Aug. 16 (Bloomberg) -- Dean, the Atlantic season's first hurricane, formed east of the Caribbean's Lesser Antilles, while in the Gulf of Mexico, Tropical Storm Erin approached Texas.

Dean was 485 miles (780 kilometers) east of Barbados at 5 a.m. Miami time, and heading west at 24 mph, the U.S. National Hurricane Center said in an advisory on its Web site. The system's sustained winds strengthened to 75 mph from 70 mph earlier today, taking it past the 74 mph threshold for a hurricane. The hurricane season runs from June 1 to Nov. 30.

``Dean is a big concern, primarily right now for the Lesser Antilles,'' Jamie Rhome, a hurricane specialist at the center in Miami said today in a phone interview. ``It could become a major hurricane over the next few days over the central Caribbean.''

The center predicted ``additional'' strengthening over the next day, as Dean heads to the Lesser Antilles, which extend south from the Virgin Islands to Trinidad and Tobago.

Erin was about 55 miles southeast of Corpus Christi, Texas, at 4 a.m. local time, and heading ``erratically'' toward the west-northwest at 12 mph, the center said. Erin's maximum sustained winds were 40 mph and may show ``a little strengthening'' before landfall later today, the center said.

Erin's approach to Texas prompted evacuations from Gulf oil and gas platforms belonging to Royal Dutch Shell Plc and Chevron Corp. Over the Atlantic, Dean may pose a further threat to production as it moves across the Caribbean toward Mexico and the Gulf.

Hurricane Warnings

In Texas, a tropical storm warning was in place from San Luis Pass to Port Mansfield as Erin approached. A warning from Port Mansfield to Brownsville was discontinued. The storm is forecast by the hurricane center to bring up to 10 inches (25 centimeters) of rain and a storm surge of up to 3 feet (1 meter) above normal levels. Isolated tornadoes along the middle Texas coast are also possible, the center said.

``Erin is a serious concern, as it's producing very, very heavy rainfall, with the potential to cause flooding,'' Rhome said, signaling that inundations may be possible in urban areas including Corpus Christi, Houston and Galveston. ``Whenever you have this kind of heavy rainfall over a short period of time, there's the potential for flash flooding.''

In the Caribbean, hurricane warnings were issued today for the islands of Dominica and Saint Lucia, indicating hurricane conditions are possible within a day. A hurricane watch was in place for Martinique, Saba, Guadeloupe and its dependencies, and Saint Eustatius, indicating hurricane conditions are possible within 36 hours. St. Maarten was under a tropical-storm watch.

Category 3 Possible

By Aug. 18, Dean may become a Category 3 storm on the five- step Saffir-Simpson scale, with sustained winds as high as 130 mph, Jack Beven, a hurricane specialist at the hurricane center said yesterday. The storm's forecast five-day track over the past two days shifted southward, with the central prediction now showing Dean advancing toward Jamaica, Mexico and then the Gulf.

As Erin approached, Royal Dutch Shell Plc, Europe's biggest oil company, evacuated 188 people from offshore natural gas sites 75 miles southeast of Corpus Christi, and halted production of 5 million cubic feet a day from the North Padre Island 975 field. Chevron Corp., the second-largest U.S. oil company, evacuated a ``small number'' of workers from platforms and drilling rigs in the Gulf of Mexico, the company said yesterday.

The Gulf of Mexico accounts for about 27 percent of U.S. oil production and 15 percent of gas output, according to U.S. Energy Department figures. Fuel prices rose to a record in 2005 after Hurricane Katrina decimated platforms, pipelines and refineries on the Mississippi and Louisiana coasts.

National Guard

Texas Governor Rick Perry dispatched National Guard troops and vehicles to the south in preparation for the storm.

``We've activated our emergency operations team and issued a reminder to residents to prepare for high winds and heavy rain,'' Ted Nelson, spokesman for Corpus Christi's emergency management branch, said yesterday in an interview. ``We have some rivers that are very high, which is our main concern. We're looking out for flooding and are prepared to react quickly if conditions warrant.''

South Padre Island issued a voluntary evacuation for some parks. If local winds exceed 45 mph, the island's causeway will be shut, forcing visitors and residents to be evacuated, a spokeswoman for the convention and visitor's bureau said.

Rhome at the hurricane center said it isn't unusual for the first two months of the season to be relatively quiet.

``In August and especially into September, the tropics really heat up and that's when we get most of the storms,'' he said. ``That's when the strongest storms occur.''

To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net.

Last Updated: August 16, 2007 06:29 EDT