Miami, Florida (CNN) -- A weather system moving over the southern Bahamas has been upgraded to a tropical storm, with sustained winds now reported at 40 miles an hour, as it heads toward the southern tip of Florida and the Gulf of Mexico. The system has been named Tropical Storm Bonnie. At 11 p.m. ET, it was moving northwest at 14 miles an hour as it approached the northwestern Bahamas, according to the National Hurricane Center. It could pick up strength as it moves over the long stretch of open water in the Gulf of Mexico, but the latest computer models do not show it becoming a hurricane, according to CNN meteorologist Chad Myers.
@highlight
Louisiana declares emergency as storm approaches
@highlight
Thad Allen orders ships at BP well site to shore
@highlight
Weather system upgraded to tropical storm
@highlight
Latest computer models show the storm moving into the Gulf of Mexico
The hurricane center predicted that the storm would bring 2 to 4 inches of rain to south @placeholder, with isolated areas receiving as much as 6 inches.