The first wave of hurricane hunter planes penetrated and circled Hurricane Frances on Sunday as scientists employed every tool at their disposal to learn more about an intense storm that seems likely to eventually strike the East Coast -- somewhere.

Once again, forecasters and emergency managers advised residents of South Florida and the rest of the Atlantic coast to carefully monitor the powerful hurricane, take preliminary precautions now and get ready to elevate their preparations later this week.

''We could have the threat of a significant hurricane in five days here,'' said forecaster James Franklin of the National Hurricane Center in West Miami-Dade County. ``Right now, I think we'll see some kind of impact on the East Coast.''

SATURDAY LANDFALL?

Traveling slowly, Frances was not expected to reach the mainland until Saturday at the earliest, though that could change.

Meanwhile, Tropical Storm Gaston weakened after making landfall Sunday in South Carolina, and forecasters tracked newly formed Tropical Storm Hermine, which formed Sunday evening between Bermuda and the East Coast but posed no immediate threat to land.

Though the dangerous core of Frances is expected to miss the Caribbean islands, its outlying weather could touch that region today or Tuesday and forecasters issued warnings and watches for the northern U.S. Virgin Islands, Culebra and Vieques in Puerto Rico, and other nearby islands.

That proximity to land also brought Frances within range of hurricane hunter aircraft, a development eagerly awaited by forecasters because real-time data gathered by those crews always add a degree of precision to computerized forecast models. Until now, forecasters had to rely on satellite imagery and ship reports.

Some scientists flew into Frances' eye, taking measurements that helped determine that the hurricane weakened slightly, though it remained a Category 3 storm. Others flew surveillance missions around the storm, collecting information about the surrounding environment that can help forecasters improve their track forecasts. By this morning, all of that data will be incorporated into forecasts, and that could change the picture -- for better or worse.

''With each day that passes, you get a little more clarity,'' said Franklin, a veteran of many hurricane hunter missions. ``Hopefully, this information will bring the models into line.''

HIGH PRESSURE SYSTEM

Hurricane forecasters have access to more than a dozen models developed by scientists at universities, the Navy and elsewhere. Each computer program analyzes different sets of data, then projects the path and intensity of a storm.

Through much of Sunday, the computerized models diverged into two groups: One brought Frances into South Florida; the other, which began to gain dominance, turned it more northwest, suggesting a run at northeast Florida, Georgia or the Carolinas.

The deciding factor will be the strength of a high pressure system that sits north of the hurricane. If that system remains strong, it would nudge Frances toward South Florida; if it weakens, it could allow Frances to turn a little northward.

''There are a couple of different scenarios that could play out, and we can't really call it yet,'' Franklin said.

One way or the other, forecasters said, some spot along the East Coast seemed likely to endure a direct hit.

Residents and emergency managers throughout a state still stunned by Hurricane Charley confronted the dawning reality this morning that Florida is likely to be ravaged by its second natural disaster in three weeks.

Though still far away, a ferocious Hurricane Frances -- a huge Category 4 storm with 140-mph winds -- rolled closer to the East Coast. Warnings and watches covered the southern and central Bahamas, which will get hit today and Thursday. South Florida could be under an official alert by Thursday morning and could be swept by hurricane wind Friday.

This morning, all signs pointed to a direct strike at the Florida East Coast on Friday or Saturday, depending on how far north or south the core wobbles.

Emergency managers began making plans. Water managers lowered canals. The Florida National Guard prepared to redeploy some of the 400 troops now helping Southwest and Central Florida residents cope with the aftermath of Charley, which struck the Gulf Coast on Aug. 13.

''I don't want to say we've been there and done that, but . . . we're prepared to do it again,'' said Lt. Col. Ron Tittle of the Florida National Guard.

And South Floridians wisely elevated their level of concern and preparation, flocking to hardware stores and supermarkets even if Frances' intentions remained uncertain.

''You can't know,'' Andrea Knafo of Cooper City said as she shopped for emergency provisions. ``I have three children who need a roof over their head. Food, safety. I'm preparing for sure.''

The problem: Forecasters did not yet know with a high degree of certainly where Frances' powerful core would collide with the mainland. They said the point of attack could come anywhere between Key West and South Carolina, though the Florida coast seemed most likely.

''I don't see how this will not have an impact over a large section of the Florida peninsula,'' said Max Mayfield, director of the National Hurricane Center in West Miami-Dade.

Worse, forecasters suggested that the storm could be moving very slowly when it crosses the coast, prolonging the agony. And the calamity it brings could be sweeping.

Frances is mammoth, its hurricane winds stretching across 140 miles, equal to the distance from Miami to Vero Beach; its tropical storm-force winds extending 370 miles from end to end, greater than the distance from Homestead to Jacksonville.

''Frances will affect a very, very large area,'' Mayfield said Tuesday evening during a rare televised press conference that dramatized the danger. ``We are expecting it to make landfall as a major hurricane that certainly is capable of causing extreme damage and, if we're not careful, loss of life.''

The extended three-day forecast suggested that the core could make landfall near Fort Pierce. But forecasters repeatedly emphasized that those forecasts have large average margins of error -- and that left the entire state within Frances' potential sphere of destruction.

ANIMATED IMAGES

Again breaking with tradition, Mayfield shared with TV viewers animated images of two of the hurricane center's computerized forecast models. One sent the storm directly over South Florida; the other dispatched it to South Carolina.

At issue was the strength of a high pressure system north of the hurricane, blocking its passage and forcing it westward. If the high remains strong, South Florida could absorb a direct hit from Frances. If the system weakens, Frances might be able to curve away and menace Central or North Florida or points farther north.

''So everybody from Florida through the Carolinas needs to stay very, very vigilant at this time,'' Mayfield said.

In addition, Frances produced one of the forecasters' most dreaded scenarios: an extremely dangerous storm approaching the coast at an oblique angle, much like Charley did. That makes even short- and mid-range forecasts more difficult because a tiny variation in direction over the ocean can substantially change the angle of attack and thus the landfall point.

WATCH THE TREND

So Mayfield and other experts urged residents not to focus on -- or draw much fear or comfort from -- the thin center line of long-range forecasts. Instead, they said, monitor the entire cone of probability and watch the trend of the forecasts to see if the danger might be growing.

And get ready now.

''The odds that the worst of the storm will come right over you are always low,'' said Bryan Norcross, chief meteorologist for WFOR-CBS4 and one of the region's leading hurricane experts. ``But the consequences of not taking action ahead of time to protect your family and your property are huge.''

Many South Floridians took that to heart. Some were veterans of Andrew, which ravaged south Miami-Dade in 1992. Others saw the devastation wrought by Charley.

At a Home Depot on University Drive in Davie, customers hustled portable generators out the door so quickly they almost left skid marks. ''We got 30 of them in this morning,'' said assistant manager Danny Miranda. ``Forty-five minutes after we opened, they were gone.''

He said managers were summoning supplies from stores across the country because many Florida stores were depleted by Charley.

Circling the area, stacking rows of duct tape like bricks in their carts, customers spoke with relatives or friends on their cellphones, trying to figure out what was needed.

Among them was Michael Waldfogel, who said his home was destroyed by Andrew and he planned to help elderly neighbors board up their homes. ''I was born in Miami,'' Waldfogel said. ``I know the routine.''

Herald staff writers Tina Cummings, Phil Long and Nikki Waller contributed to this report.

Hurricane Frances slowed its forward progress as it approached Florida this morning, and the state's most ominous storm since Hurricane Andrew loomed just over the horizon.

More than 2.5 million people from South Florida to Daytona Beach were told to flee their homes, the largest evacuation in state history.

As the storm drew closer, it pummeled the Bahamas. In Nassau this morning, the sky was pitch black and tropical storm-force winds grew into hurricane-force winds greater than 74 mph. A few trees already were uprooted, while others swayed heavily in the hot, salted air.

Frances' leading edge of squalls should arrive in South Florida in a few hours, though its more prolonged rain and persistent rain might not arrive until late tonight. Its potentially catastrophic core seemed certain to strike Saturday night -- somewhere in Florida. The system could claw through the state until early Monday, prolonging the pain and intensifying the damage.

The storm weakened a bit over night, but it remained a very dangerous Category 3 hurricane with 120-mph winds.

The official forecast called for it to re-intensify to a Catetory 4 with 140-mph winds before landfall of the core, but forecasters characterized their intensity predictions as ''low confidence'' because the conditions controlling it for the next day or so were unusually complex.

In the end, a well-placed sense of foreboding blanketed Florida.

''I'm very scared,'' said Sylvia Alvaro, 56, of Kendall, whose husband was attaching plywood to their apartment's windows after dark Thursday. ``I went through Andrew. We thought we were going to die. All you can do is pray.''

Evacuation orders covered 260,000 residents of coastal areas in Miami-Dade County and 250,000 people in Broward County. Countless Floridians nailed, screwed in, rolled out shutters, transforming their homes into tin cans or plywood exhibits. Evacuees jammed many roads.

Officials pleaded with residents to respond calmly to the emergency, but to respond immediately. Time was running out -- and it will expire later today.

''This is going to be a very major, damaging, destructive event,'' said Craig Fugate, state director of emergency management. ``The best help and the first help are going to be your neighbors.''

Fort Lauderdale-Hollywood International Airport will close at 10 a.m. today. Miami International Airport is open but carefully monitoring wind conditions, and American Airlines, Delta Air Lines and other major carriers planned to suspend service later today. Port Everglades and the Port of Miami-Dade are closed.

''This is not what we had planned,'' said Lucy Auerbach, a British tourist whose Miami Beach vacation turned into a Miami Beach evacuation. ``This has really turned into a nightmare.''

''It's only going to get worse,'' said Randy Pfost, meteorologist in charge of the National Weather Service's South Florida office.

A prophetic indicator of trouble ahead: Workmen put up storm shutters Thursday at the National Hurricane Center in West Miami-Dade County.

SQUALLS COMING

Forecasters said the storm's outlying squalls -- just a sample of its destructive power -- could begin sweeping Miami-Dade and Broward counties around noon, followed by tropical storm-force winds, torrential downpours and, possibly, hurricane winds.

Frances' eye and the rare Category 4 winds of 145 mph that surround it could strike anywhere, though forecasters said the mostly likely -- though not certain -- spot was between Palm Beach and Vero Beach and the most likely time was around midday Saturday.

`SCARES EVERYBODY'

''This thing scares everybody,'' said Theresa Bibo, 60. ``On a scale of one to 10, I'm up to a seven.''

A resident of a mobile home park in Vero Beach, she was packing up clothes, medicine, important documents and precious photos. At the moment, Vero Beach was in Frances' cross-hairs.

Forecasters said the hurricane's ultimate effect on Miami-Dade and Broward depended on the storm's ultimate track, intensity and forward speed -- and all of that remained difficult to gauge.

The storm's eye wobbled a bit during the day and its power waned a bit at night, diminishing -- if that term could be used -- to a 125-mph Category 3 storm. Forecasters said they expected Frances to regain its Category 4 strength before it reaches the mainland.

With luck, South Florida will remain on the west side of the core, which usually is weaker -- though forecasters said that might not be the case this time. Regardless, the region seemed in store for many hours of wind and rain.

The details of what to expect in Miami-Dade and Broward, according to forecasters:

Up to eight inches of rain in an already saturated area. Substantial street flooding. A 24-hour battering by winds ranging from 39 to 74 mph that fell trees and damage some structures. Large-scale power outages.

And that was the best case scenario at the moment. The core still could shift much closer to Miami-Dade and Broward before landfall, forecasters said.

''We can't let South Florida off the hook yet,'' said hurricane specialist James Franklin.

Those with the misfortune of being near the main point of attack could endure 20 inches of rain, possible tornadoes, a storm surge of seven to 15 feet along the coast and devastating floods inland, forecasters said.

Especially vulnerable are communities along the Kissimmee River south of Orlando, where Hurricane Charley filled the river and connected lakes to the brim just three weeks ago.

Experts also worried about a huge coastal storm surge and the effect of the wind and rain on Lake Okeechobee, where the dike was expected to hold but some islands seemed certain to be submerged.

The storm was huge -- much larger than Hurricane Andrew, which ravaged South Miami-Dade in 1992. And it is slower moving, too.

The East Coast from Florida City in Miami-Dade to Flagler Beach, north of Daytona Beach, was covered by a hurricane warning. That means hurricane conditions are expected within 24 hours.

About 14.6 million of Florida's 17 million people live in the areas under hurricane watches and warnings.

A flood watch was in effect in Miami-Dade and Broward counties until 8 p.m. Sunday. An inland hurricane wind watch covered western Miami-Dade and Broward.

''People inland will get as much wind as the people on the beaches,'' said James Lushine, the National Weather Service's severe weather expert for South Florida.

As Frances drew near, Miami-Dade officials ordered the evacuation of all 260,000 people who live in Miami Beach or elsewhere along the coast and Biscayne Bay. Also included were residents of mobile homes and the 8 ½-Square Mile Area in the East Everglades.

''We want people to take the order very, very seriously,'' said Miami-Dade Mayor Alex Penelas.

Broward officials told 250,000 people to leave mobile homes and all structures along and near the beaches or in low-lying areas.

Officials emphasized that evacuees should seek shelter farther west in their own counties with relatives or friends rather than further congest overcrowded roads. To ease the pressure, tolls were suspended on virtually all toll roads.

Numerous public shelters opened in both counties -- and all along Florida's Atlantic coast.

''Let's hunker down and batten down the hatches,'' said Tony Carper, Broward County's director of emergency management.

Statewide, the evacuation was the largest in history, surpassing the 1.3 million people urged to leave when Hurricane Floyd threatened but missed the state in 1999.

And so, an atmosphere of crisis prevailed everywhere.

Gasoline and diesel fuel were in short supply and long lines formed at supermarkets. Automatic teller machines ran out of cash. Some evacuees encountered bumper-to-bumper traffic.

Along Florida's central East Coast, mobile home parks turned into ghost towns as residents lowered shutters and headed for shelter with friends in more substantial houses or left the area.

''Alabama, that's the closest reservation we could get,'' Sally Simmons, 69, said as she loaded ice and soft drinks into her mini-van.

WAITING FOR WOOD

Meanwhile, people lined up more than 300 deep at Vero Beach stores, waiting more than seven hours for plywood.

``I'm nervous, I'm scared,` said Faith Irizarry, 27, in line at a Home Depot in Fort Pierce. ``I'm afraid I will lose all the things I can't replace.''

Her plight and that of the entire state attracted attention at the highest levels.

''I have been preoccupied with this very, very large hurricane that is bearing down on Florida,'' Andrew Card, President Bush's chief of staff, said in New York, site of the Republican National Convention.

To minimize any delay in aiding victims, state and federal emergency officials announced an immediate merging of forces ''so that we will overwhelm the needs of the victims,'' Fugate said.

Said Bill Carwile, a coordinating officer for the Federal Emergency Management Agency: ``We want to have a massive response.''

Herald staff writers Ina Paiva Cordle, Wanda J. DeMarzo, Tere Figueras, Mary Ellen Klas, Phil Long, Curtis Morgan, David Ovalle, Charles Rabin and Nicole White contributed to this report.

Residents responded slowly to orders to evacuate Miami Beach, adjacent beach towns and the mainland shoreline Thursday, but anxious and unhappy tourists forced from shuttered hotels began filling some public shelters.

Police visited mobile home parks to urge residents to leave, while Miami-Dade Mayor Alex Penelas urged about 260,000 residents in evacuation zones to heed the warnings.

''You don't want to find yourself tomorrow with a rush to evacuate, that's the worst possible situation,'' Penelas said in a briefing.

The Red Cross opened six shelters.

North Miami Beach High had more than 500 people by early evening, many of them tourists. About 800 special needs residents out of a total of around 1,000 had already been evacuated.

At Drew Middle School, two German couples had been forced to trade fancy Miami Beach accommodations for a section of an already-smelly corridor. For two days, said Marc Kirschner, he and girlfriend Melanie Muller had argued over whether to head north to escape Frances.

''Why the heck didn't we?'' Muller asked. ``And now it's too late because you were so indecisive.''

But others weren't ready to go.

On Southwest Eighth Street's Silver Court trailer park, one of the oldest in Miami, some residents remained unconcerned despite an earlier warning by Miami police.

''We'll see some rain and wind, but this hurricane will be moving northwest,'' said Amador Polanco, 70. ``It won't be anything that will require us to leave.''

But Polanco's brother, Juan Polanco, who lives three trailers away with his mother, was packing up his Buick with important belongings, including their residency papers.

''I have a girlfriend who lives in a sturdy house in Hialeah, and we're going over there,'' he said.

Herald staff writers Oscar Corral and Elinor J. Brecher and Herald writer Eva Busse contributed to this report.

Widespread traffic jams covered the state Thursday as millions of residents made last-minute dashes to lumberyards and grocery stores and started fleeing the coastal zones in anticipation of Hurricane Frances.

''It's not one particular spot . . . it's heavy all over,'' said Lt. Julio Pajon of the Florida Highway Patrol. ``It looks like rush hour out there. It has all day.''

South Florida emergency officials urged evacuees to head west, to inland locales, not north, considering the wide swath that Frances is expected to cut. They said several major highways across the state could be turned into one-way, westbound-only thoroughfares by early today to help accelerate last-minute evacuation efforts.

Miami-Dade officials said public bus service will cease today about two hours before tropical storm-force winds arrive, marking the effective end of the evacuation. On Thursday evening, forecasters expected those winds to arrive about 2 p.m. today.

Broward County Transit shut down Thursday, except for emergency evacuation routes.

Tri-Rail suspended commuter train service Wednesday night as CSX officials informed the regional transportation authority, which operates Tri-Rail, that they needed to begin securing crossing gates.

At times, tempers flared, especially outside gas stations as thousands tried to top off their tanks and fill spare tanks for fuel generators.

Police were called to the U-Gas station on Southwest 148th Avenue in Davie after two men grappled over the same gas nozzle, with onlookers watching in amazement.

''Someone cut in line and got into an argument, and they called us,'' Davie Officer Raul Martinez said. ``Every gas station has a little hot spot and you go to the next spot putting fires out.''

At the Shell station on Biscayne Boulevard near the Interstate 195 overpass, a man who cut into a gas line barely escaped serious harm.

''Before I knew it, three people were out of their cars screaming insults at the guy,'' said Eliezer Rivera, who couldn't believe the man cut in front of him. ``They kicked and pounded the car all over, but it was the driver they really wanted.''

In an effort to reduce the congestions, state officials suspended tolls on Florida's Turnpike, the Miami-Dade Expressway Authority highways, the Sawgrass Expressway in Broward and on westbound Alligator Alley (Interstate 75) between Fort Lauderdale and Naples.

Department of Transportation officials ordered work crews to remove traffic cones and barrels from I-95 construction zones in Palm Beach County to provide more lanes for northbound evacuees.

But across the state, traffic jams kept cropping up.

Bumper-to-bumper traffic was reported on sections of northbound I-95 between Daytona Beach and Jacksonville. Rest areas were packed along Interstate 10. Heavy congestion was reported on I-75 near the merge with Florida's Turnpike in Sumter County.

Further south, a steady river of westbound cars slowly seeped out of Brevard and Indian River counties on State Road 60, one of the few cross-Florida highways, and the BeeLine Expressway connecting Orlando with the Space Coast.

Road rage wasn't isolated to South Florida. Two tractor trailer drivers stuck in an Interstate 4 traffic jam on the north side of Orlando jumped out of their cabs and threw haymakers at each other.

''I've been a cop for 26 years, and I thought I had seen everything,'' Orange County sheriff's Chief Steve Jones, who broke up the fist fight, told The Orlando Sentinel. ``Now I can say I have seen everything.''

Herald staff writers Erika Bolstad, Hector Florin, Mary Ellen Klas, Phil Long, Susannah Nesmith, Charles Rabin and Jeanette Rivera contributed to this report.