Ivan, the third and most dreaded hurricane to taunt Florida in a month, shifted west on Saturday, giving hope to the battered Gulf Coast and the fast-emptying Keys, but placing the Panhandle on high alert.

The gigantic storm, almost as broad as the enormous Frances and as strong as Charley, appeared to be headed into a meteorological vise. A high-pressure zone over the Atlantic pushed it west, while high pressure over Texas competed to push it east. On Saturday, the Atlantic's high-pressure zone was winning.

Forecasters are steadily easing their projections of the hurricane's track, into the Gulf of Mexico, away from the retirement towns south of Sarasota that Charley shattered, and away from the flood-prone, heavily populated Tampa Bay region. Most forecasts now predict that the storm will make landfall late Tuesday or early Wednesday on the Florida Panhandle, between Tallahassee and Pensacola, though some meteorologists believe it could slide westward to southern Alabama.

But memories of Charley, which pounded Florida with 145-mph wind gusts on Aug. 13, are vivid, reminding residents about the uncertainties of even the best forecasting models. Charley had been forecast to land on Tampa but made a sudden turn and blasted onshore more than 100 miles to the south, killing 27 people and causing $7 billion in damage. It was followed three weeks later by Frances, a storm so freshly departed that more than 700,000 people -- most of them on the east coast, north of Palm Beach -- are still without power because of its winds.

"Sometimes I wish that these things wouldn't all happen in our state all at once, but if there was a place that could rebound from this, it's Florida," Gov. Jeb Bush (R) told reporters.

Storm anxiety reached almost unheard of levels. Even Key West, a city of jaunty individualists who love to sneer at hurricanes, was turning into a ghost town. Half of the residents of the nation's southernmost city had fled by late Saturday. Many worked their way north to Miami on the skinny, mostly two-lane road on the 120-mile island chain.

At Florida International University, in suburban Miami, three floors of an administration building were transformed into a shelter for Keys residents. The strange prospect of famously casual Keys dwellers sleeping in offices normally occupied by university executives was an object of curiosity for people leaving a nearby exhibit of Haitian sculpture.

"Let's go look at the refugees!" one woman exclaimed as she bounded up the stairs.

Those who stayed in Key West were uncharacteristically low-key.

Just two locals nursed their beers at Irish Kevin's on Saturday afternoon.

"The only thing we need now is tumbleweeds," said Chris Eyler, 23, who was working behind a bar lined with empty stools.

People here shrugged off the one-two punch of Charley and Frances, in the words of one resident, as "just a lot of wind." But not this time. As Hurricane Ivan smashed through Grenada and Jamaica and headed for the Cayman Islands and Cuba, killing at least 45 people, Key West and the other islands north of it disgorged thousands of cars filled with tourists and longtime residents. About 1,300 cars an hour were recorded on Friday along northbound U.S. 1.

The exodus left Rudy Valdez, 58, virtually by himself on Duval Street. Valdez, the property manager of a boarding house, said that, in his nine years living in Key West, he has not evacuated for a hurricane and that he was not going to start now.

"The chances of it hitting are slim to me," he said.

Forecasters were beginning to agree with him late Saturday. As the storm's projected path nudged west, meteorologists were sounding more confident about the prospects for the Keys but were still wary that Ivan's great width could put part of the island chain in the dangerous northeast quadrant of the hurricane, which generally causes the most damage.

Emergency managers in Monroe County, which includes the Keys and a small wedge of the southern Florida mainland, said there was little they could do to force people out of their homes after they issued an evacuation order on Thursday.

"We can't put a gun to their head and force them to leave," said Greg Artman, a spokesman for Monroe County's emergency management services.

But the estimated 50 percent evacuation rate signaled that weeks of watching other hurricanes devastate huge swaths of Florida was having an effect on the stubborn populace of Key West.

For this easygoing beach community, "that's high," city spokesman Michael Haskins said. "People are taking this serious."

Certainly there was much to fear. Ivan was not only wide and powerful, but it was showing low-pressure readings at its core below those of Hurricane Andrew, the huge 1992 hurricane that set the standard for modern-day destruction in South Florida. Ivan's winds were clocked at 165 mph on Saturday afternoon as the storm plowed toward Cuba. The storm had also slowed considerably, moving at just 9 mph, a dangerous trend because slow-moving hurricanes have time to drop more rain as they pass and to cause flooding.

Some in Key West looked to a higher power for guidance. Fanchon Brooks, 42, planned to leave as soon as her grandparents were evacuated. As she swept her porch, she fretted about her church friends who refused to go.

"They're depending on their faith," she said. "I do, too. I just know I'm not supposed to test Him."

Down the street, the iron gate was locked at the Spanish Colonial house where Ernest Hemingway once lived. The only sign of life was one of the house's famous cats, leaning into a fountain for a drink.

Roig-Franzia reported from Miami Beach.

A customer walks toward the side door of a boarded-up Marathon, Fla., cafe as Hurricane Ivan moves closer. More residents than usual have left the Keys.With Ivan near, Mike Bradshaw of Montreal packs his van near Islamorada as he prepares to leave the Florida Keys after a three-week vacation.