MIAMI, Florida (CNN) -- Tropical Storm Fay formed Friday over the Dominican Republic in the Caribbean Sea, the National Hurricane Center said.
The storm, the sixth of the Atlantic 2008 season, had maximum sustained winds near 45 mph (75 km/hr), with higher gusts, forecasters said.
"Reports from [the National Oceanic and Atmospheric Administration] and Air Force Reserve hurricane hunter aircraft indicate that the low pressure area over the Mona Passage became a tropical storm as it moved into the eastern Dominican Republic," the hurricane center said in an advisory.
As of 8 p.m. ET, the center of Fay was moving across Hispaniola -- the island containing the Dominican Republic and Haiti -- and was about 35 miles (55 km) west-northwest of Santo Domingo, Dominican Republic, and about 335 miles (540 km) east-southeast of Guantanamo, Cuba.
It was moving west at about 14 mph (22 km/hr) and was expected to continue moving west-northwest over the next day, forecasters said.
Fay is expected to dump 4 to 8 inches of rain over Hispaniola and eastern Cuba, with possible isolated amounts up to 12 inches, the hurricane center said. Heavy rain could trigger floods and mudslides and raise tides 1 to 2 feet above normal levels in the warning area.
A tropical storm warning was issued for the northern coast of the Dominican Republic and for the southern coast east of San Pedro de Macoris, forecasters said. A warning was also issued for the northern coast of Haiti from Gonaives northward, and the government of Cuba issued a warning for Guantanamo, Santiago de Cuba and Granma provinces.
A tropical storm warning means tropical storm conditions are expected in the warning area within the next 24 hours.
A tropical storm watch was issued for the Cuban provinces of Holguin and Las Tunas, the hurricane center said. A watch means tropical storm conditions are possible within 36 hours.
"The center of Fay will cross Hispaniola tonight and Saturday, and pass near or over eastern Cuba Saturday night and Sunday," the hurricane center said.
Long-range forecasts show the storm reaching the Florida Keys late Monday before heading into the southeastern United States. However, because of the erratic nature of hurricane movement, long-range forecasts often vary from the eventual track.
The storm's intensity is not expected to fluctuate while its center is over Hispaniola, forecasters said. Its strongest winds were occurring to the north and east of its center.