-- Hurricane Dennis, a tightly wound storm with a ferocious core, spiraled onto the Florida Panhandle on Sunday afternoon, shredding signs and toppling trees in coastal communities still recovering from an onslaught of three tropical storms in the past month and a monster hurricane less than a year ago.

Dennis, which had slackened slightly to a Category 3 hurricane with 120-mph winds, burst ashore just east of Pensacola at 3:25 p.m. Eastern time on Santa Rosa Island, a gangly 50-mile, barrier-island beach retreat where the legendary Apache warrior Geronimo was once imprisoned.

Aluminum sheets flew off roofs, violently cartwheeling down abandoned streets, and the seas lifted to frightening heights under wind gusts that shrieked into an afternoon sky so dark that it almost looked like night. Power lines sagged, leaving many homes and businesses, and even entire towns, without light. Gulf Power, the Panhandle's largest electric company, presaged the misery to come by warning 400,000 customers that they could be without electricity for three weeks or more. About 280,000 homes and businesses in Alabama were believed to be without power.

No deaths were reported in the storm's wake. The Associated Press reported that Dennis caused an estimated $1 billion to $2.5 billion in insured damage in the United States, according to AIR worldwide Corp. of Boston, an insurance-risk modeling company.

The last-minute weakening of a storm that earlier in the day had carried 145 mph winds was a relief to many in the region. But Florida Gov. Jeb Bush (R) and National Hurricane Center Director Max Mayfield compared the drop-off to "the difference between getting hit by a semi-truck or a freight train."

Dennis was compared with Ivan, another Category 3 hurricane that hit just up the coast in September in Gulf Shores, Ala. Ivan killed 52 people in the United States while causing $10 billion in insured damage.

But Dennis established its own identity. It arrived remarkably early, stirring the sand between Pensacola Beach and Navarre Beach as the first major hurricane to hit the United States in July in 150 years of recorded history and only the seventh Category 3 or stronger hurricane to form in that period. It also moved quicker than Ivan, smashing the coastline with a fast, concentrated jab from its more compact core, then moving on.

"This one was very, very intense all at once," said restaurateur Nick Zangari, whose penchant for serving meatball sandwiches at New York Nick's right up to the moment of hurricane impact has made him a celebrity in Pensacola. "You had things flying by like 'The Wizard of Oz' movie."

By 11 p.m. Eastern time, Dennis had been downgraded to a tropical storm with 50-mph winds, and was 25 miles southeast of Demopolis, Ala. Forecasters said it was a tornado and flooding threat but should weaken to a tropical depression by Monday. The National Hurricane Center said it would meander through Alabama, Tennessee and southern Illinois before curling into Ohio and dissipating at the end of the week.

When evening approached, National Guard convoys rolled into the Panhandle as Dennis moved inland, dropping heavy rain on lower Alabama.

Power outages were reported throughout the region, but again Dennis seemed to inflict less woe than Ivan.

"It doesn't appear that this storm has created as much widespread destruction as Ivan did, at least from a power-outage standpoint," said John Hutchinson, spokesman for Gulf Power Co. "After Ivan, we did not have one light bulb burning in Santa Rosa or Escambia counties, and right now we have power in both of those places."

Still, the true scope of the massive storm was only beginning to come into focus Sunday evening, while hundreds of relief crews arrived to assess damage before darkness made their work impossibly treacherous. The day after a hurricane, the storm veterans in this area know, often reveals much more damage than anticipated when the winds were still whipping.

Dennis spread hurricane-force winds over 40 miles of coastline dotted with tiny beach communities, simultaneously beloved as summer havens, and affectionately dubbed the "Redneck Riviera" by some of its frequent visitors. But the width of the storm's destructive power was much greater, with damaging winds of tropical-storm force, and accompanying storm surges extending more than 100 miles from its core.

Gen. Douglas Burnett of the Florida National Guard said the return of units from Iraq gave him far greater troop numbers than the Guard had during last year's four-hurricane season; relief efforts in Florida were then hampered because of the mass call-up of National Guard units for overseas duties. Four battalions were on standby or on their way to the Panhandle late Sunday, along with a contingent of heavy Chinook helicopters.

The relief effort is sure to be complicated by the delicate geography of the area; much of the most vulnerable communities is connected to the mainland only by small bridges susceptible to the punishing 15-foot storm surge kicked up by Dennis. Dive teams were dispatched to check whether roughed-up bridges would hold.

The trajectory of the storm kept it away from the largest population centers. Early Sunday, Dennis appeared headed directly for Mobile Bay, a potentially dangerous landfall point that could have submerged much of Mobile's historic downtown. Alabama Gov. Bob Riley ordered a mass evacuation of Mobile, the most extensive in state history, and residents who in past years had seemed blase about hurricane threats responded en masse.

More than 1.5 million people live in areas throughout the region affected by evacuation orders, and traffic counts led officials to believe that huge numbers heeded the warning and left. By Sunday afternoon, for instance, 98 percent of the hotel rooms in Alabama were filled as the outer edges of Dennis slapped Mobile with heavy wind and rain. At the eastern entrance to town, several dozen people sought the most ingenious of shelters: the living quarters inside the heavy metal hull of the USS Alabama, a retired World War II battleship that has become one of the state's most popular tourist attractions.

Others took more traditional coping measures, opting for the comforts of a storm-season standby: the hurricane party. At the VFW Hall on Hollinger's Island near Mobile, Commander Harry Smith was not planning to open, but his regulars insisted.

As rain pelted the little hall, C.D. Hauser, a retired Navy man, downed a Bloody Mary and declared, "I'm going back to Arkansas" as the jukebox blared lyrics that gave the place the feel of a parallel reality: "I can see clearly now, the rain is gone."

To be sure, there was much to make residents wonder if what was happening to them was real. The area was drenched just six days earlier by a strong tropical storm, Cindy, after two previous tropical storms had also whisked through the area.

Escambia County Administrator George Touart said all of the season's named storms had slapped his county. "We're beginning to wonder what we've done wrong," he said.

Cassandra Trial, 46, does not plan to stick around to find out. She moved to Pensacola from Los Angeles in March so that she could be closer to her daughter. Since then, it seems she has done little more than watch rain and wind.

"This is too much for me," said Trial, who staked a spot among 300 other people in an elementary school-turned-shelter on Sunday. "I'm going back to California and deal with the earthquakes. Roofs blowing off and all this -- no, I can't have it."

All around are signs of last year's unprecedented clumps of hurricanes: hundreds of broken roofs covered by blue tarps and billboards with great chunks bitten out of their middles by the wind.

"Before we could get our heads all the way back up above the water, we're being pushed down again," said Susan Walden, a writer in Pensacola.

But the hardy types are evident here, too, the ones who refused to leave and within minutes of facing down Dennis were grasping from some semblance of normal. Thi Nhuang Bina was open for business less than three hours after Dennis passed, selling sodas and bottled water from her convenience store on W Street in Pensacola.

Outside, Laderick Ward, 26, lined up with a dozen others, hoping there would still be a cold beer in the refrigerator when he got inside to calm his nerves.

"It was very strong," Ward said of Dennis, "but Ivan took away everything that was weak. . . . Pretty soon, there won't be anything left to tear up."

Roig-Franzia reported from Mobile. Staff writer Hamil R. Harris in Cape Canaveral contributed to this report.

An unidentified man tries to push water away from his business while Hurricane Dennis is hitting Pensacola Beach, Fla.Richard Newcome talks to a neighbor on his cell phone as he surveys the high water from Hurricane Dennis in Gulf Breeze, Fla. Newcome was checking a home for friends who evacuated the area.An employee of Drury Inn and Suites in Montgomery, Ala., tapes up the windows of the new hotel as Hurricane Dennis approaches. Dennis was downgraded to a tropical storm after traveling inland through Alabama.Marsha Gustafsson enjoys a light moment after Dennis passed Gulf Breeze.