Sept. 11 (Bloomberg) -- Hurricane Ike was forecast to intensify as it churns across the Gulf of Mexico, prompting President George W. Bush to declare an emergency for Texas and oil companies to shut platforms and refineries.

``This is going to be a major threat for coastal Texas,'' said Eric Wilhelm, a senior meteorologist for private forecaster AccuWeather.com in State College, Pennsylvania.

Governor Rick Perry readied 1,350 buses to evacuate residents in preparation for Ike's landfall, which may take place early Sept. 13 along the central Texas coast southwest of Galveston Bay. As many as 7,500 Texas National Guard members are on standby for rapid deployment, the governor's office said.

Ike's eye was 620 miles (995 kilometers) east of Brownsville, Texas, and moving west-northwest at 9 miles per hour, the National Hurricane Center said in an advisory at 4 a.m. Houston time today. It had strengthened to a Category 2 hurricane with sustained winds of 100 mph, up from 80 mph yesterday.

The hurricane center said Ike may become a ``major hurricane,'' defined as at least a Category 3 storm, with winds of at least 111 mph, within the next day or two. The storm is forecast to sweep through the center of the Gulf, missing the offshore Louisiana oil and natural gas fields. The Gulf is home to about a quarter of U.S. oil production.

``I cannot rule out Ike becoming a very large and dangerous Category 4 hurricane,'' said Jim Rouiller, a meteorologist with Planalytics Inc. in Wayne, Pennsylvania, referring to the second- strongest storms on the five-step Saffir-Simpson scale, which pack winds from 131 to 155 mph.

New Orleans Warning

The New Orleans area, including Lake Pontchartrain, was under a tropical-storm warning for Ike. That means such conditions, with sustained winds of 39 to 73 mph, are expected within 24 hours. The warning stretches along the coast from Cameron, Louisiana, east to the Mississippi-Alabama border.

New Orleans, which was devastated by Hurricane Katrina in 2005, was spared the worst of Hurricane Gustav when it struck the state last week. Gustav killed 25 people in Louisiana.

A hurricane watch was in place from Cameron, Louisiana, west to Port Mansfield, Texas. The watch means hurricane conditions, with sustained winds of at least 74 mph, are possible within 36 hours.

Officials in Corpus Christi, a city of about 277,000 people, yesterday advised people to evacuate. The city last called for an evacuation in 2005, when Hurricane Rita threatened to strike.

Voluntary Evacuations

Voluntary evacuations are also in effect for Galveston, San Patricio, Aransas and Victoria counties and parts of Jackson County. Officials have ordered mandatory evacuations for Brazoria and parts of Matagorda County, according to Perry's office.

The potential for destruction from Hurricane Ike has caused oil refiners to begin shutting plants near Houston and producers to evacuate platforms in the Gulf.

Along the Texas coast, major U.S. refineries are in the path of the storm. Exxon Mobil Corp.'s Baytown facility, 17 miles east of Houston, is the country's biggest, with a capacity of 586,000 barrels a day. In Texas City, BP Plc has a 475,000 barrel-a-day refinery. Royal Dutch Shell Plc, Total SA and Valero Energy Corp. also have refineries in the vicinity.

Some rigs, refineries and platforms shut down before Hurricane Gustav struck Louisiana last week are staying closed. Gulf operators have evacuated personnel from 63 percent of the production platforms, the Minerals Management Service said yesterday.

The Louisiana Offshore Oil Port, which is the biggest U.S. oil-import terminal and handles 13 percent of imports, said it closed marine operations because of Ike.

Crude oil for October delivery rose as much as $1.37, or 1.3 percent, to $103.95 a barrel, on concern Ike will threaten Gulf oil production. It traded at $102.06 a barrel at 9:19 a.m. London time on the New York Mercantile Exchange.

To contact the reporters on this story: Camilla Hall in London at chall24@bloomberg.net; Brian K. Sullivan in Boston at bsullivan10@bloomberg.net.

Last Updated: September 11, 2008 05:48 EDT