After strafing coastal communities in four states with strong winds and heavy rain, Hurricane Elena pounded ashore in Mississippi this morning, overturning mobile homes, flooding bridges and highways, and shattering windows as it ripped a path of destruction northwest into Louisiana.

By this afternoon, Elena had diminished into a tropical storm, but it left scattered tornadoes, wind gusts and a few flash floods in its wake.

At least four deaths were attributed to the hurricane, which forced the evacuation of more than 1 million people from Sarasota, Fla., to eastern New Orleans as it toyed with gulf communities for four days. In Biloxi, Miss., dozens of elderly evacuees were trapped under rubble when the roof of an emergency shelter collapsed during Elena's final assault this morning, but no serious injuries were reported.

Initial estimates put the damage from the hurricane -- the fourth this season and the most powerful to hit this region since 1979 -- at hundreds of millions of dollars, not including the untold costs of evacuating entire communities along hundreds of miles of coastline.

According to early American Red Cross estimates, in Leesburg County, Fla., 23 mobile homes were destroyed and 26 others had major damage. At Cedar Key, Fla., and the surrounding area, battered by the hurricane for two days, 100 mobile homes were reported severely damaged, Red Cross spokeswoman Terry Gautier said.

Yankeetown, Fla., just to the north, was said to be still inaccessible as of this evening because of flooding. The Red Cross had not completed damage estimates for other states by evening.

Mississippi Gov. William A. Allain announced that he would ask President Reagan to declare the coastal counties a disaster area, and other coastal governors were expected to follow suit.

Florida Gov. Robert Graham toured some of the affected parts of his state by helicopter this morning. Gov. Edwin W. Edwards of Louisiana immediately declared a state of emergency for his state's coastal counties.

One of the hardest-hit towns was Biloxi, near where the eye of the storm roared ashore at 8 a.m. EDT with winds over 120 miles per hour. Streets were flooded, power lines were ripped down, roofs were sheared from scores of beach houses and winds knocked the roof from an elementary school being used as an emergency shelter.

Further to the east, in Pascagoula, near the Alabama border, the force of Elena's winds shattered car windows and destroyed all the official county vehicles that were left parked in a courthouse lot. A building was ripped to its girders, and one Red Cross worker commented, "This city looks bombed."

The low number of deaths and injuries was attributed to the National Weather Service's sophisticated hurricane tracking system, which provided almost hourly updates of Elena's whereabouts as she prowled the Gulf of Mexico over the Labor Day weekend, growing in intensity.

"The consequence of everybody knowing what to do is that we didn't have any injuries or deaths here," said Mobile Mayor Lambert Mims, speaking of his own city. "This was one of the most erratic ones we've seen. It came up the Gulf in a straight shot towards Mobile, then took a sharp right turn towards Florida, stopped, turned left and headed back."

Mims said the area of Mobile most heavily damaged was Dauphin Island, just off the Alabama coast in Mobile Bay. As of late today, police had refused to allow the island's 300 permanent residents to return to inspect the damage to their homes. The bridge to the island was still partially flooded. But the bridge, which had washed away six years ago in Hurricane Frederic, withstood Elena's onslaught.

Some residents, like Bill Buerger, 61, who owns the Ship and Shore convenience store on the island, chose to remain, and sheriff's deputies reported today that all residents still there were alive and well.

"They were all out riding in their cars afterwards," said Assistant Chief Deputy Neal Schafer of the Mobile County Sheriff's Department. "I guess the Good Lord smiled on them." However, telephone lines were still dead and power remained cut off to the island as of nightfall.

Mobile residents, like those in other northern Gulf communities, were forced to evacuate last Friday, then allowed to return on Saturday when it looked as if Elena would make a landfall on the Florida coast. On Sunday night, however, residents had to evacuate again.

The hurricane had parked about 50 miles off the coast on Saturday and began pounding the area from Cedar Key to densely populated St. Petersburg with torrential rains and tornadoes before increasing its strength and changing course.

Authorities feared that Elena, on its new course, might hit vulnerable New Orleans; the eastern portions of that city were again evacuated for the second time in three days. The causeway road over Lake Pontchartrain was closed for most of this morning.

Only two weeks ago, the city took a heavy pounding from Hurricane Danny, and Red Cross personnel were still in the region from that emergency.

On its return trip around the Gulf, Elena essentially traveled the arc of the Florida Panhandle, spraying the coastal communities along the way. A drive from Tallahassee westward along the coast tracked the hurricane's curve and revealed the destruction it wrought.

The town of Apalachicola was flooded after the hurricane swept by, and its roads left impassable. Waves cresting to six feet crashed over the coastal highway, and police roadblocks kept residents and the curious from venturing near the coast.

Most residents rode out the storm huddled in a shelter 30 miles inland. Further west in Pensacola, the heavy wind gusts reached 90 mph Sunday night and early this morning, shattering windows and overturning mobile homes. Some power lines were downed, darkening much of the city.

U.S. Highway 10, which typically would be packed with holiday weekend travelers, was nearly deserted, except for the few evacuees who ventured out early to return to their homes, and a few television camera crews and reporters, who had been tracking Elena up and down the Gulf since Friday.

As communities began the massive task today of cleaning up the wreckage and assessing the damage, there was much comparing of Elena's fury to that of hurricanes past.

Hank Turk, civil defense director for Jackson County, Miss., told the Associated Press, "Preliminary indications are that the damage is more extensive than Frederic in 1979" in Pascagoula.

Forecaster Hal Gerrish at the National Hurricane Center in Miami told the AP that Elena "was a major hurricane" and "worse than Frederic."

But residents of Mobile, which took the brunt of that earlier storm, had an easier time with Elena.

"At this point in time, [after] Frederic, you couldn't even walk out your door because your ears would ring with the sound of chainsaws cutting broken limbs," said Mobile City Commissioner Bob Doyle.

Mayor Mims added, "Frederic almost wiped us off the map."

Sixteen years ago, the Gulf Coast was devastated by Camille, the strongest hurricane to strike the U.S. mainland since records have been kept, with winds of up to 175 miles an hour. It left more than 250 people dead, 68 missing and $1.4 billion worth of property damage after it traveled across several southern states.

Poor tracking and evacuation procedures during Camille led to the computerization of the National Hurricane Center and an overhaul of advisory and evacuation systems.

Elena, which began off the coast of Africa 12 days ago, was initially rated a Class 2 hurricane, using a scale on which a Class 5 storm is the most severe. But as the storm hovered off the Florida coast Saturday and Sunday, she gained strength and the classification was upgraded to a Class 3 hurricane, with sustained winds of up to 125 miles an hour.

The hurricane deaths include a Daytona Beach man, who was killed in his car by a falling limb, and two Florida heart attack victims in the Tampa-St. Petersburg area. The Associated Press reported one person killed in a Louisiana traffic accident as he fled the hurricane.

A Los Angeles Clippers spokesman said he expected an announcement today on the planned National Basketball Association trade of Bill Walton for Cedric Maxwell of the Boston Celtics.

"The last I heard was last night that they are still trying to work out details and that minor developments have come up each day," the Clippers' Scott Carmichael said.

Celtics spokesman Jeff Twiss said he could not predict when the trade would be completed, but said the league has given preliminary approval. Walton and Maxwell passed team physicals last week, Twiss said.

Mr Trucka Jet won the $2 million All American Futurity for quarter horses at Ruidoso Downs, N.M. Jacky Martin became the first three-time winning jockey and Jack Brooks a triple-winning trainer in the event as their strapping colt outjumped favored Dashing Phoebe at the start of the 440-yard sprint, then ran down the fast-closing Digging For Gold in the final 50 yards.

Mr Trucka Jet's 21.41 seconds matched the Futurity record. The victory paid owner Darrell Kissee of Miami, Okla., $1 million . . .

In Belmont Park's Labor Day feature in New York, Woody Stephens-trained Belmont Stakes winner Creme Fraiche, ridden by Eddie Maple, overtook the leaders at the top of the stretch and captured the $182,000 Jerome Handicap. He was timed in 1:34 3/5 for the mile, beat Pancho Villa by 1 3/4 lengths and paid $8.20 at the $2 windows . . .

Lightly raced 5-year-old Barberstown ($12.20) held off My Habitony to win the $240,500 Del Mar (Calif.) Handicap, about 1 3/16 miles, by a half-length . . .

Eight 2-year-old fillies, headed by Likker Is Quikker, are scheduled to run in today's $33,300 Toddler Stakes at Pimlico. Today's program marks the resumption of the Baltimore track's 49-day summer meeting put on hold while Timonium ran its 10-day meeting during the Maryland State Fair. Pimlico will run through Sept 21.

Likker Is Quikker is the lukewarm overnight choice and joint highweight at 118 pounds for the Toddler, having won two of five career starts.

North Of Danzig, conditioned by Hall of Fame trainer Stephens, is the second choice, getting into the six-furlong featiure with 109 pounds.

Betsy King birdied two of the final three holes in a five-under-par 67 for a three-day total of 205 and won the $185,000 Rail Charity Golf Classic in Springfield, Ill., by two strokes over Janet Anderson, who bogeyed the last hole.

King, in the final round, parred each of the first nine holes, made five birdies on the back nine and earned $27,750. Anderson, who led King most of the round, earned $17,112.

Nancy Lopez came within two shots of the lead with a front nine of 33. But Lopez never got any closer despite a 67 of her own.

An extra large panel of prospective jurors, 50 instead of the usual 35 in case the heavy publicity makes selection difficult, was summoned to U.S. District Court in Pittsburgh for selection of a 12-person panel to hear the case against Curtis Strong, the Philadelphia caterer accused of selling cocaine to major league baseball players.

Strong, 38, was one of seven men indicted on federal drug charges after a lengthy grand jury investigation in which at least a dozen former or current major leaguers were interviewed -- and granted immunity from prosecution -- and 10 of them have been listed as potential prosecution witnesses in the case against Strong.

Strong, accused in a 16-count indictment of distributing cocaine in Pittsburgh between 1980 and 1984, is the first of the seven to stand trial. One of three who pleaded guilty admitted to 19 counts of selling drugs to Pirates pitcher Rod Scurry and one of selling to former Pirate Parrot mascot Kevin Koch, who set up the buy as a cooperating wit news for the FBI.

Glenn Wilson scored the deciding penalty kick in the sixth round of a shootout to give the Reston Gold a 2-1 victory over the Springfield Stallions for the 19-and-under championship of the Fairfax Police Youth Club Labor Day tournament in Fairfax City. Reston's Rickie Engelfried forced overtime by making a left-footed shot, with three minutes left in regulation, off a direct kick from 15 yards. David Lausten had scored early on for Springfield.

In the girls 19-and-under final, Kathi Nidiffer scored near the end of the first half on a pass from Meredith Yarbrough and their Fairfax Cobras held on to defeat Springfield Express, 2-1. Springfield's Michelle Woodside had created a 1-1 tie midway through the half. Fairfax's Meredith Yarbrough then centered from the left to Nidiffer, who scored.