Tropical depression forms in Gulf of Mexico

MIAMI (Reuters) - The fifth tropical depression of the 2008 Atlantic hurricane season formed in the northern Gulf of Mexico on Sunday, and was forecast to pass through key U.S. oil production areas before reaching Texas or Louisiana, the U.S. National Hurricane Center said.

One computer model indicated the weather system could reach hurricane strength before making landfall, but the Miami-based hurricane center's official prediction called for it to top out as a tropical storm with maximum winds of 55 knots, or 63 miles per hour (102 km per hour).

It would be called Tropical Storm Edouard once its top winds reach 39 mph (63 kph). Tropical storms become hurricanes when their top sustained winds reach 74 mph (119 kph).

Much of U.S. offshore oil production is in the likely path of the storm, which could also threaten Gulf Coast refineries.

Oil companies have been working to strengthen platforms to withstand hurricane-force winds and so storm level winds should not pose an undue threat.

A series of powerful hurricanes in 2004 and 2005, including Hurricane Katrina, toppled oil rigs and severed pipelines in the Gulf, where the U.S. produces almost a third of its crude and 15 percent of its natural gas.

At 5 p.m. EDT the center of the tropical depression was located around 85 miles southeast of the mouth of the Mississippi River and it was moving to the west at 6 mph (10 kph).

"On the forecast track the center of the cyclone will move parallel to the Louisiana coast tonight and Monday and approach the upper Texas coast on Tuesday," the hurricane center said.

A tropical storm warning, meaning tropical storm conditions could be expected within 24 hours, was posted from the Mississippi River westward to Intracoastal City.

A tropical storm watch, meaning storm conditions are likely to occur within 36 hours, was issued for the coastline west of Intracoastal City to Port O'Connor in Texas.

The six-month hurricane season, which began on June 1, has already seen two of its four storms strengthen into hurricanes. This July was the third most active month of July for storms since Atlantic hurricane season records began in 1851.

The early and unusually vigorous storm activity has given storm experts reason to believe that predictions for an above average season could turn out to be accurate.

Among the storms this year, Hurricane Dolly came ashore on the southern Texas coast on July 23, dousing the area with tremendous downpours but causing relatively little damage.

Hurricane Bertha grazed Bermuda and became the eighth longest-lived Atlantic storm on record before fading over the cool waters of the northern Atlantic while Tropical Storm Cristobal brought heavy rain to the Carolinas.

(Reporting by Michael Christie, additional reporting by Erwin Seba in Houston; Editing by Doina Chiacu)