1.2 Million Warned to Leave New Orleans NEW ORLEANS - More than 1.2 million people in metropolitan New Orleans were warned to get out as 140-mph Hurricane Ivan churned toward the Gulf Coast, threatening to submerge this below-sea-level city in what could be the most disastrous storm to hit in nearly 40 years.    Residents streamed inland in bumper-to-bumper traffic in an agonizingly slow exodus Tuesday amid dire warnings that Ivan could overwhelm New Orleans with up to 20 feet of filthy, chemical-polluted water...