WRAPUP 3-Hurricane Gustav roars toward Caymans, Gulf

(Updates storm position, adds details, projected storm surge)

By Alan Markoff

GEORGE TOWN, Aug 29 (Reuters) - Hurricane Gustav gathered strength over the warm waters of the Caribbean on Friday roaring toward the Cayman Islands and the Gulf of Mexico on the third anniversary of Hurricane Katrina's deadly strike on New Orleans.

The storm, which killed up to 77 people in the Caribbean, plowed toward superheated waters south of Cuba where it could absorb enough energy to strengthen into a major hurricane before ripping through the heavy concentration of U.S. oil and natural gas platforms off Louisiana.

While long-range storm forecasts are prone to huge errors, the most likely track had Gustav going ashore west of New Orleans Tuesday morning as a Category 3 storm on the five-stage Saffir-Simpson scale of hurricane intensity.

U.S. emergency officials warned that Gustav was expected to be accompanied by a 15 to 30 foot (5 to 9 metre) storm surge along the Gulf Coast and said four states in its potential path were expected to begin large-scale evacuations on Saturday.

"This storm has the potential for being a very dangerous storm," said Bill Irwin, a program director with the U.S. Army Corps of Engineers.

Oil prices slipped on Friday after a week of volatile trading due to Gustav's threat to the 4,000 Gulf platforms that produce a quarter of U.S. oil and 15 percent of its natural gas. Energy companies evacuated offshore workers and shut production in preparation for the most serious Gulf storm since the devastating 2005 Atlantic hurricane season.

The U.S. National Hurricane Center said Gustav strengthened back into a Category 1 hurricane as it neared the wealthy Cayman Islands on Friday and could grow into at least a Category 3 storm before reaching western Cuba on Saturday.