Havana ? Hurricane Lili strengthened Tuesday as it roared across western Cuba and into the Gulf of Mexico, forcing thousands from their homes on the island before taking aim at the U.S. Gulf Coast.

Residents in South Louisiana faced their second evacuation in a week as Lili steadily gained strength and speed as it headed their way. “We’re probably going to be evacuating some time (Wednesday) morning,” said Ray Santiny, city councilman from the barrier island of Grand Isle, south of New Orleans.

NASA postponed today’s shuttle launch because of the storm. The space agency said it did not want to take a chance of launching Atlantis from Cape Canaveral, Fla., only to have the hurricane bear down on Houston, home to Mission Control. NASA said Thursday would be the earliest the launch could occur.

Lili was upgraded to a Category 2 hurricane Tuesday afternoon when its winds increased to nearly 100 mph as it whipped across Cuba. No casualties were reported in Cuba, but the storm earlier killed seven people in Jamaica and St. Vincent.

A hurricane watch was declared for the northern U.S. Gulf Coast in Texas to the mouth of the Mississippi River in Louisiana, meaning hurricane conditions were possible within 36 hours. A tropical storm watch was in effect from the Mississippi River to Pascagoula, Miss.

The National Hurricane Center in Miami said some squalls with gusts to tropical storm force could occur over the lower Florida Keys overnight.

“By the time the storm gets to the United States, it will be stronger and it will pack a bigger storm surge,” said Martin Nelson, lead forecaster at the U.S. National Hurricane Center in Miami.

At 8 p.m., the eye of the storm had cleared Cuban territory and was in the Gulf of Mexico, about 90 miles north of the western tip of Cuba and about 560 miles southeast of New Orleans.

Lili, the fourth hurricane of the Atlantic season, was moving northwest at about 15 mph and its wind speeds had increased slightly, to 105 mph. It could strike the Gulf Coast area by Thursday or Friday, Nelson said.