By John Marquis

NASSAU, Sept 1 (Reuters) - A busy Atlantic hurricane season moved into top gear on Monday when Hurricane Hanna developed near the Bahamas just as Gustav's winds and surge lashed New Orleans and the newly formed ninth storm of the year looked set to eventually threaten the United States or Caribbean.

The flurry of storms was the latest evidence that predictions for a busier than normal season were on the mark, and was worrisome news for U.S. oil and natural gas producers in the Gulf of Mexico, millions living in the Caribbean and on U.S. coasts, and farmers fearing flooded fields.

At 5 p.m. EDT (2100 GMT), Hurricane Hanna was packing maximum sustained winds of 80 miles per hour (130 kph) and intensifying near Mayaguana Island in the southeastern Bahamas, the U.S. National Hurricane Center said.

Hanna, which had meandered for days bewildering hurricane forecasters, was expected to churn northwest through the Bahamas before striking the U.S. East Coast between north Florida and the Carolinas.

Mayaguana, the most southeasterly of the Bahama islands, has a sparse population of about 1,000 people. Telephone contact with the island was not possible late on Monday.

The nearby Turks and Caicos Islands were also hit by heavy rain and strong winds as Hanna gathered pace.

"There's been no damage here so far," a resident of Grand Turk said. "But there is strong wind. ... I think the capital, Providenciales, is getting it worse than us."

Hanna was the fourth hurricane of the six-month season.

Atlantic storm seasons start on June 1 and usually peak on Sept. 10 and have an average of 10 tropical storms, six of which strengthen into hurricanes with top sustained winds of at least 74 mph (119 kph).

The nine storms so far mean that this year is already way ahead of normal activity, even though forecasters say it is very unlikely to match record-busting 2005, when 28 storms formed, including Hurricane Katrina, which devastated New Orleans.

In addition to Hanna -- and eventually posing perhaps a bigger menace -- Tropical Storm Ike formed on Monday midway between Africa and the Caribbean and was expected to strengthen rapidly into a hurricane.

IKE IS EXPECTED TO BECOME HURRICANE

Behind Ike, a tropical wave was coming off the coast of West Africa and could develop into a tropical depression, the precursors to tropical storms and hurricanes.

By late afternoon, Ike was about 1,400 miles (2,250 km) east of the Leeward Islands and moving west at 16 mph (26 kph), the hurricane center said.

Its top sustained winds of 50 mph (85 kph) were expected to reach hurricane strength within 36 hours.

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, 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. (Writing by Tom Brown; Editing by Michael Christie and Peter Cooney)

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