Tropical Storm Irene barreled across the Caribbean toward Puerto Rico on Sunday on a course that could take it to Florida.

Irene, the ninth named storm of the 2011 Atlantic hurricane season, was expected to pass over Puerto Rico overnight and could strengthen into a hurricane as it approached the Dominican Republic on Monday, forecasters at the U.S. National Hurricane Center said.

It would be the first hurricane of the busy -- but so far not destructive -- 2011 Atlantic hurricane season.

At 5 p.m. (2100 GMT), Irene had top winds of 50 miles per hour and was near the U.S. Virgin Island of St. Croix, about 120 miles east-southeast of San Juan, Puerto Rico. Irene was a large storm and moving west-northwest.

Strengthening is forecast and Irene is expected to be near hurricane intensity on Monday. Weakening is likely later on Monday as the center moves near or over the Dominican Republic, the Hurricane Center forecasters said.

The storm pelted the Leeward Islands with heavy rain and squalls as it crossed from the Atlantic Ocean into the northeastern Caribbean Sea on Sunday.

Hurricane watches and warnings were in effect in the U.S. Virgin Islands, Puerto Rico and the Dominican Republic. Tropical storm warnings were in effect for the Virgin Islands, Haiti, the Turks and Caicos islands and the southeastern Bahamas.

Puerto Rico lifted a ban on Sunday morning shopping, allowing stores to open so residents could stock up on canned food, bottled water and other necessities. Prices were frozen and alcohol sales were halted until after the storm passes.

Puerto Rico Secretary of State Kenneth McClintock said schools and government offices would be closed on Monday in the U.S. territory, and urged residents to finish their preparations then stay inside their homes.

You have to think about protecting life, McClintock said at a news conference.

Governor Luis Fortuno flew back to Puerto Rico after taking over the chairmanship of the Southern Governors Association on Sunday at the group's convention in North Carolina.

Ferry service to the islands of Vieques and Culebra was halted and several inter-Caribbean flights from San Juan's Luis Munoz Marin Airport were canceled.

WATCHING IRENE'S PATH

In the Dominican Republic, authorities warned of abnormal waves up to 15 feet high. Weeks of heavy rainfall have already caused deadly flooding in the Dominican Republic and authorities said they may issue evacuation orders for vulnerable areas on Monday.

Residents of Cuba, the Turks and Caicos Islands, the Bahamas and the southeastern United States were urged to monitor Irene's progress as the storm headed their way.

Computer forecast models showed Irene moving northwest over the Dominican Republic, Haiti and possibly eastern Cuba and then heading toward the Florida peninsula.

Depending on its eventual path and possible turns, Irene might still pose a threat to U.S. oil and gas installations in the Gulf of Mexico, but forecasters say it is too early to predict with certitude.

An early northward turn would bring it near the Georgia-South Carolina coast late in the week but a later turn could take it over western Cuba and into the Gulf of Mexico.

Tropical Storm Harvey hit Belize in Central America on Saturday and weakened to a tropical depression as it moved inland. It crossed into Mexico's Bay of Campeche on Sunday and forecasters said it could briefly strengthen back into a tropical storm before hitting the southern coast of Mexico.

Mudslides and flooding could affect agricultural output in Central America, but this year's coffee and sugar harvests are largely complete.

Mexico Florida Cuba Mexico