Tropical storm Cristobal takes aim at Bahamas

A strengthening tropical depression is on a collision course for the Bahamas. Tropical storm Cristobal could continue to expand through the next several days.

A strengthening tropical depression that dumped heavy rains on parts of Puerto Rico and the Dominican Republic was upgraded early Sunday to tropical storm Cristobal as it passed closer to the Bahamas, the US Hurricane Center said.

Cristobal originally formed as depression over the Turks and Caicos Islands on Saturday. It was the fourth depression of the Atlantic hurricane season.

Sunday morning, the depression had sustained winds of 35 mph and was located about 40 miles north northwest of Mayaguana island, the hurricane center said in a tropical advisory. The storm was moving northwest at about 9 mph.

A tropical storm warning has been issued for the Turks and Caicos and for the southeast and central Bahamas, with forecasters saying it could bring up to 8 inches (20 centimeters) of rain.

The storm was upgraded to a tropical depression on Saturday afternoon, and it had previously downed several trees and power lines in Puerto Rico, leaving more than 17,000 people without power and nearly 5,600 without water.

Police said in a statement that a small bridge collapsed Saturday in the central town of Barranquitas, isolating some 25 families in the area. No one was injured.

Cristobal is expected to track parallel to the US southeast coast Wednesday and Thursday, when it could intensify into a very strong tropical storm or hurricane, Accuweather.com forecasts.

Cristobal will be tracking along the western periphery of the Atlantic ridge of high pressure. How close Cristobal comes to the southeastern U.S. will depend on how far west the ridge builds.

Cristobal is currently forecast to remain offshore, it is possible though that the tropical system tracks a bit closer to land, grazing the North Carolina beaches with its outermost rain and wind.

"Even if a tropical storm or hurricane was to stay east of the Atlantic coast of the U.S., a strong system would generate swells that propagate outward that could reach the shoreline in the form of rough surf and strong rip currents during the last week of August," warned AccuWeather.com Senior Meteorologist Alex Sosnowski.