Cindy, which had crossed Mexico's Yucatan Peninsula as a tropical depression, reached tropical storm strength early Tuesday and by early afternoon had sustained wind of around 60 mph. The second storm became Tropical Storm Dennis as it developed wind of 40 mph. The minimum for a tropical storm is 39 mph.
Cindy could strengthen further before its center reaches the coast late Tuesday or early Wednesday, but it is not expected to become a hurricane, said the National Hurricane Center in Miami.
A tropical storm warning was posted from Intracoastal City, La., to the Florida Panhandle town of Destin.
The main danger would be if Cindy stalls along the coast, dumping heavy rain over a small area for an extended period, said sheriff's Capt. Mike Sanders in coastal St. Bernard Parish.
Officials of Louisiana's coastal Lafourche Parish called for a voluntary evacuation of the lower portion of the parish outside of storm protection levees.
Water levels were lowered about a foot in canals along part of the Louisiana coast in anticipation of high water, and the barrier island town of Grand Isle, a popular fishing spot, ordered all recreational vehicles removed to get the big, slow machines out of the way in case evacuations are needed.
In Mississippi's coastal Hancock County, jail inmates filled sandbags for distribution to flood-prone areas, said Dee Lumpkin of the county's Emergency Operations Center.
Shell Oil Co. said 56 people were evacuated from offshore facilities in the Gulf of Mexico and Chevron Texaco said it had started evacuations. Shell said on its Web site that production was not affected.
At 2 p.m. EDT, Cindy was centered 125 miles southwest of the mouth of the Mississippi River and was moving north at about 14 mph, with a gradual turn expected toward the northeast. Tropical storm-force wind and rain extended up to 105 miles to the east of its center.
Dennis was centered about 335 miles south-southwest of San Juan, Puerto Rico, and moving west-northwest at about 20 mph. It was on track to reach Haiti on Wednesday and South Florida on Friday, said hurricane center meteorologist Trisha Wallace. Tropical storm watches were posted for parts of Haiti and the Dominican Republic.
Elsewhere, Tropical Storm Dora in the Pacific was moving toward Mexico's southwest coast. It had maximum sustained wind of 40 mph and meteorologists did not expect it to strengthen significantly.