Isaac expected to become hurricane as it nears Florida

Tropical Storm Isaac is pictured August 24, 2012, as it passes over Haiti and the Dominican Republic. Isaac has opportunities to strengthen into a Category 1 hurricane.

Last Updated 5:19 p.m. ET

(CBS/AP) MIAMI - Tropical Storm Isaac swept across Haiti's southern peninsula early Saturday, bringing flooding and at least three deaths while adding to the misery of a poor nation still trying to recover from the terrible 2010 earthquake. At least three people were reported dead.

Forecasters expect the storm, which is packing heavy rain and 60-mph winds, to move over Cuba today and become a hurricane tomorrow.

Florida Gov. Rick Scott declared a state of emergency and officials urged vacationers to leave the Florida Keys, after forecasters expanded hurricane warnings and watches for parts of Florida, just as the Republican Party gathers for its national convention in Tampa.

CBS News hurricane consultant David Bernard reports there is great concern in South Florida and the Keys - and for the rest of the peninsula as well - as the storm approaches.

By late Saturday afternoon the storm was about 120 miles east of Camaguey, Cuba, moving northwest at 21 mph. Bernard says the future track of Isaac brings it to a Category 1 on Sunday afternoon, with the possibility of becoming even stronger than that.

By Monday night or Tuesday morning, it will make its closest approach to the west coast of Florida including the Tampa area, with a second landfall possible as Wednesday or Thursday.

Organizers of next week's Republican National Convention in Tampa say they are monitoring the storm. Some 70,000 delegates, journalists and protesters are expected, and Florida Gov. Rick Scott said there are no plans to cancel the convention.

A hurricane warning is in effect for the Florida Keys including the Dry Tortugas; the west coast of Florida from Bonita Beach southward to Ocean Reef, and Florida Bay.

A hurricane watch is in effect for Florida's east coast from Golden Beach southward to Ocean Reef, Andros Island in the Bahamas and Haiti. A hurricane watch means that hurricane conditions are possible within the watch area within the next 24 to 36 hours.

The tropical storm warning has been extended northward along Florida's east coast to Sebastian Inlet. Tropical storm watches have been issued along Florida's east coast north of Sebastian Inlet to Flagler Beach, and for Florida's west coast, north of Bonita Beach to Tarpon Springs. A tropical storm watch has been issued for Florida's west coast north of Tarpon Springs to Suwannee River.

The tropical storm watch for Jamaica has been discontinued.

Three dead in Haiti

In Haiti a woman and a child died in the town of Souvenance, Sen. Francisco Delacruz told a local radio station. A 10-year-old girl died in Thomazeau when a wall fell on his, said Marie Alta Jean-Baptiste, director of Haiti's Civil Protection Office. She said as many as 5,000 people were evacuated because of flooding.

Many, however, stayed and suffered.

In the shantytown of Cite Soleil, just north of Port-au-Prince, about 300 homes had either their roofs blown off or sitting in three feet (one meter) of water, according to Rachel Brumbaugh, operation manager for the U.S. nonprofit group World Vision.

"From last night, we're in misery," said Cite Soleil resident Jean-Gymar Joseph. "All our children are sleeping in the mud, in the rain."

More than 50 tents in a quake settlement collapsed, forcing people to scramble through the mud to try to save their belongings.

Forecasters said Isaac could dump as much as eight to 12 inches and even up to 20 inches on Hispaniola, which is shared by Haiti and the Dominican Republic, as well as produce a storm surge of up to 3 feet.

In Port-au-Prince, a city of some 3 million ringed by mountains, authorities and aid workers tried to evacuate people from a tent camp to temporary shelters.

More than a hundred people were at a shelter in a school that President Michel Martelly toured Friday, but after the visit some people began to leave.

"They dragged me from the camp and brought me here," 38-year-old Marlene Charles, thirsty and hungry, said about the aid groups. "There's no way I'm going to spend the night here."

In the Dominican Republic, authorities said they evacuated nearly 3,000 people from low-lying areas, and at least 10 rural settlements were cut off by flooding, according to Juan Manuel Mendez, director of rescue teams. Power was out in parts of the capital, Santo Domingo, but there were no reports of injuries.

Cuba declared a state of alert Friday for six eastern provinces and five central provinces were put on preliminary watch. Vacationers in tourist installations of those regions were evacuated.

State television began an all-day transmission of news about the storm on Saturday.

Radio Baracoa, from the city of Baracoa on the northern coast of eastern Cuba, reported that high seas began topping the city's seawall Friday night. Reports said lower than normal rains had left reservoirs well below capacity and in good shape to absorb runoff.

Cuba has a highly organized civil defense system that goes door-to-door to enforce evacuations of at-risk areas, largely averting casualties from storms even when they cause major flooding and significant damage to crops.

Out in the eastern Atlantic, former Tropical Storm Joyce degenerated into a weak low pressure system Friday.