreak ever recorded, which took place across four days between April 25-28, 2011. Meteorologists remember that outbreak as a ‘generational’ event for its prolific nature and its intensity.
Only a tiny fraction of severe thunderstorms ever produce a tornado. It’s even rarer for a weather event to produce dozens—let alone hundreds—of tornadoes in such quick succession.
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A slow-moving low-pressure system developed over the U.S. Plains on Monday, April 25, 2011, giving rise to multiple rounds of tornadic thunderstorms throughout the region on Monday and the following Tuesday.
But it was Wednesday, April 27, that raised alarms among even the calmest experts. Humid winds surging inland off the Gulf of Mexico sharply contrasted with upper-level winds soaring over the Deep South. This wind shear, combined with explosive thunderstorm energy, gave rise to a cavalcade of intense supercell thunderstorms.
April 27, 2011, holds the record for most tornadoes in one day
The Deep South actually faced a one-two punch of terrible storms on April 27. A line of severe thunderstorms swept through the region during the pre-dawn hours that Wednesday.
This early morning severe weather episode produced extensive wind and tornado damage that knocked out power to much of the region—a noteworthy event on its own that was almost forgotten given what would happen later that afternoon.
Instability quickly grew with the heat of the day, and thunderstorms began to flourish across Mississippi and Alabama by noontime. The first major storm of the day ripped through the heart of Cullman, Alabama, producing EF-4 damage as estimated winds as high as 275 km/h swept buildings clean off their foundations.
Dozens of supercell thunderstorms would eventually develop and continue straight into the overnight hours. All told, more than 200 tornadoes would touch down in a 24-hour period, making for the most tornadoes ever recorded in a single day.
Ground scoured, vehicles tossed
One particularly long-tracked and devastating tornado hit the major cities of Tuscaloosa and Birmingham, Alabama, killing more than 70 people. Officially, 324 people died as a direct result of the four-day tornado outbreak—making it the deadliest on record in the modern era.
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Four of the tornadoes on April 27 left behind scale-topping EF-5 damage, including the one that struck Philadelphia, Mississippi.
Meteorologists who surveyed the damage there noted that “the ground was scoured out to a depth of two feet [0.6 m] in places, and asphalt was scoured off pavement” across areas that experienced the tornado’s 330+ km/h winds.
An EF-5 twister that struck Smithville, Mississippi, lofted and hurled an SUV nearly a kilometre until it smacked into the town’s water tower and left a car-sized dent in the side of the tank.
By the time the low-pressure system finally moved along on Thursday, April 28, tornado damage had been reported from Texas to New York.
Even though the worst of the twisters remained deep in the heart of the U.S., at least one tornado touched down in Fergus, Ontario, accenting the sheer extent of this generational tornado outbreak across eastern North America.