MIAMI (Reuters) - Tropical Storm Dean strengthened into the 2007 Atlantic storm season's first hurricane on Thursday as it careened toward the Caribbean and looked set to become "extremely dangerous," the U.S. National Hurricane Center said.
The hurricane, with top sustained winds near 90 miles per hour (45 kph) at 11 a.m EDT (1500 GMT), was expected to strengthen further in the next few days and could pass to the south of Jamaica on its way toward Mexico's Yucatan Peninsula as a powerful Category 4 storm.
"Dean is likely to become a major hurricane in the eastern Caribbean Sea," the Miami-based hurricane center said. Official forecasts "develop this system into an extremely dangerous Category 4 hurricane by the time it reaches the northwestern Caribbean Sea."
Category 3 to 5 hurricanes on the five-step Saffir-Simpson scale, such as Katrina, Rita and Wilma in the devastating 2005 Atlantic storm season, are generally the most destructive storms.
Dean was expected to pass the French islands of Martinique and Guadeloupe as it entered the Caribbean, the Miami-based hurricane center said.
The storm is mostly likely to pass over Mexico's Yucatan Peninsula in about five days, but the hurricane center said one, less likely, forecast showed it moving more to the northwest into the central Gulf of Mexico.
With a large amount of U.S. oil and gas production centered off the Texas Gulf Coast, energy markets have been on edge since powerful hurricanes, including Ivan, Katrina and Rita, ravaged the region in the 2004 and 2005 hurricane seasons.
Roughly one-third of U.S. domestic oil and gas production comes from the Gulf of Mexico.
Hurricane warnings were posted for the islands of Dominica and St. Lucia and hurricane watches were in effect for Martinique and Guadeloupe. A hurricane watch means hurricane conditions can be expected within 36 hours and a warning means hurricane conditions are possible in 24 hours.
The hurricane center said tropical storm warnings were also issued for Montserrat, Antigua, St. Kitts and Nevis, Barbuda, St. Vincent and St. Maarten.
At 11 a.m. EDT (1500 GMT), Dean's center was about 350 miles east of Barbados and about 455 miles east of Martinique. The hurricane was moving west at about 23 mph (37 kph).
The hurricane center said a U.S. Air Force Reserve "hurricane hunter" aircraft was due to fly into Dean to get a bird's eye view later on Thursday.
Meanwhile, another weather system, Tropical Storm Erin, weakened into a depression as it washed ashore in Texas about 25 miles northeast of Corpus Christi, spooking oil markets. It promised to bring more rain than wind.
The hurricane center lifted a tropical storm warning along the Texas coast.
Erin's top sustained winds had slipped to 35 mph (55 kph), but it could still bring 3 to 6 inches of rain across much of southern and central Texas, which has already been soaked by rain this summer, forecasters said.
Forecasters have predicted that the six-month hurricane season, which officially begins June 1, would be more active than average with up to 16 named storms. An average year historically has between 10 to 11 storms, of which six strengthen into hurricanes.
None of the storms that had formed this year -- Andrea, Barry or Chantal -- posed a serious threat.
Atlantic hurricanes shot into the public consciousness after the devastation of 2004 when four storms in a row crossed Florida and again in 2005, when Katrina swamped New Orleans.
In 2005, Hurricane Rita also slammed into the Texas coast near New Orleans and Wilma became for a while the most powerful hurricane ever recorded.