Professor Kevin Knupp, left, and student Todd Murphy visit Hackleburg, Ala., in their Mobile Meteorological Measurement Vehicle. Getting to such sites before tornado damage is cleaned up is crucial to their research.

Professor Kevin Knupp, left, and student Todd Murphy visit Hackleburg, Ala., in their Mobile Meteorological Measurement Vehicle. Getting to such sites before tornado damage is cleaned up is crucial to their research. (Dave Dieter / For the Times / June 16, 2011)

HACKLEBURG, ALA. -- The Mobile Meteorological Measurement Vehicle -- a worn-looking '90s-model Dodge Intrepid with classic rock on the radio, a tower of weather gauges attached to its roof and a laptop computer bolted to its dash -- crested a rolling hill on its way to tiny Hackleburg, Ala.

"There it is," said Kevin Knupp, a University of Alabama-Huntsville atmospheric sciences professor, tapping the window.

To the left, a swath of pine and oak leaned northeast, like a curve of toppled dominoes, while to the right, far off, trees lurched the other way -- all pushed over by the counterclockwise swirl of a huge tornado.

In the passenger seat, graduate student Todd Murphy took notes on the GPS-enabled laptop. They had found what they were looking for: the path of one of the killer storms that battered northern Alabama on April 27.

Just six weeks earlier, the South had been hit by one of the most severe tornado outbreaks in U.S. history. In Alabama alone, an estimated 69 twisters killed about 240 people. Tuscaloosa and Birmingham were hit hard. Hackleburg, population 1,430, was leveled -- plowed over by a mile-wide tornado that originated near the Mississippi-Alabama state line and traveled a 132-mile path before it reached Tennessee and petered out. Eighteen people in Hackleburg died.

Knupp is in the field to assess the storm damage before it is all cleared away and to talk to witnesses while their memories are still crisp.

Over the next year or so, backed by funding from the National Science Foundation, he and his team will study what they've observed from the fallen trees and wreckage -- as well as radar records, satellite images, survivor interviews and even YouTube videos posted by people who captured the freak weather and its aftermath. Less "Storm Chasers" than "CSI: Meteorology," the team hopes its data-gathering will deepen understanding of how the storms developed, improve tornado forecasts and save lives.

Knupp's team also believes that the unprecedented windfall of data spun off a single day of devastation could put several weather theories to the test.

Murphy wants to see how ripples in the air called ducted gravity waves help spawn tornadoes. Elise and Chris Schultz, a husband-and-wife grad student team, plan to test how well an experimental radar system can track the path of a tornado's "debris ball" -- all the dust and trees and bits of houses the twister gathers up -- something that is not possible with most radar used today.

If things pan out, the data may even give Knupp and postdoctoral researcher Tim Coleman a chance to test a controversial idea they've mulled over for years: that features on the ground like trees, hills and valleys influence the way tornadoes behave.

Knupp -- trim and mild-mannered -- grew up in twister country, on his family's Iowa farm, where they grew corn and soybeans and raised hogs. He wrote his first scholarly paper about tornadoes in 1976 while he was an undergraduate at Iowa State University.

As a teen, he once convinced his father to stop the car on the way home from band practice so he could watch a funnel cloud approach. The family was soon engulfed in 60 mph winds; Knupp thinks they were run over by a weak tornado. No one was hurt.

He briefly attempted to drive out and "surf" the April 27 storms too, but the extreme weather convinced him to turn his car around.

"I got close, and it looked pretty wicked," he said.

That day, instability in the atmosphere -- warm, humid air near the ground and cooler, drier air aloft -- accompanied strong wind shear. The combination is favorable for creating super-cell thunderstorms. Super cells can generate tornadoes.

In a typical significant tornado outbreak, the energy helicity index, which incorporates instability and wind shear, might register 3 or 4. In some parts of Alabama in the hours preceding the April 27 outbreak, it hit 11 -- "about as large as you'd ever seen," Knupp said.

From his home in Huntsville, Knupp directed students to set up the university's mobile radar system, which can detect rain, hail and debris in clouds. The students hustled the truck-mounted device to an open location nearby and stayed with it until 8:30 p.m., riding out the storm. For about three hours during the late afternoon, MAX, as it's called, was the only radar in the region that wasn't knocked out by the weather.

Tracking the incoming images on his computer, Knupp saw storm after storm after storm. By lunchtime, two distinct weather systems had already spawned more than 30 tornadoes in the state, reportedly killing five and knocking out power to more than a quarter-million households and businesses.

Then, in the afternoon, came the mega-tornadoes, including the twister that plowed through Hackleburg. The National Weather Service would eventually determine there had been 19 tornadoes in Alabama rating EF3 or higher on the Enhanced Fujita Scale, which goes from EF0 (a small twister, like the one Knupp saw after band practice) to EF5 (a devastating one, like Hackleburg's). Sirens blared all day.

"A good data set," Knupp mused.