Washington  - Two tropical storms were moving across the Caribbean and Gulf of Mexico late Sunday, with Bill threatening to become a hurricane and Claudette poised to strike the coast of Florida by Monday morning.

The storms, along with Ana, which has been downgraded to a tropical depression, are the first storms of the unusually quiet Atlantic hurricane season, which began in early June.

Bill was still far to the east, 2,315 kilometres east of the Lesser Antilles, at 2100 GMT Sunday, the National Hurricane Center in Miami, Florida, reported. Bill was carrying 100 km/hr winds and moving about 26 km/hr toward the west-north-west.

"Bill is expected to become a hurricane later tonight or tomorrow," the hurricane center said.

Florida was bracing for heavy rains and winds by Monday morning as Claudette aimed at the panhandle. At 0000 GMT, Claudette was 155 kilometres south of Pensacola, Florida, moving about 19 km/hr. Winds were 85 km/hr.

Claudette also spawned a tornado in Florida on Sunday, MSNBC weather reported.

Ana was "poorly organized," said the hurricane center, which discontinued the tropical storm watch for the island nation of Dominica at 0000 GMT.

Nonetheless, a tropical storm watch remained in effect for Ana for the Dominica Republic, Puerto Rico, the Virgin Islands and other countries in its westward pathway. It was expected to hit the northern Caribbean Sea Monday morning. (dpa)