Moments before a massive tornado would wreak havoc on their community, destroying hundreds of homes and killing nine residents, almost no one in the small town of Parkersburg, Iowa, had any idea what was about to hit them.
But with conditions that seemed just right for a tornado, storm-spotters like Ben McMillan were out surveying the Iowa countryside. During tornado season, storm spotters are often deployed to monitor bad weather as it rolls in.
McMillan is a member of Central Iowa Skywarn, a volunteer organization that partners with the National Weather Service (NWS) to track storm conditions and issue tornado warnings around the state.
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On the afternoon of May 25, 2008 -- the Sunday of Memorial Day weekend -- McMillan was on a storm-spotting mission near Parkersburg when a dangerous mix of meteorological forces began to coalesce just outside the town of 1,900 residents.
"[The National Weather Service] issued a tornado watch called a PDS tornado watch, or a 'particularly dangerous situation," McMillan said. "When you see the words PDS or hear the words 'particularly dangerous situation,' watch out, because that's something that's pretty rare."
Initially, the storm spotters honed in on area to the west of the town. "One of our initial targets was the city of Ackley, which is just to the west … and we had a large storm cloud go up right over the city of Ackley. And, at that point, we felt that that was going to be a potential candidate to become a very violent storm," he told ABC News' Sam Champion.
"I just seem to have a knack for being places when stuff happens," McMillan said. "I've seen a lot of major tornados over the past 10 years."
Click here to watch McMillan's video of the tornado brewing.
"The earth was releasing so much built-up pressure in this case, that it just -- formed more rapidly than a storm I'd ever seen before. Most tornadoes, it's a process -- this was on steroids. It was so violent, so quickly it went from nothing to the most violent tornado on earth. This was like an atom bomb going off," he said.
Not only was the pace of the storm unlike anything McMillan had ever seen, so was its appearance. "The storm wasn't your classic tornado; it wasn't a little ropey thing that came down," he said. "This was just a massive black cloud of death."
Meanwhile, Chief Deputy Tim Wolthoff of neighboring Grundy County was also on duty that day, patrolling the area for storms with his 20-year-old son.
Here in "Tornado Alley," storm spotting is just another part of the job. "We're out there to protect and to serve and that's part of our job is to go out there and, you know, protect the community if at all possible," Wolthoff said.
Wolthoff was sent to track storms in the northern part of Grundy County, south of Parkersburg. "As we got further north, then you could see that it was starting to get pretty dark," he said.
Minutes later, Wolthoff heard reports over the radio that the tornado had stuck ground and, almost instantly, he saw the storm with his own eyes.