It was Friday night at a steakhouse in Oklahoma City. We'd just finished our dinners when the unmistakable sound of tornado sirens broke through the din of clanging silverware and country music.

Our waitress -- a blond teenager in a cowboy hat -- nervously pointed out that it was May 4; May 3 was the two-year anniversary of the half-mile-wide tornado that destroyed half of Oklahoma City and killed 46 people. That twister was classified as an F5 -- the biggest, baddest, blackest kind of windstorm on the planet.

We hurried to the van. The sky was green and black, and wind lashed the trees. But we weren't running from the tornado, we were running toward it.

Seven of us had paid $1,500 to spend five days on a hunt for foul weather. Our guide, Todd Thorn, spends two months each year driving tourists across Texas, Oklahoma, Kansas, Nebraska, the Dakotas, Iowa and Minnesota -- otherwise known as Tornado Alley. His company -- Storm Chasing Adventure Tours -- is one of about six in the country that cater to an odd subset of tourist: the extreme weather aficionado.

Seated in the radar-equipped van, we drove toward the place where the sky was darkest and greenest. Thorn turned on the weather radio, and it blared in a computer-generated voice: "ERRRRRRNT. ERRRRRRRRRNT. A TORNADO HAS BEEN SPOTTED 13 MILES SOUTH OF WILL ROGERS AIRPORT. TAKE COVER NOW. LEAVE YOUR MOBILE HOMES AND VEHICLES."

Thorn stopped the van on an entrance ramp to Interstate Hwy. 40 to consult the computer global positioning system and on-board radar. A couple of us nervously looked out the back window, hoping not to be killed by a semitrailer truck roaring onto the interstate.

We spent two hours cruising the suburbs near the airport in search of the twister, but we got caught on the wrong side of the storm (in the rainy, windy part), and it was too dark to see anything in any case.

We glumly returned to our beds in the Holiday Inn at 11 p.m.

Storm troopers

Our group was an interesting mix. There was Chris Le Conte, 33, an accountant from Guernsey -- a British Island off the coast of France. Sick of drizzle, he wanted to see real thunderstorms.

Deborah Grant, 49, who runs a flea market in Lubbock, Texas, said she had never been on a vacation before. Her reason for making this her first one: "I love nature, and I want to see a tornado."

Phyllis Frazier, 35, a nurse in Orlando, said, "It's been a dream. I have always wanted to see a tornado before I die." Someone opined that the first wish may connect her to the dying part.

The other three paying customers, including me, all shared a fascination with violent weather.

In the Midwest, we don't have giant mountain ranges or endless ocean views. But we have the sky, and in the summer, we have clouds that make the Himalayas seem anemic. I grew up watching the cumulus towers of giant storm cells grow to 60,000 feet. That's more than twice the size of Mount Everest.

When the tornado sirens sounded in my neighborhood, I stayed outside to watch the clouds swirl, to see that majesty and power in the sky. It took a lot of yelling to get me to join my family in the basement.

Our tour leader, on the other hand, has a full-blown obsession.

For years, Thorn, 35, spent his vacation each spring chasing tornadoes with friends. Four years ago, he decided to go professional and started Storm Chasing Adventure Tours. For two months each year, he takes leave from his job as an engineer for a satellite technology firm in Denver. He spends May and June driving as many as 30,000 miles in search of the worst storms the Great Plains can serve up.

Day 1

We gathered for the 10 a.m. departure from the Holiday Inn. It was cloudy.

That's good.

Thorn looked like a stereotypical weatherman, with neatly combed-over hair, a trim build and a crisp polo shirt. The Ford V-12 storm-chase van was festooned with radar dishes and antennas. Thorn explained what each one was. The big dome on the top was for picking up cable TV so we could watch the Weather Channel on three screens every minute we were in the van. And we did.

We watched the Weather Channel about 12 hours that day, over about 350 miles of territory, including vast, treeless areas of northern Texas. In the late evening light, we saw a funnel cloud west of Altus, Okla.

We made a big circle, ending up near our starting point at about 11 p.m. We spent the night at Super 8 in Yukon, Okla., just south of Oklahoma City.

Day 2

First thing in the morning, Deborah Grant, the Texas flea market owner, announced she was quitting the tour. One day of vacation was enough.

She said she got cramps in her legs from sitting so much on the first day, and that she couldn't imagine four more. Some of us shared that feeling.

"When's your flight out," I asked.

"I don't know and I don't care," she said with a broad smile.

After dropping her off, Thorn consulted his computer, the radar and a consultant at the National Storm Laboratory in Norman, Okla., and we headed back to Texas to look for twisters, accompanied by the steadying presence of the Weather Channel.

In late afternoon, the white puffy cotton balls in the sky began melding into ominous gray walls with immense towers rising above them. It was humid. Thorn -- a very laconic fellow -- noted that the dew point was 71. "Nice and juicy," he said.

When cool air from the Rockies meets that warm wet air from the Gulf, turbulence results. Giant hail and tornadoes sometimes follow.

Thorn consulted his banks of equipment and said some "super cells" appeared to be "firing up" north of us. Supercells are the mega-storms that spawn tornadoes.

An hour later at 4 p.m., we drove under a glowering sky.

Thorn turned the weather radio on. The computer voice blared its warning. A tornado had been sighted about 10 miles north of our position on I-35.

Thorn sped up to 90 miles per hour. "Of course, now we hit a traffic jam," he said. The van was hemmed in by semitrailer trucks.

"Tornado, tornado!" he shouted. "There it is, on the left!"

Dangling from a black wall cloud on the horizon was an ominous dark triangle. In a minute it turned into a white, curling tube, and then it withdrew like a snake back up into the clouds.

One hour and about 40 miles later, we spotted another one, from about 10 miles distance, just outside Ringling, Okla., near the Texas border.

We were on a country road this time, and Thorn stopped the van so we could get out and study the beast.

Standing in a row by a barbed wire fence, we looked across a pasture toward a tower of cumulus clouds that rose tens of thousands of feet over the prairie. Hanging from it like a small arm, the tornado looked harmless, and it was too far away to allow us to hear its roar. But it was ripping up somebody's farm fields just the same.

Day 3

We didn't see any tornadoes. We drove another 500 miles and got in a lot of Weather Channel viewing. We saw more big, mean looking clouds, endless expanses of mesquite trees. I saw one jack rabbit. We had dinner at the Cracker Barrel in Waco, Texas.

We also had a memorable encounter at a gas station in Italy, Texas.

The rail-thin, elderly attendant, with a crumpled, grimy Texaco cap on his head, saw the Storm Chasing Adventure Tour logo on the van (and all the radar dishes) and he accosted Phyllis the nurse as she entered the station to go to the bathroom.

"You is crazy, you should be home with your husband instead of out chasin' tornadoes!"

"I don't have a husband," Phyllis said flatly.

"Well, you should be out lookin' for one insteada out chasin' tornadoes. I'm gettin' off work and I'm gonna go home and talk to my wife. I ain't gonna be out chasin' tornadoes!"

Day 4

No tornadoes or big thunderstorms. I sat in the front of the van so I could talk to Thorn. The forecast called for partly sunny skies.

As a replacement for severe weather, we were going to Carlsbad Caverns in New Mexico to see the dusk flight of 1 million Mexican free-tail bats, a virtual tornado of skin wings flapping into the desert sky.

"Two years ago there were tornado warnings all the way to Carlsbad Caverns," Thorn said. "We were on the interstate when golf-ball-size hail started."

He says "golf-ball-size hail" the same way a jeweler might mention a particularly well-faceted diamond.

"Two Weather Service vans passed us going into the storm. We drove to the first underpass and parked. The vans kept on going. Later we passed them and all their windows, even on the sides, were broken out." He laughed remembering their hubris.

When we got to Carlsbad, it turned out we were too early in the season for the Mexican free-tail bats. Most of them were still in Mexico.

As the sun set over the mesa that holds Carlsbad Caverns, we saw only a few thousand of them flitting off to hunt mosquitoes.

After dark, six of our party stayed on top of the mesa and watched a distant thunderstorm batter the Chihuahuan Desert with hundreds of blue and white thunderbolts. The stars winked overhead. The full moon rose red as blood in the east.

Day 5

Morning came. Blue skies stretched as far as the eye could see.

We started driving back to Oklahoma City. In the afternoon, we ate at the Big Texan Steak Ranch, "Home of the Free 72 Ounce Steak," in Amarillo.

At 7:55 p.m., 2,008 miles after we left and about 70 miles before we got to where we were going, the Weather Channel reported that a tornado was rampaging through Burnsville, Minn.

"You should have stayed home," said fellow storm trooper Jeffrey Nelson. "Saved some trouble."

-- Chris Welsch is at cwelsch@startribune.com .