Storm Ike forms, seen growing into hurricane

MIAMI (Reuters) - Tropical Storm Ike, the ninth of a busy Atlantic hurricane season, formed on Monday midway between Africa and the Caribbean and was expected to grow rapidly into a hurricane that could threaten the United States or the Caribbean.

Ike was churning across the Atlantic on the heels of Hurricane Gustav, which pounded New Orleans on Monday as it came ashore on the U.S. Gulf Coast, and Hurricane Hanna, which strengthened as it neared the southeastern Bahamas islands.

The peak of the six-month Atlantic hurricane season usually occurs around September 10, and an average season spawns 10 tropical storms. Six of those strengthen into hurricanes.

Ike's formation, and the possibility of another tropical depression developing in its wake in the coming days, means the storm activity this year is well above normal, bad news for U.S. oil and natural gas production in the Gulf of Mexico and for the millions living in the Caribbean and on U.S. coasts.

By 5 p.m., Tropical Storm Ike was about 1,400 miles east of the Leeward Islands and moving west at 16 miles per hour (26 kph), the U.S. National Hurricane Center said.

Its top sustained winds were already at 50 mph (85 kph) and it was expected to reach hurricane strength, with winds of at least 74 mph (119 kph), within 36 hours, the hurricane center said.

Computer models used to forecast tropical storm tracks indicated Ike was likely to stick to a westerly path that would bring it just north of the island of Hispaniola, shared by Haiti and the Dominican Republic.

The Miami-based hurricane center said Ike could be a "major" hurricane by then. Major hurricanes are those that rank at Category 3 and higher on the five-step Saffir-Simpson scale of storm intensity and are the most destructive.

Hurricane Katrina was a Category 3 when it came ashore near New Orleans in 2005 and swamped the city, killing 1,500 people on the U.S. Gulf Coast. Hurricane Gustav was also a Category 3 on Monday shortly before landfall but it weakened as it landed.

Long-range track and intensity forecasts are subject to enormous error but some models suggested Ike could eventually dip to the south-southwest, potentially threatening Haiti, Cuba or the Gulf of Mexico where the United States produces 25 percent of its oil and 15 percent of its natural gas.

(Reporting by Michael Christie; Editing by Peter Cooney)