MIAMI, Dec 11 (Reuters) - Subtropical Storm Olga threatened the northern Caribbean islands with heavy rain, flash flooding and mudslides on Tuesday.

Olga was a relatively weak storm with top sustained winds of 45 mph (75 kph) and forecasters at the U.S. National Hurricane Center predicted strong winds in the upper atmosphere would start to tug it apart on Wednesday.

They said Olga's greatest threat was of torrential rains.

"These rains have already produced life-threatening flash floods and mudslides in Puerto Rico," the forecasters said in an advisory.

Tropical storm warnings and watches were issued for parts of Haiti and the Dominican Republic, which share the island of Hispaniola, and were expected later in the Turks and Caicos islands and the southeastern Bahamas.

At 10 a.m. EST, (1500 GMT) the storm's center was about 130 miles (200 km) east-southeast of the Dominican Republic capital of Santo Domingo.

Olga was moving almost due west near 15 mph (25 kph) on a path that would keep it very near the southern coast of the Dominican Republic on Tuesday.

The storm could dump up to 10 inches (25 cm) of rain on isolated parts of Hispaniola, while Puerto Rico could get another 2 to 4 inches (5 to 10 cm), bringing its total to 12 inches (30 cm) in some areas, the forecasters said.

Most forecasting models showed the storm moving westward across the Caribbean toward Central America for the rest of the week, keeping it well away from U.S. oil and gas production facilities in the Gulf of Mexico.

One model had it crossing western Cuba into the southern Gulf of Mexico and then veering across the southern tip of Florida toward the Atlantic Ocean.

Olga was a subtropical storm, with a cooler core than a tropical storm or hurricane, and formed over the Virgin Islands on Monday, 10 days after the official end of the six-month Atlantic-Caribbean hurricane season.

Tropical storms draw strength from warm seas, so December storms are unusual. Olga was the 17th named storm to form in the region in the month of December since record keeping began in 1851, the hurricane center forecasters said. (Reporting by Jane Sutton, editing by Richard Meares)

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