A spell of terrible weather makes good box-office

Its stars are rampaging wind funnels that toss cows and tractors in their wake - and it's spawning floods of imitators.

"Are you all right?" gutsy heroine Helen Hunt asks her co-star, Bill Paxton, in the closing scene of Twister. A monster tornado has just chased them round an Oklahoma farm hamlet, ripped one building after another from over their heads, and left them unscathed, fully clothed and game for that final smooch.

"We did it," she says. This pair of macho meteorologists, chasing one whirler after another round middle America in their battered truck, have finally unleashed a precious bucketful of golfball-sized sensors in the middle of the biggest of the lot. "Yes, we did," he responds meaningfully.

Plot, characters and dialogue leave everything to be desired in Twister. Although it is produced by Stephen Spielberg, directed by Jan De Bont, fresh from his breakneck hit Speed, and written by the author of Jurassic Park, Michael Crichton, by most measures it is a memorably bad film. But with a huge publicity push from multi-media conglomerate Time Warner, including a cover story on tornadoes in this week's Time magazine, Twister has been a sensation in the US. It took a record $40m (pounds 26.5m) on its opening weekend in more than 2,000 cinemas; rival studio executives consequently have dollar signs in their eyes, and weather on the brain.

The leading ladies in Twister are the ominous grey funnels created by computer graphics wizards. They throw a petrol tanker, a fleet of tractors and, most amusingly, a herd of plump cows at our heroes. Only three people are seen killed by tornadoes, none of them bloodily, which may reflect a new prudishness about violence. But the film got a "parental guidance" rating for "intense depiction of very bad weather" that could frighten young children.

Its success is spawning a flood of imitations. Storm Warning, The Flood and Firestorm are among those already in production or close to it. Two made-for-TV movies, Tornado and Night of the Twisters, have already drawn big audiences. "Any hurricane film that was floundering is now on the front burner," says one producer.

Hollywood has not just gone weather-mad. Twister may mark a turning point, industry observers say, from "man with a gun" action films where male stars triumph over evil towards "event", or disaster, films last popular in the 1970s, like The Towering Inferno. One Titanic movie is in the works, and a tunnel collapse film, Daylights, is making its way to the screen. But the US, like Britain, has had its share of freak weather lately, with Hurricane Andrew in 1991, Hurricane Bob in 1992, a paralysing blizzard in 1993, a deadly heatwave last year and another record storm this winter.

"There's a lot of people out there with a closet interest in the weather that we are tapping into with these movies, people who have not spoken about it," says Stu Ostro, a senior meteorologist with the Weather Channel. It reaches 50 million homes by cable with a mix of forecasts and dramatic footage, and rivals CNN in viewer figures. All of Twister's tornadoes were computer creations. But the surge in home video cameras has brought some of the most dramatic real-life footage ever seen, including a sequence from a Texas man who was struck by lightning but kept filming the tornado demolishing his house.

A University of Iowa psychologist in a recent survey examined 80 "weather phobics", people who suffer so strong a fear of thunderstorms and tornadoes that even the mildest forecast can leave them trapped in their homes, too scared to shop or work. Symptoms include constantly watching the Weather Channel. But special showings of Twister both in Iowa, where it was largely filmed, and Oklahoma, where it is set, have drawn huge audiences. Real life scientific storm-chasers have been sceptical, if impressed by the special effects. "There were some serious meteorological implausibilities," says Mr Ostro. "When they would have at least been gored to smithereens, they emerged with hardly a scratch."

There are more than a few sly references in Twister to The Wizard of Oz, with glimpses of old Judy Garland films and a little girl's dog named Toby. The love rival, jettisoned like just another flying cow, has more than a passing resemblance to the Wicked Witch of the West. And indeed, for all of the film's $85m cost, much of it on the use of massively powerful computers that in the final scene put the actors right in the eye of the storm, one ends up longing for the charming naivete of Dorothy. Even though her tornado was constructed in 1939 with a broom, some dust and a piece of spinning nylon, it was somehow more persuasive.