Approximate Time: 5:00 p.m. CST - Team TWISTEX observes this classic tornado-producing system developing over north-central South Dakota. Along with the growing wall cloud, a tell-tale laminar tail cloud is also forming. Within minutes, the chasers' all-day pursuit of a massive supercell will pay off when the system starts dropping tornadoes.
Image Credit: Team TWISTEX Matt Grzych
Approximate Time: 5:19 to 5:20 p.m. CST - After several small twisters flicker in and out, a new large area of low level rotation (mesocyclone) develops several miles west-southwest of Bowdle, South Dakota. The TWISTEX Team races to intercept as a strong stovepipe tornado touches down and starts churning up a debris cloud. By this time, the tornado is on an east-northeast track that will cross Highway 12 so Tim and his crew race to deploy the new Tower probe in its projected path.
Image Credit: Team TWISTEX Matt Grzych
Approximate Time: 5:24 p.m. CST - Less than a minute after the TWISTEX Team deployed the Tower probe alongside Highway 12, the steadily expanding tornado engulfs the probe now barely visible in the debris cloud. Also faint, but visible, is the red smoke emitted by one of the probe's wind research tools. Once Tim, Carl and Matt realized they had an excellent chance for a Tower probe intercept, they successfully deployed the instrument in about 25 seconds and quickly pulled back to observe.
Image Credit: Team TWISTEX Carl Young
Approximate Time: 5:24 p.m. CST - In the few moments before the rapidly moving tornado forces them to retreat again, Tim celebrates the stunning success of the Tower probe intercept. After weeks of near-misses and setbacks across Tornado Alley, Team TWISTEX scores its major victory of the 2010 season. According to the official government report, the Bowdle tornado had likely reached EF2 strength by the time it was crossing Highway 12.
Image Credit: Team TWISTEX Matt Grzych
Approximate Time: 5:24 p.m. CST - While the TWISTEX Team is fully occupied with their probe intercept, cameramen/producers Sean Stack and Andres Vasquez are capturing all the action but within seconds the oncoming tornado will force them to make the call: keep shooting or run for it! Within seconds, the choice is made for them.
Image Credit: Team TWISTEX Matt Grzych
Approximate Time: 5:25 p.m. CST - With the tornado's swirling debris cloud closing in, the film crew decides it's time to flee. The three TWISTEX team members also race to get out although they can barely close the vehicle doors. In fact, Carl remembers that when he opened the doors to get in, jackets and other loose clothing shot out horizontally towards the center of the rapidly intensifying tornado.
Image Credit: Team TWISTEX Carl Young
Approximate Time: 5:32 to 5:33 p.m. CST - As the tornado continues on its northeasterly track, Team TWISTEX heads east on Highway 12 to parallel the steadily intensifying twister. The chasers had already recovered the Tower probe and we're hoping for another chance to intercept. The tornado started producing EF4 damage around 7:29 p.m. and will soon rip through several farms and a stretch of metal power transmission towers.
Image Credit: Team TWISTEX Carl Young
Approximate Time: 5:35 to 5:40 p.m. CST - By now a full-strength, barrel-shaped EF4, the Bowdle tornado moves northeast across farmland to ultimately intersect Highway 47. Visible in the distance on the right horizon are transmission towers that are about to be torn apart. To keep within range of the tornado, Team TWISTEX raced to Bowdle on Highway 12 and then headed north on Highway 47. As the tornado crossed this road ahead of the chasers, it toppled a state radio tower but then lifted shortly thereafter.
Image Credit: Team TWISTEX Matt Grzych
Aftermath - One of the half dozen power transmission towers felled by the tornado lies crumbled next to its concrete footings. These structures were brought down by winds estimated at between 165 and 200 miles per hour.The same supercell system that spawned the Bowdle tornado also produced eight other smaller tornadoes that together knocked down nearly a hundred power poles in the area.
Image Credit: Team TWISTEX Matt Grzych
Aftermath - Among the other victims of the tornado was this vehicle that was carried over 75 yards and dropped in a tree shelter belt that extended across a farm north of Bowdle. Trees that weren't uprooted by direct hits were stripped bare of their full spring foliage.
Image Credit: Team TWISTEX Matt Grzych
Aftermath - A piece of sheet metal torn from a farm building and driven into a tree like an axe blade is a stark reminder of why chasers fear flying debris above all other threats. The Various types of sheet metal, common on farms and other rural settings, are easily shredded into fragments that have been nicknamed "tornado shrapnel."
Image Credit: Team TWISTEX Matt Grzych
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