By Lori EhdeThe tornado that hit eastern Rock County Sunday was assigned an F1 rating — the weakest on a scale of F1 to F5 — by the National Weather Service.But what it lacked in strength it made up for in character, according to Greg Harmon, meteorologist in charge of the National Weather Service in Sioux Falls."This was, from our view, a pretty unusual event," said Harmon, who hasn’t seen a tornado like this one in 30 years with the National Weather Service.He said conditions involved in producing Sunday’s tornado are more typical of what is seen in the western high plains, like eastern Colorado."For high-based thunderstorms to produce this tornado like they did for our area is pretty unusual," Harmon said. "The bottom of the thunderclouds were much higher than usual — about 8,000 feet. It’s usually at 3,000 or 4,000 feet where we get our tornado weather."As a result, he said, the tornado was much taller and more visible to so many people from such a great distance.Photogenic twisterFreshly tilled fields and dry conditions provided plenty of loose material that also gave the twister remarkable visibility.A typical tornado in the Midwest occurs with thunderstorms that produce rain, but with no moisture, Sunday’s otherwise weak system was able to sustain itself longer in an already arid environment."It had free access to all the ingredients it needed to keep going," said Todd Heitkamp, warning coordination meteorologist with the National Weather Service.Several residents near the storm supplied local media with quality digital images of the funnel cloud.Leah Van Meeteren, for example, watched the twister form near her farm eight miles northeast of Luverne."I was looking up into the clouds, and I could see a hole in the middle that looked like it was right above our place," she said. "As it moved to the northeast, it started picking up dirt. … It was really cool to watch."Started east of Luverne, ended near LismoreHeitkamp and Harmon spent Tuesday morning tracking the path of the twister with Rock County Emergency Management Coordinator Kyle Oldre.Based on reports, the funnel cloud formed just northeast of the Blue Mounds State Park shortly after 8 p.m. and traveled about 10 miles per hour to the east. It was last sighted near Lismore where it dissipated about 8:25 p.m.The F1 rating was determined by the amount and extent of damage it caused. In this case, wind speeds likely reached about 100 miles per hour.The only report of structural damage Sunday came from the Brad Scott farm southwest of Kenneth. His home received minor damage, with some shingles removed and some windows and gutters broken. But a less sturdy storage shed and silos were destroyed.Steel from the silos was scattered for about a mile off of Scott’s homestead. Inside the large storage barn, a grain truck lifted up and landed on lumber stored inside. "I saw that some debris was blowing around and it was an accelerating wind," he said. Once downstairs, though, he said he didn’t hear much commotion, and wasn’t concerned about finding damage. When he left the basement, however, he saw the tornado leaving his property to the east. "It wasn’t the usual funnel; it just looked like a big swirling circle of dirt. It didn’t even sound like much was happening."Because the twister was so weak, it didn’t cut a clear path on the ground, so its direction was established based on reports by residents and weather spotters.Little warningThe unusual start to Sunday’s funnel cloud caught weather forecasters off guard."This tornado didn’t form in the typical way tornados are formed," Heitkamp said. "Did they issue the warning after the fact? Yes. But that was only because we were gathering reports and trying to determine where it was going."Oldre said residents should have been aware of stormy weather and alert to the possibility of a tornado, since TV and radio broadcasts had issued thunderstorm watches and warnings three hours prior.As emergency management coordinator, Oldre said he witnessed troubling behavior among residents when the Luverne sirens sounded."Everyone was out in the streets looking around," he said. "When the sirens go off, it means seek shelter immediately. … Stay inside when you are inside. The reason is, you don’t know what’s going on behind you when you’re looking off to the east."Worse yet, Oldre said he heard reports of residents driving to get close to the storm for photos or driving from their homes to outrun the tornado.He said the worst possible place to be during a tornado is in a vehicle.On the other hand, he said some residents in their homes were concerned that they didn’t hear the sirens over the usual indoor sounds of televisions and appliances."They’re outdoor sirens. … It is not intended to be heard by people inside," Oldre clarified. "They were intended to be outdoor warning signals to residents who may not have heard weather warnings on TV or radio."Heitkamp and Harmon encouraged residents to brush up on their tornado drills, because there may be more systems like Sunday’s this summer."As long as it stays dry like it is, we’re likely to see these weak, brief tornados with other squalls of thunderstorms," Harmon said.