MIAMI, Sept 4 (Reuters) - Tropical Storm Gabrielle formed in the northeastern Caribbean Sea on Wednesday and was forecast to drench Puerto Rico and the Dominican Republic as it headed into the Atlantic, forecasters at the U.S. National Hurricane Center said.
The storm was centered about 70 miles (110 km) south of San Juan, Puerto Rico. It was expected to curve slowly to the northwest and then turn to the northeast on a path that would take it east of the Turks and Caicos Islands and the Bahamas during the weekend, forecasters said.
Gabrielle packed top sustained winds of 40 mph (65 kph), according to the hurricane center. It was expected to strengthen slowly through Monday but had little chance of growing into the season's first hurricane, forecasters said.
Puerto Rico, the U.S. Virgin Islands and the eastern Dominican Republic can expect heavy rain, with dangerous flash flooding and mudslides in mountainous areas, the forecasters said.
Puerto Rico was already saturated amid one of the wettest years on record. Rainfall in the capital of San Juan was nearly two feet (0.6 meters) above average for the year, meteorologist Jeff Masters said in his Weather Underground blog.
Gabrielle is the seventh tropical storm of the Atlantic-Caribbean hurricane season, which runs from June 1 to Nov. 30 and is now entering its traditionally busiest period.
Reporting by Jane Sutton; Editing by Will Dunham