Tropical Storm Isaac forms in the Atlantic, expected to strengthen

Tropical Storm Isaac formed Wednesday in the Atlantic Ocean and is expected to strengthen as it moves eastward, possibly becoming a hurricane by the end of the week, forecasters said.

Isaac was about 690 miles (1,115 kilometres) northeast of Bermuda with top sustained winds of 50 mph (85 kph), according to the US National Hurricane Centre in Miami. It was moving east at about 12 mph (19 kph).

A tropical storm is defined by sustained winds between 39 mph and 73 mph (62 kph and 117 kph). Winds above that make it a hurricane.

Isaac is the ninth named storm in what is predicted to be a busy hurricane season, which runs from June 1 to November 30 in the Atlantic.

The National Oceanic and Atmospheric Administration predicts between 17 and 25 named storms, with as many as 13 hurricanes and four major hurricanes.

An average Atlantic hurricane season produces 14 named storms, seven of them hurricanes and three major hurricanes.